Schur multiplicators of infinite pro-<Emphasis Type="Italic">p</Emphasis>-groups with finite coclass

Let G be an infinite pro-p-group of finite coclass and let M(G) be its Schur multiplicator. For p > 2, we determine the isomorphism type of Hom(M(G), ℤ_p), where ℤ_p denotes the p-adic integers, and show that M(G) is infinite. For p = 2, we investigate the Schur multiplicators of the infinite pro-2-groups of small coclass and show that M(G) can be infinite, finite or even trivial.     

Energising the E-factor: The E+-factor

The E-factor has become an important measure for the environmental impact of (bio)chemical reactions. However, summing up the obvious wastes generated in the laboratory neglects energy-related wastes (mostly greenhouse gases) which are generated elsewhere. To estimate these wastes, we propose to extend the E-factor by an energy-term (E⁺-factor). At the example of a lab-scale enzyme fermentation, we demonstrate that the E⁺-factor can constitute a multiple of the classical E-factor and therefore must not be neglected striving for a holistic estimation of the environmental impact.     

Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity

Water-soluble block copolymers were prepared from the nonionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermoresponsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0 and 100 degrees C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates which switch reversibly can be prepared in water, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus.     

Stereochemistry of the transmetalation of Grignard reagents to copper (I) and manganese (II)

Transmetalation of a chiral secondary Grignard reagent to Cu(I) or Mn(II) occurs with partial racemization in a manner that suggests the sequence of two transmetalation cycles, one with racemization (caused by ET ?) and the other one with (predominant) retention of configuration.     

Development of a donor-acceptor concept for enzymatic cross-coupling reactions of aldehydes: the first asymmetric cross-benzoin condensation

Highly enantioenriched mixed benzoins are obtained selectively through a biocatalytical cross-coupling reaction of aromatic aldehydes using ThDP-dependent enzymes.     

Efficient synthesis of benzopyrano[2,3-b]pyridines by sequential reactions of 1,3-bis-silyl enol ethers with 3-cyanobenzopyrylium triflates

Benzopyrano[2,3-b]pyridines were efficiently prepared by condensation of 1,3-bis-silyl enol ethers with 3-cyanobenzopyrylium triflates and subsequent domino ‘retro-Michael-lactonization-aldol’ reactions.     

In Rhodobacter sphaeroides respiratory nitrate reductase, the kinetics of substrate binding favors intramolecular electron transfer

The respiratory nitrate reductase (NapAB) from Rb. sphaeroides is a periplasmic molybdenum-containing enzyme which belongs to the DMSO reductase family. We report a study of NapAB by protein film voltammetry (PFV), and we present the first quantitative interpretation of the complex redox-state dependence of activity that has also been observed with other related enzymes. The model we use to fit the data assumes that binding of substrate partly limits turnover and is faster and weaker when the Mo ion is in the V oxidation state than when it is fully reduced. We explain how the presence in the catalytic cycle of such slow chemical steps coupled to electron transfer to the active site decreases the driving force required to reduce the MoV ion and makes exergonic the last intramolecular electron-transfer step (between the proximal cubane and the Mo cofactor). Importantly, comparison is made with all Mo enzymes for which PFV data are available, and we emphasize general features of the energetics of the catalytic cycles in enzymes of the DMSO reductase family.