bluuebunny/crossref_metadata_2025 huggingface dataset:
INACTIVATION OF PHAGE BY NEAR‐ULTRAVIOLET RADIATION AND HYDROGEN PEROXIDE
Authors: Eisenstark A. , Buzard R. L. , Hartman P. S.
Published: January 2008

A series of phage with different genomes (both single‐stranded and double‐stranded RNA and DNA) was inactivated with hydrogen peroxide (H2O2) in various combinations with far‐ultraviolet (FUV) and near‐ultraviolet (NUV) radiations. In every case but one (a lipid‐coated phage), a sublethal H2O2 concentration greatly enhanced killing by NUV but not FUV. Moreover, this NUV/H2O2 synergism was oxygen independent and there was little if any host cell reactivation upon NUV plus H2O2 inactivation. These results suggest that these phage are inactivated by a common mechanism irrespective of nucleic acid composition, but that some phage genomes may be more vulnerable to NUV/H2O2 inactivation than others.
PHOTOINITIATED DNA DAMAGE BY MELANOGENIC INTERMEDIATES IN VITRO
Authors: H. Koch Walter , Chedekel Miles R.
Published: January 2008

Cysteinyldopas, metabolic by‐products of activated melanocytes, are photochemically unstable in the presence of biologically relevant ultraviolet radiation (i.e. wavelengths > 300 nm). Initial photochemical processes involve free radical production; continued photolysis yields polymeric photoproducts. Radicals produced during 5SCD photolysis were trapped by 5,5‐dimethyl‐l‐pyrrolidine‐l‐oxide (DMPO) and identified by their ESR spectra. Further characterization by use of nitroso spin trap (2‐methvl‐2‐nitrosopropane‐MNP) demonstrated that homolytic cleavage of the ‐S‐CH2 bond of the 5SCD cysteinyl side chain is a significant photochemical pathway. The potential photobiological significance of these reactive intermediates was investigated in vitro using isolated nucleic acids. Radiolabeled 5‐[35S]‐cysteinyldopa was found to photobind to calf thymus DNA with 300 nm light activation. Under similar conditions, 5‐S‐cysteinyldopa also induced single strand breakage of 3H‐radiolabeled superhelical, circular pBR322 plasmid DNA. The implications of the 5SCD photoinitiated DNA damage and the production of highly reactive free radicals in this process are discussed with respect to the etiology of various skin cancers, particularly malignant melanoma.
EFFICIENCY OF PHOTOAFFINITY LABELING DNA HOMOPOLYMERS AND COPOLYMERS WITH ETHIDIUM MONOAZIDE *
Authors: Dannelley Julia M. , Boyce Loretta , Gaubatz James W.
Published: January 2008

Abstract— Photoaffinity labeling of synthetic DN As with ethidium monoazide was studied to determine if the efficiency of adduct formation was related to DNA sequence. Equilibrium drug binding to DNA homopolymers and copolymers was quanitified by phase partition techniques. The amount of drug bound to a deoxypolymer at equilibrium was then compared to the fraction of ethidium analog covalently‐linked following photoactivation at the same drug/DNA input ratio. There were significant sequence‐related differences in the ability of the photoaffinity probe to label DNA covalently. The efficiency of covalent‐adduct formation decreased in the order poly(dG‐dC). poly(dG‐dC)> poly‐(dG). poly(dC)poly(dA‐dT). poly(dA‐dT)poly(dA). poly(dT). Ethidium monoazide was about 2‐fold more efficient in labeling deoxyhomopolymers and deoxycopolymers composed of G‐C pairs than the A‐T base counterparts. In low ionic buffers (0.015 M Na+), the efficiency of photoactivation decreased with increasing ethidium monoazide concentrations. However. the base sequence effect was observed over a 40‐fold range of drug concentrations. Therefore, the amount of ethidium monoazide bound to a DNA site after irradiation does not appear to represent the true affinity of the drug for that site.
ANTIVIRAL EFFECT OF HARMINE, A PHOTOACTIVE β‐CARBOLINE ALKALOID
Authors: Hudson J. B. , Graham E. A. , Towers G. H. N.
Published: January 2008

Abstract— Harmine, a β‐carboline alkaloid, was found to be an efficient photoactive agent against the DNA‐containing murine cytomegalovirus (MCMV) and the RNA containing Sindbis virus, a togavirus, both of which contain membranes. In contrast the host cells themselves were relatively resistant. The MCMV was investigated in more detail. Virus which had been inactivated by harmine plus UVA retained its structural integrity and was fully capable of penetrating host cells, following which the viral genome entered the cell nucleus. The viral genes which normally code for the switch‐off in thymidine kinase activity arid for the normal cytopathic effects were not expressed; however the viral geneis responsible for the cytotoxic effect due to high multiplicities of infection was still expressed, indicating that there may be a differential block of some viral genes
INVESTIGATION OF THE ANTIVIRAL ACTION OF THE PHOTOACTIVE COMPOUND PHENYLHEPTATRIYNE
Authors: Hudson J. B. , Graham E. A. , Towers G. H. N.
Published: January 2008

Abstract—Murine cytomegalovirus, a herpes virus, was used as a model virus to investigate the mechanism of the anti‐viral action of phenylheptatriyne in long wave ultraviolet light. The genome and proteins of the inactivated virus penetrated the nuclei of susceptible cells normally. Furthermore, the viral genome did not contain extra single strand breaks or cross‐links. However, cells infected with the treated virus did not synthesize late viral proteins, as determined by polyacrylamide gel electrophoresis. nor did they synthesize late viral RNA and viral DNA according to nucleic acid hybridization tests. Thus the compound may interfere with an early viral function so that the replication cycle cannot proceed.
EFFECT OF UV RADIATION ON SURVIVAL OF NON‐HAIRED MICE
Authors: Davies Ronald E. , Forbes P. Donald
Published: January 2008

