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

We have utilised this method very successfully for dating fossil bone samples from Hungary. The difference between the data from the calibration curve and those from 14

C dating was generally negligible. We were very cautious with both sample selection and preparation; the unknown samples were mainly of origin similar to those from which the calibration curves were formulated and sample preparation was carried out exactly the same for samples of known and unknown ages. We are aware of the weak points of this method and the possible errors associated with 14

C dating. However, the results support the reliability of this method. Our calibration curves should not be used in other environments because of different conditions (e.g. temperature, pH, soil composition). However, based on these results, other calibration curves can be formulated for each environment based on methods described here. 3. Age estimation of old carpets based on cystine and cysteic acid content 3.1. Introduction In earlier publications (CSAPÓ ET AL., 1990a) investigated racemization of amino acids, and found that samples whose protein contents were less than 2000-3000 years of age (mostly bones) were unsuitable for age determination using racemization. Examination of the amino acid composition of these samples revealed that the majority of cystine had decomposed or oxidised to cysteic acid while tyrosine and methionine had all but disappeared from these ancient samples. Based on these findings, it was assumed that there must be a correlation between the age of the "recent" bone samples and their cystine, cysteic acid, methionine and tyrosine contents. After analysing some 50 bone samples, it was realised that the main protein constituent of bone (collagen) has a low concentration of sulphurous amino acids and that this method cannot be used for age estimation. Following this conclusion, the amino acid contents of various wool carpets and textiles of known age were examined to investigate possible links between amino acid contents (cystine, cysteic acid, methionine, tyrosine) and age. In a review of publications found in archaeometry journals, no references to the use of amino acid composition for the determination of age were found. The basis for using the amino acids for age determination is that the two sulphur containing amino acids are sensitive to oxidation both in the free state and when bound in peptide. Further, depending on environmental conditions, cystine may decompose into alanine, homocystine and glycine (YORITAKA AND ONO, 1954) or it may transform into homocysteine, homocystine and glycine (OSONO ET AL., 1955). Methionine may also be considerably degraded by being oxidised to methionine sulfone and sulfoxide (MARTIN AND SYNGE, 1945). In order to eliminate analytical problems due to facts outlined above, (SCHRÄM ET AL., 1954; MOOR, 1963; HIRS, 1956) devised a method for determination of the two sulphurous amino acids in the oxidised state. This method has yielded considerably better results than determinations in the unoxidised state. 3.2. Experimental 3.2.1. The analysed materials Samples of Coptic textiles and wool carpets of various ages were procured from the Hungarian National Museum and the Hungarian Museum of Industrial Arts. The samples are described in Tables 10 and 11. With special care taken to minimize damage to these textiles and carpets, portions of 20-100 mg were removed from the fabric for analysis. New wool from Hungarian Merino sheep was procured from our ownexperimental farm. 36