bluuebunny/crossref_metadata_2025 huggingface dataset:
EXCITATION OF CHLOROPLASTS IN Euglena gracilis IN THE ABSENCE OF LIGHT
Authors: DE MELLO MARICILDA P. , NASCIMENTO ANA LUCIA T. O. , Bohne Cornelia , CILENTO GIUSEPPE
Published: January 2008

Abstract— Challenging Euglena gracilis—a unicellular microorganism that contains chloroplasts—with phenylacetaldehyde induces malondialdehyde formation, sustained red emission and Hill activity. In chloroplasts, phenylacetaldehyde appears to undergo peroxidase catalyzed oxidation to formic acid and triplet benzaldehyde; the latter or, less likely, a precursor thereof promotes lipid peroxidation. Triplet benzaldehyde and/or the excited species formed in lipid peroxidation transfer energy to the chlorophylls. This explanation also applies to spinach chloroplasts preparations, thus accounting for the previous unexplained observation that phenylacetaldehyde induced sustained red emission and Hill activity. A homogeneous picture is now available regarding the intracellular generation of excited states and concomitant excitation of built‐in structures.
INTRACELLULAR FLUORESCENCE OF PHOTOSENSITIZING PORPHYRINS AT DIFFERENT CONCENTRATIONS OF MITOCHONDRIA
Authors: Schneckenburger Herbert , WUSTROW THOMAS P. U.
Published: January 2008

Abstract—Photofrin II, which contains the most efficient components of hematoporphyrin derivative with regard to tumor phototherapy, was measured fluorometrically in single cells of three squamous cell lines with different mitochondrial concentrations. Using the method of time‐resolved fluorescence microscopy, two components—probably monomeric and dimeric species—were differentiated according to the lifetimes of their excited states. The intensity ratio between these components was found to depend on the concentration of mitochondria. This may be due to a monomerization of those porphyrin molecules which are retained in mitochondrial sites.
MULTIPLE MODES OF PHOTODYNAMIC ACTION BY CERCOSPORIN
Authors: Hartman Philip E. , Dixon Wendy J. , Dahl Thomas A. , Daub Margaret E.
Published: January 2008

Abstract—Cercosporin, one of a number of 4,9‐dihydroxyperylene‐3,10‐quinones synthesized by plant pathogenic fungi, abundantly produces singlet oxygen when illuminated in solution. Singlet oxygen production is substantially decreased and superoxide production is greatly enhanced in the presence of the reducing agents ergothioneine (2‐thiol‐L‐histidine betaine) or urate. Both ergothioneine and urate enhance superoxide production at a rate approximately 25‐fold that elicited by an equimolar amount of methionine, the agent that is traditionally used in such assays. Such ‘switching’ in production of different active oxygen species under different environmental conditions may be of significance in biological processes, in this case host cell killing by the plant pathogen.
MODIFICATION OF ε‐AMINO GROUP OF LYSINES, CHOLESTEROL OXIDATION AND OXIDIZED LIPID‐APOPROTEIN CROSS‐LINK FORMATION BY PORPHYRIN‐PHOTOSENSITIZED OXIDATION OF HUMAN LOW DENSITY LIPOPROTEINS
Authors: Candide C. , Reyftmann J. P. , Santus R. , Mazière J. C. , Morlière P. , Goldstein S.
Published: January 2008

Abstract—When incorporated into LDL, protoporphyrin and the porphyrin mixture constituting the trade mark Photofrin II photosensitize peroxidations of cholesterol and lipids. Not only 5a‐hydroperoxicholesterol, the specific product of cholesterol oxidation by1O2but also the epimeric 6‐hydroperoxicholesterols are produced as shown by HPLC. In addition to malonaldehyde‐like substances, the formation of 4‐hydroxynonenal, a highly reactive and toxic aldehyde resulting from lipid peroxide breakdown is detected. These products are also formed by dark radical chain reactions of lipid photoperoxides induced by photosensitization. The involvement of lipid photoperoxidation in LDL apoprotein modification is demonstrated by following the derivatization of e‐NH2groups of Lys residues which are necessary to binding to the LDL receptor. As a result, photosensitized LDL cannot bind to their receptors on fibroblasts. Lys residues are not sensitive to direct photodynamic reaction as confirmed by delipidation of LDL and solubilization of apoLDL in 1% SDS which totally inhibit Lys derivatization without affecting the degradation of Trp residues susceptible to the photodynamic attack. Another consequence of lipid peroxidation at the protein level is the formation of cross‐links between apoLDL and photooxidized lipids as shown using LDL loaded with radioactive arachidonic acid. On the other hand, cholesterol photoperoxidation does not lead to protein‐oxidized cholesterol cross‐links. These reactions between peroxidized lipids and LDL proteins are also responsible for the formation of lipofuscin‐like fluorescent pigments encountered in all aging processes. The biological and biomedical consequences of these results are discussed.
IMPAIRED REPAIR OF UVC‐INDUCED DNA DAMAGE IN L5178Y‐R CELLS: DNA UNWINDING STUDIES WITH THE USE OF 1‐β‐D‐ARABINOFURANOSYL CYTOSINE
Authors: Szumiel Rena , Wlodek Danuta , Johanson KarlJ.
Published: January 2008

Abstract— L5178Y‐R (LY‐R) and L5178Y‐S (LY‐S) cells differ in sensitivity to UVC radiation (D0: 2.8 and 9.0 J/m2respectively, for cells exposed in Fischer's medium). We used these cells and a DNA unwinding technique in conjunction with 1‐β‐D‐arabinosyl cytosine to determine DNA strand breaks accumulating as a result of enzymatic incision during DNA repair. Following UVC exposure DNA strand break accumulation was observed in LY‐S cells but not in LY‐R cells. The repair defect in LY‐R cells is accompanied by a delayed recovery of [3H]thymidine incorporation.
SPECTRA AND EXTINCTION COEFFICIENTS OF NEAR‐INFRARED ABSORPTION BANDS IN MEMBRANES OF Rhodobacter sphaeroides MUTANTS LACKING LIGHT‐HARVESTING AND REACTION CENTER COMPLEXES
Authors: Sturgis James N. , Hunter C. Neil , Niederman Robert A.
Published: January 2008