Abstract— Patterns of mortality in a series of photocarcinogenesis experiments were examined. All experiments involved chronic irradiation of genetically non‐haired mice with simulated sunlight from a Xe lamp. Experimental variables included genetic origin of the test animals, incident dose of radiation, and the spectral quality of the radiation. In 16 experiments involving 10 genetic origins of mice the following patterns were detected: (1) survival was inversely proportional to the delivered radiation dose; (2) within origins the life‐shortening efficacy of radiation was closely correlated with its carcinogenic efficacy; (3) between genetic origins the carcinogenicity and lethality of a radiation dose were qualitatively correlated, but relative efficacy for the two effects varied; (4) altering the source spectrum by modifying the short‐wave (UVB) cutoff produced similar changes in carcinogenicity and lethality, suggesting that UVB was a significant contributor to lethal efficacy; (5) nature and relative timing of the carcinogenic response were such that carcinogenesis was not likely to have caused the observed mortality. It is speculated that systemic effects, possibly immunologic or toxic, are produced by chronic UV irradiation, and that these apparently cumulative, dose‐dependent effects result in premature death of non‐haired mice.
AN ACTION SPECTRUM FOR UV PHOTOCARCINOGENESIS *
Authors: Cole Curtis A. , FOrbes P. Donald , Davies Ronald E.
Published: January 2008

Abstract—Hairless mice were irradiated repeatedly by exposure to unfiltered black‐light (FR74T12 PUVA) fluorescent lamps and the time to development of skin tumors was determined. For several groups of animals the treatment variable was the size of the weekly dose. A similar approach had been used previously to determine dose‐response characteristics for other ultraviolet radiation emitting sources: a xenon arc solar simulator (with a series of five cut‐off filters producing five source spectra), and a fluorescent (FS40T12) “sunlamp”. The median tumor latent period (time period for just more than one half of the animals to develop at least one tumor each) was accurately predicted for all these ultraviolet radiation emitting sources by a mathematical equation incorporating the spectral source description and a spectral weighting function. The weighting function judged most appropriate for ultraviolet radiation‐induced photocarcinogenesis was the action spectrum, determined previously, for acute (single dose) skin edema in hairless mice. The mathematical equation assigns no effectiveness to wavelengths greater than 330 nm. There was no evidence for wavelength interaction in the spectral range of 26MW nm. Our data, combined with results of others, lead us to conclude that radiation with wavelength greater than 330 nm has an average relative efficacy (297 nm =1.0) less than 0.0002, and that this efficacy is not detectable with sources in which at least 2% of the UV radiation is in the UV‐B range.
POLARIZED PHOTO ACOUSTIC SPECTRA OF PHYCOBILISOMES IN POLYVINYL ALCOHOL FILMS
Authors: Frackowiak Danuta , Gantt Elisabeth , Hotchandani Surat , Lipschultz Claudia A. , Leblanc Roger M.
Published: January 2008

Abstract—Phycobilisomes fromPorphyridium cruentum, suspended in polyvinyl alcohol were found to be highly stable, and had normal absorption and fluorescence spectra. Intact phycobilisomes had a major emission peak at 680 nm, whereas upon partial dissociating the major emission was at 580 nm. Incorporation of phycobilisomes in thin polyvinyl alcohol films facilitated examination by photoacoustic spectroscopy. The photoacoustic spectra had a broad absorption maximum at 545–565 nm (phycoerythrin), which resolved as two peaks (545 and 563 nm) in absorption spectra. Stretching of films resulted in apparent chromophore reorientation in partially dissociated, but not in intact phycobilisomes. Only in dissociated phycobilisomes was observed a differential chromophore orientation at 685 nm by polarized fluorescence, which is attributed to a change in orientation of the terminal phycobilisome pigment relative to phycoerythrin.
LONG RANGE ELECTRON TUNNELING IN BIOLOGICAL AND MODEL SYSTEMS
Authors: Khairutdinov R. F. , Brickenstein E. Kh.
Published: January 2008

Abstract—This review paper reports the data on the role of long range electron tunneling in photosynthetic and model systems. The main papers concerned with elucidation mechanisms and kinetical peculiarities of electron transfer in reaction centers of bacteria and green plants are considered. The paper reviews the articles on long range electron transfer in reactions of metalloporphyrins—synthetic analogs of the main natural pigment of photosynthesis, chlorophyll. Liquid and solid phase redox reactions of electronically excited porphyrin molecules, intramolecular and photosensitized electron transfer processes are considered.
1,2‐BIS(4‐HYDROXYPHENYL)‐3,4‐DIHYDRO‐6‐HYDROXYNAPHTHALENE, A PHOTOFLUOROGENIC LIGAND FOR THE ESTROGEN RECEPTOR
Authors: Bindal Rajeshwar D. , Katzenellenbogen John A.
Published: January 2008

Abstract— 1,2‐bis(4‐Hydroxyphenyl)‐3,4‐dihydro‐6‐hydroxynaphthalene (6) is a non‐steroidal ligand for the estrogen receptor that displays photofluorogenic properties. It binds to the receptor with an affinity greater than that of estradiol (150%), and it is esentially non‐fluorescent. However, upon brief UV irradiation in protic media it is converted efficiently to an aryl tetraenedione system (8) that is highly fluorescent, but has low affinity for the receptor (0.35%). The aryltetraenedione has a complex electronic spectrum, with absorbance (and fluorescence excitation) bands extending beyond 450 nm. Both the maxima (εmax) and the intensity (φf of the fluorescence emission of the aryl tetraenedione are solvent dependent. The tetraenedione (8) is structurally related to a tetraenedione (13) obtained by photocyclization of diethylstilbestrol(l0); since tetraenedione 13 is essentially non‐fluorescent, it appears that the aryl dienone chromophore in 8 is responsible for its fluorescence. Photolysis of 6 in non‐protic media results in a direct photocyclization‐oxidation to benzodihydrochrysene system 9 that is unstable and has less desirable fluorescent properties. The formation of 8 from 6 in protic media (as contrasted to the formation of 9 in non‐protic media) is thought to arise from the competition that operates on the primary photocyclization product, dihydrophenanthrene (7): In protic media, ketonization proceeds more rapidly than oxidation (aromatization), while in aprotic media, oxidation is more rapid. This photofluorogenic ligand for the estrogen receptor should enable interesting fluorescence binding studies with the estrogen receptor to be performed.
DYNAMIC TOTAL FLUORESCENCE AND ANISOTROPY DECAY STUDY OF THE DANSYL FLUOROPHOR IN MODEL COMPOUNDS AND ENZYMES
Authors: Hoenes G. , Hauser M. , Pfleiderer G.
Published: January 2008

