bluuebunny/crossref_metadata_2025 huggingface dataset:
LINEAR DICHROISM STUDY OF METALLOPORPHYRIN TRANSITION MOMENTS IN VIEW OF RADIATIONLESS INTERACTIONS WITH TRYPTOPHAN IN HEMOPROTEINS
Authors: Gryczynski Zygmunt , Bucci Enrico , Kuba Joazee:
Published: January 2008

We measured the linear dichroism of several metalloporphyrins embedded in stretched polyvinyl alcohol (PVA) films to estimate the orientation of the absorption transition moments, which in hemoproteins are relevant to the radiationless energy transfer between tryptophan and heme. The metalloporphyrins were derivatives of protoporphyrin IX (PPIX), namely Fe3+‐PPIX (ferric‐heme) and Fe2+CO‐PPIX (CO‐heme), Mg‐PPIX (Mg‐heme) and Zn‐PPIX (Zn‐heme). Measurements were conducted between 300 and 700 nm. In all cases the linear dichroism was wavelength dependent, indicating the presence of several transition moments with different orientations. We focused our attention on the near‐UV (300–380 nm) and Soret (380450 nm) absorption bands. Deconvolution in terms of Gaussian components gave three components between 380 and 450 nm and only one in the 300–380 nm region. Deconvolution of the near‐UV and Soret spectra of oxy‐, deoxy‐ and carbonmonoxyhemoglobin gave very similar results, suggesting a very similar orientation of the various transition moments in the free and protein‐embedded hemes. It should be stressed that the single 300–380 nm band is the only one responsible for the overlap integral that regulates the energy transfer from tryptophan to heme in hemoproteins (Gryczynski et al., Biophys. J. 63, 648–653, 1992). The dichroism of this single band indicated that its transition moment is oriented at about 60 from the α‐γ meso‐axis of the heme moiety. We conclude that the heme should be considered a linear oscillator when it acts as acceptor of energy transfer from tryptophans.
THE EFFECT OF CHANGES OR DIFFERENCES IN ROBERTSON‐BERGER RADIOMETER RESPONSIVITY ON SOLAR ULTRAVIOLET‐B MEASUREMENT
Authors: Smith Gerald J. , Ryan Ken G.
Published: January 2008

Two long‐term solar UV measurement campaigns, in the USA and in Austria, using Robertson‐Berger radiometers found opposite trends for measured levels of ultraviolet‐B radiation reaching the earth's surface. This could be a consequence of the method used to calibrate the radiometers. Changes or differences in responsivity were compensated for by adjusting the sensitivity of the field radiometers to match the output of a reference radiometer.

This radiometer intercomparison procedure has been evaluated in terms of the normalization wavelength to which the Robertson‐Berger effective irradiance refers. There are small differences in spectral responsivities apparent in the radiometers used in the USA campaign, which require the field radiometers to be normalized at different wavelengths to match the response of the reference radiometer. This normalization wavelength is shown to depend on the time‐averaged spectrum experienced by the instruments during the intercomparison. As a result there are substantial interradiometer variations in their calculated response to solar radiation when the measured spectral distribution is different from the spectrum used for the radiometer intercomparison procedure.
FLUORESCENCE LINE‐NARROWING STUDIES OF ANTIBODY‐BENZO[a]PYRENE TETROL COMPLEXES
Authors: Singh Kuldip , Skipper Paul L. , Tannenbaum Steven R. , Dasari Ramachandra R.
Published: January 2008

Benzo[a]pyrene tetrol (BPT) was used as a fluorescent probe to investigate the nature of antigen binding by two different monoclonal antibodies (MAb) that recognize a variety of derivatives of anti‐7,8‐dihydroxy‐9,10‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrenes (BPDE). Fluorescence line‐narrowed spectra of the physical complexes of BPT formed with antibodies 8E11 and 3C3 were recorded at 4 K by employing vibronic excitation into the S, electronic state. The frequencies of the vibrational modes of the S1 state were only marginally affected, though changes in relative intensities of some bands were observed. Fluorescence spectra recorded at 77 K by excitation into the S2 state showed that the (0,0) fluorescence emission of BPT was shifted to red on complex formation. Intensity ratios of the (0,0) band and the main vibrational band at 1300 cm‐1 were used to assess the degree of interior binding of the chromophore. Quenching studies with acrylamide were employed to designate the complexes as type I, solvent inaccessible, or type II, solvent accessible. These studies also indicated that antibody 3C3 complexes tend to be more heterogeneous compared to the 8E11 complex. Deuterated BPT‐d‐12 also formed complexes with both antibodies, however, with different quenching behavior.
RELAXATION OF VASCULAR SMOOTH MUSCLE INDUCED BY LOW‐POWER LASER RADIATION
Authors: Chaudhry Hina , Lynch Mary , Schomacker Kevin , Birngruber Reginald , Gregory Kenton , Kochevar Irene
Published: January 2008

The relaxation of rabbit aorta rings induced by low‐power laser radiation was investigated in vitro to determine the location of the chromophore(s) responsible for this response and evaluate possible mechanisms. An action spectrum for relaxation was measured on rabbit thoracic aorta rings precontracted with norepinephrine. The decrease in isometric tension was measured during exposure to laser light (351–625 nm) delivered via a fiber optic to a small spot on the adventitial surface. The shortest UV wavelength (351 nm) was 35‐fold more effective than 390 nm and 1700‐fold more effective than 460 nm. Ultraviolet wavelengths also produced greater maximum relaxation (0.40–0.45) than visible wavelengths (0.20–0.25), suggesting that photovasorelaxation involves more than one chromophore.

The adventitial layer was not necessary for photovasorelaxation, indicating that the light is absorbed by a chromophore in the medial layer. The same degree of relaxation was obtained on rings without adventitia when either one‐half of the ring, or a small spot was irradiated indicating that communication between smooth muscle cells spreads a signal from the area illuminated to the entire ring.

