Protein deformation of lipid hybrid bilayer membranes studied by sum frequency generation vibrational spectroscopy

Structural deformations of lipid hybrid bilayer membranes induced by signal peptideless (SPL) proteins have been studied for the first time using the inherently surface specific nonlinear optical technique of sum frequency generation vibrational spectroscopy. Specifically, deformations of 1,2-distearoylphosphatidylglycerol(DSPG) membranes induced by interaction with FGF-1, a SPL protein which is released asa function of cellular stress through a nonclassical pathway, have been investigated. FGF-1 was found to induce lipid alkyl chain deformations in previously highly ordered DSPG membranes at the extremely low concentration of 1 nM at 60 degrees C. The deformation process was shown to exhibit a degree of reversibility upon removal of the protein by rinsing with buffer solution.     

Water-stable biphasic nanocolloids with potential use as anisotropic imaging probes

Electrified co-jetting of two aqueous polymer solutions followed by a thermal cross-linking step was used to create water-stable biphasic nanocolloids. For this purpose, aqueous solution mixtures of poly(acrylamide-co-acrylic acid) and poly(acrylic acid) were employed as jetting solutions. When the biphasic nanocolloids created by side-by-side electrified co-jetting were thermally treated, a cross-linking reaction occurred between amide groups and carboxylic groups to form stable imide groups. Infrared spectroscopy was employed to monitor the reaction. The quality and the integrity of the resulting biphasic nanocolloids were confirmed by confocal laser scanning microscopy, flow cytometry analysis, and dynamic light scattering. Selective encapsulation of two biomolecules in each phase of the biphasic colloids was maintained even after thermal reaction and suspension in aqueous environment. Well-dispersed spherical colloids with stable dye loadings in each hemisphere were kept intact without aggregation or dissolution for several weeks. Finally, biphasic nanocolloids were selectively surface-modified with a biotin-dextran resulting in water-stable particles to ensure binding of proteins only to a single hemisphere.     

Conformation orientation of syndiotactic polypropylene induced by deformation at different temperatures

Two syndiotactic polypropylene (sPP) sample films (S0 and S90) with different initial structures were prepared in this paper by isothermal crystallization from the melt at 0 and 90 degrees C, respectively. The polymorphic transitions of the two samples induced by deformation at different temperatures (20, 40, and 60 degrees C) were investigated by rheo-optical FTIR spectroscopy. The results indicated that stretching leads to the transition from the helical to trans-planar conformation and improves the orientation of both helical and trans-planar conformations for the sPP films. With increasing stretching temperature, the conformational transitions for the two sPP samples are all suppressed, and the orientation behavior of the two samples appears completely different. The orientation degree of S0 decreases with increasing stretching temperature, while that of S90 increases. These results suggest that the stretching temperature and initial structure have great influence on the conformation transition and orientation behavior of the sPP sample. On the basis of the experimental results, the schematic illustration of the conformation transition and orientation behavior of sPP during stretching has been proposed.     

Synthesis and isolation of methyl bismuth cysteine and its definitive identification by high resolution mass spectrometry

After the synthesis and isolation of methylated bismuth cysteine, its initial identification by IR-spectroscopy was performed, whereas for definitive identification, high resolution mass spectrometry (ESI-TOF-MS and LTQ Orbitrap) was carried out.     

Comparative enantioseparations with native beta-cyclodextrin,randomly acetylated beta-cyclodextrin and heptakis-(2,3-di-O-acetyl)-beta-cyclodextrin in capillary electrophoresis

Comparative enantioseparations were performed with three neutral cyclodextrins (CDs) in capillary electrophoresis (CE). In particular, native beta-CD was compared with single component heptakis(2,3-di-O-acetyl)-beta-CD (HDA-beta-CD) and randomly acetylated beta-CD (Ac-beta-CD) with the emphasis on the enantiomer migration order. The opposite affinity of the enantiomers of several chiral analytes was observed towards native beta-CD and its acetylated derivatives. The enantiomer affinity pattern of some chiral analytes was also opposite towards the two acetylated derivatives of beta-CD. In the case of the chiral drug clenbuterol (CL) an attempt was made to evaluate the possible structural reasons of the affinity reversal using one- and two-dimensional as well as transverse rotating frame nuclear Overhauser effect spectroscopy (ROESY). Significant differences were observed between the structure of the CL complexes with beta-CD and HDA-beta-CD.     

