bluuebunny/crossref_metadata_2025 huggingface dataset:
THE PHOTOLYSIS OF 5‐NITROFURFURAL IN AQUEOUS SOLUTIONS: NUCLEOPHILIC SUBSTITUTION OF THE NITRO‐GROUP
Authors: Busker Ruud W. , van Henegouwen Gerard M. J. Beijersbergen
Published: January 2008

Abstract— The photolysis in aqueous neutral solutions of 5‐nitrofurfural (NFA), an important metabolite of nitrofurans used as medicines, was investigated. Upon UV‐A irradiation NFA loses up to 70 mol % nitrite, with formation of 5‐hydroxymethylene‐2(5H)‐furanone, a new substance. When Cl−1 is present 5‐chlorofurfural is an important photoproduct. Photo‐induced addition of either OH or CI−1, followed by thermochemical elimination of NO2−1, is the proposed mechanism. Furthermore, NFA reacts with nitrite yielding nifuroxim. The possible role of the NFA photolysis in the occurrence of (photo)biological effects of NFA is discussed.
INDUCTION OF BIOLUMINESCENCE IN THE MARINE FISH, Porichthys, BY Vargula (CRUSTACEAN) LUCIFERIN. EVIDENCE FOR de novo SYNTHESIS OR RECYCLING OF LUCIFERIN
Authors: Thompson Eric M. , Nafpaktitis Basil G. , Tsuji Frederick I.
Published: January 2008

Abstract— The marine fish, Porichthys notatus, emits light by a classical luciferin‐luciferase reaction whose components are similar, if not identical, to those found in the luminescent crustacean, Vargula. Porichthys is divided geographically into a southern luminescent and a northern nonluminescent population. Specimens of nonluminescent Porichthys can be induced to become luminescent by injection or ingestion of Vargula luciferin. After feeding a known quantity of Vargula luciferin, light emitted by Porichthys was monitored for a 2‐yr period. Summation of light produced during each bioluminescence episode demonstrated that the total quanta emitted over 2 yr exceeded the theoretical yield from the administered luciferin. These results indicate that the administered luciferin either recycles or induces de novo synthesis of additional luciferin in Porichthys.
PRINCIPLES AND APPLICATIONS OF FLUORESCENCE TECHNIQUES IN BIOPHYSICAL CHEMISTRY*
Authors: Geacintov Nicholas E.
Published: January 2008

Abstract— Fluorescence is widely used as a probe of the properties of ligand‐biopolymer complexes or adducts, proteins, nucleic acids and membranes. The principles and techniques utilized in characterizing the basic fluorescence properties of a system of fluorophore‐biopolymer complexes are outlined. The different approaches utilized include a correlation of fluorescence decay profiles obtained by time‐correlated single photon counting techniques with (1)steady‐state fluorescence excitation and emission spectra, (2)relative fluorescence quantum yields, (3)fluorophore‐accessibilities investigated by quenching techniques, and (4)ligand‐macromolecule binding equilibria.
FLUORESCENCE OF MELANIN‐DEPENDENCE UPON EXCITATION WAVELENGTH AND CONCENTRATION
Authors: Gallas James M. , Eisner Melvin
Published: January 2008

Abstract— An introduction to the fundamental characteristics of synthetic melanin fluorescence is presented. The particular difficulties associated with the detection and reduction of the relatively weak signal are discussed and a technique is described for correcting the fluorescence spectra for attenuation of the excitation and emission beams. Spectra are reported for the excitation wavelength range 340–400 nm and an emission range of 360–560 nm. The concentration dependence of the corrected fluorescence signal is examined and is shown to be linear. The variation of the fluorescence spectra with excitation wavelength suggests a two‐component fluorescence, for the wavelength range studied. The presence of an isosbestic point in the spectra is used to identify the fluorophores as components of a reaction equilibrium. The possible relationship of this equilibrium to that associated with the melanin photo ESR is discussed
A FLOW LINEAR DICHROISM STUDY OF THE ORIENTATION OF 4′,5′‐PSORALEN‐DNA PHOTOADDUCTS
Authors: Vigny Paul , Blais Jocelyne , Ibanez Victor , Geacintov Nicholas E.
Published: January 2008

Abstract— The flow linear dichroism properties of covalent adducts derived from the photochemical binding of various psoralen derivatives to salmon sperm DNA were investigated. The psoralens studied include bifunctional derivatives (8‐methoxypsoralen,5‐methoxypsoralen, tetrahydropyrido [3,4: 4‘,5’] psoralen) and monofunctional derivatives (pyrido [3,4‐c] psoralen, 7‐methylpyrido [3,4‐c] psoralen, 3‐carbethoxypsoralen). The orientation of the psoralen moieties (furan‐side monoadducts) relative to the orientation of the DNA bases was determined. All of the furan‐side monoadducts are characterized by a similar orientation, with mean angles between the psoralen moiety and the normals of the planes of the DNA bases ranging between 70° and values close—but not equal—to 90°. The results are consistent with a pseudo‐intercalative adduct geometry, most probably involving stacking interactions with the DNA bases.
PENETRATION OF LIGHT INTO THE UTERUS OF PREGNANT MAMMALS
Authors: Jacques Steven L. , Weaver David R. , Reppert Steven M.
Published: January 2008

Abstract— The fraction of incident light which reaches the uterine lumen in pregnant rats and guinea‐pigs was studied with a surgically implanted optical fiber. Penetration of visible spectrum light (400–650‐nm wavelengths) into the uterus was examined. The effects of clipping the hair, retracting the skin, and retracting the abdominal wall on the penetration of light was also assessed to determine the relative amount of light transmitted through each layer between the external environment and the uterus. The presence of significant transmission at biologically relevant wavelengths raises the possibility that environmental lighting may reach the fetus and influence development
EXCITED TRIPLET‐SINGLET INTERSYSTEM CROSSING IN ISOALLOXAZINES
Authors: Richter Carol , Hub Walter , Traber Rainer , Schneider Siegfried
Published: January 2008

