bluuebunny/crossref_metadata_2025 huggingface dataset:
Tuthillia, a new Neotropical psyllid genus (Homoptera: Psylloidea)
Authors: HODKINSON I. D. , BROWN R. G. , BURCKHARDT D.
Published: January 2008

Tuthillia gen.n. (Homoptera: Psylloidea) is erected for four Neotropical species: canabina sp.n. (the type‐species from Belize and Panama), cognata sp.n. (Brazil), latipennis sp.n. (Panama) and iuncta sp.n. (Brazil). It is suggested that Tuthillia forms a monophyletic group with the ciriacremine genera Ciriacremum, Kleiniella and Pal‐mapenna. However, only iuncta possesses an R‐M cross vein in the forewing, a character which has been used to define the ciriacremines in the past. It seems, therefore, that this character is unstable and alternative synapomorphies are discussed. The genital morphology of Tuthillia is similar to that found in both Ciriacreminae and Diaphorininae (Aphalaridae). It is speculated that these subfamilies represent previously unrecognized sister groups defined using the genital characters as synapomorphies.
Morphological variation in British Folsomia quadrioculata Tullberg (Collembola: Isotomidae): a multivariate study
Authors: WETTON MARK N.
Published: January 2008

Abstract. Morphological variation among freshly caught specimens resembling Folsomia quadrioculata Tullberg was examined using principal components analysis and canonical variates analysis. Two distinct groups were identified corresponding with F. quadrioculata and F.manolachei Bagnall. Previous workers have questioned the specific status of F.manolachei and regarded these two species as inseparable using morphometric characters. A study of specimens previously identified as F. quadrioculata suggested that many were mis‐identified and that F.manolachei is more abundant in the British Isles than is usually thought. Variation in some characters traditionally used to identify Folsomia species was examined and a method for distinguishing adult and juvenile F.quadrioculata from F.manolachei is provided. The synonomy of F.nana Gisin with F.manolachei is supported. The separation of F.diplothalma Axelson from F. quadrioculata is discussed, concluding that no characters are known which can reliably separate British specimens of these species.
Occurrence and significance of natural hybrids between Papilio dardanus and P.phorcas (Lepidoptera: Papilionidae)
Authors: VAN E‐WRIGHT R. I. , SMITH CAMPBELL R.
Published: January 2008

Abstract. Species can exchange genes through occasional hybridization. As a result, and contrary to some expectations, closely related species may be genetically more compatible in sympatry than in allopatry. This could be so for two well‐known African swallowtails, Papilio dardanus Brown and P.phorcas Cramer. Five natural hybrids between the two species are documented, their significance is discussed, and further information requested.
A new genus and species of brown lacewing from Venezuela (Neuroptera: Hemerobiidae), with comments on the evolution of the hemerobiid forewing radial vein
Authors: OSWALD JOHN D.
Published: January 2008

Abstract. Biramus lunatus gen.n., sp.n. is described from Venezuela. This species is of special phylogenetic interest as it is the sister‐group of the subfamily Hemerobiinae (sensu Oswald, 1993), which previously contained four genera (Hemerobiella, Hemerobius, Nesobiella and Wesmaelius) and approximately 200 of the c. 550 world hemerobiid species. The conformation of the forewing radius in Biramus is especially interesting and provides a test case for distinguishing parallel evolution among forewing radial vein states within the Hemerobiidae.
ON SOME PROBLEMS CONCERNING INVESTIGATION OF LIQUID‐PHASE CHEMILUMINESCENCE
Authors: Belyakov V. A. , Vassil'ev R. F.
Published: January 2008

Abstract— Some features of chemiluminescence important for quantitative studies of the phenomenon are discussed. Parallel excitation reactions may lead to several sorts of emitters. Energy transfer from and quenching of excited states may be responsible for the peculiar behaviour of chemiluminescent systems. These points are illustrated by results for a model reaction: thermal decomposition of dicyclohexylperoxydicarbonate (DCHPC) in the presence of O2 with or without methylethylketone and an activator, 9,10‐dibromoanthracene.
REVERSIBLE PHOTODIMERIZATION OF ANTHRACENE AND TETRACENE
Authors: Wei Kei Sin , Livingston Robert
Published: January 2008

Abstract— Dianthracene is efficiently photodissociated, forming anthracene with a quantum yield of about 0.63. Like anthracene, tetracene undergoes a reversible photochemical reaction, the product of which appears to be di‐tetracene. In dilute, deoxygenated solutions the of quantum yeild for the formation of di‐tetracene is directly proportional to the concentration of the monomer ødim = 2.2 (T̃). The quantum yield for the reverse reaction is approximately 0.74

When dilute deaerated solutions of anthracene are irradiated with the unfiltered radiation from a quartz‐mercury arc, a degradation product is formed. Unlike the dimer, this product cannot be converted into anthracene either by heating it to 200d̀C or by irradiating it in solution with light of 254 nm. This degradation product appears to be the compound or compounds which Birks et al. believed to be dianthracene. Irradiation of deaerated solutions of anthracene (or tetracene) with light of wavelenghts longer than 300 nm produces only the dimer, which has an absorption spectrum similar to that reported by Coulson et al.
ELECTRONIC SPECTRA OF AZA‐AROMATICS IN POLYMER MATRICES†
Authors: Park E. H. , Kadhim A. H. , Offen H. W.
Published: January 2008

Abstract— The absorption and fluorescence spectra of acridine, phenazine, their cations and phenazine‐di‐N‐oxide are studied in several polymer matrices. There is a one‐to‐one correspondence between previously measured spectra in fluid media and those reported here for plastic media. The matrix‐induced spectral shifts are dependent upon the polarity and hydrogen‐bonding ability of the polymer substrate. Environmental perturbations are also produced by high pressures (0–27 kbar) applied to the polymer matrix. Specific interactions between polymer substrate and the electronically excited solutes are evident from pressure‐induced red shifts of the fluorescence and changes in quantum yields under pressure. These interactions between solute and its microscopic environment are subtle and varied for this group of nitrogen hetero‐cyclics, although their effects are smaller than those encountered in the adsorption of related dyes.
VISUAL PIGMENTS: THEIR SPECTRA AND ISOMERIZATIONS*
Authors: Wiesenfeld John R. , Abrahamson E. W.
Published: January 2008

