نتایج جستجو برای: isomerization

تعداد نتایج: 5525  

Journal: :Journal of materials chemistry 2010
Frederico B De Sousa João D T Guerreiro Minglin Ma Daniel G Anderson Chester L Drum Rubén D Sinisterra Robert Langer

Tunable and durable photochromic materials are a rapidly expanding area of interest, with applications ranging from biomedical devices to industrial-fields. Here we examine electrospun poly (methacrylic acid) PMAA nanofibers covalently modified with the highly photochromic molecule, spiropyran (SP) or a derivate SP which is firstly coupled to a cyclodextrin molecule (βCDSP). The photochromic pr...

2014
M. W. Balk S. H. Courtney G. R. Fleming

Photochemical isomerization provides a practical testing ground for activated barrier crossing theories. Stilbene is a prototype, because (I) reaction may be initiated by a short optical pulse and the decay of the excited trans isomer followed optically, and (2) the isomerization rate is slow compared to vibrational or solvent relaxation processes in solution. The goal is to understand the effe...

Journal: :Physical chemistry chemical physics : PCCP 2013
Xufeng Lin Yuanyuan Qu Yanhong Lv Yanyan Xi David Lee Phillips Chenguang Liu

The dehydration mechanisms for glucose in β-pyranose (BP) and in open-chain (OC) forms, catalyzed by acids homogeneously and heterogeneously, were investigated using density functional and two-layer ONIOM calculations. The first dehydration reaction and competing reaction pathways are the main focus of the present study. The energetics of five dehydration and two isomerization pathways were exa...

Journal: :The FEBS journal 2005
Rajiv Tyagi Yu-Ting Lee Luke W Guddat Ronald G Duggleby

Ketol-acid reductoisomerase (EC 1.1.1.86) is involved in the biosynthesis of the branched-chain amino acids. It is a bifunctional enzyme that catalyzes two quite different reactions at a common active site; an isomerization consisting of an alkyl migration, followed by an NADPH-dependent reduction of a 2-ketoacid. The 2-ketoacid formed by the alkyl migration is not released. Using the pure reco...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2005
Marcin Golczak Vladimir Kuksa Tadao Maeda Alexander R Moise Krzysztof Palczewski

In vertebrate retinal photoreceptors, photoisomerization of opsin-bound visual chromophore 11-cis-retinal to all-trans-retinal triggers phototransduction events. Regeneration of the chromophore is a critical step in restoring photoreceptors to their dark-adapted state. This regeneration process, called the retinoid cycle, takes place in the photoreceptor outer segments and in the retinal pigmen...

Journal: :Acta crystallographica. Section F, Structural biology and crystallization communications 2012
Raji E Joseph Nathaniel D Ginder Julie A Hoy Jay C Nix D Bruce Fulton Richard B Honzatko Amy H Andreotti

The crystal structure of the interleukin-2 tyrosine kinase Src homology domain (Itk SH2) is described and it is found that unlike in studies of this domain using NMR spectroscopy, cis-trans-prolyl isomerization is not readily detected in the crystal structure. Based on similarities between the Itk SH2 crystal form and the cis form of the Itk SH2 NMR structure, it is concluded that it is likely ...

Journal: :The Journal of chemical physics 2011
J H Baraban A R Beck A H Steeves J F Stanton R W Field

Isomerization between the cis and trans conformers of the S(1) state of acetylene is studied using a reduced dimension discrete variable representation (DVR) calculation. Existing DVR techniques are combined with a high accuracy potential energy surface and a kinetic energy operator derived from FG theory to yield an effective but simple Hamiltonian for treating large amplitude motions. The spe...

2009
Martial Boggio-Pasqua Michael A. Robb Gerrit Groenhof

We have performed excited-state dynamics simulations of a Photoactive Yellow Protein chromophore analogue in water. The results of the simulations demonstrate that in water the chromophore predominantly undergoes single-bond photoisomerization, rather than double-bond photoisomerization. Despite opposite charge distributions in the chromophore, excited-state decay takes place very efficiently f...

Journal: :The Journal of organic chemistry 2001
L Zhang C W Borysenko T A Albright E R Bittner T R Lee

A series of alkyl- and aryl-substituted derivatives of cis,cis-1,2,5,6-tetrasilacycloocta-3,7-diene were prepared. Isomerization of these compounds to the corresponding trans,trans-1,2,5,6-tetrasilacycloocta-3,7-dienes by exposure to Ru and Zr hydride complexes was explored. Experimental probes of the isomerization were consistent with a stepwise mechanism involving metal hydride addition/elimi...

2009
J. S. Baskin L. Bañares S. Pedersen A. H. Zewail Arthur Amos Noyes

The femtosecond real-time dynamics of the isomerization reaction of trans-stilbene under collisionless conditions are studied using (2+1) resonance-enhanced multiphoton ionization (REMPI) and femtosecond depletion spectroscopy (FDS) in a pump-probe scheme. The observed transients reflect the macroscopic sample anisotropy decay (rotational coherence) and intramolecular vibrational energy redistr...

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