Application of mass spectrometry in structural problems in triterpenes

Mass spectral data on 105 pentacyclic triterpenoids have been collated and analysed.From this analysis, it has been possible to identify base peaks which are characteristic of specific stereoskeletons.     

工作记忆的负荷影响心理旋转任务中的性别差异

目的:探讨心理旋转任务中的性别差异是否受工作记忆的负荷的影响。方法:采用先后呈现提示刺激和目标刺激的范式,任务分为三种:1.无效提示的数字旋转;2.有效提示的数字旋转;3.有效提示的PMA图形旋转。结果:重复测量的方差分析表明:对无效提示的数字旋转任务,男性和女性之间的反应时和正确率都无差异;对有效提示的数字旋转任务,男性和女性之间的正确率无差异,而反应时的差异边缘显著;对有效提示的PMA图形旋转任务,男性和女性之间的正确率无差异,而反应时有显著差异。结论:工作记忆的负荷可能会影响心理旋转任务中的性别差异。     

Inhibition of DNA polymerases and DNA topoisomerase II by triterpenes produced by plant callus

We found that some triterpene compounds could not only selectively inhibit the activities of mammalian DNA polymerase alpha (pol alpha) and beta (pol beta), but could also potently inhibit DNA topoisomerase II (topo II) [Biochem. J. 350 (2000) 757]. Here, we report that natural triterpenes produced by callus from an ancient Chinese medicinal plant were also inhibitors of the enzymes, and some were more selective than others. The natural triterpenes with a carboxyl group equally inhibited the activities of pol alpha, pol beta, and topo II, while the olide-type triterpenes with a ketone group suppressed the activities of pol beta and topo II, but not pol alpha. The other triterpenes from the callus hardly influenced these enzyme activities. As also described previously [J. Biochem. 130 (2001) 657], pol beta and topo II have a three-dimensionally similar triterpene-binding region, which is a pocket in which specific compounds can insert. The newly found triterpene inhibitors might structure-dependently insert into the pocket, and the pocket structure of each enzyme might, three-dimensionally but slightly, differ among them. The triterpene frames could be used for screening new inhibitors of the enzymes, and computer-simulated drug design using the frame and pocket structure may in theory be a possible approach to develop new inhibitors.     

用旋光度法测定静脉注射用人免疫球蛋白中麦芽糖含量

用旋光度测定法测定静脉注射用人免疫球蛋白 (IVIG)中麦芽糖含量 ,简便、快速 ,准确 ,重复性好 ,麦芽糖浓度与旋光度成正比 ,用该方法制备标准曲线具有很好的相关性 ,相关系数r(n =10 ) ±s为 0 .99996± 0 .0 0 0 0 3。测定两批IVIG ,分别重复测定 9次 ,麦芽糖含量分别为 9.85± 0 .0 82和 9.5 5± 0 .0 85变异系数分别为 0 .6 0 % ,0 .6 9% ,该法的内标回收率 % (n =9) ±s分别为 10 0 .4%± 0 .82和 98.8%± 0 .85 ,此法可作为IVIG中麦芽糖含量检测的常规方法     

Exploring stereochemical specificity of phosphotriesterase by MM-PBSA and MM-GBSA calculation and steered molecular dynamics simulation

Wild-type phosphotriesterase (PTE) prefers the S_P-enantiomers over the corresponding R_P-enantiomers by factors ranging from 10 to 90. To satisfy the binding modes of the PTE of S_P- and R_P-enantiomers, all-atom molecular dynamics simulations were carried out on two paraoxon S_P and R_P derivatives, namely, S_p-1 and R_p-1. Molecular mechanics Poisson–Boltzmann surface area and molecular mechanics generalized Born surface area (MM-PBSA and MM-GBSA) calculations indicated that His230 in S_p-1-PTE had a closer interaction with the substrate than that in R_p-1-PTE and that such interaction increased the catalytic efficiency of PTE for S_p-1. The steered molecular dynamics simulation indicated that, compared with S_p-1, R_p-1 in the unbinding (binding) may hinder some residue displacement, thus requiring more effort to escape the binding pocket of PTE. In addition, Trp131, Phe306, and Tyr309 are deemed important residues for the S_p-1 unbinding pathway via PTE, whereas Tyr309 alone is considered an important residue for the R_p-1 unbinding pathway. These results demonstrate the possibility of dramatically altering the stereoselectivity and overall reactivity of the native enzyme toward chiral substrates by modifying specific residues located within the active site of PTE.     

