bluuebunny/crossref_metadata_2025_split huggingface dataset:
DISTORTION OF ACTION SPECTRA IN PHOTOMORPHOGENESIS BY LIGHT GRADIENTS WITHIN THE PLANT TISSUE
Authors: Kazarinova‐Fukshansky Nina , Seyfried Max , Schäfer Eberhard 
Published: January 2008

Abstract—Recently a method for measuring optical properties of light scattering and absorbing tissues was discussed (Seyfried et al., 1983). Based on measurements of transmittance and reflectance of cotyledons of dark‐ and light‐grown Cucurbita pepo L, seedlings a method to compute and correct apparent photoconversion cross sections for various distributions of a sensory pigment is described. The distortion function may be used to calculate expected apparent (distorted) action spectra for a pigment in vivo when the spectral properties of the pigment in vitro are known. With phytochrome as an example for a sensory pigment of low concentration within the tissue it is shown that the low apparent photoconversion cross section in blue light observed in etiolated seedlings can be explained solely by optical distortions caused by light gradients. In green tissue on the other hand the ratio of the apparent photo conversion cross sections in red and blue light is almost identical with that observed in vitro, but the ratio in red and far‐red light depends strongly on the distribution of the relevant sensory pigment. An analysis of the rate of phytochrome cycling shows an additional peak in the far‐red if the pigment is localized in the lower part of the tissue only.
EXTENDING CIRCULAR DICHROISM SPECTRA INTO THE VACUUM UV AND ITS APPLICATION TO PROTEINS
Authors: Johnson W. Curtis 
Published: January 2008

AbstractCircular dichroism (CD) spectra measured into the vacuum UV region provide information necessary for this technique to fulfill its potential. In the case of proteins, CD spectra measured to 184 nm or below can be analyzed for secondary structure: generalized inverses make such analyses particularly simple. Generalized inverses for α‐helix, anti‐parallel β‐sheet, parallel β‐sheet, β‐turn, and “other” structures are given in tabular form. When the dot product of each inverse is taken with the digitized spectrum of a protein, the amount of corresponding secondary structure is predicted. However, protein CD spectra truncated above 184 nm give too little information to give reliable analyses. Furthermore, adding constraints only complicates this problem because unreliable analyses now appear good.
ON THE PRIMARY PHOTOPROCESS OF 124‐kdalton PHYTOCHROME
Authors: Eilfeld Peter , Eilfeld Petra , Rüdiger Wolfhart 
Published: January 2008

AbstractThe photoreaction between Pτ and the first detectable intermediate, lumi‐R, of 124‐kdalton oat phytochrome has been investigated at low temperatures. The temperature dependence of the quantum yields of the photoreactions, Pτ to lumi‐R and lumi‐R to Pτ, has been determined. From measurements over a temperature range from 119 to 155 K, an activation barrier of 3.6 ± 0.5 kJ mol 1 is found for the photoreaction of Pτ with 661‐nm actinic light. A higher value (5.7 ± 0.7 kJ mol ‐1) is found for the photoreaction of lumi‐R to Pτ. with 698‐nm actinic light. Increased quantum yields are found in deuterated buffer solutions at low temperatures. The activation energies for deuterated phytochrome (3.2 ± 0.7 kJ mol–1 for Pτ with 661‐nm irradiation and 6.2 ± 1.2 kJ mol‐1 for lumi‐R at 698‐nm irradiation) are identical within the limits of error with those of protonated phytochrome. The lack of a deuterium effect for the activation energies favors the Z,E‐isomerization rather than proton transfer or tautomerization for the chromophore photochemistry during Pτ⇄lumi‐R conversion.
THE MEASUREMENT OF DIHEMATOPORPHYRIN ETHER CONCENTRATION IN TISSUE BY REFLECTANCE SPECTROPHOTOMETRY
Authors: Patterson M. S. , Wilson B. C. , Feather J. W. , Burns D. M. , Pushka W. 
Published: January 2008

