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PubMed2005

Spectroscopic study on the photophysical properties of lanthanide complexes with long chain mono-docosyl phthalate.

Ortho phthalic anhydride was modified with long chain alcohol (1-docosanol) to its corresponding monodocosyl phthalate (22-Phth). Subsequently, three novel lanthanide (Eu(3+), Tb(3+), and Dy(3+)) complexes with the long chain monodocosyl phthalate were synthesized and characterized by elemental analysis and Infrared spectra. The photophysical properties of these complexes were studied in detail with ultraviolet-visible absorption spectra, low temperature phosphorescence spectra and fluorescent spectra. The triplet state energy of 22-Phth was determined to be around 25,000 cm(-1) from the maximum phosphorescent peak at 400 nm, suggesting 22-Phth is suitable for the sensitization of the luminescence of Eu(3+), Tb(3+), and Dy(3+). The fluorescence excitation and emission spectra for these lanthanide complexes of the three ligands take agreement with the above predict from energy match principle.

Journal Article↗

PubMed1987

Purification and spectroscopic properties of 124-kDa oat phytochrome.

A simplified procedure for the isolation and purification of 124-kDa phytochrome from etiolated Avena seedlings has been developed using the method of ammonium sulfate back-extraction. After hydroxyapatite chromatography of seedling tissue extracts, the pooled phytochrome was subjected to ammonium sulfate back-extraction instead of the usual application to an Affi-Gel Blue column. The resulting phytochrome had specific absorbance ratios (SAR = A666/A280) ranging from 0.85 to 0.95. Subsequent Bio-Gel filtration chromatography yielded highly pure 124-kDa phytochrome with SAR values ranging from 0.99 to 1.13. The absorption maxima of 124-kDa phytochrome were at 280, 379, and 666 nm for the red absorbing form of phytochrome (Pr) and at 280, 400 and 730 nm for the far-red absorbing form (Pfr). The A730/A673 ratio in Pfr was found to be 1.5 to 1.6. The mole fraction of Pfr under red light photoequilibrium was 0.88. No dark reversion was detected within 5 h at 3 degrees C. A photoreversible far-uv-circular dichroism was observable with all phytochrome preparations examined. Fluorescence and phosphorescence lifetimes were measured to further characterize the differences between the phytochromes prepared under different conditions. The Trp fluorescence and phosphorescence lifetimes of Pr and Pfr with the chromophore "X", probably polyphenolic in nature, were significantly shorter than those of phytochrome without the contaminant X. The short lifetime of the fluorescence of the Pr chromophore is attributable to X in the former.

Circular Dichroism↗

PubMed1975

The luminescence properties of concanavalin A.

1. The luminescence properties of native concanavalin A, both at room temperature and at 77 degrees K, are similar to those of other proteins containing tyrosine and tryptophan. 2. Binding of methyl alpha-D-glucopyranoside to concanavalin A causes a slight reduction of its fluorescence at room temperature. 3. Removal of Mn2+ and Ca2+ ions from concanavalin A causes a small increase in its fluoresence. The fluorescence: phosphorescence ratio and phosphorescence lifetime of apo-concanavalin A are similar to those of tryptophan. 4. Denaturation of concanavalin A by urea and by guanidine hydrochloride apparently takes place in two stages. Apo-concanavalin A is more easily denatured than the native molecule, but concavalin A combined with methyl alpha-D-glucopyranoside is more resistant to denaturation. 5. The luminescence properties of concanavalin A are pH-dependent. 6. The results have been interpreted in terms of the known structure and properties of concanavalin A.

Apoproteins↗

PubMed1976

Reinterpretation of luminiscence properties of neurotoxins from the venom of Middle-Asian corba Naja oxiana eichw.

