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1.
应用比较分子场分析法(CoMFA)对一系列抗癌性苯并噻唑类衍生物进行了三维定量构效关系(3D-QSAR)研究,建立了交叉验证的CoMFA模型,并在此基础上建立了非交叉验证的偏最小二乘分析模型.所建最佳模型的交叉验证相关系数为0.642,非交叉验证相关系数为0.976,估算的标准误差S=0.161,统计方差比F(3;20)=111.4,表明该模型是合理有效的.同时对该系列抗癌化合物的3D-QSAR进行了深入研究.结果表明,在R取代基的第一个原子上引入吸电子基团或原子,如F等,便可增强与它直接相连的C19的正电荷,从而增强C19ˉ位上处于静电场蓝色区域的原子的正电荷.同时,选择适当体积大小的取代基R,使之落入立体场绿色区域,就能有效地改善这类化合物的抗癌活性.  相似文献   

2.
本文采用分子对接法研究了24个5,6-二氢-2-吡喃酮衍生物与HIV-1蛋白酶的相互作用,并采用三维定量构效关系(3D-QSAR)研究了药物分子化学结构和生物活性之间的关系.最终得到模型的复相关系数(R_(cum)~2)为0.961、留一法交互校验复相关系数(Q_(cv)~2)为0.897,外部交互验证复相关系数(Q_(ext)~2)为0.880,从结果可以看出三维定量构效关系对化合物的抗艾滋病活性具有比较好的预测能力.然后通过分子对接研究了配体小分子和HIV-1蛋白酶活性氨基酸残基之间的结合模式,这些信息对于以后设计合成新的抗艾滋病药物具有一定的指导作用.  相似文献   

3.
采用比较分子场分析(CoMFA)方法对抗菌九肽、抗菌十四肽、抗菌十八肽进行三维定量构效关系(3D-QSAR)分析,建立了预测力强的3D-QSAR模型.结果表明,所建立的3D-QSAR模型对三种抗菌肽均有较好的统计学稳定性及预测能力(抗菌九肽:交叉验证系数q~2=0.537,非交叉验证相关系数r~2=0.961,外部样本检验复相关系数Q_(ext)~2=0.883;抗菌十四肽:q~2=0.502,r~2=0.718,Q_(ext)~2=0.645;抗菌十八肽:q~2=0.550,r~2=0.967,Q_(ext)~2=0.989).三维等势图不仅解释了抗菌肽结构与活性的关系,而且为抗菌肽的进一步合成提供了理论依据.  相似文献   

4.
采用比较分子场分析方法(CoMFA)和比较分子相似性指数分析方法(CoMSIA)对一系列吡啶并嘧啶类衍生物进行了三维定量构效关系(3D-QSAR)研究,建立了CoMFA和CoMSIA两种模型. 所构建的最佳模型的交叉验证相关系数分别为0.707和0.645,非交叉验证系数分别是0.964和0.972,模型的一些外部验证表明两个模型合理、可靠,并具有良好的预报能力. 同时,用分子对接的方法分析了该类化合物与Wee1激酶结构的作用模式,结果进一步表明,在R1和R5取代基上引入正电性基团,R2为体积小的电负性基团,同时选择体积中等和强的推电子的R3但亲水性的X取代基,能有效改善这类化合物的抑制活性.  相似文献   

5.
采用Topomer CoMFA方法对26个香豆素衍生物进行三维定量构效关系研究,建立了3D-QSAR模型,所得优化模型的非交叉相关系数、交互验证系数以及外部验证的复相关系数分别为0.973,0.666和0.960,结果表明该模型具有良好的稳定性和预测能力.运用这些信息进行分子对接,在理论上验证所构建的模型具有较高的可信性.此外,QSAR的研究结果可为新药合成提供理论参考.  相似文献   