AbstractThe in vivo quantitation of local photosensitizer concentration is an important problem in photodynamic therapy because tumor response depends on this parameter. This paper describes a new method for measuring dihematoporphyrin ether (DHE) concentration by reflectance spectrophotometry—a technique which could be applied to other photosensitizers. The absorbance due to the 630 nm absorption peak of DHE was determined by obtaining diffuse reflectance spectra before and after the addition of DHE in the form of Photofrin II. Spectra were obtained by placing an optical fiber bundle source and single fiber detectors in contact with the tissue surface. The sensitivity of the technique was measured for three tissues in vitro with a range of optical properties as well as for Nutralipid—a liquid with a very high scattering to absorption ratio. The results were in qualitative agreement with the predictions of a diffusion model of light propagation although a systematic discrepancy was observed. The technique was also successfully demonstrated in vivo for VX‐2 carcinomas implanted in rabbit ears by correlating simultaneous absorbance measurements with gamma counting of radiolabeled 6‐4Cu Photofrin II. Our results suggest that reflectance spectrophotometry may be a useful clinical and research tool for the in vivo quantitation of DHE and other photosensitizers.
DIFFERENT PHOTOINACTIVATION MECHANISMS IN Propionibacterium acnes FOR NEAR‐ULTRAVIOLET and VISIBLE LIGHT
Authors: Kjeldstad Berit 
Published: January 2008

The light sensitivity of Propionibacterium acnes was investigated when the cells were exposed to anoxia, sodium azide, D2O or superoxide dismutase in combination with visible light (broad band red light and 415 nm) and near‐ultraviolet irradiation (360 and 320 nm). During anoxia the cells became less sensitive when the irradiation wavelength increased. Oxygen increased the photodamage to a greater extent in the case of visible light than of near‐UV light. The photosensitization effects were, however, more or less oxygen dependent at all wavelengths used. An effect of azide and D2O on the light sensitivity was observed for visible light, while superoxide dismutase was effective only at 320 nm.The results support the hypothesis that inactivation of P. acnes with near‐UV and visible light is based on different mechanisms. Porphyrin photosensitization, accomplished by singlet oxygen, is the most important mechanism when visible light is used. At shorter wavelengths (320 and 360 nm) singlet oxygen is not involved and for 320 nm the destruction might occur via superoxide anion formation.
IMPROVING THE EFFICIENCY OF HEMATOPORPHYRIN PHOTOTHERAPY OF OCULAR TUMORS
Authors: Lutty GerardA. , Fortune Myrmuth , Hochheimer BernardF. 
Published: January 2008

Malignant melanoma of the choroid is the most common primary intraocular tumor in adult humans. Controversy exists over which is the most effective therapy. One therapeutic modality that has not been thoroughly investigated is hematoporphyrin derivative phototherapy (HPdPRT), a technique used successfully in the clinic on many non‐ocular tumors.The effect of HPd PRT on an ocular, amelanotic melanoma was evaluated using Greene melanoma implanted on pigmented rabbit iris. The parameters used clinically on non‐ocular tumors (intravenous 2.5 mg HPd kg‐1 body weight and irradiation at 633 nm 48 h later) were totally ineffective in killing Greene melanoma implanted on the iris. The dose of dye (2.5–5 mg kg‐1), wavelength of light (500‐700 nm), and illumination intensity were varied to determine the most efficient parameters for treating this tumor. The most important parameter was dye dose; increasing it to 5 mg kg‐1 resulted in some control of tumor growth. Administering 100% O2 prior to and during irradiation also improved HPd PRT cytotoxicity. The use of pulsed light (pulses of 1 or 2 min) further enhanced killing and reduced the length of irradiation needed. These studies suggested that HPd PRT might be used efficiently on ocular melanomas.
THE PHOTOCHEMISTRY OF SPECIFIC TRYPTOPHAN RESIDUES IN PROTEINS AS ANALYZED BY THE FLUORESCENT SCANNING OF TRYPTIC PEPTIDE MAPS
Authors: Dillon James , Chiesa Raúl , Spector Abraham 
Published: January 2008

