延胡索乙素在兔体内脏的分布滞留研究

本文为了对药物在脏器中的分布滞瘤问题进行研究，首先给家兔口服元胡水煎液，２４ｈ之后，再采用高灵敏的胶束荧光法，对主要脏器中所含延胡索乙素进行测定，所测心肝、肾中的含量分别为０．０７９８μｇ／ｇ，１．４０μｇ／ｇ，５．１４μｇ／ｇ，效果良好。     

Quenching interactions and nonexponential decay: tryptophan 138 of bacteriophage T4 lysozyme

Site-directed mutagenesis has been used to prepare variants of bacteriophage T4 lysozyme that contain only one tryptophan residue at position 138 and to change the residues in the immediate environment of this buried residue. Replacement of glutamine-105 by alanine results in a 2.7-fold increase in fluoresence quantum yield and converts the fluorescence decay from a highly nonexponential form to a single-exponential decay. This is atributed to electron transfer quenching of tryptophan-138 fluorescence by glutamine-105. Replacemeent of alanine-146 by threonine results in a 1.6-fold decrease in fluorescence intensity, indicating enhanced quenching by glutamine-105; replacement of glutamine-105 by alanine in this species results in a 5-fold in crease in fluorescence intensity. The interpretation of the nonexponential decay of the glutamine-105-containing species is discussed in terms of reversibility of the quenching process.     

An investigation of squaraines as a new class of fluorophores with long-wavelength excitation and emission

We present an overview of our investigation of the spectral properties and photostabilities of squaraine derivatives. The objective was to identify long-wavelength probes with reasonable quantum yields, reasonably long lifetimes, and good photostabilities for use in fluorescence-based assays and/or imaging. Both symmetrical and unsymmetrical squaraines were studied. Based on this investigation the most suitable probes for use in a biological application were found to be the symmetrical indolenine derivatives of the squaraines, which display the highest photostability. Importantly, their quantum yields and lifetimes increase significantly upon covalent and noncovalent binding to proteins (bovine serum albumin, antibodies), demonstrating the usefulness of the squaraines as long wavelength probes. The squaraine absorbance maxima between 630 and 650 nm allows the use of the new commercially available 635- and 650-nm diode lasers.     

两种补硒产品中硒的测定及其生物可利用性评估

目的:测定富硒茶叶和“黄金搭档”两种补硒产品中的硒含量,评估其生物利用性.方法:用分子荧光法于发射波长520 nm处测定样品(茶叶、“黄金搭档”维生素片、茶汤、肠模拟透析液)硒含量,以体外消化透析法测算茶汤和“黄金搭档”维生素片中硒的生物可接受率,以此评估硒的生物利用性.结果:硒标准曲线的R2为0.9989,RSD为0...     

Chelometric Titration of Trace Amounts of Metal Ions Employing Instrumentally Measured Fluorometric Endpoints

Abstract

Trace amounts of metal ions which form stable complexes with EDTA at pH 4.0 have been titrated using morin as a fluorometric indicator. Back ticration of excess EDTA with Ga(III) and instrumental endpoint detection were employed for the determination of ions which are not normally determined by fluorometric methods. The continuous monitoring of the change in the fluorescence intensity throughout a deration also allowed mixtures of Ga(III) and In(III) to be determined when TTHA and EDTA were employed as double titrants.     

Studies on the Toluidine Blue Dimer as a Fluorescence Probe for Protein Assays

Abstract

A spectrofluorometric method was developed for the determination of total serum protein by exploring toluidine blue (TB) as the fluorescence probe. The fluorescence intensity of TB at 648 nm was significantly quenched in the presence of sodium dodecylbenzene sulfonate (SDBS) by forming a dimer of the dye, which can afterwards reconvert to monomer when proteins were added accompanied by the recovery of the fluorescence. This might be attributed to the modulated transferring of the dimer‐monomer equilibrium of TB in the anionic surfactant caused by the addition of protein. A linear calibration graph was obtained in the range of 0.5–50 mg/l BSA, with a detection limit of 0.15 mg/l and a RSD of 1.3% (n=11, 5.0 mg/l BSA). Total proteins in human serums were analyzed by using the present procedure and the results agreed well with those obtained by the Biuret method.     

On the Stability of Isoindole-Type Fluorophores Derived from O-Phthalaldehyde,Primary Amino Compounds and Thiols

Abstract

o-Phthalaldehyde (OPA), a primary amino compound and a thiol react to produce a ternary isoindole-type fluorophore. The effect of the structure of the constituent amino compound on the chemical stability of isoindole fluorophores was investigated. The amino compounds with steric hindrance around the -NH₂ group such as L-tryptophan and L-Dopa exhibited a marked stabilization effect on the isoindole fluorophores. By using OPA and L-typtophan as reagents, a procedure was established for the fluorometric determination of thiols which permitted the determination of 2 nmol of L-cysteine (CySH). The possible mechanism for the instability of isoindole accelerated by increasing concentration of OPA was also discussed.     

Asymmetrical Distribution of Intrinsic Fluorescence Lifetimes in Proteins

Dynamic fluorescence measurements of proteins in solution are often interpreted in terms of continuous distributions of lifetimes, which reflect the intrinsic structural heterogeneity of these systems. In several cases a single Gaussian or Lorentzian symmetric distribution has been used to fit the data. In this paper we describe a new nonsymmetric Lorentzian function which contains three free parameters (the center, the left, and the right widths) like the double-discrete exponential model (the two lifetimes and one preexponential factor). Simulated data in the frequency domain have been used to compare the fits obtained with these different approaches, introducing a new parameter, , which quantitatively measures the asymmetry of the distribution or the ratio of the two preexponential factors, in the continuous and discrete models, respectively. Real measurements of a mixture of independent fluorophores, as well as of protein fluorescence decays, have also been performed and analyzed in terms of the new asymmetric function. The data have also been fitted with traditional discrete methods (such as the two- and the three-exponential decay) and with another asymmetric function, namely, the skewed Gaussian distribution.     

Measurement of Sectional Profile of a Cylinder using a Sinusoidally Vibrating Light with Sinusoidal Intensity

A method for accurately measuring a sectional profile of a cylinder is proposed in which a sinusoidally vibrating sinusoidal grating is used to generate a sinusoidally vibrating sinusoidal intensity distribution. A light coming from the top point of the cylinder surface is extracted with an optical system to make an image of this point. A sectional profile of the cylinder is measured by detecting a phase of a time-varying signal contained in the image intensity at a position where the amplitude of the signal is maximum. Detection of the amplitude and the phase is carried out easily and exactly.     

High performance liquid chromatography/video fluorometry. Part II: Applications

A video fluorometer is used as a detector for HPLC to characterize highly complex samples. Data selection and evaluation techniques are discussed so as to speed the spectral identification process. Several well-known polynuclear aromatic hydrocarbons are found in the samples.