Some Aspects of Selectivity in the Reaction of Glycosyl Donors*

Some advantages, disadvantages, and anomalies of various donors in glycosidations are discussed. By studying several two‐component donor/acceptor‐diol reactions, it is shown that regiopreferences are not very sensitive to the type of donor used. However, in competitive glycosidations within a given type of donor and between different types of donor, it is shown that regio‐ and chemoselectivities must be indexed to donor reactivity.     

Efficient synthesis of phosphotyrosine building blocks using imidazolium trifluoroacetate

We have successfully employed imidazolium trifluoroacetate as a replacement for tetrazole for efficient synthesis of phosphotyrosine. This modification is compatible with the protecting groups commonly used in solution phase and Fmoc-solid phase peptide synthesis.     

Phenotype MicroArray Profiling of Zymomonas mobilis ZM4

In this study, we developed a Phenotype MicroArray? (PM) protocol to profile cellular phenotypes in Zymomonas mobilis, which included a standard set of nearly 2,000 assays for carbon, nitrogen, phosphorus and sulfur source utilization, nutrient stimulation, pH and osmotic stresses, and chemical sensitivities with 240 inhibitory chemicals. We observed two positive assays for C-source utilization (fructose and glucose) using the PM screen, which uses redox chemistry and cell respiration as a universal reporter to profile growth phenotypes in a high-throughput 96-well plate-based format. For nitrogen metabolism, the bacterium showed a positive test results for ammonia, aspartate, asparagine, glutamate, glutamine, and peptides. Z. mobilis appeared to use a diverse array of P-sources with two exceptions being pyrophosphate and tripolyphosphate. The assays suggested that Z. mobilis uses both inorganic and organic compounds as S-sources. No stimulation by nutrients was detected; however, there was evidence of partial inhibition by purines and pyrimidines, NAD, and deferoxamine. Z. mobilis was relatively resistant to acid pH, tolerating a pH down to about 4.0. It also tolerated phosphate, sulfate, and nitrate, but was rather sensitive to chloride and nitrite. Z. mobilis showed resistance to a large number of diverse chemicals that inhibit most bacteria. The information from PM analysis provides an overview of Z. mobilis physiology and a foundation for future comparisons of other wild-type and mutant Z. mobilis strains.     

A green alternative method for analysis of ivermectin and moxidectin in environmental water samples using automatized preconcentration previous MEEKC

Antiparasitic drugs derived from macrocyclic lactones (MLs) are widely used in livestock activities around the world. An increasing concern for local authorities is the environmental pollution as a consequence of veterinary drugs widely used in rural areas. The purpose of environmental analysis is to monitor low levels of pollutant analytes in a large number of samples. Also, due to the lipophilic characteristic of these lactones, long‐chain solvents are usually required for performing sample treatment before and during the analysis. Therefore, sensitive, specific, robust, and environmentally friendly analytical methods are still required. In this paper, a new automatized preconcentration methodology followed by microemulsion electrokinetic chromatography analysis was developed for the simultaneous separation and determination of the most used MLs, ivermectin (IVM) and moxidectin (MXD) in environmental water. XAD‐4 resin was employed as an adsorbent for the preconcentration process and ethanol was used as the eluent. In contrast to traditional analysis for IVM and MXD, in this methodology nonpolluting solvents were involved during the whole process and therefore, it could be considered as a contribution to green analytical chemistry. Under optimal experimental conditions, LOD obtained for IVM and MXD were of 3 × 10^?3 and 3.6 × 10^?3 μg/L, respectively.     

Entropy of Badminton Strike Positions

The aim of the current study was twofold: (i) to investigate the distribution of the strike positions of badminton players while quantifying the corresponding standard entropy and using an alternative metric (spatial entropy) related to winning and losing points and random positions; and (ii) to evaluate the standard entropy of the receiving positions. With the datasets of 259 badminton matches, we focused on the positions of players’ strokes and the outcome of each point. First, we identified those regions of the court from which hits were most likely to be struck. Second, we computed the standard entropy of stroke positions, and then the spatial entropy, which also considers the order and clustering of the hitting locations in a two-dimensional Euclidean space. Both entropy quantifiers revealed high uncertainty in the striking position; however, specific court locations (i.e., the four corners) are preferred over the rest. When the outcome of each point was taken into account, we observed that the hitting patterns with lower entropy were associated with higher probabilities of winning points. On the contrary, players striking from more random positions were more prone to losing the points.     

