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Cited by 202Alzheimer's disease research and treatmentsCholinesterase and Neurodegenerative DiseasesDementia and Cognitive Impairment Research

Bifunctional Compounds for Controlling Metal-Mediated Aggregation of the Aβ42Peptide

Open access
Sharma, Anuj K., Pavlova, Stephanie T., Kim, Jaekwang, Finkelstein, Darren, Hawco, Nicholas J., Rath, Nigam P., Kim, Jungsu, Mirica, Liviu M.·2012·Journal of the American Chemical Society
DOI 10.1021/ja210588mPMC PMC3368506
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Abstract

Abnormal interactions of Cu and Zn ions with the amyloid β (Aβ) peptide are proposed to play an important role in the pathogenesis of Alzheimer's disease (AD). Disruption of these metal-peptide interactions using chemical agents holds considerable promise as a therapeutic strategy to combat this incurable disease. Reported herein are two bifunctional compounds (BFCs) L1 and L2 that contain both amyloid-binding and metal-chelating molecular motifs. Both L1 and L2 exhibit high stability constants for Cu(2+) and Zn(2+) and thus are good chelators for these metal ions. In addition, L1 and L2 show strong affinity toward Aβ species. Both compounds are efficient inhibitors of the metal-mediated aggregation of the Aβ(42) peptide and promote disaggregation of amyloid fibrils, as observed by ThT fluorescence, native gel electrophoresis/Western blotting, and transmission electron microscopy (TEM). Interestingly, the formation of soluble Aβ(42) oligomers in the presence of metal ions and BFCs leads to an increased cellular toxicity. These results suggest that for the Aβ(42) peptide-in contrast to the Aβ(40) peptide-the previously employed strategy of inhibiting Aβ aggregation and promoting amyloid fibril dissagregation may not be optimal for the development of potential AD therapeutics, due to formation of neurotoxic soluble Aβ(42) oligomers.

AI snapshot

Written from the paper’s full text.

TL;DR

Two bifunctional compounds, L1 and L2, combine Aβ-binding and Cu²⁺/Zn²⁺-chelating motifs and inhibit metal-mediated Aβ42 aggregation while disaggregating preformed fibrils. However, this effect generates soluble Aβ42 oligomers and increases neurotoxicity, especially for L2, suggesting that simply blocking Aβ42 fibrillization may not be therapeutically optimal.

Key findings

  • L1 and L2 bind Aβ fibrils with high affinity: L1 Kd = 135±25 nM; ThT competition Ki = 180±25 nM for L1 and 36±6 nM for L2. With Zn²⁺-Aβ fibrils, Ki values were 275±40 nM (L1) and 270±40 nM (L2).
  • Both compounds chelate Cu²⁺ and Zn²⁺ strongly: pCu at pH 6.6/7.4 was 9.6/10.4 for L1 and 7.0/7.9 for L2; pZn at pH 7.4 was 8.0 for L1 and 7.3 for L2.
  • L1 and L2 inhibited metal-mediated Aβ42 aggregation and disaggregated preformed fibrils by TEM and native gel/Western blotting, but produced soluble Aβ42 oligomers, especially with Cu²⁺ and L2.
  • L1 reduced Cu–Aβ42 H₂O₂ production by >65%, and L2 by >90%. In N2A cells, L2 with Aβ42 and Cu²⁺ lowered viability to 38±2% under inhibition and 34±4% under disaggregation conditions, versus 52±3% and 65±5% for L1.

Methods

  • Synthesized L1 and L2 via Mannich reactions and characterized them and their Cu²⁺/Zn²⁺ complexes by NMR, UV-vis, ESI-MS, magnetic susceptibility, and X-ray crystallography.
  • Determined pKa values and metal stability constants by UV-vis pH titrations with HypSpec/HySS; measured Aβ fibril binding by fluorescence titration, ThT competition, and fluorescence microscopy, using Aβ40 fibrils for binding studies.
  • Assessed Aβ42 aggregation/disaggregation by ThT fluorescence, native gel electrophoresis/Western blotting, and TEM; measured H₂O₂ by HRP/Amplex Red and cytotoxicity in Neuro2A cells by Alamar Blue.

Limitations

  • The paper states that the molecular mechanisms of metal–Aβ interactions, especially for Aβ42, are not completely understood, and that future in vivo studies are needed; it also notes that Aβ42 aggregation pathways involving soluble oligomers and nonfibrillar aggregates require further study.
  • Evident from the text: Aβ fibril binding affinities were measured with Aβ40 fibrils, not Aβ42; ThT fluorescence could not quantify Aβ42 aggregation because L1/L2 compete with ThT and Cu²⁺/Zn²⁺ quench or alter ThT signal.
  • Evident from the text: toxicity and aggregation studies are in vitro/cell-culture only, with no in vivo BBB or efficacy data; compounds showed more pronounced toxicity at 20 μM, and DMSO was required for solubility.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1021/ja210588m

Cites

98 of 98 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

36 of 143 cited sources checked · 12 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Use of non-specific chelators (i.e., CQ) that do not interact selectively with the Aβ-metal species exhibit adverse side effects that will likely limit their long term clinical use.

    “However, use of non-specific chelators (i.e., CQ) that do not interact selectively with the Aβ–metal species exhibit adverse side effects that will likely limit their long term clinical use.3,28,29,31,44,46–48”
    Quote in the paperSubstantial claim2 of 8 sources checked
    • cites [3] Jakob-Roetne R Jacobsen H Angew Chem Int Ed 2009 48 3030 19330877 source
    • cites [28] Zatta P Drago D Bolognin S Sensi SL Trends Pharmacol Sci 2009 30 346 19540003 source
    • cites [29] Gaggelli E Kozlowski H Valensin D Valensin G Chem Rev 2006 106 1995 16771441 source
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [44] Cherny RA Neuron 2001 30 665 11430801 source

      The paper acknowledges a historical association between clioquinol (CQ) and neurological side effects, which led to its withdrawal. It does not conclude that side effects will likely limit long-term clinical use: it says the causal link to SMON was unproven, describes possible prevention with vitamin B12, and reports no adverse effects in a phase-one trial. It also describes CQ as selective for copper and zinc relative to calcium and magnesium, rather than simply as a non-specific chelator. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [46] Cahoon L Nat Med 2009 15 356 19350001 source
    • cites [47] Arbiser JL Kraeft SK Van Leeuwen R Hurwitz SJ Selig M Dickerson GR Flint A Byers HR Chen LB Mol Med 1998 4 665 9848083 PMC2230249 source

      The Introduction and Discussion (page not supplied) link oral clioquinol to subacute myelo-optic neuropathy and say its oral use was discontinued or diminished. The Results show that clioquinol forms chelates with several metals. The paper does not assess selectivity for Aβ–metal species or establish that this lack of selectivity is why long-term clinical use would be limited. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [48] Adlard PA Neuron 2008 59 43 18614028 source
  • Findingown data

    Titrations with various amounts of compounds reveal competitive binding curves that yield Ki values 180±25 nM and 36±6 nM for L1 and L2, respectively.

    “Titrations with various amounts of compounds reveal competitive binding curves that yield Ki values 180±25 nM and 36±6 nM for L1 and L2, respectively (Figure 6b).84,85”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [84] Lockhart A Ye L Judd DB Merritt AT Lowe PN Morgenstern JL Hong GZ Gee AD Brown J J Biol Chem 2005 280 7677 15615711 source

      The Materials and Methods section describes competition assays using varying competitor concentrations to derive Ki values. Table I reports Ki values for the compounds studied, but it does not identify L1 or L2 or report 180±25 nM and 36±6 nM for them. Page numbers were unavailable in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [85] Yona RL Mazeres S Faller P Gras E ChemMedChem 2008 3 63 17926318 source
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.
  • Interpretationcitation

    The pM values compare favorably with Kd values reported for Cu-Aβ (nM-μM) and Zn-Aβ (μM).