Abstract— The fact that most proteins contain several tryptophans hinders the investigation of the photochemistry of a particular indole residue. A method is presented here that can be used to investigate the photochemistry of specific tryptophan residues in proteins. It consists simply of separating the peptides of a proteolytically digested protein by TLC and then scanning the peptides at the fluorescent maximum of tryptophan. The assignment of the resultant peaks to a particular peptide is based on the chromatographic comparison of the scans with peptide maps.Using this method, the photochemistry of the tryptophan residues in alpha crystallin, a major protein of lenses, was investigated. Under photolytic conditions that mimic the transmission characteristics of the cornea (>293 nm), it was found that there is a differential photolysis of the tryptophan residues in the protein; with Trp‐9 in the N‐terminal peptide photolyzing at a considerably faster rate than Trp‐60. In addition to tryptophan, photolytic losses of tyrosine were assessed by scanning the peptide maps at the tyrosine fluorescent maximum. Only one tyrosine residue photolyzes under these conditions. The differential photolysis of the tryptophan residues is explained in part by the presence of residues in the vicinity of the indole moieties.
PHOTOBINDING OF CHLORPROMAZINE AND ITS SULFOXIDE IN VITRO AND IN VIVO
Authors: Schoonderwoerd S. A. , van Henegouwen G. M. J. Beijersbergen , Luijendijk J. J. 
Published: January 2008

Abstract— Photosensitivity as observed after chlorpromazine (CPZ) treatment is enhanced in the UVA‐ rather than the UVB region, whereas CPZ has its absorption maximum at 305 nm. This long wavelength sensitivity has sometimes been ascribed to CPZ‐sulfoxide (CPZSO) which has an absorption maximum at 340 nm. We compared the photobinding properties of CPZSO and CPZ under both in vitro and in vivo conditions.With 310 and 370 nm lamps CPZSO absorbs twice as much light as CPZ but still binds less efficiently to HSA in vitro. At wavelengths longer than 380 nm CPZSO does not absorb nor photobind to HSA (420 nm lamps) in contrast to CPZ. In vivo the bioavailability of CPZ and CPZSO in ears, eyes and skin of the back of Wistar rats is comparable, yet irradiation with 370 nm light caused more CPZ‐photobinding in these tissues. Chlorpromazine binds relatively more compared to CPZSO, to constituents of deeper lying tissues (dermis). This corresponds with the observation that both the ratio of in vitro CPZ photobinding to CPZSO photobinding, and the penetrating ability of light in the skin increase with wavelength.In the eyes, where the lens efficiently filters out light with wavelengths shorter than 370 nm, no CPZSO photobinding was observed, in contrast to CPZ; this also corresponds with the in vitro experiments. Therefore it seems more likely that the observed wavelength maximum in the photosensitivity action spectrum after CPZ treatment should be attributed to the non‐sulfoxidated drug rather than to the sulfoxidated compound.
PHOTO‐CIDNP EVIDENCE FOR CHARGE‐TRANSFER INTERACTION BETWEEN SYNTHETIC WATER‐SOLUBLE PORPHYRINS AND GUANINE*
Authors: NouËN D. LE , MARKO J. , VERMEERSCH G. , FEBVAY‐GAROT N. , LABLACHE‐COMBIER A. , PERREE‐FAUVET M. , GAUDEMER A. 
Published: January 2008

