Multitechnique investigation of conformational features of small molecules: the case of methyl phenyl sulfoxide

The conformational distribution of methyl phenyl sulfoxide (a molecule representative of a very important class of reagents widely used in asymmetric synthesis) has been studied in two different phases of matter (gas phase and solution) by a comprehensive approach including theoretical calculations, microwave spectroscopy, liquid crystal NMR experiments, and atomistic molecular dynamics computer simulations. The aim was to investigate the combined action of intra- and intermolecular interactions in determining the molecule's conformational equilibrium, upon which important physicochemical properties (inter alia, the chemoselectivity) significantly depend. Basically, the results converge in describing the tendency of the molecule to favor stable conformations governed by intramolecular interactions (in particular, the expected optimization between steric repulsion and conjugation of pi systems). However, significant solvent effects (whose "absolute" magnitude is actually difficult to assess, due to a certain "method-dependence" of the results) have been also detected.     

Protein extraction from Phoenix dactylifera L. leaves, a recalcitrant material, for two-dimensional electrophoresis

This work was aimed at optimizing a protein extraction procedure for date palm (Phoenix dactylifera L.) leaves, a highly recalcitrant plant tissue for 2-DE. Five protein extraction protocols based on different protein precipitation agents (TCA/acetone vs. phenol (Ph) methods) and protein resolubilization methods (physical treatments, e.g., sonication, shaking and/or heating) were tested. Ph/SDS extraction with methanol/ammonium acetate precipitation, followed by DOC preincubation and TCA/acetone precipitation and, finally, solubilization by shaking in rehydration solution was found to be the best protein extraction method. We conclude that DOC with TCA/acetone precipitation step eliminates interfering compounds, thus allowing efficient resolubilization of date palm leaf proteins. This method could be appropriate for proteomic studies such as date palm colonization by entomopathogenic fungi.     

Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008)

IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem. 73, 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the (1)H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a part per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating (13)C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids are reviewed in some detail, and recommendations are given for best practice.     

Block copolymer-mediated synthesis of size-tunable gold nanospheres and nanoplates

We have successfully controlled the size and shape of isotropic and anisotropic gold nanocrystals through a one-step reaction by using amphiphilic polyethylene oxide-polystyrene oxide block copolymers as both reductant and stabilizing agents in water solution. Spherical or quasispherical nanoparticles were obtained at room temperature with tunable mean sizes and polydispersities depending on reaction conditions, that is, on copolymer block length, and copolymer and gold salt concentrations. By moderate increases of reaction temperature up to 65 degrees C, progressive formation of single-crystalline gold nanoplates in good yields takes place (up to 70%) without the necessity of additional reactants or growing solutions. These nanoplates are characterized by lateral mean sizes between 0.1-1.2 microm depending on copolymer concentration and reaction temperature, with mainly truncated or rounded triangular shapes with {111} planes as two basal surfaces. This allows us to tune the surface plasmon band of the nanoplates from ca. 850 nm to more than 1100 nm, well inside the near-infrared region (NIR), which enables the use of these type of nanostructures as a very promsing materials in applications such as optical coatings, SERS, and cancer cell hyperthermia. We proposed that the growth of these nanostructures can stem from a decrease in the reaction rate as temperature increases due to an enhanced copolymer hydrophobicity, which gives rise to a structure of interacting micelles formed from the fluid via a percolation transition (known as "soft gel") at elevated temperatures. In this way, reduction becomes slow enough to allow kinetic control of the reaction, and preferential adsorption of the copolymer molecules/micelles on certain crystallographic planes can favor the growth of certain nanocrystal facets to give the final structure. This alternative water-based system provides a more convenient and environmentally benign route to the synthesis of shape-controlled noble-metal nanocrystals in high yield because it does not involve toxic organic solvents or reagents and serves as a bridge between two frontline discipline: the block copolymeric science and anisotropic nanoparticles.     