    “These pM values represent approximate dissociation constants and compare favorably with the Kd values reported for Cu-Aβ (nM-μM) and Zn-Aβ (μM).26,29,31,57,76,79,80”
    Quote in the paperSubstantial claim1 of 7 sources checked
    • cites [26] Faller P Hureau C Dalton Trans 2009 108 19322475 source
    • cites [29] Gaggelli E Kozlowski H Valensin D Valensin G Chem Rev 2006 106 1995 16771441 source
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [57] Rodriguez-Rodriguez C de Groot NS Rimola A Alvarez-Larena A Lloveras V Vidal-Gancedo J Ventura S Vendrell J Sodupe M Gonzalez-Duarte P J Am Chem Soc 2009 131 1436 19133767 source

      In the discussion following Table 5 (page unavailable), the paper reports nanomolar binding constants for Cu–Aβ and micromolar constants for Zn–Aβ, and uses them to predict that its ligands could sequester those metals. It does not report the claimed micromolar end of the Cu–Aβ range. It also defines its pM values as −log of the free-metal concentration, rather than as approximate dissociation constants. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [76] Storr T Merkel M Song-Zhao GX Scott LE Green DE Bowen ML Thompson KH Patrick BO Schugar HJ Orvig C J Am Chem Soc 2007 129 7453 17511455 source
    • cites [79] Danielsson J Pierattelli R Banci L Gräslund A FEBS Journal 2007 274 46 17222176 source
    • cites [80] Hou L Zagorski MG J Am Chem Soc 2006 128 9260 16848423 source
  • Premisecitation

    Metal-Aβ species have been shown to be neurotoxic.

    “Since metal-Aβ species have been shown to be neurotoxic,25,51,92”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [25] Bush AI Neurobiol Aging 2002 23 1031 12470799 source
    • cites [51] Hindo SS Mancino AM Braymer JJ Liu YH Vivekanandan S Ramamoorthy A Lim MH J Am Chem Soc 2009 131 16663 19877631 PMC3417132 source
    • cites [92] Huang XD J Biol Chem 1999 274 37111 10601271 source
  • Premisecitation

    Most previous studies have employed the Aβ40 peptide that follows a more direct aggregation pathway to form homogenous, well-defined fibrillar structures.

    “However, most of these previous studies have employed the Aβ40 peptide that follows a more direct aggregation pathway to form homogenous, well-defined fibrillar structures.83,84”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [83] Klunk WE Wang YM Huang GF Debnath ML Holt DP Mathis CA Life Sci 2001 69 1471 11554609 source
    • cites [84] Lockhart A Ye L Judd DB Merritt AT Lowe PN Morgenstern JL Hong GZ Gee AD Brown J J Biol Chem 2005 280 7677 15615711 source

      The introductory passage reports that multiple laboratories studied ligands on Aβ(1–40) fibrils, and Materials and Methods describes this paper’s use of Aβ(1–40). The paper does not say that most previous studies used Aβ40, or that it follows a more direct aggregation pathway and forms homogeneous, well-defined fibrils. Page numbers are unavailable in our copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • May combine two claims. 60
  • Classified as probably not a substantial claim. 7

  • May combine two claims.

    Premisecitation

    Soluble Aβ oligomers are possibly more neurotoxic than amyloid plaques and are likely responsible for synaptic dysfunction and memory loss in AD patients and AD animal models.

    “However, recent in vivo studies have shown that the soluble Aβ oligomers are possibly more neurotoxic than amyloid plaques,14–17 and are likely responsible for synaptic dysfunction and memory loss in AD patients and AD animal models.18–21”
    Quote in the paperSubstantial claim4 of 8 sources checked
    • cites [14] Lambert MP Barlow AK Chromy BA Edwards C Freed R Liosatos M Morgan TE Rozovsky I Trommer B Viola KL Wals P Zhang C Finch CE Krafft GA Klein WL Proc Nat Acad Sci USA 1998 95 6448 9600986 PMC27787 source
    • cites [15] Hsia AY Masliah E McConlogue L Yu GQ Tatsuno G Hu K Kholodenko D Malenka RC Nicoll RA Mucke L Proc Natl Acad Sci 1999 96 3228 10077666 PMC15924 source

      The Abstract reports synaptic deficits in APP-transgenic mice before plaques form, supporting plaque-independent dysfunction. Results and Discussion names diffusible Aβ oligomers as one possible cause, but also names intraneuronal Aβ; it does not establish that oligomers are more neurotoxic than plaques or responsible for memory loss in mice or patients. Its proposed link to cognitive impairment in patients is explicitly speculative. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [16] Lesne S Koh MT Kotilinek L Kayed R Glabe CG Yang A Gallagher M Ashe KH Nature 2006 440 352 16541076 source
    • cites [17] Ahmed M Davis J Aucoin D Sato T Ahuja S Aimoto S Elliott JI Van Nostrand WE Smith SO Nat Struct Mol Biol 2011 17 561 20383142 PMC2922021 source
    • cites [18] Gong YS Chang L Viola KL Lacor PN Lambert MP Finch CE Krafft GA Klein WL Proc Nat Acad Sci USA 2003 100 10417 12925731 PMC193576 source
    • cites [19] Walsh DM Selkoe DJ J Neurochem 2007 101 1172 17286590 source
    • cites [20] Haass C Selkoe DJ Nat Rev Mol Cell Biol 2007 8 101 17245412 source
    • cites [21] Borutaite V Morkuniene R Valincius G BioMol Concepts 2011 2 211 25962030 source

  • May combine two claims.

    Premisecitation

    Aβ40 is present in larger amounts in the brain, yet Aβ42 is more neurotoxic and has a higher tendency to aggregate.

    “Aβ40 is present in larger amounts in the brain, yet Aβ42 is more neurotoxic and has a higher tendency to aggregate.8–11”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [8] McGowan E Neuron 2005 47 191 16039562 PMC1373682 source
    • cites [9] Kim J Onstead L Randle S Price R Smithson L Zwizinski C Dickson DW Golde T McGowan E J Neurosci 2007 27 627 17234594 PMC6672801 source

      The Introduction says Aβ40 is the predominant form produced, but it also says Aβ42 is the predominant form that accumulates in the AD brain; thus, the claim about larger amounts in the brain needs qualification. The Introduction and aggregation-assay section support Aβ42’s greater tendency to aggregate. The copy does not establish that Aβ42 is more neurotoxic than Aβ40. Passage-level page numbers were not provided. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [10] Kuperstein I EMBO J 2010 29 3408 20818335 PMC2957213 source

      The Introduction says Aβ40 is the major species in serum, cerebrospinal fluid, and cell-culture supernatants, with Aβ42 detected at about tenfold lower levels; it does not establish their relative amounts in brain tissue. The Introduction also describes faster Aβ42 aggregation, and the Abstract and results support its greater toxic potential, while emphasizing that toxicity depends on the Aβ42:Aβ40 ratio. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [11] Pauwels K Williams TL Morris KL Jonckheere W Vandersteen A Kelly G Schymkowitz J Rousseau F Pastore A Serpell LC Broersen K J Biol Chem 2012 287 5650 22157754 PMC3285338 source

  • May combine two claims.

    Findingcitation

    L1 and L2 were designed following the linkage approach and contain metal-binding N-(2-pyridylmethyl)amine groups and amyloid-interacting 2-phenylbenzothiazole and o-vanillin molecular fragments.

