Morphology of struvite crystals as an evidence of bacteria mediated growth

Influence of Proteus mirabilis on the growth, morphology and size of struvite crystals in artificial urine has been studied. The growth in the presence of Proteus mirabilis shows formation of struvite crystals of more regular habits compared with that in the absence of bacteria. This implies that in the presence of Proteus mirabilis, struvite crystals grow with relative growth rates within smaller range of variability compared to the absence of bacteria. The results show that bacteria affect size and struvite morphology while the habit remains almost unchanged. It is suggested that the changes in struvite crystal morphology are induced by the presence of Proteus mirabilis. Microorganism's negatively charged residues interact electrostatically with positive ions which outcrop given surfaces and lead to an enhanced expression of these surfaces. This means that microorganisms actively mediate in growth processes. Therefore, the investigations provide evidence for the importance of biological regulation in crystallization process.     

Electrooxidation of tigogenin acetate

Electrooxidation of tigogenin acetate afforded two products: 3β-acetoxy-16β-hydroxy-23,24-dinor-5α-cholanoic acid lactone (2) and 20-epitigogenin acetate (3). The structure of the latter compound was confirmed by an X-ray analysis. The tentative mechanism of reaction is proposed.     

Synthesis of (−)‐Isofagomine

Abstract

1,3‐Dipolar cycloaddition of N‐benzyl nitrone 2 to D‐threo δ‐lactone 15 proceeded with excellent stereoselectivity to provide only one adduct 16. Cycloadduct 16 was subsequently subjected to a sequence of reactions involving rearrangement to γ‐lactone, glycolic cleavage/reduction, protection of the terminal hydroxymethyl group, reduction of the lactone, desilylation/mesylation, and hydrogenolysis of the N‐O bond providing (?)‐isofagomine and its N‐substituted derivatives. The biologic activity of N‐substituted (?)‐isofagomines toward commercially available α‐ and β‐glucosidases, α‐D‐mannosidase, α‐L‐fucosidase, β‐D‐glucuronidase, and β‐D‐galactosidase was tested.     

Electrochemical synthesis of glycoconjugates of 3β-hydroxy-Δ-steroids by using non-activated sugars and steroidal thioethers

A new protocol for the electrochemical synthesis of glycoconjugates is presented. Thioether derivatives of cholesterol and other sterols were subjected to anodic oxidation in the presence of a sugar alcohol affording glycoconjugates with the sugar linked to a steroid moiety by an ether bond. The isomeric 6β-3α,5α-cyclo-steroidal thioethers proved to be better sterol donors than the normal 3β-Δ⁵-steroidal thioethers.     

Photochemistry of 6-azidopurine ribonucleoside in aqueous solution

In aqueous solution, 6-azido-9-β-d-ribofuranosylpurine undergoes an efficient photoinduced purine ring expansion to give a novel imidazole-fused 1,3,5-triazepinone nucleoside and partial conversion into adenosine. The structure of the major product was established as 1-(β-d-ribofuranosyl)-4,6-dihydroimidazo[4,5-f][1,3,5]triazepin-5(1H)-one based on HRMS and NMR spectral data.     

Noncommutative Mackey functors and Hopf-cyclic Homology

We show that a duality of the Hopf-cyclic homology and cohomology can be explained in terms of functors defined on a PROP for Hopf algebras.     

Selection of a method for determination of activity of pectinolytic enzymes in berry fruit materials

The goal of the study was to find the most accurate and sensitive method for the determination of activity of pectinolytic enzymes in complex mixtures obtained from fruit materials such as raw cloudberry and raspberry juices. Several assay methods based on enzymatic reactions using viscometric, colourimetric, spectrophotometric, or pH-titration detection of the reaction products were tested. Problems with the application of the selected methods, such as very low detection signal or very large background signal, were observed. Among the tested methods, only a modified method based on the continuous recording of the released carboxyl groups titration allowed to assay the activity of exogenous pectin methylesterase with a good linearity, sensitivity, accuracy, and minimised the interference of other fruit components.