bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDONUCLEOLYTIC INCISION OF UVB‐IRRADIATED DNA
Authors: Weiss Randi B. , Duker Nahum J.
Published: January 2008

Abstract. Ultraviolet irradiation of DNA produces a variety of pyrimidine damage. In addition to the well‐known photoproducts, pyrimidine dimers and 6‐4′(pyrimidin‐2'one)pyrimidines, DNA sequence analysis has shown that E. coli endonuclease III incises broad‐spectrum UV‐irradiated DNA at cytosines. The same enzyme incises DNA oxidized by osmium tetroxide at damaged thymines. The wavelength dependence of endonuclease III incision of irradiated DNA was examined. DNA substrates were irradiated by monochromatic light ranging from 250 to 320 nm. Maximal enzymic cleavage was obtained with substrates irradiated by wavelengths between 265 and 285 nm, with peak activity against DNA irradiated at 280 nm. Therefore, these photoproducts are optimally formed at biologically significant wavelengths and may be involved in actinic carcinogenesis.
THE EFFECT OF NORFLURAZON ON PHOTOTROPIC REACTION IN Phaseolus aureus Roxb. SEEDLINGS
Authors: Konjevic Radomir , Grubišić Dragouub , Nešković Mirjana
Published: January 2008

Abstract. The phototropic response of norflurazon‐treated mung bean seedlings has been studied to evaluate the possible role of carotenoids, carotenoid‐derived growth substances, or other factors in the perception/reaction system. Phototropism was slowed significantly in plants grown in white and blue light in the presence of norflurazon. This effect was evident in norflurazon‐bleached seedlings, as well as in those whose pigment system was not affected, due to a shorter period of herbicide action. The possible modes of norflurazon action are discussed.
NITROUS ACID REACTIVATION OF ULTRAVIOLET‐IRRADIATED DENATURED TRANSFORMING DNA
Authors: Cabrera‐Juarez Emiliano , González‐Dadda Lucina
Published: January 2008

Abstract— Partial recovery of ultraviolet‐damaged denatured transforming DNA from Haemophilus influenzae, was obtained by exposing irradiated denatured DNA to nitrous acid and assaying transforming activity. This reactivation was affected by the time of incubation with nitrous acid.
CHANGES IN cAMP AND cGMP CONCENTRATION, BIREFRINGENT FIBRILS AND CONTRACTILE ACTIVITY ACCOMPANYING UV AND BLUE LIGHT PHOTOAVOIDANCE IN PLASMODIA OF AN ALBINO STRAIN OF Physarum polycephalum
Authors: Ueda Tetsuo , Mori Yoshthito , Nakagaki Toshiyuki , Kobatake Yonosuke
Published: January 2008

Abstract— Photoavoidance by plasmodia of an albino strain of Physarum polycephalum was studied. When the organism was irradiated locally, the protoplasm moved away from the irradiated region. The action spectrum for this avoidance showed three peaks at about 260, 370 and 460 nm. The organism was about one hundred times as sensitive to far UV as to near UV and blue light, and high intensity far‐UV caused the gelation of the protoplasm. Irradiation with UV or blue light increased the mean level or the amplitude of oscillation in intracellular cAMP and cGMP concentrations. Upon UV irradiation, birefringent fibrils, presumably microfilaments of F‐actin, became thick and numerous, and the plasmodial strand generated a strong tensile force. It is postulated that UV or blue light brings about an increased concentration of cyclic nucleotides which leads to an enhanced local development of contractile fibrils which squeeze protoplasmic sol from the area, resulting in photoavoidance.
PHOTOINDUCED DEGRADATION AND MODIFICATION OF PHOTOFRIN II IN CELLS in vitro
Authors: Moan Johan , Rimington Claude , Malik Zvi
Published: January 2008

Abstract—Human cells of the line NHIK 3025 were incubated with Photofrin II (PII) and exposed to light. Fluorescence‐ and absorption spectra of PII in the cells were measured. Light exposure resulted in a degradation of PII in the cells and changes in the shape of the fluorescence spectra. These changes are probably partly due to a photochemical modification of PII and to a relocalization of PII in the cells. Notably, a destruction of binding sites for PII on or close to proteins was caused by the light exposure. The rate of the light‐induced decay of the porphyrin fluorescence intensity was only slightly increasing with the PII concentration, indicating that each porphyrin molecule is mainly degraded by photoproducts originating from itself. On the other hand, the rate of the degradation of porphyrin binding sites on the proteins increased with increasing PII concentrations.

The excitation spectrum of PII in cells has a peak at285–290 nm attributed to energy transfer from proteins to porphyrins located close to the proteins. The intensity of this peak relative to the intensity of the Soret band increases with decreasing porphyrin concentrations. This might indicate that some of the binding sites close to proteins have a higher affinity for the porphyrin than binding sites at longer distances from the proteins.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES‐X. SYNTHESES AND ANALYSES OF SULFONATED PHTHALOCYANINES
Authors: Ali Hasrat , Langlois Réjean , Wagner J. Richard , Brasseur Nicole , Paquette Benoit , VAN Lier Johan E.
Published: January 2008

Abstract— Synthetic methods to obtain selectively sulfonated metallo phthalocyanines are compared. Both condensation and direct sulfonation procedures lead to mixtures of mono‐ to tetrasulfonated products which are resolved by reverse phase liquid chromatography in buffered aqueous‐methanol. The proportion of sulfonated derivatives is examined as a function of the starting reagents in the case of the condensation method, and as a function of the temperature and reaction time in the case of the direct sulfonation procedure. The number of sulfonate groups per phthalocyanine molecule is determined by oxidative degradation of the phthalocyanine ring followed by quantitative chromatographic analysis of the sulfophthalamide and phthalamide fragments.
ELECTRON TRANSFER REACTIONS OCCURRING UPON LASER FLASH PHOTOLYSIS OF PHOSPHOLIPID BILAYER SYSTEMS CONTAINING CHLOROPHYLL, BENZOQUINONE AND CYTOCHROMEc‐II. ELECTRICALLY NEUTRAL AND POSITIVELY‐CHARGED VESICLES*
Authors: Fang Yifei , Tollin Gordon
Published: January 2008