A new interpretation of previous work (Bukolova-Orlova, T. G., Burstein, E.A. and Yukelson, L. Ya (1974) Biochim. Biophys. Acta 342, 272-280) and some new data on the luminescence of neurotoxins I and II from Naja oxiana venom is given, based on the newer data on their complete amino acid sequences. Very effective excitation energy exchange exists between Trp-27 and Trp-33 in neurotoxin I and between Trp-27 and Trp-28 in neurotoxin II, Which results in the tryptophanyl fluorescence spectra of each of the proteins seeming to be monocomponent ones. The lowered fluorescence quantium yield value, the shortened phosphorescence lifetime (80% of the emission has tau p less than 0.5 s, 20% has tau p = 4.8 s, comparing with usual tau p = 5.5-5.9 s) and decreased phosphorescence to fluorescence ratio (0.042, as compared to the usual 0.4-0.7) for neurotoxin I suggest that the indole chromophore of Trp-27 and/or Trp-33 are in contact with heavy sulfur atoms of disulfide, most probably of Cys(28)-Cys(32). Tryptophanyls in neurotoxin II are exposed to the solvent, however their accessibility in relation to that of the free tryptophan to the negatively charged quencher I- (0.455) is much higher than that for the positively charged Cs+ (0.08), which is probably due to the proximity of cationic Lys-25, Lys-26 and His-31. The difference of accessibility to the negative and positive quenchers is even more pronounced in the case of the neurotoxin I (1.04 and 0 +/- 0.02, respectively), though in its chromophore vicinity along the primary structure there is only one cationic group, Lys-25. This fact together with the analysis of the amino acid sequence, suggest that the space folding of this polypeptide results in the close proximity of Trp-27 and/or Trp-33 with the C-terminal peptide segment 67-73, which contains four cationic groups (His-67, Lys-69, Lys-71 and Arg-72).

Amino Acid Sequence↗

PubMed1977

The fine structure of luminescence spectra of azurin.

The spectra of azurin absorption, fluorescence, phosphorescence and fluorescence excitation have been measured in aqueous solutions at ordinary and liquid nitrogen temperatures. The fluorescence spectra of azurin even at ordinary temperatures have a well resolved fine vibrational structure. The frequency analysis reveals practically the same wave number distances between the main structure peaks in fluorescence spectra at room and low temperatures and in phosphorescence spectra. The comparison of the protein absorption and excitation spectra shows that all the energy absorbed by tyrosine residues is transferred onto indole chromophore. These data suggest an unusual tryptophan environment in this protein, which is characterized by the absence of any hydrogen bonding or other polar interaction of tryptophan with its environment. The problem of the possibility of contributions of two electronic transitions (1La in equilibrium A and 1Lb in equilibrium A) in absorption and emission spectra of azurin tryptophan arising from their mirror symmetry is discussed.

Azurin↗

PubMed1985

Chemiluminescence in L-tyrosine-H2O2-horseradish peroxidase system: possible formation of tyrosine cation radical.

Tyrosine-H2O2-horseradish peroxidase system at pH 7.4 emitted light in visible region. Phenolic compounds other than tyrosine were also emissive, whereas methoxy phenylalanine and phenyl compounds were not, in H2O2-peroxidase systems. Chemiluminescence spectrum of tyrosine of tyrosine-H2O2-horseradish peroxidase system showed two prominent peaks at 478 nm and 500 nm (Luminescence 1) and additional two or three peaks near 550 and 610 nm (Luminescence 2). Luminescence 1 is quite similar to the phosphorescence originated from an excited tyrosine in triplet state, while Luminescence 2 is quite similar to the phosphorescence originated from an indole in triplet state. Possible formation of tyrosine cation radical (a precursor of the excited tyrosine) and indole cation radical in the enzyme protein (a precursor of the excited tryptophan residue) were discussed.

Free Radicals↗

PubMed1992

Two different Ca2+ ion binding sites in factor VIIa and in des(1-38) factor VIIa.

The Ca2+ ion binding of factor VIIa and the derivative lacking the gamma-carboxyglutamic acid domain, des(1-38) factor VIIa, was investigated using intrinsic protein fluorescence and Tb3+ ion phosphorescence methods. Binding of Ca2+ ions giving rise to a decrease in the intrinsic protein fluorescence (approximately 50% at saturating conditions) is seen with both proteins. Each of the saturation curves is in accordance with the formation of a 1:1 complex of factor VIIa-Ca2+ (KD approximately 30 microM) and des(1-38) factor VIIa-Ca2+ (KD approximately 40 microM)). Yet another Ca2+ ion binding site reveals itself in each protein in Tb3+ ion phosphorescence experiments. Ca2+ ion competition studies have showed 1:1 complexes (KD's approximately 2 mM). The results are interpreted in terms of two different Ca2+ ion binding sites, one in the EGF-1 domain and one in the Gly-209-Gln-221 loop of the serine proteinase part.

Animals↗

PubMed1994

Phosphorimetry and its potential for the study of surface heterogeneity of chromatographic silica-based stationary phases.