Abstract— Membranes from Rhodobacter (formerly Rhodopseudomonas) sphaeroides mutant strains that lack one or more of the bacteriochlorophyll a (BChl)‐protein complexes were used to obtain spectra and molar extinction coefficients of the near‐IR absorption bands. The strains examined were NF57 which lacks the B875 light‐harvesting and reaction center complexes, and M21 which lacks the B800–850light‐harvesting complex. The extinction coefficients obtained for the B800, B850 and B875 bands were 226 ± 10, 170 ± 5, and 118 ± 5 mM‐1cm‐1, respectively, in reasonable agreement with values reported for detergent‐isolated complexes (Clayton, R. K. and B. J. Clayton, Proc. Natl. Acad. Sci. USA78,5583–5587, 1981). The results also demonstrated that detergent solubilization altered the spectra, causing a band broadening on the blue side of the B875 and B800 peaks. The data obtained from the analysis of the mutant strains were used for deconvolution of the BChl species in membranes of the wild‐type. A short BASIC computer program for performing this deconvolution is included.
LIGHT‐INDUCED ELECTRICAL EFFECTS IN A LIQUID CRYSTAL BLM CONTAINING TCNQ
Authors: Salamon Zdzislaw , Tien H. Ti
Published: January 2008

Abstract—The light‐induced capacitance changes and also both photovoltage and photocurrent under continuous illumination have been investigated in pigmented liquid crystal bilayer membranes (PBLM)‡ containing TCNQ as photosensitizer with Na2SO3electron donor on one side and methylene blue electron acceptor on the other side. The results have shown that TCNQ in cyanobiphenyl membrane produces a unique photoactive BLM system in which all three main parameters (conductivity, capacity and voltage across the membrane) are in a wide range altered by the light. It is shown that a TCNQ‐cyanobiphenyl charge transfer complex is responsible for the observed photochanges. The possible mechanism of photoinduced electrical effects in this type of PBLM is discussed.
In vitro PHOTOSENSITIZING PROPERTIES OF RHODAMINE 123 ON DIFFERENT HUMAN TUMOR CELL LINES
Authors: Melloni Elsa , Dasdia Teresa , Fava Giannino , Rocca Emilio , Zunino Franco , Marchesini Renato
Published: January 2008

Abstract—In this study, human tumor cell lines of different origin (colon carcinoma HT29, breast carcinoma MCF7 and malignant melanoma M14) were incubated for 24 h at 37*deg;C with Rhodamine 123 (Rh123) at concentrations ranging up to 4 μg/ml;. Immediately after drug removal, light irradiation was delivered at 500 W/m2for 5 min using an argon laser. After irradiation, viable cells were counted and assayed for colony formation. When only Rh123 was administered, a 50% survival was obtained at about 2.77 μg/ml and 1.48 μg/ml; for HT29 and MCF7, respectively. After light irradiation, 50% survival doses decreased to 0.47 μg/ml and 0.18 μg/ml for the two carcinoma cell lines, respectively. In the case of malignant melanoma, the decrease in survival was relatively lower than those obtained with carcinoma cells: 50% survival dose was 3.54 μg/ml with Rh123 alone and 1.32 μ/ml after irradiation. The lower sensitivity of M14 melanoma cells seems to be related to different uptake and release of drug by these cells with respect to carcinoma lines.
COPPER QUENCHING OF THE VARIABLE FLUORESCENCE IN Dunaliella tertiolecta. NEW EVIDENCE FOR A COPPER INHIBITION EFFECT ON PSII PHOTOCHEMISTRY
Authors: Samson Guy , Claude Morisette Jean , Popovic Radovan
Published: January 2008

Abstract—The copper quenching effect on fluorescence inDunaliella tertiolectawas studied. 30% of variable fluorescence was quenched in the presence of 70 μ,M CuS04. We confirmed that the copper inhibitory effect on photosystem II (PSII) activity is located on its oxidizing side. Further, we indicate that the complementary area is decreased by copper. Since the quantum yield of PSII photochemistry was lowered and the rate of PSII primary electron acceptor QAremained unaffected, we can conclude that some PSII reaction centers were inactivated by copper.
THE VISUAL PROCESS: PHOTOPHYSICS and PHOTOISOMERIZATION OF MODEL VISUAL PIGMENTS and THE PRIMARY REACTION
Authors: Becker Ralph S.
Published: January 2008

Abstract—A systematic comprehensive consideration of the emission spectroscopy, emission lifetimes, transient spectroscopy, as well as quantum yields of fluorescence, triplet occupation and photoisomeriz‐ation is given for a wide variety of polyene derivatives including retinyl and longer, as well as shorter chainlength homologs. Absorption spectral properties and the results and significance of theoretical calculations are also included. Chainlength, solvent and temperature effects on state order and photophysical as well as photoisomerization properties are evaluated. The mechanism for the primary light step in vision is considered in light of photophysical and photoisomerization data on model visual pigments and rhodopsin.
AN ULTRASTRUCTURAL COMPARATIVE EVALUATION OF TUMORS PHOTOSENSITIZED BY PORPHYRINS ADMINISTERED IN AQUEOUS SOLUTION, BOUND TO LIPOSOMES OR TO LIPOPROTEINS
Authors: Zhou Chuannong , Milanesi Carla , Jori Giulio
Published: January 2008

