Hierarchical self-assembly of a biomimetic diblock copolypeptoid into homochiral superhelices

The aqueous self-assembly of a sequence-specific bioinspired peptoid diblock copolymer into monodisperse superhelices is demonstrated to be the result of a hierarchical process, strongly dependent on the charging level of the molecule. The partially charged amphiphilic diblock copolypeptoid 30-mer, [N-(2-phenethyl)glycine](15)-[N-(2-carboxyethyl)glycine](15), forms superhelices in high yields, with diameters of 624 ± 69 nm and lengths ranging from 2 to 20 μm. Chemical analogs coupled with X-ray scattering and crystallography of a model compound have been used to develop a hierarchical model of self-assembly. Lamellar stacks roll up to form a supramolecular double helical structure with the internal ordering of the stacks being mediated by crystalline aromatic side chain-side chain interactions within the hydrophobic block. The role of electrostatic and hydrogen bonding interactions in the hydrophilic block is also investigated and found to be important in the self-assembly process.     

Spin-seebeck effect: a phonon driven spin distribution

Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution.     

Facile Synthesis of 2-Substituted cis-2-cyclopentene-1,4-diol Derivatives

2-Substituted cis-2-cyclopentene-1,4-diol derivatives are used as starting materials for prostaglandin synthesis¹. Two papers concerning the synthesis of these compounds have been published so far ^1,2. In this paper we would like to present an alternative method for synthesis of 2-substituted cis-2-cyclopen-tene-1,4-diols from easily available cis-2-cyclopentene-1, 4-diol diacetate 1 ³.     

Selective labeling of extracellular proteins containing polyhistidine sequences by a fluorescein-nitrilotriacetic acid conjugate

The compound NTA-DCF consists of two components, a dichlorofluorescein (DCF) reporter and a nitrilotriacetic acid (NTA) functionality. The latter binds polyhistidine sequences selectively through a bridging metal ion. The NTA-DCF conjugate has photophysical properties similar to those of the parent DCF fluorophore both by itself and as its nickel(II) complex. The insensitivity of the emission to paramagnetic ions allows the probe to label His6-tagged proteins fluorescently on the extracellular surfaces of HEK 293-T and HeLa cells.     

Using unnatural protein fusions to engineer resveratrol biosynthesis in yeast and Mammalian cells

Resveratrol is a naturally occurring defense compound produced by a limited number of plants in response to stresses. Besides cardiovascular benefits, this health-promoting compound has been reported to extend life spans in yeasts, flies, worms, and fish. To biosynthesize resveratrol de novo, tyrosine ammonia lyase (TAL), 4-coumarate CoA-ligase (4CL), and stilbene synthase (STS) were isolated from Rhodobacter sphaeroides, Arabidopsis thaliana, and Vitis vinifera, respectively. Yeast cells expressing 4CL and STS produce resveratrol when fed with 4-coumaric acid, the substrate of 4CL. When a translational fusion protein joining 4CL and STS was used, yeast cells produced 15-fold more resveratrol than the cotransformed cells, suggesting that physical localization of 4CL and STS facilitate resveratrol production. When the resveratrol pathway was introduced into human HEK293 cells, de novo biosynthesis was detected, leading to intracellular accumulation of resveratrol. We successfully engineered an entire plant natural product pathway into a mammalian host.     

Spatial contagion between financial markets: a copula‐based approach

A method is proposed for defining and investigating spatial contagion between two financial markets X and Y by using the information contained in their copula. A practical illustration of the introduced method is also given by examining the presence of contagion among two European stock indices (namely, FTSE 100 and DAX). Copyright © 2009 John Wiley & Sons, Ltd.     

ESIPT reaction starting from S2 and S3 singlet states in 3-hydroxyflavone

Spectra fluorescence at excitation of emission within spectral intervals of S₃, S₂ and S₁ bands of absorption, and excitation at registration of fluorescence at maxima of blue and green bands of emission have been studied in 3-hydroxyflavone solution. A possibility of ESIPT reaction starting from S₃ and S₂ states of parent 3HF molecule was shown for the first time follows from observations of differences in excitation spectra of normal and tautomer forms of 3HF, and from different ratios of these forms intensities upon excitation in different ranges of UV spectra of absorption.