The electrochemical behavior of cytochrome c (cyt-c) adsorbed to gold electrodes through mercaptoalkanoic acid/ mercaptoalcohol monolayers was investigated in the 1-butyl-3-methylimidazolium salts of bis(trifluoromethylsulfonyl)imide and hexafluorophosphate. Cyt-c does not retain its Fe(III)/Fe(II) redox activity in dry ionic liquids (ILs); however, the redox signal of the modified electrodes can be reconstituted upon subsequent treatment with aqueous buffer. Water saturated ILs, 1.4 wt.%, failed to support the redox activity of the adsorbed cyt-c; therefore, the ILs' deleterious effects on the redox behavior of the cyt-c modified electrodes cannot be attributed solely to the stripping of essential water from the enzyme's polypeptide lattice. (C) 2003 Elsevier B.V. All rights reserved.