The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

The emulsifying properties of β-lactoglobulin genetic variants A, B and C

The emulsifying properties of three genetic variants of β-lactoglobulin (β-lac) (the A, B and C variants) are investigated as a function of protein concentration. Differences in the emulsifying properties and emulsion stability are explained in view of the known differences in physico-chemical and structural/conformational properties of the β-lac variants. β-lac A forms the finest emulsion droplets, and β-lac C the largest droplets. The order of decreasing emulsifying ability (A>B>C) can be explained in terms of differences in the molecular structure, and conformational stability of the variant proteins. The creaming stability, when compared at the same particle size, is greatest for β-lac C, with β-lac A and B having a similar and lower stability. The differences in creaming stability may arise from a higher surface coverage for the β-lac C droplets at an equivalent particle size. The storage stability is lower for β-lac A than for β-lac B and C, which both show a similar behaviour. Storage stability differences are discussed in terms of differences in molecular structure, conformational stability, interfacial viscosity and surface coverage for the three variants.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

A Monte Carlo simulation of the aggregation, phase-separation, and gelation of model globular molecules

Monte Carlo computer simulation on a square 3-D lattice is used to model state behavior of globular copolymers. Two types of globular molecules were defined. One consisted of a single type of subunit (a homopolymer) while the second contained a core of strongly attractive subunits and an outer layer of less strongly attractive subunits (a heteropolymer). Systems of globules were simulated at varied volume fraction (V(F)) and reduced temperature (T(R)), and state diagrams were constructed. These state diagrams contained state boundaries defined by the V(F)/T(R) combinations at which the system formed a percolating network and at which the various component subunits in the globule unfolded. Simulated systems could exist in a number of states (between 4 and 7), depending on the V(F), T(R), whether the molecule was a homo- or heteroglobule and whether the globules were allowed to interact with each other or not. All systems exhibited a gelation/crossover line that resembled a lower critical solution temperature. All systems also exhibited a critical gelation concentration, above which a continuous network was formed. The critical gelation concentration varied between about 2-4% V(F) depending on the type of system. This is comparable to experimental critical gelation concentrations of in the region of 4% (w/w) for a range of associating polymers and biopolymers such as globular proteins and polysaccharides. Other states were formed which included one where elongated, fibril-like aggregated strands were formed, and a micelle-like aggregated state. The results are discussed in terms of the known state behavior of associating polymers and biopolymers (proteins and polysaccharides).     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。     

Laser‐induced volume changes during confocal Raman microscopy of whey‐protein‐stabilized emulsions and their relationship to protein content and particle diameters

The use of confocal Raman microscopy is applied to the study of whey‐protein‐stabilized oil‐in‐water emulsions. The stability of emulsions is an important parameter for many applications and is dependent on several factors including protein content and particle size. Emulsions were prepared with varying particle size ranging from 0.8 to 10.0 µm. Changes in sample volume due to laser‐induced heating were monitored and correlated to protein content in samples and to particle diameters. It was found that samples with the lowest protein content and larger particle diameters experienced the largest volume changes. The newly developed approach is of a potential predictive use. Copyright © 2013 John Wiley & Sons, Ltd.     

Simulating the equation of state of model globular proteins adsorbed at a surface

Monte Carlo computer simulation is used to follow the adsorption of a model globular and disordered protein at a hard surface and to simulate the surface equation of state for these molecules. The simulation utilizes the deformable globule model where the "protein" is treated as a collection of interacting subunits. Disordered globules are modeled as athermal molecules, whereas globular molecules have a strong attractive interaction between subunits. The surface equation of state is modeled by applying a known pressure to an adsorbed globule and following the changes in adsorbed conformation. Simulated equations of state for the disordered and globular molecules show features that are observed in experimental surface pressure versus area plots. In particular the simulated equations of state show "kinks" that correspond to regions where the adsorbed globules undergo conformational changes as they lift away from the surface in response to the increased pressure. The model proteins follow Bull's equation at low surface pressures in a way that is broadly in line with results from experiment, and the changes in conformation as a function of surface pressure are in line with predictions by DeFeijter and Benjamins made using a soft-particle model for adsorbed proteins.     

In silico targeting PAD4 for the treatment of rheumatoid arthritis

Structural Chemistry - Rheumatoid arthritis (RA) is an autoimmune disorder that causes chronic inflammation with periodic bursts of activity in multiple synovial joints which lead to irreversible...     

Nuclear orbiting and anomalies in nuclear reactions

In this paper, we report our measurements of back-angle oxygen and carbon particle yields from ¹⁶O+⁸⁹Y, ¹²C+⁹³Nb reactions forming the same compound nucleus ¹⁰⁵Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence at high excitation energies from ¹⁶O+⁸⁹Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission is also discussed.