Abstract— The fluorescence of the dansyl group, covalently bound to lysine or tyrosine, was studied in model compounds and enzymes. The fluorescence lifetime of the model compounds strongly depends on solvent polarity and is different for the sulfonamide or sulfate binding type. These compounds rotate as spheres having radii corresponding to the molecules’dimensions. For the enzymes, we found a biexponential total fluorescence decay, because the dansyl groups were either located at two different lysines or bound to oxygen and nitrogen of the same tyrosine, the label always being surrounded by water. Dynamic fluorescence depolarization measurements showed, that the label rotates freely and fast relative to the protein which behaves as a sphere. In a peptide, however, some amino acids rotate together with the label.
CORRELATION BETWEEN THE BINDING OF FORMATE AND DECREASED RATES OF CHARGE TRANSFER THROUGH THE PHOTOSYSTEM II QUINONES
Authors: Jursinic Paul , Stemler Alan
Published: January 2008

Abstract—The binding parameters of bicarbonate to the thylakoid membrane at different formate concentrations have been established [Stemler and Murphy (1983)Photochem. Phorobiol. 38, 701–707]. Based on these parameters, predictions could be made concerning the effects of bicarbonate and formate on photosynthetic electron flow. In this work these effects of various concentrations of bicarbonate and formate are measured and compared to predictions from the binding study. Electron flow is measured between QAand QB(the primary and secondary quinone acceptors) and QBand the plastoquinone pool. Also, these same concentration effects are determined for silicomolybdate supported oxygen evolution. It is found that the results of the bicarbonate binding study are in good agreement with the concentration dependence determined for the quinone reactions, as well as the silicomolybdate reaction. The bicarbonate concentrations required for half‐maximal effects are approximately 100 μM, 300 μMand 1.3 mM in the presence of 0, 20mMand 100 mM formate, respectively. It is concluded that a hierarchy of possible electron flow rates exist. The slowest rates occur when formate is bound. A substantially higher rate occurs when neither formate nor bicarbonate (< 2 μM) are present, but only chloride is present. The highest rates of electron flow occur when bicarbonate is bound. The QA‐ QB→ Qa Qb−Qa−Qb2–PQ → QaQb‐ PQ2–, and the silicomolybdate reactions all have the same concentration dependence on formate and bicarbonate. From this it is concluded that a single binding site for formate and bicarbonate affect all of these reactions. The possibility that multiple sites exist with approximately equal affinities for bicarbonate cannot be excluded.
STRUCTURE OF METHYLPHEOPHORBIDE‐RCI*
Authors: Scheer H. , Gross E. , Nitsche B. , Cmiel E. , Schneider S. , Schäfer W. , Schiebel H.‐M. , Schulten H.‐R.
Published: January 2008

Abstract—The methanolic extract of the cyanobacterium (blue‐green alga)Spirulina geitlerihas been treated with methanolic acid to convert all chlorophyllous pigments to their methylpheophorbides. Fractionation of the latter from methylpheophorbideaby thin layer chromatography and high pressure liquid chromatography yielded methylpheophorbide‐RCI. Its structure has been determined as 132S‐hydroxy‐20‐chloro‐methylpheophorbideaby1H‐nuclear magnetic resonance, absorption and circular dichroism spectroscopy, mass spectrometry and by partial synthesis from chlorophylla. The pigment is isolated fromSpirulina geitleriirrespective of the use or omission of chlorinated substances during the isolation procedure.
AN ANIMAL MODEL OF SOLAR‐AGED SKIN: HISTOLOGICAL, PHYSICAL, and VISIBLE CHANGES IN UV‐IRRADIATED HAIRLESS MOUSE SKIN*
Authors: Bissett DonaldL. , Hannonand DanielP. , Orr ThomasV.
Published: January 2008

Albino hairless mice (Skh:HR‐l) exposed to sub‐erythemal doses of UVB or UVA radiation display physical, visible, and histological alterations. Skin surface replicas, transepidermal water loss, and skin fold thickness were found to change with irradiation. Visibly, the skin wrinkled with UVB and sagged with UVA exposure. These changes were graded on 3‐point scales. Histological alterations included tissue thickening, loss of elastic fibers, elastosis, loss of collagen, and increases in muco‐substances. The UVB alterations occur to a much lesser extent with an SPF‐15 (7% PABA and 3% oxybenzone) sunscreen product. This sunscreen product had little effect on development of UVA‐induced changes. However, an efficient UVA sunscreen (Parsol 1789) did reduce the UVA‐induced changes. Many of the UVB‐induced alterations regressed after UVB irradiation was stopped. No regression in UVA‐induced alterations was observed when UVA irradiation was stopped. Qualitatively, the effects with UVA irradiation were like those observed in mouse chronological aging. These models and the convenient physical and visible grading methods described can be used to determine the effectiveness of topical treatments, such as sunscreens.
RESISTANCE OF PIGMENTED HUMAN CELLS TO KILLING BY SUNLIGHT AND OXYGEN RADICALS
Authors: MUSK P. , PARSONS P. G.
Published: January 2008

