bluuebunny/crossref_metadata_2025 huggingface dataset:
ORIGIN OF THE RED SHIFTED ABSORPTION IN PHYCOCYANIN 632 FROM Mastigocladus laminosus
Authors: Gottschalk L. , Fischer R. , Lottspeich F. , Scheer H.
Published: January 2008

A phycocyanin (PC) with γmax= 632 nm (PC632) was isolated from extracts of the cyanobacterium Mastigocladus laminosus. The complex contained three polypeptides migrating in SDS‐PAGE around 22 kDa. The N‐termini of the three polypeptides are identical. They are homologous to rod‐core linker polypeptides from this and another cyanobacterium and are identical to one of them. Reconstitution of PC (γmax=614–620 nm) with the 22 kDa polypeptide produced again the red‐shifted PC632. Phycobilisomes isolated at pH 6 or 7 contain, if any, only traces of 22 kDa polypeptides. Origin and functions of the polypeptides are discussed, they are most likely proteolytic fragments of allophycocyanin‐PC rod‐core linkers that contain the PC‐binding domain.
CARBOXYLATED ZINC‐PHTHALOCYANINES–II* DIMERIZATION AND SINGLET MOLECULAR OXYGEN SENSITIZATION IN HEXADECYLTRIMETHYLAMMONIUM BROMIDE MICELLES
Authors: Daraio Marta E. , Aramendía Pedro F. , Román Enrique A. San , Braslavsky Silvia E.
Published: January 2008

The dimerization of the diamide of zinc‐tetracarboxyphthalocyanine was studied spectro‐scopically in hexadecyltrimethylammonium bromide (CTAB) micelles at surfactant concentrations from 0.026 to 0.1 M and dye concentrations between 0.1 and 10 μM. The apparent dimerization constant in CTAB 0.1 M is 8.6 × 105M−1, while the intramicellar dimerization constant is 1.8 × 103. The dimer absorption spectrum was also obtained. Singlet molecular oxygen sensitization was studied by steady state photolysis using 1,3‐diphenylisobenzofurane as scavenger in 0.1 M CTAB. The usual sensitization mechanism is extended to include dimer reactions. Singlet molecular oxygen sensitization yields for monomer and dimer in the micelles are 0.7 and 0.1, respectively. With the reported values it is possible to calculate the average yield of singlet molecular oxygen production at any surfactant and dye concentrations.
DIFFERENTIAL INACTIVATION OF SURROGATE VIRUSES WITH MEROCYANINE 540
Authors: Lytle C. D. , Budacz A. P. , Keville E. , Miller S. A. , Prodouz K. N.
Published: January 2008

Bacteriophages may be useful as surrogates for animal viruses when the virucidal properties of different photosensitizing compounds are initially investigated. We studied photoinactivation of four bacteriophages, φX174, T7, PRD1, and φ6, by the dye merocyanine 540 (MC540) (15 μ g/mL). Merocyanine 540 (MC540) should be most effective with lipid‐containing viruses, since it is primarily lipophilic (but also binds to proteins). Two of the phages, PRD1 and φ6 contain lipid, with only φ6 having an external lipoprotein envelope. Filtered radiation (450–600nm) from a 750 W projector was used at16–100 W/m2. The survival curves of the different viruses clearly demonstrated different levels of sensitivity to photoinactivation by MC540, with φ6 (Do= 1.5 kJ/m2) being the most sensitive, followed by T7 (21‐fold less sensitive). While both PRD1 and (J>6 have lipid components, only φ6 was photoinactivated by MC540. Thus the internal lipid components of PRD1 were not sufficient to allow photoinactivation by this dye, at fluences up to 300 kJ/m2. For comparison, we also photoinactivated Herpes simplex virus (Do= 0.053 kJ/m2) and found it to be 28‐fold more sensitive than φ6 to photoinactivation by the same concentration of MC540. Thus φ6 may be used as a surrogate for enveloped human viruses for photoinactivation by lipophilic dyes, but the results may only be useful qualitatively.
ENHANCEMENT OF THE SENSITIVITY OF RADIATIVE and NON‐RADIATIVE DETECTION TECHNIQUES IN THE STUDY OF PHOTOSENSITIZATION BY WATER SOLUBLE SENSITIZERS USING A REVERSE MICELLE SYSTEMS*,†
Authors: Redmond Robert W.
Published: January 2008

