The determination of hydroxyproline in tissue and protein samples containing small proportions of this imino acid

A method is presented for the quantitative determination of hydroxyproline in biological materials containing as little as one part of hydroxyproline in 4000 parts of amino acids. Thus method has been applied to a study of hydroxyproline distribution in cell particulates, tissue fluids, and purified plant and animal proteins. Significant amounts of hydroxyproline were found in crystalline preparations of pepsin, elastase. and ficin.