Abstract— We have made Pariser‐Parr‐Pople molecular orbital calculations of the torsional energy curves for rotation about pertinent bonds in retinal and its Schiffs base derivatives. The results correlate well with their observed spectra and isomerization behavior. The calculations are also consistent with the visual pigment model of a protonated Schiffs base of retinal perturbed by a charged group in its environment.
EXCITED STATES OF SIX‐MEMBERED N‐HETEROCYCLES. FLUORESCENCE, PHOSPHORESCENCE AND ACID‐BASE EQUILIBRIA OF FIVE MONO‐ AND DIAZA‐PHENANTHRENES IN THE LOWEST EXCITED (τ,τ) STATES
Authors: Grabowska A. , Pakuła B. , Panciř J.
Published: January 2008

Abstract— Acid‐base equilibria of five azaphenanthrenes (1‐and 4‐aza; 1,10‐, 1,7‐, and 4,7‐diaza) in the two lowest excited (τ,τ) states have been determined by Förster's cycle. Pure electronic levels of the free bases and their conjugate acids have been located from the absorption, fluorescence and phosphorescence spectra. In diazaphenanthrenes the increase of the first pKa and the decrease of the second pKa under excitation has been observed, and an explanation is offered. In many cases the reactivity of the molecule excited to the lowest triplet state differs considerably from that in the ground state. The Pariser‐Pam‐Pople (PPP) calculations of the free bases have been performed. From the theoretical results, the changes of the net charge on nitrogen atoms under excitation and the magnitude of the S‐T splitting in the La and Lb states have been discussed and compared with experiment.
PHOTOINACTIVATION OF CATALASES FROM MAMMAL LIVER, PLANT LEAVES AND BACTERIA. COMPARISON OF INACTIVATION CROSS SECTIONS AND QUANTUM YIELDS AT 406 nm
Authors: BJÖRN L. O.
Published: January 2008

Abstract— Photoinactivation in vitro at pH 7.0 of catalases from different sources (bovine liver, spinach leaves, and Micrococcus lysodeikticus) was studied. The wavelength of the inactivating light was close to the Soret peak of catalase. No great difference in light sensitivity between soluble catalases were found; the inactivation cross sections found ranged from 3.8.10‐4 to 5.0. 10‐4Å2/molecule. The inactivation quantum yield is 2.2. 10‐5 for bovine liver catalase and 3.110‐5 for Micrococcus catalase. The quantum yield for soluble spinach catalase is of a similar order of magnitude. There are some indications of a greater resistance to photodestruction of the spinach leaf catalase activity associated with small particles.
ABSORPTION AND FLUORESCENCE SPECTRA OF CHLOROPHYLL‐a IN POLAR SOLVENTS AS A FUNCTION OF TEMPERATURE
Authors: BALNY CLAUDE , BRODY SEYMOUR S. , HOA GASTON HUI BON
Published: January 2008

Abstract— Absorption and fluorescence spectra of chlorphyll‐a in aqueous alcohol were determined as a function of temperature between 173° and 293°K. From a comparison of these spectra with ones obtained in pure methanol, it is suggested that changes in molecular association occur within aggregates of chlorophyll‐a in aqueous‐alcoholic solution induced by variation of the dielectric constant. The latter varies over a wide range in aqueous alcohol as a function of temperature.
EXCIPLEXES AND THE FLUORESCENCE OF STAPHYLOCOCCUS AUREUS ENDONUCLEASE*
Authors: LONGWORTH J. W. , BATTISTA MARIA DEL CARMEN
Published: January 2008

Abstract— The family of fluorescence spectra obtained from the endonuclease of Staphylococcus aureus at temperatures from 140° to 230°K, when superimposed, show a unique intersection point at 336nm. This indicates that only two types of fluorescent species need be considered with this protein, a low‐temperature form and a high‐temperature form. Since the high‐temperature form lacks fine structure and has a large Stokes' shift, the spectral observations are consistent with the notion that high‐temperature fluorescence comes from a tryptophan that has formed a complex with a solvent molecule within its excited‐state lifetime. The absorption spectrum and both of the fluorescence spectra indicate that the tryptophan, even in the high‐temperature state, is in an environment with a low dielectric constant.
PROTOLYTIC EQUILIBRIA IN THE LOWEST EXCITED SINGLET STATES OF 2‐HYDROXYQUINOLINE AND 4‐HYDROXYQUINOLINE
Authors: SCHULMAN S. G. , CAPOMACCHIA A. C. , TUSSEY B.
Published: January 2008

Abstract— Fluorescence spectra of 2‐ and 4‐hydroxyquinoline in a variety of solvents indicate that the lactam‐lactim tautomerism favoring the lactam structure in the ground state also favor the lactam structure in the lowest excited singlet state. Fluorimetric titrations show that the cations of both isomers become slightly more acidic in the lowest excited singlet state and that the anion of the 2 isomer becomes slightly more basic in the excited state. The excited anion of the 4 isomer is either identical in basicity to the ground state anion or does not equilibrate with the quinolone during the lifetime of the excited state. The Forster cycle is found to give a pKα* values in generally poor agreement with those obtained from fluorimetric titrations. The reasons for this are discussed.
FLUORESCENCE QUENCHING IN PHENYLALANINE AND MODEL COMPOUNDS*
Authors: TOURNON J. , KUNTZ E. , EL‐BAYOUMI M. ASHRAF
Published: January 2008

