bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDOGENOUS GLUTATHIONE PROTECTS HUMAN SKIN FIBROBLASTS AGAINST THE CYTOTOXIC ACTION OF UVB, UVA AND NEAR‐VISIBLE RADIATIONS
Authors: Tyrrell Rex M. , Pidoux Mireille
Published: January 2008

Both the UVB (290‐320 nm) and UVA (320‐380 nm) regions of sunlight damage human skin cells but, particularly at the longer wavelengths, information is scant concerning the mechanism(s) of damage induction and the roles of cellular defense mechanisms. Following extensive glutathione depletion of cultured human skin fibroblasts, the cells become strongly sensitized to the cytotoxic action of near‐visible (405 nm), UVA (334 nm, 365 nm) and UVB (313 nm) but not UVC (254 nm) radiations. In the critical UVB region, the magnitude of the protection afforded by endogenous glutathione approaches that of the protection provided by excision repair. The results suggest that a significant fraction of even UVB damage can be mediated by free radical attack and that a major role of glutathione in human skin cells is to protect them from the cytotoxic action of sunlight.
LIGHT‐INDUCIBLE ABSORBANCE CHANGES AND VANADATE‐SENSITIVE ATPase ACTIVITY ASSOCIATED WITH THE PRESUMPTIVE PLASMA MEMBRANE FRACTION FROM CAULIFLOWER INFLORESCENCES
Authors: Caubergs Roland J. , Asard Han H. , DeGreef Jan A. , Leeuwerik Frans J. , Oltmann Fred L.
Published: January 2008

Sucrose density gradient centrifugation of a microsomal membrane fraction of cauliflower inflorescences showed a strong correlation between a blue light mediated cytochrome b reduction (LIAC) and an ion stimulated nitrate‐insensitive but a vanadate‐sensitive ATPase activity at 38‐40% sucrose. LIAC activity and vanadate‐sensitive ATPase might be assigned to the same type of membrane different from ER, Golgi, tonoplast and mitochondria. The Mg2+‐dependent ATP‐hydrolytic activity obtained after purification of the microsomal fraction on an aqueous polymer two phase system was partially characterized. Temperature optimum (40°C), pH optimum (pH 7.0), vanadate inhibition (I50 at 20 μM), substrate kinetics (Km= 1.37 mM Mg.ATP) and inhibitor studies all point to the presence of the frequently described plasma membrane ATPase. Potassium and Na+ stimulated the enzyme activity (20‐40%). In general our data arc strongly in favour of the hypothesis that LIAC activity is localized on the plant plasma membrane. The cytochrome b involved in the light reaction has a midpoint potential near +150 mV. This cytochrome which has been previously shown in a cauliflower microsomal fraction is a constituent of the plasma membrane.
BIOLUMINESCENCE OF THE BRITTLE STAR OPHIOPSILA CALIFORNICA
Authors: Shimomura Osamu
Published: January 2008

The light‐emitting principle of the brittle star Ophiopsila californica has been isolated and purified. It was found to be a green‐fluorescent photoprotein (molecular weight 45000) which emits green light (λmax 500 nm) when H2O2 is added, independently of the presence or absence of O2. The green fluorescence (emission maximum 500 nm, excitation maximum 440 nm) spectrally coincided with the H2O2‐triggered luminescence, indicating that the green fluorescent chromophore is the light‐emitter of the photoprotein luminescence.
PHOTOELECTROCHEMICAL OXIDATION OF OXALATE ION IN AQUEOUS DISPERSIONS OF ZINC OXIDE
Authors: Domenech J. , Costa J. M.
Published: January 2008

The photooxidation of oxalate ions in aqueous dispersions of ZnO under UV‐illumination has been investigated in order to determine the efficiency of oxalate ions as hole scavangers. The process has been studied by measuring the quantity of oxalate ions photooxidized at different experimental conditions. It is observed that the number of moles of oxalate photodecomposed increases with irradiation time and with the mass of semiconductor in suspension, attaining in this case a limiting value. Also, the amount of oxalate ions photooxidized increases with both initial oxalate concentration and light intensity. These results are discussed in terms of the different redox processes that take place at the semiconductor particle‐electrolyte interface.
PHOTOLYSIS OF PHEOMELANIN PRECURSORS: AN ESR‐SPIN TRAPPING STUDY
Authors: Pilas Barbara , Felix Christopher C. , Sarna Tadeusz , Kalyanaraman B.
Published: January 2008

The photolysis of 5‐S‐cysteinyldopa, 2,5‐S,S‐dicysteinyldopa, 4‐hydroxybenzothiazole and cysteinyldopa melanins has been studied by ESR‐spin trapping methods using 5.5‐dimethyl‐1‐pyrroline‐1‐oxide and 2‐methyl‐2‐nitrosopropane as spin traps for hydrated electrons, hydrogen atoms, and carbon‐centered alanyl radicals. The photochemistry of these materials is shown to resemble dopa in that both photoionization and photohomolysis occur. However, unlike dopa, the cysteinyldopa also forms the carbon‐centered alanyl radicals via photodecomposition of the cysteinyl group. Action spectra and quantum yields are reported. Mechanism(s) of radical formation are discussed.
PHOTOBINDING OF PSORALENS TO BACTERIAL MACROMOLECULES IN SITU AND INDUCTION OF GENETIC EFFECTS IN A BACTERIAL TEST SYSTEM. EFFECTS OF SINGLET OXYGEN DIAGNOSTIC AIDS D2O AND DABCO
Authors: Mol N. J. de , van Henegouwen G. M. J. Beijersbergen , Weeda B. , Knox C. N. , Truscott T. G.
Published: January 2008

