Fluorescence Spectra Of Complexes Research Articles

Resolution of complex fluorescence spectra recorded on single unpigmented living cells using a computerised method

The identification and quantification of fluorescent compounds in a complex fluorescence spectra are always difficult, especially in the case of low signal:noise ratio. We propose a computerised method that allows the resolution of low light level complex fluorescence spectra into its components. Based on a linear combination of N possible characteristic fluorescence spectra, and using N weighting functions, this method allows the integration of fluorescence intensities over the entire fluorescence spectra and the generation of n equations with N unknowns. The compounds that participate in complex fluorescence spectra are identified and quantified. Because fluorescence intensities can be integrated we can resolve complex fluorescence spectra presenting a low signal:noise ratio. The reliability and sensitivity of our method are shown through examples of resolution of complex intracellular fluorescence of single living cells pretreated with benzo(a)pyrene. Depending on the cell type and treatment, two, four, or five components can be identified in the complex fluorescence spectra.

Cooperative emission of photons by weakly coupled chromium ions in Al2O3

Under strongcw-excitation ruby crystals exhibit complex anti-Stokes fluorescence spectra in the near ultraviolet. Based on ring dye laser excitation spectra, fluorescence decay and concentration dependence, we show that these spectra can be decomposed into single ion emissions and a cooperative emission at the double energy of the2 E→4 A 2 transition. The unusual vibronic sideband of the latter suggests a general mechanism for the coupling of distant ions in polar insulators involving the electric field of longitudinal optical phonons.

Fluorescence properties of tetraphenylporphyrin-polypeptide complexes as model photosynthetic systems

The steady-state and time-resolved fluorescence spectra of complexes formed from α,β,γ,δ-tetrakis(4-carboxyphenyl) porphin and the synthetic sequential polytripeptides poly(L-lysyl-L-leucyl-L-alanine) n (I) (MW 7900) and poly(L-lysyl-L-alanyl-L-alanine) n (II) (MW 6900) are studied in phosphate buffer ( pH=7.2). The peptide matrices were found to bond 4-5 pigment molecules per one polypeptide. The complexed pigment fluorescent decay kinetics is two-exponential with components τ 1 =240 ps and τ 2=2400 (I) and 3500 ps (II). The relative contributions of τ 1 correlate with the degree of α-helicity of the polypeptide matrix.

Application of the indirect dephasing model to resonance and dispersed fluorescence in the isolated molecular complex

The theory of indirect dephasing proposed by Hiroike is applied to studying the mechanism of line broadening in resonance and dispersed fluorescence spectra of molecular complexes in supersonic free jet. In the indirect dephasing model, the width of the luorescence spectra which is characterized by the homogeneous linewidth can be expressed in terms of two parameters, the rate of intramolecular vibrational redistribution (IVR), γ and frequency change induced by the IVR, δω. It is shown that the non-Markovian character introduced into the interaction between the intra- and intermolecular modes reduces the indirect dephasing rate. The theory is applied to calculation of the linewidth of the resonance fluorescence of the tetrazine–Ar molecular complex excited in 6a1 vibronic level. The introduction of the non-Markovian character is necessary to calculate the linewidth of the fluorescence in a molecular complex with a few intermolecular modes such as tetrazine–Ar.

The coprecipitation of an organophosphate fraction from harbour water for x-ray fluorescence spectrometry

The film x-ray fluorescence spectrum of a cobalt pyrrolidinedithiocarbamate carrier complex, precipitated in harbour-water samples, contains a previously unreported peak at the wavelength of the first-order K α line of phosphorus. The coprecipitated phosphorus is an organophosphate fraction of biological origin, constituting approximately 10% of the dissolved organophosphorus in the waters.

Van der Waals, charge-transfer and “mixed” states of molecular complexes formed in supersonic jets

Excitation and fluorescence spectra of perylene or anthracene complexes have been studied in a supersonic jet While the phenol- or anisole-perylene complexes behave as van der Waals systems and the N,N-dimethylaniline-perylene, N,N-dimethylaniline- or aniline-anthracene complexes as exciplexes, the aniline- or N-monomethylaniline-perylene complexes have peculiar spectra which suggest a strong mixing between the locally excited and charge-transfer states.