    “Reported herein are two new BFCs, L1 and L2, that were designed following the linkage approach and contain metal-binding N-(2-pyridylmethyl)amine groups and amyloid-interacting 2-phenylbenzothiazole and o-vanillin molecular fragments (Scheme 2).59”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [59] Necula M Kayed R Milton S Glabe CG J Biol Chem 2007 282 10311 17284452 source

      The Experimental Procedures list o-vanillin among compounds tested for effects on amyloid-β aggregation, and the Discussion identifies it as inhibiting both oligomerization and fibrillization (page unavailable). The copy does not describe L1 or L2, the linkage approach, or the claimed composition of those new compounds; it also does not establish the specific role of a 2-phenylbenzothiazole fragment. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    The non-specific chelator clioquinol (CQ) showed decreased Aβ aggregate formation that resulted in improved cognition in clinical trials.

    “For example, the non-specific chelator clioquinol (CQ) showed decreased Aβ aggregate formation that resulted in improved cognition in clinical trials.24,25,43–45”
    Quote in the paperSubstantial claim1 of 5 sources checked
    • cites [24] Barnham KJ Masters CL Bush AI Nat Rev Drug Disc 2004 3 205 15031734 source
    • cites [25] Bush AI Neurobiol Aging 2002 23 1031 12470799 source
    • cites [43] Bush AI Trends Neurosci 2003 26 207 12689772 source
    • cites [44] Cherny RA Neuron 2001 30 665 11430801 source

      The Abstract reports reduced brain Aβ deposition after clioquinol treatment in transgenic mice, not in a clinical trial. The Discussion says cognitive gains were only predicted and that further testing was needed to determine whether the observed improvement in general behavior reflected a cognitive effect. (LLM, conf=0.94)

      Experimental — accuracy not yet measured
    • cites [45] Barnham KJ Bush AI Curr Opin Chem Biol 2008 12 222 18342639 source

  • May combine two claims.

    Premisecitation

    Metal chelators can reduce metal-mediated Aβ aggregation, ROS formation, and neurotoxicity in vitro.

    “Given the recognized interactions of Aβ with transition metal ions, several studies have shown that metal chelators can reduce the metal-mediated Aβ aggregation, ROS formation, and neurotoxicity in vitro.43–45”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [43] Bush AI Trends Neurosci 2003 26 207 12689772 source
    • cites [44] Cherny RA Neuron 2001 30 665 11430801 source

      The passage on chelator selection (indexed as Abstract; page unavailable) says common chelators reverse metal-induced Aβ aggregation and H2O2 production, supporting the aggregation and ROS parts of the claim. The Experimental Procedures describe an in-vitro aggregation assay, but the passages found do not report that chelators reduce Aβ-mediated neurotoxicity in vitro. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [45] Barnham KJ Bush AI Curr Opin Chem Biol 2008 12 222 18342639 source

  • May combine two claims.

    Premisecitation

    Two approaches have been pursued in BFC design: direct incorporation of metal-binding atom donors into the structural framework of an Aβ-interacting compound, and linking the metal-chelating and Aβ-binding molecular fragments.

    “In this context, two approaches have been pursued in BFC design. 31,49–58 One strategy is based on the direct incorporation of metal-binding atom donors into the structural framework of an Aβ-interacting compoud (Scheme 1, approach A), and the other involves linking the metal-chelating and Aβ-binding molecular fragments (Scheme 1, approach B).”
    Quote in the paperNot a substantial claim3 of 10 sources checked
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [49] Scott LE Telpoukhovskaia M Rodriguez-Rodriguez C Merkel M Bowen ML Page BDG Green DE Storr T Thomas F Allen DD Lockman PR Patrick BO Adam MJ Orvig C Chem Sci 2011 2 642

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [50] Perez LR Franz KJ Dalton Trans 2011 39 2177 20162187 PMC2860397 source
    • cites [51] Hindo SS Mancino AM Braymer JJ Liu YH Vivekanandan S Ramamoorthy A Lim MH J Am Chem Soc 2009 131 16663 19877631 PMC3417132 source

      In the main text (page unavailable), the paper describes incorporating nitrogen or oxygen donor atoms directly into an Aβ-recognizing imaging agent, supporting the first design approach. It does not describe the second approach of linking separate metal-chelating and Aβ-binding fragments. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [52] Choi JS Braymer JJ Nanga RPR Ramamoorthy A Lim MH Proc Natl Acad Sci 2010 107 21990 21131570 PMC3009803 source
    • cites [53] Zhang Y Chen LY Yin WX Yin J Zhang SB Liu CL Dalton Trans 2011 40 4830 21437337 source
    • cites [54] Dedeoglu A Cormier K Payton S Tseitlin KA Kremsky JN Lai L Li XH Moir RD Tanzi RE Bush AI Kowall NW Rogers JT Huang XD Exp Gerontol 2004 39 1641 15582280 source
    • cites [55] Hureau C Sasaki I Gras E Faller P ChemBioChem 2010 11 950 20401891 source
    • cites [56] Choi J-S Braymer JJ Park SK Mustafa S Chae J Lim MH Metallomics 2011 3 284 21210061 source
    • cites [57] Rodriguez-Rodriguez C de Groot NS Rimola A Alvarez-Larena A Lloveras V Vidal-Gancedo J Ventura S Vendrell J Sodupe M Gonzalez-Duarte P J Am Chem Soc 2009 131 1436 19133767 source

      The Introduction (page not provided) describes adding chelating properties to compounds with amyloid affinity, and the Summary says the resulting molecular framework integrates amyloid binding and metal chelation. This supports the direct-incorporation approach, but the paper does not describe the claimed alternative of linking separate metal-chelating and Aβ-binding fragments. (LLM, conf=0.83)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingcitation

    The presence of Zn2+ causes a significant enhancement of the emission intensity in 2 and 4, similar to reported Zn fluorescent sensors containing N-(2-pyridylmethyl) arms.

    “However, the presence of Zn2+ causes a significant enhancement of the emission intensity in 2 and 4, (Figures S17 and S18), similar to the reported Zn fluorescent sensors containing N-(2-pyridylmethyl) arms.73,74”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [73] Nolan EM Lippard SJ Acc Chem Res 2008 42 193 18989940 PMC2646817 source
    • cites [74] Tomat E Lippard SJ Curr Opin Chem Biol 2010 14 225 20097117 PMC2847655 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Aβ fibrils obtained from the Aβ40 peptide form more homogenous fibrillar structures without any non-fibrillar aggregates.

    “These studies were performed with Aβ fibrils obtained from the Aβ40 peptide, which forms more homogenous fibrillar structures without any non-fibrillar aggregates (Figure S21a).83,84”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [83] Klunk WE Wang YM Huang GF Debnath ML Holt DP Mathis CA Life Sci 2001 69 1471 11554609 source
    • cites [84] Lockhart A Ye L Judd DB Merritt AT Lowe PN Morgenstern JL Hong GZ Gee AD Brown J J Biol Chem 2005 280 7677 15615711 source

      Materials and Methods (page unavailable) confirms that the authors prepared fibrils from Aβ(1–40) peptide. The results describe two populations of high-molecular-mass species in that preparation; they do not establish that Aβ40 forms more homogeneous fibrils than another peptide or that non-fibrillar aggregates are absent. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Interpretationown data

    The lack of change in L2 emission in presence of Aβ fibrils is likely not due to lack of L2 binding to Aβ fibrils, but merely a failure of Aβ to impact the fluorescence of L2.