The photobinding of radiolabeled psoralen and 8‐methoxypsoralen (8‐MOP) to biological macromolecules under conditions that affect the lifetime of singlet oxygen (1O2) is reported. These conditions are: increase of 1O2 lifetime in D2O and 1O2 quenching with DABCO. The photobinding to calf thymus DNA was studied in vitro and the covalent photobinding to DNA and other biological macromolecules (RNA, proteins) was also studied in intact bacteria. The results of the DNA photobinding experiments have been related to the induction of genetic damage in a bacterial test system. In addition, laser flash photolysis has been used to measure the effect of D2O and DABCO on the psoralen and 8‐MOP triplet lifetimes. In general D2O increases the triplet lifetimes and DABCO quenches the triplet states with the probable formation of radicals. The results suggest that the covalent photobinding of 8‐MOP to various biological macromolecules in situ is a basis for cell damage occurring at various cellular targets. Analysis of the results of the mutagenicity test suggests that in the presence of D2O the mechanism of induction of genetic lesions is not changed and therefore largely seems to be independent of singlet oxygen.
PROPERTIES OF SYNTHETIC BACTERIORHODOPSIN PIGMENTS. FURTHER PROBES OF THE CHROMOPHORE BINDING SITE
Authors: Crouch Rosalie K. , Scott Rick , Ghent Shawn , Govindjee Rajni , Chang Chung‐Ho , Ebrey Thomas
Published: January 2008

Abstract— A series of retinals with specific structural alterations have been synthesized to probe the bacteriorhodopsin binding site. The 4‐chloro‐, 4‐bromo‐ and 4‐iodoretinals all form pigments with bacterioopsin but undergo an in situ displacement of the allylic halogen to form the 4‐hydroxyretinal pigment. Several naphthyl retinals were prepared which effectively extend the polyene chain and/or add bulk to the ring portion of the chromophore. All the naphthyl retinals form pigments with bacterioopsin but only the pigment containing the derivative with a polyene side chain identical to that of retinal pumps protons efficiently. The 12‐butyl‐13‐desmethylretinal was also synthesized but this analogue did not form a pigment with bacterioopsin. These results confirm the nonspecificity at the ring portion of the chromophore binding site and the importance of the role of the polyene chain in the proton pumping function of bacteriorhodopsin.
IDENTIFICATION AND LOCALIZATION OF PHOTOALKYLATED BASES IN DNA FRAGMENTS
Authors: (Noy) Etta Livneh , Sperling Joseph
Published: January 2008

Abstract— Antibodies directed toward 8‐(2‐hydroxy‐2‐propyI)‐deoxyguanosine‐5′‐monophosphate (8‐hpdGMP), a product of the photoalkylation of deoxyguanosine‐5‘‐monophosphate with 2‐propanol, were shown to be highly specific and sensitive in detecting 8‐hpdGMP residues in photoalkylated DNA.

The antibodies were further used to determine the distribution of modified guanine residues in DNA. The irradiated DNA was digested with restriction enzymes and the fragments obtained were separated electrophoretically and blotted onto diazotized paper. The covalently bound DNA fragments were probed with the antibodies and then with 125I Staphylococcus aureus protein A. These experiments indicate a non‐random distribution of modified guanine residues in øX174 RF DNA molecules.
DEVELOPMENT OF A PLAQUE REDUCTION ASSAY AND APPLICATION TO THE STUDY OF PSORALEN‐DAMAGED DNA
Authors: Yokobata Kathy E. , Jordan John M. , Chapman Orvrlle , Krerl Curt
Published: January 2008

Abstract— We have developed a procedure called a plaque reduction assay to assess the biological activity of duplex circular DNA modified by covalent adduct formation with psoralen derivatives. The replicating form (RF) of bacteriophage DNA modified by photochemical addition of a psoralen derivative was introduced into bacterial cells using the CaCI2 transfection method. The transfected cells. plated upon a confluent lawn of cells permissive for the bacteriophage in the inoculum, provided a measure of the reduction in infectivity of the RF DNA which resulted from its covalent modification. Use of this assay is illustrated in studies which screened and compared the activities of several recently synthesized psoralen derivatives. We describe two new compounds. β‐(8‐psoralenoxy)‐ethanol and β‐(8‐psoralenoxy)ethylamine that are significantly more active than either 8‐methoxypsoralen or trioxsalen in the biological assay
PHOTOHEMOLYSIS OF ERYTHROCYTES ENRICHED WITH SUPEROXIDE DISMUTASE, CATALASE AND GLUTATHIONE PEROXIDASE *
Authors: Finazzi‐Agro Alessandro , Giulio Antonio Di , Amicosante Gianfranco , Crifó Carlo
Published: January 2008

Abstract— Cationic liposomes have been used to introduce into human erythrocytes variable amounts of the enzymes superoxide dismutase, catalase and glutathione peroxidase. The behaviour of the enzyme‐enriched erythrocytes toward photohemolysis sensitized by protoporphyrin IX has been studied in comparison to that of erythrocytes treated with empty liposomes. The erythrocytes with increased catalase and glutathione peroxidase activity were more resistant to photohemolysis. In contrast, the erythrocytes enriched with superoxide dismutase hemolyzed faster. The association of two enzymes at a time was also studied
BOOK REVIEW
Authors: Baskin Tobias I. , Watanabe Masakatsu
Published: January 2008

Sensory Perception and Transduction in Aneural Organ isms, NATO AS1 Series A: Life Science, Vol.
SUPPRESSION OF THE INDUCTION OF DELAYED‐TYPE HYPERSENSITIVITY REACTIONS IN MICE BY A SINGLE EXPOSURE TO ULTRAVIOLET RADIATION
Authors: Ullrich Stephen E. , Azizi Esther , Kripke Margaret L.
Published: January 2008

Abstract— After a single exposure of mice to UV radiation, their ability to generate a contact hypersensitivity (CHS) response to contact sensitizers applied epicutaneously to distant, unirradiated skin is severely impaired. It is not clear, however, if the classic delayed type hypersensitivity (DTH) reponse to exogenous antigens, injected into the subcutaneous (s.c.) space, can also be modulated by UV radiation. We report here that a single exposure of mice to UV radiation suppressed the induction of DTH to both erythrocyte and soluble protein antigens injected s.c., but did not suppress the elicitation of the response. The suppressive effect was abrogated by cyclophosphamide treatment. In addition, antigen‐specific suppressor cells were found in the spleens of the mice with a decreased DTH response. Since the ability to mount a DTH response has been linked with the resistance to certain pathogenic microorganisms, we suggest that the suppression of DTH by UV radiation may have the potential to compromise host resistance to such infectious agents.
THE EFFECT OF IONIC STRENGTH AND pH ON THE PROTONATED SCHIFF BASE AND TYROSINE DEPROTONATION KINETICS DURING THE BACTERIORHODOPSIN PHOTOCYCLE
Authors: Corcoran Timothy C. , Dupuis Paul , El‐Sayed M. A.
Published: January 2008

