荧光光谱法研究核黄素与核黄素结合蛋白的相互作用

运用荧光光谱研究了核黄素与核黄素结合蛋白的相互作用,并探讨了两者间的结合类型、结合常数、结合过程中热力学参数和能量转移。结果表明:核黄素结合蛋白内源荧光的猝灭是由于核黄素与蛋白质之间形成复合物,并符合静态猝灭机理。298,308,318K下核黄素与核黄素结合蛋白的结合常数分别为:5.35×108,1.54×108,0.56×108 L.mol-1。热力学数据表明核黄素与核黄素结合蛋白之间主要作用力为氢键和范德华力。Frster能量转移理论确定了核黄素与核黄素结合蛋白的作用距离与能量转移效率分别为0.70nm与0.39。利用同步荧光光谱研究了核黄素结合蛋白与核黄素结合过程中构象的变化。     

Investigation on the interaction of glipizide with bovine hemoglobin by spectroscopy and molecular docking

This study aims to investigate the interaction between glipizide and bovine hemoglobin using fluorescence quenching, circular dichroism spectroscopy in various temperatures (293, 303, and 310?K) and molecular docking methods. The results demonstrated that glipizide could cause strong fluorescence quenching of bovine hemoglobin by a dynamic quenching mechanism, during which the hydrophobic interaction played a dominant role in this system. The order of magnitude of binding constant is 10⁴, and the number of binding site in the system was close to 1. It also showed that tyrosine residues and tryptophan residues were both involved in the binding of glipizide with bovine hemoglobin, and was closer to the later. Circular dichroism spectra revealed that the conformation of bovine hemoglobin was changed during the binding reaction. The interaction of the system was studied by both spectroscopic method and molecular docking simulation, and the conclusions are consistent.     

Study on Ion-dynamics in solids by hole burning spectroscopy

The importance of hole burning spectroscopy for studying elementary migration processes of ions in superionic conductors is being discussed using two examples. In β″-alumina, the potential energy for the conduction of ions along the conduction path, as obtained from the analysis of the results of hole burning spectroscopy, showed that there are two different bare-potentials along the ionic conduction path. One of them is higher than the activation energy for ionic conductivity. This result gives direct evidence that an ionic interaction among the conducting ions plays an important role for ion migration in β″-alumina. In YSZ with various concentration of Y₂O₃, we have observed persistent holes in Pr³⁺ ions doped samples. Their disordered nature will be discussed using the bandwidth considerations. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002.     

Visualization of in-plane dispersion of hole subbands by photoelectron spectroscopy

The in-plane dispersion of the hole subband (HSB) in a Si quantum well is obtained for the first time by applying angle-resolved photoemission spectroscopy and surface science techniques. The entire shape of the HSB over a wide ranged wave vector, including admixing of heavy and light hole subbands around the crossing point and the camelback structure inducing negative effective mass, is visualized directly. Energy separations between the subbands are quantitatively explained.     

Nonlinear plasmon-photon interaction resolved by k-space spectroscopy

Metallic nanostructures support extreme localization and enhancement of optical fields via surface-plasmon (SP) resonances. Although SP are associated with giant enhancements of nonlinear phenomena such as second-harmonic generation (SHG), the role of SP in the process, whether as a field-enhancing catalyst or as a quasiparticle converted in the interaction, has remained experimentally elusive. We demonstrate how k-space spectroscopy can distinguish between the plasmonic and photonic SHG processes that occur in a metal nanofilm when it is optically driven via the Kretschmann geometry. The results revealed a nonlinear interaction where two SP annihilate to create a second-harmonic photon. This knowledge has implications for realizing the inverse process, plasmonic parametric down-conversion, which could act as a coherent source of entangled SP pairs.     

