Hen ovomucoid-agarose: A new conjugate for the isolation by affinity chromatography of UDP-galactose: Glycoprotein galactosyl-transferase

A new conjugate for the affinity chromatography of UDP-galactose:glycoprotein galactosyltransferase has been synthesized by coupling hen ovomucoid, a ligand similar to the acceptor substrate, to agarose. The hen ovomucoid-Sepharose conjugate binds galactosyl transferase more tightly that other acceptor-Sepharose conjugates. The new adsorbent gives comparable yields and purifications with those obtained by ligands similar to the nucleotide moiety of the substrate and to the “specifier” protein, α-lactalbumin. The soluble galactosyltransferase from rat ventral prostate is effectively removed from the high speed supernatant by an ovomucoid-Sepharose column. The enzyme can be eluted with buffer containing EDTA andN-acetylglucosamine in a high yield (75–80%) and in a purified form (4000-fold purification). The stability of ovomucoid to heat and to high concentrations of urea and its inhibition of some proteases makes the conjugate easy to operate with an quite useful even with rather crude preparations.     

Conformation of N,N′-bis (2,6-dimethylmorpholino), N″-dichloroacetyl phosphoric triamide: CHCl2C(O)NHP(O)[2,6(CH3)2(NC4H6O)]2. NMR and ab initio studies

Using phosphorus pentachloride as a substrate, a new carbacyclamidophosphate, N,N″-bis (2,6-dimethylmorpholino), N″-dichloroacetyl phosphoric triamide (1) has been synthesized and characterized by ¹H, ³¹P and ¹³C NMR, IR spectroscopy and elemental analysis. Due to the presence of methyl disubstituted morpholine rings and the dichloroacetamide group, several conformers can be considered for this molecule. The ³¹P{¹H} NMR spectra for the isomeric mixture of synthesized compound showed four signals with the ratio 67.1; 19.0; 12.2; 1.7, which indicates four independent conformers. The ¹H NMR spectra confirmed these results. The conformational space and the molecular geometry of the molecule in the gaseous phase have been studied using the B3LYP method of approximation, with 6-31G and 6-311++G^** basis sets.     

A band dispersion mechanism for Pt alloy compositional tuning of linear bound CO stretching frequencies

The C-O stretching frequency (nu(CO)) of atop CO/Pt in PtRu alloys is compositionally tuned in proportion to the Pt mole percent. The application of a Blyholder-Bagus type mechanism (i.e., increased back-donation from the metal d-band to the hybridized 2pi CO molecular orbitals (MOs)) to compositional tuning has been paradoxical because (1) a Pt-C bond contraction, expected with increased back-donation as the Pt mole percent is reduced, is not observed (i.e., calculated Pt-C bond is either elongated or insensitive to alloying and the binding energies of CO/Pt decrease with alloying) and (2) the lowering d-band center and increased d-band vacancies upon alloying (suggesting less back-donation to the higher energy metal hybridized 2pi CO MOs) must be reconciled with the alloy-induced red shift of the nu(CO). A library of spin-optimized Pt and Pt alloy clusters was the basis of density functional theory (DFT) calculations of CO binding energies, nu(CO) values, shifts, and broadening of 5sigma/2pi CO MO upon hybridization with the alloy orbitals and a DFT derived Mulliken electron population analysis. The DFT results, combined with FEFF8 local density of states (LDOS) calculations, validate a 5sigma donation-2pi back-donation mechanism, reconciling the direction of alloy compositional tuning with the lowering of the d-band center and increased vacancies. Although the d-band center decreases in energy with alloying, an asymmetric increase in the dispersion of the d-band is accompanied by an upshift of the metal cluster HOMO level. Concomitantly, the hybridization and renormalization of the CO 5sigma/2pi states results in a broadening of the 5sigma/2pi manifold with additional lower energy states closer to the upshifted (with respect to the pure Pt cluster) HOMO of the alloy cluster. The dispersion toward higher energies of the alloy d-density of states results in more 5sigma/2pi CO filled states (i.e., enhanced 2pi-back-donation). Finally, Mulliken and FEFF8 electron population analysis shows that the increase of the average d-band vacancies upon alloying and additional 2pi back-donation are not mutually exclusive. The d-electron density of the CO-adsorbed Pt atom increases with alloying while the average d-electron density throughout the cluster is reduced. The localized electron density is manifested as an electrostatic wall effect, preventing the Pt-C bond contractions expected with increased back-donation to the 2pi CO MOs.     

