Ultraviolet-B-Induced Damage to Escherichia coli Fpg Protein

We investigated the effect of UVB light (290 < or = lambda < or = 320 nm) on the structure and enzymatic activities of Escherichia coli Fpg protein (2,6-diamino-4-hydroxy-5N-methylformamidopyrimidine-DNA glycosylase), a DNA repair enzyme containing a zinc finger motif and five chromophoric Trp residues. Irradiation with UVB light of air-saturated pH 7.4 buffered aqueous solutions of Fpg induces the formation of polymers as shown by sodium dodecyl sulfate polyacrylamide gel electrophoretic analysis. In argon-saturated solutions, polymer formation produces a precipitate. The polymerization quantum yield is 0.07 +/- 0.01 and 0.15 +/- 0.02 in air- and argon-saturated solutions, respectively. In the polymerized Fpg protein, second-derivative absorption spectroscopy indicates that three and one Trp residues are destroyed in air- and argon-saturated solutions, respectively. Polymers are devoid of all three activities of the Fpg protein, whereas the unpolymerized protein retains full activities. Matrix-assisted laser desorption/ionization experiments demonstrate that polymer formation is accompanied by the formation of short polypeptides containing the first 32 or 33 residues of the N-terminal domain. Theses polypeptides are most probably formed by the photolytic cleavage of Fpg protein induced by light absorption by the adjacent Trp-34 residue.     

Elastica of an euler rod with clamped ends

The stability of the postcritical states of equilibrium of a flexible rod with clamped ends loaded by an axial force is analyzed. It is shown that the existing Lagrange elliptic-integral solution has bifurcation points and branches of solution that have not been investigated thus far. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 3, pp. 184–186, May–June, 2000.     

40 years since the discovery of the arsenazo III reagent

The review was devoted to progress in the application of the well-known and widely used reagent Arsenazo III in analytical chemistry. Arsenazo III 2,7-bis[(2-arsonophenyl)azo]-1,8-dihydroxy-3,6-naphthalenedisulfonic acid was synthesized by S.B. Savvin in 1959     

Potential-Barrier Profile for the Adiabatic Electron Transfer Reaction in the Condon Approximation

An effective reaction coordinate is introduced and a self-consistent algorithm is proposed for the calculation of the potential barrier profile of the adiabatic electron transfer reaction in a polar solvent, taking into account electron wave functions of reagents with respect to the media polarization. A change in the functions when moving along the reaction coordinate reduces significantly the activation barrier and increases the reaction rate.     

Effects of Electron Correlations in a Simple Model for Adiabatic Electrochemical Reactions: The Diagram of Kinetic Regimes

In the framework of the surface-molecule model for adiabatic electrochemical reactions of electron transfer previously suggested by the authors, a diagram of kinetic regimes (DKM) in the space of model parameters is obtained. The diagram comprises critical regions that correspond to various feasible electron transfer processes (transfer of one electron, simultaneous transfer of two electrons, transfer of two electrons in the presence of an intermediate state) and a region corresponding to electroadsorption of the reagent in certain charge states. Analytical expressions for boundary curves of DKM are obtained for a number of simple cases. A DKM for the general case of the surface-molecule model with an exact allowance for electron–electron correlations is constructed and analyzed.     

Method for the calculation of the species balance in the reaction zone

A class of processes for which the problem of species balance can be solved without using any assumptions concerning the mechanism of the chemical event of the reaction was found in the problem of species balance in the reaction zone. The mathematical statement of the problem in this case was discussed; it was shown that the solution is mainly determined by the system geometry. The method for reducing the problem to determination of the probability of species entering the chemical event zone is substantiated; this can be done by the Green function method.     

Reaction of 4,4-Dimethyl-1,3-dioxane with Dinitriles

The reaction of 4,4-dimethyl-1,3-dioxane with bis(2-cyano)diethyl ether or 1,2-di(beta-cyanoethoxy)ethane yields the corresponding bis[2-(4,4-dimethyl-5,6-dihydro-2-oxazinyl)]diethyl ether and 1,2-di{beta-[2-(4,4-dimethyl-5,6-dihydro-2-oxazinyl)]ethoxy}ethane which are readily hydrolyzed under the action of aqueous alkali to give 3-methyl-3-amino-1-butanol.     

Reaction of 1,5-Diphenyl-1,4-pentadien-3-one and 1,5-Diphenyl- 1-penten-4-yn-3-one with Monosubstituted Hydrazines

Phenyl- and isopropylhydrazines react with 1,5-diphenyl-1,4-pentadien-3-one to give 4,5,6,7-tetrahydroindazole derivatives instead of the expected 4,5-dihydropyrazoles. The reaction of phenylhydrazine with 1,5-diphenyl-1-penten-4-yn-3-one leads to formation of 1,5-diphenyl-3-phenylethynyl-4,5-dihydropyrazole. 2,4-Dinitrophenylhydrazine reacts with 1,5-diphenyl-1-penten-4-yn-3-one, affording the corresponding unsaturated hydrazone rather than pyrazole derivative.