Chemo-enzymatic synthesis of 4-methylumbelliferyl beta-(1-->4)-D-xylooligosides: new substrates for beta-D-xylanase assays

Transglycosylation catalyzed by a beta-D-xylosidase from Aspergillus sp. was used to synthesize a set of 4-methylumbelliferyl (MU) beta-1-->4-D-xylooligosides having the common structure [beta-D-Xyl-(1-->4)]2-5-beta-D-Xyl-MU. MU xylobioside synthesized chemically by the condensation of protected MU beta-D-xylopyranoside with ethyl 2,3,4-tri-O-acetyl-1-thio-beta-D-xylopyranoside was used as a substrate for transglycosylation with the beta-D-xylosidase from Aspergillus sp. to produce higher MU xylooligosides. The structures of oligosaccharides obtained were established by 1H and 13C NMR spectroscopy and electrospray tandem mass spectrometry. MU beta-D-xylooligosides synthesized were tested as fluorogenic substrates for the GH-10 family beta-D-xylanase from Aspergillus orizae and the GH-11 family beta-D-xylanase I from Trichoderma reesei. Both xylanases released the aglycone from MU xylobioside and the corresponding trioside. With substrates having d.p. 4 and 5, the enzymes manifested endolytic activities, splitting off MU, MUX, and MUX2 primarily.     

A Simple and Convenient Synthesis of Glycosyl Azides

Treatment of glycosyl halides with NaN₃ in aqueous acetone or acetonitrile is a convenient method for the stereoselective synthesis of 1,2-trans-per-O-acetyl-glycosyl azides.     

Spin-reorientational phase transition in the basal plane in an α-Fe2O3: (Ga, Dy) crystal

A spin-reorientational phase transition in the basal plane, which was experimentally observed earlier, is explained in terms of a model in which the crystalline Fe-ion matrix is considered as a continuum, while dopant Dy ions are treated as quasi-Ising ions. The transition is established to be due to the Fe-subsystem anisotropy competing with that of the rare-earth subsystem.     

Electrohydrodynamic ion emitters

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 3–10, March–April, 1990.     

The Hilbert boundary-value problem with a finite index and a countable set of jump discontinuities in coefficients

We consider the Hilbert boundary-value problem with a finite index for the case, when the coefficients in the boundary condition have two infinite sequences of discontinuity points of the first kind. We obtain a formula for the general solution and study the solvability issues.     

The Hilbert problem: The case of infinitely many discontinuity points of coefficients

We obtain a solution to the Hilbert boundary value problem in the theory of analytic functions on the half-plane in the case that the coefficients of the boundary condition have countably many discontinuity points of the first kind. We elaborate the two substantially different situations: the series consisting of the jumps of the argument of the coefficient function and the increments of its continuous part converges and this series diverges. Accordingly, Hilbert problems with finite and infinite indices result. We derive formulas for the general solution and investigate the pictures of solvability of these problems.     

Recombinant formate dehydrogenase from <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>: Preparation,crystal growth in microgravity,and preliminary X-ray diffraction study

Crystals of high-purity recombinant NAD⁺-dependent formate dehydrogenase from the higher plant Arabidopsis thaliana (AraFDH) were grown in microgravity in the Modul’-1 protein crystallization apparatus on the International Space Station. The space-grown crystals have larger sizes than those grown on Earth. X-ray diffraction data suitable for determining the three-dimensional structure were collected from the space-grown crystals to a resolution of 1.22 Å using an X-ray synchrotron source. The crystals belong to sp. gr. P4₃2₁2; the unit-cell parameters are a = b = 107.865 Å, c = 71.180 Å, α = β = γ = 90°.     

Numerical simulation of the fine structure of domain walls in rare-earth orthoferrites

The structure of a solitary domain wall (DW) with a Bloch line in rare-earth orthoferrites is determined using numerical methods for the values of the material parameters lying beyond the range in which the can be found analytically solution. The law of rotation of the DW magnetization vector, the effective DW width, and the energy per unit length of the Bloch line are determined. It is shown that a more accurate treatment of the two-dimensional DW using numerical methods makes it possible to reveal essential distinctions in the fine structure of the DW in comparison to the approximate analytical solutions.