Solar irradiation of a panel of human cell lines revealed three phenomena relevant to understanding the biological role of melanin; a heavily melanised melanoma line (MM418) was considerably more resistant to solar killing compared with HeLa and amelanotic melanoma cells of similar size and DNA content; MM418 cells were also resistant to killing by artificial UVB and by hydrogen peroxide generated in situ with extracellular glucose oxidase; and no difference in survival between the cell lines was found using 254 nm UV or gamma radiation. MM418 cells were resistant to sunlight when irradiated as attached monolayers but not when irradiated in suspension. Further studies showed that resistance to solar radiation in MM418 cells was not due to less DNA damage, as judged by inhibition of semiconservative DNA synthesis, or to enhanced constitutive or induced repair determined by reactivation of irradiated adenovirus. These results indicate that melanisation protects human cells from solar UVB in vitro and that the mechanism is associated with protection from hydrogen peroxide‐type damage rather than direct shielding of DNA.
TRANSPORT OF LIGHT IN TISSUE IN PHOTODYNAMIC THERAPY
Authors: Profio A. E. , Doiron D. R.
Published: January 2008

Abstract The dose rate in photodynamic therapy is proportional to the energy fluence rate and the concentration of the photosensitizer. Calculations of the energy fluence rate have been performed in slab, cylindrical and spherical geometries with the discrete ordinates transport method and diffusion theory. The attentuation of the energy fluence rate is least in slab geometry and greatest in spherical geometry. Violet (405 nm) light is attenuated much more rapidly than red (630 nm) light. Small tissue dimensions or narrow beam irradiation further decrease the energy fluence rate with radius and depth. Anisotropic scattering increases the energy fluence rate at large depths, but decreases it near the source. Measurements of the absolute energy fluence rate vs depth in a mouse tumor model exhibit an order of magnitude attenuation through the skin and a 3 mm thick tumor. Calculations of the energy fluence rate of the DHE fluorescence have been carried out to guide measurement of the concentration. Violet light excitation is much more efficient than red light excitation.
INDIRECT VERSUS DIRECT TECHNIQUES FOR THE MEASUREMENT OF THE OPTICAL PROPERTIES OF TISSUES
Authors: Wilson B. C. , Patterson M. S. , Flock S. T.
Published: January 2008

Abstract Knowledge of the optical absorption and scattering properties of tissues is required to calculate the spatial distribution of light in vivo for applications such as photodynamic therapy. In many soft tissues in the visible wavelength range the optical albedo is high, the scattering is highly forward peaked, and the mean free path between photon interactions is small. This regime presents severe technical difficulties in measuring the absorption and scattering coefficients. Two classes of technique may be used: 1. indirect methods in which, by applying specific models of light propagation, the properties are deduced from measurements of bulk tissue properties, and 2. direct, model‐free measurements using optically thin tissue samples. These two approaches are described and the relative advantages and disadvantages discussed. Data for the optical properties of model soft tissues at 630 nm are presented to illustrate the applications of indirect and direct methods.
PHOTOSENSITIZING PROPERTIES OF BACTERIOCHLOROPHYLLIN a and BACTERIOCHLORIN a, TWO DERIVATIVES OF BACTERIOCHLOROPHYLL a
Authors: Beems Eva M. , Dubbelman Tom M. A. R. , Lugtenburg Johan , Van Best Jaap A. , Smeets Monique F. M. A. , Boegheim J. Pierre J.
Published: January 2008

AbstractThe photosensitizing properties of two water soluble derivatives of bacteriochlorophylla, bacteriochlorophyllinaand bacteriochlorina(lacking the central Mg‐ion) were investigated and compared to those of hematoporphyrin derivatives. At physiological pH the oxygen consumption rate of histidine, tryptophan, dithiothreitol and guanosine upon illumination was 3 to 4 times higher when bacteriochlorinawas used as photosensitizer than when hematoporphyrin derivatives were used. Especially bacteriochlorinaproved to be an effective sensitizer for the killing of L929 cells. Because bacteriochlorinahas an absorption maximum at 765 nm in phosphate buffered saline (allowing a light penetration in tissue about ten times larger than at 630 nm) and a high molar absorption coefficient (32 000Mcm−1) it has promising possibilities for the application in photodynamic therapy.
ANTIVIRAL ACTIVITY OF MEROCYANINE 540
Authors: Sieber Fritz , O'Brien Jill M. , Krueger Gregory J. , Schober Sheri L. , Burns William H. , Sharkis Saul J. , Sensenbrenner Lyle L.
Published: January 2008

Abstract Simultaneous exposure to the lipophilic dye merocyanine 540 (MC 540) and white light inactivates several enveloped viruses. The same treatment appears to have little or no effect on pluripotent hematopoietic stem cells, mature red cells, and mature leukocytes. At least some components of the clotting system are spared, too. The molecular basis of the virucidal effect of MC 540 and light is not yet completely understood. Based on what is known about the interactions of MC 540 with cells and artificial membranes, it seems likely that MC 540 binds to and damages the viral envelope. MC 540‐mediated photosensitization may have implications for the sterilization of bone marrow and blood products, the preparation of vaccines, and selected areas of antiviral therapy.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES–VII. PHOTOINACTIVATION OF V‐79 CHINESE HAMSTER CELLS BY SELECTIVELY SULFONATED GALLIUM PHTHALOCYANINES
Authors: Brasseur Nicole , Ali Hasrat , Langlois Rejean , Van Lier Johan E.
Published: January 2008

Abstract Gallium chloride phthalocyanines sulfonated to different degrees were tested for their ability to inactivate V‐79 Chinese hamster cells in the presence of red light. The mono‐ and disulfonated compounds were the most active whereas the tri‐ and tetrasulfonated complexes were completely void of photoactivity. In addition, large variations in photoactivity were observed among the four isomeric disulfonated derivatives with the most hydrophobic isomer exhibiting the highest photoactivity. Prolonged exposure to the disulfonated complex resulted in increased photosensitization. Complexing the dye with Al instead of Ga resulted in a slightly increased photosensitizing effect.
THE CONTRASTING MECHANISMS OF COLONIC COLLAGEN DAMAGE BETWEEN PHOTODYNAMIC THERAPY and THERMAL INJURY
Authors: Barr H. , Tralau C. J. , Boulos P. B. , MacRobert A. J. , Tilly R. , Bown S. G.
Published: January 2008

