Dependence of Fluorescent Ability on Efficiency of Intersystem Conversion in Psoralens

Results of theoretical research for seven psoralen molecules: psoralen, 5-methoxypsoralen, 8-methoxypsoralen, angelicin, pseudoisopsoralen, isopseudopsoralen, and allopsoralen, are presented. Schemes of photophysical processes in psoralens based on quantum chemical calculation by the INDO method are analyzed. Effects of isomerism and methoxysubstitution on the energy level diagram are demonstrated. The rate constants of intersystem and internal conversions are calculated. We obtained rather high intersystem conversion constant that influences on the fluorescent yield of psoralens.     

Ultraviolet spectra of coumarins and psoralens

The π → π^∗ transitions of coumarins in the ultraviolet region have been described on the basis of fluorescence polarization, dichroic spectra, and SCF MO CI results. The two lowest π → π^∗ transitions in coumarin, 4-hydroxy-coumarin, and psoralen were found to be polarized nearly parallel to each other, probably along the long molecular axis. The two lowest π → π^∗ transition moments in 8-methoxypsoralen were found to be oriented with a substantial angle between them, in contrast to the case of coumarin and psoralen. It was not possible to identify any n → π^∗ bands as they are probably obscured by the strong π → π^∗ bands.     

Identification of psoralen loaded PLGA microspheres in rat skin by light microscopy

Drug delivery systems involving the use of polymers are widely studied and discovery of biocompatible polymers has become the focus of research in this area. Psoralen loaded poly(DL-lactide-co-glycolide) (PLGA) microspheres to be used in PUVA therapy (psoralen and UVA irradiation (ultraviolet A, 320-400 nm) of psoriasis were identified in paraffin sections by histological analysis. The psoralen loaded PLGA microspheres were prepared using the solvent evaporation technique. They were spherical and possessed an external smooth surface as observed by scanning electron microscopy (SEM) analysis. This study describes a modification in the routine preparation of microsphere samples for examination by light microscopy. The changes involved fixative agents and/or stains allowing the identification of microspheres containing a non-fluorescent material. The preservation and identification of microspheres in tissues for histological processing in paraffin was greatly improved by these modifications as proven by our results.     

Spectral and luminescent properties of sensitizers based on psoralen substitutes

Psoralens (furocoumarines) are photosensitizers of vegetative origin increasing the sensitivity of biological objects to near-ultraviolet radiation (UV-A, 320–400 nm). In the present work, the influence of substitution on the energy level diagram is considered for the first element of the series-psoralen. The absorption and fluorescence spectra are investigated with the use of an SM-2203 spectrofluorimeter, and theoretical calculations are carried out. In addition, the results obtained are compared with the calculated and experimental results of other authors. The employed method of intermediate neglect of differential overlap (INDO) yields such parameters as an oscillator force, nature and energy of the transition, positions of triplets and singlets, etc. The geometry is optimized by the semi-empirical PM3 method of the program Hyperchem 6.03. A comparison of the calculated results for the examined compounds demonstrates that after the substitution, the absorption spectra are shifted toward the red range. The lower excited singlet of the 21,22-dimethyl-10,11-cyclohexylpsoralen compound lies higher than that of psoralen and 10,11-phenyl-21,22-cyclohexylpsoralen; it is located at 332 nm. The absorption spectra from the excited states undergo a bathochromic shift after the substitution. The most intensive T-T absorption bands are also indicated in this work. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 43–49, July, 2008.     

Spectral features of formation of H-bonded complexes in coumarins and psoralens

Spectral features of H-bonded complexes formed by molecules of coumarin 1 and psoralen with methanol (1∶1) have been studied by the methods of quantum chemistry [a semiempirical method with intermediate neglect of differential overlap (INDO) with special spectroscopic parametrization] and by the method of electrostatic potential (MEP). The MEP using INDO wave functions was used to find ways of approach to the methanol molecules and the structure of H-bonded complexes. The direction of spectral shifts of the different (with respect to the orbital nature) electronic excited states in the formation of the complexes and ways of approach to the solvent molecules in the formation of the first solvation shell are established. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 88–92, March, 1999.     