Abstract— Higher excited triplet states originating from the lowest triplet state of isoalloxazines by absorption of light with Λ ‐ 600 nm undergo “inverse” intersystem crossing to the singlet manifold [φ(Tn‐Sm) = 8 × 10‐3] followed by rapid internal conversion and “normal” fluorescence S1‐S0 with Λm= 540 nm.
DNA DAMAGE AND REPAIR FOLLOWING TREATMENT OF V‐79 CELLS WITH SULFONATED PHTHALOCYANINES
Authors: Hunting Darel J. , Gowans Bonnie J. , Brasseur Nicole , Lier Johan E. van
Published: January 2008

Abstract. Two gallium‐phthalocyanines were tested for their effects on cell survival, trypsinization, and DNA strand breaks in intact and permeable cells, measured by alkaline elution. Gallium‐tetrasulfophthalocyanine was not phototoxic to cells and caused no measurable DNA damage in intact cells, while a mixture of less sulfonated gallium‐sulfophthalocyanines, containing an average of 2.7 sulfonates per molecule, was very phototoxic and induced DNA strand breaks and/or alkali‐sensitive sites; however, both drugs were equally effective at inducing DNA strand breaks in permeable cells. The DNA damage was rapidly repaired in intact cells; this process was not inhibited by aphidicolin, an inhibitor of DNA polymerases alpha and delta, under conditions in which DNA replicative synthesis was inhibited by more than 90%.
ACTION SPECTRA FOR THE INDUCTION OF PYRIMIDINE(6‐4)PYRIMIDONE PHOTOPRODUCTS AND CYCLOBUTANE PYRIMIDINE DIMERS IN NORMAL HUMAN SKIN FIBROBLASTS
Authors: Rosenstein Barry S. , Mitchell David L.
Published: January 2008

Abstract. Normal human skin fibroblasts were exposed to 265–313‐nm monochromatic UV wavelengths and the yield of pyrimidine(6‐4)pyrimidone photoproducts [(6‐4) photoproducts] and cyclobutane pyrimidine dimers (dimers) measured by radioimmunoassay. The action spectra for the induction of these two types of DNA damage were very similar for wavelengths from 254 to 302 nm. However, the action spectrum value for (6‐4) photoproduct production was less than half the value obtained for dimer induction by 313‐nm UV. Cells were also exposed to the UV produced by a broad‐spectrum fluorescent sunlamp (280–360 nm, peak at 313 nm) under conditions in which various wavelength components were removed from the spectrum. For exposures in which the (6‐4) photoproducts and dimers were induced primarily by wavelengths shorter than 310 nm, their rates of induction, relative to 254‐nm‐irradiated cells, were similar. However, the level of (6‐4) photoproduct production was about three‐fold lower than dimer induction for sunlamp irradiations in which the 315–330‐nm component of this source was primarily responsible for the formation of this damage. These results are consistent with the conclusion that for treatments in which (6‐4) photoproducts are produced by wavelengths in the 310–320‐nm range, which represent the region of absorption peaks for these photoproducts, both the induction and photolysis of (6‐4) photoproducts occur simultaneously during irradiation.
TUMOR LOCALIZATION AND PHOTOSENSITIZATION BY SULFONATED DERIVATIVES OF TETRAPHENYLPORPHINE
Authors: Kessel David , Thompson Paul , Saatio Karen , Nantwi Kwaku D.
Published: January 2008

Abstract. We have examined transport, sites of photosensitization, and plasma protein binding by sulfonated derivatives of tetraphenylporphine in vitro and tumor localization of these products in vivo. Studies carried out in culture indicate that the mono‐sulfonated porphyrin sensitized mainly at intracellular loci while drugs with 2 or 3 sulfonates caused photodamage at membrane sites. But the number and distribution of sulfonates were majors factor in both accumulation and efficiency of photodamage. The product with 2 adjacent sulfonates was the most potent photosensitizer; the presence of more or fewer sulfonate residues led to reduced uptake and sensitization. Steady‐state accumulation of drugs with one, two (opposite), three or four sulfonates was rapid, while uptake of the disulfonated (on adjacent rings) porphine was slower. Products bearing one to four sulfonates localized equally well in vivo, but sites of localization varied considerably. Drugs with one sulfonate, or two sulfonates on adjacent rings partitioned into neoplastic cells, analogs with two (opposite), three or four sulfonates partitioned to tumor stroma. Plasma binding studies show that drugs with one or two (adjacent) sulfonates bound to VLDL, LDL and HDL components of plasma, while the tri and tetra‐sulfonated analogs bound progressively more to albumin. These results suggest that tumor localization can occur via two pathways: one mediated by lipoprotein binding and leading to dye accumulation in neoplastic cells, another associated with albumin binding and leading to dye accumulation in stromal elements of neoplastic tissues.
TOWARD THE LINK BETWEEN MEMBRANES TRANSPORT AND PHOTOPERCEPTION IN PLANT
Authors: Blatt Michael R.
Published: January 2008

“The processes of growth and morphogenesis represent the movements of chemical groups. at

certain rates and in certain definite directions in space. within the organism. Thus, growth and

morphogenesis represent transport processes which, in common with the more popular membrane transport, must be described by vector quantities, having both magnitude and direction in space.
APPLICATION OF TIME‐RESOLVED FLUOROMETRY TO THE RESOLUTION OF PORPHYRIN‐PHOTOPRODUCT MIXTURES
Authors: Valat Pierre , Reinhart Gregory D. , Jameson David M.
Published: January 2008

Abstract—The quantitation of porphyrin and its photoproducts in biological samples is important in diverse applications including, but not limited to, tumor phototherapy. Differences in fluorescence properties, e.g., emission spectra and lifetimes, of the various components can be utilized to resolve the individual contributions. In this report time‐resolved measurements using multifrequency phase and modulation rluorometry are employed to study mixtures of protoporphyrin IX and photoprotopor‐phyrin. Individual lifetimes of 14.85 ns and 5.95 ns were determined for dioxane solutions of protoporphyrin IX and photoprotoporphyrin, respectively. These lifetime values were utilized to resolve the individual emission spectrum of each component in the mixture using the phase‐resolved Huorometry technique.
PHOTOREDUCTION OF SOME NITROBIPHENYL ETHER HERBICIDES TO NITRO RADICAL ANIONS BY β‐CAROTENE AND RELATED COMPOUNDS
Authors: Rao D. N. Ramakrishna , Mason Ronald P.
Published: January 2008

