Synchronous fluorescence spectra of hemoglobin: A study of aggregation states in aqueous solutions

The synchronous fluorescence spectra of hemoglobin solutions are reported for the first rime. The main fluorescence peaks observed in the spectra are assigned. The effect of the concentration of hemoglobin solution on the spectra is studied. Characteristic fluorescence peaks due to the dimer and tetramer of hemoglobin molecules are recognized. (C) 1998 Academic Press.

The suppression of Ge-132 on the Maillard reaction of BSA by fluorescence spectrum

The fluorescences of BSA and glycosylated BSA were observed respectively. The lambda(cm) of BSA was 340 nm; while the lambda(cm) of glycosylated BSA was 436 nm. Because the fluorescence spectra of them were different greatly, we can observe the suppression of Ge-132 on the Maillard reaction of BSA without any interference of itself. It was showed that the fluorescence intensity of glycosylated BSA increased continuously with the cultured time, Ge-132 may suppress the Maillard reaction of BSA greatly, and the suppressing efficicency would be 32 %. The key site of the Maillard reaction of BSA is free amino groups of alanine residues on N-terminal amino group, besides the epsilon-amino groups of intrachain Lysine residues.

In situ UV-vis and CD thin-layer spectroelectrochemistry study of the electrochemical behavior of L-noradrenaline in alkaline solution

Electrochemical redox behavior of noradrenaline in alkaline solution on a glassy carbon electrode has been investigated by in situ UV-vis and CD spectroelectrochemistry by using a long optical path thin-layer cell. The experimental data were processed by using a double logarithmic method of analysis together with nonlinear regression which confirmed that the first step in both the oxidation of noradrenaline and reduction of noradrenochrome is a two-electron irreversible process governed by an EE mechanism. The kinetic parameters of the electrode reactions, i.e., charge transfer coefficient and the number of electrons transferred, alpha(1)n(1) = 0.11 and alpha(2)n(2) = 0.23, formal potentials modified with kinetics, E-1(0') = 0.65 (+/- 0.01) V and E-2(0') = 0.72V and standard rate cnstants, k(1)(0) = 7.0(+/-0.5)x10(-5) cm s(-1), for the first and second steps in the oxidation process of noradrenaline, and similarly, alpha(1)n(1) = 0.33, alpha(2)n(2) = 0.58, E-1(0') = 0.37(+/-0.01) V, E-0' = -0.25 (+/-0.01) V and k(1)(0) approximate to k(2)(0) = 1.06 (+/-0.05)x10(-4) cm s(-1) for the first and second steps in the reduction process of noradrenochrome were also determined.

Effect of urea on synchronous fluorescence spectra and electrochemical behaviour of cytochrome c

The changes of the synchronous fluorescence spectra and the electrochemical behaviour of cytochrome c with the urea concentration are studied. It has been found that with the increase of urea concentration, there occur sequentially the deaggregation of cytochrome c molecules, the increase of exposure extent of the heme group to the solvent, the disruption of Fe-S bond of the heme group and the change in the electrochemical behaviour of cytochrome c. It is suggested that the reason why the electrochemical reaction of cytochrome c is irreversible is that cytochrome c molecules exist in the concentrated solution as oligomers which are electrochemically inactive.

THE EFFECT OF SOLUTION PH ON SYNCHRONOUS FLUORESCENCE-SPECTRA OF CYTOCHROME-C SOLUTIONS

Synchronous fluorescence spectra of cytochrome c solutions were studied. It was found that synchronous fluorescence spectra of tyrosine and tryptophan residues in cytochrome c molecules can be separated using different wavelength intervals. The changes in synchronous fluorescence spectra of cytochrome c solutions with the solution pH are different from that of free tyrosine and tryptophan and reflect the pH-induced conformational transitions of cytochrome c molecules. (C) 1995 Academic Press, Inc.

STUDIES ON STATES OF CYTOCHROME-C MOLECULES IN AQUOUS SOLUTIONS USING SYNCHRONOUS FLUORESCENCE SPECTROSCOPY

The states of cytochrome C molecules in aquous solution were studied with synchronous fluorescence spectroscopy, It was found that the synchronous fluorescent spectra of cytochrome C were contributed by tyrosine and tryptophan residues separately at Delta lambda = 20 nm and Delta lambda = 80 nm, The peak position in synchronous fluorescent spectra of tyrosine residues in cytochrome C molecule does not change with its concentration, but that of tryptophan residue changes with its concentration, Only one peak at 340.0 nm was observed in the dilute solution of cytochrome C, With increasing the concentration of cytochrome C, a new peak at 304. 0 nm appeared. The peak at 340.0 nm disappeared and only one peak at 304.0 nm was observed at a higher concentration of cytochrome C, It may originate from the change of aggregation states of cytochrome C molecules and it was considered that the peak at 340.0 nm was attributed to the monomer and peak at 304.0 nm was due to the dimmer or oligomers. When urea was added into cytochrome C solution in which both monomer and dimmer or oligomers exist, cytochrome C molecules do not denature in the range of the specific concentrations of urea. The concentration of monomer of cytochrome C molecules increased and that of aggregation slates decreased by adding urea, Therefore, the synchronous fluorescence spectroscopy can be used to identify monomer and aggregation states of cytochrome C molecules.