Preparative separation of methoxy derivatives of psoralen using supercritical-fluid chromatography

A method of separation of a mixture of three methoxy derivatives of psoralen—bergapten, xanthotoxin, and isopimpinellin—has been developed. The performed screening allows it to be concluded that it is appropriate to separate them by normal-phase supercritical-fluid chromatography (SCF). Analysis of mechanisms of separation of methoxypsoralens (MOPs) showed that, on all silica gel-based sorbents with immobilized polar groups, except for 2-ethylpyridine and pentafluorophenyl sorbents, absorption occurs by the same retention mechanism. A possible explanation for the observed regularities of elution of the related MOPs has been suggested. In the case of pentafluorphenyl sorbent, π-electronic intermolecular interactions play a key role in separation. Presumably the same effect is responsible for the particular order of elution observed when the 2-ethypyridine sorbent was used.     

类呋喃香豆素的合成与DNA的结合及细胞毒性研究

呋喃香豆素类化合物无紫外光辅助照射时抗肿瘤活性低,为提高其正常情况下的抗肿瘤活性,依据“最小嵌入”假说对其进行结构改造。把呋喃香豆素结构中的呋喃环拆分出来,使其与香豆素由原来稠环相并的结合方式转变为通过化学键相连,得到合成简化的类呋喃香豆素。利用DNA熔解曲线、吸收光谱、荧光发射光谱和粘度测试考察了这些类呋喃香豆素与DNA的相互作用。综合DNA溶解曲线、光谱法和粘度测试的结果,推测除目标产物5b是一DNA嵌入剂外,其他化合物嵌入DNA能力下降,5a以部分嵌入方式与DNA结合,5c和5d是通过极为少见、鲜有报道的“桥型结构”与DNA相结合。利用“罗丹明B蛋白染色法”考察了目标化合物的体外细胞毒性,测试结果显示,与对照品补骨脂素相比这些化合物对肿瘤细胞体外生长抑制作用明显增强,并且非经典嵌入结合的化合物活性增强更明显。该研究拓展了“最小嵌入”假说的应用范围,同时为呋喃香豆素类化合物结构改造提供了依据。     

Photodynamic activity of different dyes

Photodynamic therapy (PDT) is a technique for inducing tissue damage with light irradiation of a drug selectively retained in malignant tissue. Many kinds of compounds are known with photosensitizing properties including dyes, drugs, cosmetics, chemicals, and many natural substances. There are different classes of sensitizers used for medical purposes such as tetrapyrroles (porphyrins and derivatives, chlorophyll, phylloerythrin, phthalocyanines), tricyclic dyes with different meso-atoms (acridine orange, proflavine, riboflavine, methylene blue, fluorescein, eosine, erythrosine, rose bengal), and furocoumarins (psoralen and its methoxyderivatives xanthotoxin, bergaptene). In this work, we performed one comparative cytotoxic study of the photodynamic activity presented by tricyclic dyes (methylene blue, fluorescein and erythrosine) and the commercial Russian photosensitizer Photogem® (hematoporphyrin derivative). For this purpose, three cell lines were used: HEp-2 (tumor cells), VERO and McCoy (nontumor cells), and a yeast strain. The wavelength used for irradiation was 630 nm, the same as used in PDT for medical purposes, since it is in the therapeutic window, i.e., where light can penetrate more into the tissues. The results suggest that Photogem® is more cytotoxic and more photocytotoxic than the studied tricyclic dyes in nontumor and tumor cells. These dyes present less cytotoxicity (around half) in normal cells (dark and light) than in tumor cells. In the experiments with microorganisms, methylene blue presented a better photodynamic effect than Photogem®. These results can be explained by the fact that it is more difficult for Photogem® to penetrate in microorganism membranes than mammalian cell membranes. As for Photogem®, these tricycle dyes present a higher cytotoxicity in tumor cells. These data suggest that methylene blue can be an option in photodynamic inactivation as well as in photodynamic therapy, mainly for superficial lesions.     

The boson transformation and the vortex solutions

The boson transformation, which allows the construction of spontaneously broken solutions with space and/or time-dependent vacuum directly from the translationally invariant ones, is examined in the context of the Higgs mechanism. Both the Lorentz and the radiation gauge are treated in detail. The classical vortex solution is derived by fully quantum field theoretical considerations. The general form of the vortex solution is presented, and various special cases of interest are examined in detail.     

Identity of Elementary Particles and Gauge Interactions

Problems of gauge invariance and identity of elementary particles are examined. The hypothesis that the gauge field charge is related to the possible increase of the entropy is set up. It is demonstrated that the given hypothesis allows fundamental interactions to be interrelated and numerical relations for elementary particle masses to be derived. Theoretical and practical consequences of the examined hypothesis are discussed.     

