EHMO方法的分子轨道定域化

用Foster-Boys的定域化准则讨论了EHMO方法的分子轨道定域化问题,提出用双中心重叠积分近似计算双中心轨道偶极矩积分方法,得到的EHMO定域分子轨道与严格定域化结果接近,与从头计算方法的定域化结果定性一致。     

含双键有机小分子的定域分子轨道的研究

选择22种具有双键的有机小分子(含C、H、O和N原子)作模型分子,应用ab initioSTO-3G和Foster-Boys定域化分子轨道程序,对它们的定域分子轨道进行了研究,得到了定域分子轨道能量,确定了相应分子轨道间的相互作用。对烯类分子的光电子能谱进行了分析,结果较为满意。     

定域分子轨道中的σ—π分离

对含重键的分子体系,分子轨道定域化会涉及到两种完全不同的重键描述,即等价的重键或“香蕉”键和不等价的σ和π键,文献曾利用杂化轨道法对此进行过讨论。对于定域分子轨道,具体得出哪种描述取决于所采用的定域准则及计算中采用的近似方法。对于从头算法的定域化研究,Boys定域准则强烈地趋向于等价重键描述;Ruedenberg定域准则只是对未共轭的重键体系有较强的等价重键描述倾向,对共轭的重键体系,这种倾向性明显减     

有机链状分子的定域分子轨道的研究

利用Foster-Boys定域化程序和STO-3G ab initio方法,对含有C、H、O、N原子的100多个有机链状分子进行了研究,得到定域分子轨道能量及其相互作用参数。应用这些参数和定域分子轨道模型,对于众多的含有C、H、O、N原子的有机链状分子,可得到相应的正则分子轨道能量及其与定域分子轨道的关系。以此预测它们的电离能,结果与实验值符合较好。     

自然定域轨道方法研究

本文报导我们按自然定域轨道原理编制的NLMO程序以及对自然定域轨道计算方法的一些改进。用NLMO程序计算出七个具有不同成键特性分子(包括是否含有孤对或π键,是否含有多中心键等不同情况)的自然定域轨道,结果与用其它定域化方法得出的基本一致。由于自然定域轨道方法基本上具有内禀定域性质,而计算量明显小于其它定域化方法,可以认为它是有效和方便的。     

定域分子轨道模型——含H、C、N、O有机小分子的研究

应用STO_(-3)G从头算方法和Fostre-Boys定域化分子轨道程序, 我们研究了20多个有机小分子(含H、C、N,O)的定域化分子轨道, 获得了它们的能量和相互作用参数。采用定域分子轨道模型和统一的参数, 对正醇类分子进行了计算, 与光电子能谱数据比较, 得到的电离能的计算结果是相当令人满意的。     

双核锰化合物的定域分子轨道研究

利用ＩＮＤＯ和Ｅｄｍｉｓｔｏｎ－Ｒｕｅｄｅｎｂｅｒｇ定域化方法，计算了Ｍｎ２（μ－Ｃｌ）２（ＣＯ）８和Ｍｎ２（ＣＯ）１０的正则和定域分子轨道，给出了它们的成键图象，讨论了Ｍｎ－Ｍｎ原子间相互作用以及不同方式配位的ＣＯ化学键和几何结构的关系。     

非正交定域分子轨道及其Fock能量的传递特性

应用 Lennard-Jones 和 Pople 提出的求定域分子轨道(简称为 LMO)的方法,可以获得对应于分子化学键和原子内层空间的一组正交化的 LMO。但为了保持正交化,必然使这些轨道不很定域。同时,正交化的 LMO 反映分子中原子轨道的杂化类型,只能按同系物分子寻求传递性的 LMO。因此,放弃正交化条件的限制,寻求更定域的,因而更传递的 LMO 是一件有意义的工作。     

E-R分子轨道定域化方法与分子结合能

自编了E-R^[1]定域化计算程序,对HF、LiH、BH、Li₂、Be₂、CO和CH₄等分子作了计算。确定的酉变换算出的定域分子轨道正确。计算了各分子的定域分子轨道能量ε、加和能E′和结合能E″^[2],得到三点结论。     

苯的XPS Shake-up谱的理论研究——对称和非对称的CNDO/S-CI计算

用不同方法对苯的XPS Shake-up谱进行了CNDO/S—CI计算,一种是用对称化(D_(6h))的基函数进行实芯隙(core—hole)离域模型的非等价核近似的计算,一种是在等价核近似下用实芯隙定域模型的约化对称(C_(2v))和非对称化进行计算。所有计算只考虑单电子激发的组态。在这些条件下,离域模型的结果要比定域模型的好。     

SUBCELLULAR LOCALIZATION OF PORPHYRINS USING CONFOCAL LASER SCANNING MICROSCOPY

The in vitro subcellular distribution patterns of 10 porphyrins, varying in hydrophobicity and charge, were studied using confocal laser scanning microscopy on two cell lines (V79 and C6 glioma cells) for incubation times up to 24 h. All of the porphyrins were taken up rapidly by both cell lines and distinct classes of subcellular distribution patterns were observed: general cytoplasmic staining; localization in lysosomes (usually associated with general cytoplasmic staining); localization in mitochondria (and general cytoplasmic staining); localization in mitochondria with subsequent uptake into lysosomes. Structure-localization relationships which have emerged are that porphyrins with dominantly cationic side chains localize in mitochondria, whereas those with a more anionic character tend to localize in lysosomes.     

