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旅游和工业化对亚热带森林地区大气环境质量及两种木本植物叶绿素荧光特性的影响 总被引:5,自引:0,他引:5
研究了旅游、工业化等不同类型的人类活动对亚热带森林大气CO2、SO2、NOx浓度及两种木本植物———木荷(SchimasuperbaGardn.etChamp.)和马尾松(PinusmasonianaLamb.)叶绿素荧光特性的影响。结果表明,不同形式人类活动使森林中大气CO2浓度上升了17~30μmol·mol-1,NOx化合物的浓度上升了5~20nmol·mol-1,SO2浓度上升了2~19nmol·mol-1。森林大气中CO2、NOx、SO2浓度随着人类活动的加强而升高。木荷和马尾松叶片Fv/Fm、ΦPSⅡ和稳态下的qP随人类活动加强而下降,其下降趋势与CO2、SO2、NOx的上升趋势相一致。 相似文献
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17β-雌二醇诱导血管内皮细胞一氧化氮释放及其与细胞内钙的关系 总被引:6,自引:0,他引:6
利用小牛胸主动脉内皮细胞(BAECs)作为模型,观察17β-雌二醇(E2)BAECs一氧化氮(NO)释放、一氧化氮合酶(eNOS)mRNA表达和细胞内钙(〔Ca^2+〕i)的影响,以及雌激素受体(ER)拮抗剂tamoxifen和NOS抑制剂(L-NAME)的作用。结果显示,E2(10^-12 ̄10^-8mol/L)呈尝试依赖性促进BAECs中NO的释放,以10^-8mol/L浓度E2处理BAECs 相似文献
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目的和方法 本研究采用离子探针Fura-2/AM结合计算机图象分析技术,并通过施加NO合酶抑制剂L-NNA和NO的作用靶--鸟苷酸环化酶(GC)的抑制剂美兰(Methylene Blue;MB),观察经培养的大鼠大脑皮层微血管内皮细胞和平滑肌细胞中的〖Ca^2+〗i在低氧作用后的变化以及与有关血管舒张因子NO和cGMP之间的关系。结果 低氧时大脑微血管内皮细胞和平滑肌细胞内的Ca^2+浓度有下降, 相似文献
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蛋白质修饰剂,变性剂和活性氧对菠菜叶片光系统Ⅱ光失活的… 总被引:1,自引:0,他引:1
菠菜叶圆片以活性氧,蛋白质修饰剂和变生剂结合强光处理半小时,检测叶绿素荧光动力不并与单照强光的对照作比较,加入H2O2,O2^-,OH和^1O2等活性氧加剧了PSⅡ的光抑制作用,Fv/Fm,QP和ΦPSⅡ降低,qN和1-qp相应上升,4种蛋白质修饰剂NBS,DEPC,BDE和ρCMB的处理,使叶片的Chl的荧光参数发生了与活性氧作用相类似的变化,尤以精氨酸残基悠剂BDE的影响较为显著。 相似文献
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两类Ca^2+通道拮抗剂对脑缺血时Ca^2+/CaM PKhⅡ活性抑制的保护 … 总被引:2,自引:1,他引:1
本文以蒙古沙土鼠双颈总动脉结扎(BCAO)前脑缺血模型Ca^2+/CaM PKⅡ活性变化为指标,研究了以氯胺酮(KT)、右美沙芬(DM)、苄丙咯(BP)及硝苯吡啶(ND)为代表的配体门控Ca^2+通道(LGCC)及电压门控Ca^2+通道(VGCC)两类Ca^2+通道拮抗剂对缺血性脑损伤的保护作用。结果如下:(1)脑缺血后,胞浆型及颗粒型Ca^2+/CaM PKⅡ活性均明显下降;(2)缺血前单独用药 相似文献
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缺氧对培养的肺动脉内皮细胞血管紧张素Ⅱ分泌的影响 总被引:2,自引:0,他引:2
缺氧是否通过影响血管内皮细胞的分泌功能而参与缺氧性肺动脉高压的发生尚不清楚。本实验动态观察了缺氧对培养的新生小牛内皮细胞(PAEC)的血管紧张素Ⅱ(ATⅡ)分泌的影响。结果发现:2.5%O2缺氧早期(1.5h),PAEC的ATⅡ分泌增加(P<0.01vs常氧组),缺氧后期与常氧组无明显差别;0%O2缺氧早期(1.5-6h),ATⅡ分泌明显降低(P<0.01vs常氧组及2.5%O2组),后期ATⅡ分泌明显增高(P<0.01vs常氧组及2.5%O2组);无论缺氧还是常氧条件下,NO供体SIN1显著抑制ATⅡ的分泌(P<0.01),而内源性NO抑制剂硝基精氨酸则明显促进ATⅡ分泌(P<0.01);0%O2缺氧24h后,PAEC细胞内cGMP含量明显降低(P<0.05)。上述结果表明缺氧可通过抑制PAEC的内源性NO产生而促进ATⅡ的分泌,PAEC自分泌的改变可能参与缺氧性肺动脉高压的发生过程。 相似文献
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一氧化氮合酶的研究进展 总被引:4,自引:0,他引:4
一氧化氮是由L-精氨酸和氧分子在一氧化氮合酶及其辅因子NADPH、FAD、FMN、CaM和BH4催化作用生成的;NOS分为原生型和诱生型NOS,原生型NOS活性依赖于胞浆内Ca^2+水平,诱生型NOS是Ca^2+/CaM非依赖性酶,其活性开关是胞内nNOS mRNA水平,NOS可在多个水平被调节;NOS可能在心血管疾病的发病中起重要作用。 相似文献
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A novel molecular connectivity index, , based on the adjacency matrix of molecular graphs and novel atomic valence connectivities, , for predicting the molar diamagnetic susceptibilities of organic compounds is proposed. The is defined as: , where and Ei are the atomic valence connectivity and the valence orbital energy of atom i, respectively. A good QSPR model for molar diamagnetic
susceptibilities can be constructed from and using multivariate linear regression (MLR). The correlation coefficient r, standard error, and average absolute deviation
of the MLR model are 0.9918, 5.56 cgs, and 4.26 cgs, respectively, for the 721 organic compounds tested (training set). Cross-validation
using the leave-one-out method demonstrates that the MLR model is highly reliable statistically. Using the MLR model, the
average absolute deviations of the predicted values of molar diamagnetic susceptibility of another 360 organic compounds (test
set) is 4.34 cgs. The results show that the current method is more effective than literature methods for estimating the molar
diamagnetic susceptibility of an organic compound. The MLR method thus provides an acceptable model for the prediction of
molar diamagnetic susceptibilities of organic compounds.
Figure Plot of calculated vs experimental values of molar diamagnetic susceptibilities using the multivariate linear regression (MLR)