Abstract— Balb/c mice bearing a transplantedMS–2 fibrosarcoma have been injected with 2 mg kg‐1 hematoporphyrin either dissolved in phosphate‐buffered saline (Hp‐aq), or incorporated into unilamellar liposomes of dipalmitoyl‐phosphatidylcholine (Hp‐lip), or precomplexed with low density lipoproteins (Hp‐LDL). At 24 h after injection, the mice received 150 J cm‐2 of600–680 nm light irradiation. Electron microscopic studies performed on tumor tissues taken from mice sacrificed at different times after the phototreatment showed that, in the presence of Hp‐aq. tumor necrosis is largely the consequence of vascular damage. On the other hand, in the presence of Hp‐lip and Hp‐LDL, the response of the tumor to the phototreatment occurs at a faster rate and is mainly determined by direct damage of neoplastic cells. These findings are correlated with the different distribution of the various hematoporphyrin forms (Hp‐aq, Hp‐lip, Hp‐LDL) among the serum proteins and the modalities of hematoporphyrin delivery to tissues by the possible carriers.
DETECTION OF CYCLOBUTANE THYMINE DIMERS IN DNA OF HUMAN CELLS WITH MONOCLONAL ANTIBODIES RAISED AGAINST A THYMINE DIMER‐ CONTAINING TETRANUCLEOTIDE
Authors: Roza Len , van der Wulp Kees J. M. , MacFarlane Sandra J. , M.Lohman Paul H. , Baan Robert A.
Published: January 2008

Abstract— A hybrid cell line (hybridoma) has been isolated after fusion between mouse‐plasmacytoma cells and spleen cells from mice immunized with a thymine dimer‐containing tetranucleotide coupled to a carrier protein. Monoclonal antibodies produced by this hybridoma were characterized by testing the effect of various inhibitors in a competitive enzyme‐linked immunosorbent assay (ELISA). The antibodies have a high specificity for thymine dimers in single‐stranded DNA or poly(dT), but do not bind UV‐irradiated d(TpC)5. Less binding is observed with short thymine dimer‐containing sequences. In vitro treatment of UV‐irradiated DNA with photoreactivating enzyme in the presence of light, or with Micrococcus luteus UV‐endonuclease results in disappearance of antigenicity. Antibody‐binding to DNA isolated from UV‐irradiated human fibroblasts (at 254 nm) is linear with dose. Removal of thymine dimers in these cells during a post‐irradiation incubation, as detected with the antibodies, is fast initially but the rate rapidly decreases (about 50% residual dimers at 20 h after 10 J/m2). The induction of thymine dimers in human skin irradiated with low doses of UV‐B, too, was demonstrated immunochemically, by ELISA as well as by quantitative immunofluorescence microscopy.
PHOTODYNAMIC THERAPY INDUCED ULTRASTRUCTURAL ALTERATIONS IN MICROVASCULATURE OF THE RAT CREMASTER MUSCLE
Authors: Tseng Michael T. , Reed Malcolm W. R. , Ackermann Douglas M. , Schuschke Dale A. , Wieman T. Jeffery , Miller Frederick N.
Published: January 2008

Abstract— Photodynamic therapy disrupts blood flow to tumors and produces tumor necrosis. These effects may be due to a localized generation of singlet oxygen. The current studies used direct observations of the rat cremaster microvasculature to examine the vascular effects of PDT. The objective of the morphological examination was to delineate the structural basis for the altered blood flow in photodynamic therapy. Dihematoporphyrin ether given 30 min or 48 h prior to the experiment was activated with green light (wavelength530–560 nm, 120 J/cm2). After the in vivo activation the tissues were prepared for electron microscopy. Light alone induced little or no change in the luminal content or vessel wall. On exposure to activating light both acute (30 min) and long term (48 h) dihematoporphyrin ether pretreated samples displayed formation of luminal aggregates, granulocyte margination and migration, and endothelial cell and smooth muscle cell damage. The latter was more pronounced in the arterioles than the venules. Perivascular changes included interstitial edema and damage to striated myocytes. Some of the alterations such as interstitial edema may be transient; however, smooth and skeletal muscle cell injury are important in normal and tumor tissue necrosis after photodynamic therapy.
DEPROTONATION DYNAMICS OF LOCAL ANESTHETICS IN HYDROPHOBIC MEDIA: DIBUCAINEHCI IN WATER/ALCOHOL OR SURFACTANT MIXTURES
Authors: Lin C. T. , Williamson L. N. , Chyan Y. G. , Marques A. D. S.
Published: January 2008

Abstract— The emitting chromophores, emitting states, state orderings and phosphorescence lifetimes of neutral, hydrogen‐bonded, and protonated dibucaines in water/alcohol mixtures were determined experimentally and were confirmed theoretically using a HAM/3 method. These photophysical properties are used to probe the deprotonation dynamics of dibucaine‐HCl in the water/hydrophobic media. It is found that the protonated dibucaine in an aqueous solution is deprotonated and/or forms hydrogen‐bonded dibucaine when it is brought into contact with the alcohols and surfactants. The observed deprotonation processes could lend some insight on the molecular basis of pharmacological action of dibucaine.
PHOTOLYTIC REARRANGEMENT OF METRONIDAZOLE TO 1‐HYDROXYETHYL‐2‐METHYL‐4‐HYDROXYIMINO‐5‐OXO‐IMIDAZOLE AND THE FORMATION OF COPPER COMPLEXES OF THESE COMPOUNDS
Authors: Wilkins Brian J. , Moore Douglas E.
Published: January 2008

Abstract— A labile intermediate in the photolytic rearrangement of the antibacterial drug, metronidazole, was identified by isolating the product of photolysis of metronidazole benzoate in methanol. The intermediate, 1‐hydroxyethyl‐2‐methyl‐4‐hydroxyimino‐5‐oxo‐imidazole, was shown to act as a bidentate chelating agent for copper(II) ions, whereas metronidazole forms a weak monodentate complex. The intermediate may be relevant to the bioactivation mechanism of metronidazole.
HYDROXYSTILBAZOLES AND HYDROXYAZAPHENANTHRENES: PHOTOCYCLIZATION AND FLUORESCENCE STUDIES
Authors: Haroutounian Serkos A. , Katzenellenbogen John A.
Published: January 2008

