Materials and Methods

Reagents. Carboxypeptidases A and B were obtained from Worthington Biochemicals, Freehold, NJ Urea (ultra pure) was purchased from Schwarz/Mann, Orangeburg, NY Methanesulfonic acid and dansyl chloride were purchased from Pierce Chemical Co., Rockford, 111. Hydrazine (95%+) was f From the Departments of Biochemistry and Medicine of the Albert Einstein College of Medicine, New York, New York 10461. Received April 27, 1976. Supported by Research Grants HL 02965 and HL 14236 from the National Institutes of Health, and Training Grant HL 5273 from the United States Public Health Service. 1 Abbreviations used are: HDL, high-density lipoprotein; LDL, low-density lipoprotein; VLDL, very low-density lipoprotein; CD, circular dichroism; ARP, arginine-rich protein; LMW, low molecular weight proteins of rat HDL; Glx, glutamic acid or glutamine; Asx, aspartic acid or asparagine; EDTA, ethylenediaminetetraacetic acid.