The study of photosensitization processes in aqueous solution is complicated by the unsuit‐ability of water as solvent for the commonly used techniques for monitoring radiative and non‐radiative relaxation processes. The infrared luminescence method is hampered by the relatively weak intensity of emission and short lifetime of singlet molecular oxygen, O2(1Δg), in water. Photoacoustic and photothermal detection of the dominant non‐radiative relaxation process for O2(1Δg) is also inhibited by the unfavorable physico‐chemical properties of water which reduce the sensitivities of these techniques for the study of sensitizers in aqueous with respect to non‐aqueous media. Such problems have been alleviated by incorporating the sensitizer in the aqueous core of aerosol OT reverse micelles. It is demonstrated that the sensitivity of both radiative and non‐radiative detection depends not on the local environment of the sensitizer but on the overall composition of the medium, which, in the case of reverse micelle solutions, is predominantly hydrocarbon. This produces a 4.5 and 6‐fold enhancement of the sensitivity of luminescence and optoacoustic detection, respectively, in comparison to purely aqueous solution. The utility of the method is demonstrated for Rose Bengal, where quantum yields of intersystem crossing (φisc) of 0.78 (LIOAC) and singlet oxygen generation (φδ) of 0.81 (LIOAC) and 0.80 (TRLD) were measured. Phenazine was also studied for comparative purposes and to corroborate values obtained for Rose Bengal.
PHOTOCHEMISTRY IN A CYCLODEXTRIN CAVITY. PRIMARY PROCESSES IN THE PHOTOREDUCTION OF 3‐ and 4‐BENZOYLPYRIDINE STUDIED BY LASER FLASH‐PHOTOLYSIS*
Authors: MONT Sandra , Camaioni Nadia , Bortolus Pietro
Published: January 2008

The photochemistry of 3‐ and 4‐benzoylpyridine‐cyclodextrin inclusion complexes (BPyCDx) was examined by nanosecond laser flash‐photolysis and stationary techniques. The lifetimes of the triplet complex and of the triplet radical pair, formed by H‐abstraction from a glucose unit of the CDx, have been measured in β‐CDx complexes. The reactivity of the heterocyclic ketones with CDx is higher than that of benzophenone, but the lower binding ability of the macrocycle toward these more hydrophylic molecules induces faster separation of the geminate radicals. The quantum yields of the escaped radicals and their decay kinetics have been determined. The β‐CDx cage favours geminate recombination reactions, while α‐ and ‐γ‐CDx tend to release the guest molecule. Cage products have been spectroscopically characterized in the case of the 3‐BPy‐β‐CDx system.
INTRAMOLECULAR EXCIMER FORMATION and MOLECULAR RECOGNITION OF MODIFIED CYCLODEXTRINS APPENDED BY TWO NAPHTHALENE RINGS*
Authors: Minato Shingo , Osa Tetsuo , Morita Masahiko , Nakamura Asao , Ikeda Hiroshi , Toda Fujio , Ueno Akihiko
Published: January 2008

The intramolecular excimer formation of 6A,6B‐, 6A,6C‐, 6A,6D‐, and 6A,6E‐bis(2‐naphthyl‐sulfonyl)‐γ‐cyclodextrins (1, 2, 3, and 4, respectively) and 6A.6B‐, 6A,6C‐, and 6A,6D‐bis(2‐naphthyl‐sulfonyl)‐β‐cyclodextrins (5, 6, and 7, respectively) has been studied in 10% ethylene glycol aqueous solution. The two naphthyl rings are co‐included in the γ‐cyclodextrin cavities of1–4, and marked excimer emission was observed for 2, 3, and 4. On the other hand, almost pure monomer emission was observed for 5, 6, and 7 due to inclusion of one of two naphthyl rings in the β‐cyclodextrin cavities. Compounds 2, 3, 6, and 7 showed remarkable guest‐induced enhancement in the excimer emission, and this property was used for detecting several organic compounds with remarkable molecular recognition.
PHOTOCHEMISTRY ON SURFACES: TRIPLET‐TRIPLET ENERGY TRANSFER ON MICROCRYSTALLINE CELLULOSE STUDIED BY DIFFUSE REFLECTANCE TRANSIENT ABSORPTION and EMISSION SPECTROSCOPY*
Authors: Wilkinson F. , Leicester P. A. , Ferreira L. F. V. , Freire V. M. M. R.
Published: January 2008