Abstract— As models for novel fluorescent probes, we have synthesized three isomeric hydroxystilbazole systems (4′‐hydroxy‐substituted 2‐, 3‐, and 4‐stiIbazoles), examined their photocyclization‐oxi‐dation to four hydroxyazaphenanthrene systems, and made a preliminary study of their absorption and fluorescence spectra. All three stilbazoles can be prepared easily by addition of the isomeric picoline anions to 4‐methoxybenzaldehyde, followed by dehydration and deprotection. Photocyclization proceeds efficiently, furnishing a single product isomer from each of the 2‐ and 4‐stilbazole systems, and two isomeric azaphenanthrenes from the 3‐stilbazole. The stilbazoles all have intense UV absorbance bands whose maxima depend upon solvent and pH; all three isomers have relatively similar spectra under neutral conditions and all three show a large red shift in base; in acid, however, the 2‐and 4‐stilbazole isomers show a greater red shift than the 3‐stilbazole. The fluorescence of the stilbazoles is also solvent dependent, shifting to the red in more polar medium; red shifts are also observed in acid and base, but in acid, the 3‐stilbazole shows a larger shift. The azaphenanthrene photocyclization products show absorbance spectra typical for quinolines and isoquinolines; their absorptivities are less than the stilbazoles, but their fluorescence is more intense. In general, the benzoquinolines have longer wavelength but weaker fluorescence than the benzoisoquinolines. Also, those isomers in which the resonance effects of the hydroxy and nitrogen groups can reinforce one another show longer wavelength emissions of greater intensity. All seven systems show dual fluorescence in water under neutral conditions, suggesting the emission from both non‐ionized and ionized species in the excited state. In one case, the benzoisoquinoline system derived from 4′‐hydroxy‐4‐stilbazole, an emission at 640 nm, observed in water over a wide pH range, is ascribed to a zwitterionic phototautomer. These stilbazoles, benzoquinolines and benzoisoquinolines may prove to be useful spectroscopic probes.
CONCENTRATION‐DEPENDENT LIFETIMES OF Cu(NN)+2 SYSTEMS: EXCIPLEX QUENCHING FROM THE ION PAIR STATE
Authors: Everly R. Michael , McMillin David R.
Published: January 2008

Abstract— The concentration dependence of the lifetimes of the charge transfer excited states of Cu(dmp)+2 and Cu(dpp) +2 has been investigated in CH2C12 solution at 20°C. (dmp denotes 2,9‐dimethyf‐1,10‐phenanthroline, and dpp denotes 2,9‐diphenyl‐l,10‐phenanthroline.) In dilute solution (< 30 μM) the lifetime of Cu(dmp)+2, is 95 ± 5 ns, independent of the anion. At higher concentrations the lifetime decreases, in most cases, to a limiting value that depends upon the counterion. The measured limiting lifetimes range from 38 ± 3 ns for CIO‐4 to 78 ± 5 ns for PF‐6. The anion‐induced quenching is attributed to exciplex quenching which is mediated by an ion pair which exists in the ground state. The results imply that the quenching ability of the anions follows the order BPh‐4 < PF ‐6, < BF‐4 < CIO ‐4 < NO‐3 which is consistent with previous estimates of donor strength. The lifetime of Cu(dpp)+2 is also concentration dependent, but the effect is much smaller because the phenyl substituents impede attack by the anion.
A COMPARISON OF SERUM KINETICS AND TISSUE DISTRIBUTION OF PHOTOFRIN II FOLLOWING INTRAVENOUS AND INTRAPERITONEAL INJECTION IN THE MOUSE
Authors: PANTELIDES M. L. , MOORE J. V. , BLACKLOCK N. J.
Published: January 2008

Abstract Although hematoporphyrin derivative (HPD) and its ‘purers’ variety Photofrin II are the most widely used tissue sensitizers in both clinical and experimental photodynamic therapy (PDT), quantitative studies of tissue distribution have been few. We have extracted and measured Photofrin II in several organs of the normal mouse including those of relevance to urological practice. In view of the reported heterogeneities in the distribution within tissues of various cytotoxics when administered intraperitoneally. we have compared results for Photofrin II given by this route with those for intravenous injection. Although both routes of administration gave equally consistent results, differences in absolute tissue concentration as a function of time after injection were found for several but not all tissues. Furthermore, the porphyrin accumulated following intravenous administration seemed to contain more of the non‐polar photodynamically active component than that accumulated following the intraperitoneal route. We attempt to explain these differences by reference to published data on porphyrin binding to serum proteins.
DEPENDENCY OF PHOTON DENSITY ON PRIMARY PROCESS OF CATTLE RHODOPSIN
Authors: KANDORI HIDEKI , MATUOKA SINZI , SHICHIDA YOSHINORI , YOSHIZAWA TÔCRU
Published: January 2008

AbstractThe primary photochemical reactions of cattle rhodopsin suspended in H2O or D2O were compared between excitation with both a weak and an intense picosecond laser pulse (wavelength, 532 nm; duration, 25 ps) at room temperature. The time‐dependent change of bsorbance at about 575 nm demonstrated that photorhodopsin, a precursor of bathorhodopsin, was produced immediately after the excitation with a weak picosecond laser pulse. It decayed to bathorhodopsin with a time constant of 45 ps which is close to the value reported previously [Shichidaet al., (1984)Photobiochem. Photobiophys., 7, 221–228]. No deuterium effect was observed in this process. Excitation with an intense laser pulse induced instantaneous increase of the absorbance at about 575 nm and remained at almost constant level on the picosecond time scale, which was in good agreement with the pioneering work [Buschet al., (1972)Proc. Natl. Acad. Sci., USA, 69, 2802–2806], No deuterium effect was observed in this photochemical process.
INHIBITION OF THE IMMUNE RESPONSE TO ALLOANTIGEN IN THE RAT BY EXPOSURE TO ULTRAVIOLET RADIATION
Authors: Magee Mitchell J. , Kripke Margaret L. , Ullrich Stephen E.
Published: January 2008