Abstract—The nitrobiphenyl ether herbicides; 4‐nitrobiphenyl ether, bifenox, nitrofen, acifluorfen, acifluorfen‐methyl, acifluorfen‐ethyl, and oxyfluorfen were reduced to their corresponding nitro radical anions by visible light in the presence of β‐carotene, lycopene, retinol, retinal, retinoic acid and retinyl acetate in anaerobic solutions at high pH. It was more difficult to obtain spectra of bifenox, nitrofen and oxyfluorfen than acifluorfen derivatives, probably due to their poor solubilities. In neutral solutions the steady‐state concentration of the nitro radical anions was low due to their faster rate of dispropor‐tionation and the poor solubility of β‐carotene. In the presence of retinal, the nitro radical anion of acifluorfen was produced at pH 7.4. Compounds containing conjugated double bonds such as crotonaldehyde and 2.4‐hexadienal also reduced acifluorfen and its derivatives to their respective nitro radical anions in the presence of light. Ubiquinone‐50 which does not contain conjugated double bonds in the side chain did not reduce acifluorfen under similar conditions.
PHOTOSENSITIZED INACTIVATION OF DNA BY MONOCHROMATIC 334‐nm RADIATION IN THE PRESENCE OF 2‐THIOURACIL: GENETIC ACTIVITY AND BACKBONE BREAKS
Authors: Peak Meyrick J. , Ito Atsushi , Foote Christopher S. , Peak Jennifer G.
Published: January 2008

AbstractMonochromatic 334‐nm radiation delivered under aerobic conditions inactivates the genetic activity (ability to transform auxotrophic recipient cells to nutritional prototrophy) of isolated transforming Bacillus subtilis DNA. The presence of superoxide dismutase (SOD), catalase, and mannitol reduces the 334‐nm inactivation. The rate of inactivation of the genetic activity by 334‐nm radiation is enhanced fivefold by the sensitizer 2‐thiouracil (s2Ura). This enhancement is substantially reversed when the irradiations are performed in the presence of mannitol, and, to a lesser extent, SOD. Catalase slightly reduces the s2Ura enhancement of 334‐nm inactivation of transforming activity. Backbone breaks induced in the same DNA by aerobic 334‐nm radiation were also enhanced markedly by the presence of s2Ura; this enhancement was reversed by the presence of mannitol and, to a lesser extent, SOD during irradiation. Catalase had no effect upon s2Ura‐enhanced, 334‐nm‐induced SSBs. Whereas DNA breakage may be responsible for a portion of the inactivation of the DNA by the photosensitized reaction between s2‐Ura and 334‐nm radiation, it is not the only inactivating lesion, because the yield of SSBs per lethal hit per unit length of DNA is not constant for all the irradiation conditions studied. The results support a complex role for active oxygen species in inactivation of transforming activity and DNA breakage by s2Ura‐enhanced 334‐nm radiation. They are also consistent with the formation of superoxide anion, hydroxyl radical, and possibly also singlet molecular oxygen, generated from ground‐state molecular oxygen by reactive s2Ura in both Type I and II reactions.
ENERGY CONVERSION IN THE DECAY OF TRIPLET LUMIFLAVIN IN THE PRESENCE OF FERRI‐ AND FERROCYANIDE
Authors: Naman S. A.
Published: January 2008

Abstract—Flash photolysis at 450 nm has been used to study the quenching of the excited triplet state of lumiflavin and the transient species formed in subsequent reactions in deaerated phosphate buffer (pH 6.9).

The effect of the presence of ferricyanide on the life time of triplet lumiflavin has been studied. The results suggest an energy transfer reaction without concurrent electron transfer reactions. The rate constant for the process was 2.8 times 109M‐1s‐1. The analogous reaction with ferrocyanide could not be observed because of the efficient electron transfer reaction (δG = ‐20.6 kcal mol‐1) leading to the formation of the semireduced lumiflavin and ferricyanide. The rate constant for this reaction was 3.3 times 109M‐1s‐1. The semireduced lumiflavin radical was found to disappear in a second order reaction with a rate constant of 1.7 times 109M‐1s‐1. It was found to react with ferricyanide with a rate constant of 0.7 times 109M‐1s‐1.

A model for the various photochemical and photophysical processes involved in the decay and quenching of the lumiflavin triplet state is suggested and discussed.
AGGREGATION OF CHLOROPHYLL a SPECIES ABSORBING NEAR 700nm–1. THE INFRARED CARBONYL BANDS
Authors: Chapados Camille
Published: January 2008

Abstract— Amorphous chlorophyll a obtained by electrodeposition(Chl–678) undergoes a bathoch‐romic shift upon solvation with gaseous alcohol at ambient temperatures. The process is reversible when the alcohol is removed. With 1‐propanol, the red band of Chi a is displaced from 678 nm to 701 nm and a new aggregate is formed,Chl–701. To determine the nature of the new aggregate, the IR carbonyl bands of Chi are monitored. The free ketone massive band ofChl–678, situated at 1691 cm‐1, is decreased upon solvation to the profit of the associated ketone carbonyl massive band which absorbs at 1656 cm‐1. The bandwidths of the massive bands are much greater than the typical value of a carbonyl band of a ketone in solution. This is an indication that the massive bands are composed of overlapping bands. In order to determine the number and the position of the bands, the Fourier self‐deconvolution technique has been used to enhance the spectral characteristics of the infrared spectra. The band fitting technique is then used on the original spectra to determine the difference in intensity between the bands ofChl–678 and those ofChl–701. The interpretation of the resolved IR spectra shows that the amorphous sample is composed of open dimers linked together by the CO‐Mg coordinate bonds. When the solvated species are formed, these coordinate bonds are not ruptured and one molecule of alcohol for two molecules of chlorophyll is linked to these molecules by an hydrogen bond between the hydrogen of the alcohol and the available ketone and by a coordinate bond between the available Mg and the oxygen of the alcohol. Closed dimers are thus formed.
LINEAR DICHROISM(250–700 nm) OF CHLOROPHYLL a AND PHEOPHYTIN a ORIENTED IN A LAMELLAR PHASE OF GLYCERYLMONOOCTANOATE/H2O. CHARACTERIZATION OF ELECTRONIC TRANSITIONS
Authors: Fragata M. , Nordén B. , Kurucsev T.
Published: January 2008