Abstract— The deprotonation kinetics of tyrosine and the protonated Schiff base during the bacteriorho‐dopsin photocycle were studied under different perturbations by transient absorption spectroscop Native purple membrane, as well as samples which were deionized (blue) then restored with Na+ or La3+ were used at pH's ranging from 7 to 10 at very low salt concentrations. The results were compared with previous studies at higher ionic strength. The important conclusions can be summarized as follows: (a) The rate constants of both the Schiff base and tyrosine deprotonation are not very sensitive to the changes of conditions. (b) An almost linear relationship is observed between the relative amplitudes of the tyrosine deprotonated during the cycle and the slow component of the Schiff base deprotonation under the different perturbations studied. This was taken to support the two site model for the protonated Schiff base, one near tyrosine and the other near its ionized form. (c) The pKa value determined from the ratio of the amplitude of the fast to the slow component of the Schiff base deprotonation is found to decrease with increasing ionic strength of the medium. At extremely low ionic strength, it was found to equal that of the tyrosine phenolic group in solution.
RECOVERY OF SUBCHROMOSOMAL DNA SYNTHESIS IN SYNCHRONOUS V‐79 CHINESE HAMSTER CELLS AFTER ULTRAVIOLET LIGHT EXPOSURE
Authors: Meechan P. J. , Carpenter J. G. , Griffiths T. D.
Published: January 2008

Abstract— Previous work obtained from Chinese hamster V‐79 cells indicated that, immediately following exposure, UV‐induced lesions acted as blocks to elongation of nascent strands, but gradually lost that ability over a 10 h period after exposure to 10 J/m2. The work reported herein attempted to examine possible cell cycle mediated alterations in the recovery of DNA synthesis. Kinetic incorporation of radiolabeled thymidine studies indicated that there may have been a more rapid recovery of DNA synthesis in cells irradiated in G1 or G2vs cells irradiated in S phase. DNA fiber autoradiograms prepared from synchronous cells indicated that after irradiation in any phase of the cell cycle, the length of newly synthesized DNA was equal to control lengths 1 h after exposure to 5.0 J/m2 (or 1 h after entering S phase for cells irradiated in G1 or G2). This observed recovery was not solely due to an excision process. No cell cycle mediated difference in the number of dimers induced or removed as a function of cell cycle position was observed. These results appear to be consistent with a continuum of effects, with initiation effects dominating the response at low fluences, gapped synthesis at intermediate fluences and elongation inhibition at high fluences. The fluences at which each event dominates may be cell‐line specific.
METABOLISM OF tRNAs IN GROWING CELLS OF Escherichia coli ILLUMINATED WITH NEAR‐ULTRAVIOLET LIGHT
Authors: Hajnsdorf Eliane , Favre Alain
Published: January 2008

Abstract— The tRNA metabolism which accompanies illumination of growing E. coli cells has been examined in conditions that led to growth delay. (i) The in vivo formation of the 8–13 link was followed by a fluorimetric procedure and revealed pseudo‐first order kinetics very close to those obtained in vim under the same illumination conditions. The yield of 8–13 link appears to be quantitative (± 10%). Comparison of these kinetics with the radiochromatographic data of Blanchetot et al. (1984) suggests the transient formation during illumination of a new RNase‐T,‐resistant dinucleotide in tRNA distinct from the 8–13 link. (ii) Evidence is provided that under illumination some tRNA molecules lack one or more bases in a specific position in the sequence, thus yielding discrete fragments after aniline treatment. (iii) During the growth lag, uracil incorporation into nucleic acids occurs at an apparent rate between 4–8% of that normally observed during exponential growth. Evidence is provided however that the pyrimidine ribonucleoside triphosphate pools are strongly perturbed after illumination. Comparison of exogenous [3H]uracil incorporation into two strains proficient or deficient in uracil biosynthesis suggests a derepression of the endogenous path after light treatment. In addition, the UTP‐to‐CTP conversion is inhibited. In spite of preferential incorporation of exogenously labelled uracil in tRNA after illumination, a possible pyrimidine base turnover cannot be proved. These data are compatible with tRNA repair (Blanchetot et al., 1984) involving a few tRNA species.
CHANGE IN SULFHYDRYL GROUP MICROENVIRONMENT OF CALF LENS α‐CRYSTALLIN BY 300 nm LIGHT
Authors: Andley Usha P. , Chylack Leo T.
Published: January 2008

Abstract— The effect of 300 nm irradiation on the sulfhydryl groups of calf lens a‐crystallin has been investigated by using specific, covalently bound fluorescent sulfhydryl probes 4–(N‐iodoacetoxy)ethyl‐N‐methylamino‐7‐n‐itrobenz‐2‐o‐xa‐1,3‐d‐iazole (IANBD), N‐iodoacetyl‐N′‐(5‐s‐ulfo‐l‐naphthyl) ethylene‐diamine (1,5 IAEDANS) and 5‐i‐odoacetamidofluorescein (IAF). The decrease in tryptophan fluorescence with time of irradiation of a‐crystallin, is accompanied by a decrease in the fluorescence of the hydrophobic sulfhydryl label IANBD. In addition, the fluorescence of the surface‐sulfhydryl label IAF increased in the irradiated a‐crystallin. These results indicate that the sulfhydryl groups are in a more exposed (hydrophilic) environment in the irradiated protein than in the control, possibly because of partial unfolding of the protein. This result is confirmed by fluorescence lifetime measurements with IAEDANS. The decay curve of IAEDANS‐α‐crystallin has a major lifetime of 15.7 ns and a minor one of 24.6 ns. Upon irradiation, the lifetime of the major component decreases to 10.2 ns and that of the minor component to 21.7 ns. Denatured IAEDANS‐α‐crystallin has a single lifetime of 10.4 ns. These results show that the photoinduced damage to the tryptophan residues of α‐crystallin alters the environment of the sulfhydryl groups and induces a change in the tertiary structure of the protein. Proximity of the cysteine residues to tryptophan in the tertiary structure of the protein may be an important determinant of their susceptibility to photoinduced change.
RADICAL CATION PRODUCTION IN THE PHOTOLYSIS OF 5‐M‐ETHOXY‐1‐M‐ETHYLINDOLE
Authors: Kuntz Robert R.
Published: January 2008

