Amino acid elements of normal human aqueous fluid protein.

EARLY analyses of the proteins of the normal aqueous humour by Franceschetti and Wieland (1928), and later by Kronfeld (1941) and Kronfeld and others (1941), have shown a content of 10 to 20 mg. per cent. Any functional significance this protein may have is unknown. However, the human lens contains 30-40 p' r cent. protein, the fractions of which have been determined by several authors (Cagianut and others, 1953 ; Stemmermann, 1952). The lens protein is built up by the capsular epithelium, which, because of its avascularity, must draw the constituent elements of protein synthesis from the aqueous alone. Neither the free nor the protein-bound amino acids of the aqueous humour have hitherto been determined by reliable methods. The reasons for this are, first, that the aqueous contains extremely small amounts of protein and free amino acids, and, second, that there is a very large concentration of inorganic ions in proportion to that of the amino acids. In this communication, the composition of the amino acids present in normal human aqueous fluid protein is reported.