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Methyl Cyanide Induces α to β Transition and Aggregation at High Concentrations in E-State of Human Serum Albumin

P. Sen, M. A. Iqbal, S. Fatima, and R. H. Khan*

Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India; fax: +91-571-272-1776; E-mail: rizwanhkhan@hotmail.com; rizwanhkhan1@yahoo.com

* To whom correspondence should be addressed.

Received February 5, 2009; Revision received May 1, 2009
We have studied the effect of 2,2,2-trifluoroethanol (TFE), an α-helix inducer, versus methyl cyanide (MeCN), a β-sheet inducer, on acid-denatured human serum albumin (HSA) using far-UV circular dichroism, intrinsic fluorescence, 1-anilino-8-naphthalene sulfonate binding, and acrylamide quenching studies. Interestingly, at pH 2.0, where the recovery and resolution of the protein in reverse phase chromatography is high, its secondary structure remains unchanged even in the presence of very high concentration (76% v/v) of MeCN. Gain of 23 and 34% α-helicity was observed in the presence of 20 and 50% TFE, respectively. At pH 7.3, HSA aggregates in the presence of 40% MeCN, but it remains soluble up to 75% MeCN at pH 2.0. The results seem to be important for HSA isolation and purification.
KEY WORDS: acrylamide quenching, aggregation, circular dichroism, E-state, human serum albumin

DOI: 10.1134/S0006297910030132