Phenylethyl Glycosides from Globularia alypum Growing in Turkey

From the leaves of Globularia alypum, three new phenylethyl glycosides, namely galypumosides A (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐[(E)‐p‐coumaroyl]‐β‐glucopyranoside; 1 ), B (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐[(E)‐feruloyl]‐β‐glucopyranoside; 2 ), and C (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐menthiafoloyl‐β‐glucopyranoside; 3 ), were isolated, together with two known phenylethyl glycosides, calceolarioside A and verbascoside. Eight iridoid glucosides, catalpol, globularicisin, globularin, globularidin, globularinin, globularimin, lytanthosalin, and alpinoside, a flavon glycoside, 6‐hydroxyluteolin 7‐O‐sophoroside, a lignan glycoside, syringaresinol 4′‐O‐β‐glucopyranoside, and a phenylpropanoid glycoside, syringin, were also obtained and characterized. The structures of the isolates were elucidated on the basis of 1D‐ and 2D‐NMR experiments as well as HR‐MALDI‐MS.     

H2‐Fueled ATP Synthesis on an Electrode: Mimicking Cellular Respiration

ATP, the molecule used by living organisms to supply energy to many different metabolic processes, is synthesized mostly by the ATPase synthase using a proton or sodium gradient generated across a lipid membrane. We present evidence that a modified electrode surface integrating a NiFeSe hydrogenase and a F₁F₀‐ATPase in a lipid membrane can couple the electrochemical oxidation of H₂ to the synthesis of ATP. This electrode‐assisted conversion of H₂ gas into ATP could serve to generate this biochemical fuel locally when required in biomedical devices or enzymatic synthesis of valuable products.     

A Jordan–Hölder theorem for weakly group-theoretical fusion categories

We prove a version of the Jordan–Hölder theorem in the context of weakly group-theoretical fusion categories. This allows us to introduce the composition factors and the length of such a fusion category \({\mathcal C}\), which are in fact Morita invariants of \({\mathcal C}\).     

Highly diastereoselective nucleophilic addition to myrtenal. Straightforward synthesis of an enantiopure scorpionate ligand

The work described here represents the first example in which an efficient and highly diastereoselective nucleophilic 1,2-addition of an organolithium reagent has been performed on a carbonylic prostereogenic center to give an enantiopure scorpionate ligand in only one step.     

Mathematical Modelling and Computer Simulation of Linear Polymer Degradation: Simple Scissions

Summary: Degradation of a polymer in a reactor by the degrading agent(s) follows a distinct pattern, primarily influenced by structural integrity and reactor environment. This distinct pattern is recorded in the changes in the evolved molecular weight distribution (MWD) or polymer chain length distribution (PCLD) curve characteristics from the initial intact state. Modern size exclusion chromatography (SEC) is the best laboratory‐based method that can clearly provide these plots in the form of chromatogram; however, detailed molecular information is not available. The nature of molecular destruction can be well‐characterised if the distinct MWD shift patterns can be simulated to fingerprint the different chain scission dynamics. This is investigated by our current research using the power of computer simulation techniques to gain insight into the polymer ageing processes. One such technique for studying simple decay processes is presented here, and the results are compared with experimental findings. The concept of a binary tree scission model is introduced to show chain rupture as a sequence of probabilistic events and as a non‐linear function of time. Two new mathematical algorithms, an iterative Monte Carlo structured probability scheme and a semi‐iterative algebraic exact statistical formulation method, are investigated to implement this model and simulate the evolution of resultant temporal MW distribution. The latter, an innovative approach to mathematical modelling, has the potential to generate a statistically perfect instant MWD decay curve. A statistical comparison of the product yield is presented from the data obtained using a wide variety of simulated scission regimes to determine the sources of variability.

Simulated MWD lateral shift for percent cut scission model showing deviation from the initial MWD (red) over degradation time zones T_j(0 ≥ j ≤ 9) with bimodal and curve broadening effect due to accumulation of varied percent cut range 5–30%.