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Closed-system behaviour of the intra-crystalline fraction of amino acids in mollusc shells

Penkman, K.E.H., Kaufman, D.S., Maddy, D., Collins, M.J.·2008·Quaternary Geochronology
DOI 10.1016/j.quageo.2007.07.001PMC PMC2727006
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Fig. 1 Change in THAA concentration (6 h hydrolysis) of Asx with oxidation time in H2O2 for Corbicula (left) and Margaritifera (right).
Fig. 1 Change in THAA concentration (6 h hydrolysis) of Asx with oxidation time in H2O2 for Corbicula (left) and Margaritifera (right).CC BY · PubMed Central
Fig. 2 Decline in the amino acid concentration with oxidation time using NaOCl. Upper: THAA concentration of Asx (6 h hydrolysis) for Corbicula (left) and Margaritifera (right). Other amino acids show similar trends (Fig. 4). The particle size of the powder does not appear to affect the extent of oxidation. Lower: THAA (24 h hydrolysis; left) and FAA (right) concentrations of Asx, Glx, and Ala for Bithynia.
Fig. 2 Decline in the amino acid concentration with oxidation time using NaOCl. Upper: THAA concentration of Asx (6 h hydrolysis) for Corbicula (left) and Margaritifera (right). Other amino acids show similar trends (Fig. 4). The particle size of the powder does not appear to affect the extent of oxidation. Lower: THAA (24 h hydrolysis; left) and FAA (right) concentrations of Asx, Glx, and Ala for Bithynia.CC BY · PubMed Central
Fig. 3 Absolute abundance of 11 amino acids before and after oxidation with H2O2 and NaOCl for Corbicula (left) and Margaritifera (right). The concentration of each amino acid decreases on oxidation.
Fig. 3 Absolute abundance of 11 amino acids before and after oxidation with H2O2 and NaOCl for Corbicula (left) and Margaritifera (right). The concentration of each amino acid decreases on oxidation.CC BY · PubMed Central
Fig. 4 Amino acid composition in Corbicula, Margaritifera and Bithynia shells, unbleached (left) and after oxidation with NaOCl for 48 h (right). The colours for each amino acid follow the convention of RasMol. The concentration of the silk-like protein decreases relative to that of the acidic amino acids in bleached Margaritifera and Bithynia.
Fig. 4 Amino acid composition in Corbicula, Margaritifera and Bithynia shells, unbleached (left) and after oxidation with NaOCl for 48 h (right). The colours for each amino acid follow the convention of RasMol. The concentration of the silk-like protein decreases relative to that of the acidic amino acids in bleached Margaritifera and Bithynia.CC BY · PubMed Central
Fig. 5 Change in Asx D/L in the THAA with oxidation time using NaOCl. Upper: Asx D/L for Corbicula (left) and Margaritifera (right). Lower: D/L in Asx, Glx and Ala for Bithynia.
Fig. 5 Change in Asx D/L in the THAA with oxidation time using NaOCl. Upper: Asx D/L for Corbicula (left) and Margaritifera (right). Lower: D/L in Asx, Glx and Ala for Bithynia.CC BY · PubMed Central
Fig. 6 Conceptual model of the effect of bleach on different amino acid fractions in a shell (upper figure modified from Sykes et al., 1995). The highly racemized FAA in the matrix (1) are removed first, leading to a small drop in concentration but a decrease in the D/L value. A rise in D/L coincides with a rapid drop in concentration as the intact proteins of the matrix (2) are removed. Prolonged bleaching may selectively remove amino acids in the intra-crystalline fraction or begins to etch the carbonate, thereby exposing intra-crystalline amino acids (3). This coincides with only a small drop in concentration. At this point the bleaching could induce further racemization, or it could oxidize the less-racemized molecules. The increase in racemization is minimal, however.
Fig. 6 Conceptual model of the effect of bleach on different amino acid fractions in a shell (upper figure modified from Sykes et al., 1995). The highly racemized FAA in the matrix (1) are removed first, leading to a small drop in concentration but a decrease in the D/L value. A rise in D/L coincides with a rapid drop in concentration as the intact proteins of the matrix (2) are removed. Prolonged bleaching may selectively remove amino acids in the intra-crystalline fraction or begins to etch the carbonate, thereby exposing intra-crystalline amino acids (3). This coincides with only a small drop in concentration. At this point the bleaching could induce further racemization, or it could oxidize the less-racemized molecules. The increase in racemization is minimal, however.CC BY · PubMed Central
Fig. 7 Unbleached, pre-heated bleached, and post-heated bleached concentration of Asx in the THAA under hydrous conditions for Corbicula (left) and Margaritifera (right) heated at 140 °C.
Fig. 7 Unbleached, pre-heated bleached, and post-heated bleached concentration of Asx in the THAA under hydrous conditions for Corbicula (left) and Margaritifera (right) heated at 140 °C.CC BY · PubMed Central
Fig. 8 Concentration of Asx (left) and Ala (right) for FAA and THAA (6 h hydrolysis) for the bleached Corbicula powder during heating at 140 °C. The increase in abundance of THAA (except Asx) in the early time steps suggests incomplete preparatory hydrolysis.