Abstract The colon is protected from disruption and bursting pressures by the submucosal collagen layer. Photodynamic therapy with aluminium sulphonated phthalocyanine (AlSPc) does not cause perforation or reduction in the bursting strength of the rodent colon despite causing full thickness damage. Thermal injury also produces full thickness necrosis but causes perforation and considerably reduces the bursting strength of the colon. The differing mechanisms of damage were examined. Using transmission electron microscopy we examined collagen from undamaged normal rodent colon, colon damaged by photodynamic therapy and thermally injured colon. Following photodynamic therapy collagen maintained its architecture and periodicity. Thermally damaged collagen became grossly swollen and lost its fibrillary architecture. We have concluded that photodynamic therapy with AlSPc is collagen sparing.
A RANDOMIZED COMPARATIVE STUDY OF THE SAFETY and EFFICACY OF PHOTODYNAMIC THERAPY USING PHOTOFRIN II COMBINED WITH PALLIATIVE RADIOTHERAPY VERSUS PALLIATIVE RADIOTHERAPY ALONE IN PATIENTS WITH INOPERABLE OBSTRUCTIVE NON‐SMALL CELL BRONCHOGENIC CARCINOMA
Authors: Lam S. , Kostashuk E. C. , Coy E. P. , Laukkanen E. , LeRiche J. C. , Mueller H. A. , Szasz I. J.
Published: January 2008

Abstract To determine if photodynamic therapy (PDT) adds anything to conventional external beam radiotherapy (XRT) in patients with obstructive endobronchial tumors, 11 patients with inoperable non‐small cell bronchogenic carcinoma obstructing a central airway were randomized into either XRT alone or PDT followed by XRT. The most proximal site of obstruction was in the trachea (2), carina (3) or a main‐stem bronchus (6). The tumors involved more than one site in all patients. The histology was squamous cell in 9 and large cell carcinoma in 2. The age. location of tumor, degree of endobronchial obstruction and karnofsky rating were similar between the two groups. The radiation dose was 3000 cGy in 10 fractions over two weeks using a parallel pair technique. The patients were reassessed 4 and 12 weeks after completion of XRT and then quarterly thereafter. Response to treatment was assessed by changes in symptom scores, quality of life scores, bronchoscopy, quantitative ventilation perfusion lung scan, spirometric measurements and arterial blood gas sampling. All patients improved symptomatically with objective evidence of regression of their tumor at 4 weeks. Four out of five patients in the XRT group who had been followed for 12 weeks or more had progression of their tumor at 12 weeks. Three of them had died 155, 256 and 261 days respectively after treatment. Only i patients in the PDT + XRT group who had been followed for 12 weeks or more relapsed at 12 weeks and subsequently died 201 days after treatment. Two patients are still in complete remission 183 days and 310 days after treatment. Our preliminary results suggest that 3000 cGy radiation therapy alone offers only transient palliation for patients with obstructive endobronchial tumor. The addition of PDT prior to XRT provides significantly better and longer lasting local control. The combined treatment may also improve survival. It is possible that a therapeutic dose–6000 cGy radiation therapy may offer better local control than 3000 cGy.
PHOTOLYTIC DEGRADATION OF IBUPROFEN. TOXICITY OF THE ISOLATED PHOTOPRODUCTS ON FIBROBLASTS and ERYTHROCYTES
Authors: Castell J. V. , Gomez‐L. M. J. , Miranda M. A. , Morera I. M.
Published: January 2008

The photodegradation of Ibuprofen, a widely used non‐steroidal anti‐inflammatory drug (NSAID), was examined. Several photoproducts (I‐VI) were isolated and identified on the basis of their IR‐1H‐NMR‐ and 13C‐NMR‐ spectra. The chemical structures were confirmed by unambiguous alternative synthesis from available reagents. The most significant primary photochemical process was the cleavage of the C‐C bond a to the carboxy group. Subsequent secondary processes (hydrogen abstraction, dimerization, incorporation of methanol, or reaction with oxygen) might account for the formation of the different photoproducts. The cytotoxic effects were assayed using the red‐blood cell lysis test and the enzyme leakage (LDH and GOT) from cultured fibroblasts. Compound V [l‐(4 isobutylphenyl)‐ethanol] was found to be toxic for both system at concentrations greater than 1 mM while compound IV [l‐(4 isobutylphenyl acetophenone)] was toxic for fibroblasts but not for erythrocytes at the same concentration. Ibuprofen and the other photocompounds were apparently non‐toxic. The significance of these results is discussed in connection with the possible in vivo phototoxicity of Ibuprofen.
PHOTOELECTRIC EFFECTS IN BILAYER LIPID MEMBRANE CONTAINING METALLO‐PORPHYRINS and DYES
Authors: Kutnik Jan , Tien H. Ti
Published: January 2008

The bilayer lipid membrane (BLM) system containing metallo‐porphyrins (M‐TPP) and dyes as photosensitizers and electron mediators was studied. Cyclic voltammetry was used to determine photoconductivity and photo‐emf of the system. The largest photoconductivity was observed for the Mg‐TPP containing BLM with methyl viologen (MV2+) and iodine (I2) present in the aqueous solution. Photoactive dyes, due to their redox ability caused photovoltage up to 30 mV to develop, but no conductance change was observed under illumination in absence of Mg‐TPP. The relevance of cyclic voltammetry to the photoconductance and the photo‐emf observed in the BLM is discussed.
PHOTOINDUCED GENERATION OF HYDROGEN PEROXIDE AND HYDROXYL RADICALS IN MELANINS
Authors: Korytowski W. , Pilas B. , Sarna T. , Kalyanaraman B.
Published: January 2008