Abstract— The flash photolysis of 5‐m‐ethoxy‐1‐m‐ethylindole in aqueous media was studied for the purpose of assigning the absorption spectrum of the radical cation. Transients produced in this study were analogous to those formed in the photolysis of 5‐m‐ethoxyindole. The major transient observed with an absorption maximum of 460 nm was O2‐s‐ensitive and had a lifetime of 20 μs in nitrogen saturated solutions. One radical species is produced with absorption maxima at 445 and 530 nm. Ionic strength effects on the reaction of this species with I− confirms that it is the radical cation of 5‐m‐ethoxy‐l‐methylindole. The effect of H+ and Br− on the fluorescence, radical cation and triplet yields is discussed in relation to the mechanism of transient formation.
THE DESIGN AND IMPLEMENTATION OF SOFTWARE FOR THE COMPATIBILITY OF SPEX DATAMATE PROCESSORS WITH APPLE II COMPUTERS
Authors: Findsen E. W. , Ondrias M. R.
Published: January 2008

Abstract— A program and protocol for transferring data from the SPEX Datamate controller/data acquisition system to an APPLE II series computer are described. The Datamate system is currently widely used in both Raman and fluorescence instrumentation. No hardware modification is required to implement this economical and versatile alternative to the dedicated disk storage offered by the manufacturer.
REPAIR OF CYCLOBUTANE DIMERS AND (6–4) PHOTOPRODUCTS IN ICR 2A FROG CELLS
Authors: Mitchell David L. , Clarkson Judith M. , Chao Chuck C.‐K. , ROSENSTEIN Barry S.
Published: January 2008

Abstract— The removal of cyclobutane dimers and Pyr(6–4)Pyo photoproducts from the DNA of UV‐irradiated ICR 2A frog cells was determined by radioimmunoassay. In the absence of photoreactivat‐ing light, 15% of the cyclobutane dimers and 60% of the (6–4) photoproducts were removed 24 h post‐irradiation with 10 J m−2, Exposure to 30 kJ m−2 photoreactivating light resulted in removal of 80% of the cyclobutane dimers and an enhanced rate of repair of (6–4) photoproducts, resulting in a loss of 50% of these lesions in 3 h. The preferential removal of (6–4) photoproducts by excision repair resembles previously published data for mammalian cells.
ANALYSIS OF FLASH PHOTOLYSIS DATA BY A GLOBAL FIT WITH MULTI‐EXPONENTIALS–II. DETERMINATION OF CONSISTENT NATURAL RATE CONSTANTS and THE ABSORPTION SPECTRA OF THE TRANSIENT SPECIES IN THE BACTERIORHODOPSIN PHOTOCYCLE FROM MEASUREMENTS AT DIFFERENT TEMPERATURES
Authors: Maurer R. , Vogel J. , Schneider S.
Published: January 2008

A procedure is described which allows one to deduce from flash photolysis data (absorbance change vs time) recorded at different temperatures the natural rate constants for the elementary reaction steps and the transient absorption spectra of the intermediates within a given kinetic scheme. The selected solutions fulfil two requirements: (i) the rate constants for different temperatures follow Arrhenius’law; (ii) the absorption spectra of the intermediates are independent of temperature. The method is applied to the photocycle of bacteriorhodopsin; the selected model comprises two L‐species, a branching at the M‐intermediate directly back to BR and an equilibrium between M and O.
THE QUANTUM EFFICIENCY FOR THE INTERPHOTOCONVERSION OF THE BLUE and PINK FORMS OF PURPLE MEMBRANE
Authors: Liu S. Y. , Ebrey T. G.
Published: January 2008

When the cations bound to purple membrane are removed it turns blue, and when this blue membrane is irradiated its color changes to pink. Irradiation of pink membrane leads to the reformation of blue membrane. We have determined that the quantum efficiency for the formation of pink membrane from deionized blue membrane is 1.6 ± 0.6 ± 10 4 at 0oC, pH 5.0. We also found that the quantum efficiency for the back photoconversion, i.e. the formation of blue membrane from pink membrane, is 8.8 ± 1.6 ± 10‐3 at 0oC, 55 times greater than that of the forward photoconversion reaction. The extinction coefficients of the pink membrane and blue membrane were determined to be 44 500 ± 670 cm‐1 M‐1 at 491 nm and 54 760 ± 830 cm‐1M‐1 at 603 nm, respectively, assuming light‐adapted purple membrane is 63 000 cm‐1M‐1 at 568 nm. The quantum efficiency for forming pink membrane from blue membrane is much lower than that for forming the photointermediate of the blue membrane's photocycle. Their relationship is similar to that of light‐adaptation and photocycle of the dark‐adapted purple membrane.
ALL‐trans β‐CAROTENE‐5,6‐EPOXIDE IN THYLAKOID MEMBRANES
Authors: Ashikawa Ikuo , Kito Mariko , Satoh Kimiyuki , Koike Hiroyuki , Inoue Yorinao , Saiki Kayoko , Tsukida Kiyoshi , Koyama Yasushi
Published: January 2008

All‐transβ‐carotene‐5,6‐epoxide has been found in the thylakoid membranes of spinach and of the cyanobacterium Synechococcus vulcanus Copeland. The epoxide was extracted from the thylakoid membranes with acetone, and was isolated by high‐performance liquid chromatography (HPLC). The structure of the epoxide was identified by means of mass, Raman, and electronic absorption spectroscopy. Changes in the amount of the epoxide, as a result of epoxidation and (apparent) de‐epoxidation reactions in the membranes, were traced by analysis of extracts on HPLC. In isolated thylakoid membranes, only the epoxidation reaction took place. The reaction was caused by irradiation or by the addition of ferricyanide, suggesting that electron transport reactions in the membranes are involved in the epoxidation. In intact spinach leaves, however, both epoxidation and de‐epoxidation took place; the extent of epoxidation correlated with the intensity of light incident on the leaves. The epoxidation and de‐epoxidation of all‐transβ‐carotene are contrasted with those of xanthophylls (in the violaxanthin cycle).
CHEMISTRY OF SINGLET OXYGEN—48. ISOLATION and STRUCTURE OF THE PRIMARY PRODUCT OF PHOTOOXYGENATION OF 3,5‐DI‐t‐BUTYL CATECHOL
Authors: Jensen Frank , Foote ChristopherS.
Published: January 2008