Phosphorimetry was applied to the study of silica-based chromatographic phase surface heterogeneity by determining the phosphorescence response of a phenanthrene probe as a function of loading on underivatized silica and reversed and ion-exchange phases. The phosphorescence response was used to "titrate" and estimate the number of strong adsorption sites on underivatized silica. By incorporating covalent vs. ionic heavy atom/ion enhancers onto derivatized silicas, it was demonstrated that the probe molecules adsorb at residual silanols at lower loadings but associate with alkyl chains at higher loadings. Suggestions for further phosphorimetric studies are given.

Adsorption↗

PubMed1988

Binding of recA protein to single- and double-stranded polynucleotides occurs without involvement of its aromatic residues in stacking interactions with nucleotide bases.

Phosphorescence and optically detected triplet state magnetic resonance (ODMR) spectroscopy studies of recA protein and its complexes with poly(5-HgU) and poly(dA-5BrdU) show that the two tryptophan residues are not involved in stacking interactions with the nucleotide bases of either single- or double-stranded polynucleotides. Solvent conditions which induce preferential binding to single-stranded ligands result in a shortening of the tyrosine phosphorescence lifetime, which is further reduced upon binding to poly(5-HgU). This suggests a change in the global conformation or self-aggregation state of the protein. Binding to poly(dA-5BrdU) induces small changes in the tryptophan zero field splittings of recA, but significant changes on those of 5BrdU, which are consistent with recA binding to the minor groove of the polynucleotide.

Chemical Phenomena↗

PubMed1991

Spectroscopic evidence for NADH-induced conformational changes in rabbit muscle aldolase.

The intrinsic fluorescence (steady-state spectra, anisotropy and nanosecond decay) in combination with phosphorescence at room temperature were used to detect and characterize conformational changes in rabbit muscle aldolase accompanying the NADH-binding process. Ligand binding has entailed a decrease in aldolase fluorescence intensity, a blue shift in its maximum and a polarization increase in a long wavelength part of the emission spectrum. The NADH binding induces the changes in room temperature phosphorescence - higher intensity and longer lifetime. The excited state energy transfer from tryptophans to NADH is not observed, and the character of spectroscopic changes on NADH binding allows us to reveal the spectroscopic heterogeneity among the tryptophan residues. The character, location of protein conformational changes associated with the binding of NADH and their relation to the tryptophans' microenvironment in aldolase are discussed.

Animals↗

PubMed1996

Interaction of alkaline phosphatase with cytochrome c.

Alkaline phosphatase (AP) a protein which exhibits long-lived phosphorescence lifetime and ferricytochrome c as a phosphorescence quenching agent were examined. The excitation of the tryptophan triplet state resulted in cytochrome c reduction confirming long-range electron transfer as the quenching mechanism. The rate of electron transfer was not related to the length of the illumination interval; an additional reaction between the two proteins leading to cytochrome c reduction was detected. The reaction which proceeded in the dark was not sensitive to oxygen, was dependent on pH, and on the AP to cytochrome c ratio. At optimum 68 +/- 4% of the total cytochrome c could be reduced due to the presence of AP. On incubation of the two proteins the conformation of cytochrome c was altered as was evidenced by its decreased reducibility by ascorbate, by the disappearance of the absorption band at 695 nm, by the appearance of the new band at 620-640 nm, and by a change in circular dichroism spectra witnessing a structural alteration in the vicinity of the heme cleft. This was characterized by a profound increase in positive elipticity at 400 nm and by a reversible change in the magnitude of negative elipticity at 417 nm. The reaction was not significantly affected by the addition of sulfhydryl-binding and metal-complexing agents.

Aerobiosis↗

PubMed1993

Fluorescence depletion measurements in various experimental geometries provide true emission and absorption anisotropies for the study of protein rotation.

Use of fluorescence depletion methods for measuring slow protein rotational diffusion has been limited by failure to obtain, from depletion data, well-defined anisotropy functions dependent on the distribution of either fluorophore emission or absorption transition dipoles, but not both. Such anisotropies would be directly comparable to those obtained from phosphorescence emission or triplet absorption measurements. We now describe such procedures applicable to cuvet and microscope experimental geometries, together with supporting experimental results. In cuvet measurements, the pump and probe beams are colinear and fluorescence is collected at 90 degrees to this axis. The data analysis procedure for this geometry has been suggested by Wegener (Biophys. J., 46 (1984) 795) and permits calculation of the absorption and emission anisotropies and the interdipole angle. In microscope experiments, fluorescence emission is collected along the pump/probe beam axis. For microscope measurements, a new experimental procedure permits evaluation of absorption and emission anisotropies when the interdipole angle is independently known. In either case multiple depletion measurements are required, each with different relative orientations of the probe beam polarization, pump beam polarization and emission polarizer axis. We have used these methods to calculate the time-dependent anisotropies for eosin-derivatized BSA rotation in glycerol solutions in both experimental geometries. These data correspond well with those obtained from time-resolved phosphorescence anisotropy measurements.

