Determination of molecular weights by differential cryoscopy on small volumes of dilute solutions of oligopeptides

✍ Scribed by V.G. Davenport; E.R. Stimson; H.A. Scheraga

• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 747 KB
• Volume: 142
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(84)90483-4

✦ Synopsis

A differential cryoscope of the equilibrium type is described. It requires only 1 ml of sample for a molecular-weight determination of a solute in a solvent that freezes below room temperature. The instrument is sensitive to +0.0002°C, which corresponds to +O.OOOl mol of solute per 1000 g of water. The apparatus was evaluated by measuring the freezing point depressions of 0.015 M urea and 0.01 M alanine in water, the measured molecular weights being accurate to within +5%. The molecular weights of the following oligopeptides were then measured to determine their states of aggregation in the cited solvents: Ac-Asn-Pro-Tyr-NHMe in Hz0 and dimethyl sulfoxide and cyclo(L-alanyl-L-alanyl-t-aminocaproyl), cyclo(L-alanyl-rralanyl-c-aminocaproyl), cyclo(L-alanyl-L-analyl-wcapryl), cyclo(L-alanyl-D-alanyl-ocapryl), and Ac-Tyr-Pro-Asn-NHMe in dimethyl sulfoxide. o 1984 Academic press. hc.