Fig. 8 Concentration of Asx (left) and Ala (right) for FAA and THAA (6 h hydrolysis) for the bleached Corbicula powder during heating at 140 °C. The increase in abundance of THAA (except Asx) in the early time steps suggests incomplete preparatory hydrolysis.CC BY · PubMed Central
Fig. 9 Relative composition of Asx in each of the four fractions of Bithynia shell during heating at 140 °C: intra-crystalline free, intra-crystalline bound, inter-crystalline free, and inter-crystalline bound.
Fig. 9 Relative composition of Asx in each of the four fractions of Bithynia shell during heating at 140 °C: intra-crystalline free, intra-crystalline bound, inter-crystalline free, and inter-crystalline bound.CC BY · PubMed Central
Fig. 10 Percentage of THAA in supernatant water (uncorrected for procedural blank) compared to that within the shells, for unbleached and bleached Corbicula (left) and Bithynia (right) shell at 140 °C. Unbleached shells (u=closed symbols) leach a higher percentage of amino acids into the water compared to bleached shells (b=open symbols).
Fig. 10 Percentage of THAA in supernatant water (uncorrected for procedural blank) compared to that within the shells, for unbleached and bleached Corbicula (left) and Bithynia (right) shell at 140 °C. Unbleached shells (u=closed symbols) leach a higher percentage of amino acids into the water compared to bleached shells (b=open symbols).CC BY · PubMed Central
Fig. 11 Racemization of bleached Bithynia tentaculata shell at 140 °C in the FAA (left) and THAA (right). The upper graphs show the measured D/L values; the lower graphs show the data plotted as ln{(1+D/L)/(1−D/L)} vs. time. If the reaction follows reversible first-order kinetics, the relation should be linear.
Fig. 11 Racemization of bleached Bithynia tentaculata shell at 140 °C in the FAA (left) and THAA (right). The upper graphs show the measured D/L values; the lower graphs show the data plotted as ln{(1+D/L)/(1−D/L)} vs. time. If the reaction follows reversible first-order kinetics, the relation should be linear.CC BY · PubMed Central
Fig. 12 FAA D/L vs. THAA D/L for unbleached (u) and bleached (b) Asx and Glx (left) and Ala and Val (right) for Margaritifera (upper) and Bithynia (lower) shell heated at 140 °C under hydrous conditions.
Fig. 12 FAA D/L vs. THAA D/L for unbleached (u) and bleached (b) Asx and Glx (left) and Ala and Val (right) for Margaritifera (upper) and Bithynia (lower) shell heated at 140 °C under hydrous conditions.CC BY · PubMed Central
Fig. 13 Concentration vs. THAA D/L for Asx for bleached and unbleached fossil shells. Upper: [THAA] for Bithynia. Middle: [THAA] and [FAA] for unbleached (left) and bleached (right) Valvata. Lower: [THAA] and [FAA] for unbleached (left) and bleached (right) Corbicula. Insets show an expanded scale.
Fig. 13 Concentration vs. THAA D/L for Asx for bleached and unbleached fossil shells. Upper: [THAA] for Bithynia. Middle: [THAA] and [FAA] for unbleached (left) and bleached (right) Valvata. Lower: [THAA] and [FAA] for unbleached (left) and bleached (right) Corbicula. Insets show an expanded scale.CC BY · PubMed Central
Fig. 14 Concentrations for unbleached (u) and bleached (b) FAA and THAA fractions for Valvata piscinalis and Bithynia tentaculata from Funthams Lane, and Bithynia tentaculata from Purfleet. Error bars are one standard deviation about the mean. Little change is observed upon bleaching for the FAA.
Fig. 14 Concentrations for unbleached (u) and bleached (b) FAA and THAA fractions for Valvata piscinalis and Bithynia tentaculata from Funthams Lane, and Bithynia tentaculata from Purfleet. Error bars are one standard deviation about the mean. Little change is observed upon bleaching for the FAA.CC BY · PubMed Central
Fig. 15 Average amino acid compositions for intra- and inter- free (F) and bound (B) amino acids within modern, MIS 7, and MIS 9 Bithynia tentaculata.
Fig. 15 Average amino acid compositions for intra- and inter- free (F) and bound (B) amino acids within modern, MIS 7, and MIS 9 Bithynia tentaculata.CC BY · PubMed Central
Fig. 16 THAA concentration vs. D/L for Asx, Glx, Ala, and Val for bleached and unbleached Bithynia tentaculata from Funthams Lane.
Fig. 16 THAA concentration vs. D/L for Asx, Glx, Ala, and Val for bleached and unbleached Bithynia tentaculata from Funthams Lane.CC BY · PubMed Central
Fig. 17 Frequency distribution of THAA D/L for Ala and Val for unbleached (■) and bleached (□) Valvata piscinalis from Funthams Lane.