Triplet‐triplet energy transfer has been studied between benzophenone and an oxazine dye (2,7‐bis(diethyl‐amino)‐phenazoxonium chloride) co‐adsorbed on the surface of microcrystalline cellulose. Ground state absorption and fluorescence measurements provide evidence for dimer formation of the oxazine dye when adsorbed on cellulose in contrast to the behaviour in ethanol solution where no dimerization is observed. The equilibrium constant for dimerization, which is found to be (1.0 × 0.1) × 106 mol−1 g (2560 × 250 dm3 mol−1) for oxazine alone on cellulose decreases in the presence of co‐adsorbed benzophenone. Fluorescence is detected from excited monomeric but not from excited dimeric oxazine. The absorption spectrum of the triplet state of oxazine adsorbed on cellulose was obtained and its extinction coefficient evaluated relative to that of triplet benzophenone which was used as a sensitizer. The lifetime of adsorbed triplet oxazine is 4.3 ms which is 300 times longer than that in acetonitrile solution.

The efficiency of energy transfer from triplet benzophenone to oxazine on cellulose was studied using both time resolved sensitized absorption and phosphorescence intensity measurements as a function of oxazine concentration. Lifetime measurements show that the energy transfer process involves static quenching since the benzophenone lifetime is independent of oxazine loading at the surface. A mechanism is proposed to explain the results in which one oxazine molecule is suggested as being able to quench phosphorescence from a “pool” consisting of 2 to 3 benzophenone molecules.
TYPE I and TYPE II PHOTOSENSITIZATION BY THE ANTIBACTERIAL DRUG NALIDIXIC ACID. A LASER FLASH PHOTOLYSIS STUDY*
Authors: Vermeersch G. , Ronfard‐Haret J. C. , Bazin M. , Carillet V. , Morliere P. , Santus R.
Published: January 2008

The 355 nm laser flash photolysis of nalidixic acid at pH 9.2 leads to the formation of the nalidixate anion triplet state (absorption Λmax= 620 nm; 5700 ≤εT≤ 9000 M−1cm−1; 0.6 ≤φT≤ 1). The first order triplet state decay (kT= 7.7 times 10−3s−1) is accompanied by a diffusion controlled triplet‐triplet annihilation. Oxygen efficiently quenches the triplet state (k = 3.2 times 109M−1s−1). The nalidixate radical dianion (absorption Λmilx= 650 nm; ε= 3000 M−1cm−1) is produced by the diffusion controlled reductive quenching of the triplet state by tryptophan and tyrosine. The superoxide anion (O−2) is produced by diffusion controlled reaction of the radical dianion with oxygen. The O−2 is characterized by its reactions with ferricytochrome c and superoxide dismutase. The physiological form of nalidixic acid is thus a good Type I and Type II photosensitizer.
HYDRATED ELECTRON FORMATION IN NANOSECOND and PICOSECOND LASER FLASH PHOTOLYSIS OF HEMATOPORPHYRIN IN AQUEOUS SOLUTION
Authors: Grabner G. , Getoff N. , Gantchev TS. , Angelov D. , Shopova M.
Published: January 2008

