TY - JOUR
T1 - Intra-crystalline protein diagenesis (IcPD) in Patella vulgata. Part II
T2 - Breakdown and temperature sensitivity
AU - Demarchi, B.
AU - Collins, M. J.
AU - Tomiak, P. J.
AU - Davies, B. J.
AU - Penkman, K. E H
PY - 2013/4/1
Y1 - 2013/4/1
N2 - Artificial diagenesis of the intra-crystalline proteins isolated from Patella vulgata was induced by isothermal heating at 140 °C, 110 °C and 80 °C. Protein breakdown was quantified for multiple amino acids, measuring the extent of peptide bond hydrolysis, amino acid racemisation and decomposition. The patterns of diagenesis are complex; therefore the kinetic parameters of the main reactions were estimated by two different methods: 1) a well-established approach based on fitting mathematical expressions to the experimental data, e.g. first-order rate equations for hydrolysis and power-transformed first-order rate equations for racemisation; and 2) an alternative model-free approach, which was developed by estimating a "scaling" factor for the independent variable (time) which produces the best alignment of the experimental data. This method allows the calculation of the relative reaction rates for the different temperatures of isothermal heating. High-temperature data were compared with the extent of degradation detected in sub-fossil Patella specimens of known age, and we evaluated the ability of kinetic experiments to mimic diagenesis at burial temperature. The results highlighted a difference between patterns of degradation at low and high temperature and therefore we recommend caution for the extrapolation of protein breakdown rates to low burial temperatures for geochronological purposes when relying solely on kinetic data.
AB - Artificial diagenesis of the intra-crystalline proteins isolated from Patella vulgata was induced by isothermal heating at 140 °C, 110 °C and 80 °C. Protein breakdown was quantified for multiple amino acids, measuring the extent of peptide bond hydrolysis, amino acid racemisation and decomposition. The patterns of diagenesis are complex; therefore the kinetic parameters of the main reactions were estimated by two different methods: 1) a well-established approach based on fitting mathematical expressions to the experimental data, e.g. first-order rate equations for hydrolysis and power-transformed first-order rate equations for racemisation; and 2) an alternative model-free approach, which was developed by estimating a "scaling" factor for the independent variable (time) which produces the best alignment of the experimental data. This method allows the calculation of the relative reaction rates for the different temperatures of isothermal heating. High-temperature data were compared with the extent of degradation detected in sub-fossil Patella specimens of known age, and we evaluated the ability of kinetic experiments to mimic diagenesis at burial temperature. The results highlighted a difference between patterns of degradation at low and high temperature and therefore we recommend caution for the extrapolation of protein breakdown rates to low burial temperatures for geochronological purposes when relying solely on kinetic data.
KW - High-temperature experiments
KW - Intra-crystalline proteins
KW - Kinetic parameters
KW - Patella vulgata
KW - Temperature sensitivity
UR - http://www.scopus.com/inward/record.url?scp=84877139718&partnerID=8YFLogxK
U2 - 10.1016/j.quageo.2012.08.001
DO - 10.1016/j.quageo.2012.08.001
M3 - Journal article
AN - SCOPUS:84877139718
SN - 1871-1014
VL - 16
SP - 158
EP - 172
JO - Quaternary Geochronology
JF - Quaternary Geochronology
ER -