Tritium–hydrogen exchange of poly-L-glutamic acid in aqueous solutions

✍ Scribed by Akira Ikegami; Sadaaki Yamamoto; Fumio Oosawa

• Publisher: Wiley (John Wiley & Sons)
• Year: 1965
• Tongue: English
• Weight: 562 KB
• Volume: 3
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1965.360030506

✦ Synopsis

To investigate the flexibility or motility of the secondary structure of poly-Lglutamic acid, a simple model molecule of proteins, the kinetics of the tritium-hydrogen exchange of this polymer in aqueous solutions waa followed at various pH values by use of a freezedrying technique and a liquid scintillation counter. The most essential point of the experimental results is that all of the protons (or isotopes) attached to peptidenitrogens were exchanged according to a simple first-order reaction and the rate was proportional to the fraction of random coil conformation determined by optical rotatory dispersion meaaurements. This means that the tritium attached to a peptide unit is exchangeable with a proton in water only when this unit is contained in the random coil structure and that the interchange of each unit between helical and random coil conformations takes place as a result of thermal fluctuation at very high frequency, although the average helical content of each molecule has a definite value.