The mechanism for photovasorelaxation was investigated using potential inhibitors. N‐monomethyl‐l‐arginine and N‐amino‐L‐arginine, inhibitors of nitric oxide synthase, did not alter photovasorelaxation nor did indomethacin, an inhibitor of cyclooxygenase, and zinc protoporphyrin, an inhibitor of heme oxygenase.
AGGREGATION OF 2,3‐DIHYDROXY‐ETIOCHLORIN I. AN AMPHIPHILIC MODEL COMPOUND FOR PHOTODYNAMIC THERAPY AND GREEN HEME d
Authors: Senge Mathias O. , Hope Hakon , Iakovides Panos , Smith Kevin M.
Published: January 2008

The crystal structure of 2,3‐dihydroxy‐etiochlorin I has been determined to obtain information on its aggregation behavior. Cis‐dihydroxychlorins serve as model compounds for green heme d and show promising photonecrotic activity in photodynamic therapy. The compound shows strong aggregation in the solid state facilitated by intramolecular hydrogen bonding between one hydroxy group and pyrrole nitrogens of neighboring molecules. This novel type of aggregation leads to chain‐type aggregates in the crystal. The title compound 4 crystallized in the monoclinic space group Ia (Z = 4) with unit cell dimensions a = 9.902(4) Å, b = 26.430(9) Å, c = 10.823(5), β= 104.47(3) Å, V = 2743(2) Å3. The structure was refined to an R‐value of 0.097 on the basis of 1150 reflections with F > 4.0σ (F) (130 K).
MODULATION OF 8‐METHOXYPSORALEN‐DNA PHOTOADDUCT FORMATION BY CELL DIFFERENTIATION, MITOGENIC STIMULATION AND PHORBOL ESTER EXPOSURE IN MURINE T LYMPHOCYTES
Authors: Tokura Yoshim , Edelson Richard L. , Gasparro Francis P.
Published: January 2008

Abstract The effects of cell differentiation and mitogen and phorbol ester stimulation on the formation of 8‐methoxypsoralen (8‐MOP)‐DNA photoadducts in murine T lymphocytes were examined using 3H‐8‐MOP. While there were no significant differences in 8‐MOP photoadduct formation among BALB/c thymocytes, splenocytes, splenic T cells and MRL/1pr lymph node cells, BALB/c bone marrow cells showed fewer photoadducts than did the lymphocytes. This suggested that proliferating progenitor cells may be resistant to 8‐MOP photoadduct formation. Incubation of purified splenic T cells with lectin mitogens for 2 h or with phorbol 12‐myristate 13‐acetate (PMA) for 2–43 h resulted in reduction of 8‐MOP photoadduct formation in the DNA, whereas 64 h cultivation with these agents augmented the photoadduct formation. The reduction of photoadduct formation induced by phytohemagglutinin was restored by the further addition of a protein kinase C (PKC) inhibitor, H‐7, to the culture. Thus, it is assumed that the reduction of adduct formation evoked by mitogens and PMA is mediated in part by the activation of PKC in the cells. On the other hand, the augmentation of the adduct formation induced by the longer‐period cultures with mitogens and PMA appeared to be caused by down‐regulation of PKC. The present study showed that the stimulatory signals in which PKC is presumably involved affect the ability of cells to form 8‐MOP‐DNA photoadducts.
CHARACTERIZATION OF SKELETAL MUSCLE ACTIN LABELED WITH THE TRIPLET PROBE ERYTHROSIN‐5‐IODOACETAMIDE
Authors: Ludescher Richard D. , Liu Zane
Published: January 2008

Abstract We have labeled rabbit skeletal muscle actin with the triplet probe erythrosin‐5‐iodoacetamide and characterized the labeled protein. Labeling decreased the critical concentration and lowered the intrinsic viscosity of F‐actin filaments; labeled filaments were motile in an in vitro motility assay but were less effective than unlabeled F‐actin in activating myosin S1 ATPase activity. In unpolymerized globular actin (G‐actin), both the prompt and delayed luminescence were red‐shifted from the spectra of the free dye in solution and the fluorescence anisotropy of the label was high (0.356); filament formation red shifted all excitation and emission spectra and increased the fluorescence anisotropy to 0.370. The erythrosin phosphorescence decay was at least biexponential in G‐actin with an average lifetime of 99 μs while in F‐actin the decay was approximately monoexponential with a lifetime of 278 μs. These results suggest that the erythrosin dye was bound at the interface between two actin monomers along the two‐start helix. The steady‐state phosphorescence anisotropy of F‐actin was 0.087 at 20°C and the anisotropy increased to ≈0.16 in immobilized filaments. The phosphorescence anisotropy was also sensitive to binding the physiological ligands phalloidin, cytochalasin B and tropomyosin. This study lays a firm foundation for the use of this triplet probe to study the large‐scale molecular dynamics of F‐actin.
DYNAMIC CAPILLAROSCOPY: A MINIMALLY INVASIVE TECHNIQUE FOR ASSESSING PHOTODYNAMIC EFFECTS in vivo
Authors: Da Silva Fernando A. Menezes , Newman E. Luke
Published: January 2008

Abstract A noninvasive method for visualizing the microvasculature in the mouse tail is described, consisting of a custom‐built microscope with through‐lens illumination. The microscope is fitted with a television camera and images can be recorded on videotape and displayed on a television monitor. Blood vessels are imaged as columns of red blood cells, in which flow is clearly observed. Administration of photosensitizers and illumination with the standard light source produces no observable photodynamic effect on blood flow. The combination of photosensitizer and a more intense light source (either broadband light from a filtered mercury arc or red light from a laser) causes photodynamic cessation of flow within a few minutes. The magnitude of the effect is dependent on the dose and nature of the photosensitizer, the delay after photosensitization and the match between the laser light and the absorption spectra of the photosensitizers in the red region. We conclude that the technique yields results consistent with the known photodynamic effects of the photosensitizers in tumors and propose its use as an initial screening method in YWO, as a means of conducting pharmacokinetic experiments and as an assay of prolonged cutaneous photosensitivity.
EFFECTS OF UV IRRADIATION ON A LIVING SKIN EQUIVALENT
Authors: Nelson D. , Gay R. J.
Published: January 2008

