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A proline-rich polypeptide isolated from sheep colostrum is described. The molecular weight of the polypeptide determined by gel filtration is 17 200. However, in the presence of guanidinium chloride the molecular weight found is about 6000. The polypeptide contains about 22% of proline, a high proportion of non-polar amino acids, a low percentage of glycine, and no alanine, arginine and cysteine residues. The only N-terminal amino acid found is leucine. C.d. spectra in water and in 50% (v/v) trifluoroethanol suggest the presence of block sequences of proline residues forming helices of polyproline II type. The proline-rich polypeptide is soluble at 4 degrees C but is reversibly precipitated on warming to room temperature. Maximal precipitation is observed at pH 4.6 and at ionic strength above 0.6. The precipitation depends on the concentration of the polypeptide. No effect of other proteins, Ca2+ and Zn2+ ions on the precipitation of the polypeptide was found. The proline-rich polypeptide is not an amphipathic protein. The lack of effect of the polypeptide on proteolytic enzymes ruled out the possibility that it is an inhibitor of proteinases.

The present study was designed to estimate the ability of chlorophyllin (CHL) to interact with two acridine mutagens, quinacrine mustard (QM) and acridine orange (AO), and with the antitumor anthracycline doxorubicin (Dox). To this end, aqueous solutions of QM, AO or Dox during titration with CHL were subjected to spectrophotometry and spectrofluorimetry to detect possible interactions between these reagents. The data indicate that CHL forms complexes with AO, QM or Dox in these solutions. The presence of the complexes was manifested by a bathochromic shift of the absorption spectra, as well as by strong quenching of the fluorescence of each of these mutagens in the presence of CHL. CHL, thus, may serve as an interceptor of these mutagenic acridines in different in vivo or in vitro applications. Its ability to interact with Dox may potentially be utilized to detoxify patients overdosed with this or similar drugs.

In aqueous solutions, in the presence of double-stranded DNA, chlorophyllin (CHL) forms complexes with each of the three DNA intercalators: acridine orange (AO), quinacrine mustard (QM), and doxorubicin (DOX). The evidence for these interactions was obtained by measurement changes in the absorption and fluorescence spectra of the mixtures containing DNA and intercalators during titration with CHL. A model of simple competition between DNA and CHL for the intercalator was used to define the measured interactions. The concentrations of the complexes estimated based on this model were consistent with the concentrations obtained by actual measurement of the absorption spectra.The present data provide further support for the role of chlorophyllin as an "interceptor" that may neutralize biological activity of aromatic compounds including mutagens and antitumor drugs.