The hydrogen peroxide produced during photolysis of melanin pigments has been measured using an oxidase electrode. The photooxidation has been shown to occur via the superoxide intermediate. In the presence of superoxide dismutase the rate of photo‐induced production of hydrogen peroxide is increased, reflecting the ability of melanin to scavenge superoxide radicals. Evidence for metal‐ion dependent formation of hydroxyl radicals during photooxidation of melanin pigments was obtained using electron spin resonance‐spin trapping procedures. Superoxide dismutase increased the rate of formation of hydroxyl radicals in the system. Mechanisms of metal ion‐induced production of hydroxyl radicals during photolysis of melanin pigments are discussed.
THE EVOLUTION OF BIOLUMINESCENCE IN BACTERIA
Authors: Seliger H. H.
Published: January 2008

Individuals of aerobic, saprophytic bacterial species, encountering a changing environment in which they were regularly exposed to periods of severe hypoxia, would have gained a major selective advantage in fatty acid metabolism if a mutation in a flavoprotein oxygenase permitted them to oxidize accumulated C8‐C18 aliphatic aldehydes to fatty acids at oxygen concentrations below which the cytochrome oxidase mediated electron transport pathway became inhibited. Such mutants, able to continue to metabolize exogenous lipid fatty acids under hypoxia, might have outproduced their wild type ancestors. Colonies of those mutants which utilized reduced flavin mononucleotide (FMNH2) as the flavin cofactor would have been luminous, owing to the fortuitous coincidence that the aldehyde oxygenation resulted in an enzyme‐flavin excited electronic state which emitted blue light with a high fluorescence yield. If this accidental “proto‐bioluminescence” were initially of sufficient brightness to have elicited phototactic responses in nearby motile organisms, increasing thereby detrital food sources or the potential for dispersal and colonization for the bacteria, a new and completely different selective advantage, that of bioluminescent signalling, would have arisen from the original metabolic function. This is the biochemical analog of Darwin's principle of functional change in structural continuity. It is proposed that bacterial luciferase, the FMNH2‐oxygenase in luminous bacteria, was such a mutation. The present ubiquitous distributions of luminous bacterial species in marine waters, on the surfaces of marine animals and as symbionts in the specialized light organs and digestive tracts of many fish species have resulted from subsequent environmental selection and optimization for this original proto‐bioluminescent reaction. By extension it is suggested whereas “protobioluminescence” arose in many species independently whenever metabolic oxygenation of a substrate resulted in an adventitiously efficient chemiluminescence, the function of bioluminescence arose only upon favorable interaction between the “proto‐bioluminescence” and its ecosystem.
STEADY‐STATE NEAR‐INFRARED DETECTION OF SINGLET MOLECULAR OXYGEN: A STERN‐VOLMER QUENCHING EXPERIMENT WITH SODIUM AZIDE
Authors: Hall Robert D. , Chignell Colin F.
Published: January 2008

Abstract— A sensitive near‐infrared detection system incorporating improvements to existing methodologies has been used to characterize the sodium azide quenching of the steady‐state luminescence of singlet molecular oxygen at 1270 nm. Stern‐Volmer plots which were linear up to 80% quenching of the 1O2 generated by rose bengal and eosin Y yielded a rate constant of 5.8 ± 0.1 times 108M−1 s−1 for the quenching of 1O2 in water, while the rate constants obtained in deuterium oxide with the same sensitizers were 6.28 times 108M−1 s−1 and 6.91 times 108M−1 s−1 respectively. A flow system minimized the effects of photobleaching of the rose bengal. With a mercury arc light source, the instrument can be used in photosensitization experiments to detect low levels of 1O2 production in aqueous media.
THE PHOTOREACTIVITY OF PYRIMIDINE‐PURINE SEQUENCES IN SOME DEOXYDINUCLEOSIDE MONOPHOSPHATES AND ALTERNATING DNA COPOLYMERS
Authors: Kumar Shiv , Davmst R. Jeremy H.
Published: January 2008

Abstract—A reversed‐phase HPLC system has been developed which separates the common nucleo‐bases from the 6‐methylimidazo[4,5‐b]pyridin‐5‐one (6‐MIP) produced on acid hydrolysis of a thymine‐adenine photoadduct (TA*) that is formed between adjacent thymine and adenine bases in UV‐irradiated polydeoxyribonucleotides. By measuring the relative amounts of adenine and 6‐MIP in acid hydrolysates, this system has been used to investigate how polynucleotide conformation affects the yield of TA* in poly(dA‐dT) irradiated at 254 nm. The photoreactivity of other pyrimidine‐purine sequences has been examined with the deoxydinucleoside monophosphates d(TpI) and d(m5CpA) and with the alternating DNA copolymers poly(dA‐dU), poly(dI‐dC), poly(dG‐dC) and poly(dA‐dC).poly(dG‐dT). Samples were irradiated at 254 nm in aqueous solution and in ice, and at wavelengths >290 nm with acetone as photosensitizer. A photoproduct resembling TA*, and giving 6‐MIP on acid hydrolysis, was isolated from d(TpI) irradiated at 254 nm in solution or in ice; d(m5CpA) was comparatively unreactive. Acid hydrolysates of the irradiated DNA copolymers were screened by HPLC and by TLC and paper electrophoresis, for the presence of imidazo[4,5‐b]pyridin‐5‐one, 6‐MIP, or other species attributable to specific photoproduct formation. By this criterion, however, none of the copolymers showed evidence of significant photoreactivity in either their single‐ or double‐stranded conformational states. The formation of mixed pyrimidine‐purine photoadducts in DNA is therefore probably restricted to T‐A doublets.
SUNBURN CELL: FACTORS INVOLVED IN ITS FORMATION.
Authors: Danno Kiichiro , Horio Takeshi
Published: January 2008

Abstract— The sunburn cell (SC) is a type of individual cell death appearing in epidermis principally after exposure to middle‐wavelength UV radiation (UVR). Because SCs can easily be recognized by histologic characteristics, they may provide a countable index of assessment of the degree of UVR injuries. However, despite extensive investigations, the mode of formation of this UVR‐induced apoptosis has not fully been understood. In this review article, we are summarizing the results of recent studies with special reference to both the formation mechanisms and their implications in the field of photobiology.
IMPAIRED REPAIR OF UVC‐INDUCED DNA DAMAGE IN L5178Y‐R CELLS: SEDIMENTATION STUDIES WITH THE USE OF 5'‐BROMODEOXYURIDINE PHOTOLYSIS
Authors: Hagan Michael P. , Dodgen Daniel P. , Beer Janusz Z.
Published: January 2008