Abstract— We determined the polarized and isotropic visible/UV absorption spectra of chlorophyll a (Chi a) and pheophytin a (Pheo a) oriented in the lamellar phase of glycerylmonooctanoate/H2O. Resolution into mutually perpendicular X‐ and Y‐polarized absorption spectra of the pigments was achieved assuming that the transition moments of Chi a and Pheo a are located in the plane of the chromophores. The polarized spectra were deconvoluted into harmonic progressions and the resultant assignment of band positions in the long‐wavelength region was found to correlate well with independent spectral measurements, such as the polarisation of fluorescence. However, the correlation of the experimentally determined transitions with the results of theoretical calculations is not straightforward. The overall conclusions are of fundamental interest in the determination of orientations of the tetrapyrrole macrocycle in lipid lamellae and pigment‐protein structures of photosynthetic membranes.
SPECTROSCOPIC INVESTIGATION OF DIHYDRONICOTINAMIDES‐I: CONFORMATION, ABSORPTION, AND FLUORESCENCE
Authors: FISCHER PETER , FLECKENSTEIN JURGEN , HöNES JOACHIM
Published: January 2008

Abstract— The 1(N)‐(2,6‐dichlorobenzyl)‐1,4‐dihydronicotinamide (I), N‐methyl‐ and N,N‐dimethyl‐1(N)‐(2,6‐dichlorobenzyl)‐1,4‐dihydronicotinamide (II and III), respectively), and 1(N)‐(2,6‐dichloro‐benzyl)‐2‐aminomethyl‐1,4‐dihydronicotinic acid lactame (IV) were synthesized as model compounds for natural coenzymes, and systematically studied by 1H NMR, UV/V1S absorption and fluorescence spectroscopy. The absorption at ∼ 340 nm argues for an effective conjugation between dihydropyridine and carboxamide π‐system, and rules out any severely twisted conformation. For the natural coenzymes NADH and NMNH, as well as for I and II (with no or only one N‐amide substituent), 1H NMR definitively establishes a transoid conformation in solution, with the carbonyl O close to 2‐H of the dihydropyridine ring. N,N‐dimethyl substitution effectively inverts the carboxamide orientation into the cisoid form. The 1H NMR data (as well as molar extinctions) for the fused‐ring derivatives IV and V, with a fixed cisoid and transoid structure, respectively, provide final proof for the conformational assignment.

Absorption maxima are shifted to lower energies with increasing solvent polarity. In solvents which can act as hydrogen bond acceptors to the carboxamide N‐H, absorption shows a general blue‐shift of ∼ 10 nm. H‐bond donor solvents do not affect absorption maxima but enhance molar extinction. Fluorescence maxima show a similar dependence on solvent polarity but no specific hydrogen‐bonding effect. Fluorescence quantum yields appear increased tenfold in solvents donating H‐bonds to the carboxamide C=O group. These results are interpreted in terms of the vinylogous amide resonance between C=O function and ring‐N lone pair being the electronic interaction dominating in the ground state of dihydronicotinamides.
SOME PREVALENT BIOMOLECULES AS DEFENSES AGAINST SINGLET OXYGEN DAMAGE
Authors: Dahl Thomas A. , Midden W. Robert , Hartman Philip E.
Published: January 2008

Abstract— We have compared the relative abilities of some putative biological protectors to block oxidation of 2,5‐bis(hydroxymethyl)furan (BHMF)† in illuminated solutions containing the photosensitizer rose bengal and in the separated‐surface‐sensitizer (S‐S‐S) system involving pure singlet oxygen (1ΔAgO2). While L‐histidine is a well‐known quencher of singlet oxygen, free L‐histidine is not commonly found in high concentrations in nature. L‐Carnosine (β‐alanyl‐L‐histidine), however, is present in the striated muscles of many organisms, most notably mammals, in concentrations up to 40 mM. At neutral pH, carnosine quenched singlet oxygen more effectively than did equimolar histidine, both in solubilized sensitizer studies and in the S‐S‐S system. In the pure singlet oxygen system, 1 mM carnosine reduced the rate of BHMF oxidation as effectively as 3 mM histidine alone, or a mixture of 3 mM histidine and 3 mMβ‐alanine. The fungal product L‐ergothioneine (2‐thiol‐L.‐histidine betaine) and its synthetic analogue, 2‐thiolhistidine, at 1 mM blocked photosensitized BHMF oxidation using solubilized rose bengal, as did urate at 0.5 mM. All three compounds failed to reduce the rate of BHMF oxidation by singlet oxygen in the S‐S‐S system, however. Homocarnosine (‐γ‐aminobutyryl‐L‐histidine) gave levels of protection against BHMF oxidation identical to histidine, but is present in the central nervous system only at micromolar concentrations. Neither 1 mM imidazole nor 5 mM urea reduced BHMF oxidation in either system. We conclude that some prevalent biomolecules may afford protection either by preventing singlet oxygen production (urate, L‐ergothioneine) or by intercepting singlet oxygen once formed (L‐carnosine). Such protective devices may be of importance in natural systems.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES‐IX. PHOTOSENSITIZATION OFV–79 CHINESE HAMSTER CELLS ANDEMT–6 MOUSE MAMMARY TUMOR BY SELECTIVELY SULFONATED ZINC PHTHALOCYANINES
Authors: Brasseur Nicole , Ali Hasrat , Langlois Réjean , VAN Lier Johan E.
Published: January 2008