The dye‐sensitized photooxygenation of t‐butyl substituted catechols has been investigated. The primary product from 3,5‐di‐t‐butyl catechol has been isolated and shown to be a hydroperoxydienone by single crystal X‐ray diffraction. The absence of sensitizer effects and the faster reaction rate in polar solvents suggest that the reaction proceeds with singlet oxygen as the primary oxygenating species. Charge‐transfer or full electron‐transfer from the catechol to singlet oxygen is probably involved. Substituent effects are in agreement with this mechanism. The products from thermal breakdown of the hydroperoxydienone are inconsistent with a Baeyer‐Villiger mechanism.
CUTANEOUS PHOTOTOXICITY OF TETRACYCLINE ANTIBIOTICS: GENERATION OF FREE RADICALS and SINGLET OXYGEN DURING PHOTOLYSIS AS MEASURED BY SPIN‐TRAPPING and THE PHOSPHORESCENCE OF SINGLET MOLECULAR OXYGEN
Authors: Li AnsonS. W. , Chignelland ColinF. , Hall RobertD.
Published: January 2008

Chlortetracycline (CTC) generated an aryl radical in aqueous buffer (pH 7.4) during near UV irradiation, as evidenced by the formation of 2‐methyl‐2‐nitrosopropane spin adducts. The radical was produced via dechlorination, a photoprocess not previously reported for tetracyclines. Demeclocyc‐line (DEM), another chlorinated tetracycline, did not produce detectable aryl radicals. Relative 1O2 yields obtained by direct luminescence measurements at 1268 nm for five tetracyclines in alkaline ethanol (demeclocycline · tetracycline · chlortetracycline · doxycycline · minocycline) showed that DEM produced approximately three times as much singlet oxygen as CTC. This constitutes direct evidence that tetracyclines sensitize both Type I and Type II photoreactions.
SPECTROSCOPIC EXAMINATION OF HYDROGEN BONDING and PROTON TRANSFER IN MODEL SCHIFF BASES RELATED TO THE VISUAL PIGMENT CHROMOPHORE
Authors: Al‐Dilaimi S. K. , Aumiller J. C. , Johnsonand R. H. , Blatz P. E.
Published: January 2008

By means of a variable low temperature cell holder, double beam spectra were obtained to temperatures as low as 88 K. As the temperature was lowered for a 3McP solution containing N‐2,4,6,8,10‐dodecapentaenylidene‐n‐butylamine (2) and phenol, three separate species could be detected, (i) The first spectrum taken at room temperature exhibits sharp fine structure and is the unperturbed spectrum of 2. As the temperature is lowered, a completely new spectrum with fine structure develops at slightly longer wavelength while simultaneously the old fine structure disappears. (ii) The new spectrum belongs to the H‐bonded species formed between 2 and phenol. As temperature is further lowered, the second spectrum disappears as a new band develops at about 440 nm. (iii) This is the proton transferred species. The same phenomenon is repeated when p‐nitrophenol and acetic acid are substituted for phenol. The ‐ΔH and ΔS values for the H‐bonding process between phenol and 2 in 3MeP are 3900 cal mol‐1 and 1.4 cal dgr‐1 mol‐1 respectively. Additional experiments firmly establish the process to be H‐bonding with the phenolic hydroxyl group. Alcohol also H‐bonds with 2 but does not proton transfer.
MONITORING LIGHT‐INDUCED CHANGES IN ISOLATED, INTACT EYE LENSES
Authors: Rao Ch. Mohan , Balasubramanian D. , Chakrabarti B.
Published: January 2008

Fluorescence spectral changes occurring upon irradiation with 300 nm light have been monitored in situ in isolated, intact, whole lenses from the eyes of several species. The findings corroborate observations on other individual constituent protein molecules in the solution state, and also reveal features attributable to the supramolecular protein assembly that exists in the whole lens. Irradiation of the lens with 300 nm light causes red shifts in the tryptophan emission spectrum, suggesting alterations in the protein packing in the lens. Intermolecular energy transfer from tryptophan to one of the photoproducts, presumably N‐formylkynurenine (N‐FK), occurs in the condensed‐phase sample. The N‐FK formed is photodegraded efficiently in the lens, indicating that the photodynamic effects of endogenous N‐FK might not be as severe as has been thought. Species variation in the photoevents are evident, particularly in avian lenses that contain the variant δ‐crystallin as the core protein. The photoinduced changes in the near‐UV circular dichroism of δ‐crystallin (which is α‐helical, as opposed to the β‐sheet structure of α‐, β‐, and ‐γ‐crystallins), isolated from chicken lenses, are remarkably different from other crystallins. Irradiation of δ‐crystallin leads to a drastic reduction of circular dichroism intensity in the 250–300 nm region, whereas no changes are seen in the peptide absorption band.
A NEW METHOD TO PREPARE BLUE MEMBRANE BY REMOVING THE CATIONS FROM THE PURPLE MEMBRANE BY ELECTROLYSIS
Authors: Liu Su‐Yi , Ebrey T. G.
Published: January 2008

The purple membrane of Halobacterium halobium will change to the blue membrane when the cations bound to the membrane are removed. Here we introduce a new method to remove the cations by applying a moderate potential (20 V) between two platinum electrodes in a chamber containing a purple membrane solution. The purple membrane is deposited on the anode where the cations are removed by the low pH near this electrode due to the electrolysis of water. The blue membrane made by this method seems identical with blue membrane made by other methods but it can be made more quickly and in large quantities.
THE STRUCTURE OF THE ACTIVE MATERIAL IN HEMATOPORPHYRIN DERIVATIVE
Authors: Byrne C.J. , Marshallsay L.V. , Ward A.D.
Published: January 2008