model (Eq. 8) 相似文献
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Jaiswal M Khadikar PV Scozzafava A Supuran CT 《Bioorganic & medicinal chemistry letters》2004,14(12):3283-3290
QSAR study on the tumor-associated transmembrane carbonic anhydrase IX (CA IX) isoenzyme has been made using a large pool of distance-based topological indices : W, Sz, PI (0)chi, (1)chi, (2)chi,(0)chi(v), (1)chi(v), (2)chi(v). A combined set of 32 aromatic and heterocyclic compounds, including the six clinically used derivatives: acetazolamide, methazolamide, ethoxyzolamide, dichlorophenamide, dorzolamide, and brinzolamide are used for this purpose. The results have shown that the inhibition of the tumor-associated isoenzyme IX with aromatic and heterocyclic sulfonamides can be modeled excellently in multiparametric regression after introduction of indicator parameters. The predictive power of the models is discussed using probable error of correlation (PE), variance-inflation factor (VIF), and cross-validation parameters: PRESS, SSY, r(2) (cv) (S) PRESS, and PSE. This is the first report on QSAR study on inhibition of tumor-associated isoenzyme IX. 相似文献
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A new method is proposed for calculating aqueous solvation free energy based on atom-weighted solvent accessible surface areas. The method, SAWSA v2.0, gives the aqueous solvation free energy by summing the contributions of component atoms and a correction factor. We applied two different sets of atom typing rules and fitting processes for small organic molecules and proteins, respectively. For small organic molecules, the model classified the atoms in organic molecules into 65 basic types and additionally. For small organic molecules we proposed a correction factor of hydrophobic carbon to account for the aggregation of hydrocarbons and compounds with long hydrophobic aliphatic chains. The contributions for each atom type and correction factor were derived by multivariate regression analysis of 379 neutral molecules and 39 ions with known experimental aqueous solvation free energies. Based on the new atom typing rules, the correlation coefficient (r) for fitting the whole neutral organic molecules is 0.984, and the absolute mean error is 0.40 kcal mol–1, which is much better than those of the model proposed by Wang et al. and the SAWSA model previously proposed by us. Furthermore, the SAWSA v2.0 model was compared with the simple atom-additive model based on the number of atom types (NA). The calculated results show that for small organic molecules, the predictions from the SAWSA v2.0 model are slightly better than those from the atom-additive model based on NA. However, for macromolecules such as proteins, due to the connection between their molecular conformation and their molecular surface area, the atom-additive model based on the number of atom types has little predictive power. In order to investigate the predictive power of our model, a systematic comparison was performed on seven solvation models including SAWSA v2.0, GB/SA_1, GB/SA_2, PB/SA_1, PB/SA_2, AM1/SM5.2R and SM5.0R. The results showed that for organic molecules the SAWSA v2.0 model is better than the other six solvation models. For proteins, the model classified the atoms into 20 basic types and the predicted aqueous free energies of solvation by PB/SA were used for fitting. The solvation model based on the new parameters was employed to predict the solvation free energies of 38 proteins. The predicted values from our model were in good agreement with those from the PB/SA model and were much better than those given by the other four models developed for proteins.Figure The definition of hydrophobic carbons. Here CA, CB and CD are three carbon atoms; X represents a heteroatom. According to our definition, CB is a hydrophobic carbon, CA is not a hydrophobic carbon because a heteroatom is within four atoms and CD is not a hydrophobic carbon because CD is sp2- hydridized and in a six-member ring.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