Nanosecond (λcxc= 266, 355 and 532 nm) and picosecond (λcxc. = 355 nm) laser flash photolysis of hematoporphyrin (Hp) was performed in neutral (pH 7.4) and alkaline (pH 12) aqueous solution, as well as in the presence of 0.1% Triton X‐100. The dependence of the yield of photoproduced hydrated electrons (e−aq) on laser pulse energy was studied over a wide range of energies (0.2 to >1000 mJ cm−2). The results show that e˜, are predominantly formed in a two‐photon process at λexc= 266 and 355 nm. One‐photon quantum yields are higher at λexc= 266 nm than at λexc= 355 nm. Both one‐photon and two‐photon pathways are less efficient at higher Hp concentration, reflecting the influence of Hp self‐aggregation. Two‐photon eaq formation is more efficient when 30 ps pulses are used for excitation, as compared to 10 ns pulses. No e−aq could be detected at λexc= 532 nm. Nanosecond pulse‐induced transient spectra obtained at pH 7.4 are also discussed.
EVALUATION OF SKIN CANCER RISK RESULTING FROM LONG TERM OCCUPATIONAL EXPOSURE TO RADIATION FROM ULTRAVIOLET LASERS IN THE RANGE FROM 190 TO 400 nm
Authors: Sterenborg H. J. C. M. , Gruul F. R. de , Kelfkens G. , Leun J. C. van der
Published: January 2008

The relative risk of occupational exposure to radiation from UV lasers was estimated using a mathematical model based on both epidemiological data and animal experiments. Calculations were performed for the 193 nm ArF excimer laser cornea shaping, the 308 nm XeCl excimer laser for coronary angioplasty, and other UV lasers in a laboratory environment. The model included the effects of direct exposure and exposure to scattered radiation. The results show that for the two medical applications the increase in the relative risk is comparable to that of one additional day of sunbathing per year. For subjects exposed to UV lasers in a laboratory setting, the relative risk may increase to a value comparable to that of people with an outdoor profession.
IN VIVO 31P NMR STUDY OF COMBINED HYPERTHERMIA and PHOTODYNAMIC THERAPIES OF MAMMARY CARCINOMA IN THE MOUSE
Authors: Jiang Q. , Chopp M. , Hetzel F. W.
Published: January 2008

Although the sequence and time interval effects of combined photodynamic therapy (PDT) and hyperthermia tumor treatments have been studied using survival curves, tumor regrowth, and cloning assays, the metabolic response to combined treatment measured by nuclear magnetic resonance (NMR) spectroscopy has not yet been clarified. In this study, mammary carcinoma in the flank of C3H mice was subjected to PDT (12.5 mg/kg Photofrin II, 632 ± 1 nm at 200 J/cm2) and water bath hyperthermia (43.5°C, 30 min) with no delay or 4 h delay between treatments. In vivo31P‐NMR spectroscopy was employed to measure energy metabolism and pH of the tumors before and serially after treatment for up to 1 week. The data revealed significant differences in the time course of high energy phosphate levels between treatment combinations, which may reflect the biological effectiveness of the combined treatments. Our observations indicate that 31P‐NMR spectroscopy can be used to evaluate the metabolic response of tumors to treatment with combined PDT and hyperthermia.
PHOTODYNAMIC THERAPY: EFFECT ON THE ENDOTHELIAL CELL OF THE RAT AORTA
Authors: He Dong Ping , Hampton James A. , Keck Rick , Selman Steven H.
Published: January 2008

Previous studies in our laboratory have demonstrated that photodynamic therapy (PDT) of experimental bladder tumors leads to rapid destruction of the endothelial lining within the tumor micro vasculature. Endothelial cell death during PDT may be a consequence of direct cell injury resulting from retention of photosensitizer within the endothelial cell or, alternatively, result from intravascular activation of circulating photosensitizer with subsequent indirect endothelial damage. In the experiments described here, we investigated the possibility that photosensitizer retained within the endothelial cell was sufficient to cause endothelial cell injury in the absence of circulating drug. The experimental model was rat aorta photosensitized in vivo via the intravenous injection of tin(II) etiopurpurin dichloride (SnET2), and subsequent in situ or in vitro (in explant culture) light (670 nm) treatment from an argon pumped dye laser. Damage to the lining of the aorta was assessed morphome‐trically by determining the areal density of silver stained endothelial cells. Results indicate that purpurin SnET2‐PDT directly damages the endothelial lining.
RESPONSES OF LIGHT‐GROWN WILD‐TYPE and LONG‐HYPOCOTYL MUTANT CUCUMBER SEEDLINGS TO NATURAL and SIMULATED SHADE LIGHT*
Authors: Ballare C. L. , Casal J. J. , Kendrick R. E.
Published: January 2008