Abstract The structure of the active material in hematoporphyrin derivative is shown to be a condensation polymer of hematoporphyrin linked by ether functional groups. When a mixture of the monoacetates and the diacetate of hematoporphyrin is treated with dilute sodium hydroxide solution a polymeric fraction is formed which constitutes the active material of hematoporphyrin derivative. This fraction is stable to basic hydrolysis using conditions which are shown to hydrolyse porphyrin esters, but is hydrolysed by acidic conditions which cleave porphyrin ethers as well as esters. When hematoporphyrin diacetate is similarly treated with base a polymeric fraction is formed which is hydrolysed by both acidic and basic conditions showing it to be ester linked. This ester linked polymer is unstable in aqueous solution at pH 7 and converts to the polyether within 2 days at room temperature.
THE ROLE OF SINGLET OXYGEN IN THE PHOTOHEMOLYSIS OF RED BLOOD CELLS SENSITIZED BY PHTHALOCYANINE SULFONATES
Authors: Sonoda M. , Krishna C. Murali , Riesz P.
Published: January 2008

Abstract The post‐illumination photohemolysis of human red blood cells was used as a model system for studying membrane damage sensitized by various phthalocyanine sulfonates. With a constant fluence and photolysis time at 670 ± 10 nm and with a fixed optical density of the sensitizer, the percentage of hemolysis was measured as a function of time after illumination; and from the usual sigmoidal shaped curves, the times for 50% hemolysis were determined. The most effective central cation was Al, followed by Zn; the metal‐free compound and those containing the paramagnetic ions Cu, Fe and Co were inactive. The sensitizer bound to the red blood cells was found to be effective for photohemolysis. Studies of the Al compound in 98.0% deuterated media (as measured by NMR) showed a definite deuterium isotope effect, suggesting the participation of singlet oxygen. This result was supported by the large protective effects of 3.3 raM and 13.3 mM tryptophan present during photolysis. Tryptophan reacts rapidly with singlet oxygen and with OH radicals. The much smaller effects observed with the same concentrations of mannitol and glycerol, OH radical scavengers which do not react with singlet oxygen, are consistent with the predominant role of singlet oxygen in photohemolysis sensitized by Al phthalocyanine sulfonate.
MICROTUBULE ASSEMBLY INHIBITION BY PORPHYRINS and RELATED COMPOUNDS
Authors: Boekelheide Kim , Eveleth Julia , Tatum Arthur H. , Winkelman James W.
Published: January 2008

Abstract Administration of meso‐tetra(4‐sulfonatophenyI)porphine (TPPS4) to rats resulted in cyto‐skeletal abnormalities with loss of microtubules in unmyelinated peripheral nerve axons (Winkelman and Collins, 1987). That in vivo toxic effect prompted the present in vitro study of microtubule assembly inhibition by porphyrins and related compounds. Several approaches were used to measure microtubule assembly inhibition including: (1) determination of the final optical density at 350 nm, (2) analysis of supernatant unassembled tubulin by direct measurement and by colchicine binding, and (3) ultrastructural examination for the presence of typical microtubule profiles. Of the 11 compounds studied, TPPS4, two less sulfonated TPPS congeners and me.so‐tetra(N′‐methyl‐4‐pyridyl)porphine caused profound microtubule assembly inhibition. Afoo‐tetra(4‐carboxyphenyl)porphinc produced an intermediate level of microtubule assembly inhibition. The remaining compounds, including hemato‐porphyrin D (HpD), had little or no effect upon microtubule assembly. In phytohemagglutinin stimulated lymphocytes, nonphotoactivated TPPS4 produced metaphase arrest to the same extent as colcemid. Thus, the specific interaction of TPPS4 with tubulin produces microtubule assembly inhibition in vitro and metaphase arrest in cell culture. Tubulin binding could explain the intracellular concentration of TPPS4 and TPPS‐like compounds, and differences in the biological behavior of these from other porphyrins.
QUANTITATIVE ANALYSIS OF INTRACELLULAR BEHAVIOUR OF PORPHYRINS
Authors: Bottiroli Giovanni , Ramponi Roberta , Croce Anna Cleta
Published: January 2008

Abstract Fluorometric analysis performed on L 1210 cells after treatment with Photofrin indicated that the interactions with cellular structures induce a significant modification of the equilibria among the different porphyrin species. This modification turned out to be dependent on the uptake and release processes. Thus, a comparative analysis of the dynamic aspects of the drug accumulation process was performed on cells treated with hematoporphyrin, Photofrin and Photofrin II. The results obtained were interpreted taking into account the different chemical composition of the drugs employed. The porphyrin species mainly released seem to be the monomeric ones and ‘unfolded oligomers’. The release process results in further modifications of the aggregation and/or configu‐rational state of intracellular porphyrins due to altered internal equilibrium.
DIHEMATOPORPHYRIN ETHER‐PHOSPHOLIPID INTERACTIONS. THE ROLES OF SURFACE CHARGE and LATERAL PHASE SEPARATIONS
Authors: Kendrick Sandra E. , Persky James , Eckhauser Marc L. , Imbembo Anthony L. , Fleischmann Jonathan D. , Koehler Karl A.
Published: January 2008

