1H‐NMR assignment and folding of the isolated ribonuclease 21–42 fragment

Abstract

We show in this paper that the isolated bovine ribonuclease 21–42 fragment is able to adopt in water solution a measurable population (14% at 22°C, pH 5.4) of a native‐like α‐helical structure. Strong support for this conclusion is given by the analysis of CD data and 1H chemical shift variations with the temperature and the addition of stabilizing (trifluoroethanol) and denaturing (urea) agents. This result gives experimental support to the idea that native isolated secondary structure elements (at least α helices) are, as a rule, partially stable in solution and therefore they can act as independent protein‐folding nucleation centers. Copyright © 1988, Wiley Blackwell. All rights reserved