Abstract—

Exposure of mice to ultraviolet radiation (UV) followed by alloantigcn sensitization can suppress the immune response to that alloantigen. In order to assess the applicability of using UV‐induced immunosuppression in organ transplantation, the effectiveness of UV in prolonging the survival of vascularized organ allografts must be determined. Because, for technical reasons, rats are better suited than mice for such experiments, we first wanted to determine whether UV suppresses the immune response of inbred rats to alloantigens. The data presented here demonstrate that exposure of rats to UV (115–129 kJ/m2) prior to alloantigenic sensitization decreases the mixed lymphocyte response to alloantigen. The depression of the proliferative response to alloantigen was selective in that spleen cells from the UV‐treated rats could respond to mitogenic stimulation. In contrast to previous results with mice, suppressor cells could not be demonstrated in the spleens of the UV‐treated rats. In addition, UV treatment after sensitization inhibited the response to alloantigen. These data suggest that treatment of the recipient with UV before or after alloantigenic sensitization may provide a novel method of inhibiting immune responses to allogeneic antigens.
LOCAL SUPPRESSION OF CONTACT HYPERSENSITIVITY IN MICE BY A MONOFUNCTIONAL PSORALEN PLUS UVA RADIATION
Authors: Alcalay Joseph , Ullrich Stephen E. , Kripke Margaret L.
Published: January 2008

Abstract—

Monofunctional psoralens, plus UVA radiation are not erythemogenic and are less mutagenic than bifunctional psoralens plus UVA radiation. Thus, they have received considerable attention in recent years as potential therapeutic agents for various skin diseases. The purpose of this study was to examine the immunologic side effects following treatment of mice with a monofunctional psoralen plus UVA radiation. We report that angelicin plus UVA radiation suppressed the induction of contact hypersensitivity to dinitrofluorobenzene. This decreased immune response was associated with the presence of splenic suppressor cells that transferred suppression to normal recipients. Treatment with angelicin and UVA radiation also decreased the number of Thy‐1+ and Ia+ dendritic epidermal cells in the treated site. We conclude that although this monofunctional psoralen is not phototoxic, it has immunosuppressive activity in mice.
ELICITATION OF SPREADING DEPRESSION BY ROSE BENGAL PHOTODYNAMIC ACTION
Authors: Netto Marialia , Martins‐Ferreira Hiss
Published: January 2008

Abstract—

Spreading depression refers to a slowly propagating depression of the ordinary electrical activity of the nervous tissue. It can be elicited by different types of physical or chemical non‐specific stimuli. Various evidences suggest that transient alterations of cell membranes are involved. For this reason, and considering the action of free radicals on cell membranes, the elicitation of the reaction by dye photoactivation has been investigated. Isolated chick retina superfused in the dark with Ringer solution was able to regularly exhibit spreading depression when submitted to 1 µ,M rose bengal pulse of 5 min in duration, followed by 2.1 104 to 4.2 times 104 Jm‐2 light pulse. The phenomenon was monitored either by visual inspection of the light‐scattering milky wave that accompanies the reaction or by recording its characteristic slow voltage variation. The reaction was not triggered if the retina, superfused with the dye, was (a) maintained in the dark; (b) illuminated with red light (3.75 times 102 to 2.25 times 104 Jm‐2), or (c) stimulated by white light but superfused with nitrogen‐saturated solutions. It is concluded that, under the present conditions, the elicitation of spreading depression is contingent on the photoactivation of rose bengal in the presence of oxygen.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS‐XIV. THE SPIN TRAPPING OF FREE RADICALS FORMED DURING THE PHOTOLYSIS OF HALOGENATED SALICYLANILIDE ANTIBACTERIAL AGENTS
Authors: Chignell Colin F. , Sik Robert H.
Published: January 2008

Abstract—

Several antibacterial halogenated salicylanilides, including 3,3′,4′,5‐tetrachlorosalicylanilide (TCSA) and 3,4′,5‐tribromosalicylanilide (TBSA) are known to cause photoallergy. We have carried out photochemical and spin trapping studies to determine whether free radicals may be involved in the photoallergic response. Irradiation (λ > 300 nm) of TCSA in buffered (pH 7.4) 50% ethanol resulted in the rapid loss of the 3‐chloro atom, followed by the much slower release of 5‐ and then the 4′‐chloro atoms to give 3′‐chlorosalicylanilide as a stable photoproduct. Under the same conditions TBSA successively lost the 3‐, 5‐ and 4′‐bromine atoms to give salicylanilide. When TCSA or TBSA were irradiated (λ= 356 nm) in buffered (pH 7.4) 50% ethanol containing 2‐methyl‐2‐nitrosopropane (MNP) only solvent‐derived free radicals were detected. However, irradiation (λ= 356 nm) of TCSA and MNP in 0.1 N NaOH generated an ESR spectrum consisting of a broad triplet (aN= 15.6 G).This spectrum was attributed to the adduct formed by the reaction of MNP with the aryl radical generated by the loss of a chlorine atom from the sterically hindered 3‐(or 4′‐)‐position. Under the same conditions TBSA initially generated a broad triplet (aN= 15.5 G) similar to that observed for TCSA. However, upon further irradiation a 21‐line spectrum (aN= 14.4 G, a2H= 2.0 G and a2H= 0.9 G) appeared. Since the same ESR spectrum was obtained by irradiating 4′‐bromosalicylanilide, the spectrum must be generated by an adduct formed by reaction of MNP with an aryl radical derived from loss of the 4′‐bromine atom of TBSA. Irradiation (λ= 356 nm) of TBSA, glutathione and the spin trap 5,5‐dirrrethyl‐l‐pyrroline‐N‐oxide (DMPO) yielded the glutathione thiyl adduct of DMPO. Irradiation of (λ= 356 nm) TCSA, MNP and glycylglycine resulted in the trapping of a carbon‐centered radical derived from hydrogen abstraction from the backbone methylene of the C‐terminal glycine residue. These studies demonstrate that photo‐irradiation of TCSA or TBSA generates highly reactive aryl radicals, which can react with peptides to form secondary radicals. Thein vivoreaction of secondary protein radicals with the primary aryl radicals from TCSA or TBSA would result in the covalent binding of the salicylanilides to skin proteins to give molecules with antigenic potential.
USE OF CHARGE COUPLED DEVICE CAMERA FOR IMAGING OF INTRACELLULAR PHTHALOCYANINES
Authors: Chan W.‐S. , MacRobert A. J. , Phillips D. , Hart I. R.
Published: January 2008

