Hadak Útján. A népvándorlás kor fiatal kutatóinak konferenciája (Szeged, 2000)

Csapó János - Csapó-Kiss Zsuzsanna - Csapó János jun.: Mira használható az aminosavanalitika a régészetben?

CSAPÓ János — CSAPÓ-KISS Zsuzsanna - CSAPÓ János jun.

WHAT AMINO ACIDS ANALYTICS CAN BE USED IN ARCHAEOLOGY FOR?

CSAPÓ János - CSAPÓ-KISS Zsuzsanna - CSAPÓ János jun.

Racemization of free amino acids is considerably lower than that of amino acids bound in peptide. In the same experimental conditions, the rate of racemization of free amino acids is only 20-80% of that of peptide bound amino acids. When using to traditional protein hydrolysis, racemization was 1,2-1,6 times as high as that obtained at high temperatures (160-180 °C), under conditions ensuring total hydrolysis of the protein. This lower degree of racemization may be explained by the fact that, at high temperatures, the protein hydrolyses more rapidly into free amino acids and the racemization of free amino acids is considerably slower that of amino acids bound in polypeptides. When hydrolysis is conducted at lower temperatures for longer times, the amino acids bound in the peptide chain are exposed for a longer time to the effects actually causing racemization. As a result, we may say that any factor which speeds up hydrolysis, will lower the degree of racemization. After 48 hours at 110 °C and in presence of 4M barium hydroxide, all amino acids (whether free or bound in peptide) totally racemized. Therefore the racemization of tiyptophan cannot be determined using barium hydroxide promoted protein hydrolysis. High temperature hydrolysis (at 160 °C for 45 to 60 minutes, at 170 °C for 30-45 minutes and 180 °C for 30 minutes) are recommended for those who would like to hydrolyse the protein for short times and to determine the degree of racemization occurring in the polypeptide chain, but do not wish to use enzyme hydrolysis.

After developing protein hydrolysis method with low racemization, a method has been developed to determine the age of fossil bone samples based on amino acid racemization (AAR). Approximately one hundred fossil bone samples of known age from Hungary were collected and analysed for D- and L-amino acids. As the racemization of

Csapó János

Kaposvári Egyetem, Allattudományi Kar 7401 Kaposvár Guba S. u. 40.

Pf 16.

Csapó János jun.

JPTE Természettudományi Kar Természetföldrajzi Tanszék 7624 Pécs Ifjúság u. 6.

amino acids is affected by temperature, pH, metal content of the soil, and time passed since death, these factors were eliminated by comparing the estimated age to age determined by the radiocarbon method. Determining the D- and L- amino acid contents in samples of known age, determining the half life of racemization and plotting the D/L ratio as a function of time, calibration curves were obtained. These curves can be used for the age estimation of samples after determining their D- and L-amino acid content. The D/L ratio for 2 to 3 amino acids was determined for each sample and the mean value of estimated ages based on calibration curves was considered to estimate age of the fossil samples.

After this a method for evaluation of age of wool carpets and textiles was developed based on the age dependent alteration of amino acid composition of proteins. Samples of 23 wool carpets and textiles of known age, obtained from the Hungarian Museum of Industrial Arts and the Hungarian National Museum were analysed for amino acid content. Results were compared with data obtained for contemporary, untreated wool and wool carpet. The cysteic acid content of wool increased with age. The contemporary wool carpet contained 0,31 g of cysteic acid in 100 g of protein. Comparable figures were 1,87 g for 550-year old carpet and 4,01-4,39 g for the 1600-1750-year old wool carpets. Cystine content decreased with age corresponding figures being 7,88, 3,12, 1,19-0,97, respectively. Corresponding contents of methionine were 0,43, 0,21, and 0,20-0 and for tyrosine were 3,07, 2,11 and 0,20-0. Prediction equations were developed as linear regressions of age of wool on cysteic acid, cystine and tyrosine contents. The 95% confidence intervals of estimates for two samples of unknown age were estimates plus or minus 30 and 38 years.

Csapó-Kiss Zsuzsanna Kaposvári Egyetem, Allattudományi Kar 7401 Kaposvár Guba S. u. 40.

Pf 16.

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