Abstract— The Living Skin Equivalent (LSE™) is an organotypic coculture composed of human dermal fibroblasts interspersed in a collagen‐containing matrix and overlaid with human keratinocytes forming a stratified epidermis. The LSE has a dry, air‐exposed epidermal surface suitable for the application of oils, creams and emulsions. These features suggested its feasibility as an in vitro skin model for studying the protective effects of sunscreens. Using the thiazolyl blue (MTT) conversion assay as a measure of mitochondrial function, the extent of cytotoxicity induced by various doses of UV‐R (280–400 nm) or UV‐A (320–400 nm) was evaluated in the LSE. The doses of UV radiation that caused 50% reductions in MTT conversion (UV‐R50 or UV‐A50) in different lots of LSE were 0.053 ± 0.021 J/cm2 (n = 29) and 11.6 ± 4.9 J/cm2 (n = 17) for UV‐R and UV‐A, respectively. The protective effects of an 8% homosylate standard and of five UV‐A sunscreens, topically applied to the LSE, were determined and compared with their reported protection factors in human skin. Morphological changes and the release of proinflammatory mediators (interleukin‐1‐α, tumor necrosis factor‐α and prostaglandin E2) implicated in UV‐induced erythema were also demonstrated in the LSE exposed to UV‐A or UV‐B. The data suggest that the LSE can be used for studying the effects of U V radiation on skin and may have utility for assessing the efficacy of certain sunscreens against UV‐B and UV‐A.
PHOTOSENSORY TRANSDUCTION IN CILIATES. IV. MODULATION OF THE PHOTOMOVEMENT RESPONSE OF Blepharisma japonicum BY cGMP
Authors: Fabczak Hanna , Tao Nengbing , Fabczak Stanislaw , Song Pill‐Soon
Published: January 2008

Abstract— The effect of various modulators of cytoplasmic guanosine 3',5'‐cyclic monophosphate (cGMP) level on the step‐up photophobic responses in Blepharisma japonicum has been investigated to clarify the possible role of cGMP in the mechanism of photosensory signal transduction. Membrane‐permeable analogs of cGMP, 8‐bromo‐guanosine 3',5'‐cyclic monophosphate or dibutyryl cGMP, caused a marked dose‐dependent prolongation of the latency for the photophobic response, resulting in inhibition of the photophobic response in Blepharisma japonicum. A similar effect was observed when cells were treated with 3'‐isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, and pertussis toxin, a G‐protein activity modulator. The G‐protein activator, fluoroaluminate, and 6‐anilino‐5,8‐quinolinedione (LY 83583), an agent which effectively lowers the cytoplasmic cGMP level, significantly enhanced the photoresponsiveness of these ciliates to visible light stimuli. These results suggest that cellular cGMP serves as a signal modulator in the photophobic response of Blepharisma japonicum.
PHOTOCHEMISTRY, PHOTOPHYSICS, AND MECHANISM OF PYRIMIDINE DIMER REPAIR BY DNA PHOTOLYASE
Authors: Kim Sang‐Tae , Sancar Aziz
Published: January 2008

Abstract— DNA photolyases photorepair pyrimidine dimers (PyroPyr) in DNA as well as RNA and thus reverse the harmful effects of UV‐A (320–400 nm) and UV‐B (280–320 nm) radiations. Photolyases from various organisms have been found to contain two noncovalently bound cofactors; one is a fully reduced flavin adenine dinucleotide (FADH‐) and the other, commonly known as second chromophore, is either methenyltetrahydrofolate (MTHF) or 8‐hydroxydeazaflavin (8‐HDF). The second chromophore in photolyase is a light‐harvesting molecule that absorbs mostly in the near‐UV and visible wavelengths (300–500 nm) with its high extinction coefficient. The second chromophore then transfers its excitation energy to the FADH‐. Subsequently, the photoexcited FADH‐ transfers an electron to the Pyr<>Pyr generating a dimer radical anion (Pyr<>Pyr‐) and a neutral flavin radical (FADH‐). The Pyr<>Pyr‐ is very unstable and undergoes spontaneous splitting followed by a back electron transfer to the FADH‐. In addition to the main catalytic cofactor FADH‐, a Trp (Trp277 in Escherichia coli) in apophotolyase, independent of other chromophores, also functions as a sensitizer to repair Pyr <> Pyr by direct electron transfer.
PHOTOCHEMISTRY OF CONJUGATED POLYACETYLENES: [2+2] PHOTOCYCLOADDITION OF l‐PHENYL‐l,3,5‐HEXATRIYNES WITH SOME OLEFINS
Authors: Chung Chang Beom , Kwon Jang Hyuk , Shim Sang Chul , Hoshino Mikio
Published: January 2008

Abstract— Irradiation of 1‐phenyl‐1,3,5‐hexatriynes with various olefins in methylene chloride yields [2 + 2] type 1:1 photoadducts. The photoreaction proceeds through a triplet excited state and shows site selectivity and regioselectivity. Olefins with electron‐withdrawing substituents, such as dimethyl fumarate, fumaronitrile, acrylonitrile, methyl acrylatc, and styrene, are more reactive than electron‐rich olefins, suggesting that the triplet excited states of 1‐phenyl‐1,3,5‐hexatriynes have a nucleophilic radical character.
ADENOSINE‐MEDIATED PHOTOREACTION OF 4,5′,8‐TRIMETHYLPSORALEN WITH ALCOHOLS
Authors: Yun Mi Hong , Choi Seung Ju , Shim Sang Chul
Published: January 2008

Abstract— Irradiation of thin films consisting of 4,5′,8‐trimethylpsoralen (TMP), adenosine and small amounts of alcohols led to TMP‐alcohol photoadducts in addition to TMP‐adenosine photoadducts. Four TMP‐ethanol and two TMP‐methanol adducts have been separated and characterized. Covalent bonds were formed between the 4‐carbon of TMP and the α‐carbon to the hydroxy group in the alcohols. The TMP‐alcohol photoadducts were formed only in the TMP film containing small amounts of alcohol and adenosine. Furthermore, no photoadduct of TMP and ribose was detected upon photolysis of a TMP‐ribose film, suggesting that the adenine moiety plays a specific role in the reaction. The interaction of adenosine with psoralens in a dry film may be related to the DNA sequence selectivity observed for the photoreaction of psoralens with DNA.
REEXAMINATION OF BASU THEORY
Authors: Kakitani Toshiaki
Published: January 2008