AbstractRelative to their L5178Y‐S counterparts, L5178Y‐R cells have an impaired capacity to form patches in DNA after exposure to UVC radiation. The photolysis of 5'‐bromodeoxyuridine (BrdUrd) incorporated into DNA was used to estimate the number of 'repair patches'formed in response to a 254 nm UV (UVC) exposure. L5178Y‐S cells, typical of rodent cell lines, formed a small number of patches in exposed DNA (1‐2 patches per 1 times 108 dalton during a 6 h recovery after an exposure of 20 J/m2). In contrast, DNA extracted from L5178Y‐R cells exposed to UVC and subsequently incubated with BrdUrd for 6 h showed no evidence of BrdUrd incorporation indicating no capacity to form sites of repair (fewer than 0.5 sites of BrdUrd incorporation per 1 times 108 dalton). Moreover, in L5178Y‐R cells high fluences of UVC caused an extensive DNA degradation. Such degradation was not observed in L5178Y‐S cells during the 24‐h post‐exposure period. These results are consistent with the notion that L5178Y‐R cells have a reduced capacity to repair DNA damage induced by UVC radiation.
PHOTOCHEMICAL PROPERTIES OF PORPHYRINc: AN AGENT FOR USE IN TUMOR PHOTOTHERAPY
Authors: Ghiggino Kenneth P. , Bennett Louise E. , Henderson Robert W.
Published: January 2008

Abstract—The absorption and fluorescence properties of porphyrinc(Pc), the porphyrin chromophore present in cytochromec, have been determined in several solvents and micellar environments. In aqueous buffer solutions at pH 7.5 Pc may exist in both a fluorescent monomeric form with quantum yield of fluorescence, (Φf,) ∼ 0.03, and fluorescence lifetime, (τf) ∼ 8 ns, and as a non‐fluorescent aggregate. The proportion of monomeric form is higher in organic solvents and micelles but is reduced with increasing porphyrin concentrations in aqueous solutions. Porphyrincreadily complexes with Zn2+to produce a fluorescent chelate (Zn‐Pc) with Φf, ∼ 0.02 and τf, ∼ 2 ns at pH 7.5. The yields of singlet excited oxygen formation from Pc and the Zn‐Pccomplex are higher than observed for hematoporphyrin derivative (HpD). Both Pcand Zn‐Pcare effective agents in tumor phototherapy and do not induce the prolonged cutaneous photosensitivity observed with the use of HpD.
PHOTOCHEMICAL TRANSFORMATIONS IN SALICYLANILIDE PHOTOALLERGY
Authors: EPLING GARY A. , WELLS JENNIE L. , YOON UNG CHAN
Published: January 2008

Abstract—The photochemical transformations of 3,3′,4′,5‐tetrachlorosalicylanilide, have been characterized by isolation and spectroscopic determination of the primary and secondary photoproducts. The photoreactivity cleanly involves photochemical dechlorination; three chlorines are ultimately lost in an efficient stepwise fashion. A radical mechanism was implicated by formation of a dimer and hydrogen atom abstraction from cysteine when present during photolysis. In the presence of HSA or BSA, the initial dehalogenation leads to a photoadduct with the protein, but dehalogenation of the primary photoproduct, a trichloro compound, does not lead to an efficient photobinding to protein.
AUGMENTATION OF ULTRAVIOLET ERYTHEMA BY INDOMETHACIN IN ACTINIC PRURIGO: EVIDENCE OF MECHANISM OF PHOTOSENSITIVITY
Authors: Farr P. M. , Diffey B. L.
Published: January 2008

Abstract— The effect of topical indomethacin on the intensity of erythema induced by ultraviolet radiation was measured by reflectance spectrophotometry in six patients with actinic prurigo. The intensity of UV‐C erythema was decreased by indomethacin in five patients. The intensity of UV‐B erythema was increased by indomethacin in five patients, and UV‐A erythema was increased by indomethacin in all patients. The increased inflammatory response induced by UV‐B and UV‐A with indomethacin application was related to erythemal sensitivity at these wavelengths. Topical indomethacin caused no change in the intensity of UV‐A erythema in a group of non‐photosensitive subjects.

That inhibition of cyclo‐oxygenase augments the inflammatory response to ultraviolet radiation suggests that lipoxygenase metabolites of arachidonic acid may be involved in the mechanism of photosensitivity in actinic prurigo.
PHOTOSENSITIZERS IN ORGANIZED MEDIA: SINGLET OXYGEN PRODUCTION AND SPECTRAL PROPERTIES
Authors: Gottfried V. , Peled D. , Winkelman J. W. , Kimel S.
Published: January 2008

Abstract—Measurement of singlet oxygen production by porphyrin‐type photosensitizers in simple buffer solutions show that TPPS is more efficient than PII (Photofrin II) or than hematoporphyrin. This behavior was observed using three independent analytical detection methods for1O2: RNO bleaching, tryptophan degradation, and oxygen consumption. Similar results were obtained when irradiating with a classical light source or with a pulsed dye laser. Addition of EPC liposomes to the buffer solution caused a decrease of efficiency for TPPS and an increase for PII. Addition of BSA shows the same relative pattern: a small increase of efficiency for TPPS and a tenfold increase for PII. These changes can be ascribed to specific interactions between the sensitizer molecules and the organized medium. Since changes in the fluorescence properties are also due to interactions with the medium, we monitored the emission of the sensitizers as a function of the environment. The fluorescence peak positions (at 648, 705 nm for TPPS and at 615, 677 nm for PII) were all red shifted. The intensities show an increase, particularly for PII in liposomes, due to a marked change in the microviscosity.
THE PHOTOPHYSICS OF MEROCYANINE 540. A COMPARATIVE STUDY IN ETHANOL AND IN LIPOSOMES
Authors: Aramendia Pedro F. , Krieg Marianne , Nitsch Christian , Bittersmann Edith , Braslavsky Silvia E.
Published: January 2008

