1,3-Didodecylimidazolium salts have been prepared as first representatives of a new class of ionic liquid crystals (ILCs), showing thermotropic liquid crystalline behaviour in an extended temperature range below 70 degrees C. Remarkably strong non-Newtonian viscosity behaviour was found for the liquid-crystalline state of these ILCs.

Different types of cyclic phosphine oxides, such as tetrahydrophosphole oxide 1, phosphabicyclo[3.1.0]hexane 3oxide 8 and phosphabicyclo[2.2.1]heptene 7-oxides 10 and 12 were efficiently converted to phosphine-boranes 2, 9, 11 and 13, respectively, under relatively mild conditions by reaction with 4.4 equivalents of dimethyl sulfide-borane. The more strained hetero-ring the starting phosphine oxide (in general 16) has, the easier to accomplish the change in the P-function, that takes place through the corresponding phosphine intermediate ( 20). It is noteworthy that the imide carbonyl groups in starting materials 10 and 12 were fully reduced by the borane to give 11 and 13 respectively.

Watching phase transitions: Ordering processes and phase transitions in thin films of the liquid‐crystalline ionic liquid 1,3‐didodecylimidazolium tetrafluoroborate [C12C12IM][BF4] on Pt(111) (see picture) are studied by means of temperature‐dependent IR reflection absorption spectroscopy. The method allows in situ monitoring of the structural properties of liquid‐crystalline supported ionic liquid phase (SILP) catalysts under reaction conditions.

No abstract

No abstract

Objective Regio-and stereoselective hydroxylation of lithocholic acid (LCA) using CYP107D1 (OleP), a cytochrome P450 monooxygenase from the oleandomycin synthesis pathway of Streptomyces antibioticus. Results Co-expression of CYP107D1 from S. antibioticus and the reductase/ferredoxin system PdR/PdX from Pseudomonas putida was performed in Escherichia coli whole cells. In vivo hydroxylation of LCA exclusively yielded the 6b-OH product murideoxycholic acid (MDCA). In resting cells, 19.5% of LCA was converted to MDCA within 24 h, resulting in a space time yield of 0.04 mmol L-1 h-1. NMR spectroscopy confirmed the identity of MDCA as the sole product. Conclusions The multifunctional P450 monooxygenase CYP107D1 (OleP) can hydroxylate LCA, forming MDCA as the only product.

Xylitol is produced by the heterogeneous catalytic hydrogenation of xylose over Raney nickel. The hydrogenation must typically be followed by several purification steps, which makes the chemical production relatively complex and expensive. In this study, activated carbon and bio-purification treatments of corn stover hydrolysates and subsequent nickel-catalyzed hydrogenation of xylose to xylitol were investigated. The activated carbon treatment was used to eliminate inhibitory compounds and increase the efficiency of the bio-purification step. It was found that the glucose could be completely eliminated from the hydrolysate. The hydrogenation reactions of corn stover hydrolysate demonstrated that a high reaction temperature resulted in high sugar alcohol yields and selectivity. At a given temperature, the flow rate had no significant effect on xylitol yield. Figure 1. Hydrogenation of xylose to xylitol over Raney nickel.

Construction of the presynaptic filament (PSF) of proper helical structure by Rad51 recombinases is a prerequisite of the progress of homologous recombination repair. We studied the contribution of ATP-binding to this structure of wt human Rad51 (hRad51). We exploited the protein-dissociation effect of high hydrostatic pressure to determine the free energy of dissociation of the protomer interfaces in hRad51 oligomer states and used electron microscopy to obtain topological parameters. Without cofactors ATP and Ca(2+) and template DNA, hRad51 did not exist in monomer form, but it formed rodlike long filaments without helical order. ΔG(diss) indicated a strong inherent tendency of aggregation. Binding solely ssDNA left the filament unstructured with slightly increased ΔG(diss). Adding only ATP and Ca(2+) to the buffer disintegrated the self-associated rods into rings and short helices of further increased ΔG(diss). Rad51 binding to ssDNA only with ATP and Ca bound could lead to ordered helical filament formation of proper pitch size with interface contacts of K(d) ∼ 2 × 10(-11) M, indicating a structure of outstanding stability. ATP/Ca binding increased the ΔG(diss) of protomer contacts in the filament by 16 kJ/mol. The results emphasize that ATP-binding in the PSF of hRad51 has an essential, yet purely structural, role.