Bildung von mehfach verzweigtem Pfropfcopolymerem durch Kupplungsreaktion

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Beneficial Effects of Epigallocatechin-3-O-Gallate,Chlorogenic Acid,Resveratrol, and Curcumin on Neurodegenerative Diseases

Many observational and clinical studies have shown that consumption of diets rich in plant polyphenols have beneficial effects on various diseases such as cancer, obesity, diabetes, cardiovascular diseases, and neurodegenerative diseases (NDDs). Animal and cellular studies have indicated that these polyphenolic compounds contribute to such effects. The representative polyphenols are epigallocatechin-3-O-gallate in tea, chlorogenic acids in coffee, resveratrol in wine, and curcumin in curry. The results of human studies have suggested the beneficial effects of consumption of these foods on NDDs including Alzheimer’s and Parkinson’s diseases, and cellular animal experiments have provided molecular basis to indicate contribution of these representative polyphenols to these effects. This article provides updated information on the effects of these foods and their polyphenols on NDDs with discussions on mechanistic aspects of their actions mainly based on the findings derived from basic experiments.     

Reaction rate of crosslinkings by using metallated polymer. I. Grafting and intramolecular crosslinkings at the first stage

Lithium-metallated styrene–p-benzylstyrene copolymer was reacted with chlorine-terminated polystyrene as a crosslinker polymer in tetrahydrofuran (THF) at 25°C. The rate constant was estimated from the changes in the concentration of metallated polymer by using photometrical measurements. The various reaction conditions were chosen and it became clear that the rate constants of grafting (k₁) and intramolecular crosslinkings (k_2intra) were gotten separately at the first stage. As a result, k_2intra showed larger values than k₁ and decreased with increasing degree of polymerization of crosslinker polymers.     

Reaktionsgeschwindigkeit der Bildung von Pfropf-Copolymeren durch Kupplungsreaktion

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Analysis of the effect of foreign gases in the production of hyperpolarized 129Xe gas on a simple system working under atmospheric pressure

Experimental conditions that affect the degree of polarization of 129Xe gas were tested for a higher degree of polarization to facilitate a laboratory use of 129Xe NMR, primarily on the effect of addition of foreign gases. When He, N(2), or D(2) gas was added separately to pure Xe gas with natural isotope abundance, D(2) gas gave better results than the others in enhancing the degree of polarization in 129Xe atom. When these gases were added in mixture, however, N(2) plus He was proved to be more efficient than D(2) or He in enhancing the degree of polarization. As a result, the degree of polarization was found to be increased by more than an order, when diluent gases were properly mixed; polarization as high as 35% was reached at gas composition of 5% Xe, 10% N(2), and 85% He, whereas only a few percent was attainable when Xe gas was polarized without mixing any foreign gases [J. Magn. Reson. 150 (2), 156-160 (2001)]. These results were discussed on a basis of quenching and buffer effects of foreign gases. Polarization was also measured after separating the pure Xe gas from the mixture; value of 22% was obtained for the Xe gas isolated after solidification in liquid nitrogen trap. Build-up time of the polarization was also tested, which did not change remarkably depending on the gas composition.     

Preparation of soluble microgel by the copolymerization of methylmethacrylate with p-divinylbenzene in the presence of tetrabromomethane

Various types of soluble crosslinked polymers obtained from the copolymerization of methylmethacrylate (MMA) and p-divinylbenzene (p-DVB) in the presence of a transfer agent (CBr₄) have been discussed in relation to the variation of the structure during the reaction time. When [p-DVB]/[MMA] = 1.49 × 10^?3 and [CBr₄]/[MMA] = 1.28 × 10^?4, only linear polymers (primary polymer; M _n = 1.0 × 10⁵) with pendant vinyl groups are formed intially. Considerable branched structure is attained in rather large polymers (M _n = 2.5 × 10⁵), but the number of pendant double bonds is not enough to reach the gelation. As the concentration of the transfer agent becomes high, the intermolecular crosslinking is depressed, and the formed polymers contain loops and short chains. At [p – DVB]/[MMA] = 7.43 × 10^?3 and [CBr₄]/[MMA] = 1.28 × 10^?3, the shape of polymer with the same M _n became compact gradually with increasing reaction time. These results are considered to be useful for the preparation of soluble crosslinked polymer with controlled structure.     

Solid-state conformation of diastereomeric -Pro-Pro-(Aib)4 sequences

The crystal structures of two diastereomeric -Pro-Pro-(Aib)₄- sequences, Cbz-l-Pro-l-Pro-(Aib)₄-OMe (1) and Cbz-d-Pro-l-Pro-(Aib)₄-OMe (2), have been determined by X-ray crystallographic analysis. The crystals of the two compounds were characterized by the following parameters: (1) monoclinic, P2₁, a=10.543 Å, b=8.103 Å, c=22.642 Å, β=97.679, Z=2, R₁=0.104, and R_w=0.327; (2) orthorhombic, P2₁2₁2₁, a=10.470 Å, b=10.953 Å, c=32.405 Å, Z=4, R₁=0.040, and R_w=0.046. In the asymmetric unit of 1, the homochiral l-Pro¹-l-Pro² adopts a polyproline II structure, which induces a left-handed (M) 3₁₀-helical structure in the following -(Aib)₄- sequence. The preferred conformation of diastereomeric 2, which contains heterochiral d-Pro¹-l-Pro² segments, was similar to that of 1 with differences at the N-terminal d-Pro residue.     

Imaging of internal stress around a mineral inclusion in a sapphire crystal: application of micro‐Raman and photoluminescence spectroscopy

We developed a micro‐Raman and photoluminescence imaging technique for visualizing the internal stress fields in a sapphire crystal. The technique was applied to an Australian sapphire gemstone with a zircon inclusion. Considering piezospectroscopic effects on Raman and photoluminescence spectra, the Raman shifts of sapphire around the zircon inclusion were converted to hydrostatic pressure and deviatoric components of stress tensor. The internal stress was highly concentrated at the tips of the zircon crystal, where the deviatoric stress and the hydrostatic pressure component reached 700 and 470 MPa, respectively. Generation of compressive stress on the crystal surface of zircon can be explained by the difference in thermal expansion coefficients and elastic constants between sapphire and zircon. In general, internal stress fields induced by mineral inclusions reflect the pressure and temperature conditions at which the host sapphire gemstones were crystallized. Thus, the present technique can be utilized to identify the origin of gemstones. Copyright © 2012 John Wiley & Sons, Ltd.