Low-temperature spectroscopy of organic molecules in solids by photochemical hole burning

Characteristic features of photochemical hole-burning (PHB) in the impurity spectra of low-temperature solids and PHB applications in molecular spectroscopy are considered. The evolution of a no-phonon hole and a phonon sidehole in excitation and fluorescence spectra is analysed on the basis of model calculations. Some more complex models for PHB are considered, which take into account reverse reactions, the optical thickness of the sample, the inhomogeneous dispersion of both homogeneous linewidths and transition energies of the photoproduct and quasi-static impurity-impurity interactions. The effects of PHB on fluorescence line narrowing are discussed. By PHB homogeneous linewidths of purely electronic and vibronic no-phonon lines in the spectra of some porphine and phthalocyanine derivatives in various matrices are measured and their temperature dependence is studied. The latter is found to be essentially different in polycrystalline and glassy matrices. Line-broadening mechanisms are discussed. By PHB the existence of an inhomogeneous distribution of vibrational frequencies in molecular impurities is established. The applications of PHB in the studies of photochemical reactions in solid solutions of phthalocyanine derivatives and tetracene are regarded and the mechanisms of these reactions are discussed. The results obtained by PHB for chlorophyll and its derivatives are presented.     

Black hole spectroscopy via adiabatic invariance

During the last years, one had to combine the proposal about how quasinormal frequencies are related with black holes and the proposal about the adiabatic invariance of black holes in order to derive the quantized entropy spectrum and its minimum change for several black holes. In this Letter we exclusively utilize the statement that the black hole horizon area is an adiabatic invariant and derive an equally spaced entropy spectrum of a black hole with its quantum to be equal to the one given by Bekenstein. Interestingly, in our approach no concept of quasi-normal mode is needed.     

Investigation of the interatomic interaction in immunoglobulin G fragments via X-ray photoelectron spectroscopy

The chemical structure of Fc and Fab fragments of immunoglobulin G (IgG) is studied by means of X-ray photoelectron spectroscopy. The purpose of studies is to apply the given technique in determining the chemical composition of fragments obtained via papain hydrolysis. Fragments with specified biological properties can be used as an effective agent in a vaccine developed for the treatment of human rheumatoid arthritis, which is prepared from the IgG Fc fragment.     

Theoretical interpretation of 1s hole satellite peaks of formaldehyde

Variable temperature studies of the photoelectron (PE) spectra of the title compounds lead to the assignment of the observed bands to a molecular orbital energy sequence which is the same for all three compounds; some of the observed fine structure in the SiF₄ spectrum is due to the presence of “hot bands.”     

Investigation of TiC-C coatings by X-ray photoelectron spectroscopy

Titanium carbide-based coatings deposited by arc-technology in C₂H₂/Ar atmosphere were studied by X-ray photoelectron spectroscopy. It was found that, in addition to the cubic phase of TiC _x O _y oxycarbide, the films contain carbon in the amorphous, presumably graphite-like state. In carbon C1s spectra, bands at 282.0, 284.4, and 286.0 eV correspond to the TiC _x state, amorphous carbon, and C-C bonds, respectively. The maximum at 283.0 eV was interpreted as the C state in titanium carbide nanoforms, i.e., Ti₁₄C₁₃ clusters or Ti₈C₁₄ carbohedra. The phase ratio was varied by coating deposition conditions, i.e., TiC/a-C deposition by Ti cathode sputtering in C₂H₂/Ar, and composite Ti/C target sputtering in Ar and C₂H₂/Ar. When using the Ti cathode and C₂H₂/Ar gas mixture, the ratio of carbide and amorphous a-C phases was estimated as 1: 1; the surface layer ～15 nm thick was enriched with amorphous carbon. It was assumed that TiC/a-C composite coatings with an additional a-C film on the surface would have an increased stability in reaction media and good biocompatibility.     

Investigation of the mechanism of the interaction of trimethylhalosilanes with a hydrated silica surface by the method of IR spectroscopy

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 934–938, June, 1991.     