    “This behavior is likely not due to the lack of L2 binding to Aβ fibrils, but is merely a failure of Aβ to impact the fluorescence of L2.86”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [86] Reinke AA Seh HY Gestwicki JE Bioorg Med Chem Lett 2009 19 4952 19640715 PMC2730169 source

      In Results, under “Fluorescence screen for Aβ conformation-specific small molecules” (page unavailable), the paper says unchanged fluorescence should not be interpreted as failure to bind. It does not study L2 or establish that L2 binds Aβ fibrils, so it supports the citing sentence’s interpretive caution but not its L2-specific explanation. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingcitation

    CQ shows <30% cell survival at concentrations >2 μM, while EDTA shows 90-95% cell survival up to 20 μM concentration.

    “By comparison, the clinically tested compound CQ shows <30% cell survival at concentrations >2 μM, while EDTA shows 90–95% cell survival up to 20 μM concentration (Figure S26).51,52”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [51] Hindo SS Mancino AM Braymer JJ Liu YH Vivekanandan S Ramamoorthy A Lim MH J Am Chem Soc 2009 131 16663 19877631 PMC3417132 source

      In the paper’s cell-study discussion (page unavailable), CQ is described as more toxic than compounds 1 and 2, supporting only the qualitative CQ comparison. Our copy gives neither <30% survival above 2 μM for CQ nor 90–95% survival up to 20 μM for EDTA; its approximately 90% survival figure refers to compound 2. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [52] Choi JS Braymer JJ Nanga RPR Ramamoorthy A Lim MH Proc Natl Acad Sci 2010 107 21990 21131570 PMC3009803 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Aβ42 peptide was shown to form neurotoxic soluble Aβ oligomers.

    “which was also shown to form neurotoxic soluble Aβ oligomers.18–20”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [18] Gong YS Chang L Viola KL Lacor PN Lambert MP Finch CE Krafft GA Klein WL Proc Nat Acad Sci USA 2003 100 10417 12925731 PMC193576 source
    • cites [19] Walsh DM Selkoe DJ J Neurochem 2007 101 1172 17286590 source
    • cites [20] Haass C Selkoe DJ Nat Rev Mol Cell Biol 2007 8 101 17245412 source

  • May combine two claims.

    Interpretationown data

    Metal ions are able to stabilize the soluble Aβ42 oligomers and thus partially inhibit the Aβ42 aggregation.

    “These results suggest that metal ions are able to stabilize the soluble Aβ42 oligomers and thus partially inhibit the Aβ42 aggregation.89”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [89] Tew DJ Bottomley SP Smith DP Ciccotosto GD Babon J Hinds MG Masters CL Cappai R Barnham KJ Biophys J 2008 94 2752 18065467 PMC2267149 source

      The Conclusion (page unavailable) says Cu2+ promotes the formation and stability of soluble Aβ oligomers, supporting the stabilization part for copper. It does not report that metal ions generally partially inhibit Aβ42 aggregation; the Discussion instead describes increased aggregation under the study conditions. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    Soluble Aβ42 oligomers show decreased cell survival of 44±8%, supporting the increased neurotoxicity of Aβ42 oligomers versus Aβ42 fibrils.

    “This is confirmed by the decreased cell survival of 44±8% in presence of soluble Aβ42 oligomers (Figure 11, lane 2), supporting the increased neurotoxicity of Aβ42 oligomers versus Aβ42 fibrils.16,19”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [16] Lesne S Koh MT Kotilinek L Kayed R Glabe CG Yang A Gallagher M Ashe KH Nature 2006 440 352 16541076 source
    • cites [19] Walsh DM Selkoe DJ J Neurochem 2007 101 1172 17286590 source

  • May combine two claims.

    Findingcitation

    The 48 h total incubation leads to mature Aβ42 fibrils, as observed by TEM, while the Western blot shows the presence of higher order Aβ42 oligomers, likely due to an assembly-disassembly equilibrium that is established for mature Aβ fibrils.

    “The 48 h total incubation leads to mature Aβ42 fibrils, as observed by TEM (Figure 10, panel a) while the Western blot shows the presence of higher order Aβ42 oligomers (Figure 10, lane a), likely due to an assembly-disassembly equilibrium that is established for mature Aβ fibrils.89–91”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [89] Tew DJ Bottomley SP Smith DP Ciccotosto GD Babon J Hinds MG Masters CL Cappai R Barnham KJ Biophys J 2008 94 2752 18065467 PMC2267149 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [90] Dahlgren KN Manelli AM Stine WB Baker LK Krafft GA LaDu MJ J Biol Chem 2002 277 32046 12058030 source
    • cites [91] Stine WB Dahlgren KN Krafft GA LaDu MJ J Biol Chem 2003 278 11612 12499373 source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The Alamar Blue cell viability assay has been shown to give more reproducible results than the MTT assay.

    “using an Alamar Blue cell viability assay, which has been shown to give more reproducible results than the MTT assay.93,94”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [93] Wogulis M Wright S Cunningham D Chilcote T Powell K Rydel RE J Neurosci 2005 25 1071 15689542 PMC6725948 source

      In the section on MTT as an indicator of Aβ-mediated neuronal cell death (page unavailable), alamarBlue and other assays did not show the apparent loss of viability indicated by MTT. The paper therefore supports a difference in reliability for this specific application, but does not show that alamarBlue gives more reproducible results than MTT. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [94] Stine BW Jungbauer L Yu C LaDu MJ Met Mol Biol 2010 670 13 PMC3752843 20967580 source

      The Methods section (3.8.1, page not available) describes a CellTiter-Glo ATP-based viability assay, not an Alamar Blue assay. Searches for Alamar Blue, MTT, and assay reproducibility found no comparison between them in our copy. (LLM, conf=0.76)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    BFCs were able to inhibit metal-mediated Aβ aggregation and disassemble pre-formed Aβ aggregates.

    “These BFCs were also able to inhibit the metal-mediated Aβ aggregation and disassemble pre-formed Aβ aggregates.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The bifunctional character of L1 and L2 was confirmed by metal-chelating and Aβ-binding studies that reveal tight binding to Cu and Zn ions and high affinity for Aβ fibrils.

    “The bifunctional character of the two compounds was confirmed by metal-chelating and Aβ-binding studies that reveal a tight binding to Cu and Zn ions and high affinity for the Aβ fibrils.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Performing the same titration of Aβ fibrils with ThT yields a Kd of 1.17±0.14 μM, a value similar to those reported previously.

    “By comparison, performing the same titration of Aβ fibrils with ThT yields a Kd of 1.17±0.14 μM (Figure S21b), a value similar to those reported previously.83,85”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [83] Klunk WE Wang YM Huang GF Debnath ML Holt DP Mathis CA Life Sci 2001 69 1471 11554609 source
    • cites [85] Yona RL Mazeres S Faller P Gras E ChemMedChem 2008 3 63 17926318 source

  • May combine two claims.

    Findingown data

    pCu values for L1 are 9.6 and 10.4 at pH 6.6 and 7.4, respectively; for L2 the values are 7.0 and 7.9, respectively.

    “In our case, the pCu values for L1 are 9.6 and 10.4 at pH 6.6 and 7.4, respectively, while for L2 the values are 7.0 and 7.9, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Ki value for L1 in presence of Zn2+ is less than two-fold larger than that in absence of Zn2+, while a seven-fold difference is observed for L2.

    “While the Ki value for L1 in presence of Zn2+ is less than two-fold larger than that in absence of Zn2+, a seven-fold difference is observed for L2.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • May combine two claims.

    Findingown data

    The Zn-L2 complex 4 is isolated as a 1:1 complex in the solid state, yet Job's plot analysis suggests formation of a mixture of 1:1 and 1:2 complexes in solution.

    “In addition, the Zn-L2 complex 4 is isolated as a 1:1 complex in the solid state, yet the Job’s plot analysis suggests formation of a mixture of 1:1 and 1:2 complexes in solution.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Both L1 and L2 have a slightly higher affinity for Cu2+ than for Zn2+.