Blocks and bodies: sex differences in a novel version of the Mental Rotations Test

A novel version of the Mental Rotations Test (MRT) that alternated the standard block figures with three-dimensional human figures was administered to 99 men and 129 women. Women and men differed predictably in their retrospective reports of childhood play and digit ratios, a putative measure of prenatal androgen action. Compared to the block figure items, human figure items on the modified MRT were associated with an improvement in performance in both sexes. However, consistent with the study hypothesis, the enhancing effect of the human figure condition on performance as measured by conventional scores was smaller in men compared to women and not at all evident in men when performance was measured by ratio scores. A closer inspection of the human figures effects on test scores showed performance in women improved for both male and female figure items. In contrast, relative to scores on block figure items, performance in men improved when stimuli were male figures but did not improve when stimuli were female figures. These results add to the evidence that the magnitude of sex differences in scores on the MRT may vary according to the test content and item properties. The findings suggest that online measures of cognitive processing in response to different classes of test stimuli (e.g., animate vs. inanimate objects, self-relevant vs. neutral stimuli) may prove useful in research aimed at understanding the hormonal and social factors contributing to the sex difference in performance on the MRT.     

AFLP分子标记技术在昆虫学研究中的应用

AFLP分子标记技术是一种建立在PCR技术和RFLP标记基础上的新的DNA指纹分析技术 ,具有多态性丰富、结果稳定可靠、重复性好、所需DNA量少、可以在不知道基因组序列的情况下进行研究等特点 ,现已广泛用于构建遗传图谱、遗传多样性研究、系统进化及分类学、遗传育种和品质鉴定以及基因定位等方面。该文介绍了AFLP标记技术的原理以及在昆虫学研究中的应用。     

Applications of the molecular dynamics flexible fitting method

In recent years, cryo-electron microscopy (cryo-EM) has established itself as a key method in structural biology, permitting the structural characterization of large biomolecular complexes in various functional states. The data obtained through single-particle cryo-EM has recently seen a leap in resolution thanks to landmark advances in experimental and computational techniques, resulting in sub-nanometer resolution structures being obtained routinely. The remaining gap between these data and revealing the mechanisms of molecular function can be closed through hybrid modeling tools that incorporate known atomic structures into the cryo-EM data. One such tool, molecular dynamics flexible fitting (MDFF), uses molecular dynamics simulations to combine structures from X-ray crystallography with cryo-EM density maps to derive atomic models of large biomolecular complexes. The structures furnished by MDFF can be used subsequently in computational investigations aimed at revealing the dynamics of the complexes under study. In the present work, recent applications of MDFF are presented, including the interpretation of cryo-EM data of the ribosome at different stages of translation and the structure of a membrane-curvature-inducing photosynthetic complex.     

玉米连作、迎茬和轮作对田间杂草群落的影响

采用定位试验方法研究了北方旱作玉米长期 (1 0～ 1 2年 )连作、米豆米迎茬和豆麦米轮作条件下玉米田杂草群落变化。结果表明 ,3种茬口杂草密度以米豆米迎茬最小 ,杂草密度在不同年际间存在着差异 ,随着连作年限的增加 ,使连作区一些杂草种类增加 ,同时也有些杂草种类减少 ,但这种差别主要是在双子叶杂草之间 ,单子叶杂草种类没有变化 ,如连作 1 2年较连作 1 0年杂草增加了牛繁缕 ,减少了鸡眼草。 2年调查结果可知 ,连作、迎茬和轮作 3个茬口相比 ,米豆米迎茬较连作和轮作杂草种类发生的少     

Restrained molecular dynamics of solvated duplex DNA using the particle mesh Ewald method

Restrained and unrestrained aqueous solution molecular dynamics simulations applying the particle mesh Ewald (PME) method to DNA duplex structures previously determined via in vacuo restrained molecular dynamics with NMR-derived restraints are reported. Without experimental restraints, the DNA decamer, d(CATTTGCATC)d(GATGCAAATG) and trisdecamer, d(AGCTTGCCTTGAG)d(CTCAAGGCAAGCT), structures are stable on the nanosecond time scale and adopt conformations in the B-DNA family. These free DNA simulations exhibit behavior characteristic of PME simulations previously performed on DNA sequences, including a low helical twist, frequent sugar pucker transitions, BI- BII(–) transitions and coupled crankshaft (–) motion. Refinement protocols similar to the original in vacuo restrained molecular dynamics (RMD) refinements but in aqueous solution using the Cornell et al. force field [Cornell et al. (1995) J. Am. Chem. Soc., 117, 5179–5197] and a particle mesh Ewald treatment produce structures which fit the restraints very well and are very similar to the original in vacuo NMR structure, except for a significant difference in the average helical twist. Figures of merit for the average structure found in the RMD PME decamer simulations in solution are equivalent to the original in vacuo NMR structure while the figures of merit for the free MD simulations are significantly higher. The free MD simulations with the PME method, however, lead to some sequence-dependent structural features in common with the NMR structures, unlike free MD calculations with earlier force fields and protocols. There is some suggestion that the improved handling of electrostatics by PME improves long-range structural aspects which are not well defined by the short-range nature of NMR restraints.     