Abstract—The primary and secondary electron transfer reactions which occurred upon laser flash photolysis of electrically neutral and positively‐charged lipid bilayer vesicles containing chlorophyll, benzoquinone and cytochromecwere determined by time‐resolved difference spectral and kinetic measurements, and compared with previous results obtained with negatively‐charged vesicles (Y. Fang and G. Tollin,Photochem. Photobiol. 1988). The extent to which oxidized cytochromeccould function as an electron acceptor from triplet state chlorophyll, and reduced cytochromeccould act as an electron donor to chlorophyll cation radical, decreased from negatively‐charged to electrically neutral to positively‐charged vesicles, in agreement with expectations based on changes in the ability of cytochromecto bind to the bilayer. In all three types of vesicles, cytochromecreduction by benzoquinone anion radical occurred in the aqueous phase.
PHOTOCHEMISTRY OF 4‐THIOURIDINE AND THYMINE
Authors: Peak Meyrick J. , Midden W. Robert , Babasick David M. , Haugen David A.
Published: January 2008

Abstract— When thymine is irradiated in aqueous solution with monochromatic 334‐nm UV radiation in the presence of 4‐thiouridine a photoproduct of thymine is formed, as shown by thin‐layer chromatography and autoradiography. The quantum yield for the formation of thymine photoproduct (θ=0.017) is greater than that for cytosine photoproduct formation (θ= 0.0015). The identity of the photoproduct is not known: one possibility is the formation of an adduct between the sensitizer and the base yielding a pyrimidine‐pyrimidone type of photoproduct.
PHOTOCHEMISTRY and PHOTOBIOLOGY WITHOUT LIGHT
Authors: Cilento Giuseppe , Adam Waldemar
Published: January 2008

Abstract—This review covers the literature since 1980 on chemically and enzymatically generated electronically excited species. The emphasis lies on triplet states of carbonyl products that are derived from dioxetanes and dioxetanones as precursors or from suitable enzymatic oxygenations. Singlet oxygen, an important excited state species in biological processes, is not explicitly treated. The utilization of triplet excited carbonyl products to promote photochemical and photobiological transformations by energy transfer are of primordial interest and not the photomechanistic behavior, photophysical properties and inherent photochemical reactions of such excited state species. Thus, the coverage concentrates on photodamage of DNA and RNA, the photochemistry of flavins, vitamin D, tryptophan, arachidonic acid, chlorophyll, lipid peroxidation, urocanase activation, excitation of chlorophlasts, and the aerobic oxidation of Schiff bases derived from amino acids and proteins. The potential perspectives of employing authentic dioxetanes and enzymatically generated dioxetane intermediates as effective photon equivalents in photochemotherapy, phototoxicity, photoaffinity labeling and photogenotoxicity are pointed out, in the hope of stimulating more intensive activity in this emerging and novel bioorganic and photobiological field.
THE EFFECT OF LIPOSOMES' MEMBRANE COMPOSITION ON THE BINDING OF THE PHOTOSENSITIZERS HPD AND PHOTOFRIN II
Authors: Ehrenberg Benjamin , Gross Eitan
Published: January 2008

Abstract—Photofrin II (PF‐II) is the commercial name of the active photosensitizer which is used in photodynamic therapy of cancer. The effect of the composition of lipid membranes on the binding of PF‐II was studied and compared to hematoporphyrin derivative (Hpd), which is a complex mixture of porphyrins and from which PF‐II is separated. We find that increasing the content of cholesterol in the bilayer decreases the partitioning of PF‐II into the bilayer, similar to what we have found earlier with Hpd. However, inserting DMPC or DPPC into the membrane, which was shown to decrease the binding of Hpd, causes the opposite trend with PF‐H. A membrane fluidizer such as benzyl alcohol also has different effects on the membrane binding of Hpd and PF‐II. The rate of binding of PF‐II to a lipid membrane is about 10 times lower than that of Hpd. These results as well as I‐quenching of the fluorescence of the two porphyrins indicate that PF‐II is immersed less homogeneously and deeper in the bilayer than Hpd. The unique additive‐dependent binding of PF‐II to lipid membranes calls for care in using Hpd as a model photosensitizer.
A NEW BIOLOGICAL TARGET OF FUROCOUMARINS: PHOTOCHEMICAL FORMATION OF COVALENT ADDUCTS WITH UNSATURATED FATTY ACIDS
Authors: Specht Kathleen G. , Kittler Leonhard , Midden W. Robert
Published: January 2008

Abstract— Furocoumarins, potent skin therapy and tanning agents, form covalent adducts in a photochemical reaction with unsaturated fatty acids. These adducts and the chemical kinetics of their formation have been characterized by chromatography, isotopic tracers, electronic absorbance and fluorescence spectroscopy and mass spectrometry. Adduct formation does not require oxygen. The quantum yield of adduct formation in ethanol or methanol‐water solutions is comparable to the quantum yield for formation of furocoumarin‐thymine adducts in DNA.
SPECTROSCOPY AND FLUORESCENCE QUENCHING OF TYROSINE IN LIMA BEAN TRYPSIN/CHYMOTRYPSIN INHIBITOR AND MODEL PEPTIDES
Authors: Liu Xiao‐Yuan , Cottrell Kazuo O. , Nordlund Thomas M.
Published: January 2008

Abstract— The effects of citrate ion concentration and pH on the optical spectra and fiuoresence decay have been measured for several tyrosine model compounds and lima bean trypsin/chymotrypsin inhibitor, a protein containing one tyrosine at position 69 and seven disulfides but no tryptophan, in order to determine the location and environment of Tyr 69. Tyrosine in the protein is protected from citrate collisional quenching, as indicated by the dynamic quenching constant 9 to 15 times smaller than those for the model peptides. Static quenching remains, with a Stern‐Volmer constant of about 1.0 M‐1 somewhat smaller than those of L‐tyrosine, tyrosine‐glutamate, and leucine‐tyrosine‐leucine. The elevated pKa of Tyr 69, 11.6, also indicates protein protection from solvent ions. Though Coulomb repulsion of the Glu 70/citrate pair may play a role in the shielding of Tyr 69 from citrate, our measurements indicate that steric effects of the protein structure are more important. Tyrosinate emission in the protein at neutral pH is minimal.
WAVELENGTH DEPENDENCE OF HISTOLOGICAL, PHYSICAL, AND VISIBLE CHANGES IN CHRONICALLY UV‐IRRADIATED HAIRLESS MOUSE SKIN*
Authors: Bissett Donald L. , P.Hannon Daniel , Orr T. V.
Published: January 2008