    “In addition, both L1 and L2 have a slightly higher affinity for Cu2+ than for Zn2+.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The solid state structure for 3 shows a 1:2 Cu:ligand complex, while Job's plot analysis and UV-vis titrations suggest the formation of a 1:1 complex in solution.

    “Notably, while the solid state structure for 3 shows a 1:2 Cu:ligand complex, the Job’s plot analysis and UV-vis titrations suggest the formation of a 1:1 complex in solution.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In complex 4, the Zn2+ ions are bridged by the phenolate O's of the L2 ligand, and an additional μ3-oxo group bridges all three Zn centers.

    “Similar to 2, the Zn2+ ions in 4 are bridged by the phenolate O’s of the L2 ligand, and an additional μ3-oxo group bridges all three Zn centers.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In complexes 1 and 2, each metal ion is bound to the two pyridine N's and the amine N atom of one ligand molecule, while the two phenolate O's bridge the two metal centers.

    “Each metal ion is bound to the two pyridine N’s and the amine N atom of one ligand molecule, while the two phenolate O’s bridge the two metal centers (Figures 5a and S19).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    L2 forms a 2:1 complex with Cu2+ in which the metal center adopts a pseudo-octahedral coordination environment.

    “Interestingly, while L2 forms a 2:1 complex with Cu2+ in which the metal center adopts a pseudo–octahedral coordination environment (Figure 5b)”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    L2 exhibits an increased fluorescence intensity compared to L1, yet its emission does not change in presence of Aβ fibrils.

    “The L2 compound exhibits an increased fluorescence intensity compared to L1, yet its emission does not change in presence of Aβ fibrils (Figure S22b).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Both Cu2+ centers in 1 exhibit a distorted square-pyramidal coordination geometry with trigonality index parameters τ of 0.32 and 0.44.

    “Both Cu2+ centers in 1 exhibit a distorted square–pyramidal coordination geometry with trigonality index parameters82 τ of 0.32 and 0.44, respectively.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Cu complexes 1 and 3 show characteristic d-d transition bands (832 nm for 1 and 660 nm for 3) as well as phenolate-to-Cu charge transfer bands (425 nm for 1 and 520 nm for 3).

    “Cu complexes 1 and 3 show characteristic d–d transition bands (i.e., 832 nm for 1 and 660 nm for 3) as well as phenolate-to-Cu charge transfer bands (425 nm for 1 and 520 nm for 3, Figures S10 and S12).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The concentration of free Cu2+ with L1 is negligible above pH 4.5, while free Zn2+ is present up to pH 7.0.

    “In addition, Figures 3 and 4 show that the concentration of free Cu2+ with L1 is negligible above pH 4.5, while free Zn2+ is present up to pH 7.0.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Incubation of ThT, L1, and L2 with Aβ42 fibrils for 10 min followed by fluorescence microscopy imaging shows that areas rich in Aβ42 aggregates exhibit a bright blue fluorescence, with emission intensity for L1 and L2 similar to that observed for ThT.

    “Incubation of ThT, L1, and L2 with Aβ42 fibrils for 10 min followed by fluorescence microscopy imaging shows that the areas rich in Aβ42 aggregates exhibit a bright blue fluorescence, the emission intensity for L1 and L2 being similar to that observed for ThT (Figure 7).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    L1 and L2 exhibit 72±4% and 77±2% cell survival, respectively, when used in 2 μM concentrations.

    “Secondly, we tested the neurotoxicity of our compounds, which shows that L1 and L2 exhibit 72±4% and 77±2% cell survival, respectively, when used in 2 μM concentrations (Figure 11, lanes 4 and 8).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Aggregation of Aβ42 for 24 h at 37 °C leads to well-defined Aβ fibrils, as confirmed by TEM, and native gel/Western blot analysis shows a small amount of soluble Aβ oligomers.

    “The aggregation of Aβ42 for 24 h at 37 °C leads to well-defined Aβ fibrils, as confirmed by TEM (Figure 8, panel a), and native gel/Western blot analysis shows a small amount of soluble Aβ oligomers (Figure 9, lane a).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    While the presence of Cu2+ or Zn2+ during the initial 24 h incubation at 37 °C leads to formation of smaller aggregates and soluble oligomers, the additional 24 h incubation leads to mature Aβ aggregates along with a decrease in the amount of soluble Aβ oligomers.

    “While the presence of Cu2+ or Zn2+ during the initial 24 h incubation at 37 °C leads to formation of smaller aggregates and soluble oligomers (Figure 8, panels b and c; Figure 9, lanes b and c), the additional 24 h incubation leads to mature Aβ aggregates (Figure 10, panels b and c) along with a decrease in the amount of soluble Aβ oligomers (Figure 10, lanes b and c).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Native gel/Western blot analysis shows formation of a wide range of soluble Aβ42 oligomers - including higher-mass aggregates, in presence of Cu and L1 or L2, with L2 having a more pronounced effect.

    “Native gel/Western blot analysis shows formation of a wide range of soluble Aβ42 oligomers – including higher-mass aggregates, in presence of Cu and L1 or L2 (Figure 9, lanes e and h), L2 having a more pronounced effect.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Aβ aggregation in presence of Cu shows formation of almost no Aβ fibrils by TEM, while Western blotting shows the formation of soluble Aβ42 oligomers with masses in the 10-110 kDa range.

    “However, Aβ aggregation in presence of Cu shows formation of almost no Aβ fibrils by TEM (Figure 8, panel b), while Western blotting shows the formation of soluble Aβ42 oligomers with masses in the 10–110 kDa range (Figure 9, lane b).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Aβ42 fibrils show limited neurotoxicity (86±8% cell viability), while the presence of both Aβ42 fibrils and Cu2+ shows no cell death.

    “Firstly, we observe a limited neurotoxicity of Aβ42 fibrils (86±8% cell viability, Figure 11, lane 1), while the presence of both Aβ42 fibrils and Cu2+ shows no cell death (Figure 11, lane 3)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Other metal chelators such as clioquinol (CQ) and phenanthroline (phen) have almost no effect on H2O2 production, while EDTA shows a reduction in H2O2 formation similar to that of L2.

    “By comparison, other metal chelators such as clioquinol (CQ) and phenanthroline (phen) have almost no effect on H2O2 production, while the strong chelator ethylenediaminetetraacetic acid (EDTA) shows a reduction in H2O2 formation similar to that of L2.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The metal-binding compound L* exhibits a dramatic reduction of H2O2 production by Cu2+ and Cu2+-Aβ42 species, suggesting an intrinsic anti-oxidant property of this metal-binding molecular fragment.

    “Interestingly, the metal-binding compound N-methyl-N,N-bis(2-pyridylmethyl)amine (L*), which resembles the metal-chelating fragments in L1 and L2, exhibits also a dramatic reduction of H2O2 production by Cu2+ and Cu2+–Aβ42 species (Figure S25), suggesting an intrinsic anti-oxidant property of this metal-binding molecular fragment.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Cu2+-Aβ42 aggregates are efficiently disassembled by L1 and especially by L2 to form a wide range of soluble Aβ42 oligomers of various sizes, which are expected to lead to increased neurotoxicity.

    “The Cu2+-Aβ42 aggregates are efficiently disassembled by L1 and especially by L2 to form a wide range of soluble Aβ42 oligomers of various sizes (Figure 10, lanes e and h), which are expected to lead to increased neurotoxicity (vide infra).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Addition of CQ to Aβ42 fibrils in presence of Cu2+ leads to marked cell toxicity, likely due to the ability of CQ to disaggregate Aβ fibrils.