Abstract— The effects of the carboxylic and amino groups in their neutral and charged forms on the absorption and emission properties of phenylalanine are analyzed with the help of model compounds containing either substituent. Fluorescence yields of phenylalanine and model compounds were measured as a function of pH. Fluorescence quenching occurs in going from COO‐ to COOH and from NH3+ to NH2. Lowering the ionization potential of the phenyl group by substitution increases the quenching effect. This provides more evidence that an intramolecular charge‐transfer mechanism may be responsible for intersystem‐crossing rate enhancement and fluorescence quenching in phenylalanine and model compounds.
THE ORIENTATION OF CHLOROPHYLL AND BACTERIOCHLOROPHYLL MOLECULES IN AN ORIENTED LECITHIN MULTILAYER
Authors: Hoff A. J.
Published: January 2008

Abstract— Chlorophyll a and b and bacteriochlorophyll a have been incorporated in an oriented phospholipid multilayer. The orientation of the chlorophyll molecules in this layer has been measured by polarization spectroscopy. Formulas are given expressing the dichroic ratio R as a function of the angle of tilt θ between the molecule and the plane of the multilayer and the angle μ between this plane and the transition dipole moment measured in the plane of the molecule. The possibility of overlapping bands of mutually perpendicular polarization has been taken into account. Analysis of the experimental results gives the angles θ and μ as well as an estimate for the fraction of polarization of some bands along the dihydro axis in the plane of the chlorophyll molecule.
FURTHER IN VIVO STUDIES ON THE PARTICIPATION OF SINGLET OXYGEN IN THE PHOTODYNAMIC INACTIVATION AND INDUCTION OF GENETIC CHANGES IN SACCHAROMYCES CEREVISIAE
Authors: Kobayashi Katsumi , Ito Takashi
Published: January 2008

Abstract—In vivo participation of singlet excited oxygen (1O2, 1Δ9) in the photodynamic inactivation and induction of genetic changes (gene conversion) in acridine orange‐sensitized yeast cells was investigated by using N3‐, an efficient 1O2 quencher, and D2O, a known agent for the enhancement of the lifetime of 1O2. The addition of N3‐ protected the cells from both photodynamic actions. From an analysis of the concentration‐dependent protection, about 80% of the induction of the genetic change is explainable on the basis of 1O2 mechanism. The quantitative estimation of the N3‐ protection in the inactivation was not possible because of the sigmoidal nature of the inactivation curve. The replacement of H2O with D2O during illumination was effective in enhancing the photodynamic inactivation but almost completely ineffective for the gene conversion induction. The deuterium effect with the cell system was clearly not as large as would be expected from in vitro experiments. This, however, could be explained from the kinetic consideration that natural quenchers of lO2 in the cell would mask the deuterium effect. By experiments with different cell stages it was demonstrated that these two modifying effects were dependent on the intracellular reaction environment. The conclusion is that 1O2 must be the major intermediate responsible for the photodynamic actions in acridine orangesensitized yeast cells.
SOLVENT EFFECTS ON THE SPECTRA OF RETINAL SCHIFF BASES—I. MODELS FOR THE BATHOCHROMIC SHIFT OF THE CHROMOPHORE SPECTRUM IN VISUAL PIGMENTS*
Authors: Kliger D. S. , Milder S. J. , Dratz E. A.
Published: January 2008

Abstract— Retinylidine Schiff base spectra have been investigated in a variety of solvents that were chosen primarily to mimic possible environments of the chromophore in visual pigments. These studies have identified particular amino acid side chains which can have important influences on visual pigment spectra. Most amino acid side chain analogues or solvents which mimic the peptide bond environment have little effect on retinylidine Schiff base spectra. Tyrosine, tryptophan, and cysteine analogues and ionized aspartic and glutamic acid analogues produce pronounced red shifts in the spectra. As is explained in more detail in the following paper the presence of these amino acids in the chromophore “pocket” of the protein is sufficient to account for the spectra of many visual pigments. Calculations of the spectra of protonated Schiff bases under a variety of conditions have been considered in conjunction with the spectral data to provide a model for the nature of the chromophore interactions with its environment.

In solution and in rhodopsin the protonated Schiff base linkage is likely to be associated with an anion. The presence of certain amino acid side chains along the remainder of the retinal chain in the protein can modify the spectrum by altering the polarizability and polarity of the environment. The polarity in the region of the ionone ring appears to be particularly important for shifting the spectrum. In solution the nucleophilicity of the solvent also has an important influence on the anion‐protonated Schiff base region of the chromophore.
THE ROLE OF BIRADICALOID GEOMETRIES IN ORGANIC PHOTOCHEMISTRY
Authors: Michl Josef
Published: January 2008

Abstract— Excited molecules tend to return to the ground state at biradicaloid geometries, i.e. those for which the simple MO description yields two non‐bonding orbitals occupied by only two electrons in the ground state. The nature of electronic states at these geometries and the consequences for the course of photochemical reactions are summarized, using the cases of H2 and H4 as simple models. Several aspects of classification schemes for photochemical reactions are discussed.

Detailed mechanisms of photocycloaddition, of adiabatic photochemical rearrangement of Dewar aromatics, and of luminol chemiluminescence are considered as examples.
ULTRAVIOLET ACTION SPECTRUM FOR FLUOROGEN PRODUCTION IN THE OCULAR LENS
Authors: Borkman Raymond F. , Dalrymple Ann , Lerman Sidney
Published: January 2008

Abstract— …Previous work has demonstrated that fluorescent material (360nm excitation, 440nm emission), whose concentration normally increases with age in human lenses, can be generated artificially by exposing cultured human or animal lenses to UV radiation. In the present paper we report measurements of the rate of production of this fluorescent material in rat lenses in vitro as a function of UV irradiation wavelength. A plot of the observed rate of fluorogen production normalized to constant photon flux vs irradiation wavelength shows little action at 360 or 320nm, increases sharply at 300nm, remains relatively constant in the range 300–280nm, and then exhibits a further gradual rise from 270–250nm. The results on rat lenses are compared with results reported elsewhere for tryptophan in aqueous solution. The action spectrum for photochemical destruction of tryptophan in solution closely parallels that for fluorogen production in rat lenses. This result and other evidence suggest that photochemical destruction of tryptophan might be the initial event in UV‐induced fluorogen production in the ocular lens.
ON THE GENERATION OF THE HYDROXYLATION AGENT FROM SUPEROXIDE RADICAL. CAN THE HABER–WEISS REACTION BE THE SOURCE OF OH RADICALS?
Authors: Czapski Gidon , Ilan Yael A.
Published: January 2008

Abstract— In many biological systems, the role of O2‐ in hydroxylation and toxic processes was assumed to be due to the formation of OH radicals. The Haber‐Weiss reaction (Haber and Weiss, 1934)—(H2O2+ O2‐→ OH + OH‐+ O2) was suggested as the origin of this activity.