Abstract— Albino hairless mice (Skh:HR–1) exposed chronically to sub‐erythemal doses of UV radiation display physical, visible and histological alterations. Using narrow bandwidth radiation covering the UV radiation spectrum from280–380 nm, the wavelength dependence of these alterations was determined. The wavelength dependence spectra indicate that for all but one parameter measured (skin sagging), UV‐B radiation is considerably more efficient than UV‐A radiation in producing changes in the skin. However, in natural sunlight there is considerably more UV‐A than UV‐B radiation, providing the potential for UV‐A to have a larger contribution to skin damage than UV‐B. This argues in favor of using broad spectrum photoprotective agents to shield the skin adequately from UV‐induced aging. The spectra were also used to develop potential associations among events by determining which events occur at similar wavelengths. There seems to be a correspondence between mouse visible skin wrinkling (UV‐B event) and two histological events: increase in glycosami‐noglycans and alteration in collagen. There was no obvious correspondence among UV‐A‐induced events.
HYPOCRELLIN‐A SENSITIZED PHOTOOXIDATION OF BILIRUBIN
Authors: Ma Jin‐Shi , Yan Fang , Wang Chang‐Qi , An Jing‐Yi
Published: January 2008

Abstract— Hypocrellin A (HA) extracted from Hypocrellia batnbusae (b.et Br.) sace, a derivative of 3,10‐dihydroxy‐4,9‐perylenequinone, is a highly effective photosensitizer. Kinetic studies of the HA‐sensitized photooxidation of bilirubin IXα (BR) in different solvents in the presence of various active oxygen quenchers indicate that in aprotic solvents the photooxidation goes via a Type II (1O2) mechanism, whereas in alkaline protic solvents Type I (electron transfer from an excited state of HA to the ground state of oxygen or the BR substrate). Type II and probably free radical reactions may occur simultaneously.
ON THE MECHANISM OF PHOTOSYSTEM II DETERIORATION BY UV‐B IRRADIATION
Authors: RENGER G. , VÖLKER M. , ECKERT H. J. , FROMME R. , HOHM‐VEIT S. , GRÄBER P.
Published: January 2008

AbstractThe influence of UV‐B irradiation on photosystem II activities has been investigated using isolated photosystem II membrane fragments from spinach. It was found: (a) The average amount of DCIP reduced per flash declined drastically with increasing irradiation time in the absence of DPC but remained almost unaffected in its presence, (b) After UV‐B irradiation, the maximum amplitude of laser flash induced 830 nm absorption changes decreases only slightly; whereas the relaxation kinetics exhibit marked effects: the (JLS components dominate the decay at the expense of ns components. The γ.s kinetics already arise after illumination with a single flash of dark adapted samples, (c) The manganese content decreases only partly at irradiation times where the oxygen evolution capacity is almost completely lost, (d) The polypeptide pattern is hardly affected; the number of atrazine binding sites markedly decreases. Based on the results of this study, UV‐B irradiation is inferred to deteriorate primarily the function of water oxidation. The action spectrum of the UV‐B effect does not reveal a specific target molecule. It is assumed that structural changes of the D‐l/D‐2 polypeptide matrix are responsible for the modification by UV‐B irradiation of the capacity of water oxidation and atrazine binding.
THE TIME COURSE OF CUTANEOUS PORPHYRIN PHOTOSENSITIZATION IN THE MURINE EAR
Authors: BELLNIER DAVID A. , DOUGHERTY T. J.
Published: January 2008

Abstract This study was designed to investigate the time course of acute cutaneous photosensitivity following administration of Photofrin II using the murine ear swelling response (ESR) as an in vivo end‐point. Ros:(ICR) mice were injected with 5 mg/kg Photofrin II and illuminated 7.5 h to 31 days later with 630‐nm laser light; ESR was measured 24 h after illumination. There was a direct correlation between ESR and the concentration of [14C]Photofrin II in blood, while no relationship between ESR and the level of [14C]Photofrin II in the ear tissue of exsanguinated mice was evident. Photosensitivity in the mouse foot can be suppressed by preexposure to low doses of light via a photochemical destruction of tissue‐bound sensitizer (Boyle and Potter, 1987, Photochem. Photobiol. 46, 997–1001). However, mouse ears pretreated with 84 J/cm2 of 630‐nm light (28 J/cm2/day, given 2, 4 and 6 d after injection), a dose sufficient to reduce porphyrin fluorescence in ear tissue by about 75%, prior to the usual light dose (88.6 J/cm2, 630 nm, day 9 after injection) showed a mean ESR not significantly different (P > 0.5) from that for ears which received only a single dose of 88.6 J/cm2 on day 9. It is concluded, for this animal model, that circulating porphyrin is the source of photoinduced ear‐tissue edema and that photobleaching of tissue‐bound sensitizer does not attenuate ear‐tissue photosensitivity.
ULTRAVIOLET RADIATION ‐ INDUCED MALIGNANT MELANOMA IN Monodelphis domestica
Authors: D. Ley Ronald , A. Applegate Lee , Padilla R. Steven , D. Stuart Thomas
Published: January 2008