Chemistry, Physical↗

PubMed1986

Enols of aldehydes in the peroxidase/oxidase-promoted generation of excited triplet species.

General (acid and base) or specific (fluoride ion) catalysis generates the enol of isobutanal and propanal from the corresponding trimethylsilyl enol ethers. The enols are directly rapidly oxidized by peroxidase (acting as an oxidase) to triplet acetone or triplet acetaldehyde, respectively, and formic acid. Due to the faster rate of reaction and the absence of quenching by excess aldehyde, the excited carbonyl emits more strongly than when the aldehyde itself is the substrate. With both enols the emission is pure phosphorescence. Both triplet acetone and triplet acetaldehyde are generated within the enzyme, as shown by the different quenching by D- and L-tryptophan, and are somewhat protected from oxygen quenching, as attested by the very fact that phosphorescence is observed. The use of enol precursors as substrates opens wide possibilities for photochemical investigations in the absence of light over a much broader range of experimental conditions.

Acetone↗

PubMed1996

Real time frequency domain fibreoptic temperature sensor using ruby crystals.

The excited state phosphorescence lifetime of ruby crystals is used to monitor temperature in the physiological range from 15 degrees to 45 degrees C with precision and accuracy less than 1 degree C, in real time. Precision of 0.1 degree C is attained with 3 min integration times. A 500 micron cubic ruby crystal bounded to the distal end of an optical fibre of similar core dimensions is excited with pulsed Ne-He laser light of about 9 microW average power. The instrument uses a sampler for data acquisition, and frequency domain methods for data fitting. The instrument amplifies the a.c. components of the detector output and band limits the signal to 800 Hz. The fundamental frequency of the excitation is set to 24.41 Hz to obtain 32 or less harmonics. This band-limited signal is sampled and averaged between 20 and 100 cycles to obtain temperature measurements in real time. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio, of each sampled harmonic, is then computed. Five to 32 values of the phase and modulation are averaged before computing the sensor lifetime. The technique is capable of measuring precise and accurate excited state lifetimes from subpicowatt luminescent signals in plastic optical fibres. A least squares fit yields the lifetimes of single exponentials. A component of zero lifetime is introduced to account for the backscatter excitation seen by the photodetector leaking through optical interference filters. The phosphorescence lifetimes measured reproducibly to about six parts in 1000, with a 2 s integration time, are used to monitor physiological temperature. Temperatures are computed employing empirical polynomials. The system drift is 3% over 5 h of continuous operation. The instrumentation and methods allow 2.7 s update times and 50 s full response times.

Biomedical Engineering↗

PubMed2006

Determination of alkaline phosphatase based on affinity adsorption solid-substrate room temperature phosphorimetry using rhodamine 6G-dibromoluciferin luminescent nanoparticle to label lectin and prediction of diseases.

In the presence of heavy atom perturber LiAc, the silicon dioxide nanoparticle containing rhodamine 6G (R) and dibromoluciferin (D) (R-D-SiO(2)) can emit strong and stable solid-substrate room temperature phosphorescence signal of R (lambda(ex)/lambda(em)=481/648 nm) and D (lambda(ex)/lambda(em)=457/622 nm) on the surface of acetyl cellulose membrane (ACM). R-D-SiO(2) is used to label triticum vulgare lectin (WGA). Then two types of affinity adsorption reactions, R-D-SiO(2)-WGA- alkaline phosphatase (ALP) (direct method) and WGA-ALP-WGA-R-D-SiO(2) (sandwich method), are carried out on ACM. The conditions and the analytical characteristics for the determination of ALP using affinity adsorption solid-substrate room temperature phosphorimetry (AA-SS-RTP) were studied. For a 0.40-microl drop of sample, results show that the detection limits of the sandwich method are 0.16 ag spot(-1)(457/622 nm) and 0.17 ag spot(-1)(481/648 nm), and the detection limits of the direct method are 0.41 ag spot(-1) (457/622 nm) and 0.44 ag spot(-1) (481/648 nm). The contents of ALP in human serum correlated well with those obtained by enzyme-linked immunoassay. This study shows that AA-SS-RTP whether by the sandwich method or the direct method, can combine very well the characteristics of both high sensitivity of SS-RTP and specificity of the immunoreaction. Simultaneously, whether the phosphorescence excitation/emission wavelength of either R or D in R-D-SiO(2) is chosen to determine ALP, this can promote the agility and widen the adaptability of AA-SS-RTP.