In this study it is shown that this reaction pathway is too slow, and that OH is probably formed from the reaction of complexed superoxide with H2O2 or/and from the reduction of Fe(III), bound to biological compounds, by O2‐; the reduced Fe(II) can then react with H2O2 as a Fenton reagent, to yield OH.

It is also shown that singlet oxygen cannot be formed in these biological systems neither from the dismutation of OJ nor from the reaction of O2‐ with OH. Singlet oxygen may be formed from the reduction of metal complexes by O2‐.
LASER PULSE EXCITATION STUDIES OF THE FLUORESCENCE OF CHLOROPLASTS
Authors: Swenberg C. E. , Geacintov N. E. , Breton J.
Published: January 2008

Abstract. The fluorescence yield, φ, as a function of single picosecond laser pulse intensity was experimentally studied in spinach chloroplasts and for chlorophyll a in ethyl ether solution. The progressive decrease in φ with increasing incident intensity for in vivo chlorophyll was found to be adequately explained within the context of continuum bimolecular kinetics with a singlet‐singlet fusion rate constant of γ=5×‐9cm‐3s‐1 at room temperature. We discuss qualitatively how the fluorescence quantum yield depends on the duration and intensity of the incident pulse. The identity of φ vs l (the number of absorbed quanta) curves at the emission maxima of 685 nm and 735 nm for single picosecond pulse mode of excitation is explained within the context of Butler's tripartite model of the fluorescence of chloroplasts at 77 K. Various models relating γ to the singlet exciton diffusion coefficient and the Förster energy transfer rate are used to infer lower bounds to these physical parameters. Predictions and supporting experimental evidence for the tripartite model are discussed.
KINETIC ANALYSIS OF THE PHOTOREACTION (365 nm) BETWEEN PSORALEN AND DNA
Authors: Dall'acqua F. , Magno S. Marciani , Zambon F. , Rodighiero G.
Published: January 2008

Abstract— Psoralen complexed with DNA under irradiation at 365 nm forms monofunctional and bifunctional adducts with pyrimidine bases of DNA. while the fraction of psoralen which remains free in the aqueous solution forms photodimer and photooxidation products. We havc studied the photoreaction betwecn psoralen and DNA from a kinetic point of view. Only some products of this photoreaction could be measured quantitatively. Thus. in order to present a picture of the overall photoreaction. we have represented this by a mathematical model consisting of a system of seven differential equations. Utilizing all the experimental data that it was possible to obtain. we were able to estimate rate constants for formation of all photoproducts. From the general picture thus obtained. we conclude that monofunctional adducts are formed in a four to one ratio to bifunctional adducts. Among the monofunctional photoproducts. 3,4‐cycloadducts occur with a higher yield than 4',5'‐cycloadducts. The combined rate constant of formation of photodimer and photooxidation products of psoralen is small. indicating that they are marginal by‐products relative to the cycloadducts formed in the photoreactions with DNA.
CONVERSION OF LIGHT ENERGY TO ELECTROSTATIC ENERGY IN THE PROTON PUMP OF HALOBACTERIUM HALOBIUM
Authors: Warshel Arieh
Published: January 2008

Abstract— The energetics of the proton pump in Halobacterium halobium is considered on a molecular level. It is proposed that absorption of light by bacteriorhodopsin leads to charge separation and sequential changes in the proton affinities some of the protein groups resulting in proton pumping against the pH gradient. Two alternative models of ‘through‐space’ and ‘through‐bond’ charge separation are proposed. Novel diagrams that describe the energetics of the pumping process are presented. These diagrams can be used both to examine different models of bacteriorhodopsin and for considering other photobiological processes that involve conversion of light energy to electrostatic energy.
MOLECULAR LUMINESCENCE OF SOME ISOALLOXAZINES IN APOLAR SOLVENTS AT VARIOUS TEMPERATURES
Authors: Eweg Jan K. , Müller Franz , Visser Antonie J. W. G. , Veeger Cees , Bebelaar Dick , Voorst Joop D. W. van
Published: January 2008

Abstract— –Spectral properties of isoalloxazines in organic solvents of low polarity are determined at 300 and 77 K. Vibrational structure in the spectra reveals a vibrational mode of 1250cm‐. The pure electronic transition energies are established to a greater accuracy than was done previously and comparison to theoretical data is made. Actual lifetimes up to 10 ns for fluorescence and 300 ms for phosphorescence are found. The ratio of the actual fluorescence lifetime and the radiative lifetime is found to agree well with the quantum yield. Solvent interactions hardly shift the energy of the first electronically excited singlet state but merely affect the Franck‐Condon envelope of the spectrum and the non radiative decay of the chromophore. In albne solutions at 77 K isoalloxazine clusters are formed exhibiting P‐type delayed fluorescence.
FORSTER TRANSFER RATES FOR CHLOROPHYLL a*
Authors: Shipman Lester L. , Housman David L.
Published: January 2008