Abstract— The Basu theory of the solvent effect on the absorption spectra of dye molecules in nonpolar solvent is reexamined. The term due to the transition dipole moment of a solute molecule was found to be irrelevant in the formula of the spectral shift and only the term due to the electronic polarizability was necessary for the spectral shifts of large dye molecules.
ACTIVATION OF THE HUMAN IMMUNODEFICIENCY VIRUS PROMOTER BY UVA RADIATION IN COMBINATION WITH PSORALENS OR ANGELICINS
Authors: Zmudzka Barbara Z. , Strickland Amparo G. , Miller Sharon A. , Valerie Kristoffer , Dall'Acqua Francesco , Beer Janusz Z.
Published: January 2008

Abstract— The effects of mono‐ and bifunctional furocoumarins plus UVA radiation (PUVA and related treatments) on the human immunodeficiency virus‐1 (HIV‐1) promoter were studied using HeLa cells stably transfected with the chloramphenicol acetyl transferase gene under the control of the HIV‐1 promoter. The experiments were performed with three psoralens (5‐methoxypsoralen, 5‐MOP; 8‐methoxypsoralen, 8‐MOP; and 4′‐aminomethyl‐4,8,5′‐trimethyl‐psoralen, AMT) and four angelicins (angelicin; 4,5′‐diniethylangclicin, 4,5′‐DMA; 6,4′‐dimethylangelicin, 6,4′‐DMA; and 4,6,4′‐trimethylangelicin, TMA). The drugs alone and UVA radiation alone showed no erect on the HIV promoter. However, when the cells were incubated with the furocoumarins at 0.1–40 μg/mL and then irradiated. the HIV promoter was activated in distinct fluence ranges, i.e. (1) no promoter activity was discernible at low fluences (e.g. at 0.1 μg/mL of 8‐MOP up to 100 kJ/m2), (2) as the fluence was increased, the promoter activity increased to reach a maximum (10–50‐fold with respect to the unexposcd samples), and (3) as the fluence was further increased, the promoter activity decreased. Similar (although shifted on the fluence scale) pattcrns were observed with either > 340‐nm UVA radiation or with UVA radiation contaminated with a small amount of UVB radiation (typical for PUVA lamps). The effective fluences were inversely related to the drug concentration. Experiments with 5‐MOP and 8‐MOP indicated reciprocity of the drug concentration and radiation hence. The HIV promoter response patterns were similar for monofunctional angelicins and bifunctional psoralens. This indicated that the furocoumarin‐DNA crosslinks are not a prerequisite for the promoter activation and that the monoadducts suffice to elicit the HIV promoter response. The HIV promoter‐activating effectiveness of diKcrent drugs correlated with their photosensitizing potential. Thus, among psoralens the effectiveness order was AMT >. 5‐MOP >8‐MOP, and among angelicins: TMA > 6,4′‐DMA > 4,5′‐DMA > angelicin. The ektiveness did not vary substantially for 5‐MOP, 8‐MOP, 4,5′‐DMA, and 6,4′‐DMA. The combined drug and UVA radiation doses were higher than those that elicit cellular responses or those that may be received by the human white blood cells during cxtracorporeal PUVA therapy (photopheresis).
THE ANTI‐HIV ACTIVITIES OF PHOTOACTIVE TERTHIOPHENES
Authors: Hudson J. B. , Harris L. , Marles R. J. , Arnason J. T.
Published: January 2008

Abstract— Various synthetic analogues of the naturally occurring terthiophene, α‐terthienyl (αT), were evaluated for anti‐human immunodeficiency virus (HIV) activity. The compounds were incubated individually with a known amount of the virus, with or without UVA radiation (long‐wavelength ultraviolet) and residual virus was monitored for its ability to produce cytopathic effects in cell culture and the production of virus‐specific protein (p24). The basic terthiophene structure was essential for good anti‐HIV activity, although various side chains, such as alcohols, bromo, methyl, thiomethyl and trimethylsilyl groups, permitted retention of maximum activity. Under optimum conditions, as little as 12 ng/mL of these compounds (i.e approximately 3 × 10−8M) could inactivate 103 infectious virions. None of the compounds however were more active than αT itself. In all cases, UVA radiation was essential. Several side chains decreased the antiviral efficacy, and some side chains abrogated the activity.
GENERAL PURPOSE LAMPS INDUCE POLYOMA DNA REPLICATION IN H3 CELLS
Authors: Rutberg Susan E. , Ronai Zeev
Published: January 2008

Abstract— We have previously demonstrated the ability of UVC (254 nm) radiation to induce asynchronous polyoma replication in rat fibroblast cells (H3 line) that contain an integrated copy of polyoma virus. In the present study we show that general purpose lamps can induce polyoma replication in these cells as well. The amount of UV radiation emitted by three different light sources was determined and the effects of each source on the replication of polyoma DNA was assessed. Our findings indicate that a 100 W incandescent lamp had a minimal effect on replication, whereas a 90 s exposure to a halogen lamp or a 160 W mercury vapor lamp induced replication 1.5‐fold and 2‐fold, respectively, in comparison with nontreated controls. We have previously shown that asynchronous polyoma replication in H3 cells involves UV‐inducible cellular protein factors. Our present results indicate that these factors are also activated by exposure to commonly used lamps that emit comparable doses of UV radiation.
PROPERTIES OF ZINC AND MAGNESIUM METHYL BACTERIOPHEOPHORBIDE d AND THEIR AGGREGATES
Authors: Cheng Peiling , Liddell Paul A. , Ma Sharon X. C. , Blankenship Robert E.
Published: January 2008