Abstract—

Several lines of evidence support the hypothesis that ultraviolet radiation (UVR) is involved in the etiology of cutaneous melanoma in humans. However, progress in understanding the mechanisms involved in induction of melanotic tumors by UVR has been hindered by lack of a suitable animal model. During the course of multiple exposures (3 times/wk for 70 wk) of the South American opossum, Monodelphis domestica, to UVR, we first observed the appearance of areas of dermal melanocytic hyperplasia (MH) on the exposed skin. Post‐UVR exposure to photoreactivating light (320–500 nm) suppressed the occurrence of MH. We also observed at 100 weeks from first exposure that 10 of 46 surviving animals had developed melanotic tumors which arose, presumably, from areas of MH. Tumors on three of the 10 animals have been classified as malignant melanomas based on metastasis to lymph nodes. We conclude from these results that UVR can act as a complete carcinogen for melanoma induction and, based on the photoreactivation of MH induction, that DNA damage is involved in melanoma formation.
PHOTOSENSITIZED OXIDATION OF BIOMATERIALS and RELATED MODEL COMPOUNDS
Authors: Davila Jorge , Harriman Anthony
Published: January 2008

Abstract—

Aluminium trisulfonatophthalocyanine (AIPCS), a dye being widely advocated for use in photodynamic therapy, produces singlet oxygen with a quantum yield of 0.34 in oxygenated water at pH 7. Triplet A1PCS abstracts an electron from a variety of amines and phenols, the rate of electron transfer depending upon the thermodynamic driving force, forming the AIPCS radical anion. This latter species reduces molecular oxygen to superoxide ions with high efficiency. The triplet state also abstracts an electron from biological components, including NADH, vitamin C, cysteine, methionine, tyrosine, tryptophan, uracil, and guanine, but not from DNA. These results suggest that photoinduced electron abstraction from appropriate biomaterials could compete with singlet oxygen production under in vivo conditions.
TRIPLET STATE OF METALLOPORPHYCENES: ZnPCl, PdPC2, PtPC2, and NiPC2
Authors: Toporowicz Moshe , Ofir Hanna , Levanon Haim , Vogel Emanuel , Koucher Matthias , Pramod Kakumanu , Fessenden Richard W.
Published: January 2008

Abstract—

We report on a study of the photoexcited triplet state, at low temperatures in ordered liquid crystals, and at room temperatures in the liquid phase, of some new metalloporphycenes: normal zincporphycene, ZnPCl; Pd(II), and Ni(II) complexes of 2,7,12,17‐tetra‐n‐propylporphycene, PdPC2, PtPC2, and NiPC2, respectively. The triplet state at low temperature is obtained by selective laser excitation and its magnetization response is detected by EPR in the 250 ns time scale. From triplet EPR line shapes and triplet spin polarization directions it is concluded that the zinc cation lies above the molecular plane and the palladium cation fits into the porphycene's cavity. Such a proposed structure implies a strong spin‐orbit interaction in PdPC2, thus resulting in an out‐of‐plane active spin state (z‐axis), whereas that in ZnPCl, having a smaller spin‐orbit interaction, in‐plane (x,y‐axes) are the active spin states. Laser photolysis of the metalloporphycenes gives rise to detectable triplets of ZnPCl, PdPC2 and PtPC2 with triplet lifetimes of 26, 5 and 0.2 µs, respectively. The sensitization experiment, using β‐acetonaphthone as a sensitizer to produce the triplet, results in detectable transients of only ZnPCl and PdPC2 with much longer triplet lifetimes of 85 and 20 µs, respectively. The short triplet lifetime of PtPC2 (and probably that of NiPC2) do not allow for triplet detection with the present sensitizer. However, the latter two metalloporphycenes quench the triplet lifetime of β‐acetonaphthone from 29 to 10µs.
PHOTOCONTROL OF ANTHOCYANIN SYNTHESIS IN TOMATO SEEDLINGS: A GENETIC APPROACH*
Authors: Adamse Paulien , Peters Janny L. , Jaspers Patricia A. P. M. , Tuinen Ageeth VAN , Koornneef Maarten , Kendrick Richard E.
Published: January 2008

Abstract—

The photocontrol of anthocyanin synthesis in dark‐grown seedlings of tomato (Lycopersicon esculentum Mill.) has been studied in an aurea (au) mutant which is deficient in the labile type of phytochrome, a high pigment (hp) mutant which has the wild‐type level of phytochrome and the double mutant au/hp, as well as the wild type. The hp mutant demonstrates phytochrome control of anthocyanin synthesis in response to a single red light (RL) pulse, whereas there is no measurable response in the wild type and au mutant. After pretreatment with 12 h blue light (BL) the phytochrome regulation of anthocyanin synthesis is 10‐fold higher in the hp mutant than in the wild type, whilst no anthocyanin is detectable in the au mutant, thus suggesting that it is the labile pool of phytochrome which regulates anthocyanin synthesis. The au/hp double mutant exhibits a small (3% of that in the hp mutant) RL/far‐red light (FR)‐reversible regulation of anthocyanin synthesis following a BL pretreatment. It is proposed that the hp mutant is hypersensitive to the FR‐absorbing form of phytochrome (Pfr) and that this (hypersensitivity) establishes response to the low level of Pfl. (below detection limits in phytochrome assays) in the au/hp double mutant.
DETERMINANTS OF PHOTOSENSITIZATION BY PURPURINS
Authors: Kessel David
Published: January 2008

Abstract—

Studies were carried out on two purpurins, NT2 and an analog, Sn.NT2H2. Both are photosensitizers, but the latter is substantially more effective against neoplastic cells in vivo. These hydrophobic dyes can be solubilized via Cremophor EL emulsions. We found both dyes to be approximately equitoxic to murine leukemia L1210 cells in culture, in terms of intracellular concentrations. But uptake of NT2 was 10‐fold less efficient than Sn.NT2H2, i.e. a 10‐fold higher extracellular level of NT2 was needed to produce an equitoxic response. Fluorescence measurements indicate that NT2 partitions to a very hydrophobic intracellular environments; its phototoxicity was related to inhibition of biosynthesis of DNA. In contrast, SN.NT2H2 was accumulated at more hydrophilic loci (the apparent dielectric constant is consistent with a membrane interface) and mediated photodamage at sites of membrane transport.
SINGLET OXYGEN GENERATION OF PORPHYRINS, CHLORINS, AND PHTHALOCYANINES
Authors: Kimel S. , Tromberg B. J. , Roberts W. G. , Berns M. W.
Published: January 2008