Abstract— A convenient formula has been derived for the calculation of Forster transfer rates between chlorophyll a molecules. The formula is applicable over limited ranges of absorption maxima positions, Stokes' shifts, solvents, relative orientations and intermolecular distances. The limitations on the applicability of the Forster transfer model are discussed. Finally, some implications for in vivo energy transfer are considered.
PHOTOPHYSICAL PROPERTIES OF NUCLEIC ACID COMPONENTS—1. THE PYRIMIDINES: THYMINE, URACIL, N, N‐DIMETHYL DERIVATIVES AND THYMIDINE
Authors: Becker Ralph S. , Kogan Gregory
Published: January 2008

Abstract— Low‐temperature (and some room temperature) absorption and emission, fluorescence and phosphorescence, data including quantum yields and lifetimes have been obtained from the title pyrimidine bases as a function of the nature of the solvent environment. Modest vibrational resolution has been observed for the first time in the absorption spectra, particularly for thymine and uracil. The excitation spectra also show structure. The quantum yields of fluorescence (φF) and phosphorescence are independent of the excitation wavelength. Thymine, thymidine and uracil have profoundly different photophysical properties in polar‐aprotic vs polar‐protic solvents. The N, N‐dimethyl substitution of thymine and uracil produces photophysical changes comparable to the solvent change for the unsubsti‐tuted bases. The species involved in the emission processes is the keto (lactam) form. It is probable that 1,3(n,π*) state(s) has(have) changed order relative to a lowest 1(π,π*) state as a consequence of both the solvent change and N, N‐dimethyl substitution. The lowest triplet state is assigned as 3(n π*). We propose that an important factor contributing to the previously reported excitation wavelength dependence of φF and φT1 (φisc) for nucleic‐acid components is the equilibrium coexistence of H‐bonded and non‐H‐bonded forms each having different photophysical properties. Consideration is given of the impact of the significantly different photophysical properties of nucleic‐acid bases as a function of the nature of the solvent upon the photochemical properties.
NATURE OF PEROXY INTERMEDIATES PRODUCER BY THE PHOTOSENSITIZED OXYGENATION OF DIETHYL SULFIDE AND PHENYLBENZOYL DIAZOMETHANE: KINETIC STUDIES BY CO‐OXIDATION WITH 4‐MONO SUBSTITUTED DIPHENYL SULFIDES
Authors: Ando Wataru , Kabe Yoshio , Mivazaki Hajime
Published: January 2008

Abstract— Competitive oxidations of pairs of 4‐monosubstituted diphenyl sulfides by intermediates produced in the photosensitized oxygenation of diethyl sulfide and phenylbenzoyl diazomethane were carried out in methanol and benzene, respectively. Relative rates of oxidation correlate well with Ham‐mett's a, and p values of ‐0.61 (oxidation in the presence of diethyl sulfide) and ‐0.32 (oxidation in the presence of phenylbenzoyl diazomethane) show that the diphenyl sulfides oxidizing intermediates have electrophilic character. In the photosensitized oxygenation of sulfides and diazo compounds, peroxy intermediates (a persulfoxide and a carbonyl oxide, respectively) have been proposed as the most probable intermediates.
MICROENVIRONMENT OF AROMATIC HYDROCARBONS EMPLOYED AS FLUORESCENT PROBES OF LIPOSOMES
Authors: Lianos P. , Mukhopadhyay A. K. , Georghiou S.
Published: January 2008

Abstract— The enhancement of weakly allowed vibronic transitions in the fluorescence spectra of pyrene, 1,12‐benzoperylene and naphthalene, which we previously found to be the result of the reduction of the molecular symmetry caused by ground state complex formation with polar solvents, has been employed in the present work to study the microenvironment of these aromatic hydrocarbons when incorporated as fluorescent probes into egg phosphatidylcholine and dipalmitoyl phosphatidylcholine liposomes. The probes are found to interact and form ground state molecular complexes with polar groups of the liposomes. For egg phosphatidylcholine the degree of enhancement is matched by that in butanol, methanol and dioxane for the three probes, respectively. For dipalmitoyl phosphatidylcholine the matching solvents are ethanol, dimethylformamide and dioxane below the phase transition, while they are ether, methanol and dioxane above it. Thus, above the phase transition pyrene and 1,12‐benzoperylene penetrate further into the liposomes, while naphthalene retains approximately the same location.
PHOTOELECTROCHEMICAL STUDY OF CHLOROPHYLL‐a MULTILAYERS ON SnO2 ELECTRODE
Authors: Miyasaka Tsutomu , Watanabe Tadashi , Fijjishima Akira , Honda Kenichi
Published: January 2008

Abstract—

Photoelectrochemical behaviour of Chl‐a multilayers, built up on SnO2 optically transparent electrode by means of the Langmuir technique, was investigated in an electrolyte solution with or without hydroquinone as a reducing agent. Quantum efficiencies of the anodic photocurrents in the presence of hydroquinone tended to decrease with increasing number of layers. In the electrolyte without hydroquinone, the cathodic photocurrents were observed in the presence of dissolved oxygen. A possibility of a reaction of water with the oxidized Chl‐a is suggested.
TIME‐RESOLVED FLUORESCENCE SPECTRA OF TRYPTOPHAN IN MONOMERIC GLUCAGON*
Authors: Cockle S. A. , Szabo A. G.
Published: January 2008

Abstract— The fluorescence decay of tryptophan‐25 in monomeric glucagon at pH 8.2 was measured at a series of emission wavelengths using pulsed laser excitation and single photon counting techniques. Double exponential kinetics were consistently observed, with time constants 3.26 and 1.11 ns. This allowed the steady‐state emission spectrum to be resolved into two components with differing intensities but similar emission maxima near 350 nm. Decay parameters were almost unchanged in the presence of 5.5 M guanidinium chloride. The dual emission is thought to reflect different conformers of the indole ring or of the peptide chain.
EVIDENCE FOR ELECTROPHILIC CHARACTER IN OXYGEN ATOM TRANSFER BY CARBONYL OXIDES
Authors: Agarwal Sudhir K. , Murray Robert W.
Published: January 2008