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Kamal I. Al-Malah 《Journal of molecular modeling》2011,17(5):1029-1034
The aqueous solubility of a single-carbon organic molecule as a function of its size & dipole moment was investigated. The
molecular dipole moment was chosen to represent the polar character of a poly-atomic molecule. It is hypothesized here that
at a given pH, temperature, and pressure, the solubility of a single-carbon organic molecule in water will be a function of
its polar character; namely, dipole moment and of its molecular size. Different forms of the solubility function were tested;
it was found that the solubility model, given by Eq. 1, which is based on the polar character and the molecular volume, adequately described the aqueous solubility of single-carbon
organic moieties. The aqueous solubility of single-carbon organic solutes exhibits maximum at the condition of high polar
character (large dipole moment) and low molecular volume. The general trend of the solubility of single-carbon organic solutes,
based on the proposed model (Eq. 1) could be explained in terms of the trade-off between the driving force (degree of polar character of the solute) for solubilization
versus the resistance to be solubilized as a result of the entropic effects which increase with increasing molecular volume
of the organic moiety. 相似文献
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This extension of the liquid hydrocarbon model seeks to quantify the thermodynamic contributions to protein stability from the removal of nonpolar and polar surface from water. Thermodynamic data for the transfer of hydrocarbons and organic amides from water to the pure liquid phase are analyzed to obtain contributions to the thermodynamics of folding from the reduction in water-accessible surface area. Although the removal of nonpolar surface makes the dominant contribution to the standard heat capacity change of folding (delta C0fold), here we show that inclusion of the contribution from removal of polar surface allows a quantitative prediction of delta C0fold within the uncertainty of the calorimetrically determined value. Moreover, analysis of the contribution of polar surface area to the enthalpy of transfer of liquid amides provides a means of estimating the contributions from changes in nonpolar and polar surface area as well as other factors to the enthalpy of folding (delta H0fold). In addition to estimates of delta H0fold, this extension of the liquid hydrocarbon model provides a thermodynamic explanation for the observation [Privalov, P. L., & Khechinashvili, N. N. (1974) J. Mol. Biol. 86, 665-684] that the specific enthalpy of folding (cal g-1) of a number of globular proteins converges to a common value at approximately 383 K. Because amounts of nonpolar and polar surface area buried by these proteins upon folding are found to be linear functions of molar mass, estimates of both delta C0fold and delta H0fold may be obtained given only the molar mass of the protein of interest.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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通过对有机化合物非氢原子进行分类、参数化染色、建立非氢原子之间的关系得到新的结构描述符.对灯盏花的64种挥发性有机化合物结构进行了参数化表征,运用多元线性回归(MLR)和偏最小二乘回归(PLS)方法构建了化合物结构与色谱保留时间的关系模型.通过“留一法”交互检验对模型的稳定性进行了评价,利用外部样本集对模型的预测能力进... 相似文献