Mannanase Transfer into Hexane and Xylene by Liquid–Liquid Extraction

The formation of noncovalent complexes between glycosidase, endo-1,4-β-d-mannanase, and ionic surfactant di(2-ethylhexyl) sodium sulfosuccinate (AOT) was shown to promote protein transfer into organic solvents such as xylene and hexane. It was found that mannanase can be solubilized in hexane and in xylene with concentration at least 2.5 and 2.0 mg/ml, respectively. The catalytic activity of the enzyme in hexane spontaneously increases with the concentration of AOT and is about 10% of the activity in aqueous system. In xylene, a catalytic activity higher than that in bulk aqueous conditions was found for the samples containing 0.1–0.3 mg/ml of mannanase, while for the samples with a higher concentration of enzyme, the activity was hardly detected.     

Prototropic behavior of cyclohexane substituted urethane and urea compounds. Observation of H-bond mediated 4HJH1H3 coupling constants across urea fragments

Two 1-aryl-3-cyclohexylurea and two 1-aryl-3-cyclohexylurethane with and without alkyl tail in aryl fragments were synthesized and their variable-temperature ¹H NMR spectra in chloroform, DMSO and DMF were recorded. The temperature dependences of chemical shift of NH protons for all compounds have been observed. The type of dependence has been explained by the aggregation of molecules and formation of ionic structures. The formation of intermolecular complexes leads to possible formation of symmetrical N1 ^{… …} H ^……N3 intramolecular hydrogen bond in urea fragment. As a result,^4hJ_H1H3 trans-hydrogen bond scalar coupling constants have been observed for the first time in low molecular weight compounds using a simple one-dimensional ¹H NMR experiment. The formation of strong intramolecular H-bond leads to π-conjugation not only with spacer but with phenyl ring too. It support the Gilli conception that RAHB formation is a result of π-electron delocalization. The presence in urea fragment of such kind interaction leads to formation of ionic structure, which has been detected by NMR and UV spectroscopies. The formation of ionic structure can explain the catalytic activity of such compounds and the mechanism of transformation in organic and bioorganic reactions in which involved the urea compounds.     

Selective labeling of polypeptides using protein farnesyltransferase via rapid oxime ligation

An aldehyde-containing alternative substrate for protein farnesyltransferase was prepared and shown to be enzymatically incorporated into a peptide and a protein. The protein was subsequently immobilized onto aminooxy-functionalized agarose beads or labeled with a fluorophore. This method for protein modification provides an alternative to the commonly employed Cu(I)-catalyzed click reaction.     

Decreasing and fast solutions for a second-order difference equation related to Fisher-Kolmogorov's equation

We prove the existence of so-called fast solutions of a second-order difference equation related to traveling wave solutions of Fisher-Kolmogorov's equation. Variational approach is used and the fast solutions are obtained as minimizers of an energy functional on a weighted Hilbert space. Numerical experiments are presented.     

Anisotropy of Atomic Van der Waals Radii in the Gas-Phase and Condensed Molecules\sp{1}

The anisotropic components of van der Waals radii for 5b, 6b and 7b Group elements were determined from the structures of gaseous van der Waals complexes and of crystalline molecular solids. The transition from the gaseous to the solid state reduces the anisotropy of a van der Waals atomic shape. This anisotropy is largely responsible for the changes of intermolecular distances, which are often misinterpreted as an effect of hydrogen bonds.     

Periodic and homoclinic solutions of some semilinear sixth-order differential equations

In this paper we study the existence of periodic solutions of the sixth-order equation

uvi+Auiv+Bu″+u−u3=0,