Transport spectroscopy of Kondo quantum dots coupled by RKKY interaction

We develop the theory of conductance of a quantum dot which carries a spin and is coupled via RKKY interaction to another spin-carrying quantum dot. The found dependence of the differential conductance on the bias and magnetic field at a fixed RKKY interaction strength may allow one to distinguish between the possible ground states of the system. Transitions between the ground states are achieved by tuning the RKKY interaction, and the nature of these transitions can be extracted from the temperature dependence of the linear conductance. The feasibility of the corresponding measurements is evidenced by recent experiments by Craig et al.     

Ar 3s, 3p satellite lines studied by fluorescence spectroscopy

The fluorescent radiation emitted by the Ar 3s, 3p satellite states (observed by photoelectron spectroscopy) has been recorded in the wavelength range between 400 and 780 Å with an energy resolution ranging from 50 to 100 mV. The fluorescence was stimulated by use of undispersed synchrotron radiation.     

Investigation of radiosterilization feasibility of sulfamethoxazole by ESR spectroscopy

In the present study, the spectroscopic features of the radiolytic intermediates that were produced in gamma-irradiated (5, 10, 25 and 50?kGy) sulfamethoxazole (SMX) have been investigated by electron spin resonance (ESR) spectroscopy and the radiation sterilization feasibility of SMX by ionizing radiation was examined. Gamma-irradiated SMX exhibited a complex ESR spectrum consisting of 13 resonance lines where spectral parameters for the central resonance line were found to be g?=?2.0062 and ΔH_pp?=?0.6?mT. The radiation yield of SMX was calculated to be relatively low (G?=?0.1) by ESR spectroscopy and no meaningful difference was observed in the comparison of unirradiated and 50?kGy gamma irradiated SMX by the Fourier transform infrared (FT-IR) technique, confirming that SMX is a radioresistive material. Although SMX could not be accepted to be a good dosimetric material, the identification of irradiated SMX from the unirradiated sample was possible even for the low absorbed radiation doses and for a relatively long time (three months) after the irradiation process. Decay activation energy of the radical species, which is mostly responsible for the central intense resonance line, is calculated to be 45.15?kJ/mol by using the signal intensity decay data derived from annealing studies. Four radical species with different spectroscopic properties were accepted to be responsible for the ESR spectra of gamma-irradiated SMX, by simulation calculations. It is concluded that SMX and SMX-containing drugs can be sterilized by gamma radiation and ESR spectroscopy is an appropriate technique for the characterization of these induced radical intermediates during the gamma irradiation process of SMX. Toxicology tests should also be done for its safe usage.     

Investigation on RF styrene plasma by emission spectroscopy

In order to gain an insight into the processes in an RF styrene plasma, gas phase plasmas were investigated by emission spectroscopy. The plasma reactor was a bell-jar-type chamber with two parallel plate electrodes. The measurement of plasma emission spectra was made with axial resolution. The correlations among the emission intensities of CH and C₄H₂⁺ species, the polymer deposition rate and the polymeric structure of the deposited films were studied. The proposed analysis showed that the gas flow pattern in the plasma reactor, and the difference in collisions between styrene monomer molecules and energetic free electrons occurring in the plasma region and RF sheath, made the fragments and ions produced change in the different regions, resulting in a change in polymeric structure and deposition rate of the polymer films. With increasing distance between the substrate position and the lower electrode, the deposition rate and the concentration of phenyl groups both at the polymer surface and in the bulk decreased     

Electron—hole liquid in CdS crystals as revealed by non-equilibrium transmission spectroscopy

Transmission measurements in the excitonic region on thin platelets under high N₂ laser excitation showed the disappearance of exciton absorption into a strong absorption continuum. The low energy edge of the latter — about 12 meV below the free exciton A_n=1 — coincides with the high energy edge of the gain spectrum of stimulated emission under similar excitations. These results favour the assumption of electron—hole drop formation with a ground state of the e-h-pair about 12 meV below A_n=1.