Abstract Fluorescence spectroscopy was utilized to investigate the equilibrium interaction of dihem‐atoporphyrin ether(s) (DHE) with binary and ternary phospholipid mixtures of defined composition in order to define the roles of net negative surface charge and lateral phase separations in DHE‐membrane partitioning. Binary phospholipid mixtures employed were composed of dimyristoyl‐phosphatidylcholine (DMPC) mixed with increasing weight percentages of dimyristoylphosphatidylgly‐cerol (DMPG) providing controlled variation of net membrane surface charge. Two types of ternary phospholipid mixtures were utilized. Ternary acid mixtures contained various percentages of palmitoyl‐lysophosphatidyl choline (LPC) + palmitic acid (PA) dispersed in DMPC. Ternary alcohol mixtures contained various percentages of LPC + hexadecanol (OL) dispersed in DMPC. The ternary phospholipid mixtures are known to be phase separated. At total DHE concentrations of 0.33 μA/ and using 100% DMPC, the DHE partition coefficient (P) is 250 000. This partition coefficient is to some extent dependent on the DHE concentration. The observed partition coefficients show little dependence on surface charge in DMPC‐DMPG mixtures. However, P decreases markedly with increasing phase separation in the ternary lipid mixtures. The fluorescence of membrane‐bound DHE is dependent on the composition of the ternary mixtures in a manner suggesting micropartitioning of DHE into the phospholipid bulk phase as well as into the disordered regions between laterally phase separated phospholipid domains.
ULTRASTRUCTURAL STUDIES ON THE MECHANISM OF THE PHOTODYNAMIC THERAPY OF TUMORS
Authors: Milanesi Carla , Biolo Roberta , Reddi Elena , Jori Giuuo
Published: January 2008

Abstract Balb/c mice bearing a transplanted MS‐2 fibrosarcoma were injected with 2.5 mg kg 1 of either tetra(4‐sulfonatophenyl/porphine (TPPS) in phosphate‐buffered saline or 0.5 mg kg−1 of Zn2+‐phthalocyanine (Zn‐Pc) incorporated into unilamellar liposomes of dipalmitoyl‐phosphatidylcholine. Chromatographic studies showed that TPPS is mainly transported in the serum by globulins and albumin, while Zn‐Pc is specifically bound by lipoproteins. Exposure of the injected mice to red light (300 J cm−2) caused extensive tumor necrosis. The ultrastructural analysis of tumor specimens taken from mice at 15 h after PDT showed that TPPS photoinduces a preferential necrosis of the neoplastic cells, while Zn‐Pc causes severe photodamage to both the vascular system and the neoplastic cells. The different modes of tumor photosensitization by TPPS and Zn‐Pc are discussed on the basis of the transport mechanism of the two dyes.
HEMATOPORPHYRIN DERIVATIVE UPTAKE BY ATHEROMA IN ATHEROSCLEROTIC RABBITS: THE SPECTRA OF FLUORESCENCE FROM HEMATOPORPHYRIN DERIVATIVE DEMONSTRATED BY AN EXCIMER DYE LASER
Authors: Okunaka Tetsuya , Kato Harubumi , Aizawa Katsuo , Ohtani Takuzo , Kawabe Hirofumi , Asahara Takayuki , Nakajima Hitoshi , Yamasawa Ikuhiro , Ibukiyama Chiharu , O'Hata Susumu , Hayata Yoshihiro
Published: January 2008

Abstract A new diagnostic and therapeutic endoscopic system consisting of an excimer pulse dye laser is presented. This report demonstrates the accumulation of hematoporphyrin derivative (HpD) in atheroma as shown by the fluorescence of HpD using this equipment. Atheroma was induced in the aorta of WHHL (Watanabe heritable hyperlipidemic) rabbits, 5 mg kg−1 HpD was injected intravenously and the rabbits were sacrificed 24 h later. The aorta was dissected and the localization of HpD was examined. Characteristic peaks of the fluorescence of HpD at 630, 665 and 690 nm wavelength were detected in the atheromatous lesion. However, in the fatty plaque, the emission peak at 630 nm was lower and the 665 nm peak faded away. No fluorescence with peaks was detected in the normal area. The ratio of fluorescence intensity in atheroma, border zones and normal areas was 10.4 : 5.0 : 1.0. On normal rabbits made atherosclerotic by diet and balloon damage, an ultra thin endoscopic catheter was inserted from the descending aorta of atherosclerotic rabbits under anesthesia. Essentially the same data was obtained by these studies in vivo as was obtained in the in vitro studies. The above data suggests the possibility of future applications of this equipment for diagnosis of atheroma.
DRUG and LIGHT DOSE DEPENDENCE OF PHOTODYNAMIC THERAPY: A STUDY OF TUMOR and NORMAL TISSUE RESPONSE
Authors: Fingar Victor H. , Henderson Barbara W.
Published: January 2008

Abstract It is clinically relevant to determine drug and light dose combinations where complete tumor response is accompanied by little or no photosensitivity, and minimal damage to normal tissues. Although reciprocity of RIF tumor cell clonogenicity has been established within a range of drug and light doses, no quantitative data exist for reciprocity of tumor response. This study has examined reciprocity of drug and light doses for tumor response and normal tissue damage in two experimental mouse models. Representative tumors were examined for vascular damage after treatment. Reciprocity of drug and light doses for tumor response was observed over a range of drug/light combinations in both tumor models. Reciprocity failed when drug dose was reduced below a threshold value. For reciprocal drug/light combinations, complete vascular stasis occurred in the tumor and surrounding skin which was followed by necrosis of those tissues. In non‐reciprocal PDT combinations, there was vascular damage to the tumor but no damage to the surrounding normal tissues. Tumors responded initially, but no cure was obtained. Tumor cure was only observed under conditions where a considerable margin of normal tissue surrounding the tumor was damaged. This conclusion was supported by shielding experiments done to assess the contribution of normal tissue damage to tumor response. Reciprocity of drug and light doses for tumor response was therefore shown to exist only at high drug doses, which were not low enough to reduce skin photosensitivity in our models.
PORPHYRIN‐LIPID INTERACTIONS AT THE AIR‐WATER INTERFACE IN SPREAD MONOLAYERS. A FLUORESCENCE STUDY.
Authors: Bohorquez Maria , Patterson Larry K. , Brault Daniel
Published: January 2008

In membrane systems, carboxylic porphyrins may interact with both the lipid pseudophase and the adjacent aqueous environment through their hydrophobic core and their polar acid chains, respectively. These interactions are monitored in model membrane systems, i.e. spread monolayers of dioleoylphosphatidylcholine as functions of lipid organization and pH of the aqueous subphase using steady state and time resolved fluorescence techniques. In all cases contact between porphyrin and aqueous subphase, as indicated through quenching by I‐, is observed at low surface pressure. This contact decreases and becomes almost insignificant as the monolayer approaches maximum organization through compression. On deprotonation of the monocarboxylic porphyrin, methylpyrroporphyrin, increased contact with water is observed in liquid compressed monolayers. In liquid expanded layers, however, it appears that organization of lipid molecules surrounding this dissymmetric charged form affords some isolation from water. The effect of esterification of carboxylic chains is also examined.
AN INEXPENSIVE STIRRING DEVICE FOR THE ‘MERRY‐GO‐ROUND’ PHOTOREACTOR FOR THE DETERMINATION OF REACTION QUANTUM YIELDS
Authors: De Silva A. Prasanna , Silva S. Sisira K. de , Edwin V. , Ramyalal N. L. D. Sydney , Silva M. Lalith K.
Published: January 2008