Abstract— Naphthalene was oxidized by carbonyi oxides produced by singlet oxygen oxidation of p, p‐disubstituted diphenyldiazomethanes. Yields of naphthol products correlate with Hammett σ constants giving ρ=+0.93. The results are interpreted as indicating the electrophilic character of these oxidations.
PHOTOOXYGENATION OF MESO‐TETRAPHENYLPORPHYRIN METAL COMPLEXES
Authors: Smith KevinM. , Brown Stanley B. , Troxler Robert F. , Lai Jan‐Ji
Published: January 2008

Abstract Cadmium(II), zinc(II), magnesium(II), and bis‐[thallium(I)] complexes of meso‐tetraphenyl‐porphyrin undergo unsensitized photooxygenation to yield a bilitriene derivative as the final product. The reaction has previously been shown to involve singlet oxygen (Matsuura et al., 1980); on the basis of mass spectrometry of products from 16O2 and 18O2 experiments, and characterization of the initial photoproduct, the reaction is shown to proceed by a mechanism in which one oxygen molecule adds to the metalloporphyrin to give a metallobilitriene. In the subsequent work‐up, demetalation and addition of two hydrogen atoms gives the final product.
POSSIBLE IN VIVO FORMATION OF LUMICHOLCHICINES FROM COLCHICINE BY ENDOGENOUSLY GENERATED TRIPLET SPECIES
Authors: Brunetti I. L. , Bechara E. J. H. , Cilento G. , White E. H.
Published: January 2008

Abstract In Colchicum autumnale L., colchicine is accompanied by its photoproducts, mainly β‐lumicholchicine, even in parts not exposed to light such as the corm of plants grown in the dark. The transformation of colchicine into lumicolchicines can be efficiently accomplished in vitro by energy transfer from enzyme‐generated triplet species to colchicine, thus providing additional evidence for‘photobiochemistry without light’.
THE BLUE ANOMALOUS EMISSION OF LARGE AND SMALL PHYTOCHROME*
Authors: Holzwarth Alfred R. , Braslavsky Silvia E. , Culshaw Stephen , Schaffner Kurt
Published: January 2008

–Small and immunoaffinity‐purified large phytochrome (Pr and Pfr) show a so‐called anomalous fluorescence with λemmax= 470 and 440 nm, respectively, when irradiated within the blue absorption band. Model studies indicate that this emission arises from a dipyrromethenone partial structure produced by a nucleophilic addition to the central carbon C‐10 of the bilindione chromophore. The anomalous emitter of phytochrome is thus similar to one bilirubin conformer which has previously been found to contribute to the absorption and emission of the bile pigment.
STUDIES ON THE TRIPLET EXCITED STATE OF 4‐THIOURIDINE
Authors: Salet C. , Bensasson R. V. , Favre A.
Published: January 2008

Abstract— The absorption spectra, lifetimes, extinction coefficients and intersystem crossing quantum yields of the lowest triplet T1 of 4‐thiouridine have been determined both in acetonitrile and in water. An ordering of 1,3(n,π)* and 1,3(π,π)* states is suggested. Triplet quenching rate constants with various pyrimidine bases or amino acids are reported.
PHOTOSENSITIZED LYSIS OF LIPOSOMES BY HEMATOPORPHYRIN DERIVATIVE
Authors: Grossweiner Leonard I. , Goyal Greesh C.
Published: January 2008

The spectral properties and efficiency for photosensitizing the lysis of phosphatidylcholine liposomes have been measured for the components of hematoporphyrin derivative (Hpd) after alkaline hydrolysis and fractionation by polyacrylamidc gel chromatography. Two major and two minor Hpd fractions have been identified whose spectral properties correlate with the anoxic sensitizing efficiency and the oxygen enhancement ratio (OER). The fastest moving fraction, which is the putative biologically active component, comprised one‐third of the starting material and had OER = 2.7. Liposome lysis by this fraction was inhibited in the presence of human serum albumin at concentration ratios comparable to those employed for photoradiation therapy. The present results show that Hpd can act as an oxic and anoxic photosensitizer of a model biomembrane and suggest that separation from serum proteins is required for in vivo photosensitization.
LIGHT‐INDUCED ELECTRON TRANSFER REACTIONS BETWEEN CHLOROPHYLL AND QUINONE IN ELECTRICALLY‐CHARGED VESICLES: EFFECTS OF COUNTERIONS LOCATED IN EITHER THE INNER OR OUTER AQUEOUS PHASES ON RADICAL FORMATION AND DECAY*
Authors: Fang Yifei , Tollin Gordon
Published: January 2008

Abstract— The presence of relatively low concentrations of counterions (millimolar in the case of univalent ions and micromolar in the case of polyvalent ions) in either the inner or outer aqueous compartments of electrically charged lipid bilayer vesicles containing chlorophyll in the presence of benzoquinone has been shown to produce large effects on radical formation and decay as measured by laser flash photolysis. With negatively charged vesicles having no added salt inside, salt ions added to the external phase caused radical yields to markedly decrease, with no change in decay kinetics. When salt was present only in the interior phase, radical decay became biphasic and the ability of externally added salt to affect radical yields was greatly diminished.

With positively charged vesicles having no added salt inside, salt addition to the external medium caused both the radical decay rate and yield to decrease. The presence of interior salt, however, caused radical decay to become faster and, as was the case with negative vesicles, greatly reduced the effects of salt added externally.

These results have been interpreted in terms of electrostatic and structural effects of charge neutralization by counterions on the dynamics of radical‐ion separation and recombination.
ENERGY TRANSFER AMONG THE CHROMOPHORES OF C‐PHYCOCYANIN FROM Anabaena variabilis USING STEADY STATE AND TIME‐RESOLVED FLUORESCENCE SPECTROSCOPY
Authors: Switalski Steven C. , Sauer Kenneth
Published: January 2008

Abstract We have investigated the model of energy transfer between sensitizing (s) and fluorescing (f) chromophores for the αβ monomer and for the separated α and β subunits of C‐phycocyanin from Anabaena variabilis using fluorescence emission spectroscopy, fluorescence excitation polarization, and picosecond‐resolved fluorescence decay kinetics. The fluorescence emission maximum occurs at 640 nm for all samples. The fluorescence excitation polarization is constant (P= 0.40) across the absorption hand for the α subunit, but it increases across the absorption band towards longer wavelength for the β subunit and the αβ monomer. The fluorescence decay kinetics exhibit two exponential lifetimes of 1.3‐1.5 ns and 340‐500 ps for the αβ monomer and for the α and β subunit preparations.

