Role of Information Provision in Reversed-Phase High-Performance Liquid Chromatography (Exemplified by Impurity Identification in Dihydroquercetin)

It was noted that the common current practice of presenting the results of identifying organic compounds in reversed-phase HPLC with the specification of analytical parameters that do not exhibit interlaboratory reproducibility or without giving any data is inadequate. This approach is oriented only to the use of reference materials, and it actually implies that identification be performed anew in each particular case. The means of solving this general problem based on the use of retention indices and UV-spectroscopic invariants, such as relative absorbance, are exemplified by solving a particular problem of the identification of impurities in dihydroquercetin.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 8, 2005, pp. 837–841.Original Russian Text Copyright © 2005 by Zenkevich, Kosman.     

Potentialities of Quantitative Analysis by High-Performance Liquid Chromatography without Reference Standards of Analytes: Use of Reference Data on UV Spectra for Calculating Calibration Coefficients

It was shown by the examples of simple organic compounds and some medicinal substances that, in the quantitative analysis by the internal standard method in high-performance liquid chromatography (HPLC) with UV detection, one can use calibration coefficients calculated from reference data on UV spectra. Determinations should be performed at several constant wavelengths (for example, 220, 254, 280, and 320 nm) using at least two internal standards (a set of eight samples was proposed) rather than one standard. As can be judged from the estimates obtained, the systematic component of the determination error under these conditions does not exceed the contributions of random errors. The developed approach opens up new opportunities for quantitative determinations by HPLC without reference samples of analytes, instead of which reference data on molar absorptivities are used.     

Inverse perturbation analysis: Improving the accuracy of potential energy curves

The equation for the first-order energy correction is used inversely to find the perturbation responsible for the energy correction. In the specific application to the calculation of a potential energy curve from the spectroscopic term values, the sought perturbation is a correction to an approximate potential curve. Consequently, an approximate potential curve (e.g. an RKR (Rydberg-Klein-Rees) curve) can be improved until the eigenvalues calculated for this curve agree with the spectroscopic term values within the experimental uncertainty. Results are given for the X²Σ⁺ state of HgH.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.     

Separating sets by lower and upper semicontinuous functions with a closed graph

In this paper we characterize the pairs (A^?, A⁺) of disjoint subsets of perfectly normal topological space which can be separated by a lower and an upper semicontinuous function with a closed graph.     

Spectroscopic and kinetic studies of perturbed trinuclear copper clusters: the role of protons in reductive cleavage of the O-O bond in the multicopper oxidase Fet3p

The multicopper oxidase Fet3p couples four 1e(-) oxidations of substrate to the 4e(-) reduction of O2 to H2O. Fet3p uses four Cu atoms to accomplish this reaction: the type 1, type 2, and coupled binuclear type 3 sites. The type 2 and type 3 sites together form a trinuclear Cu cluster (TNC) which is the site of O2 reduction. This study focuses on mutants of two residues, E487 and D94, which lie in the second coordination sphere of the TNC and defines the role that each plays in the structural integrity of the TNC, its reactivity with O2, and in the directional movement of protons during reductive cleavage of the O-O bond. The E487D, E487A, and D94E mutants have been studied in the holo and type 1 depleted (T1D) forms. Residue E487, located near the T3 center, is found to be responsible for donation of a proton during the reductive cleavage of the O-O bond in the peroxide intermediate and an inverse kinetic solvent isotope effect, which indicates that this proton is already transferred when the O-O bond is cleaved. Residue D94, near the T2 site, plays a key role in the reaction of the reduced TNC with O2 and drives electron transfer from the T2 Cu to cleave the O-O bond by deprotonating the T2 Cu water ligand. A mechanism is developed where these second sphere residues participate in the proton assisted reductive cleavage of the O-O bond at the TNC.