Effects of scapular upward rotation exercises on alignment of scapula and clavicle and strength of scapular upward rotators in subjects with scapular downward rotation syndrome

The purpose of this study was to investigate the effects of a 6-week scapular upward rotation exercise (SURE) on scapular and clavicular alignment and scapular upward rotators strength in subjects with scapular downward rotation syndrome (SDRS). Seventeen volunteer subjects with SDRS were recruited from university populations. The alignment of the scapula and clavicle was measured using radiographic analysis and compared in subjects before and after a 6-week self-SURE program. A hand-held dynamometer was used to measure the strength of the scapular upward rotators. The subjects were instructed how to perform the self-SURE program at home. The 6-week self-SURE program was divided into two sections (the first section with non-resistive SURE during weeks 1–3, and the second section with resistive SURE using thera-band during weeks 4–6). The significance of the difference between pre- and post-program was assessed using a paired t-test, with the level of statistical significance set at p < 0.05. Significant differences between pre- and post-program were found for scapular and clavicular alignment (p < 0.05). Additionally, the comparison between pre- and post-program measurements of the strength of the scapular upward rotators showed significant differences (p < 0.05). The results of this study showed that a 6-week self-SURE program is effective for improving scapular and clavicular alignment and increasing the strength of scapular upward rotator muscles in subjects with SDRS.     

小麦,玉米轮作田蜘蛛群落结构及多样性研究

一、研究方法本项工作于1988—1990年在青州市南郊农田进行。位于东经118°17′,北纬36°27′,年平均气温9℃,年降雨量860mm以上,无霜期180天左右。调查了不同作物类型的地块,包括玉米间作(大豆)田、净玉米田、有水浇条件的麦田、旱麦田和田埂杂草五种生境。其中小麦、玉米轮作田各3块,每块面积0.2ha以     

Influence of tool rotation on 3D surface topography at the nanometric scale

The influence of the tool rotation on the 3D surface topography produced by the nano-cutting process is investigated using molecular dynamics simulations. The least square mean method is utilized to model the evaluation criteria for the surface roughness parameters. The effects of the tool rotation on the cutting force and the chip formation at the nano-metric scale are also evaluated. It is found that the chip formation produced with tool rotation is dominated by the ploughing and the shearing forces. With increase of the adopted rotation velocity, the cutting force is sharply increased and the smaller elastic recovery of the machined surface is observed. The 3D surface roughness parameters at the nano-metric scale are significantly influenced by the tool rotation velocity and the feed speed, and the surface quality can be improved by decreasing the tool rotation velocity and the feed speed.     

Separation of the pentacyclic triterpenes tylolupenols A and B from Tylophora kerrii

Tylolupenols A and B from Tylophora kerrii were separated and identified as D:C-friedolup-8(9)-en-3β-ol and D:C-friedolup-9(11)-en-3β-ol, respectively.     

Individual differences in women''s facial preferences as a function of digit ratio and mental rotation ability

The second-to-fourth digit ratio (2D:4D) and mental rotation (MR) ability are sexually dimorphic traits that appear early in development and have been correlated with exposure to prenatal androgens (Grimshaw, Sitarenios, & Finegan, 1995; Lutchmaya, Baron-Cohen, Raggatt, Knickmeyer, & Manning, 2004). The current study examined how 2D:4D and MR differences among women of European descent (N=41) were related to their (a) preferences for male faces: attractive (ATM), short-term (STM), and long-term mate (LTM), and (b) psychological femininity and masculinity, as measured by the Bem Sex-Role Inventory (BSRI) (Bem, 1981). To examine potential changes in facial preferences over their menstrual cycle, participants' preferences were measured during two experimental sessions separated by 2 weeks. The results indicated that (a) femininity scores decreased with decreasing 2D:4D, (b) masculinity scores increased with faster MR, (c) women preferred a more masculine male face for an STM than for an LTM, and (d) preference changes over the menstrual cycle varied systematically with 2D:4D. When compared with women with high 2D:4D ratios, low 2D:4D women (e) preferred a more masculine LTM, (f) recalled less parental bonding, (g) had shorter intimate relationships, and (h) reported more menstrual irregularity. The results are interpreted as support for an interactive hormonal theory of physical attraction.     

Seasonal variation of sexual differences in the volatile oil of Juniperus scopulorum

Very few differences between male and female trees were found in the volatile oil composition of Juniperus scopulorum Sarg. Differences were more apparent when the compounds were calculated as percent of total oil than as weight per g dry matter. Almost all of the sexual differences occurred in the growing season (March–May). Essentially no differences were observed during the rest of the year. The observed differences were very small and should not affect the choice of plant material used in revegetating efforts (when browse potential is important). These differences should not affect chemosystematic studies, particularly if sampling is done during the period of the year when the plants are dormant.