We attribute the change in polarization across the absorption band to energy transfer among the three chromophores in the αβ monomer and among the two chromophores in the separated β subunit. The constant, relatively high polarization in the separated a subunit, having only one chromophore, is consistent with the absence of both energy transfer and chromophore rotation. The concentration of the α subunit did not affect the decay kinetics, suggesting that the short lifetime component does not arise from aggregation of the α subunits. The biexponential decay kinetics of the α subunit cannot be explained using the sensitizing‐fluorescing model. The possibility of conformational interactions is under investigation.
LASER FLASH PHOTOLYSIS OF INDOLE IN THE PRESENCE OF AMINO ACIDS
Authors: Previtali C. M.
Published: January 2008

The laser flash photolysis of indole at 265 nm in the presence of glycine, proline and hydroxy proline was studied. The relative yields of c aq, triplet state, and indole cation radical were determined in the absence and in the presence of the amino acids. The yields were determined as a function of laser intensity and the values at very low intensity were compared with the fluorescence quenching results. It was concluded that in these conditions the photoionization of indole occurs via the fluorescent state. From the curves of triplet yield vs laser intensity, the triplet quantum yield extrapolated at low laser intensity was obtained, φr = 0.55 φ 0.05, relative to the literature value of 0.15 for φeag. This gives φF+φeaq= 1.0 ± 0.1 at room temperature. When proline and hydroxy proline were used as singlet quenchers, the yield of In was greater than the yield of caq. This was considered as evidence that a fraction of the quenching processes leads to complete electron transfer from indole to the amino acids.
CYTOCHROME P‐450/420 IN PLANT PLASMA MEMBRANES: A POSSIBLE COMPONENT OF THE BLUE‐LIGHT‐REDUCIBLE FLAVOPROTEIN‐CYTOCHROME COMPLEX*
Authors: Kjellbom Per , Larsson Christer , Askerlund Per , Schelin Cecilia , Widell Susanne
Published: January 2008

Abstract— Carbon monoxide difference spectra and pyridine binding spectra indicate the presence of cytochrome P‐450/420 in plasma membranes from cauliflower inflorescences. Mild lithium dodecylsulfate polyacrylamide gel electrophoresis shows only one heme staining band in the plasma membrane fraction at an apparent molecular weight of 93 kiloDalton. This band is suggested to be due to a cytochrome P‐450/420 dimer, in view of the known molecular weights of animal cytochromes P‐450/420. The plasma membrane‐bound cytochrome P‐450/420 is probably identical to the blue‐light‐reducible b‐type cytochrome of plant plasma membranes, which has been inferred to have a role in photomorphogenesis.
XANTHENE DYES AS SENSITIZERS FOR THE PHOTOREDUCTION OF WATER
Authors: Mau A. W.‐H. , Johansen O. , Sasse W. H. F.
Published: January 2008

Abstract— Some photochemical and photophysical properties of a group of xanthene dyes have been studied in relation to their roles as sensitizers for the photoreduction of water. New spectroscopic and kinetic measurements have been carried out with these dyes. The triplet states of the dyes undergo energy‐transfer and electron‐transfer, but with rate constants differing by two orders of magnitude in favour of the former pathway. The very efficient transfer of triplet energy from a group of dyes to an acceptor molecule led to the design of a greatly improved system for the photochemical production of hydrogen.
VACUUM‐ULTRAVIOLET PHOTOACOUSTIC SPECTROSCOPY OF BIOLOGICAL MATERIALS USING SYNCHROTRON RADIATION AS A LIGHT SOURCE
Authors: Inagaki Takashi , Ito Atsushi , Motosuga Masatsugu , Hieda Kotaro , Kobayashi Katsumi , Maezawa Hiroshi , Ito Takashi
Published: January 2008

Abstract— Photoacoustic measurements of biological materials such as DNA, lysozyme, squalene and yeast cells were performed for the first time in the vacuum‐UV region above 150 nm using the gas‐microphone technique and synchrotron radiation as a light source. The samples studied were in a form of thin film supported on a self‐supporting collodion film. The results obtained for the phase of the photoacoustic signal were found consistent with the predictions from the simple one‐dimensional theory. The signal amplitudes obtained as a function of the incident wavelength were interpreted as giving the absorptance (the fraction of the incident photon energy dissipated in the sample) spectrum.
EFFICIENT PHOTOREDUCTION OF METHYLVIOLOGEN BY METALLOPHTHALOCYANINE SENSITIZERS
Authors: Ohtani Hiroyuki , Kobayashi Takayoshi , Tanno Takashi , Yamada Akira , Wöhrle Dieter , Ohno Takeshi
Published: January 2008

Abstract— Metallophthalocyanines (MPc) and tetrasubstituted magnesium phthalocyanines (MgPcR4) were investigated as sensitizers for the photoreduction of methylviologen (MV2+) under visible light(420–800 nm) irradiation using disodium ethylenediaminetetraacetic acid (Na2EDTA) as an electron donor in dimethyl formamide (DMF)‐water mixture. Magnesium phthalocyanine and aluminium phthalocyanine were found to be the most efficient sensitizers among nine MPc's examined (M = 2Li, 2Na, Mg, Ca, Al(Cl), Fe, Ni, Co, and Zn). The following sequence of the efficiency among MgPc and MgPcR4's was obtained.
VACUUM ULTRAVIOLET CIRCULAR DICHROISM OF DOUBLE STRANDED NUCLEIC ACIDS
Authors: Sutherland John C. , Lin Bohai , Mugavero Jo Ann , Trunk John , Tomasz Maria , Santella Regina , Marky Luis , Breslauer Kenneth J.
Published: January 2008