Adsorption↗

PubMed2004

Orientational manoeuvres in the dark: dissociating allocentric and egocentric influences on spatial memory.

Subjects in a darkroom saw an array of five phosphorescent objects on a circular table and, after a short delay, indicated which object had been moved. During the delay the subject, the table or a phosphorescent landmark external to the array was moved (a rotation about the centre of the table) either alone or together. The subject then had to indicate which one of the five objects had been moved. A fully factorial design was used to detect the use of three types of representations of object location: (i) visual snapshots; (ii) egocentric representations updated by self-motion; and (iii) representations relative to the external cue. Improved performance was seen whenever the test array was oriented consistently with any of these stored representations. The influence of representations (i) and (ii) replicates previous work. The influence of representation (iii) is a novel finding which implies that allocentric representations play a role in spatial memory, even over short distances and times. The effect of the external cue was greater when initially experienced as stable. Females out-performed males except when the array was consistent with self-motion but not visual snapshots. These results enable a simple egocentric model of spatial memory to be extended to address large-scale navigation, including the effects of allocentric knowledge, landmark stability and gender.

Adult↗

PubMed2004

Spectroscopic study on binding behaviors of different structural nonionic surfactants to cyclodextrins.

The binding of polyethylene glycol (10) n-octylphenyl ether (OPE) and polyethylene glycol (10) tert-octylphenyl ether (Triton X-100, TX) to beta-cyclodextrin (beta-CD) and heptakis(2,3- beta-dimethyl)- beta-CD (DM- beta-CD) was described in detail by surface tension, steady-state fluorescence of OPE and TX, and phosphorescence of 1-bromonaphthalene (BN) probe. Surface tension and fluorescence measurements show that beta-CD entraps the hydrophobic moieties of OPE and TX to form inclusion complexes with the stoichiometry of 1:1. Unlike the n-octyl group of OPE, however, the tert-octyl group of TX fails to be encapsulated into the cavity of DM- beta-CD because of the steric hindrance of methyl groups at the rim of the cavity. The inclusion of the phenyl group of OPE and TX was demonstrated by dynamic quenching effect of iodide ion on fluorescence of OPE and TX in the presence of beta-CD. Static fluorescence quenching of OPE and TX by BN, phosphorescence of BN, and energy transfer between TX and BN provide additional evidence for the inclusion of their phenyl groups into the CD cavity. Analyses of molecular size suggest that the longer tert-octyl group of OPE is situated in curled manner in the cavity and the tert-octyl group of TX undergo a slight distortion for fit of beta-CD. Further introduction of the third guest component into the CD cavity occupied by OPE and TX will force the flexible octyl groups of OPE and TX to deform to a greater extent.

Cyclodextrins↗

PubMed2005

Proton transfer reaction in 4-hydroxy-3-formyl benzoic acid in protic solvents at room temperature and 77K and some theoretical aspects.

Proton transfer processes of 4-hydroxy-3-formyl benzoic acid (HFBA) have been studied in a number of different protic solvents by means of absorption, emission and nanosecond transient spectroscopy at room temperature and 77K. Intermolecular interaction occurs in polar protic solvents only in presence of a base in the ground state whereas in the excited state, intermolecular complex formation and proton transfer occurs even in pure protic solvents. The dianion is detected in water, methanol, ethanol and TFE in presence of base. HFBA shows phosphorescence in pure ethanol at 77K. The occurrence of phosphorescence is due to rupture of the intramolecular bond and rotation of the formyl group. We have calculated quantum yields of fluorescence and also estimated decay rates from nanosecond measurements. The energetics of the ground and excited state proton transfer in HFBA have been investigated at the AM1 level of approximation. The ground singlet is predicted to have a large activation barrier on the proton transfer path, while the barrier height is much lower on the corresponding excited singlet surface.

Benzoic Acid↗