Abstract— Zinc phthalocyanines sulfonated to different degrees are tested for their ability to sensitizeV–79 Chinese hamster cells andEMT–6 mouse mammary tumors to red light. In vitro, the lower sulfonated derivatives were the most active with the exception of the poorly water‐soluble monosulfonated dye. An isomeric mixture of tetrasulfonated derivatives obtained via direct sulfonation was ten times more active than the homogeneous tetrasulfo derivative prepared via the condensation of sulfophthalic acid. In vivo, the latter dye was completely inactive, whereas the remainder of the sulfonated preparations exhibited a similar structure‐activity pattern as observed with theV–79 cells in vitro. The disulfonated zinc phthalocyanine showed the best tumoricidal activity in the series and also appeared to be a more efficient photosensitizer of cell inactivation and tumor cure than the aluminum or gallium complexes as well as hematoporphyrin derivative preparations. No significant differences in skin phototoxicity were observed among the various dyes.
FLUORESCENCE QUANTUM YIELDS AND LIFETIMES FOR BACTERIOCHLOROPHYLL c
Authors: Brune Daniel C. , Blankenship Robert E. , Seely Gilbert R.
Published: January 2008

Abstract— Absorption and emission spectra of bacteriochlorophyll c dissolved in a variety of solvents were measured and fluorescence quantum yields determined from the integrated emission spectra. Values for the emission maxima calculated from the positions and bandwidths of the red absorption band using the Stepanov relationship agreed closely with the experimental values. Fluorescence quantum yields varied between 0.10 in methanol and 0.36 in tetrahydrofuran and in dibutylamine. Fluorescence lifetimes were also determined for bacteriochlorophyll c in four of the solvents, and ranged from 2.7 ns in methanol to 7.6 ns in dimethylsulfoxide.
COOPERATION OF QUERCETIN WITH ASCORBATE IN THE PROTECTION OF PHOTOSENSITIZED LYSIS OF HUMAN ERYTHROCYTES IN THE PRESENCE OF HEMATOPORPHYRIN
Authors: Sorata Yasuhiro , Takahama Umeo , Kimura Mitsutaka
Published: January 2008

Abstract— Quercetin(20–100 μM) suppressed photohemolysis sensitized by hematoporphyrin, while ascorbate(10–100 μM) stimulated it. However, in the presence of 40 μM quercetin, ascorbate promoted the suppression. The suppression by quercetin was due to scavenging of both singlet oxygen generated by a photosensitized reaction and radicals generated by decomposition of lipid peroxides formed by a singlet oxygen‐dependent reaction. In scavenging, quercetin was oxidized and the oxidation was suppressed by ascorbate. Ascorbate was oxidized by illumination in the presence of quercetin. It is suggested that the cooperation of quercetin with ascorbate in photohemolysis is due to reduction of oxidized quercetin by ascorbate regenerating the flavonol.
A ROLE FOR MENADIONE IN THE PURPLE MEMBRANE PROTON PUMP?
Authors: Renthal Robert , Hollub Alexander
Published: January 2008

Abstract— It has been assumed that proton pumps such as purple membrane lack redox loops. However, purple membrane does contain an electron carrier. Kates et al. (Meth. Enzymol. 88,98–1 111, 1982) reported the presence of 1 mole of vitaminMK–8 to 6 mol of bacteriorhodopsin among the nonpolar lipids. Is this quinone functionally important in the proton pump mechanism?

Proton pumping rates were measured with lipid‐free bacteriorhodopsin reconstituted in vesicles to which varying amounts of vitamin K1 were added. With soybean lipids, in the presence of tetraphenyl boron, the pump quantum yield was 0.04H+/photon. This result was independent of the amount of vitamin K, added over a range of 0 to a 100‐fold mole ratio to bacteriorhodopsin. A similar result was obtained with H. halobium lipids. The pump quantum yield in vesicles is much less than reported for membrane sheets and whole cells. The results support the conclusion that a vitamin K Q‐cycle is not involved in the purple membrane proton pump.
IN VITRO AND IN VIVO PROTECTION AGAINST PHOTOTOXIC SIDE EFFECTS OF PHOTODYNAMIC THERAPY BY RADIOPROTECTIVE AGENTSWR–2721 ANDWR–77913
Authors: Dillon James , Kennedy James C. , Pottier Roy H. , Roberts Joan E.
Published: January 2008

Abstract— The experimental radioprotective agentsS–2‐(3‐aminopropylamino) ethyl phosphorothioate(WR–2721) and 3‐amino‐2‐hydroxypropyl phosphorothioate(WR–77913) are also protective against photosensitized oxidation. They reduce porphyrin‐induced photopolymerization of lens cytosol proteins in vitro, and phototoxic damage to mouse skin in vivo. The phototoxic dose modification factor (DMF) was 1.5 which is similar to that found in ionizing radiation. Part of the mechanism by which sulfhydryls afford this protection is by accelerating photobleaching of the porphyrins.
8‐METHOXYPSORALEN‐PHOTOINDUCED DNA CROSSLINKS AS DETERMINED IN YEAST BY ALKALINE STEP ELUTION UNDER DIFFERENT REIRRADIATION CONDITIONS. RELATION WITH GENETIC EFFECTS
Authors: Cundari E. , Averbeck D.
Published: January 2008

Abstract—DNA damage induced by 8‐methoxypsoralen (8‐MOP) plus near UV light (UVA) was analyzed in diploid yeast using the alkaline step elution technique. The presence of 8‐MOP and UVA induced DNA interstrand cross‐links was revealed by the increase of DNA retained on elution filters as compared to untreated controls. The fraction of DNA retained on filters increased linearly with UVA dose. The amount of cross‐links was estimated from the fraction of DNA retained on filters using a dose of m̀‐radiation leading to a number of DNA strand breaks at least equivalent to the number of 8‐MOP induced photoadducts.

When 8‐MOP treated cells were exposed to monochromatic light, 365 nm light induced monoadducts and cross‐links whereas 405 nm light induced only monoadducts. When submitting 8‐MOP plus 405 nm light treated cells to 365 nm irradiation, after removal of unbound 8‐MOP by washing, a portion of 8‐MOP plus 405 nm light induced monoadducts was converted into cross‐links. The amount of monoadducts transformed into cross‐links was dependent on the dose of 365 nm irradiation up to a maximum likely to correspond to the number of suitably positioned furan‐side monoadducts that could be converted into biadducts. When 8‐MOP plus 365 nm light treated cells were reirradiated with 365 nm light, following the same protocol, the maximum level of cross‐linking obtainable in yeast was lower than that obtained with 8‐MOP in a 405 nm plus 365 nm reirradiation protocol.