    “As expected, addition of CQ to Aβ42 fibrils in presence of Cu2+ leads to marked cell toxicity (Figure 11, lane 12), likely due to the ability of CQ to disaggregate Aβ fibrils.96”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [96] Mancino AM Hindo SS Kochi A Lim MH Inorg Chem 2009 48 9596 19817493 source

  • May combine two claims.

    Findingown data

    Both L1 and L2 are good inhibitors of aggregation, with noticeably fewer Aβ42 fibrils observed in presence vs. absence of these compounds.

    “Interestingly, both L1 and L2 were observed to be good inhibitors of aggregation, noticeably fewer Aβ42 fibrils being observed in presence vs. the absence of these compounds (Figure 8, panels d and g).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Aggregation of Aβ42 in presence of Zn2+ leads to a small amount of amorphous aggregates, and native gel/Western blot analysis shows formation of soluble Aβ42 oligomers of various sizes.

    “By comparison, the aggregation of Aβ42 in presence of Zn2+ leads to a small amount of amorphous aggregates (Figure 8, panel c), and native gel/Western blot analysis shows formation of soluble Aβ42 oligomers of various sizes (Figure 9, lane c).88”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [88] Garai K Sahoo B Kaushalya SK Desai R Maiti S Biochemistry 2007 46 10655 17718543 source

  • May combine two claims.

    Findingown data

    Addition of L1 or L2 to Aβ42 fibrils leads to a dissociation of the large Aβ42 aggregates, as observed by TEM, although small Aβ42 fibrils are still present.

    “Addition of L1 or L2 to Aβ42 fibrils leads to a dissociation of the large Aβ42 aggregates, as observed by TEM (Figure 10, panels d and g), although small Aβ42 fibrils are still present.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The presence of monomeric Aβ42 (20 μM), L1 (2 μM), and Cu2+ (20 μM) leads to 52±3% cell viability, while a 65±5% cell survival was observed in presence of Aβ42 fibrils.

    “The presence of monomeric Aβ42 (20 μM), L1 (2 μM), and Cu2+ (20 μM) leads to 52±3% cell viability, while a 65±5% cell survival was observed in presence of Aβ42 fibrils (Figure 11, lanes 6 and 7, respectively).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    According to the amyloid cascade hypothesis, increased production and accumulation of the Aβ peptide promote the formation of Aβ oligomers, protofibrils, and ultimately amyloid fibrils that lead to neurodegeneration.

    “According to the amyloid cascade hypothesis, the increased production and accumulation of the Aβ peptide promote the formation of Aβ oligomers, protofibrils, and ultimately amyloid fibrils that lead to neurodegeneration.12,13”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [12] Hardy JA Higgins GA Science 1992 256 184 1566067 source
    • cites [13] Hardy J Selkoe DJ Science 2002 297 353 12130773 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    These metal ions have been shown to promote Aβ40 aggregation.

    “Thus, these metal ions have been shown to promote Aβ40 aggregation,23–27,29–32”
    Quote in the paperNot a substantial claim0 of 9 sources checked
    • cites [23] Lovell MA Robertson JD Teesdale WJ Campbell JL Markesbery WR J Neuro Sci 1998 158 47 9667777 source
    • cites [24] Barnham KJ Masters CL Bush AI Nat Rev Drug Disc 2004 3 205 15031734 source
    • cites [25] Bush AI Neurobiol Aging 2002 23 1031 12470799 source
    • cites [26] Faller P Hureau C Dalton Trans 2009 108 19322475 source
    • cites [27] Faller P ChemBioChem 2009 10 2837 19877000 source
    • cites [29] Gaggelli E Kozlowski H Valensin D Valensin G Chem Rev 2006 106 1995 16771441 source
    • cites [30] Rauk A Chem Soc Rev 2009 38 2698 19690748 source
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [32] Karr JW Kaupp LJ Szalai VA J Am Chem Soc 2004 126 13534 15479110 source

  • May combine two claims.

    Premisecitation

    The role of metal ions in Aβ42 aggregation remains unclear and only few reports are available in the literature.

    “However, the role of metal ions in Aβ42 aggregation still remains unclear and only few reports are available in the literature.37–41”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [37] Atwood CS Moir RD Huang XD Scarpa RC Bacarra NME Romano DM Hartshorn MK Tanzi RE Bush AI J Biol Chem 1998 273 12817 9582309 source
    • cites [38] Atwood CS Scarpa RC Huang XD Moir RD Jones WD Fairlie DP Tanzi RE Bush AI J Neurochem 2000 75 1219 10936205 source
    • cites [39] Yoshiike Y Tanemura K Murayama O Akagi T Murayama M Sato S Sun XY Tanaka N Takashima A J Biol Chem 2001 276 32293 11423547 source
    • cites [40] Zou J Kajita K Sugimoto N Angew Chem Int Ed 2001 40 2274 11433492 source
    • cites [41] Tõugu V Karafin A Zovo K Chung RS Howells C West AK Palumaa P J Neurochem 2009 110 1784 19619132 source

  • May combine two claims.

    Premisecitation

    These metal ions lead to formation of reactive oxygen species (ROS) and oxidative stress.

    “as well as lead to formation of reactive oxygen species (ROS) and oxidative stress.3,26–31,33–36”
    Quote in the paperNot a substantial claim0 of 10 sources checked
    • cites [3] Jakob-Roetne R Jacobsen H Angew Chem Int Ed 2009 48 3030 19330877 source
    • cites [26] Faller P Hureau C Dalton Trans 2009 108 19322475 source
    • cites [27] Faller P ChemBioChem 2009 10 2837 19877000 source
    • cites [28] Zatta P Drago D Bolognin S Sensi SL Trends Pharmacol Sci 2009 30 346 19540003 source
    • cites [29] Gaggelli E Kozlowski H Valensin D Valensin G Chem Rev 2006 106 1995 16771441 source
    • cites [30] Rauk A Chem Soc Rev 2009 38 2698 19690748 source
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [33] Cappai R Barnham K Neurochem Res 2008 33 526 17762917 source
    • cites [34] Zhu X Su B Wang X Smith M Perry G Cell Mol Life Sci 2007 64 2202 17605000 PMC11136009 source
    • cites [35] Hureau C Faller P Biochimie 2009 91 1212 19332103 source

  • May combine two claims.

    Interpretationcitation

    The two lower pKa values of L1 are assigned to deprotonation of the two pyridinium groups, the third to the ammonium group, and the highest to phenol deprotonation.

    “Based on previously reported acidity constants for phenols, amines,76 and pyridines,52 we assigned the two lower pKa values to the deprotonation of the two pyridinium groups, and the third pKa value to the ammonium group. The highest pKa value is likely due to phenol deprotonation in L1.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [76] Storr T Merkel M Song-Zhao GX Scott LE Green DE Bowen ML Thompson KH Patrick BO Schugar HJ Orvig C J Am Chem Soc 2007 129 7453 17511455 source
    • cites [52] Choi JS Braymer JJ Nanga RPR Ramamoorthy A Lim MH Proc Natl Acad Sci 2010 107 21990 21131570 PMC3009803 source

  • May combine two claims.

    Interpretationown data

    L1 and L2 satisfy Lipinski's rules for BBB penetration and calculated logBB values, suggesting they should be capable of crossing the BBB.

    “Considering the restrictive Lipinski’s rules for BBB penetration (MW ≤ 450, clogP ≤5, hydrogen bond donors ≤ 5, hydrogen bond acceptors ≤ 10, polar surface area ≤ 90 Å2) and the calculated logBB values (Table S2), both L1 and L2 satisfy these requirements, suggesting that these compounds should be capable of crossing the BBB.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [31] Scott LE Orvig C Chem Rev 2009 109 4885 19637926 source
    • cites [75] Lipinski CA Lombardo F Dominy BW Feeney PJ Adv Drug Del Rev 2001 46 3 11259830 source

  • May combine two claims.

