De novo design of a bolaamphiphilic peptide with only natural amino acids

A new self-assembling bolaamphiphilic peptide has been designed and synthesized using only natural amino acids. This simple peptide is composed of two lysines connected by 4-8 alanines to maintain the characteristics of the traditional bolaamphiphiles. Based on an irregular secondary structure, it can self-assemble into nanospheres, nanorods, or nanofibers with lengths up to micrometers. The long nanofibers can be broken into smaller fragments by sonication, however, they could reassemble into nanofibers after incubation. Furthermore, the nanostructures were shown to have considerable thermostability. This new bolaamphiphilic peptide differs from any other self-assembling peptides or bolaamphiphiles, and possibly provides a new approach to fabricate nanomaterials.     

Continuous-time photon-stimulated desorption spectroscopy studies on soft x-ray-induced reactions of CF3Br adsorbed on Si(111)-7×7

Continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was used to study the soft x-ray-induced reactions of CF(3)Br molecules adsorbed on Si(111)-7×7 near the Si(2p) edge (98-110 eV). The monochromatic synchrotron radiation was employed as a soft x-ray light source in the photon-induced reactions and also as a probe for investigating the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. Several different surface coverages were investigated. The PSD spectra from the low-CF(3)Br-covered surfaces show the production of surface SiF species, while those from the high-CF(3)Br-covered surfaces depict the formation of surface SiF, SiF(2), and SiF(3) species. The photolysis cross section of the submonolayer CF(3)Br-covered surface is determined as ～4.3×10(-18) cm(2). A comparison with the results on CF(3)Cl/Si(111)-7×7 surface is discussed.     

Dried polyacrylamide gel absorption: a method for efficient elimination of the interferences from SDS-solubilized protein samples in mass spectrometry-based proteome analysis

Sample preparation holds an important place in MS-based proteome analysis. For effective proteolysis and MS analysis, it is essential to eliminate the interferences while extracting the analytes of interest from complex mixtures. To address this, herein we describe a new dried polyacrylamide gel absorption method. In this method, the protein sample prepared using high concentration of SDS was directly and completely absorbed by vacuum-dried polyacrylamide gel, and then the interfering substances including SDS and some other salts were efficiently removed by in-gel washing steps while retaining the denatured proteins in the gel, thus offering a clean environment amenable to downstream buffer exchange, proteolytic digestion and digest recovery, etc. In combination with in-gel digestion and LC-MS/MS, the newly developed method was applied to the proteome analyses of membrane-enriched fraction and whole tissue homogenate. It was demonstrated that the method is suitable for the analysis of a complex biological sample and can be widely used for sample cleanup in shotgun proteome analyses.     

Metabolic Labeling of Sialic Acids in Living Animals with Alkynyl Sugars

Sialome sweet sialome : As sialic acids are involved in many host–pathogen recognition events and are markers of embryonic and malignant tissues, there is great interest in methods for the enrichment and identification of sialylated glycoproteins from complex tissues. Now N‐(4‐pentynoyl)mannosamine can be used to metabolically label sialylated glycoproteins in living animals, enabling future identification of new biomarkers.

     

Separation of three water-soluble vitamins by poly(dimethylsiloxane) microchannel electrophoresis with electrochemical detection

A method for rapid separation and sensitive determination of three water-soluble vitamins, pyridoxine, ascorbic acid (VC), and p-aminobenzoic acid (PABA) has been developed by PDMS microchannel electrophoresis integrated with amperometric detection. After treatment of the microchip with oxygen plasma, the peak shapes of the three analytes were essentially improved. Pyridoxine, VC, and PABA were well separated within only 80 s in a running buffer of 20 mM borate solution (pH 8.5). Good linearity was obtained within the concentration range of 2-200 microM for the three water-soluble vitamins. The detection limits were 1.0 microM for pyridoxine and VC, and 1.5 microM for PABA. The proposed method has been successfully applied to real human urine sample, without solid phase extraction, with recoveries of 80-122% for the three water-soluble vitamins.     

Asymmetric transfer hydrogenation catalysed by hydrophobic dendritic DACH-rhodium complex in water

Hydrophobic Fréchet-type dendritic chiral 1,2-diaminocyclohexane-Rh(III) complexes have been applied in the asymmetric transfer hydrogenation of ketones in water using HCOONa as hydrogen source. The catalysts were found to be finely dissolved in the liquid substrates in the aqueous mixture and exhibited high catalytic activity and enantioselectivity (52-97% ee). The catalytic loading could be decreased to 0.01 mol% and good conversion was still obtained with excellent enantioselectivity. Moreover, the catalyst could be easily precipitated from the mixture by adding hexane and reused several times without affecting the high enantioselectivity.     

π -Type and σ -type cation- π complexes of atomic cations

MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B⁺ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li⁺, N⁺, Na⁺, P⁺ and K⁺ form -type complexes, whereas H⁺, F⁺, and Cl⁺ form covalent -type complexes. With benzene Li⁺, B⁺, Na⁺, Al⁺, and K⁺ form -type complexes whereas H⁺, F⁺, and Cl⁺ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction.     

The HPLC Enantioresolution of Phenyl Isothiocyanated Amino Acids on Vancomycin Bonded Phase Using the Acetonitrile‐Based Mobile Phase: A Comparison to the Teicoplanin Phase

The phenyl isothiocyanate, an electrophilic reagent for peptide chain sequencing, is used to pre‐column derivatize a variety of α‐amino acids in alkaline medium before their enantioresolution on a vancomycin bonded chiral phase using the acetonitrile‐based mobile phase. The observed resolution is believed to be due to the re‐location of the hydrogen receptor site from sulfur to nitrogen on the isothiocyanyl fragment of derivatizing reagent, which in turn changes the enantioselectivity. Under the same chromatographic conditions, the resolution for N‐benzoylated, 3,5‐dinitrobenzoylated and N‐carbobenzyloxylated amino acids is either not found or unsatisfactory. Also, no resolution is obtained in the reversed‐ or normal phase mode for all phenyl isothiocyanated amino acids examined in this study.     

Neutron activation analysis of gold and iridium in steel

A method of determination of trace gold and iridium in steel is presented. The samples were preconcentrated with an anion exchanger. The chemical recoveries were determined by an isotope tracer technique using¹⁹⁸Au and¹⁹²Ir.