LIFETIMES OF RYDBERG LEVELS IN THE PERTURBED 6SNP P-1,3(1) SERIES OF YBI

Using two methods: (1) three-step excitation and (2) single UV photon excitation in an atomic beam with direct observation of the decay of the fluorescence light, we have measured the lifetimes of the Rydberg levels of YbI belonging to the perturbed series 6snp J = 1 levels. The measured values have been interpreted by the multichannel quantum defect theory (MQDT).

Fluorescence spectroscopy studies on the action of rare earths with bovine serum albumin in multimolecular system

In this paper. the interaction of tripositive terbium ions (Tb3+) with bovine serum albumin (BSA) has been investigated in the presence of some alkaline earth metals and citric acid (Cit) by using fluorescence spectroscopy. The results show that Tb-31. BSA and Cit can form ternary complex BSA . Tb-2. Cit(4) in mu =0.1 mol/l NaCl. pH6.3 hexamethylenetetramine buffer. Other tare earths are able to compete for the same binding site in BSA with Tb3+-. The sequence of con,petition is Eu3+>Pr3+>Yb3+>Gd3+>La3+>Ca2+ and Mg2+ cannot replace Tb bound to BSA.

卟啉和卟啉铜分子的成膜特性和UV－Vis光谱表征

合成了５，１０，１５，２０－四（对－异戊酯苯基）卟啉及其铜配合物，研究了它们在气液界面的成膜性质，制备了上述化合物的ＬＢ膜，利用ＵＶ—Ｖｉｓ光谱对化合物在ＬＢ膜结构中的取向进行了表征．研究结果表明．两种化合物在界面上的成膜性质和分子环面在ＬＢ膜结构中的取向均受到铜离子配位的影响.

IN-SITU UV-VISIBLE SPECTROELECTROCHEMICAL AND CIRCULAR DICHROIC ELECTROCHEMICAL STUDY OF BILIRUBIN AND BILIRUBIN PLUS HUMAN SERUM-ALBUMIN COMPLEX

The electro-oxidation of bilirubin (BR) in aqueous solution was investigated by cyclic voltammetry and in-situ thin-layer spectroelectrochemical techniques, It was found that both oxidation processes of BR are two electron transfer reactions. A mechanism

EXCIMER FLUORESCENCE STUDY ON THE MISCIBILITY OF POLY(VINYL METHYL-ETHER) AND STYRENE-BUTADIENE STYRENE TRIBLOCK COPOLYMER

The excimer fluorescence of a triblock copolymer, styrene-butadiene-styrene (SBS) containing 48 wt% polystyrene was used to investigate its miscibility with poly(vinyl methyl ether) (PVME). The excimer-to-monomer emission intensity ratio I(M)/I(E) can be used as a sensitive probe to determine the miscibility level in SBS/PVME blends: I(M)/I(E) is a function of PVME concentration, and reaches a maximum when the blend contains 60% PVME. The cloud point curve determined by light scattering shows a pseudo upper critical solution temperature diagram, which can be attributed to the effect of PB segments in SBS. The thermally induced phase separation of SBS/PVME blends can be observed by measuring I(M)/I(E), and the phase dissolution process was followed by measuring I(M)/I(E) at different times.

STUDY ON THE ACTIVE-CENTERS OF METHANE COUPLING CATALYSTS BY MEANS OF FLUORESCENCE EMISSION OF EU3+

Eu3+ ion was adopted as a probe to detect the probability of entrance of alkali elements into the crystal lattice of MgO, CaO and La2O3 by means of its characteristic emission. Based on the experimental data it is concluded that Li+ and Na+ ions can substitute Mg2+ and Ca2+ ions and only a small amount of K+ ion can enter into the lattice of CaO. Whilst Li+ ion can not enter into the lattice of lanthana. The conclusion of this investigation is in good agreement with that obtained by Lunsford by ESR studies.

DETERMINATION OF THE MOLECULAR-ORIENTATION OF A PHTHALOCYANINE DERIVATIVE IN A LANGMUIR-BLODGETT-FILM BY POLARIZED UV VIS SPECTRA

Langmuir-Blodgett (LB) films of (p-carboxyphenoxy)-tri(2,4-di-tert-pentyl phenoxy)phthalocyanine copper(II) (asyCuPc) are prepared; the associated forms of the compound in chloroform solution and the particular orientation of asyCuPc molecular macrocycles in LB films is determined by polarized UV-VIS.