Abstract—

The production of singlet oxygen was measured indirectly for three classes of photosensitizers: porphyrins (Photofrin II, TPPS4), chlorins (MACE, DACE), and a phthalocyanine (CASPc). Buffered solutions of sensitizers and singlet oxygen acceptors were irradiated with a CW dye laser and the oxygen depletion was monitored electrochemically with a Clark‐type microelectrode. A comparison of oxygen‐depletion rate constants and quantum efficiencies yields the order of efficiency of the sensitizers: TPPS4> MACE > PII > DACE > CASPc. For singlet oxygen acceptors the order was: furfuryl alcohol > imidazole > tryptophan. CHO cell suspensions were also used as acceptors. Here the order of efficiency (per absorbed photon) was PII > MACE = CASPc. Expressed in terms of oxygen depletion per cell the order was CASPc = PII > MACE. When performing cell clonogenicity studies the order of efficiencies, expressed as percentage cell kill per unit weight of sensitizer, was CASPc > PII > MACE = DACE. The discrepancy between the efficiencies of sensitizers to generate singlet oxygen and their cytotoxicity was explained in terms of photodegradation (for the chlorins), intracellular localization (for PII), and contributions from a Type I mechanism (for CASPc).
EFFECTS OF ORAL RETINOID (VITAMIN A AND ETRETINATE) THERAPY ON PHOTOCARCINOGENESIS IN HAIRLESS MICE
Authors: Kelly Graham E. , D.Meikle William , Sheil A. G. Ross
Published: January 2008

Abstract—

Oral retinoid therapy has been considered for the prevention of skin carcinogenesis in humans, although animal studies have failed to provide any evidence of a protective effect of these drugs in the one‐step photocarcinogenic system. In this study, oral therapy with vitamin A or a synthetic analogue, etretinate, was tested for ability to protect hairless mice(Skh‐hrl) from the development of skin tumours following exposure to broad‐band light(280–700 nm) for 25 weeks. Retinoids were given by gavage 3 times weekly either at low dosage(2000 IU vitamin A or 4 mg etretinate per kg body weight) or high dosage(10 000 IU vitamin A or 20 mg etretinate per kg body weight). None of the retinoid therapies compared to control mice(gavage vehicle only) modified skin tumour production in terms of time to onset of tumours, total tumour yield, or the types of tumours produced.
TWO‐DIMENSIONAL IMAGING OF ULTRA‐WEAK EMISSION FROM INTACT SOYBEAN ROOTS
Authors: Ichimura Teijiro , Hiramatsu Mitsuo , Hirai Nobuyuki , Hayakawa Tsuyoshi
Published: January 2008

Abstract—

Two‐dimensional imaging of photons emitted from soybean roots was achieved with an ultra‐high sensitivity photon‐counting image acquisition system. The detected images reveal that a soybean root itself emits very weak light and photon flux from the growing point of the root is more intense than that from other parts of the roots.
SINGLET MOLECULAR OXYGEN QUENCHING BY SATURATED AND UNSATURATED FATTY‐ACIDS AND BY CHOLESTEROL
Authors: Vever‐Bizet C. , Dellinger M. , Brault D. , Rougee M. , Bensasson R. V.
Published: January 2008

Abstract—

The rate constants of molecular singlet oxygen quenching by saturated and unsaturated fatty‐acids and by cholesterol‐membrane critical components ‐ membrane critical components ‐ have been measured by time resolved detection of the 1270 nm phosphorescence of singlet molecular oxygen [O2(1δg)]. We have determined (i) an increment of 5.7 times 102M‐1s‐1per ‐CH2‐ in C6D6and CD3OD for saturated fatty acids between C4and C20, (ii) an increment of 3 times 104M‐1s‐1per non‐conjugated cu‐double bond for C18unsaturated fatty acids, identical in C6D6and CD3OD, (iii) a lower quenching rate constant by a factor of 2.7 for thetrans‐C16andtrans‐C18as compared to the corresponding cis‐monounsaturated fatty acids, (iv) a rate constant of O2(1δg) quenching by cholesterol of 5.7 times 104M‐ls‐lin benzene. These rate constants are compared to those obtained for other membrane cellular components.
A NEW DOSIMETER FOR ULTRAVIOLET‐B RADIATION
Authors: Wong C. F. , Fleming R. , Carter S. J.
Published: January 2008

Abstract— A type of polycarbonate plastic was found to be sensitive to ultraviolet (UV) radiation. The damage to the material due to UV exposure was revealed by etching in a strong alkaline solution. The latent effect can be retained in the material for a period of at least 30 days. The material was tested for use as a detector of ultraviolet‐B (UV‐B 280–320 nm) radiation.

The response of the detector in the wavelength region between 254 and 365 nm was determined using a set of narrow‐band filters and a 200 W UV xenon‐mercury lamp. The maximum UV effect in the detector was observed at a wavelength of 290 nm. The spectral response curve was found to be similar to the human erythema action spectrum.

The detector may be miniaturized for dosimetric applications. The dose response curve is linear in the region up to an erythemal dose of 300 mJcm−2. Laboratory and field tests showed that the dosimeter response to UV exposure was additive and was independent of dose rate. Further experiments suggested that the dosimeter was stable against changes in temperature and humidity.
THE BIOLOGICAL EFFECTS OF UV‐B ON THE EYE
Authors: Taylor Hugh R.
Published: January 2008

–The adverse effects of ultraviolet‐B (UV‐B) radiation on the eye have been suspected but only recently have they been quantified by epidemiologic studies in humans. These studies became possible as methods to qualify individual ocular UV‐B exposure were developed. A consistent dose‐dependent association between ocular UV‐B exposure and two common types of cataract (cortical and posterior subcapsular) has been shown. Although suggested by experimental studies, at present, evidence does not exist to link UV‐B exposure to senile macular degeneration. Ocular exposure to UV‐B is also associated with several corneal changes, pterygium, climatic droplet keratopathy, and acute photokeratitis (snow blindness). Significant reduction in ocular UV‐B exposure results from the use of eyeglasses and hats.
POLARIZED TIME‐RESOLVED FLUORESCENCE SPECTRA OF PHYCOBILISOMES ISOLATED FROM Tolypothrix tenuis EMBEDDED IN POLY(VINYL ALCOHOL) FILM
Authors: Frackowiak Danuta , Minuro Mamoru , Yamazaki Iwao , Tamai Naoto , Fujita Yoshihiko
Published: January 2008

