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931.
Protein refolding to its native state in vitro is a challenging problem in biotechnology, i.e., in the biomedical, pharmaceutical, and food industry. Protein aggregation and misfolding usually inhibit the recovery of proteins with their native states. These problems can be partially solved by adding a surfactant into a suitable solution environment. However, the process of this surfactant-assisted protein refolding is not well understood. In this paper, we wish to report on the first-ever simulations of surfactant-assisted protein refolding. For these studies, we defined a simple model for the protein and the surfactant and investigated how a surfactant affected the folding behavior of a two-dimensional lattice protein molecule. The model protein and model surfactant were chosen such that we could capture the important features of the folding process and the interaction between the protein and the surfactant, namely, the hydrophobic interaction. It was shown that, in the absence of surfactants, a protein in an "energy trap" conformation, i.e., a local energy minima, could not fold into the native form, which was characterized by a global energy minimum. The addition of surfactants created folding pathways via the formation of protein-surfactant complexes and thus enabled the conformations that fell into energy trap states to escape from these traps and to form the native proteins. The simulation results also showed that it was necessary to match the hydrophobicity of surfactant to the concentration of denaturant, which was added to control the folding or unfolding of a protein. The surfactants with different hydrophobicity had their own concentration range on assisting protein refolding. All of these simulations agreed well with experimental results reported elsewhere, indicating both the validity of the simulations presented here and the potential application of the simulations for the design of a surfactant on assisting protein refolding. 相似文献
932.
Lizeng PengHuawei Liu Tao ZhangFengzhi Zhang Tiansheng MeiYi Li Yulin Li 《Tetrahedron letters》2003,44(27):5107-5108
A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described. 相似文献
933.
IntroductionReversiblecolorchangesuponexternalorinternalstimulationshavebeenattractingmuchattentionduetotheirutilityasfunctionalmaterials .Forexample ,pho tochromismdescribesthecolorchangesinducedbypho toirradiationandcanbeusedasphoto recordingmateri als… 相似文献
934.
Studies of the electrochemical behavior of epinephrine at a homocysteine self-assembled electrode 总被引:6,自引:0,他引:6
The self-assembled electrode with the homocysteine monolayer (Hcy/Au) has been characterized by infrared spectroscopy and ac impedance spectroscopy in electrolyte. The Hcy/Au electrode is demonstrated to promote the electrochemical response of epinephrine (E) by cyclic voltammetry. A pair of well-defined redox waves was obtained and the calculated standard rate constant (ks) is 2.1×10−2 cm s−1 at the self-assembled electrode. The reduction peak of E can be used to determine the concentration of E in presence of ascorbic acid (AA) owing to the Hcy/Au also promoting the electrochemical oxidation of AA. 相似文献
935.
Liu H Yang S Balteanu I Balaj OP Fox-Beyer BS Beyer MK Bondybey VE 《Rapid communications in mass spectrometry : RCM》2004,18(13):1479-1481
A route to efficient generation of C6H4+*, potentially the benzyne radical cation, is presented. Laser vaporization of Mg+* and supersonic expansion in helium doped with o-, m-, or p-C6H4F2 yields, among other ions, o-, m-, p-C6H4F2Mg+* complexes, but no C6H4+*. Collision-induced dissociation experiments show that the o-C6H4F2Mg+* complex can be converted into C6H4+* in a mildly energetic collision, with a center-of-mass energy around 1-2 eV. These conditions can also be reached in the ion source when argon is used as a carrier gas. In this way, mass spectra containing the desired m/z 76 peak, i.e. C6H4+*, are obtained. 相似文献
936.
Delong Liu 《Tetrahedron letters》2007,48(4):585-588
Novel air-stable C2-symmetric tetrasubstituted ruthenocene-based ligands were readily synthesized and used for palladium-catalyzed asymmetric allylic substitution showing excellent enantioselectivity and high catalytic activity. 相似文献
937.
Rong Chen Yu-Hui Cheng Lei Liu Xiao-Song Li Qing-Xiang Guo 《Research on Chemical Intermediates》2002,28(1):41-48
MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B+ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li+, N+, Na+, P+ and K+ form -type complexes, whereas H+, F+, and Cl+ form covalent -type complexes. With benzene Li+, B+, Na+, Al+, and K+ form -type complexes whereas H+, F+, and Cl+ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction. 相似文献
938.
The anionic [MeSeFe(CO)4] and [MeSeCr(CO)5] complexes were synthesized by reaction of [PPN][HFe(CO)4] and [PPN][HCr(CO)5] with MeSeSeMe respectively via nucleophilic cleavage of the Se-Se bond. The ease of cleavage of the Se-Se bond follows the nucleophilic strength of metal-hydride complexes. Methylation of [RSeCr(CO)5?] by the soft alkylating agent MeI resulted in the formation of neutral (MeSeMe)Cr(CO)5 in THF at 0°C. In contrast, the [ICr(CO)5?] was isolated at ambient temperature. Reaction of [MeSeFe(CO)4?] or [MeSeCr(CO)5?] with HBF4 yielded (CO)3Fc(μ-SeMe)2Fe(CO)3 dimer and anionic [(CO )5Cr (μ-SeMe)Cr(CO)5?] respectively, and no neutral (HSeMe)Fe(CO)4 and (HSeMe)Cr(CO)5 were detected spectrally (IR) even at low temperature. Reaction of NOBF4 or [Ph3C][BF4] and [MeSeCr(CO)5?] resulted in the neutral monodentate (MeSeSeMe)Cr(CO)5 complex. Addition of 1 equiv CpFe(CO)2I to 2 equiv [MeSeCr(CO)5?] gave CpFe(CO)2(SeMe) and the anionic [(CO)5Cr(μ-SeMe)Cr(CO)5?] in THF at ambient temperature. 相似文献
939.
Thin film composite (TFC) membranes based polyamide were prepared with m-phenylenediamine (MPD), m-phenylenediamine-5-sulfonic acid (SMPD) and trimesoyl chloride (TMC) through interfacial polymerization technique on the polysulphone supporting film. The membranes were characterized using permeation experiments with salt water, attenuated total reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS) as well as scanning electronic microscopy (SEM). This study has shown that the active layer of TFC membrane is aromatic polyamide, including sulfuric acid function group (-SO3H) according to the result of ATR-IR and XPS. The NaCl rejection of RO membranes decreased and the flux increased when WSMPD/WMPD increased from 0 to 1, and the linear part with pendant -COOH in membrane barrier layer increased with the increase of SMPD content, but the surface of membrane becoming smoother and smoother with the increase of SMPD content. So the membranes performance mainly was determined by chemical structure in their barrier layer. 相似文献
940.
ZnS胶体溶液中某些无机盐光化学过程中产生的阴离子自由基的ESR研究 总被引:4,自引:0,他引:4
本文用自旋捕捉与ESR技术相结合的方法研究了ZnS胶体溶液中某些无机盐光化学过程中产生的无机阴离子自由基,并对自由基产生的机理进行了讨论 相似文献