Glyoxylic Acid versus Ethyl Glyoxylate for the Aqueous Enantio­selective Synthesis of α-Hydroxy-γ-Keto Acids and Esters by the N-Tosyl-(S a)-binam-l-prolinamide-Organocatalyzed Aldol Reaction

N-Tosyl-(S a)-binam-l-prolinamide is an efficient catalyst for the aqueous aldol reaction between ketones and glyoxylic acid, as the monohydrate or as an aqueous solution, or a 50% toluene solution of ethyl glyoxylate. These reactions led to the formation of chiral α-hydroxy-γ-keto carboxylic acids and esters in high levels of diastereo- and enantioselectivities (up to 97% ee), providing mainly anti aldol products. Only cyclopentanone and cyclohexane-1,4-dione afforded an almost 1:1 mixture of the syn/anti-diastereoisomers; however, the reaction between 4-phenylcyclohexanone and ethyl glyoxylate gave the corresponding syn,syn-product as the major diastereoisomer.

Palladium nanoparticles supported on graphene and reduced graphene oxide as efficient recyclable catalyst for the Suzuki–Miyaura reaction of potassium aryltrifluoroborates

Palladium nanoparticles supported on graphene platelets have been efficiently used as catalyst in the Suzuki–Miyaura coupling between aryl bromides and potassium aryltrifluoroborates using 0.1 mol% of Pd and potassium carbonate as base in MeOH/H2O as solvent at 80 °C. The reaction can be performed using conventional and microwave heating showing the catalyst high reusability, particularly with microwaves, where lower aggregation of Pd nanoparticles has been observed. A dissolution/re-deposition catalytic mechanism is proposed, based on the fact that palladium leaching to the solution is detected under microwave irradiation.

Binap-silver-catalyzed enantioselective multicomponent 1,3-dipolar cycloaddition of azomethines ylides derived from ethyl glyoxylate

The enantioselective binap–silver catalyzed multicomponent 1,3-dipolar cycloaddition using ethyl glyoxylate, phenylalanine ethyl ester, and maleimides is described. The employment of basic silver carbonate allows the reaction to take place in the absence of an extra base giving high yields and ee. In addition, low-level calculations regarding the importance of the benzyl substituent at the α-position of the amino ester justify the expected absolute configuration of the final cycloadducts and the observed high enantiodiscrimination.

Competing Lipid-Protein and Protein-Protein Interactions Determine Clustering and Gating Patterns in the Potassium Channel from Streptomyces lividans (KcsA)

There is increasing evidence to support the notion that membrane proteins, instead of being isolated components floating in a fluid lipid environment, can be assembled into supramolecular complexes that take part in a variety of cooperative cellular functions. The interplay between lipid-protein and protein-protein interactions is expected to be a determinant factor in the assembly and dynamics of such membrane complexes. Here we report on a role of anionic phospholipids in determining the extent of clustering of KcsA, a model potassium channel. Assembly/disassembly of channel clusters occurs, at least partly, as a consequence of competing lipid-protein and protein-protein interactions at nonannular lipid binding sites on the channel surface and brings about profound changes in the gating properties of the channel. Our results suggest that these latter effects of anionic lipids are mediated via the Trp67–Glu71–Asp80 inactivation triad within the channel structure and its bearing on the selectivity filter.

The Trk Potassium Transporter Is Required for RsmB-Mediated Activation of Virulence in the Phytopathogen Pectobacterium wasabiae

Pectobacterium wasabiae (previously known as Erwinia carotovora) is an important plant pathogen that regulates the production of plant cell wall-degrading enzymes through an N-acyl homoserine lactone-based quorum sensing system and through the GacS/GacA two-component system (also known as ExpS/ExpA). At high cell density, activation of GacS/GacA induces the expression of RsmB, a noncoding RNA that is essential for the activation of virulence in this bacterium. A genetic screen to identify regulators of RsmB revealed that mutants defective in components of a putative Trk potassium transporter (trkH and trkA) had decreased rsmB expression. Further analysis of these mutants showed that changes in potassium concentration influenced rsmB expression and consequent tissue damage in potato tubers and that this regulation required an intact Trk system. Regulation of rsmB expression by potassium via the Trk system occurred even in the absence of the GacS/GacA system, demonstrating that these systems act independently and are both required for full activation of RsmB and for the downstream induction of virulence in potato infection assays. Overall, our results identified potassium as an essential environmental factor regulating the Rsm system, and the consequent induction of virulence, in the plant pathogen P. wasabiae.

Application of phosphatidylethanol (PEth) in whole blood in comparison to ethyl glucuronide in hair (hEtG) in driving aptitude assessment (DAA)

For driving aptitude assessment (DAA), the analysis of several alcohol biomarkers is essential for the detection of alcohol intake besides psycho-medical exploration. In Switzerland, EtG in hair (hEtG) is often the only direct marker for abstinence monitoring in DAA. Therefore, the suitability of phosphatidylethanol (PEth) was investigated as additional biomarker. PEth 16:0/18:1 and 16:0/18:2 were determined by online-SPE-LC-MS/MS in 136 blood samples of persons undergoing DAA and compared to hEtG, determined in hair segments taken at the same time. With a PEth 16:0/18:1 threshold of 210 ng/mL for excessive alcohol consumption, all (n = 30) but one tested person also had hEtG values ≥30 pg/mg. In 54 cases, results are not in contradiction to an abstinence as neither PEth (<20 ng/mL) nor hEtG (<7 pg/mg) was detected. In eight cases, both markers showed moderate consumption. Altogether, PEth and hEtG were in accordance in 68 % of the samples, although covering different time periods of alcohol consumption. With receiver operating characteristic analysis, PEth was evaluated to differentiate abstinence, moderate, and excessive alcohol consumption in accordance with hEtG limits. A PEth 16:0/18:1 threshold of 150 ng/mL resulted in the best sensitivity (70.6 %) and specificity (98.8 %) for excessive consumption. Values between 20 and 150 ng/mL passed for moderate consumption, values <20 ng/mL passed for abstinence. As PEth mostly has a shorter detection window (2-4 weeks) than hEtG (up to 6 months depending on hair length), changes in drinking behavior can be detected earlier by PEth than by hEtG analysis alone. Therefore, PEth helps to improve the diagnostic information and is a valuable additional alcohol marker for DAA.