Light-scattering and potentiometric-titration studies of poly-L-tyrosine in aqueous solution

✍ Scribed by Marilyn B. Senior; Sandra L. H. Gorrell; Eugene Hamori

• Publisher: Wiley (John Wiley & Sons)
• Year: 1971
• Tongue: English
• Weight: 928 KB
• Volume: 10
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360101204

✦ Synopsis

Synopsis

Aqiieoris solritions of poly-1,-tyrosine were studied by potentiometric titrations, lightsrat,teririg measrirements, and infrared spectroscopy in order to characterize the conformational changes the macromolecules exhibit when the hydrogen-ion concentration of the solutions is varied. It was found that when the pH of the system a t 25OC is lowered from a value of about 13 the poly-L-tyrosine molecules undergo a random-coil to 8-structrire coxformatioil change a t pTI ll..?. It appears, that iuider the experimental conditions used, the formatioil of the p structure is an iiit ramolecular process which involves the folding of the polymer backbone into several hairpins of antiparallel 6 structure. On frirther lowering of the plf of the solutions aggregatioii (pII ll.B3) arid subsequently precipitation (pH 11.2) takes place. Since the apparent pK of the polymer does not show a drastic change dririiig the r:tndom-coil to p-strlict,lire conformation change, it was concluded, that the thermodynamic driving force for this conformation change is mainly due to the electrostatic effect of the partidly charged side chains of the poly-L-tyrosine molecriles.