Abstract— A highly sensitive charge‐coupled device (CCD) camera, linked to a computerized image processor, has been used to obtain fluorescence images of chloro‐aluminum sulfonated phthalocyanine (ClAlSPc), and its mono‐ to tetra‐sulfonated constituents, in cells recovered from the peritoneal cavity of dye‐treated mice. Immunofluorescence and cytochemistry showed that cells which preferentially took up ClAlSPc and its sulfonated species were predominantly of the monocyte‐macrophage series. While this technique may be of use in determining the nature of those cells capable of taking up light sensitive dyes and, perhaps, the intracellular location of such agents, the possibility that photoinactiv‐ation by dye aggregation could reduce the sensitivity of this procedure is discussed.
In vivo PHOTODEGRADATION OF CHLORPROMAZINE
Authors: Schoonderwoerd S. A. , Henegouwen G. M. J. Beijersbergen Van , Belkum S. Van
Published: January 2008

Abstract— The in vivo photodegradation of chlorpromazine (CPZ) in the skin was investigated after systemic administration of 3H‐CPZ to shaven Wistar rats and exposure to UV‐A. Promazine (PZ) and 2‐hydroxy‐promazine (2‐OH‐PZ) appeared to be formed in irradiated rats, but not in the skin of rats kept in the dark. This indicates that upon irradiation with UV‐A the PZ‐radical is formed which can be held responsible for the photobinding to eye and skin constituents as observed earlier [Schoonder‐woerd and Beijersbergen von Henegouwen (1987) Photochem. Photobiol. 46, 501–505]. Chlorpromaz‐ine‐sulfoxide (CPZSO) is a major metabolite of CPZ. Less CPZSO was found in the skin of irradiated rats compared to those kept in the dark. As this appeared not to be caused by photobinding or photodegradation of CPZSO it can be concluded that CPZSO is not a photoproduct of CPZ under these experimental conditions. This study shows that the in vivo photodegradation of CPZ proceeds via the promazinyl radical rather than via the radical cation.
FLOW CYTOMETRIC ANALYSIS OF INTRACELLULAR HEMATOPORPHYRIN DERIVATIVE IN HUMAN TUMOR CELLS AND MULTICELLULAR SPHEROIDS
Authors: West Catharine M. L. , Moore James V.
Published: January 2008

Abstract— Flow cytometry (FCM) has been used to investigate the intracellular fluorescence of hematoporphyrin derivative (HPD) in monolayer and spheroid cultures of WiDr cells. For exponentially‐growing monolayer cultures mean cellular fluorescence was directly proportion to the external HPD levels in the range 5–100 µg ml−1(r = 0.99). Heterogeneity of cellular fluorescence was quantified by determining the ratio of the fluorescence value below which were observed values for 98% of the cell population compared to the fluorescence value for 2%. In exponentially‐growing cultures, decreasing levels of HPD in the medium led to an increase in the 98:2% ratio, i.e. an increase in heterogeneity of intracellular drug levels. The growth of cells as multicellular spheroids confers a spheroid‐size‐dependent resistance to photodynamic treatment. With increasing spheroid size (100, 250, 500, 750 and 1000 µm diam.) there was a decrease in mean intracellular HPD levels and a large linear increase in the 98:2% ratio (r = 0.94).
THE RELATIONSHIP BETWEEN MALIGNANT MELANOMA OF SKIN AND EXPOSURE TO SUNLIGHT
Authors: Lee John A. H.
Published: January 2008

–Malignant melanomas of the skin are becoming more common. Earlier diagnosis has led to better individual prognoses, but this has not prevented the death rate in the population from rising. This paper brings up‐to‐date studies on the etiology of malignant melanoma, and supplements various fuller but earlier reviews.

Melanoma risk is increased in lightly pigmented people who burn in the sun and do not tan well. People with an increased number of nevi are also at increased risk. Latitude of residence is important, risk in white populations increasing with distance from the poles. Phenotypic factors can over‐ride location, so that Mediterranean people have lower rates than Scandinavians. Melanomas are concentrated on sites exposed by clothing, but this concentration is not as strong as for the other skin cancers. Migrants to sunny climates are at less risk than similar people born locally, provided that they migrated as adults. Outdoor work carries only a small excess risk of malignant melanoma, in contrast to the other skin tumors. Melanomas are commoner, and kill more often, among people of high socioeconomic status than low.

The two most detailed contemporary reconciliations of these pieces of evidence are based on the ideas that intense brief exposure is the critical factor, or that exposure in childhood is of major importance.

With the expected changes in the global concentration of ozone in the stratosphere, it is necessary to estimate the relationship between the intensity of sunlight and melanoma risk.
RESOLUTION OF TWO EMISSION SPECTRA FOR TRYPTOPHAN USING FREQUENCY‐DOMAIN PHASE‐MODULATION SPECTRA
Authors: Lakowicz Joseph R. , Jayaweera Ranjith , Szmacinski Henryk , Wiczk Wieslaw
Published: January 2008

–We describe a novel application of frequency‐domain fluorometry which allows resolution of the decay times and emission spectra of samples which display multi‐exponential decay kinetics. This method does not require any previous knowledge about the decay times or any assumptions about the shape of the emission spectra. We record the wavelength‐dependent phase angles and modulations (phase angle and modulation spectra) using a number of light modulation frequencies. The data are analyzed by non‐linear least‐squares to recover the underlying spectra and their associated decay times.