Dispersion properties of electromagnetically induced transparency under the Doppler broadening

The influence of heat motion of atoms in gaseous media on the features of manifestation of electromagnetically induced transparency is investigated. Taking into account elastic and inelastic collisions, fairly general and compact analytical relations are derived for the absorption and refraction coefficients of the probe wave in the presence of high-power inducing radiation, resonant to the adjacent atomic transition. It is shown, that occurrence of narrow resonance structures in the Doppler absorption and refraction profile is due to “overlap” of effective resonance velocities of atoms. The atomic level splitting in the strong wave field is uniformly analyzed in the entire intensity range. Interference transparency in a particular region of the Doppler profile is found to be accompanied by high resonance dispersion of the refraction coefficient, which is important for generating slow radiation and controlling its parameters. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 56–62, March, 2007.     

Structural and magnetic characterization of Co67Fe4Ni2Si15B12

 Soft magnetic properties of Co-based amorphous alloy of the composition Co₆₇Fe₄Ni₂Si₁₅B₁₂ have been investigated by isothermal heat treatment up to the conventional crystallization temperature. In the as-cast condition the Curie temperature of the sample is 272 °C and saturation magnetization is 74 emu/g. Magnetic properties undergo variation depending on the heat treatment temperature. For the heat treatment temperatures of around 420 and 490 °C, superior soft magnetic properties are obtained. For both the temperatures initial permeability, μ′ reaches value up to ten times the value of permeability in the as-received samples. Annealing effect on giant magneto-impedance has been observed for the current-driving frequencies of 4.5 and 6 MHz. Field dependence of magneto-impedance shows hysteresis at low field, which is related to the changes in the magnetization process of the sample.     

Crack path prediction in anisotropic brittle materials

A force balance condition to predict quasistatic crack paths in anisotropic brittle materials is derived from an analysis of diffuse interface continuum models that describe both short-scale failure and macroscopic linear elasticity. The path is uniquely determined by the directional anisotropy of the fracture energy, independent of details of the failure process. The derivation exploits the gradient dynamics and translation symmetry properties of this class of models to define a generalized energy-momentum tensor whose integral around an arbitrary closed path enclosing the crack tip yields all forces acting on this tip, including Eshelby's configurational forces, cohesive forces, and dissipative forces. Numerical simulations are in very good agreement with analytic predictions.     

Applications of Bruhat decompositions to complex hyperbolic geometry

The double coset space AΛ (n, ℂ) / U (n − 1, 1) is studied, where A consists of the diagonal matrices in GL (n, ℂ). This space naturally arises in the harmonic analysis on the hermitian symmetric space GL (n, ℂ) / U (n − 1, 1). It is shown here that these double cosets also represent a class of basic invariants related to complex hyperbolic geometry. An algebraic parametrization for the double cosets is given and it is shown how this may be used to conveniently compute the geometric invariants.     

Attachment of alkali cations on beta-D-glucopyranose: matrix-assisted laser desorption/ionization time-of-flight studies and ab initio calculations

In matrix-assisted laser desorption/ionization mass spectrometry, carbohydrates ionize by attachment of an alkali cation, and the ion yield varies with the nature of the cation. In an attempt to contribute to the understanding of the mechanisms involved, we have conducted matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) experiments on the simple glucose molecule with the alkali cations Li+, Na+ and K+, and have also performed ab initio calculations. The calculations show that, for the most stable carbohydrate-cation geometry, the carbohydrate ring is twisted and the cation is coordinated to four oxygen atoms. Calculations also show that in these complexes the positions of the three cations are very similar, and the smaller the cation, the closer it is to the oxygen atoms. Finally, the calculated formation enthalpies of the different complexes agree with the experimental results obtained for the order of stability of these complexes.