Abstract— Light‐harvesting bacteriochlorophylls are believed to he aggregated in oligomcric forms in chlorosomes of green photosynthetic bacteria. Zn and Mg methyl bacteriopheophorhides d (MBPd) were synthesized from chlorophyll a and studied as model compounds for bacteriochlorophyll d. Monomeric Zn and Mg MBPd in methanol have Qy absorption maxima at 650 nm and 657 nm and fluorescence decay lifetimes of 5.1 ns and 5.4 ns, respectively, comparcd to 5.6 ns for bactcriochlorophyll d. Zn and Mg MBPd both form oligomers in nonpolar solvents and exhibit Q, absorption maxima at 728 nm and 731 nm and fluorescence decay lifetimes of 14 ps and 19 ps, respectively, compared to 730 nm and 9 ps for similar bacteriochlorophyll d aggregates. One of the diastereomers at the 3l position, R‐Mg MBPd, forms intermediate‐sized aggregated species that are equivalent to the dimer and a highly fluorescent species formed by bacteriochlorophylls c and d. The similarities of quantitative propcrtics between the model compounds, and the antenna pigments bacteriochlorophyll c and d indicate that Mg and Zn MBPd are good models for studying pigment interactions in chlorosomes and that the long hydrocarbon tail in the natural pigment is not required for oligomer formation. The dimer and the highly fluorescent species do not appear to be the building blocks of the oligomcr.
SINGLET‐OXYGEN GENERATION AT GAS‐LIQUID INTERFACES: A SIGNIFICANT ARTIFACT IN THE MEASUREMENT OF SINGLET‐OXYGEN YIELDS FROM OZONE‐BIOMOLECULE REACTIONS
Authors: Kanofsky Jeffrey R. , Sima Paul D.
Published: January 2008

Abstract— Several ozone‐biomolecule reactions have previously been shown to generate singlet oxygen in high yields. For some of these orone‐biomolecule reactions, we now show that the apparent singlet‐oxygen yields determined from measurements of 1270 nm chemiluminescence were artifactually elevated by production of gas‐phase singlet oxygen. The gas‐phase singlet oxygen results from the reaction of gas‐phase ozone with biomolecules near the surface of the solution. Through the use of a flow system that excludes air from the reaction chamber, accurate singlet‐oxygen yields can be obtained. The revised singlet‐oxygen yields (mol 1O2 per mol O3) for the reactions of ozone with cysteine, reduced glutathione, NADH, NADPH, human albumin, methionine, uric acid and oxidized glutathione are 0.23 ± 0.02, 0.26 ± 0.02, 0.48 ± 0.04, 0.41 ± 0.01, 0.53 ± 0.06, 1.11 ± 0.04, 0.73 ± 0.05 and 0.75 ± 0.01, respectively. These revised singlet‐oxygen yields are still substantial.
EFFECTS OF BOUND MONOCLONAL ANTIBODIES ON THE DECAY OF THE PHOTOTRANSFORMATION INTERMEDIATES I1,21700 FROM NATIVE Avena PHYTOCHROME*
Authors: Lindemann Peter , Braslavsky Silvia E. , Cordonnier Marie‐Michéle , Pratt Lee H. , Schaffner Kurt
Published: January 2008

Abstract–Thc kinetics of the microsecond phototransformation intermediates of 124 kDa Avena phytochrome (17001,2) were studied in the prcsence of bound monoclonal antibodies at various temperatures. A global analysis was applied to the decays at all wavelengths at each temperature in order to derive the rate constants and the decay‐associated spectra of the three decay components. Monoclonal antibodies bound to specific epitopes altered the Arrhenius parameters of both 17001,2 decay components. The strongest influence on these parameters was observed with OAT 8 (epitope between residues 624 and 686), which decreased by more than 50% the activation parameters of both components. This decrease is interpreted to result from an increased flexibility induced by this antibody in the ground state or in the transition state of bonds changing during the decay of both 1700 transients. Thus, the OAT 8 cpitope appears to be functionally important during the decay of the 17001,2 intermediates. For the case of 11001 bound OAT 23 and OAT 25 (epitopes between residues 1 and 66) reduced even further the relatively small flexibility of these bonds in the red light‐absorbing form of phytochrome (P1) without antibodies, as reflected by the high preex‐ponential factors for its decay. This resulted also in higher activation energies for this decay in the presence of the antibodies. Thus, the amino‐terminus should act as a rigid spacer of the chromophore cavity without affecting it during the microsecond transformation, because the Arrhenius parameters for these decays are similar to those for small phytochrome. The possible implications of the influence of the various antibodies on the bleaching remaining after the decay of 17001,2 are discussed.
DNA REPAIR IN THE VARIABLE PLATYFISH (Xiphophorus variatus) IRRADIATED in vivo WITH ULTRAVIOLET B LIGHT
Authors: Mitchell David L. , Scoggins J. Travis , Morizot Donald C.
Published: January 2008

Abstract— Dark‐ and light‐dependent DNA repair processes were studied in vivo in the variable platyfish, Xiphophorus vuriatus. Excision (dark) repair of the (6–4) photoproduct was more efficient than that of the cyclobutane dimer with ∼ 70% of the (6–4) photoproducts reniovcd by 24 h post‐UVB radiation compared to ∼30% of the cyclobutane dimers. Exposure to photoreactivating light resulted in rapid loss of most (>90%) of the cyclobutane dimers and increased excision repair of the (6–4) photoproduct. Preexposure to photoreactivating light 8 h prior to UVB radiation increased the rate of photoreactivation two‐fold.
ALTERED SPECTRAL PROPERTIES OF THE B875 LIGHT‐HARVESTING PIGMENT‐PROTEIN COMPLEX IN A Rhodobacter sphaeroides MUTANT LACKING pufX
Authors: Westerhuis Willem H. J. , Farchaus Joseph W. , Niederman Robert A.
Published: January 2008

Abstract— Mutants of Rhodobacler sphac, roicies lacking the pufX gene are unable to grow photosynthetically and have been reported to show impaired cyclic electron flow and elevated B875 levels when grown at low oxygen tension. An examination of the low‐temperature optical properties of chromatophores from a pufx‐ strain, obtained by complementation of a pufLMX mutant in trans with pufQBALM, encoding polypeptides of the B875 antenna and reaction center complexes, revealed that the absorption and fluorescence emission maxima and the fluorescence polarization rise over the B875‐Qy band were shifted to lower energies. These results suggest that the pufX gene product may limit the aggregation state of the B875 complex, assuring the proper functional arrangement of antenna and reaction ccntcr components within the cores of the photosynthetic units.
PHOTOSENSITIZATION WITH A CHLORIN‐THIOBARBITURATE CONJUGATE
Authors: Kessel David , Morgan Alan
Published: January 2008

