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A nonspectroscopic chemical method is employed to determine the binding site on horse cytochrome involved in its adsorptive immobilization on a COOH-terminated self-assembled monolayer (SAM). The factors that can complicate or distort data interpretation and the generality of differential modification relative to existing in situ methods for protein orientation determination are discussed.

Research has been conducted on the kynurenine pathway catabolites. The reaction of these catabolites with iron and copper and interactions with alpha-crystallins have been investigated.

A review of literature of dynamic electrochemistry incorporates publications from Nov. 1, 1993 to Oct. 31, 1995 with a lag in-between. Only literature directed on the developments in electrochemistry are included with emphasis on the application of electroanalytical chemistry. The relevant subjects are enzyme electrodes, voltammetric analysis, microelectrodes, and instrumentation. Surface electrochemistry, redox polymers and other essential electrochemical issues are also accounted for.

A theoretical analysis suggests a relationship between an observed reaction rate constant and a differential rate constant, which is related to the Marcus theory of electron transfer. Consequently, assumptions from the Marcus theory are used to derive an expression for the current as a function of overpotential during linear-sweep voltammetry in the case of kinetically irreversible electron transfer between an electrode and a surface-confined redox species. A method for the extraction of kinetic parameters from experimental current vs potential data is also described. The application of this procedure is demonstrated in the electron transfer between gold electrodes and strongly adsorbed cytochrome c through a self-assembled alkanethiolate monolayer.

A review of significant developments in electroanalytical chemistry during Dec. 1991-Nov. 1993 is presented. The papers reviewed dealt with several topics such as ultramicroelectrodes, analytical voltammetry, electrode kinetics, surface electrode phenomena, modified electrodes, instrumentation, bioelectrochemistry, spectroelectrochemistry and characterization of redox reactions.

Cytochrome c peroxidase (CCP) adsorbed at (sub)monolayer surface coverage on edge-oriented pyrolytic graphite (EPG) is being used as a model system for determining the effects of immobilization on the kinetic properties of an enzyme and for developing molecular insight into enzymatic electrocatalysis. Evidence indicating that the catalytic reduction of [H.sub.2][O.sub.2] at the CCP/EPG electrode occurs via the intact enzyme and not via some form of 'free' heme is discussed. Rotating disk electrode (RDE) voltammetry has been used to determine a Michaelis constant of 48 [mu]M and a minimum turnover number of [110s.sup.-1] for the adsorbed enzyme at 3 [degrees]C. Adsorbed CCP was found to exhibit the same trend with regard to inhibition by anions as does solution CCP, i.e., CN-> F-> N3->> CI-. From these and previous results, we conclude that the catalytic function of CCP remains essentially intact when strongly adsorbed on EPG.

A study was done on reductive detoxification as a mechanism of fungal resistance to singlet oxygen-generating photosensitizers. It was shown that Cercospora species protect themselves against cercosporin by a reversible reduction and detoxification of the toxin molecule. In addition, it was shown that the photosensitizer reduction may be a generalized mechanism of resistance for the organisms to other oxygen-generating photosensitizers.

Tin oxide electrodes with an adsorbed cytochrome c monolayer were examined using ultraviolet-visible spectroscopy. The structural state and the distribution of the compound on the surface were readily observed without the need for complex procedures. The position and intensities of the ultraviolet spectra provided the information regarding the conformation and total surface coverage of the cytochrome c monolayer. In addition, ferricytochrome c remained intact after its adsorption on the electrode's surface even in the presence of applied potentials reaching 0.7 volts.

The recombinant expression and purification of dehaloperoxidase (DHP) B from Amphitrite orbata is described along with the analysis of catalytic cycle. A novel reaction pathway is demonstrated in which the products of the oxidative dehalogenation of trihalophenols are themselves capable of inducing formation of oxyferrous DHP B and an updated catalytic cycle for DHP is described.

A modification in the structure of the self-assembled monolayer can increase interfacial electron-transfer (ET) rates of cytochromes c, with those of yeast species at dramatic levels. It is shown that increases in ET rate for yeast cyt c are possible when mixed COOHN/OH SAMs are substituted for COOH SAMs of comparable thickness. These EDT rate increases are said to result from enhanced electronic coupling at the yeast cyt c/SAM interface.

The acidity (pKa) of monolayers made up of 11-mercaptoundecanoic acid self-assembled on vapor-deposited gold film electrodes in contact with either 0.10 or 1.0 M ionic strength NaClO4 electrolyte solutions have been measured through indirect laser-induced temperature jump method. The pKa is defined as the value of the pH of the solution in contact with the monolayer when half of the acid functional groups have been ionized. Results indicated that pKa has a value of 5.7 +/- 0.2 at O.10 M ionic strength and 4.4 +/- 0.2 at 1.0 M ionic strength.