Abstract— Absorption and fluorescence emission spectra, fluorescence lifetimes, fluorescence quantum yields, photoisomerization quantum yields and triplet quantum yields were measured for Merocyanine 540 (MC540) in ethanol and in large unilamellar dimyristoyl phosphatidylcholine vesicles. The major differences in the photophysics between the two media are the increase of the fluorescence quantum yield from 0.15 in ethanol to 0.6 in vesicles at 25° C, and the appearance of a second fluorescence decay with a lifetime of 1.87 ns in the latter medium. Upper and lower limits for the photoisomerization quantum yields were determined by combining the data from laser flash photolysis and optoacoustic spectroscopy. The decrease in photoisomerization quantum yield upon incorporation of the dye into the lipid bilayer by a factor 2 suggests that this process competes directly with fluorescence. The temperature dependence of the fluorescence and photoisomerization quantum yields in solution supports this model. In both media MC540 has a very low triplet quantum yield with values 0.002 > (> øT > 0.02 in ethanol and 0.01 > øT‐ > 0.09 in liposomes Our data are consistent with the model whereby the dye is incorporated into the lipid bilayer as a monomer with two different orientations and this model is adopted on the basis of the biexponential behaviour of the fluorescence and photoisomer decay.
STRUCTURAL PROPOSALS FOR THE MANGANESE CENTERS OF THE OXYGEN EVOLVING COMPLEX: AN INORGANIC CHEMIST'S PERSPECTIVE*
Authors: Pfxoraro Vincent L.
Published: January 2008

Abstract—This contribution provides an analysis of the basic coordination tendencies of manganese with specific emphasis on the biological chemistry of this element. The review is broken into four parts. First, a discussion of the basic coordination chemistry of manganese is mononuclear and multinuclear environments is presented. Second, the biophysical data essential to the development of models for the active center of the photosystem is examined. Third, recently reported mononuclear and cluster manganese compounds are profiled with an emphasis on relating the physical parameters of the models to the structure and function of the enzymatic system. Finally, a comparison is made between the OEC and other known manganoenzymes which metabolize the O2n‐moiety.
PHOTOEXCITATION OF ZINC PHTHALOCYANINE IN MOUSE MYELOMA CELLS: THE OBSERVATION OF TRIPLET STATES BUT NOT OF SINGLET OXYGEN
Authors: Firey P. A. , Jones T. W. , Jori G. , Rodgers M. A. J.
Published: January 2008

Abstract— Liposomes were used to deliver zinc phthalocyanine (ZnPC) to cultured mouse myeloma cells. ZnPC triplets states were observed when such systems were photoexcited. Singlet oxygen luminescence was not observed in cellular media. Solutions of ZnPC in various organic solvents, sodium dodecyl sulfate micelles and dipalmitoyl phosphatidyl choline liposomes were also prepared, and time‐resolved triplet state parameters and singlet oxygen production were measured for these systems to provide comparisons for the cellular suspensions.
INTERACTIONS AND PHOTOREACTIVITY OF 8‐ALKOXYPSORALENS WITH THYMINE. A MODEL APPROACH
Authors: Décout Jean‐Luc , Lhomme Jean
Published: January 2008

Abstract—To investigate the interactions and the photoreactions in solution between thymine and psoralen, model compounds have been synthesized in which a thymine molecule is linked to a psoralen ring by a polymethylene bridge. Two series of compounds have been studied and compared as models for the two major drugs 5‐MOP and 8‐MOP. We report here the results obtained in the 8‐alkoxypso‐ralen series. In water, intramolecular ring‐ring stacking interactions were evidenced using UV and1H NMR spectroscopies. In organic solvents such as ethanol, these interactions disappear completely. The photoreactivity of the models was examined in relation to their ground state interaction properties. in water and in ethanol. Slow photolysis of the pyrone ring of psoralen occurs whatever the length of the linking chain (3 to 12 methylenes). No intramolecular thymine‐psoralen photoaddition nor psoralen photodimerization were observed. These results are discussed with regards to the behavior of the 5‐alkoxy models which lead selectively to the 3,4 psoralen‐thymine photoadduct.
THYMIDINE UPTAKE, INCORPORATION AND DNA POLYMERASE ACTIVITY IN MURINE BLADDER TUMOR CELL,MBT–2, EXPOSED TO UV ACTIVATED DIHEMATOPORPHYRIN ETHER
Authors: Tseng Michael T. , Ling Yi‐He , Harty James I.
Published: January 2008

Abstract— Photodynamic therapy (PDT) is a new modality for treatment of malignancy. In this paper, we reported the effect of UV activated dihematoporphyrin ether (DHE) on [3H] thymidine uptake and DNA synthesis in murine bladder tumor cells,MBT–2. Exponentially growing cells were pretreated with 0.05–5μg/ml of DHE for 30 min in complete darkness prior to irradiation with 0.15‐0.90 J/cm2 of UV light (265 nm). The rates of thymidine uptake and DNA synthesis were suppressed in a DHE concentration and photic energy dependent manner. Double reciprocal analysis on the kinetics of the thymidine uptake and DNA synthesis indicated that the inhibition was non‐competitive, i.e. decrease in both the apparent Km value and maximum velocity in DHE plus UV light treated cells. The activities of DNA polymerase a and (3 were determined by [*H] dATP incorporation into DNA of permeabilizedMBT–2 cells. DNA polymerase a activity was approximately 60% of the control after 0.45 J/cm2 of UV light exposure; a further inhibition of DNA polymerase a was observed when 0.5–5ng/W of DHE and UV photoradiation were combined. In contrast, a slight stimulation of DNA polymerase fJ was noted after a similar treatment. This study demonstrates that photodynamic therapy‐induced suppression of DNA synthesis inMBT–2 cells is a complex process involving in reduction of thymidine transport as well as the perturbation of the enzymes involved in DNA synthesis.