Phase and modulation spectra (PM Spec) were used to recover the emission spectra associated with the two decay times of tryptophan at pH = 7 (0.54 and 3.44 ns). The emission spectra of these components are centered at 340 and 355 nm, respectively, with the amplitude of the 0.54 ns component contributing 6% to the total eirnssion. These results are in agreement with previous time‐resolved studies by Szabo and Rayner [J. Am. Chem. Soc.102, 554–563 (1980)]. Control experiments were performed on mixtures of N‐acetyl‐L‐tryptophanamide (NATA) and PPD, which demonstrate our ability to recover the spectra and decay times from two component mixtures. NATA itself displayed a single decay time and only one emission spectrum.
OPTICAL ABSORPTION AND EMISSION STUDIES ON LASER DYE INCORPORATED IN NAFION MEMBRANE
Authors: MOHAN HARI , MOORTHY P. N. , IYER R. M.
Published: January 2008

Abstract— Incorporation of the laser dye 7‐amino‐4‐methyl coumarin (C‐120) in a perfluoro sulfonate cation exchange membrane (Nafion) from aqueous solution has been studied by following its light absorption and emission (fluorescence) characteristics. It is shown that in the H+ form of the membrane the dye exists in its monoprotonated cationic form, whereas in different cation exchanged forms of the membrane it is incorporated as the unprotonated neutral molecules. By repeated equilibration with the aqueous solution, high concentrations of the dye could be loaded into the membrane. As compared to an aqueous solution, the polymer matrix was found to confer very good photostability to the dye.
PHOTOCHEMICALLY INDUCED BINDING OF Rh(phen)2Cl2+ TO DNA†
Authors: MAHNKEN R. E. , BINA M. , DEIBEL R. M. , LUEBKE K. , MORRISON H.
Published: January 2008

Abstract— The photoinduced covalent binding of the title compound to native and heat denatured DNA is described. The level of binding has been measured by UV (for DNA) and atomic absorption (for Rh) analysis. Quantum efficiencies of 6.4 times 10‐4 mol Rh per mol photons and 1.6 times 10‐3 mol Rh per mol photons have been determined for binding to native and denatured calf thymus DNA, respectively. Levels of bound rhodium as high as 1 molecule per five bases have been achieved. There is no binding of the complex in the absence of light, and there is evidence that at least a portion of the binding may be due to the photolytic conversion of the complex into one or more stable intermediates. Studies with polyribonucleotides indicate a strong preference for binding to the purine bases.
ON THE INTERPRETATION OF ABSORPTION SPECTRA OF LEAVES–II. THE NON‐ABSORBED RAY OF THE SIEVE EFFECT and THE MEAN OPTICAL PATHLENGTH IN THE REMAINDER OF THE LEAF
Authors: McClendon John H. , Fukshansky Leonid
Published: January 2008

Abstract— The sieve effect and scattering within leaves are analysed by the use of a simple model. By plotting the leaf transmittance (corrected for light not entering the leaf) vs the transmittance of an equivalent amount of homogeneous plastid pigments, an intercept is found where the latter is zero. This minimum transmittance represents the fraction of the leaf area devoted to the ray of the sieve effect which strikes no chloroplasts. It varied between 7% and 0.2% in non‐senescent leaves. When this was subtracted from the leaf spectrum, the peak absorbance was greater than that of the homogeneous leaf pigments in all cases. The ratio of the leaf absorbance to that of the homogeneous pigments, at the same wavelength, is the apparent optical pathlength, which increases with decreasing absorbance. By plotting this ratio vs the absorbance of the equivalent homogeneous pigment, an intercept is found where the latter is zero. This intercept is interpreted as an estimate of the true mean scattering pathlength. Leaves with high chlorophyll contents had low pathlengths (mean and SD = 2.30 ± 0.25); with moderate and low contents, the values were higher (2.75 ± 0.28, 3.95 ± 0.77). Another application of the model gave values between 3 and 4 for the true scattering pathlength.
HYDROGEN ABSTRACTION FROM LIPIDS BY TRIPLET STATES OF DERIVATIZED BENZOPHENONE PHOTOSENSITIZERS
Authors: Marković D. Z. , Durand T. , Patterson L. K.
Published: January 2008

Abstract— Laser photolysis techniques have been used to characterize the reactivity of triplet state lipoidal benzophenone derivatives toward fatty acids and glycerides in benzene solution. The reactivities of benzophenone‐4‐heptyl‐4'‐pentanoic acid (BHPA) toward fatty acid compounds having different configurations of olefinic bonds have been determined. The rates of hydrogen abstraction are found to be lower when compared with similar measurements using benzophenone alone. However, the contribution of physical quenching of the triplet derivative by double bonds also appears to be slightly lower than that found with benzophenone itself. The hydrogen abstraction efficiencies of three other benzophenone derivatives toward linoleic acid in benzene have also been measured. For benzophenone incorporated into a fatty acid molecule, there is a limited relationship between structure and photoreac‐tivity. Finally, these sensitizers have been incorporated into mixed SDS/linoleate micelles to determine the effects of molecular organization on photochemical behavior of the sensitizer and lipid.
AGGREGATION OF MONOVINYL‐ and DIVINYL‐PROTOCHLOROPHYLLIDE IN ORGANICSOLVENTS*
Authors: Kotzabasis Klriakos , Senge Mathias , Seyfried Britta , Senger Horst
Published: January 2008

Abstract—Two different protochlorophyllides (PChlide), PChlide 629/433 (absorption data in methanol) and PChlide 630/441 (the monovinyl (MV) and divinyl (DV) forms) were isolated from the pigment mutant C‐2A'ofScenedesmus obliquus.Their spectroscopic behaviour in several organic solvents and their aggregation in toluene was investigated. In polar solvents such as ether, acetonitril or acetone, absorption maxima similar to those in methanol were observed, while in solvents such as tetrahydrofuran and pyridine a bathochromic shift of the blue absorption band compared to the spectra in methanol occurred. The absorption maxima of MV‐PChlide shifted from 629 nm and 433 nm in methanol (monomeric form), to 631 nm and 443 nm in toluene (aggregated form). The absorption maxima of DV‐PChlide shifted from 630 nm and 441 nm in methanol to 655 nm and 483 nm in toluene (aggregated form). The fluorescence excitation and emission spectra of the two protochlorophyllides yielded the according results. The aggregation process was faster for DV‐PChlide than for MV‐PChlide and was reversible upon addition of small amounts of polar solvents. The similarity of the spectral characteristics of the aggregated forms of the different protochlorophyllides after toluene treatment with those reported for “active”‐PChlidein vivoare discussed.
TRANSIENTS OF URACIL and THYMINE DERIVATIVES and THE QUANTUM YIELDS OF ELECTRON EJECTION and INTERSYSTEM CROSSING UPON 20 ns PHOTOLYSIS AT 248 nm
Authors: Görner Helmut
Published: January 2008