The photomorphogenic control of hypocotyl extension growth was characterized in wild type (WT) and long hypocotyl (Ih) mutant seedlings of cucumber (Cucumis sativus L.) grown under natural radiation in outdoor and glasshouse experiments. Hypocotyl extension growth of WT plants was promoted by supplementing sunlight with far‐red light during the photoperiod, by reducing the amount of blue light reaching either the whole shoot or the hypocotyl, and by reducing the amount of UV reaching the whole shoot.The Ih seedlings only responded to a reduction in UV‐B levels. Both WT and Ih seedlings showed phototropic responses to the direction of blue light. Increasing degrees of vegetational shade promoted hypocotyl growth of WT plants. The Ih mutant showed no hypocotyl growth promotion by natural shade in glasshouse experiments (no UV‐B, low water demand) and a reduced response (10‐23% of the WT response, according to pretreatment conditions) in outdoor experiments (UV‐B, high water demand).
STRUCTURE OF BACTERIORHODOPSIN and in situ ISOMERIZATION OF RETINAL: A MOLECULAR DYNAMICS STUDY*
Authors: Nonella M. , Wlndemuth A. , Schulten K.
Published: January 2008

Abstract– Henderson's model of the structure of bacteriorhodopsin has been completed by adding the missing loop regions and by subsequent energy minimization and equilibration (for about 100 ps) at 300 K. Analysis of the structure during a later 20 ps molecular dynamics run showed no significant deviations from the Henderson model. In situ isomerization reactions of the retinal chromophore in bacteriorhodopsin have then been simulated to investigate the chromophore protein interaction for the three isomerization reactions: (i) all‐trans→ 13‐cis; (ii)all‐trans→ 13,14‐dicis; and (iii) all‐trans→ 13,15‐dicis. We find that reaction (iii) which accompanies dark‐adaptation of bacteriorhodopsin can proceed in the binding site without any sterical hinderance and involves negligible motions of the covalently bound Lys‐216 and other side groups. Reaction (ii) exhibits a somewhat larger but still small energy barrier and involves little rearrangement of Lys‐216 and the protein backbone. Reaction (i) experiences a sterical impediment amounting to more than 10 kT at physiological temperatures and also induces significant structural changes at the binding site. Our simulations also reveal that reaction (ii) as a photo‐isomerization process can be completed within about 400 fs, whereas reaction (i) requires longer times for completion. Reaction (i) is also accompanied by a co‐rotation of the 14–15 bond by 150° (even when a torsional barrier of 20 kcal/mol is imposed to impede rotation of the 14–15 bond) such that photoreactions (i) and (ii), in effect, lead to very similar final geometries. Isomerization (ii) can readily explain the pump mechanism of bacteriorhodopsin: the sequential, thermal back‐reaction 13,14‐dicis→ 13‐cisall‐trans can be acid‐base catalyzed, i.e., coupled to deprotonation and reprotonation of retinal's Schiff base nitrogen. The orientation of retinal is such that Asp‐85 can act as the acceptor and Asp‐96 as the (indirect) donor. The thermal back‐reaction 13,14‐dicis→ all‐trans can be coupled to vectorial Cl− ion transport as well.
SOLUBILIZATION SITES AND ACID‐BASE FORMS OF DIBUCAINE‐HYDROCHLORIDE IN NEUTRAL AND CHARGED MICELLAR SOLUTIONS
Authors: MERTZ C. J. , LIN C. T.
Published: January 2008