In the presence of 8‐MOP single exposures to 405 nm light were found to be only slightly genotoxic. However, when followed by second exposures to 365 nm light, a dose‐dependent increase in genetic effects, i.e. mutation and gene conversion, was observed in parallel to the induction of DNA crosslinks. These results stress again the prominent role of DNA cross‐links in the genotoxicity of 8‐MOP.
PRODUCTS AND RELATIVE REACTION RATES OF THE OXIDATION OF TOCOPHEROLS WITH SINGLET MOLECULAR OXYGEN
Authors: NEELY W. C. , MARTIN J. M. , BARKER S. A.
Published: January 2008

Abstract— The relative reactivity of singlet molecular oxygen, 02(1Δg), α‐,β‐,Γ‐and δ with ‐tocopherol (vitamin E) was investigated using microwave discharge generation as a uniquely clean source of singlet oxygen and using a hydrocarbon solvent to approximate the membrane environment. The relative efficiencies of the tocopherols for O2(1Δg) were found to decrease in the order: D‐α‐tocopherol > D‐β‐tocopheroI > D–Γ‐tocopherol > D‐δ‐tocopherol. The reaction products in all cases were found to be mixtures of quinone and quinone epoxides apparently resulting from decomposition of the primary product, the hydroperoxydienone.
PHOTOPHYSICAL BEHAVIOUR OF 5‐METHOXYPSORALEN IN DIOXANE‐WATER MIXTURES
Authors: Melo T. Sae , Maqanita A. , Prieto M. , Bazin M. , Ronfard‐Haret J. C. , Santus R.
Published: January 2008

Abstract—Triplet‐triplet absorption spectra, intersystem crossing quantum yields, fluorescence lifetimes, and fluorescence quantum yields of 5‐methoxypsoralen (5MOP) in dioxane‐water mixtures are reported. The fluorescence and triplet formation quantum yields depend strongly on the water content in the mixtures, increasing up to maximum values which are, respectively, twentyfold and fivefold larger than in dioxane and then decreasing. This behaviour is essentially due to the variation of the internal conversion rate constant. With these solvent mixtures it is possible to emulate the dielectric response of 5MOP photophysical parameters in other media, such as in biological model systems and in human blood lipoproteins. The biological importance of these results is discussed.
SOLAR SPECTRAL IRRADIANCE IN THE VISIBLE AND INFRARED REGIONS
Authors: Green Alex E. S. , Chai Shun‐Tie
Published: January 2008

Abstract— The analytical formulas previously developed for estimating the spectral irradiance reaching the ground in the ultraviolet are extended into the visible and infrared(350–3000 nm). This approach has two distinct features: (1) all physical inputs for calculating the direct irradiance are given in analytical form, and (2) the diffuse spectral irradiance (skylight) is calculated using dimensionless ratios which relate it to the direct irradiance. In common with other approaches, the global spectral irradiance for arbitrary ground reflectivity is calculated from the sum of the direct and diffuse spectral irradiances and a divisor which depends upon the ground and air spectral reflectivities. The global spectral irradiance on a tilted surface may also be calculated in terms of the above quantities and two angles. As in the case of the ultraviolet, the formulas presented are intended for photobiological applications.
PHOTOCHEMISTRY OF METHYLATED RHODOPSINS
Authors: Govindjee Rajni , Dancshazy Zsolt , Ebrey Thomas G. , Longstaff Colin , Rando Robert R.
Published: January 2008

Abstract—Rhodopsin, in which the active‐site Schiff‐base lysine has been chemically modified by monomethylation, is unable to form the deprotonated Schiff base bleaching intermediate, rnetarhodop‐sin II. The photochemistry of the methylated Schiff base rhodopsin stops at the metarhodopsin I stage, which then slowly decays to all‐trans retinal and opsin. Methylation of the non active‐site lysines does not block the photochemical transformation but does speed up the formation and decay of the metarhodopsins.
PHOTOEXCITATION OF RHODOPSIN: CONFORMATION CHANGES IN THE CHROMOPHORE, PROTEIN AND ASSOCIATED LIPIDS AS DETERMINED BY FTIR DIFFERENCE SPECTROSCOPY
Authors: DeGrip Willem J. , Gray Daniel , Gillespie John , Bovee Petra H. M. , Berg Ellen M. M. Van Den , Lugtenburg Johan , Rothschild Kenneth J.
Published: January 2008

Abstract—The visual pigment rhodopsin is the major membrane protein in the rod photoreceptor membrane. Rhodopsin's function is to transduce the light induced isomerization (ll‐cis toall‐trans)of its internally located retinylidene chromophore into transient expression of signal sites at the surface of the protein. Fourier transform infrared (FTIR) difference spectroscopy has been used to study all of the steps in the photobleaching sequence of rhodopsin. Early protein alterations involving the peptide backbone and aspartic and/or glutamic carboxyl groups were detected which increase upon lumirhodopsin formation and spread to water exposed carboxyl groups by metarhodopsin II. The intensified and frequency shifted hydrogen‐out‐of‐plane vibrations of the chromophore that are present in bathorhodopsin are absent in lumirhodopsin. This indicates that by lumirhodopsin, the chromophore has relaxed relative to its more strained all‐frans form in bathorhodopsin. Finally, the transition to metarhodopsin II is found to involve perturbation of the acyl tail region of unsaturated phospholipid molecules possibly in response to small changes in the shape of the rhodopsin.
COMPARISON OF PHOTODYNAMIC ACTION BY ROSE BENGAL IN GRAM‐POSITIVE AND GRAM‐NEGATIVE BACTERIA
Authors: Dahl ThomasA. , Midden W. Robert , Neckers D. C.
Published: January 2008