Ground state structures of a lattice model: honeycomb and tetrahedral lattices

The ground state structures of a lattice model with nearest-neighbor and next-nearest-neighbor interactions were examined by the method of “partitioning” the hamiltonian. This model is Widom's lattice model of microemulsions. Previous analysis had examined only cubic lattices, however the analysis is more general as this paper illustrates.     

Interference and inequality in quantum decision theory

The quantum decision theory is examined in its simplest form of two-condition two-choice setting. A set of inequalities to be satisfied by any quantum conditional probability describing the decision process is derived. Experimental data indicating the breakdown of classical explanations are critically examined with quantum theory using the full set of quantum phases.     

Bulk and edge properties of the Chern-Simons Ginzburg-Landau theory for the fractional quantum Hall effect

The Chern-Simons Ginzburg-Landau theory for the fractional quantum Hall effect is studied in the presence of a confining potential We review the bulk properties of the model and discuss how the plateau formation emerges without any impurity potential. The effect is related to changes, by accumulation of charge, at the edge when the chemical potential is changed. Fluctuations about the ground state are examined and an expression is found for the velocity of the massless edge mode in terms of the confining potential. The effect of including spin is examined for the case when the system is fully polarized in the bulk. In general a spin texture may appear at the edge, and we examine this effect in the case of a small spin-down component. The low-frequency edge modes are examined and a third-order equation is found for velocities which indicates the presence of three different modes. The discussions are illustrated by numerical studies of the ground states, both for the one- and two-component cases.     

Optical and electrical experiments at some transition-metal oxide foil-electrolyte interfaces2

Metal oxide layers formed from transition-metal foils oxidized by heating in air have been examined for their photoelectrolytic response. The metals examined are Y, Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Pt. Weak photoeffects are observed for oxide layers of all of these metals. Sizable light-dependent oxygen gas evolution rates are found in Ti and also in W oxides. The spectral dependence of the oxygen response in these compounds is investigated, and interpretation is given of these experiments.     

Molecular layering of 2D films and superlattices based on II–VI compounds

The method of molecular layering is used to prepare CdS thin films and CdS/ZnS and CdS/CdSe superlattices. The dependence of the exciton photoluminescence on film thickness is studied, and the role of internal strains is examined. The effect of the excitation intensity on the superlattice photoluminescence spectra is examined, manifested in a shift of the emission maximum toward shorter wavelengths when this intensity is increased. Fiz. Tverd. Tela (St. Petersburg) 40, 820–821 (May 1998)     

痕量锗的HG-ICP测定及介质对其测定的影响的研究

采用氢化物发生-电感耦合等离子体原子发射光谱法测定痕量锗的方法,系统地考察了不同酸介质、NaBH₄浓度及共存元素的影响,确定了最佳测定条件。方法的检出限为0.2 ng·mL-1,精密度为0.9%。用环境标准物质进行对照,其测定值均在给定的标准范围之内。并且针对反应介质对锗测定的影响,进行了详尽的研究。     

Orthorhombic Materials and Perfect Lenses

The potential of orthorhombic materials for perfect lenses is theoretically examined.     

The Signs of Frequencies and Phases in NMR

The signs of radiofrequency phases and frequencies used in NMR are examined carefully. Some fundamental problems with current usage are exposed by simple examples. The entire chain of events leading to the NMR spectrum is examined closely, including generation and phase-shifting of the radiofrequency carrier wave, nuclear-spin dynamics in the presence of the radiofrequency field, quadrature detection, signal digitization, post-digitization phase shifting, Fourier transformation, and spectral presentation. Recommendations are given for software modifications which should facilitate the correspondence between pulse programming, spectral presentation, and spin dynamical theory.     

Losses from rotational hysteresis and magnetic anisotropy in single crystals of barium and barium-cobalt hexaferrites

The rotational-hysteresis loss as a function of field has been examined for single crystals of the hexaferrites BaM and Co₂W. Curves for K₁(T) for BaM and K₃(T) for Co₂W have been recorded. The domain structure has been examined on specimens with residual magnetization. The rotational-hysteresis loss for BaM is of the type usual for ferrites, having a negative temperature coefficient below 120 °C, but above this there is an anomalous positive coefficient, which is due to diffusion of Co ions in the rotating field. The initial increase in the loss is related to the dynamics of the domain structure. Heat treatment influences the temperature dependence of the anisotropy constants and hence the rotational hysteresis loss.