Measurement of absolute line intensities in the ν5-ν4 band of C2H2 using SOLEIL synchrotron far infrared AILES beamline

Absolute intensities of about 120 lines of the ¹²C₂H₂ molecule are reported for the ν₄-ν₅ band between 65 and 192 cm^-1, with an average accuracy of 5%. Vibrational transition dipole moment squared values and empirical Herman-Wallis coefficients are obtained allowing modelling the rotational dependence of the transition dipole moment squared. Special care is taken to accurately determine an apparatus function for the Bruker IFS 125-HR coupled to the synchrotron SOLEIL far infrared AILES beamline in order to minimize its effects on the line parameter retrieval.     

Some pitfalls in PAGE-LA-ICP-MS for quantitative elemental speciation of dissolved organic matter and metalomics

An experimental approach to evaluate the capabilities and limitations of polyacrylamide gel electrophoresis (PAGE) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for quantitative elemental speciation is presented. Two metalloproteins (superoxide dismutase, containing Cu and Zn, and thyroglobulin, containing I) with high binding affinity for metals, and metal-dissolved organic matter (DOM) complexes (from a compost leachate sample) which show different types of metal binding are studied. Iodine can be quantitatively detected in thyroglobulin after PAGE-LA-ICP-MS using either sodium dodecyl sulfate (SDS) PAGE or native PAGE. However, detection of Cu and Zn in superoxide dismutase after PAGE-LA-ICP-MS depends on the conditions of the PAGE method because possible metal losses can occur (either with SDS-PAGE or with native PAGE). The use of PAGE-LA-ICP-MS to study the contribution of DOM to the mobilization of metals from environmental samples is possible, but it depends also on the PAGE separation conditions owing to disequilibrium effects of metal-DOM complexes. Presented at the 4th International Conference on Trace Element Speciation in Biomedical, Nutritional and Environmental Sciences, 25–29 May 2008, Munich-Neuherberg, Germany.     

Multiple-injection affinity capillary electrophoresis to examine binding constants between glycopeptide antibiotics and peptides

Multiple-injection affinity capillary electrophoresis (MIACE) was used to determine binding constants (K(b)) between vancomycin, ristocetin, and teicoplanin from Streptomyces orientalis, Nocardia lurida, and Actinoplanes teichomyceticus, respectively, and fluorenylmethoxycarbonyl (Fmoc)-(Gly, Ala, Val, and Phe)-D-Ala-D-Ala peptides. In this technique, separate plugs of sample containing non-interacting standards, peptide one, buffer, and peptide two, were injected into the capillary column and electrophoresed. Peptides migrate through the column at similar electrophoretic mobilities but remain as distinct zones due to the buffer plug between peptides. The electrophoresis is then carried out in an increasing concentration of antibiotic in the running buffer. Continued electrophoresis results in a shift in the migration time of the peptides upon binding to the antibiotic. Analysis of the change in the relative migration time ratio (RMTR) of the resultant complexes relative to the non-interacting standards, as a function of the concentration of antibiotic yields a value for K(b). MIACE is a versatile technique that can be used to measure affinity constants between ligands of similar relative molecular mass and charge without the need of separate binding experiments. The findings described, herein, demonstrate the advantages of using MIACE to estimate binding parameters between ligands and receptors.     

Including quantum subsystem character within classical equilibrium simulations

A mixed quantum/classical density matrix approximation is derived. The density matrix makes use of quantum subsystem vibrational wave functions. The diagonal of the density matrix can be used as an equilibrium distribution in Monte Carlo simulations. The approximate distribution compares well with the path integral distribution for a model system. Since it includes quantum subsystem information, it performs much better than the quadratic Feynman-Hibbs distribution. These types of distributions can aid in including quantum vibrational information in otherwise classical simulations.