Abstract Photoreactions of aqueous solutions of synthetic water‐soluble porphyrins were studied by the 1H and 13C CIDNP technique. Strong polarizations, which were very sensitive to the presence of added acid, were observed on the cationic porphyrins (TMePyPH2‐TAPPH2) when irradiated through continuous UV‐visible light. They resulted from the reverse electron transfer between the semi‐oxidized and the semi‐reduced species of the derivative.When the experiments were carried out in the presence of nucleobases, guanine (and its derivatives) was the only residue that was polarized. This is thoroughly interpreted in terms of a reversible electron transfer reaction leading to guanine photooxidation by the porphyrin excited triplet state. It was shown to be drastically pH‐dependent and was correlated to the redox potential of the porphyrin. It was not affected by the incident wavelength. The reaction proceeded through the intermediate formation of the correlated radical‐ion pair: porphyrin radical anion‐guanine radical cation. This study suggested that a Type I (free radical) reaction could be one of the primary processes in DNA photosensitization by porphyrins.
SELECTIVE DEGRADATION OF AMINO ACIDS PHOTOSENSITIZED BY TRYPTOPHAN IN POLYPEPTIDE STRUCTURES
Authors: Pigault Claire , Gerard Dominique 
Published: January 2008

Abstract—Polypeptides containing a basic amino acid close to their single tryptophan residue were irradiated with monochromatic 302 nm radiation. Tryptophan photolysis was monitored by absorption and fluorescence spectroscopy. Amino acid loss was evaluated by amino acid analysis. Only the protonated residues adjacent to tryptophan in the sequence were destroyed upon tryptophan excitation. This reaction is probably due essentially to direct interaction between the excited tryptophan and the neighbouring residue without electron solvation.
PHOTO‐INDUCED ELECTRON EJECTION FROM THE REDUCED COPPER OF Pseudomonas aeruginosa AZURIN
Authors: Corin Alan F. , Gould Ian R. 
Published: January 2008

Abstract—The reduced form of Pseudomonas aeruginosa azurin exhibits an enhanced absorbance in the UV compared to that of the oxidized protein. This enhancement has also been observed for azurins from other bacterial species and for another type I copper protein, plastocyanin. Pulsed laser excitation of the reduced azurin in the region of enhanced absorbance at 308 nm results in single photon, rapid (<30 ns) oxidation of the copper center and formation of the hydrated electron with a quantum yield of 0.05. The hydrated electron reacts in the expected manner with scavengers such as nitrous oxide, oxygen, acetone and nitromethane. In the absence of scavengers, the electron reacts with the protein, including the disulfide bond, to form the disulfide radical anion, observed at 410 nm. The overall photophysical event involves a charge‐transfer to solvent transition although the existence of intermediate states can not be excluded.
SOLAR ULTRAVIOLET RADIATION AT THE EARTH'S SURFACE
Authors: Frederick J. E. , Snell H. E. , Haywood E. K. 
Published: January 2008

AbstractThe biologically effective ultraviolet irradiance at the earth's surface varies with the elevation of the sun, the atmospheric ozone amount, and with the abundance of scatterers and absorbers of natural and anthropogenic origin. Taken alone, the reported decrease in column ozone over the Northern Hemisphere between 1969 and 1986 implies an increase in erythemal irradiance at the ground of four percent or less during summer. However, an increase in tropospheric absorption, arising from polluting gases or particulates over localized areas, could more than offset the predicted enhancement in radiation. Any such extra absorption is likely to be highly regional in nature and does not imply that a decrease in erythemal radiation has occurred on a global basis. The Antarctic ‘ozone hole’ represents a special case in which a portion of the earth has experienced ultraviolet radiation levels during spring that are far in excess of those which prevailed prior to the present decade.
RADICAL PROCESSES IN LIPIDS. SELECTIVITY OF HYDROGEN ABSTRACTION FROM LIPIDS BY BENZOPHENONE TRIPLET
Authors: MARKOVIC D. Z. , PATTERSON L. K. 
Published: January 2008

AbstractLaser photolysis techniques have been used to measure the reactivity of benzophenone triplet (BZP) toward various fatty acids and two glycerides in benzene solution. Eight compounds varying both in number and in the configuration of olefinic bonds have been examined. It has been found that the rate constant for hydrogen abstraction from these compounds by 3BZP may be related to the number of secondary, allylic and doubly allylic hydrogens in each molecule by the equation: k
H={0.023[Hsec+ 0.112[Hallylic] + 1.78[Hddoubly allylic]}× 107M‐1s‐1
ORIENTATION MOVEMENTS OF CHLOROPLASTS IN Vallisneria EPIDERMAL CELLS: DIFFERENT EFFECTS OF LIGHT AT LOW‐ and HIGH‐FLUENCE RATE*
Authors: Izutani Yasuhiko , Takagi Shingo , Nagai Reiko 
Published: January 2008