Neutron diffraction study of [H(4)Co(4)(C(5)Me(4)Et)(4)], a tetrahedral metal cluster complex with four face-bridging hydride ligands

A single-crystal neutron diffraction analysis of the cluster complex [H(4)Co(4)(C(5)Me(4)Et)(4)] was carried out on the new quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin. The structure consists of four face-bridging hydrides attached to a tetrahedral cobalt metal core. Average distances and angles in the core of the molecule are as follows: Co-Co = 2.571(8), Co-C = 2.158(6), Co-H = 1.749(7), H.H = 2.366(9) A; Co-H-Co = 94.6(3), H-Co-H = 85.1(3) degrees. The hydride ligands are located off the Co-Co-Co planes by an average distance of 0.923(8) A. It is suggested that the dimensions of the HCo(3) fragments found in this molecule provide reasonable estimates for analogous distances and angles associated with chemisorbed H atoms situated on the 3-fold hollows of a cobalt surface. Crystallographic details: space group P2(1)/a (monoclinic); a = 21.979(2), b = 10.924(1), c = 34.406(2) A; beta = 90.81(1) degrees; Z = 8. Final agreement factor: R(F) = 0.099 for 3779 reflections [I > 2sigma(I)] collected at 20 K.     

Reflections on spontaneous asymmetric synthesis by amplifying autocatalysis

Spontaneous generation of chirality was observed in the course of studying the mechanism of asymmetric autocatalysis by NMR in ZnR2 alkylation of pyrimidin-5-aldehydes. A systematic study was carried out in order to discover its origins. Even in clean fresh non-glass reaction vessels spontaneous ee was clearly observed, and was not dependent on any single reaction parameter. For comparison it was demonstrated that enantiomerically pure Zn alkoxide catalyst could control the configuration of the reaction product even when present at below micromolar concentrations. The high propensity of the Soai reaction system to produce an enantiomerically enriched product without initial bias is suggested to result from stochastic effects. These are especially important in autocatalysis because all the final products can be derived by breeding from a small number of initial events. The statistical excess of one enantiomer in that set is sufficient to generate a measurable ee in the product. The process is aided by the requirement for dimerisation before the product is an active catalyst. An enumeration that rationalises these observations is provided.     

Optical biochemical sensor for determining hydroperoxides in nonpolar organic liquids as archetype for sensors consisting of amphiphilic conetworks as immobilisation matrices

This paper reports the successful design of a prototype of an optical biochemical sensor for the determination of hydroperoxides in nonpolar organic liquids. The sensor consists of a matrix of an amphiphilic polymer conetwork (APCN), a novel class of very promising polymeric materials for easy preparation of biochemical sensor matrices. APCNs are characterised by nanoscopic phase separation between the hydrophilic and the hydrophobic phases. For medium ratios of conetwork composition, the domains of both phases are interconnected both on the surface of the conetworks and throughout the bulk. The APCNs have peculiar swelling properties—the hydrophilic phase swells in hydrophilic media and the hydrophobic phase swells in hydrophobic media. In both types of media dissolved reagents can diffuse from the solution into the swollen phase of the polymeric conetwork. This enables loading of the hydrophilic phase of the APCNs with enzymes and indicator reagents by simple impregnation. Hydrophobic analytes can diffuse into the polymeric conetwork via its hydrophobic phase and react with indicator reagents immobilised in the hydrophilic phase at the huge internal interface between the two opposite phases. To prepare the described hydroperoxide-sensitive biosensors, we used APCN films consisting of 58% (w/w) poly(2-hydroxyethyl acrylate) (PHEA) as hydrophilic chains and 42% (w/w) polydimethylsiloxane (PDMS) as hydrophobic linkers. Horseradish peroxidase (HRP) and diammonium 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as indicator reagent were co-immobilised in this optically clear and transparent matrix. In this feasibility study the conditions investigated were principally those relevant to characterisation of the innovative matrix material and the disposable biosensor produced from it; the biosensor was not optimised. Sensitivity toward tert-butylhydroperoxide (tBuOOH) dissolved in n-heptane was acceptable, between approximately 1 and at least 50 mmol L⁻¹, even in the dry state. The response time was 1.7 to 5.0 min. No leaching of immobilised reagents was observed during a period of at least one hour. Pre-swelling the sensors with water increased the reaction rate and the total turnover number of the enzyme. In a dry atmosphere at 4 °C the sensors were found to be stable for at least two weeks.     

Electrical transport and noise in semiconducting carbon nanotubes

We investigate electrical transport and noise in semiconducting carbon nanotubes. By studying carbon nanotube devices with various diameters and contact metals, we show that the ON-currents of CNFETs are governed by the heights of the Schottky barriers at the metal/nanotube interfaces. The current fluctuations are dominated by 1/f noise at low-frequencies and correlate with the number of transport carriers in the device regardless of contact metal.