Presence in Photosystem II Core Complexes of a 34-Kilodalton Polypeptide Required for Water Photolysis

Photosystem II (PSII) reaction center core complexes have been isolated and characterized from wild type (WT) Scenedesmus obliquus and from its LF-1 mutant. LF-1 thylakoids are blocked on the oxidizing side of PSII and have a reduced Mn content. Visible absorption and low temperature fluorescence spectra of both core complexes are identical and resemble those reported for spinach (Satoh, Butler 1978 Plant Physiol 61: 373-379). Lithium dodecyl sulfate-polycrylamide gel electrophoresis reveals that a protein alteration, originally observed in thylakoid membranes (Metz, Wong, Bishop 1980 FEBS Lett 114: 61-66), is retained in the PSII core particles. That is, a 34-kilodalton (kD) polypeptide, present in the WT core complex, is missing in the mutant, and the core complex of the mutant contains a 36-kD protein not present in the WT. The 34-kD intrinsic protein is also observed in O(2)-evolving PSII preparations and PSII core complexes from spinach. It is distinct from the 33-kD extrinsic protein first reported by T. Kuwabara and N. Murata (1979 Biochim Biophys Acta 581: 228-236). We suggest that the 34-kD protein is a site of Mn binding in the PSII membrane.

Fluorescence study of the effects of histone tyrosyl residues of DNA

The fluorescence spectra of histone-DNA complexes at pH 7.0 were studied. These species showed fluorescence spectra broader than the characteristic histone spectrum, with the appearance of peaks at higher wavelengths. It is shown that the emission at higher wavelengths arises from the bases of DNA (specially from the A-T bases), when their hydrogen bonds are weakened or broken. These results corroborate those of other authors and it is postulated that tyrosine residues in histone form hydrogen bonds with DNA and/or stack with the bases of the nucleic acid.

Polarization of phononless lines in the fluorescence spectra of metallic complexes of porphine at 4.2�K under selective laser excitation

Polarization of phononless lines in the fluorescence spectra of metallic complexes of porphine at 4.2�K under selective laser excitation

Photometric determination of aluminium and zinc with salicylaldehyde semicarbazone

The effect of some tensides on the absorption, excitation, and fluorescence spectra of Al and Zn complexes of salicylaldehyde semicarbazone in aqueous-alcoholic solutions and on their extractability into ethyl acetate has been studied. The shape of the absorption spectra is unaffected by the presence of the tensides while the time of the complex formation is shorter. The complexes are extractable into ethyl acetate in the presence of the anionactive tenside tested, sodium lauryl sulphate. The optimum conditions for the spectrophotometric and fluorometric determination of Al and Zn have been established. The limit of determination is 2 ng ml-1 (pH 3.8-4.8) for Al and 50 ng ml-1 (pH 8.4-8.6) for Zn. Using thiosulphate or fluoride as masking agents, Zn can be determined in a concentration of 2 μg ml-1 in the presence of the same quantity of Al or Cu, or in the presence of a tenfold excess of Fe, with a relative standard deviation of 1.5%.

Binding between thermolysin and talopeptin (MKI) in which the tryptophan residue was converted into kynurenine.

The tryptophan residue of talopeptin, which is a specific inhibitor for thermolysin, was converted into kynurenine by ozonization followed by acid-catalyzed hydrolysis, and (Trp leads to Kyn) talopeptin (Kyn-talopeptin) thus obtained was purified with gel-chromatography. The inhibitor constant of Kyn-talopeptin, K1, and the dissociation constant of thermolysin-Kyn-talopeptin complex, Kd, directly obtained by fluorometric titration were in good agreement with each other. These values were found to be about 10 times larger than those of intact talopeptin, but both inhibitors showed a similar pH dependence. Upon the binding of Kyn-talopeptin with thermolysin, the protein fluorescence of thermolysin decreases by about 60%, while the kynurenine fluorescence (measured at 450 nm when excited at 360 nm) of the inhibitor increases about 14 times. The measurements of the excitation and fluorescence spectra of EI complex strongly indicated the energy transfer from tryptophan residue(s) (the donor) of the enzyme to kynurenine residue (the acceptor) of the inhibitor. The distance between the donor and the acceptor was roughly estimated to be 18 A. This value is in good agreement with the one expected from the crystallography of phosphoramidon-thermolysin complex. The binding process was studied kinetically with the stopped-flow method over the pH range between 4.5 and 8.5, by monitoring the decrease in the fluorescence intensity of the enzyme tryptophan caused by the complex formation. Comparison of the data with those previously obtained for talopeptin-thermolysin system revealed that the replacement of the tryptophan residue by kynurenine of the inhibitor does not affect the apparent second-order association rate constant, kon, seriously.