Abstract— The photobiologic properties of a chlorin‐thiobarbiturate conjugate were examined. In addition to the characteristic 670 nm chlorin absorbance, the conjugate exhibited new absorbance bands at 517 and 743 nm, but these were not a part of the fluorescence emission spectra, nor was fluorescence observed at wavelengths >670 nm. The action spectrum indicated that the long‐wavelength absorbance of the conjugate was not involved in phototoxicity in cell culture, and that only irradiation at wavelengths associated with the chlorin moiety yielded a cytotoxic effect. In vivo cytotoxicity elicited by 745 nm irradiation is attributed to thermal effects.
FT‐IR SPECTRA OF THE SCHIFF BASES and PROTONATED SCHIFF BASES OF 1‐cis‐ and 7,9‐DIcis‐RETINAL
Authors: Zhu Yun , Larsen R. W. , Liu R. S. H.
Published: January 2008

Abstract— We have prepared and recorded the FT‐IR spectra of the Schiffand protonated SchifT bases of 1‐cis‐ and 7,9‐dicw‐retinal. Analyses of the spectra were aided by corresponding spectra of three deuterated analogs and the retinal isomers. The vibrational assignments of the latter have now been supported by results from normal mode calculations.
THE EFFECT OF PERIPHERAL SUBSTITUTION ON THE BATHOCHROMIC SHIFT OF THE Qy TRANSITION OF BACTERIOCHLOROPHYLL DIMERS; in vitro MODELS OF THE PROTEIN EFFECT ON THE SPECTRUM OF PIGMENT CENTERS IN THE LIGHT‐HARVESTING COMPLEXES*
Authors: Rosenbach‐BELKIN V. , Scherz A. , MlCHALSKI T. J. , Schiffer M. , Norris J.
Published: January 2008

Abstract— The effect of chemical modifications in the side groups of the isocyclic ring V on the formation, optical absorption and circular dichroism of bacteriochlorophyll (Bchl) dimers was examined in a mixture of formamide and water containing TritonX–100 and variable amounts of pyridine. Substitution of the carbomethoxy group in the C132 position with a hydrogen atom, had no effect on the dimerization constant but increased the shift of the Qy transition by 1000 cm‐1 with respect to the native Bchl. Substitution of the C13 hydrogen atom with OH decreased the shift of the Qy transition by 400 cm‐1. The similarity between the spectra of the modified Bchl dimers and Bchl dimers in vivo indicates that protein binding to the side groups at Bchl dimers may profoundly affect the energy of their Qy transition but have minor effects on the Qy transitions of the monomelic Bchl.
PHOTODYNAMIC LIPID PEROXIDATION BY THE PHOTOSENSITIZING NONSTEROIDAL ANTIINFLAMMATORY DRUGS SUPROFEN AND TIAPROFENIC ACID
Authors: Castell Jose V. , Gomez‐Lechon Maria J. , Grassa Carmina , Martinez Luis A. , Miranda Miguel A. , Tarrega Pilar
Published: January 2008

Abstract The photochemistry of the photosensitizing nonsteroidal antiinflammatory drugs tiaprofenic acid and suprofen involves the intermediacy of short‐lived species (i.e. radicals). The data obtained in the present work strongly suggest that such intermediates may be responsible for the phototoxicity of 2‐arylpropionic acids by inducing photodynamic lipid peroxidation at drug concentrations likely to be reached in the skin. This has been investigated using linoleic acid as a model lipid and determining the amount of hydroperoxides by measuring the spectrophotometric absorption at 233 nm, associated with the formation of dienic hydroperoxides. The major photoproducts of tiaprofenic acid and suprofen are derivatives bearing an ethyl side chain. Photoproducts of this type, due to the lack of polar moieties, are highly lipophilic and likely to accumulate in the lipid bilayer of cell membranes. Taking into account their ability to induce photodynamic lipid peroxidation and their marked photostability, it is conceivable that such photoproducts can participate in many catalytic cycles, playing a significant role in the mechanism of photosensitizatinn by tiprofenic acid and suprofen.
SYNTHESIS OF AMPHIPATHIC PORPHYRINS AND THEIR PHOTOINDUCED ELECTRON TRANSFER REACTIONS AT THE LIPID BILAYER‐WATER INTERFACE
Authors: Hwang Kuo Chu , Mauzerall David , Wagner Richard W. , Lindsey Jonathan S.
Published: January 2008

A one flask synthesis of cis‐substituted amphipathic porphyrins is reported. These porphyrins were used to study electrostatic effects on photoinduced electron transfer across the lipid bilayer‐water interface. A neutral porphyrin undergoes only dynamic interfacial electron transfer reactions irrespective of charge of the acceptor, although ionic strength effects indicate a negative charge on the porphyrin donor species. A dianionic porphyrin forms an interfacial static complex with a dicationic electron acceptor, methyl viologen, at low ionic strength. The electron transfer rate within the complex is slow, 105∼ 106 s‐1, which is attributed to a near orthogonal orientation between the donor and the acceptor ∼ orbitals.
SPECTROSCOPIC STUDIES OF COUMARIN IN MICELLES
Authors: Marques A. D. S. , Marques G. S. S.
Published: January 2008