The vacuum ultraviolet (VUV) circular dichroism (CD) of double stranded DNA and RNA is greater in amplitude than the CD of these molecules for wavelengths longer than 200 nm. The amplitude of the VUV‐CD depends on the base composition of DNA, with guanine‐cytosine base pairs contributing more intensity than adenine‐thymine base pairs. The shape and amplitude of the VUV‐CO are better indicators of nucleic acid conformation (A, B or Z) than are those of the longer wavelength CD. We illustrate the unique features of VUV‐CD with specific examples. In the presence of Cs+ and ethanol, VUV‐CD reveals that poly(dA‐dC)poly(dG‐dT) forms a right handed double helix despite the inversion of the longer wavelength CD, which usually is used as a benchmark for the left‐handed form. The greater magnitude of the VUV‐CD of DNA and RNA compared to longer wavelengths means that the VUV‐CD is less susceptible to distortion by the induced CD of UV‐absorbing ligands like mitomycin C and N‐2‐acetylaminofluorene.
PHOTOREDUCTION OF VIOLOGENS WITH NADPH AS REVERSIBLE ELECTRON DONOR
Authors: Aono Shigetoshi , Kita Tatsuya , Okura Ichiro , Yamada Akira
Published: January 2008

Abstract— The photoreduction of viologens with NADPH as an electron donor was investigated. As the photosensitizer in that reaction, ZnTPP33‐ and HmP were applied. HmP dissolved by CTAB or Triton X‐100 was a more active photosensitizer than ZnTPPS33‐. The reduction rate of viologen under steady state irradiation depends remarkably on the type of surfactant used for dissolving HmP. The effect of the surface charge of micelle was examined by laser flash photolysis.
DEPLETION OF CUTANEOUS GLUTATHIONE BY ULTRAVIOLET RADIATION*
Authors: Connor Michael J. , Wheeler Larry A.
Published: January 2008

Supplemental antioxidants may have a role in ameliorating or preventing the actinic damage that can lead to cutaneous disorders such as skin cancer, hyperpigmentation, and premature aging. Glutathione is an important endogenous antioxidant and fulfills various protective functions in the skin. Irradiation of hairless mice with short (UVB) or long (UVA) wavelength ultraviolet radiation or with UVA combined with a photosensitizing psoralen (PUVA) can deplete skin glutathione levels. Ultraviolet B irradiation causes rapid transient fluctuations in the epidermal glutathione level and the relative amount present as the oxidized form. Ultraviolet A irradiation can deplete epidermal and dermal glutathione for several hours but requires much higher doses than UVB. PUVA treatments may lead to extensive and prolonged depletions of epidermal and dermal glutathione, the severity of which is dependent on the psoralen dose and may last for several days. These transient depletions, oxidations, and sometimes rapid recoveries of cutaneous glutathione levels are compatible with a role for glutathione as an endogenous photoprotective agent in the skin. Experimental evidence supports such a role: for example severe skin edema develops in mice only after about 50% of the glutathione has been depleted by PUVA treatment. Although different mechanisms are involved in each case, glutathione depletion may contribute to the production of phototoxicity by UVB, UVA, and by PUVA. Understanding the depletion mechanisms may allow the development of strategies aimed at preventing loss of cutaneous glutathione, and at reinforcing the natural protective functions of this critical cell component.
PHOTOCHEMICAL SENSITIZATION BY 7‐METHYLBENZ[c]ACRIDINE AND RELATED COMPOUNDS
Authors: Burt Christopher D. , Moore Douglas E.
Published: January 2008

Abstract. The carcinogenic environmental contaminant, 7‐methylbenz[c]acridine (7MBAC), generates singlet oxygen in high yield when irradiated with near‐UV light. The photophysical and photochemical properties are reported for 7MBAC and several related acridine, anthracene and benzanthracene derivatives in aqueous surfactant solutions and in methanol. Singlet oxygen production was assessed by measuring the rates of oxygen uptake in irradiated solutions containing oxidizable substrates, such as 2,5‐dimethylfuran or histidine. Relative yields of free radical production from the irradiated sensitizers were determined by the initiation of free radical polymerization of acrylamide.
THE α‐OXIDASE SYSTEM OF YOUNG PEA LEAVES (Pisum sativum) AS GENERATOR OF ELECTRONICALLY EXCITED STATES. EXCITATION IN THE DARK UNDER NATURAL CONDITIONS
Authors: Salim‐Hanna Marta , Campa Ana , Cilento Giuseppe
Published: January 2008

Abstract. The aerobic oxidation of saturated long chain fatty acids to the lower aldehyde and CO2 catalyzed by the α‐oxidase system of young leaves from germinating Pisum sativum results in concomitant excitation of the chloroplasts or/and fractions present in the α‐oxidase preparation. The excitation is attested to by both chlorophyll emission and Hill activity. This is the first case of photobiochemistry without light within a natural system.
FLUORESCENCE LIFETIME OF ACRIDINE ORANGE IN SODIUM DODECYL SULFATE PREMICELLAR SOLUTIONS
Authors: Miyoshi Norio , Hara Kiyoaki , Yokoyama Issei , Tomita Giiti , Fukuda Masaru
Published: January 2008

Abstract— The absorption and fluorescence spectra, and the fluorescence lifetime of acridine orange (AO) were measured in a wide range of the sodium dodecyl sulfate (SDS) concentration below and above the critical micelle concentration (cmc). The fluorescence consisted of two components with different lifetimes; short (<3 ns) and long (>3 ns). The short and long lifetime components are attributed to the AO monomer and dimer associated with detergent, respectively. The lifetime of the dimer increased with increasing the SDS concentration just below the cmc. It decreased suddenly to a constant value just above the cmc. The lifetime of the monomer showed only a slight increase in the concentration range of SDS employed.