    Premiseown data

    L2 is a tridentate ligand that can generate metal complexes with different stoichiometry in solution versus the solid state.

    “L2 is a tridentate ligand that can generate metal complexes with different stoichiometry in solution versus the solid state.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The tested BFCs exhibit both amyloid-binding affinity and fluorescence properties similar to ThT.

    “These studies provide further evidence that the tested BFCs exhibit both amyloid-binding affinity and fluorescence properties similar to ThT”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • May combine two claims.

    Interpretationreasoning

    The amyloid binding affinity is more sensitive to the presence of metal ions for L2, possibly due to its weaker metal-binding ability and the formation of a 1:2 metal complex in solution.

    “This suggests that the amyloid binding affinity is more sensitive to the presence of metal ions for the latter compound, possibly due to its weaker metal-binding ability and the formation of a 1:2 metal complex in solution (vide supra).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • Classified as probably not a substantial claim.

    Premisenone given

    The compounds described contain a 2-phenylbenzothiazole fragment reminiscent of Thioflavin T (ThT), a common fluorescent dye used to detect the beta sheet structure of fibrillar Aβ aggregates.

    “The compounds described herein contain a 2-phenylbenzothiazole fragment reminiscent of Thioflavin T (ThT), a common fluorescent dye used to detect the beta sheet structure of fibrillar Aβ aggregates.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    These pM values are comparable to those calculated for DTPA, suggesting that L1 and L2 have high metal-binding affinity, especially for Cu2+ ions.

    “Interestingly, these pM values are comparable to those calculated for the strong chelating agent DTPA (diethylenetriaminepentaacetic acid), suggesting that our compounds have a high metal-binding affinity, especially for Cu2+ ions.78”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [78] Martell AE Smith RM Critical Stability Constants Plenum New York 1976 IV

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationown data

    Overall, the tested BFCs bind tightly to Aβ fibrils and appending a metal-binding arm to the 2-phenylbenzothiazole group does not negatively affect the amyloid binding affinity of these compounds.

    “Overall, these studies strongly suggest that the tested BFCs bind tightly to Aβ fibrils and that appending a metal-binding arm to the 2-phenylbenzothiazole group does not negatively affect the amyloid binding affinity of these compounds.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • May combine two claims.

    Interpretationown data

    The Ki value for L1 is similar to the Kd value obtained directly, while the Ki value obtained for L2 shows an even stronger binding affinity to Aβ fibrils.

    “While the Ki value for L1 is similar to the Kd value obtained directly, the Ki value obtained for L2 shows an even stronger binding affinity to Aβ fibrils.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • May combine two claims.

    Premisecitation

    Other reported BFCs have employed benzothiazole fragments as amyloid-binding motifs, but no binding affinities for the Aβ species have been measured for those systems.

    “While other reported BFCs have employed benzothiazole fragments as amyloid-binding motifs, no binding affinities for the Aβ species have been measured for those systems.49,53,54”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [49] Scott LE Telpoukhovskaia M Rodriguez-Rodriguez C Merkel M Bowen ML Page BDG Green DE Storr T Thomas F Allen DD Lockman PR Patrick BO Adam MJ Orvig C Chem Sci 2011 2 642

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [53] Zhang Y Chen LY Yin WX Yin J Zhang SB Liu CL Dalton Trans 2011 40 4830 21437337 source
    • cites [54] Dedeoglu A Cormier K Payton S Tseitlin KA Kremsky JN Lai L Li XH Moir RD Tanzi RE Bush AI Kowall NW Rogers JT Huang XD Exp Gerontol 2004 39 1641 15582280 source

  • May combine two claims.

    Interpretationcitation

    The highest three pKa values of L2 are assigned to deprotonation of the pyridinium group, the ammonium group, and the phenol group, respectively; the low pKa of 1.94(1) is assigned to deprotonation of the nitrogen atom of the benzothiazole group.

    “The highest three pKa values can be assigned to the deprotonation of the pyridinium group, the ammonium group, and the phenol group, respectively, similar to the values obtained for L1. In addition, the low pKa value of 1.94(1) is assigned to the deprotonation of the nitrogen atom of the benzothiazole group, similar to previous reports.77”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [77] Perrin DD Dissociation constants of organic bases in aqueous solution Butterworths London 1972

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisereasoning

    L1 is a tetradentate ligand and thus is expected to form 1:1 Cu and Zn complexes.

    “While L1 is a tetradentate ligand and thus is expected to form 1:1 Cu and Zn complexes”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    L1 exhibits a high affinity for Aβ fibrils comparable to other neutral ThT derivatives, suggesting that appending a metal-binding group to the 2-phenylbenzothiazole fragment does not limit its amyloid binding affinity.

    “This value suggests that L1 exhibits a high affinity for the Aβ fibrils comparable to other neutral ThT derivatives,83,85 suggesting that appending a metal-binding group to the 2-phenylbenzothiazole fragment does not limit its amyloid binding affinity.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [83] Klunk WE Wang YM Huang GF Debnath ML Holt DP Mathis CA Life Sci 2001 69 1471 11554609 source
    • cites [85] Yona RL Mazeres S Faller P Gras E ChemMedChem 2008 3 63 17926318 source
    • Rests on an assumption: The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

  • May combine two claims.

    Interpretationown data

    The formation of larger soluble Aβ42 oligomers in presence of L1 is not as pronounced as that observed for L2, which likely leads to an increased cell survival for L1 vs. L2.

    “The formation of larger soluble Aβ42 oligomers in presence of L1 is not as pronounced as that observed for L2 (Figures 9 and 10, lanes h vs. e), which likely leads to an increased cell survival for L1 vs. L2 (Figure 11, lanes 10–11 vs. 6–7).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The metal ions and compounds tested have an inhibitory effect on Aβ42 fibrillization, suggesting that these bifunctional chelators can modulate the neurotoxicity of the formed Aβ42 species.

    “These studies clearly show the metal ions and compounds tested have an inhibitory effect on Aβ42 fibrillization, suggesting that these bifunctional chelators can modulate the neurotoxicity of the formed Aβ42 species (vide infra).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Both inhibition and disaggregation studies show that L1 and L2 are able to control the Aβ aggregation process both in the absence and presence of metal ions, highlighting the bifunctional character of these compounds.

    “Overall, both inhibition and disaggregation studies show that L1 and L2 are able to control the Aβ aggregation process both in the absence and presence of metal ions, highlighting the bifunctional character of these compounds.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Both Cu2+ and Zn2+ ions lead to a reduced ThT fluorescence, due to emission quenching by the paramagnetic Cu2+ ions or Zn2+-induced formation of non-fibrillar Aβ aggregates.

    “In addition, both Cu2+ and Zn2+ ions lead to a reduced ThT fluorescence, due to emission quenching by the paramagnetic Cu2+ ions or Zn2+-induced formation of non-fibrillar Aβ aggregetes.41,88”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [41] Tõugu V Karafin A Zovo K Chung RS Howells C West AK Palumaa P J Neurochem 2009 110 1784 19619132 source
    • cites [88] Garai K Sahoo B Kaushalya SK Desai R Maiti S Biochemistry 2007 46 10655 17718543 source
66 of 66

  • The paper relies on this without support.

    L1 and L2 are the first bifunctional chelators for which Aβ fibril binding affinities were measured.

    “L1 and L2 are, to the best of our knowledge, the first bifunctional chelators for which Aβ fibril binding affinities were measured.”