6.
噻吩并嘧啶衍生物抗胃癌活性的CoMFA模型与分子设计   总被引:1,自引:0,他引:1  
基于比较分子力场分析(CoMFA)方法建立25种噻吩并嘧啶衍生物抗胃癌活性(pM)的三维定量构效关系(3D-QSAR)。训练集中20个化合物用于建立预测模型,测试集6个化合物(含模板分子)作为模型验证。已建立的CoMFA模型的交叉验证系数(Rcv2)、非交叉验证系数(R2)分别为0.369、0.831,说明所建模型具有较强的稳定性和良好的预测能力。该模型中立体场、静电场贡献率依次为40.9%、59.1%,表明影响抑藻活性(pI)的主要因素是取代基的库仑力、氢键及配位,其次是取代基的疏水性和空间位阻。基于此研究结果,设计了4个具有较高抗胃癌活性的新化合物,有待医学实验验证。  相似文献   

7.
采用Topomer CoMFA方法对30个芳基硫代吲哚衍生物进行三维定量关系研究,建立了3D-QSAR模型,所得模型的交叉验证相关系数q~2,非交叉验证相关系数r~2,外部验证的复相关系数Q_(ext)~2分别为0.562,0.878,0.985,结果表明该模型具有较好的稳定性和预测能力.Topomer CoMFA模型等势面提供的立体场与静电场可视化图像,直观的揭示了这一系列化合物中不同取代基结构对其生物活性的影响,运用这些信息进行分子设计,在理论上获得了5个具有较高活性的新化合物,该QSAR的实验结果可为合成新药提供理论参考.  相似文献   

8.
对一系列具有抗人乳腺癌细胞系MCF-7生物活性的微管蛋白抑制剂─芳基硫代吲哚衍生物(arylthioindole),进行了三维定量构效关系(3D-QSAR)和对接(docking)研究. 在训练集中,建立了具有良好统计质量和预报能力的比较分子力场分析(CoMFA) 模型,其非交叉验证相关系数平方R2为0.898,交叉验证相关系数平方q2为0.654. 同时在测试集的验证中得到预测相关系数平方R2(pred)为0.816, 进一步表明了该模型具有较高的预测能力. 此外,通过对接研究,获得了这些化合物与微管蛋白作用的键合方式和构象,发现该系列化合物的CoMFA力场分布与对接结合位点上的三维拓朴结构相一致. 根据CoMFA和对接分析的结果,细致地讨论和总结了有利于提高或改进该类化合物活性的主要因素,即在取代基R3、R4和R5上引进高电负性的基团,在取代基R6上引进带有高电负性且大体积的基团,以及在取代基R7上引进小体积的基团等都是有利的. 基于这些研究结果,在理论上还设计了5个新的具有较高活性的化合物.  相似文献   

9.
本文采用Topomer CoMFA方法对37个吡唑啉嘧啶类IL-2诱导T细胞激酶抑制剂进行三维定量构效关系研究.得到3D-QSAR模型,其交互验证系数q~2为0.728,非交叉相关系数r~2为0.994,主成分数N为8,标准估计误差SEE为0.097.结果表明该模型有较好的预测能力.采用Topomer Search技术在ZINC数据库中进行R基的筛选,并设计6个新分子.最后用分子对接技术研究了4个新分子与IL-2诱导的T细胞激酶(Itk)大分子蛋白的作用模式,从结果中可以看到,4个新分子与Itk蛋白的A/LYS391、A/MET438位点作用显著.  相似文献   

10.
采用Topomer CoMFA方法对27个苯氨基磺酸衍生物进行了三维定量构效关系研究。得到了3D-QSAR模型,其交互验证系数q2为0.713,非交叉相关系数r2为0.995,主成分数N为6,标准估计误差SEE为0.183。结果表明该模型有较好的预测能力。采用Topomer Search技术在ZINC数据库中进行R基的筛选,并设计了5个新分子,最后用分子对接技术研究了新分子与苯氨基磺酸衍生物大分子蛋白的作用模式,从结果中可以看到,新分子与苯氨基磺酸衍生物蛋白的A/ARG220、A/ARG63和A/ASN115位点作用显著.  相似文献   

11.
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.  相似文献   

12.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.  相似文献   

13.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.  相似文献   

14.
15.
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.  相似文献   

16.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.  相似文献   

17.
A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.  相似文献   

18.
We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.  相似文献   

19.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations.  相似文献   

20.
In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.  相似文献   

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