A simple bar magnet is employed to effect stirring of the contents of reaction cells in a‘merry‐go‐round’photoreactor.
PURIFICATION and ANALYSIS OF HEMATOPORPHYRIN and HEMATOPORPHYRIN DERIVATIVE BY GEL EXCLUSION and REVERSE‐PHASE CHROMATOGRAPHY*
Authors: Kessel David , Thompson Paul
Published: January 2008

A ternary‐solvent HPLC method for analysis of the components of the tumor‐localizing product HPD is described. This HPLC system was used to assess the utility of a new method, based on gel exclusion chromatography, for purification of hematoporphyrin.
LASER FLASH SPECTROSCOPY OF METHYLENE BLUE WITH NUCLEIC ACIDS
Authors: Kelly John M. , van der Putten Wilhelm J. M. , Mcconnell David J.
Published: January 2008

Absorption spectra, fluorescence spectra and quantum yields, triplet state absorption spectra, yields and rates of decay have been obtained for methylene blue (MB+), MB+/CT‐DNA complexes and complexes of MB+ with the synthetic polynucleotides poly[d(G‐C)] and poly[d(A‐T)]. Strong fluorescence quenching is observed in the complexes of the dye with CT‐DNA and poly[d(G‐C)] concomitant with a decrease in the triplet yield. The fluorescence and triplet yield of MB+ with poly[d(A‐T)] are similar to those of the free dye. The triplet decay times are increased in all three polymer/dye complexes and show a decreased sensitivity to oxygen quenching. These results are interpreted in terms of the binding of the dye to these polymers and the implications of polymer binding on the photosensitizing properties of the dye are discussed.
CORRELATION BETWEEN THE TRIPLET PHOTOPHYSICAL PROPERTIES AND THE PHOTOBIOLOGICAL ACTION IN YEAST OF TWO MONOFUNCTIONAL PYRIDOPSORALENS
Authors: Ronfard‐Haret J. C. , Averbeck D. , Bensasson R. V. , Bisagni E. , Land E. J. , Moron J.
Published: January 2008

The photophysical properties of the lowest excited triplet states of pyrido[3,4‐c]psoralen (PyPs) and 7‐methylpyrido[3,4‐c]psoralen (MePyPs) have been investigated by laser flash photolysis, including energy transfer from these triplets to oxygen‐generating singlet oxygen. A parallel study of the photosensitization of yeast in vivo by these compounds in the presence and absence of oxygen is also reported. The low triplet and hence singlet oxygen yields, reflected in the lack of an oxygen effect in yeast, suggest that photoadditions to DNA are likely to be the main source of the photosensitized lethal effects induced by these pyridopsoralens in vivo.
RATE CONSTANTS FOR INTERACTION OF 1O21Δg) WITH AZIDE ION IN WATER
Authors: Haag Werner R. , Mill Theodore
Published: January 2008

Abstract— The rate constant for quenching of 1O2 by azide ion in water was determined to be (5.0 ± 0.4) × 108M−1 s−1 using a variety of sensitizers (including humic acids) and 1O2 acceptors. The apparent second‐order rate constant decreases with pH below pH 5.5 in accordance with the protonation of azide ion to form hydrazoic acid (pKa= 4.6). Quenching by hydrazoic acid is at least 2 orders of magnitude slower than by azide ion. Greater than 99% of all interactions between 1O2 and azide ion involve physical quenching rather than chemical reaction. Humic acid triplets are not significantly quenched by azide ion at concentrations less than 2 mM, allowing azide ion quenching to be used as a diagnostic test for the intermediacy of 1O2 in photosensitized oxidations in natural surface waters.
PHOTOREVERSAL OF ABNORMAL MORPHOGENESIS IN SEA‐URCHIN EMBRYOS CAUSED BY UV‐IRRADIATION
Authors: Akimoto Yoshihiro , Shiroya Tsugio
Published: January 2008

Abstract— Morphological abnormalities induced by UV‐irradiation of 8‐ or 16‐cell‐stage embryos of the sea‐urchin, Hemicentrotus pulchenimus, and their photoreversal were studied. UV‐irradiation of the animal hemisphere of embryos caused the formation of exogastrulae, while that of the vegetal hemisphere caused the formation of permanent blastulae. These UV‐induced morphological abnormalities were photoreversed when the UV‐irradiated embryos were subsequently illuminated with visible light, so that the UV‐irradiated embryos developed into normal pluteus‐larvae. When UV‐irradiated embryos were illuminated with visible light up to the onset of the DNA‐synthesis phase of the following cell cycle, the UV‐induced morphological abnormalities were photoreversed almost completely. The effectiveness of an exposure to visible light declined thereafter and was subsequently completely lost.
OXYGEN EFFECT IN SURVIVAL OF Dictyostelium discoideum TREATED WITH NEAR ULTRAVIOLET RADIATION
Authors: Graetzer R.
Published: January 2008

Abstract— Fluence‐response survival curves have been measured for the cellular slime mold Dictyostelium discoideum exposed to near ultraviolet radiation. Data were obtained for a wild type strain and three UV‐sensitive mutant strains in exponential growth phase. Fluences for 10% survival (F10) are about 1 MJ m−2 for cells irradiated in saline solution saturated with nitrogen. When air is bubbled through the saline, the Fm values are only one third as large. Strain HPS50, which is the strain most sensitive to gamma radiation and to 254 nm UV, also exhibits the greatest sensitivity to near UV. However, the difference in sensitivity to near UV between wild type and mutant strains is small compared to other physical and chemical agents known to damage DNA.