CONFORMATION OF ANGIOTENSIN-2 IN AQUEOUS SOLUTION .2. DIALYSIS AND GEL FILTRATION BEHAVIOR OF [ASN1-VAL5]-ANGIOTENSIN-2

In a study of the kinetics of dialysis of [Asn1-Val5]-angiotensin II through cellophane membranes, at low ionic strength, it was possible to detect two components with different first-order rate constants of dialysis. The two components were present in approximately equal amounts in the pH range 2-9, but at pH 1.1 and 11.0 the component that dialyzed faster was present in a significantly lower proportion. At ionic strength 0.1 only the slow-dialyzing component was found in the pH range 1.1-11.0. A slow conversion from the fast-into the slow-dialyzing form was observed when the ionic strength of an aqueous solution of the peptide was raised to 0.1 by the addition of KCl. Chromatography on Sephadex G-25 columns also showed the presence of two components at low ionic strength. The effect of salt on the behavior of angiotensinamide toward Sephadex chromatography indicated that the component that dialyzed faster was more retained by Sephadex than the slower dialyzing one. These results are interpreted as evidence for the possibility of two conformations of angiotensin II in aqueous solutions. © 1969, American Chemical Society. All rights reserved.