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An enzymatic assay is described which quantitates radiolabeled type IV basement membrane collagen in the presence of large amounts of other proteins. A partially purified neutral protease is used which cleaves type IV collagen into fragments at 37°C which are not precipitated at 1.3% (final concentration) trichloroacetic acid-tannic acid. The kinetics of type IV collagen digestion by this enzyme are not significantly altered by the presence of a 10-fold excess of type III collagen. [14C]Tryptophan-labeled control proteins prepared from fibroblast cultures are not degraded significantly by this protease in the presence of 2.5 m m N-ethylmaleimide. The proportion of type IV collagen in a mixture of labeled placenta collagenous proteins was calculated after separate digestions with the type IV collagenolytic activity and bacterial collagenase: this value compared favorably with the proportion of type IV collagen estimated by gel electrophoresis.

A rapid and accurate reverse-phase high-performance liquid chromatography procedure for amino acid analysis of connective tissue proteins has been optimized. The method is based on quantitative dansyl chloride precolumn derivatization of protein hydrolyzates and chromatographic separation of the dansyl derivatives on Ultrasphere ODS C18 column. High molar uv absorption of Pro and Hyp derivatives, quantitation of low Des and Ide amounts (60 pmol), and good separation of all the amino acid derivatives (CV mostly less than 0.1%) including Hyl overcome the difficulties of other methods in producing reliable single run amino acid analysis of collagen and elastin. The use of fluorescence detector and the possibility of concentrating derivatized samples would give even higher sensitivity to the system. The procedure appeared to be suitable for single run analysis of other proteins, particularly those having an unbalanced amino acid composition.