Achaeometrical Research in Hungary II., 1988

PROSPECTING and DATING - János CSAPÓ - Zsuzsanna CSAPÓ-KISS - János CSAPÓ JR.: How the amino acids and amino acid racemization can be used and with what limits for age determination of fossil materials in archaeometry

Table 4 D-amino acid content of lysozyme (A), cytochrome (В) and fossile bone (С) hydrolysed by 6 M hydrochloric acid at different temperatures for different times Amino acid 6 M HCl Amino acid 110 °C for 24 h 160 °C for 60 min. A В С A В С Asp 6.62 7.01 7.89 3.27 3.42 4.15 GIu 4.58 4.61 5.93 2.79 2.84 3.61 Thr 3.62 3.74 4.38 2.29 2.31 3.14 Ala 2.99 3.21 4.02 1.69 1.65 2.13 Val 2.11 2.24 2.53 1.69 1.84 2.33 Phe 3.31 3.42 3.64 3.19 3.37 3.57 His 1.83 1.89 2.38 1.64 1.67 2.01 Data expressed as in Table 1. 1.3.2. Influence of the hydrolysis method on the D-amino acid content of lysozyme, cytochrome С and fossil bone After the experiments with ribonuclease, we hydrolysed lysozyme, cytochrome С and fossil bone sample using the traditional method. The results thus obtained were compared with the data obtained at 160 °C for 60 minutes, at 170 °C for 45 and 60 minutes and finally at 180 °C for 30 minutes. The degree of racemization was compared among the various hydrolysis conditions. The selection of the these time-temperature combinations was based on the time-temperature combinations required to produce total amino acid hydrolysis. The data in Tables 4 and 5, show that the degrees of racemization for lysozyme and cytochrome С were virtually identical to that obtained for ribonuclease at the same time and temperature. In the case of bone samples, for each temperature-time combination, we obtained degrees of racemization 15-25% higher than that of the three pure proteins. The higher racemization may be partially explained by the mineral matter content of bone. It is known that, with the exception of nickel, heavy metals catalyse the racemization of amino acids. Table 5 D-amino acid content of lysozyme (A), cytochrome (B) and fossile bone (C) hydrolysed by 6 M hydrochloric acid at different temperatures for different times Amino acid 6 M HCl Amino acid 170 °C for 45 min 180 °C for 30 min Amino acid A В С A В С Asp 3.29 3.57 4.42 3.84 3.99 4.67 Glu 2.81 2.89 3.74 3.51 3.63 3.92 Thr 2.11 2.23 3.04 2.87 3.14 3.42 Ala 1.72 1.77 2.11 2.81 2.89 3.04 Val 1.71 1.82 2.27 2.54 2.57 2.82 Phe 2.89 3.11 3.60 2.97 2.83 3.20 His 1.52 1.60 1.99 1.79 1.93 2.11 Data expressed as in Table 1. 28