Fig. 17 Frequency distribution of THAA D/L for Ala and Val for unbleached (■) and bleached (□) Valvata piscinalis from Funthams Lane.CC BY · PubMed Central
Fig. 18 THAA vs. FAA D/L Asx for bleached Bithynia shells from Funthams Lane (MIS 7) and Purfleet (MIS 9). Each of the measurements is from a single shell. Note the much greater consistency in the measurements obtained from bleached shells.
Fig. 18 THAA vs. FAA D/L Asx for bleached Bithynia shells from Funthams Lane (MIS 7) and Purfleet (MIS 9). Each of the measurements is from a single shell. Note the much greater consistency in the measurements obtained from bleached shells.CC BY · PubMed Central
Fig. 19 Coefficient of variation (CV) of the concentrations and D/L values of THAA in unbleached and bleached fossil samples. Upper: 15 individual unbleached (■) and bleached (□) Valvata piscinalis shell powders from Funthams Lane. Lower: CVs of bleached samples as a percentage of the CVs for unbleached samples, for the THAA concentration and D/L values from Funthams Lane (FL) Valvata piscinalis, Bithynia tentaculata and from Purfleet (P) Bithynia tentaculata. Inter-shell variability is reduced in all measures of the amino acid composition, except for D/L Ala in shells from Purfleet, where the CVs are low.
Fig. 19 Coefficient of variation (CV) of the concentrations and D/L values of THAA in unbleached and bleached fossil samples. Upper: 15 individual unbleached (■) and bleached (□) Valvata piscinalis shell powders from Funthams Lane. Lower: CVs of bleached samples as a percentage of the CVs for unbleached samples, for the THAA concentration and D/L values from Funthams Lane (FL) Valvata piscinalis, Bithynia tentaculata and from Purfleet (P) Bithynia tentaculata. Inter-shell variability is reduced in all measures of the amino acid composition, except for D/L Ala in shells from Purfleet, where the CVs are low.CC BY · PubMed Central
Fig. 20 THAA D/L for Inter-laboratory comparison samples C (ILC-C) and Z (ILC-Z), unbleached and bleached.
Fig. 20 THAA D/L for Inter-laboratory comparison samples C (ILC-C) and Z (ILC-Z), unbleached and bleached.CC BY · PubMed Central
Fig. 21 THAA D/L vs. FAA D/L for Ala for bleached (●) and unbleached (○) Bithynia (left) and Valvata (right). The trendlines are derived from kinetic experiments on the intra-crystalline fraction of the two species.
Fig. 21 THAA D/L vs. FAA D/L for Ala for bleached (●) and unbleached (○) Bithynia (left) and Valvata (right). The trendlines are derived from kinetic experiments on the intra-crystalline fraction of the two species.CC BY · PubMed Central
Fig. 22 FAA to THAA D/L correlation for each amino acid for bleached and unbleached Valvata (left) and Corbicula (right). There is no improvement upon bleaching for Corbicula, unlike that observed for the fossil gastropods.
Fig. 22 FAA to THAA D/L correlation for each amino acid for bleached and unbleached Valvata (left) and Corbicula (right). There is no improvement upon bleaching for Corbicula, unlike that observed for the fossil gastropods.CC BY · PubMed Central
Fig. 23 THAA D/L for Glx vs. Asx for Funthams Lane Bithynia tentaculata (left) and Valvata piscinalis (right). The results on bleached shells form a more coherent cluster, except for one outlier, which contains unexpectedly high amino acid concentration and is probably incompletely bleached.
Fig. 23 THAA D/L for Glx vs. Asx for Funthams Lane Bithynia tentaculata (left) and Valvata piscinalis (right). The results on bleached shells form a more coherent cluster, except for one outlier, which contains unexpectedly high amino acid concentration and is probably incompletely bleached.CC BY · PubMed Central
Fig. 24 Schematic of intra-crystalline amino acids entrapped within carbonate crystals. Unlike the proteins of the organic matrix between the crystallites, which leach from the shell with time, amino acids are entrapped in the closed intra-crystalline system. Thus the relation between the D/L values of different amino acids and between free (non-protein bound) and total hydrolysable (both free and originally protein-bound amino acids, released by acid hydrolysis) amino acids is predictable. Analysis of the whole shell results in lower-than-expected D/L values for the THAA, due to the loss of the more highly racemized FAA.
Fig. 24 Schematic of intra-crystalline amino acids entrapped within carbonate crystals. Unlike the proteins of the organic matrix between the crystallites, which leach from the shell with time, amino acids are entrapped in the closed intra-crystalline system. Thus the relation between the D/L values of different amino acids and between free (non-protein bound) and total hydrolysable (both free and originally protein-bound amino acids, released by acid hydrolysis) amino acids is predictable. Analysis of the whole shell results in lower-than-expected D/L values for the THAA, due to the loss of the more highly racemized FAA.CC BY · PubMed Central

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Authors
Penkman, K. E. H., Kaufman, D. S., Maddy, D., & Collins, M. J.
Venue
Quaternary Geochronology
Publisher
Elsevier BV
Published
2008-02
Volume
3
Issue
1-2
Pages
2-25
ISSN
1871-1014
DOI
10.1016/j.quageo.2007.07.001
PMC
PMC2727006
Cited by
205
References
0
Language
en
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