Abstract— The photodynamic inactivation by illuminated Rose Bengal of a number of bacterial species was compared. The gram‐positive species, Bacillus subtilis, Staphylococcus aureus, Streptococcus faecalis and Streptococcus salivarius, were inactivated about 200x more quickly (99% inactivation) than a Salmonella typhimurium wildtype strain. The Salmonella inactivation curve exhibited an initial lag time during which bacteria were not significantly inactivated. The lag time for inactivation of a derivative of the wildtype Salmonella strain that is deficient in a large portion of its cell wall lipopolysaccharide coat was approximately half of the lag time for the wildtype strain but the subsequent rate of inactivation was approximately the same for the two strains. Dark preincubation of both Salmonella strains with Rose Bengal before illumination shortened the lag time, but did not increase the final rate of inactivation. Dark preincubation prior to illumination did not measurably change the inactivation curve of the gram‐positive species. The lag time observed in the inactivation curves for Salmonella bacteria may reflect the time required for penetration of the Rose Bengal anion through the outer portion of the gram‐negative cell wall to a critical location within the cell for effective photosensitization.
ACTION SPECTRA FOR SUPEROXIDE GENERATION AND UV AND VISIBLE LIGHT PHOTOAVOIDANCE IN PLASMODIA OF Physarum polycephalum
Authors: Ueda Tetsuo , Mori Yoshihito , Nakagaki Toshiyuki , Kobatake Yonosuke
Published: January 2008

Abstract— The initial photochemical process leading to photoavoidance by plasmodia of an albino strain of Physarum Plasmodium was studied. Superoxide (O), detected as superoxide dismutase (SOD)‐inhibitable electron spin resonance (ESR) signal of a spin trap (tBN), was formed upon irradiation. The amount of O formed increased linearl) with log fluence rate above the threshold. The photoavoidance to radiation at wavelengths between200–800 nm also showed the similar linear relationship in log fluence rate‐response curves. Thresholds for photoavoidance and O generation agreed with each other and the action spectra showed peaks at about 260, 370, and 460 nm. Thus, active oxygen generated by photosensitization seems to trigger the UV and blue light photoavoidance.
PHOTOFRAGMENTATION OF PHOTOTOXIC DIBENZOCYCLOHEPTADIENE ANTIDEPRESSANTS
Authors: Epling Gary A. , Sibley Michele T. , Chou Thomas T. , Kumar Anil
Published: January 2008

Abstract— Abstract‐The products of photochemical reaction of a family of phototoxic tricyclic antidepressants have been determined, both in the presence and absence of oxygen. Under all conditions photofrag‐mentation of the phototoxic compounds is an important reaction‐in some cases it is virtually the only photoreaction observed. The mechanism of photoreaction appears to involve excited state electron transfer from the side chain to give a reactive exciplex, which fragments via both radical and ionic pathways. These reactive intermediates are likely to contribute to the in vivo phototoxicity of these compounds.
TEMPERATURE AND MYCOCHROME SYSTEM IN NEAR‐UV LIGHT INDUCIBLE AND BLUE LIGHT REVERSIBLE PHOTOINDUCTION OF CONIDIATION IN Alternaria tomato*
Authors: Kumagai Tadashi
Published: January 2008

Abstract— When dark‐grown colonies were exposed to near‐UV light, conidiophore formation was induced, and conidia developed during a subsequent dark period. Simultaneous exposure to near‐UV and blue light inhibited induction of conidiation. The inductive effect of near‐UV light irradiation was greatly enhanced by treating colonies with low temperatures for 4 h during the 2nd‐6th hour of incubation in the dark following inductive irradiation: the enhancement was greatest at 21°C. The extent of inhibition by blue light increased with the temperature between 10 and 28°C. This diminution by low temperature was greatest when colonies previously kept at a low temperature were exposed to inductive irradiation: the longer the duration between inductive irradiation and temperature treatment, the lower the diminution. Higher fluences of blue light were required to suppress conidial induction at lower temperature.

Thus, it is evident that the inductive effect of near‐UV light irradiation on conidiation and the suppressive effect of blue light irradiation are each responsive to different temperatures applied at different times.
MECHANISM OF PHOTOSENSITIZATION BY PHEOPHORBIDE a STUDIED BY PHOTOHEMOLYSIS OF ERYTHROCYTES AND ELECTRON spIN RESONANCE SPECTROSCOPY
Authors: KUWABARA M. , YAMAMOTO T. , INANAM O. , SATO F.
Published: January 2008

Abstract Phcophorbide a (PPa), a causal substance of food intoxication, when excited by exposure to light wavelengths of over 600 nm, caused the photohemolysis of goat erythrocytes in proportion to the incubation time of the cells. The addition of N‐3, an effective scavenger of 1O2, to the medium markedly inhibited the hemolysis of erythrocytes in a concentration‐dependent manner, whereas the addition of superoxide dismutase (SOD) and catalase, inhibitors of O‐2 and H2O2 generation, respectively, to the medium had little effect on it.

Methods for converting 1O2 to a nitroxide radical by 2,2,6,6‐tetramethyl‐4‐piperidone (TMPD) and for trapping O‐2 and OH by 5,5‐dimethyl‐l‐pyrroline‐A'‐oxide (DMPO) were employed to observe directly these activated oxygens by electron spin resonance (ESR). The methods provided evidence that only 1O2, was produced by PPa, which was excited by light wavelengths of over 600 nm. Both the addition of N3 to the solution and the removal of oxygen from the solution inhibited the generation of 1O2.