Abstract— Transients of uracil and a series of 17 correlated pyrimidines, e.g. methylated bases, nucleosides, nucleotides, and polyuridylic acid [poly(U)] were studied after 248 nm excitation by 20 ns laser pulses. The transient absorption spectra in aqueous solution at room temperature reveal the triplet state and the hydrated electron (e−nq), while the corresponding radical cation could not be observed at pH6–7. Fast loss of the chromophore in the260–290 nm range within 0.1 μs was observed in aqueous solution in some cases [e.g. poly(U), 5'‐UMP, uridine, uracil] and in others (thymine, thymidine) virtually not. This photobleaching is assigned to formation of the photohydrate. The concentration of e−eq shows a quadratic dependence on the laser pulse intensity (I,) in the range (0.2‐2) × 107 W cm −2 and the quantum yield of electron ejection (Φs.‐) thus depends linearly on IL. This behaviour, suggesting that the photoionization involves a two‐step absorption process, was found for poly(U) and all pyrimidine monomers examined. At a constant I, value of 2 × 107 W cm 2, Φe. ranges from 3 × 10 −3 for 1,3‐dimethylthymine to 4 × 10˜2 for poly(U). The triplet state shows a much larger transient absorbance (DTA. typically in a broad range, e.g.290–500 nm) than that of the neutral radical resulting from the radical cation. The triplet state in organic solvents (acetonitrile and ethanol) shows generally a significantly larger DTA value than in aqueous solution. The estimated quantum yields of intersystem crossing at room temperature are compared with those of phosphorescence at ‐196°C.
SINGLE‐ and DOUBLE‐STRAND BREAK FORMATION IN DOUBLE‐STRANDED DNA UPON NANOSECOND LASER‐INDUCED PHOTOIONIZATION
Authors: Bothe Eberhard , Gorner Helmut , Opitz Joachim , Schulte‐Frohlinde Dietrich , Siddiqi Aslam , Wala Malgorzata
Published: January 2008

Abstract—Double‐stranded (ds) calf thymus DNA (0.4 mM), excited by 20 ns laser pulses at 248 nm, was studied in deoxygenated aqueous solution at room temperature and pH 6.7 in the presence of a sodium salt (10 mM). The quantum yields for the formation of hydrated electrons (Φe.), single‐strand breaks (Φssb) and double‐strand breaks (Φdsb) were determined for various laser pulse intensities (I1). Φc. and Φssbincrease linearly with increasing IL; however, Φssbhas a tendency to reach saturation at high IL(Φ5 times 100Wcm−2). The ratio Phi;ssh/Φc‐. representing the number of ssb per radical cation, is about 0.08 at IL5 times 106Wcm−2. For comparison, the number of ssb per OH radical reacting with dsDNA is 0.22. On going from argon to N2O saturation, Φssband Φdsbbecome larger by factors of 5 and10–15, respectively. This enhancement is produced by attack on DNA bases by OH radicals generated by N2O‐scavenging of the photoelectrons. While Φssbis essentially independent of the dose (Etot), Φdsb, depends linearly on Etotin both argon‐ and N2O‐saturated solutions. The linear dependence of Φdsbimplies a square dependence of the number of dsb on Etot. This portion of dsb formation is explained by the occurrence of two random ssb, generated within a critical distance(h)in opposite strands. For both argon‐ and N2O‐saturated solutionshwas found to be of the order of40–70 phosphoric acid diester bonds. On addition of electron scavengers such as 2‐chloroethanoI (or N2O plus t‐butanol), Φdsbis similar to that in neat, argon‐saturated solutions. Thus, hydrated electrons are not involved in the chemical pathway leading to laser‐pulse‐induced dsb of DNA.
CHLORANIL‐PHOTOSENSITIZED MONOMERIZATION OF DIMETHYLTHYMINE CYCLOBUTANE DIMERS and EFFECT OF MAGNESIUM PERCHLORATE
Authors: Pac Chyongjin , Miyamoto Ikuya , Masaki Yasuhiro , Furusho Seiichi , Yanagida Shozo , Ohno Takeshi , Yoshimura Akio
Published: January 2008

Abstract— The photosensitized monomerization of the cyclobutane dimers of 1,3‐dimethylthymine by p‐chloranil was investigated by means of steady‐state irradiation and laser‐flash photolysis. Quantum yields for the monomerization are 0.34 for the cis, syn dimer, 0.39 for the trans, syn dimer, and < 10−2 for the cis, anti isomer. Formation of the chloranil anion radical associated with quenching of triplet chloranil by the dimers demonstrates that electron transfer from dimers to triplet chloranil occurs to initiate the monomerization. Kinetic analysis suggested that the swdimer cation radicals undergo the ring cleavage at 10o s−1 before escaping from the solvent cage, while the reactivity of the anti‐dimer cation radical is very low. The different reactivities of the syn and anti dimer cation radicals are discussed in terms of through‐bond coupling between the n orbitals of N(1) and N(1') involving the cyclobutane‐ring s̀ orbitals. In the cases of the syn‐dimers, the sensitizer‐dimer ion‐radical pairs undergo the rapid geminate recombination that works as a major energy dissipating channel responsible for the lower‐than‐unity quantum yields. It has been found that the presence of Mg(C1O4)2 at 0.1 M enhances 1.5 times either the monomerization of the syn dimers or the formation of the chloranil anion radical. A laser‐flash photolysis study shows that Mg2+ foms a complex with either the triplet or the anion radical of chloranil. The net salt effects are attributed to the retardation of the rapid geminate recombination by the participation of Mg2+ in the sensitizer‐dimer ion‐radical pairs.