Lanthanide complexes with N-oxides. Synthesis and fluorescence spectra of lanthanide nitrate and thiocyanate complexes with pyridine N-oxide

Lanthanide complexes with N-oxides. Synthesis and fluorescence spectra of lanthanide nitrate and thiocyanate complexes with pyridine N-oxide

OPTICAL‐MICROWAVE DOUBLE RESONANCE SPECTROSCOPY OF IN VIVO CHLOROPHYLL

Abstract—At low temperatures, chloroplast and subchloroplast preparations exhibit complex fluorescence spectra. Emission bands can be attributed to photosystem (PS) particles and various antenna‐chl proteins as well as solubilized chls. Initial results from a systematic study of the components of these fluorescence spectra via optical‐microwave double resonance spectroscopy are presently reported. Conclusions regarding possible structural features are discussed. Experiments on triplet sublevel decay rates yielded data consistent with an interpretation of triplet energy transfer within antenna fragments.

Concerning the fluorescence of some 7-hydroxycoumarins and related compounds

The fluorescence of 7-hydroxy-4-methylcoumarin and 4-carboxymethyl-7-hydroxycoumarin and some simple derivatives, has been examined. For compounds having a free 7-hydroxy-group, complex fluorescence spectra were obtained when solvents containing water were employed. The complexity is in part due to the ground state equilibrium, phenol ⇄ phenolate anion. This means that unless the excitation wavelength is carefully selected, more than one species is excited. Four fluorescent species, derived from the phenol, were observed in various aqueous alcohol systems: two species were identified as the excited phenol and its anion and the other two tentatively identified as an intimate and sovent separated ion-pair. From steady state, fluorescence measurements and time resolved ns fluorescence spectroscopy the inter-relation of these various excited states was established. The role of water in these systems is discussed.

Deactivation of an excited charge-transfer complex II. Influence of rigidity of medium on radiative and radiationless transitions

Fluorescence spectra, quantum yields and decay times for charge-transfer complexes of tetracyanoethylene with benzene, toluene, ortho-xylene and para-xylene in low-temperature glassy solutions of different viscosities have been investigated. It was established that the influence of viscosity or rigidity of medium on charge-transfer fluorescence consists in the decrease of efficiency of radiationless processes when viscosity or rigidity increases. Fluorescence spectra of complexes of tetracyanoethylene with toluene, o-xylene and p-xylene have a composite double-band character at high viscosities of medium. The intensity of both subbands changes in a different way with change of viscosity. The excitation spectra of these complexes are dependent on the wavelength of observation. These facts are discussed in terms of an existence of different orientational isomers of a charge-transfer complex of low symmetry.

Fluorescence and absorption spectra of the charge transfer complex in the EDA system exhibiting exciplex fluorescence

The fluorescence (polarization) and absorption spectra, and lifetimes of the charge transfer (CT) complexes between 9,10-dicyanoanthracene and alkylnaphthalenes in 3-methylpentane which exhibit characteristic exciplex fluorescences above about 160° K were observed below ≈ 125° K. The results demonstrate that CT absorption bands lie in the region of the 1L a band of the acceptor, and that fluorescence lifetimes of the exciplex and the CT complex depend markedly on the electron donors.

Fluorimetric determination of serum 11-hydroxysteroids. Calculative correction of deviations in complex fluorescence spectra

Abstract Fluorimetry of serum 11-hydroxycorticosteroids was accompanied by contamination due to nonspecific fluorescence. A spectro-fluorometrical method was proposed for the correction of the contamination.

Differences in fluorescence spectra of acridine orange-DNA complexes related to DNA base composition.

Differences in fluorescence spectra of acridine orange-DNA complexes related to DNA base composition.

Analysis of the fluorescence spectra of europium(III)-bis-phenanthroline-tris-carboxylate complexes

The fluorescence spectra of microcrystalline complexes of the composition Eu(phen)2(benz)3, Eu(phen)2(sal)3, and Eu(phen)2(p-OH-benz)3 have been investigated under high resolution at room temperature and 77°k. The effective Eu(III) site symmetries for Eu(phen)2(benz)3(C 2v ) and Eu(phen)2(sal)3(D 2) complexes have been established with the help of group theoretical reasoning. The Eu(III) fluorescence lines for Eu(phen)2(p-OH-benz)3 complex are very broad and weak even at 77°k; reasons for this weakness are given. A comparison of fluorescence intensities of Eu(phen)2(benz)3 and Eu(phen)2(sal)3 with other bis-phenanthroline complexes has been presented.

Fluorescence spectra of ternary complexes of dehydrogenases with reduced diphosphopyridine nucleotide and reduced substrates

Fluorescence spectra of ternary complexes of dehydrogenases with reduced diphosphopyridine nucleotide and reduced substrates