–Time‐resolved fluorescence spectra in the ps time range were measured on phycobilisome (PBS) embedded in poly(vinyl alcohol) films. The cyanobacterium Tolypothrix tenuis was used as a source of PBS because the pigment composition and the structure of the PBS are well defined. Isotropic PBS in the unstretched film and PBS uniaxially oriented in the stretched film were investigated. Diameters of PBS hemidiscs were oriented parallel to the film‐stretching direction. The time‐resolved fluorescence spectra of the unstretched sample and of the two polarized components in the stretched samples showed several differences in the rise and decay. The delay time, estimated from the time span between the maximum laser pulse and maximal intensity of the phycocyanin and allophycocyanin fluorescence, was much longer than that reported in the aqueous media. This suggests occurrence of a higher thermal deactivation of PBS in polymer film than in aqueous media. The excitation energy transfer from excited phycocrythrin to allophycocyanin was more efficient in the unstretched than in the stretched samples, and it was greater in the parallel polarized component of the stretched sample than in the perpendicular component. The present results are in agreement with a previous suggestion which states that there are two independent pathways of excitation energy transfer in PBS and that there is more than one final emitter of fluorescence. The molecules taking part in various pathways of energy transfer differ in their orientation within PBS.
PHOTOFRIN II UPTAKE BY ATHEROMA IN ATHEROSCLEROTIC RABBITS. FLUORESCENCE AND HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC ANALYSIS ON POST‐MORTEM AORTA
Authors: VEVER‐BIZET C. , L′EPINE Y. , DELETTRE E. , DELLINGER M. , PERONNEAU P. , GAUX J. C. , BRAULT D.
Published: January 2008

Abstract—Atherosclerotic lesions were induced in normal and Watanabe rabbits by atherogenic diet and stripping of aorta endothelium. The rabbits were injected with Photofrin II and sacrificed two days later. Atheromatous aorta as well as normal aorta from control animals were characterized by their fluorescence spectra using front face excitation. Characteristic emission peaks at 631 and 694 nm were displayed at atheromatous plaques. The excitation spectrum shows a strong band at 394 nm and weaker bands at 446, 504, 536 and 574 nm. Although no fluorescence of normal aorta can be seen by visual inspection, emission with a maximum at 626 nm was detected by spectrofluorimetry. Normal phase high performance liquid chromatography analysis of extracts from atheroma and control aorta were also carried out. The specific labelling of atheroma involves mainly protoporphyrin, hematopor‐phyrin and also minor components of Photofrin II which are accumulated. Some other components are accumulated but do not appear to be specifically retained by atheroma.
PHOTO‐CIDNP OF THE AMINO ACIDS
Authors: STOB S. , KAPTEIN R.
Published: January 2008

Abstract

A photochemically induced dynamic nuclear polarisation (photo‐CIDNP) study is presented of the amino acids that are polarisable with a flavin dye. These include derivatives of tryptophan, tyrosine, histidine, methylated lysines and methionine. The influence of pH, concentration and chemical modification on the magnitude of the CIDNP effect has been studied to obtain mechanistic information about the radical pair formation.

The pH and concentration dependence of tyrosine and tryptophan polarisation could be accounted for quantitatively. The CIDNP evidence indicates that hydrogen‐atom abstraction is important in generating radical pairs in the case of histidine and tyrosine, while electron transfer prevails in the case of tryptophan, the methylated lysines and methionine.
MUTATION AND SISTER CHROMATID EXCHANGE INDUCTION IN CHINESE HAMSTER OVARY (CHO) CELLS BY PULSED EXCIMER LASER RADIATION AT 93 nm AND 308 nm AND CONTINUOUS UV RADIATION AT 254 nm
Authors: RASMUSSEN RONALD E. , HAMMER‐WILSON MARIE , BERNS MICHAEL W.
Published: January 2008

Abstract— We compared mutagenesis and sister chromatid exchange (SCE) induction by 193 nm and 308 nm pulsed excimer laser radiation with 254 nm low intensity continuous wave UV light in Chinese hamster ovary (CHO) cells in culture. The 254 nm radiation was most mutagenic of the radiations, in accordance with expectation, and also was most effective in increasing the level of SCEs. The 193 nm radiation was mutagenic at the ouabain resistance locus, but not at the HGPRT locus. However, 193 nm radiation was also strongly cytotoxic at energies producing measurable mutations. This radiation also caused a dose‐related increase in SCEs. Pulsed excimer radiation at 308 nm was mutagenic at both loci, and also increased the incidence of SCEs. Comparison of the ratio of mutants/surviving cells at the D37 after radiation showed similar values for 254 nm and 308 nm at the HGPRT locus, but at the ouabain resistance locus, the ratio for the 308 nm radiation was about 5 times that for 254 nm radiation. These results indicate that some risk for mutagenesis may accompany the use of excimer radiation in the UVA region in therapeutic applications.
LONG WAVE ULTRAVIOLET RADIATION STIMULATES ARACHIDONIC ACID RELEASE AND CYCLOOXYGENASE ACTIVITY IN MAMMALIAN CELLS IN CULTURE
Authors: HANSON DEBRA L. , DELEO VINCENT A.
Published: January 2008

Abstract— Human fibroblasts and mouse C3H 10T1/2 cells in culture were prelabeled with [3H]arachidonic acid and exposed to UVA radiation. Cells released labeled arachidonate metabolites into medium in a dose‐dependent fashion (5–20 J ctrr2). The time course of release appeared biphasic with peak responses occurring immediately and at 2 h post irradiation. Release of radiolabel was oxygen and calcium ion dependent and was inhibited by the addition of phenylglyoxal. indomethacin, and dibucaine to the medium. High performance liquid chromatographic examination of medium extracts revealed UVA stimulation of cyclooxygenase metabolism of [3Hjarachidonic acid and specifically, prostaglandin E2 production by cells in culture. Furthermore, UVA stimulated a dose‐dependent release of membrane incorporated pH]choline from cells in culture. Paper chromatographic analysis of the medium provided evidence that choline release from the membrane was predominantly accompanied by release of phosphorylcholine with some glycerophosphorylcholine suggesting indirectly that the major pathway for UVA‐stimulated arachidonic acid release was via phospholipase C and diacylglycerol lipase enzyme systems.
DETERMINANTS OF PHOTOSENSITIZATION BY MONO‐L‐ASPARTYL CHLORIN e6
Authors: KESSEL DAVID
Published: January 2008