TRANS-MEMBRANE LOCALIZATION OF REACTION CENTER PROTEINS IN RHODOPSEUDOMONAS SPHAEROIDES CHROMATOPHORES

Abstract— Rhodopseudomonas sphaeroides NCIB 8253 chromatophores were treated with trypsin and pronase to determine which of the three reaction center subunits was exposed at the outer surface and susceptible to digestion. Trypsin (37°C, 60min) produced no detectable digestion of any subunit, based on SDS polyacrylamide gel electrophoresis analysis. Pronase (37°C, 60min) digested the H (28 kdalton) subunit but left the M (22 kdalton) and L (19 kdalton) subunits intact. We conclude that the H subunit is significantly exposed at the outer chromatophore surface but that the M and L subunits are probably not externally exposed. Chromatophores which had been pronase-treated were fully photochemically active, as measured by light-induced carotenoid bandshift at 522 nm. The H subunit is apparently unnecessary for primary photochemistry in situ.     

IDENTIFICATION AND LOCALIZATION OF PHOTOALKYLATED BASES IN DNA FRAGMENTS

Abstract— Antibodies directed toward 8-(2-hydroxy-2-propyI)-deoxyguanosine-5'-monophosphate (8-hpdGMP), a product of the photoalkylation of deoxyguanosine-5'-monophosphate with 2-propanol, were shown to be highly specific and sensitive in detecting 8-hpdGMP residues in photoalkylated DNA.
The antibodies were further used to determine the distribution of modified guanine residues in DNA. The irradiated DNA was digested with restriction enzymes and the fragments obtained were separated electrophoretically and blotted onto diazotized paper. The covalently bound DNA fragments were probed with the antibodies and then with ¹²⁵I Staphylococcus aureus protein A. These experiments indicate a non-random distribution of modified guanine residues in øX174 RF DNA molecules.     

LOCALIZATION OF ULTRA WEAK PHOTON EMISSION IN PLANTS

Abstract— Ultraweak light emission and light piping of cucumber seedlings was shown using two-dimensional photon imaging via an ultrahigh sensitive photon counting image acquisition system. A macroscopic localization of the photon generating region was achieved.     

UPTAKE KINETICS AND INTRACELLULAR LOCALIZATION OF HYPOCRELLIN PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY: A CONFOCAL MICROSCOPY STUDY

Hypocrellins are naturally occurring compounds with photosensitizing properties in biological systems. We have prepared synthetic derivatives of hypocrellin B, which have promise as photosensitizers in the clinical application of photodynamic therapy. The intracellular localization and uptake kinetics of hypocrellin B and several selected hypocrellin congeners were determined semiquantitatively by fluorescence confocal microscopy in monolayer cultures of EMT6/Ed murine tumor cells. Each compound had unique uptake kinetics. Although no compound tested to date has demonstrated nuclear labeling, most could be detected in lysosomes, Golgi, endoplasmic reticulum and, to a minor extent, in cellular membranes. No two compounds gave identical labeling distributions. The differences are assumed to originate in physicochemical properties characteristic of each compound, which may ultimately impact upon the primary modality of phototoxicity.     

SUBCELLULAR LOCALIZATION OF HEMATOPORPHYRIN DERIVATIVE IN BLADDER TUMOR CELLS IN CULTURE

Mitochondria have been implicated as a primary subcellular site of porphyrin localization and photodestruction. However, other organelles including the cell membrane, lysosomes and nucleus have been shown to be damaged by hematoporphyrin derivative (HpD) photosensitized destruction as well. In this study we attempted to follow the translocation of the fluorescent components of HpD in human bladder tumor cells (MGH-U1) in culture to determine whether specific subcellular localization occurs over time. Following a 30 min exposure to HpD the cellular fluorescence was examined immediately and 1, 2, 4, and 24 h after HpD removal using fluorescence microscopy and an interactive laser cytometer. The in vitro translocation of dye appeared to be fairly rapid with fluorescence present at the cell membrane and later (1-2 h) within a perinuclear area of the cytoplasm. To determine whether HpD had become concentrated into a specific subcellular organelle, these fluorescence distribution patterns were compared with fluorescent marker dyes specific for mitochondria, endoplasmic reticulum and other membranous organelles. The HpD fluorescence did not appear to be as discrete as the dyes specific for mitochondria or endoplasmic reticulum but appeared similar to the diffuse cytomembrane stain. Finally, the interaction between the fluorescent components of HpD and the cellular constituents was evaluated using a "fluorescence redistribution after photobleaching" technique. The results indicated that the mean lateral diffusion for HpD in MGH-U1 cells was 1.05 x 10(-8) cm2/s, a rate closer to that of lipid diffusion (10(-8)) than that of protein diffusion (10(-10)).(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of some integral methods

