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

be the result of incomplete hydrolysis. In a preliminary experiment wool samples were hydrolysed for 24, 48, 72, 96 and 120 hours with 6M HCl. The results were used to establish hydrolysis time for the main experiment. 3.2.3. Analysis of amino acids Samples were analysed with the LKB 4101 (LKB Biochrom, England) automatic amino acid analyser. The amino acid standard and cysteic acid were obtained from Merck (E. Merck, Darmstadt, Gennany). The analysis conditions were: The flow rates of the buffers were 50 ml/h, and the flow rate of ninhydrin was 25 ml/h. The other parameters were those recommended by the manufacturer of the amino acid analyser for amino acid analysis.The analysis of amino acids was performed according to the method described previously (CSAPÓ ET AL., 1986). 3.2.4. Preliminary comparison of modern and older wool samples Five samples each of modern wool, a modern carpet and a 550-year-old carpet were subjected to amino acid analysis. The complete amino acid profile was determined on each of these samples. The contrasts of means Wool + Modem Carpet _ Qfá Carpet 2 were tested by the t-test. 3.2.5. Statistical analysis of the data Based on the hypothesis that carpet age can be estimated from amino acid analysis, known age (y) was regressed on cysteic acid, cystine, methionine and tyrosine contents and on the ratio cysteic acid/cystine. Accuracies of the functions were measured by correlation between predicted age ( y ) and actual age (y) and by standard deviation of the difference (y- y ) designated as Sy^. 3.3. Results and discussion 3.3.Í. The influence of hydrolysis time on the amino acid composition of wool The amino acid contents of the wool of Hungarian merino sheep, after being subjected to various hydrolysis times, are shown in Table 12. It may seem, from the data, that cystine is the only amino acid undergoing significant change as a result of changing hydrolysis times. However, regression analysis showed that there were significant (P < .05) increases in levels of aspartic acid, glutamic acid, proline and valine associated with increased hydrolysis time. Significant (P < .05) decreases were seen for cystine and tyrosine. The very large decrease in cystine content (85% after 48 hours, 72% after 72 hours and 59% after 120 hours) did not seem to be due to oxidation since cysteic acid content increased by only 27% in 120 hours. The trends of amino acids which changed with increased time of hydrolysis would suggest that as much as 72 hours hydrolysis may be desirable. However, the ninhydrin positive peaks observed after 24 hours were not observed after 48 hours of hydrolysis. The decision was made to use 48 hour hydrolysis in the remainder of this study.