Abstract— The mono‐N‐aspartyl derivative of chlorin e6 (MACE) is a new photosensitizer being examined for use in antineoplastic photodynamic therapy. Studies were carried out to identify unique aspects of MACE localization by murine leukemia L1210 cells in vitro. Octanol/water partitioning studies were used to quantitate the hydrophobicity of MACE and two analogs, chlorin e6 and mesochlorin. Sites of cellular localization of these dyes were probed by fluorescence studies, and by examining loci of photodamage. These studies indicate that MACE, a hydrophilic dye, partitions to cytoplasmic loci. Data obtained with chlorin e6, a more hydrophobic dye, are consistent with binding at both membrane and cytoplasmic sites. A substantially more hydrophobic product, meso‐chlorin, binds primarily to the cell membrane. While the tumor‐localizing porphyrin product HPD binds to plasma LDL < HDL. MACE and CE are predominantly bound to plasma protein and HDL. Patterns of distribution and localization of MACE differ substantially from those observed with HPD and other hydrophobic sensitizers. Phototoxic effects of MACE could not be specifically attributed to membrane or mitochondrial damage.
SUBLIMINAL LIGHT CONTROL OF DARK ADAPTATION KINETICS IN Phycomyces PHOTOTROPISM*
Authors: GALLAND PAUL , CORROCHANO LUIS M. , LIPSON EDWARD D.
Published: January 2008

Abstract— The dark adaptation kinetics of Phycomyces phototropism depend critically on the experimental protocol. When sporangiophores that had been light‐adapted to a fluence rate of 1 W m 2 at 447 nm were exposed to dim unilateral light, the adaptation kinetics showed exponential decay (6 min time constant). However, when light‐adapted sporangiophores were kept for variable intervals in darkness (i.e. in presence of traditional red safelight) and then exposed to dim unilateral test light, the decay kinetics of adaptation were biexponential with a rapid decay during the first minute (1 min time constant), followed by a slow recovery (11 min time constant). Thus, the dim subliminal light given after the sporangiophores had been adapted to 1 W m‐2, was actually perceived, and exerted control over the dark‐adaptation process. The observed acceleration of dark‐adaptation kinetics constitutes a novel light effect of the sporangiophore. At wavelength 383 nm this effect was not observed. Because a β‐carotene lacking mutant, L91 (genotype carB), was unmodified in dark‐adaptation kinetics measured in the presence or absence of subliminal light, it appears that β‐carotene is not involved in the photocontrol of adaptation.
THE C4‐PHOTOCYCLODIMERS OF 4,5',8‐TRIMETHYLPSORALEN(TMP)
Authors: Shim Sang Chul , Lee Sang Sun , Choi Seung Ju
Published: January 2008

Abstract— The photodimerization of 4,5'.8‐trimethylpsoralen(TMP) in dichloromethane solution has been investigated. Three products have been isolated and characterized: (1) a non‐fluorescent homodi‐mer resulting from the C4‐cycloaddition at the pyrone end, with a trans‐anti configuration, (2) a bicyclomer resulting from a double cycloaddition between pyrone and furan moieties, and (3) a fluorescent heterodimer resulting from the C4‐cycloaddition between the furan end of one TMP moiety and the pyrone end of the other, with cis‐syn configuration.
CONFIGURATIONS OF CAROTENOIDS IN THE REACTION CENTER and THE LIGHT‐HARVESTING COMPLEX OF Rhodospirillum rubrum. NATURAL SELECTION OF CAROTENOID CONFIGURATIONS BY PIGMENT PROTEIN COMPLEXES
Authors: Koyama Yasushi , Takatsuka Ichiro , Kanaji Mariko , Tomimoto Koichi , Kito Mariko , Shimamura Toshio , Yamashita Jinpei , Saiki Kayoko , Tsukida Kiyoshi
Published: January 2008

Abstract—Carotenoids extracted from the reaction center (RC), the light‐harvesting complex (LH), and the chromatophore membrane ofRhodospirillum rubrumSI were analyzed by high‐performance liquid chromatography. The chemical structures and the configurations of major components were determined by means of mass, Raman, electronic absorption and1H‐NMR spectroscopy. The results indicated: (1) 15‐cis‐spirilloxanthin is bound to RC; (2) both all‐frans‐spirilloxanthin and aII‐(ran.s‐3,4‐dihydrospirilloxanthin are bound to LH and (3) 13‐cK‐spirilloxanthin is additionally present in the chromatophore membrane. The natural selection of the carotenoid configurations, i.e. 15‐ris by RC andaW‐transby LH, is discussed in relation to the physiological functions and the photophysical properties of isomeric carotenoids.
QUANTITATIVE CONVERSION OF THE (6–4) PHOTOPRODUCT OF TpdC TO ITS DEWAR VALENCE ISOMER UPON EXPOSURE TO SIMULATED SUNLIGHT
Authors: Taylor John‐Stephen , Lu Hwang‐Fun , Kotyk John J.
Published: January 2008

