0023-6152

AA00247166

22552

Unrefereed

1) A method of estimating cysteine (or SH compounds) and cystine (or S.S compounds) in tissues and biological fluids was described. In this method, first of all, proteins are removed by means of sulphosalicylic acid, and then the filtrate of the protein coagulum is made to hold a definite concentration of the acid. Cysteine compounds are estimated in this solution by titration with a standard iodate solution in the presence of a certain quantity of iodide. Cystine compounds, after being reduced into cysteine compounds, are estimated in the same way. 2) Trichloracetic acid is as effective as sulphosalicylic acid as a protein-precipitant. But as the solvent for cysteine the latter is superior to the former, giving much more accurate results. Furthermore, in trichloracetic acid solution, the reduction of cystine to cysteine is in complete, which results in inaccurate estimation. Consequently sulphosalicylic acid is preferable in either the estimation of cysteine compounds or that of cystine compounds. 3) As a titrating solution for cysteine, an iodate solution in presence of some iodide is superior to an iodine solution, giving much more accurate results. Furthermore iodate solution, as a rule, is stable for several months or a year. 4) By this method, only minute traces or no traces of cysteine, cystine and their derivatives were obtained from blood serum and boiled milk, and when pure cysteine and cystine were added to these samples, they were recovered quantitatively. Consequently, the constituents of the serum and the boiled milk have probably no influence upon this method. 5) All the extracts from fresh animal tissues examined contain cysteine and cystine compounds, the former predominating. The quantity of these compounds decreases rapidly at room temperature, but slowly in a frozen state or in a strongly acid solution. 6) Some fruits examined contain no cysteine compounds, but roots and seeds contain both cysteine and cysline compounds. During the maturation of peas, the quantity of these compounds varies.