These results led us to conclude that 1O2 was mainly responsible for the hemolysis of erythrocytes by photoexcited PPa.
GLUCOSE ADMINISTRATION AUGMENTS IN VIVO UPTAKE AND PHOTOTOXICITY OF THE TUMOR‐LOCALIZING FRACTION OF HEMATOPORPHYRIN DERIVATIVE
Authors: Thomas James P. , Girotti Albert W.
Published: January 2008

Abstract Rhabdomyosarcoma tumors in rats made hyperglycemic by multiple injections of glucose exhibited a transient decrease in pH and an increased ability to accumulate derivatives of hemato‐porphyrin (HPD). Photoradiation of tumors in glucose/HPD‐treated animals produced a greater cell kill than in galactose/HPD‐treated controls. A therapeutic benefit of glucose administration in conjunction with HPD‐phototherapy is suggested.
THE EFFECT OF A CHALCOGENAPYRYLIUM DYE WITH AND WITHOUT PHOTOLYSIS ON MITOCHONDRIAL FUNCTION IN NORMAL AND TUMOR CELLS
Authors: WALSTAD DIANA L. , BROWN J. TONY , POWERS STEPHEN K.
Published: January 2008

Abstract A chalcogenapyrylium dye 8b, which is under investigation for the photodynamic therapy of malignant gliomas (brain tumors), was evaluated for inhibition of mitochondrial function both before and after exposure to laser light of 800 nm. Neoplastic and normal cells forced to use mitochondrial substrates were killed by the light‐activation of intracellular 8b as well as exposure to classic mitochondrial inhibitors, rotenone and sodium azide. Correspondingly, cells in glucose‐rich media showed little decrease in viability due to the photolysis of intracellular 8b or the presence of mitochondrial toxins. The toxicity of 8b without light activation was found to be the same regardless of the cell's energy source. Measurement of cellular ATP generated during treatment also showed the photolysis of intracellular 8b to be more inhibitory towards mitochondrial function than the unactivated parent compound. We conclude that the chalcogenapyrylium dyes localize to the mitochondrion and that photoactivation results in mitochondrial injury.
PHOTOSENSITIZATION OF SINGLE‐STRAND BREAKS IN pBR322 DNA BY ROSE BENGAL
Authors: CIULLA THOMAS A. , VAN CAMP JOHN R. , ROSENFELD EVAN , KOCHEVAR IRENE E.
Published: January 2008

Abstract Rose bengal photosensitized the formation of frank single‐strand breaks (SSBs) in double‐stranded, supercoiled pBR322 DNA as measured by neutral agarose electrophoresis. The yield of SSBs followed first order kinetics with respect to light fluence and dye concentration. The efficiency of cleavage was more than 20 times greater in an argon atmosphere than in an oxygen atmosphere. The quantum yield in an air atmosphere was 1.7 (± 0.3) × 10‐8. Sodium azide quenched the cleavage more efficiently in an oxygen atmosphere than when the oxygen concentration was reduced. Isopropanol and mannitol were poor quenchers; ribose‐5‐phosphate and guanosine‐5'‐monophosphate did not quench the cleavage. Substituting D2O for H2O increased the yield of SSBs in both oxygen and oxygen‐depleted atmospheres. The results are consistent with initiation of cleavage by reaction of the triplet state of rose bengal (or a radical derived from it) with DNA. In the presence of oxygen, an additional mechanism is introduced.
α‐OXIDASE ACTIVITY IN PLANTS AS PROMOTOR OF ELECTRONIC ENERGY
Authors: CAMPA ANA , SALIM‐HANNA MARTA , CILENTO GIUSEPPE
Published: January 2008

Abstract The a‐oxidase activity of higher plants acting on long chain fatty acids generates the lower aldehyde in the ground state; however if chlorophyll or chioroplasts are present the chlorophylls are excited most likely by a chemically initiated electron exchange (CIEEL) luminescence process with the putative a‐peroxylactone intermediate. When the aldehyde is substituted for the acid, the lower aldehyde appears in the triplet state. The chiral discrimination observed in the quenching by D‐ and L‐tryptophan of the chlorophyll sensitized emission indicates that the triplet aldehyde is generated within the enzymatic preparation and transfers energy while still bound to the enzyme.

Chlorophylls in chioroplasts are excited by addition of a long chain fatty acid or aldehyde. The mechanism, however, is unknown.
PICOSECOND FLUORESCENCE OF R3230AC MAMMARY CARCINOMA MITOCHONDRIA AFTER TREATMENT WITH HEMATOPORPHYRIN DERIVATIVE and PHOTOFRIN®II in vivo
Authors: Hanzlik Cheryl A. , Knox Robert S. , Gibson Scott L. , Hilf Russell
Published: January 2008

Abstract—

Hematoporphyrin derivative(HPD) and other porphyrin samples were excited by 20‐ps 532‐nm laser pulses. Fluorescence was detected using a low‐jitter streak camera. Data were fitted to a sum of exponential decay times on the order of picoseconds. Fluorescence of porphyrins in aqueous solution show various behaviors depending on the hydrophobicity of the porphyrins. The most hydrophilic porphyrins show long decays only(500 ps). Porphyrins intermediate in hydrophobicity have intensity‐dependent fast decays. The most hydrophobic have fast decays (< 20 ps). Picosecond fluorescences of mitochondria prepared from rat tumors treatedin vivowith HPD or Photofrin II show an increase in the ratio of fast to slow decays when compared to the injected porphyrins. These results are consistent with the concentration of the more hydrophobic porphyrins in mitochondria in photosensitization treatment. Thus picosecond fluorescence studies of porphyrins may provide a means to obtain photoproperties which differentiate between effective and ineffectivein vivophotosensitizers.
FLUENCE‐RESPONSE RELATIONSHIP FOR PHOTOGENE EXPRESSION IN ETIOLATED PEA SEEDLINGS†
Authors: Yoshida Kazuichi , Takimoto Atsushi , Sasaki Yukiko
Published: January 2008

Abstract—

Fluence‐response relationships in transcript accumulation were investigated at various wavelengths for the following photogenes: the nuclear‐encoded small subunit gene of ribulose bisphosphate carboxylase/oxygenase (rbcS), the nuclear‐encoded chlorophyll alb‐binding protein gene (Cab), the chloroplast‐encoded large subunit gene of ribulose bisphosphate carboxylase/oxygenase (rbch) and the chloroplast‐encoded photosystem I A2 subunit gene (psaB). The fluence‐response curves for all genes obtained at all wavelengths showed a biphasic character suggesting the involvement of both very low fluence response and low fluence response mediated by phytochrome. The proportion responding in the very low fluence range differed with the gene, and was largest for rbcL followed by psaB, Cab and rbcS in this order.