Abstract— It has been found that the (6‐4) photoproduct of thymidylyl‐(3→ 5')‐deoxycytidine (TpdC) is converted quantitatively to a further photoproduct upon exposure to Pyrex‐filtered medium pressure mercury arc light. Infrared UV, FAB MS, 'H NMR, 13C NMR and “P” NMR spectra were obtained for both the (6–4) product and its photolysis product. 'H NMR assignments were made on the basis of proton decoupling and homonuclear shift correlated experiments and 13C NMR assignments were made on the basis of proton‐detected heteronuclear shift correlated experiments. The Dewar pyrimidi‐none structure was assigned to the photolysis product by analysis of the spectral data in comparison to those of the Dewar photoproduct of TpT and other Dewar pyrimidinones. The (6–4) product of TpdC is the second member of the class of (6–4) photoproducts that has been found to photoisomerize to its Dewar valence isomer upon exposure to wavelengths > 280 nm, the first being that of TpT (Taylor and Cohrs. 1987,J. Am. Chem. Soc.109,2834–2835). These results further support the proposal that all members of the (6–4) photoproduct class are converted to their Dewar valence isomers upon exposure to sunlight.
ON THE INTERPRETATION OF ABSORPTION SPECTRA OF LEAVES–I. INTRODUCTION and THE CORRECTION OF LEAF SPECTRA FOR SURFACE REFLECTION
Authors: McClendon John H. , Fukshansky Leonid
Published: January 2008

Abstract—Reflectance and transmittance spectra of leaves and their sum can be corrected to relate only to the light actually entering the leaf, if the reflectance of the epidermal surface is known. The latter is found if the leaf reflectances at several wavelengths near the transmittance minimum in the red are plottedvsthe transmittances of a homogeneous suspension of the native pigment‐proteins at the same chlorophyll content per unit area and at the same wavelengths. With non‐senescent leaves, the relation is linear and the extrapolation of the pigment transmittance to zero gives the value for the surface reflection. Surface reflectance data (both adaxial and abaxial) are given for the leaves of a number of trees and a few herbs, plus examples of the raw and corrected spectra. With normal, glaucous leaves, the adaxial reflectance averaged 4.5% of the incident light (n= 23, range = 3.7 −5.9, standard deviation = 0.4). The reflectances of the abaxial surfaces ranged between 7 and 13% since additional near‐surface reflection occurred at the inside of the epidermis and in the spongy mesophyll. Reflectance and transmittance data demonstrated strong absorption in the epidermis below 480 nm.
THE CONFORMATIONAL STATUS OF A PROTEIN INFLUENCES THE AEROBIC PHOTOLYSIS OF ITS TRYPTOPHAN RESIDUES: MELITTIN, β‐ LACTOGLOBULIN and THE CRYSTALLINS
Authors: Rao S. Chenchal , Rao Ch. Mohan , Balasubramanian D.
Published: January 2008

Abstract— We have studied the aerobic photolysis of the tryptophan residues of the proteins melittin and p‐lactoglobulin when the proteins are in ordered conformations and when they are in randomly coiled states. The results suggest that the conformational status of the protein is a factor that influences the photolysis of the constituent tryptophan residues. This point appears to be of relevance to the photo‐oxidation of the tryptophan residues of the eye lens proteins crystallins.
UV INDUCED (6‐4) PHOTOPRODUCTS ARE DISTRIBUTED DIFFERENTLY THAN CYCLOBUTANE DIMERS IN NUCLEOSOMES
Authors: Gale James M. , Smerdon Michael J.
Published: January 2008

Abstract— We have compared the distributions of two stable UV photoproducts in nucleosome core DNA at the single‐nucleotide level using a T4 polymerase‐exonuclease mapping procedure. The distribution of pyrimidine‐pyrimidone (6‐4) dimers was uncovered by reversing the major UV photo‐product, cis‐syn cyclobutane pyrimidine dimer, with E. coli DNA photolyase and photoreactivating light. Whereas the distribution of total UV photoproducts in nucleosome core DNA forms a striking 10.3 base periodic pattern, the distribution of (6‐4) dimers is much more random throughout the nucleosome core domain. Therefore, histone‐DNA interactions in nucleosomes strongly modulate formation of the major class of UV‐induced photoproducts, while having either a constant effect or no effect on (6‐4) dimer formation.
LONG‐TERM EFFECTS OF A SINGLE DOSE OF ULTRAVIOLET‐B ON ALBINO RABBIT CORNEA–II. DETURGESCENCE and FLUID PUMP ASSESSED in vitro
Authors: Doughty Michael J. , Cullen Anthony P.
Published: January 2008

Abstract— Both eyes of female albino rabbits (1.9 kg;9–10 wk old) were exposed to a single dose of UV‐B (300 ± 9 nm; 0.125 J/cm2 total dose) between 13.30 and 15.00 h. At various time periods thereafter (every 12 h for 3 days, 6, 7, 14, 28, 42, 56, 112, 224 and 336 days post‐irradiation), animals were sacrificed, samples of aqueous humor taken for analysis and stroma‐endothelium preparations obtained from the corneas. Following such threshold irradiation, small increases in aqueous humor tonicity and protein levels were observed. The preparations were mounted in a specular microscope assembly (for measuring the rate and magnitude of corneal deturgesccnce) or between two half chambers (for measuring fluid pump) and equilibrated for 2 h with a CO2‐equilibrated glucose‐adenosine‐glutathione‐supplemented Ringer solution at 37°C and a hydrostatic pressure of 20 cm H2O. After equilibration the stromal thickness showed large variation with large reductions in both the rate and amplitude of deturgescence function observed by 36 h. Large reductions in fluid pump activity were also observed by 36 h. The magnitude of the effects on fluid pump were somewhat greater than the effects on deturgescence. Both functions recovered to pre‐irradiation levels by 112 days post‐irradiation.
TIME RESOLVED SPECTROSCOPIC STUDIES ON THE INTACT HUMAN LENS
Authors: Dillon James , Atherton Stephen J.
Published: January 2008

Abstract— The human lens is continually under photooxidative stress from ambient radiation. In the young lens the major absorbing (between300–400 nm) species is the glucoside of 3‐hydroxy kynurenine. Using time resolved fluorescence spectroscopy on both the isolated compound and the intact human lens, the first excited singlet state of this compound is shown to have fast (ps) decay processes. This would tend to minimize damage to lens constituents because there would be little time for energy transfer into more harmful channels. Thus, this compound appears to act as a protection for the retina. With aging, human lens proteins become yellow with absorptions out to 450 nm. Time resolved diffuse reflectance spectroscopic studies on intact older human lenses showed that excitation (355 nm) resulted in the formation of long lived (microseconds) transient species with an absorption maximum at ca 490 nm. Similar spectra were obtained from two model systems used to explain age related changes in human lens proteins.