Steady‐state and time‐resolved emission spectroscopic techniques have been employed to characterize the coumarin species and identify which species is solubilized in the hydrocarbon core micelles of triton X‐100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and dodecyl lithium sulfate (anionic) solutions under physiological conditions at 77 K. The emission and absorption spectra for the following species of coumarin—monomer, hydrogenbonded complex, molecular aggregation and strong hydrophobic aggregates—were recorded in methylcyclohexane (MCH), ethanol, buffers and aqueous solutions. The fluorescence and phosphorescence emissions of monomer in MCH at 77 K are assigned as resulting from 1(*)1 and 3(*)1 states, respectively, originated from the ethylenic bond and carbonyl of the pyrone ring. Molecular orbital calculations using the Hydrogenic Atoms in Molecule, version 3, method were carried out to help interpretation of the spectroscopic results. The photophysical properties from each species are used to probe which species penetrates in the hydrophobic region of micelles. It was found that a fifth species of coumarin assigned as the “action species” is solubilized into the interior of micelles. These observations could lend some insight into the mechanism of transporting coumarins across the membrane.
PHOTODYNAMIC TREATMENT OF YEAST WITH CHLOROALUMINUM‐PHTHALOCYANINE: ROLE OF THE MONOMERIC FORM OF THE DYE
Authors: Paardekooper M. , Gompel A. E. Van , Bont H. J. G. M. De , Nagelkerke J. F. , Steveninck J. Van , Broek P. J. A. Van den
Published: January 2008

The effect of photodynamic treatment on the yeast Kluyveromyces marxianus with aluminum‐phthalocyanines has been studied. It was found that the nonsulfonated sensitizer caused light‐dependent loss of colony‐forming capacity, whereas the mono‐ and tetrasulfonated forms did not induce loss of clonogenicity. The effect of the nonsulfonated sensitizer increased with longer preincubation periods of cells with the dye. Formation of cellattached, mostly intracellularly localized monomelic sensitizer also increased with time. The amount of cell‐bound multimeric nonsulfonated phthalocyanine did not vary with time. Experiments designed to specifically increase the amount of cell‐attached monomers led also to an increased photoinactivation of the cells. It is therefore concluded that the photodynamic effect of the nonsulfonated Al‐phthalocyanine is mediated by the monomeric form of the dye.
LIGHT REACTIONS OF THE CILIATE Stentor coeruleus‐A THREE‐DIMENSIONAL ANALYSIS
Authors: Kuhnel‐Kratz Christian , Hader Donat‐P.
Published: January 2008

A computer‐controlled three‐dimensional tracking and motion analysis system was developed to study the responses of Stentor coeruleus to short light pulses and to evaluate its distribution patterns. In addition to photokinesis and phototaxis, the step‐up photophobic response was analyzed, which includes a gravity‐controlled component at higher fluence rates and a light direction‐dependent component at lower fluence rates.
PHOTOCYTOTOXICITY OF CURCUMIN
Authors: Dahll Thomas A. , Bilski Piotr , Reszka Krzysztof J. , Chignell Colin F.
Published: January 2008

Curcumin, bis(4‐hydroxy‐3‐methoxyphenyl)‐l,6‐diene‐3,5‐dione, is a yellow‐orange dye derived from the rhizome of the plant Curcuma longa. Curcumin has demonstrated phototoxicity to several species of bacteria under aerobic conditions (Dahl, T. A., et al., 1989, Arch. Microbiol. 151 183), denoting photodynamic inactivation. We have now found that curcumin is also phototoxic to mammalian cells, using a rat basophilic leukemia cell model, and that this phototoxicity again requires the presence of oxygen. The spectral and photochemical properties of curcumin vary with environment, resulting in the potential for multiple or alternate pathways for the exertion of photodynamic effects. For example, curcumin photogenerates singlet oxygen and reduced forms of molecular oxygen under several conditions relevant to cellular environments. In addition, we detected carbon‐centered radicals, which may lead to oxidation products (see accompanying paper). Such products may be important reactants in curcumin's phototoxicity since singlet oxygen and reduced oxygen species alone could not explain the biological results, such as the relatively long lifetime (t12= 27 s) of the toxicant responsible for decreased cell viability.
EFFECTS OF LIGHT ON T‐CELLS IN HIV‐INFECTED SUBJECTS ARE NOT DEPENDENT ON HISTORY OF SEASONAL AFFECTIVE DISORDER
Authors: Rosenthal Norman E. , Brown Charlotte , Oren Dan A. , Galetto Giorgio , Schwartz Paul J. , Malley James D.
Published: January 2008

In order to evaluate the effect of light on helper‐ and suppressor‐T‐cell counts in HIV‐infected individuals, with and without a history of seasonal affective disorder (SAD), we treated 35 subjects with 45 min of light therapy in the morning, in a crossover design involving two 2 week treatment conditions: visible white light (half‐peak band width, 530‐620 nm; 10 000 lux) and visible red light (half‐peak band width, 615‐685 nm; 175 lux). We found small but significant differences between the two treatment conditions, with higher CD4 and CD8 levels during the white, as compared with the red, condition. There were no differences between baseline and treatment conditions. Both light treatment conditions were associated with significant mood improvements in the SAD, but not the non‐SAD, subjects. There was no evidence that the higher cell counts seen under the bright light conditions were mediated by the effects of light on mood or on plasma Cortisol levels. While the size of the light effect on T‐cells renders questionable the potential therapeutic value of this treatment modality for HIV, the finding is of theoretical interest and is reassuring for those HIV‐infected individuals who require light treatment for other reasons.
PHOTOPHYSICAL AND PHOTOSENSITIZING PROPERTIES OF BENZOPORPHYRIN DERIVATIVE MONOACID RING A (BPD‐MA)*
Authors: Aveline Béatrice , Hasan Tayyaba , Redmond Robert W.
Published: January 2008

