GAS CHROMATOGRAPHIC ANALYSIS OF AMINO ACIDS AS ETHYL CHLOROFORMATE DERIVATIVES.
MICHAEL R. SCHILLING, & HERANT P. KHANJIAN
1 APPENDIX 1
1.1 AMINO ACIDS THAT MAY BE FOUND IN ACID HYDROLYSATES OF PROTEINS
2 APPENDIX 2
2.1 CORRELATION COEFFICIENTS
A useful statistical tool for determining the degree of association between data sets is the correlation coefficient (Anderson 1987). It is defined by the following equation:
where X and Y are the concentrations for each amino acid, n is the number of amino acid measured, and r is the correlation coefficient. By definition, sample data are represented by X and reference data are represented by Y. A correlation coefficient of 1.0 indicates perfect correlation, a value of 0.0 indicates that no correlation exits. Many database software packages (such as Lotus 123 and Excel) contain formulas for calculating coefficients for data sets automatically. Otherwise manual calculations can be performed, but are a bit tedious.
Sinkai and Sugisita (1990) used correlation coefficients to identify proteins in adhesives, by comparing concentration data for adhesives samples to data for proteinaceous reference materials and materials that contain amino acids, such as rice starch, glue casein, egg yolk, and gelatin. The method was quite successful and provided an easy means for comparing large data sets.
3 APPENDIX 3
3.1 AMINO ACID COMPOSITION DATA FOR VARIOUS PROTEINS
4 APPENDIX 4
4.1 STABLE AMINO ACID COMPOSITION DATA FOR VARIOUS PROTEINS
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Pigments obtained from Kremer Pigments Inc., 61 East Third St., New York, N.Y. 10003
Names and addresses of other suppliers of materials and equipment are listed in Schilling et al. 1996.
MICHAEL R. SCHILLING earned his B. S. (1983) and M.S. (1990) in chemistry from the California State Polytechnic University, Pomona. He has worked at the Getty Conservation Institute since 1983 and presently holds the position of associate scientist. His interests are thermoanalytic methods, light microscopy, gas chromatography, mass spectrometry, and color measurement. He has been active in the examination of painted museum objects, pigment identification, binding medium analysis, and analysis of volatile organic compounds in the museum environment. He has also been involved in a number of special GCI collaborative projects: conservation of the wall paintings in the tomb of Nefertari, located in Luxor, Egypt; preservation of the wall paintings and sculptures in the Dunhuang and Datong grottoes, China; and conservation of the Dead Sea scrolls in Jerusalem, Israel. Address: Getty Conservation Institute, Scientific Program, 4503 Glencoe Ave., Marina del Rey, Calif. 90292.
HERANT P. KHANJIAN received his B.A. degree in chemistry from California State University, Northridge. His research interests involve the detection and identification of binding media found in art objects using gas chromatography and infrared spectroscopy. Address as for Schilling.