离子交换色谱法研究蛋白质与RNA的结合特异性

RNA是以磷酸二酯键相连的核苷酸组成的聚阴离子,而蛋白质在PH小于它的等电点的缓冲溶液中带有正电性.因此,它们在离子交换色谱分子时能出现在差异很大的洗脱组分中.据此.我们设计了用离子交换色谱法研究蛋白质与RNA的结合特异性方法,用以研究位于T细胞核内的具有RNA结合活性的蛋白质人环素33(hCyP33)与不同RNA的结合特性.结果表明,人亲环素33只有ply(A)尾序列结构的mRNA,即poly(A)^ RNA发生特异性结合.     

Investigation of the large-scale functional brain networks modulated by acupuncture

Previous neuroimaging studies have primarily focused on the neural activities involving the acute effects of acupuncture. Considering that acupuncture can induce long-lasting effects, several researchers have begun to pay attention to the sustained effects of acupuncture on the resting brain. Most of these researchers adopted functional connectivity analysis based on one or a few preselected brain regions and demonstrated various function-guided brain networks underlying the specific effect of acupuncture. Few have investigated how these brain networks interacted at the whole-brain level. In this study, we sought to investigate the functional correlations throughout the entire brain following acupuncture at acupoint ST36 (ACUP) in comparison with acupuncture at nearby nonacupoint (SHAM). We divided the whole brain into 90 regions and constructed functional brain network for each condition. Then we examined the network hubs and identified statistically significant differences in functional correlations between the two conditions. Following ACUP, but not SHAM, the limbic/paralimbic regions such as the amygdala, hippocampus and anterior cingulate gyrus emerged as network hubs. For direct comparisons, increased correlations for ACUP compared to SHAM were primarily related with the limbic/paralimbic and subcortical regions such as the insula, amygdala, anterior cingulate gyrus, and thalamus, whereas decreased correlations were mainly related with the sensory and frontal cortex. The heterogeneous modulation patterns between the two conditions may relate to the functional specific modulatory effects of acupuncture. The preliminary findings may help us to better understand the long-lasting effects of acupuncture on the entire resting brain, as well as the neurophysiological mechanisms underlying acupuncture.     

A Single Residue Influences the Reaction Mechanism of Ammonia Lyases and Mutases

All ways lead to Rome? Computer modeling and kinetic measurements identified a distinct residue in Phe/Tyr ammonia lyases (PAL/TAL) which controls whether the Friedel–Crafts or an E₁cB reaction mechanism takes place. Hence, Glu484 in pcPAL favors the Friedel–Crafts reaction (see picture, MIO=4‐methylidene imidazol‐5‐one) whereas an Asn in TAL gives an elimination reaction. These mechanistic investigations also reveal activity of a PAL mutant and a TAL towards an amino alcohol.

     

DNA脱碱基位点存在下非氢键配体的增强结合研究

众所周知,插入剂的DNA特性结合位点位于DNA碱基对之间,然而这种非共价相互作用对于含脱碱基（AP）位点的DNA来讲还没有引起足够的重视,虽然在生物细胞中总是存在着DNA脱碱基位点。本文以原黄素（proflavine,PF）为例研究了插入剂对DNA中AP位点的结合特性。实验结果表明,相对于插入位点而言,AP位点是PF的优先结合位点,AP位点的本征结合常数比插入结合常数高一个数量级以上。此外,PF的结合使含脱碱基位点DNA的热稳定性明显提高,表明PF在脱碱基位点的结合构像明显不同于插入结合时的分子定向。本文结果将有助于判断小分子的DNA结合方式所决定的药物的生物化学及生物物理效用。     

Ion Specificity on Electric Energy Generated by Flowing Water Droplets

The development of energy‐conversion devices using water movement has actively progressed. Ionovoltaic devices, which are driven by ion dynamics, show ion specificity by which different ions with identical charges show different output performance. However, the ion specificity remains poorly understood because the influence of the ion species on generated electric signals is not elucidated. The ion specificity in electric signals induced by flowing water droplet was investigated in terms of its relationship with the potential profile across the solid–liquid interface.     

The G553M Mutant of Peroxisomal Carnitine Octanoyltransferase Catalyses Acetyl Transfer and Acetyl-CoA Hydrolysis

Summary. The structure of carnitine acetyltransferase revealed a putative binding site for longer acyl chains but access was blocked by methionine 564 (G. Jogl and L. Tong (2003) Cell 112, 113–122). The equivalent residue in all long chain carnitine acyltransferases is a conserved glycine. Mutation of glycine 553 to methionine in bovine COT resulted in loss of activity with all acyl-CoA substrates except acetyl-CoA, supporting the hypothesis that the methionine blocks access for longer acyl chains. The kinetic characteristics of acetyl transfer to carnitine were identical in the native and mutant enzyme. However, rapid acetyl-CoA hydrolysis in the mutant but not the wild-type indicates perturbation of the catalytic site.     

Mechanistic studies of the oxidative coupling polymerization of phenols. VI. Comparison of reactivities of DMP,PPO-dimer,and -trimer in the copper-catalyzed oxidative coupling polymerization

In the oxidative coupling polymerization, catalyzed by copper-amine complexes, the oxidation rates of 2,6-dimethylphenol (DMP) and its C? O-coupled dimer [4-(2′,6′-dimethylphenoxy)-2,6-dimethylphenol] and trimer [4-(-4′-(2″,6″-dimethylphenoxy)-2′,6′-dimethylphenoxy))-2,6-dimethylphenol] have been determined. The DMP concentration dependence shows a Michaelis–Menten-type behavior. On the other hand, the dimer and trimer showed a first-order rate-dependence in the respective phenol concentrations. This indicates that the slow reaction step, following an equilibrium complex formation between DMP and copper complex, is relatively fast for both the dimer and the trimer. Therefore, coordination of dimer or trimer to the copper complex appears to be rate-determining. Furthermore, the dimer and trimer gave overall reaction rates approximately eight times higher than found for DMP. Following the Flory principle of equal reactivity for functional groups of oligomers in polycondensations, all PPO oligomers can be assumed to have equally high oxidation rates as the dimer and trimer. The yield of undesired DPQ side product is strongly reduced when starting with the dimer (0.18%), or trimer (0.17%), compared to 3.3% for DMP. This is not unexpected, since DPQ can only be formed from two monomeric DMP residues. In fact, using a 1/10 molar mixture of dimer/DMP already results in a DPQ yield of only 1.7%. Furthermore, when starting from DMP, it has been observed that DPQ was predominantly formed during the first 30% conversion. Starting from dimer (or trimer) DPQ was formed at an almost constant very low rate during the whole course of the reaction. From these experiments it can be concluded that the most important polymerization reaction involves oxidation of copper-coordinated DMP anion to its corresponding cations, followed by coupling with a copper coordinated PPO chain.