The photophysical properties of benzoporphyrin derivative monoacid ring A (BPD‐MA), a second‐generation photosensitizer currently in phase II clinical trials, were investigated in homogeneous solution. Absorption, fluorescence, triplet‐state, singlet oxygen (O2(1Δg)) sensitization studies and photobleaching experiments are reported. The ground state of this chlorin‐type molecule shows a strong absorbance in the red (λ≈ 688 nm, ɛ≈ 33 000 M−1 cm−1 in organic solvents). For the singlet excited state the following data were determined in methanol: energy level, Es= 42.1 kcal mol−1, lifetime, Φf= 5.2 ns and fluorescence quantum yield, Φf= 0.05 in air‐saturated solution. The triplet state of BPD‐MA has a lifetime, τf >. 25 ns, an energy level, ET= 26.9 kcal mol−1 and the molar absorption coefficient is ɛT= 26 650 M−1 cm−1 at 720 nm. A dramatic effect of oxygen on the fluorescence (φf) and intersystem crossing (φT) quantum yields has been observed. The BPD‐MA presents rather high triplet (φT= 0.68 under N2‐saturated conditions) and singlet oxygen (φΔ= 0.78) quantum yields. On the other hand, the presence of oxygen does not significantly modify the photobleaching of this photostable compound, the photodegradation quantum yield (φPb) of which was found to be on the order of 5 × 10−5 in organic solvents.
AGGREGATION OF COLLAGEN EXPOSED TO UVA IN THE PRESENCE OF RIBOFLAVIN: A PLAUSIBLE ROLE OF TYROSINE MODIFICATION
Authors: Kato Yoji , Uchida Koji , Kawakishi Shunro
Published: January 2008

Riboflavin‐sensitized photodynamic modification of collagen led to significant formation of cross‐linked molecules. Sodium azide or l,4‐diazabicyclo(2,2,2)octane, which are known to be singlet oxygen quenchers, and catalase could not inhibit the modification. Surprisingly, the collagen modification was accelerated in the presence of superoxide dismutase. The aggregation was accompanied by the loss of tyrosine and histidine residues in the collagen. An inhibitory effect of dissolved oxygen on the modification of collagen was observed. Similarly, the loss of tyrosine residues in the irradiated collagen was inhibited in the presence of dissolved oxygen. Dityrosine formation was also observed with the loss of tyrosine. These results indicate that photodynamic modification of tyrosine probably contributes to the riboflavin‐sensitized cross‐linking of collagen through the formation of dityrosine.
X‐RAY INDUCED VISIBLE LUMINESCENCE OF PORPHYRINS
Authors: Kokotov Sophia , Lewis Aaron , Neumann Ronny , Amrusi Shmuel
Published: January 2008

A concept has been presented whereby X‐ray irradiation can be used to induce visible luminescence of chromophores such as porphyrins. The essential aspects of the idea have been demonstrated in a supramolecular assembly consisting of a water‐dispersed polystyrene latex with an embedded scintillating compound, 2,5‐diphenyloxa‐zole, and an externally attached hematoporphyrin. X‐ray excitation of the assembly yields an emission spectra typical for hematoporphyrin with fluorescent yields. of up to 3% with respect to 2,5‐diphenyloxazole emission. Significant quenching in the presence of dioxygen indicates that singlet oxygen is formed at atmospheric conditions.
PARTIAL PROTECTION OF PHOTODYNAMIC‐INDUCED SKIN REACTIONS IN MICE BY N‐ACETYLCYSTEINE: A PRECLINICAL STUDY
Authors: Baas Paul , Oppelaar Hugo , Van Der Valk Martin A. , Zandwijk Nico van , Stewart Fiona A.
Published: January 2008

Abstract The major side effect of photodynamic therapy (PDT) using Photofrin® is enhanced skin sensitivity for sunlight, which persists for 3‐8 weeks after injection. Formation of singlet oxygen and radicals is believed to be involved in the basic mechanism of inducing skin damage. Reducing this side effect would make PDT more widely acceptable, particularly for palliative use. Hairless dorsal skin patches of mice, injected with 10 mg kg−1 photofrin intraperitoneally (i.p.) 24 h before illumination, were used to evaluate the effect of increasing light doses. The light was obtained from a halogen lamp and transmitted via a fiber optic to illuminate a field of 2.5 cm2. After establishing a dose‐response relationship for single or fractionated light dose illumination of the skin, drugs known to scavenge radicals, quench singlet oxygen or interfere with histamine release were tested for their protective effect. N‐acetylcysteine (NAC), a radical scavenger, administered i.p. (1000 and 2000 mg kg−1) 1 h before illumination produced a significant decrease in skin damage at light doses >50 J cm−2 (protection factor of 1.3‐1.8). When NAC was administered in a dose of 500 mg kg−1, no protection was observed. Fractionated illumination experiments in combination with multiple injections of NAC (1000 mg kg−1) also failed to show any protection. The addition of Ranitidine®, a histamine blocking agent (25‐100 mg kg−1, given prior to illumination, resulted in a limited protection at higher light doses. From this study we conclude that NAC could be of value in amelioration of the photosensitivity in patients treated with PDT.
MODEL STUDIES ON THE PHOTOCHEMICAL PRODUCTION OF LENTICULAR FLUOROPHORES
Authors: Ellozy Aziza R. , Wang Ren H. , Dillon James
Published: January 2008

Abstract With aging, human lens proteins accumulate fluorophores having blue and green emissions. Model studies were undertaken to determine the role of 3‐hydroxykynurenine (3‐HK) and its glucoside (3‐HKG) in the photochemical production of those fluorophores. Experiments were carried out using 10−3M 3‐HK solutions in the presence or absence of glycine (1M), which was used to mimic the environment of the lens. The solutions were photolyzed (transmission above 295 nm) for various periods of time while the loss of starting material and the formation of fluorescent photoproducts (blue emission at 470 nm, and green emission at 520 nm) were monitored using fluorescence and UV‐visible spectroscopy and thin‐layer and high‐pressure liquid chromatography analysis. Several parameters were varied such as oxygen tension and the addition of the free radical scavenger, penicillamine. The photolytic loss of 3‐HK in the absence of glycine occurred approximately 5‐10 times faster than in its presence. Conversely, blue and green fluorophores formed in irradiated solutions containing glycine but not with the photolysis of 3‐HK alone. The blue fluorophore was formed first and appeared then to be photochemically converted to the green one, with the rate of formation of the latter increasing with an increase in UV dosage or oxidizing conditions. The addition of penicillamine drastically reduced the photochemical formation of both fluorophores.

Both the blue and green fluorophores appear to result from the photochemically induced covalent attachment of 3‐HK to glycine. In the human lens, these reactions can explain the age‐related loss of 3‐HKG with the concomitant formation of fluorophores covalently attached to lens proteins, probably via the amino group of lysine.