The integral methods proposed to compute the kinetic parameters of heterogeneous reactions under non-isothermal conditions are usually worked by the help of the least squares method and the obtained correlation coefficient is taken as a criterion to choose the best integral method.An analysis of several experimental data by mean of three different integral methods was performed by us and the results pointed out that this criterion, by itself, is not enough to provide reliable information on the kinetic parameters.It appears, thus, that the use of an integral method or another is a simple matter of researcher's choice.

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Zusammenfassung Integrationsmethoden zur Berechnung kinetischer Parameter von heterogenen Reaktionen unter nicht isothermen Bedingungen werden im allgemeinen nach der Methode der kleinsten Quadrate erarbeitet und der ermittelte Korrelationskoeffizient dient als ein Kriterium für die Auswahl der besten Integrationsmethode.Mittels drei verschiedenen Integrationsmethoden wurde eine Analyse verschiedener experimenteller Daten durchgeführt. Die Ergebnisse zeigen, daß dieses Kriterium allein nicht ausreicht, um ausreichende Informationen über die kinetischen Parameter zu liefern.Es scheint deshalb, daß die Verwendung der einen oder anderen Integrationsmethode einfach eine Wahl des Anwenders darstellt.

     

Comment on “Analytical evaluation for two-center nuclear attraction integrals over Slater type orbitals by using Fourier transform method” by S. ?zcan and E. ?ztekin (J. Math. Chem. DOI 10.1007/s10910-008-9398-z)

S. ?zcan and E. ?ztekin, (J. Math. Chem. doi:) published formulas for evaluating the two-center nuclear attraction integrals over Slater type orbitals. It is shown that the analytical relations for these integrals through the expansion coefficients of the electron charge density for the one-center case and the overlap integrals presented in Sect. 3 of this work can easily be derived by means of a simple algebra from the formulas published in our papers (I.I. Guseinov, J Mol Struct (Theochem) 417:117, 1997; J Math Chem 42:415, 2007 and B.A. Mamedov, Chin J Chem 22:545, 2004). It should be noted that the formulas of overlap integrals presented by E. ?ztekin et al., in previous paper (E. ?ztekin, M. Yavuz, Ş. Atalay, J Mol Struct (Theochem) 544:69, 2001) for the calculation of two-center nuclear attraction integrals also are obtained from our papers (see Comment: I.I. Guseinov, J Mol Struct (Theochem) 638:235, 2003).     

Kinetic analysis of thermogravimetric data obtained under linear temperature programming—a method based on calculations of the temperature integral by interpolation

A new technique, called interpolation method, with general application in the kinetic analysis of processes studied by thermogravimetry (TG) under linear temperature programming is developed. It is based on the linear relationship, with slope 1, between log g() and log I(γ, θ) for the appropriate kinetic function, where I(γ, θ) is the normalized temperature integral, θ the normalized temperature (θ=T/T₀) and γ a dimensionless activation energy (γ=E/RT₀). Values of log I(γ, θ) are calculated by linear interpolations in a pre-built table. This method can easily be programmed and implemented in a personal computer, where the results (kinetic parameters and quality of regressions for the kinetic functions considered) are typically obtained in a very short time. The method is validated by analyzing different simulated thermogravimetric curves and comparing the results with those determined with some classic methods taken from the literature. In addition, the results are compared with the values obtained by a similar method, also developed and explained in this paper, which involves the evaluation of all the values of the temperature integral by numerical integration, therefore, demanding a much larger calculation time. The interpolation method is found to be more accurate than other published methods, particularly in the case of thermogravimetric curves corresponding to processes with low activation energies. The results obtained are always similar to those determined by the integration method, which is taken as reference. Application of the technique to experimental data for various types of reactions shows that the results are in agreement with the published parameters and kinetic laws.     

Non-isothermal kinetics in solids

The integral methods, which are obtained from the various approximations for the temperature integral, have been extensively used in the non-isothermal kinetic analysis. In order to obtain the precision of the integral methods for the determination of the activation energy, several authors have calculated the relative errors of the activation energy obtained from the integral methods. However, in their calculations, the temperature integral at the starting temperature was neglected. In this work, we have performed a systematic analysis of the precision of the activation energy calculated by the integral methods without doing any simplifications. The results have shown that the relative error involved in the activation energy determined from the integral methods depends on two dimensionless quantities: the normalized temperature θ=T/T ₀, and the dimensionless activation energy x ₀=E/RT ₀ (where E is the activation energy, T is the temperature, T ₀ is the starting temperature, R is the gas constant).