  • The paper relies on this without support.

    This is the first detailed study of the interaction of bifunctional compounds with the more aggregation-prone Aβ42 peptide.

    “Most notably, this is the first detailed study of the interaction of bifunctional compounds with the more aggregation-prone Aβ42 peptide, which is proposed to be physiologically relevant due to the formation of Aβ42 oligomers.10,11,18–20”

  • The paper relies on this without support.

    The Aβ40 fibrils used for binding assays are a valid surrogate for Aβ42 fibrils in assessing L1/L2 binding affinity.

    “These studies were performed with Aβ fibrils obtained from the Aβ40 peptide, which forms more homogenous fibrillar structures without any non-fibrillar aggregates (Figure S21a).83,84”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The presence of Cu2+ ions inhibits the formation of large soluble and insoluble Aβ42 aggregates.

    “the presence of Cu2+ ions inhibits the formation of large soluble and insoluble Aβ42 aggregates (Figure 7, lane 2).”

    From Small Bifunctional Chelators That Do Not Disaggregate Amyloid β Fibrils Exhibit Reduced Cellular Toxicity (2014) · cites this paper as [20]

    In Results and Discussion, ‘Effect of L1 and L2 on Aβ42 Aggregation’ (page unavailable), the paper reports almost no fibrils after 24 hours in the presence of Cu, supporting inhibition of large insoluble aggregates. It also reports soluble Aβ42 oligomers of 10–110 kDa and says metal ions stabilize soluble oligomers, so it does not support inhibition of large soluble aggregates. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Zn2+ promotes formation of nonfibrillar aggregates.

    “Several studies showed that Zn2+ promotes formation of nonfibrillar aggregates,16,29–31 yet conflicting results have been reported for the Cu2+-mediated Aβ aggregation.”

    From The effect of Cu2+ and Zn2+ on the Aβ42 peptide aggregation and cellular toxicity (2013) · cites this paper as [29]

  • The majority of these BFCs have been studied for their effect on aggregation of the Aβ40 peptide, and fewer studies have focused on their interaction with the more neurotoxic Aβ42 peptide.

    “However, the majority of these BFCs have been studied for their effect on aggregation of the Aβ40 peptide,25,31 and fewer studies have focused on their interaction with the more neurotoxic Aβ42 peptide.20,21”

    From Small Bifunctional Chelators That Do Not Disaggregate Amyloid β Fibrils Exhibit Reduced Cellular Toxicity (2014) · cites this paper as [20]

  • Cu2+ ions slow down fibrillization of Aβ42 peptide and stabilize soluble Aβ42 species.

    “We have also recently reported that Cu2+ ions slow down fibrillization of the Aβ42 peptide and stabilize the soluble Aβ42 species, as observed by native gel electrophoresis/Western blotting, TEM, cell viability studies,20,21 and pulsed hydrogen/deuterium exchange mass spectrometry studies.22”

    From Small Bifunctional Chelators That Do Not Disaggregate Amyloid β Fibrils Exhibit Reduced Cellular Toxicity (2014) · cites this paper as [20]

  • The approach of inhibiting metal-mediated Aβ40 aggregation or promoting disaggregation may not be optimal for the Aβ42 peptide, given the increased toxicity observed for soluble Aβ42 oligomers.

    “However, this approach may not be optimal for the Aβ42 peptide, given the increased toxicity observed for soluble Aβ42 oligomers.20,21”

    From Small Bifunctional Chelators That Do Not Disaggregate Amyloid β Fibrils Exhibit Reduced Cellular Toxicity (2014) · cites this paper as [20]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • L1 exceeds the stated blood-brain barrier molecular-weight limit

    Major

    The paper says both compounds satisfy a molecular-weight limit of 450, but the reported mass of L1 plus a proton is 469.1698. L1's molecular weight is therefore about 468, above the stated limit.

  • The same starting material has incompatible mass-to-amount ratios

    Minor

    The two syntheses name the same benzothiazole starting material, but 2.113 g divided by 8.99 mmol implies about 235 g/mol, whereas 0.5 g divided by 1.923 mmol implies about 260 g/mol.

  • The extra metal-binding arm is attributed to the wrong ligand

    Minor

    The proposed explanation for L1's larger binding constants says L2 has the additional metal-binding arm. Elsewhere, the paper describes L1 as tetradentate and L2 as tridentate, indicating the opposite.

  • Linkage design is assigned to two different approaches

    Minor

    The introduction identifies the linkage strategy as approach B, whereas the results identify it as approach A.

  • L2 absorption maximum differs between sections

    Minor

    The synthesis section reports L2's longer-wavelength MeCN absorption maximum as 348 nm, while the results report it as 330 nm.

  • Zn-L1 complex has four versus two perchlorates

    Minor

    The heading assigns four perchlorate ions to complex 2, but its analytical formula contains only two chlorine atoms and thus only two perchlorates.

6 of 6

Cited works that were retracted

Works this paper cites that were later retracted, from the retraction notices publishers deposit. Major when the notice came out before this paper was published.

  • Cites a retracted work: 10.1038/nature04533

    Info

    The cited work was retracted on 2024-06-24 (notice 10.1038/s41586-024-07691-8), not before this paper was published (2012-04-06).

    Cited work 10.1038/nature04533 · retracted 2024-06-24 · notice 10.1038/s41586-024-07691-8 · this paper published 2012-04-06

1 of 1

Cites

1 retracted

Flagged first, then by citations

1 of the 99 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. Gans P., 1999, Ann. Chim., 45

Cited by

Sorted by citations

Related

Authors
Sharma, A. K., Pavlova, S. T., Kim, J., Finkelstein, D., Hawco, N. J., Rath, N. P., Kim, J., & Mirica, L. M.
Affiliations
  • Washington University in St. Louis (US)
  • University of Missouri–St. Louis (US)
Corresponding author
Mirica, Liviu M.
ORCID
Venue
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Published
2012-04-06
Volume
134
Issue
15
Pages
6625-6636
ISSN
  • 0002-7863 (ISSN-L)
  • 1520-5126
DOI
10.1021/ja210588m
PMC
PMC3368506
OpenAlex
W2017489767
Semantic Scholar
f4ab466027f9ae03dd585081a4a08811314cf258
Cited by
202
References
99
Citations by year
2026: 4 · 2025: 3 · 2024: 10 · 2023: 10 · 2022: 12 · 2021: 10 · 2020: 13 · 2019: 16 · 2018: 21 · 2017: 17 · 2016: 24 · 2015: 15 · 2014: 24 · 2013: 15 · 2012: 7
FWCI
11.51
Type
journal article
Language
en
Open access
Locations
  • Journal of the American Chemical Society (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (submittedVersion)
  • PubMed Central (submittedVersion)
Funders
  • National Institutes of Health (5p41rr000954-34, 5p50ag005681-36, 5p30ns069329-02)
  • National Institute on Aging (P50‐AG005681, P 50 AG05681)
  • National Institute of Neurological Disorders and Stroke (P30-NS069329, P30NS69329)
  • National Center for Research Resources (P41-RR000954)
Topics
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Health Sciences › Medicine › Pharmacology › Cholinesterase and Neurodegenerative Diseases
  • Health Sciences › Medicine › Psychiatry and Mental health › Dementia and Cognitive Impairment Research
Keywords
Alzheimer's disease, metal-peptide interactions, copper ions, zinc ions, bifunctional molecules, metal chelation, amyloid fibril disaggregation, aggregation inhibition, soluble oligomers, neurotoxicity
MeSH terms
Alzheimer Disease, Chelating Agents, Copper, Humans, Metals, Zinc, Amyloid beta-Peptides, Protein Multimerization

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-17.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-17.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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