Abstract— Epidermal cells of Vallisneria gigantea have a large central vacuole which is surrounded by a thin layer of cytoplasm. The chloroplasts are distributed over all six cytoplasmic layers of an approximate cuboid. In low‐intensity light, the accumulation of chloroplasts in the side facing the outer periclinal wall (the P side) continues for several hours. Red light (650 nm) shows the highest effect and induces such an accumulation even at a fluence rate of only 0.02 W/m2. In response to high‐intensity light, the chloroplasts move to the sides that face the anticlinal walls (the A sides) within a few tens of minutes. Blue light (450 nm) is most effective in inducing this movement. At a fluence rate of 1.51 W/m2, the reaction is induced in only half of the specimens. Neither red nor blue light can induce any orientation movement in the presence of 100 μg/ml of cytochalasin B.The chloroplast movements in the P side have been examined with a time‐lapse video system. When cells, in which the chloroplast accumulation has been completed after red‐light irradiation, are subsequently irradiated with blue light, the rapid movement of chloroplasts to A sides is induced. However, a considerable number of chloroplasts remains in the center of the P side. The same is true of cells in which the chloroplasts have not accumulated in the P side because of cytochalasin B treatment during red‐light irradiation, when such cells are irradiated with blue light after removal of the drug. Some anchoring mechanism seems to work in low‐intensity light to render the chloroplasts immobile in the P side.
BLUE LIGHT PHOTORECEPTION IN Neurospora ORCADIAN RHYTHM: EVIDENCE FOR INVOLVEMENT OF THE FLAVIN TRIPLET STATE
Authors: Fritz Bernhard J. , Kasai Sabu , Matsui Kunio 
Published: January 2008

AbstractThe mechanism of the photoreceptor acting on the circadian conidiation rhythm of Neurospora crassa was studied, with the following results: (1) the efficiency of 8‐haloflavins as sensitizers increased with their triplet yields. (2) Phase shifts were not abolished by removal of oxygen prior to illumination. (3) Oxygen inhibited phase shifts when introduced into the cultures after light treatment. It is proposed that the blue light photoreceptor for the circadian clock of Neurospora crassa acts (1) from its triplet state, but (2) not via singlet oxygen; (3) signal transduction involves (an) oxygen‐sensitive intermediate(s).
CHARACTERIZATION OF RADICAL ADDUCTS FORMED DURING PHOTOCHEMICAL SPIN TRAPPING IN LIPOSOMES
Authors: Sheng Pei‐GEN , Feix J. , Kalyanaraman B. 
Published: January 2008

Abstract—There exists an urgent need to monitor radical reactions in biological membranes. With the exception of a few studies in model and natural membranes, most biological spin trapping reactions have been confined to homogeneous media. In the present work we have devised a methodology by which spin trapping reactions can be investigated in liposomes composed of a fully‐saturated phospholipid, dimyristoylphosphatidylcholine. Using photochemical spin trapping, we have detected and characterized the formation and partitioning of spin adducts in liposomes. Benzophenone (a lipid‐soluble photosensitizer) and benzoyl peroxide (a lipid‐soluble radical initiator) have been used to generate free radicals from hydrogen donors during photolysis in liposomes. Both water‐soluble and lipid‐soluble spin traps have been used to trap the radicals.
DEPTH MEASUREMENTS AND HISTOPATHOLOGICAL CHARACTERIZATION OF PHOTODYNAMIC THERAPY GENERATED NORMAL BRAIN NECROSIS AS A FUNCTION OF INCIDENT OPTICAL ENERGY DOSE
Authors: Dereski M. O. , Chopp M. , Garcia J. H. , Hetzel F. W. 
Published: January 2008

AbstractThe response of normal brain to photodynamic therapy (PDT) was investigated in 62 Fisher rats. The animals were injected i.p. with Photofrin II (12.5 mg/kg). Forty‐eight hours following injection, an area of dura 5 mm in diameter over the frontal cortex was photoactivated with red light (632 ± 2 nm) at 100 mW cm−2, with no contributing thermal increases, at optical energy doses ranging from1–140 J cm−2 from an argon‐pumped dye laser. Appropriate controls were also prepared. Brain tissue samples for histological analysis were taken 24 h following PDT treatment. Maximum lesion depth perpendicular to the pial brain surface, was measured using an eyepiece micrometer. Lesions of increasing depth were generated as the incident optical energy dose was increased. Fitting the depth of necrosis to a natural log dependence of incident optical dose yielded a slope of 0.83 mm/In J cm−2 (r2=0.99). The intercept of 1.47 J cm−2 indicated the energy dose below which no normal tissue damage would occur at the incident laser intensity of 100 mW cm−2. The smallest lesions consisted almost exclusively of isolated neuronal injury and neuropil vacuolation, suggestive of an early ischemic lesion. Damage at the upper energy levels (35–140J cm‐2) consisted of complete coagulative necrosis identical to that induced by an arterial occlusion. The existence of viable tissue alongside neurons in various stages of necrosis at low energy levels (< 35 J cm−2) is suggestive of reversible injury and possibly clinically relevant treatment levels.
BIOCHEMICAL ISOLATION AND SPECTROSCOPIC CHARACTERIZATION OF POSSIBLE PHOTORECEPTOR PIGMENTS FOR PHOTOTAXIS IN A FRESHWATER Peridinium
Authors: Häder Donat‐P. , Liu Shi‐Mei 
Published: January 2008

AbstractPhotoreceptor pigments have been isolated biochemically from the freshwater dinoflagellate Peridinium gatunense, and characterized spectroscopically. At least four different chromoproteins can be detected in the crude extract and the membrane fraction isolated from the cells absorbing at 580, 638, 667 and 710 nm, which correspond with the maxima in the action spectrum for phototaxis in this organism. Light energy absorbed by shorter wavelength pigments is emitted as fluorescence at wavelengths which are absorbed by pigments with maxima at longer wavelengths. Protein separation on a MonoQ anion exchanger column using fast liquid chromatography resulted in a non‐bound fraction and four bound fractions eluted by an NaCI gradient, which differed in their pigment composition.
REGIOSELECTIVE PHOTOREDUCTION OF ZINC(II) PORPHYRINS TO GIVE CHLORINS
Authors: Iakovides Panos , Simpson Daniel J. , Smith Kevin M. 
Published: January 2008

ReferencesThe ascorbic acid/organic base photoreduction of zinc(II) porphyrins was investigated. It was established that certain substituents can direct the photoreduction to the site of the macrocycle to which they are attached. For example, zinc(II) vmy/porphyrins (8, 12, 16, 20) are photoreduced with cis stereochemistry on the ring bearing the vinyl group to give the corresponding chlorins. Zinc(II) acefy'porphyrins (22, 24) were likewise reduced to chlorins such that cis‐hydrogenation took place on the ring bearing the acetyl group. Zinc(II) formylporphyrins 33 also appear to reduce at the ring bearing the formyl group. When the zinc(II) acrylic porphyrin 28 was photoreduced, reduction did take place at the ring bearing the acrylic side chain, but migration of the acrylate double bond was very rapid, and the product isolated was the corresponding porphyrin propionate 30. Reduction of a zinc(II) porphyrin 35 bearing both a vinyl group and a nuclear carboxylic ester took place at the ring bearing the carboxylic ester. The reaction provides a general method for regioselective synthesis of chlorins from zinc(II) porphyrins without any evidence of formation of over‐reduction products characteristic of many other procedures for formation of chlorins from porphyrin precursors.