Abstract—

Steady‐state and time‐resolved emission spectroscopic techniques have been employed to characterize the drug species of dibucaine and to identify its location in micellar Triton X‐100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and lithium dodecyl sulfate (anionic) solutions at 77 K. Under physiological conditions, the dibucaine is shown to exist in the free base form (D) while solubilized in the hydrocarbon core of neutral micelles. In cationic micellar solution, dibucaine exists as the monocation species (DH+) where the anesthetic is solubilized in the extramicellar aqueous solution and D is solubilized in the hydrophobic region with close proximity to the micellar interface. In the anionic micelles, interfacial solubilization is most consistent with a site in which the tertiary amine group of the monocation dibucaine (DH+) is anchored at the micellar interface with its quinoline analog penetrating the hydrophobic region. The distinct properties observed for the drug species (i. e. D and DH+) and their solubilization sites in micelles are consistent with a balance between hydrophobic forces, surface polarity and the interfacial electrostatic potential present in the micellar solubilization sites. These observations could lend insight into the molecular basis of pharmacological action, in particular the mechanism of local anesthetic drug transport across membranes.
INTRAVENOUS vs INTRAPERITONEAL SENSITIZER: IMPLICATIONS FOR INTRAPERITONEAL PHOTODYNAMIC THERAPY
Authors: PERRY ROGER R. , SMITH PAUL D. , EVANS STEVEN , PASS HARVEY I.
Published: January 2008

Abstract—

Photodynamic therapy (PDT) is a potential treatment for peritoneal carcinomatosis. However, little data is available regarding the relative distribution of sensitizer to tumor and intra‐abdominal organs, optimal route of sensitizer administration, and maximal tolerated light dose. Tumor and normal tissue sensitizer levels were measured by tissue extraction 3, 24, 48 and 72 h after 10 mg/kg of Photofrin II was given intraperitoneally (IP) or intravenously (IV) in a mouse peritoneal tumor model, and the maximal tolerated PDT light dose determined. Equivalent tumor sensitizer levels were obtained regardless of the route of sensitizer administration. Route of administration, however, did affect the kinetics of tumor sensitizer elimination, with the half‐time for elimination (T1/2) 113.6 h for IP drug and 60.6 h for IV drug. Route of administration also affected sensitizer levels in several intra‐abdominal organs, resulting in somewhat higher tumor to liver and kidney levels at 24 and 72 h after IP sensitizer administration. Despite these tissue distribution differences, route of sensitizer administration did not significantly affect PDT toxicity or mortality when mice were treated with 630 nm light. The maximum tolerated light dose was 1.04 J/cm2. These parameters will prove helpful in designing large scale animal trials assessing the efficacy and safety of intra‐abdominal PDT.
SPECTROSCOPIC STUDIES OF CHLOROPHYLL a AGGREGATES FORMED BY AQUEOUS DIMETHYL SULFOXIDE
Authors: UEHARA KAKU , MIMURO MAMORU , TANAKA MAKOTO
Published: January 2008

Abstract—

Characteristic chlorophyll (Chl) a aggregates formed in aqueous dimethyl sulfoxide (DMSO) were investigated spectroscopically. Four chlorophyll forms were found with increasing DMSO concentration; they are called A‐672, A‐683, A‐695 and A‐665 according to the wavelengths of their absorption maxima. Transformation occurred only in this order. Reverse transformation could not be realized. A‐683 and A‐695 were apparently formed by the interaction of Chl a with DMSO in the linear dimer and linear polymer arrangements, respectively. Coordination of the Mg atom with a DMSO O atom and interaction between the S atom of one DMSO molecule and the O atom of an other DMSO molecule should lead to formation of a sandwich‐type complex of partially overlapping chlorophyll macrocycles (Chl a‐DMSO)n. A‐672 and A‐665 were assigned to Chl a micelles and to dissolved monomeric Chl a in DMSO, respectively. Fluorescence spectra showed that the A‐683 was highly fluorescent, while the A‐695 was less fluorescent. Energy migration within the A‐695 form to a trap with a low fluorescence yield might be responsible for this difference in the emission intensity.
HYDROPHOBICITY‐DEPENDENT FLUORESCENCE PROPERTIES AND INTRACELLULAR FLUOROSPECTROSCOPIC BEHAVIOR OF PHOTOTOXIC DRUGS
Authors: SASAKI MASAKO , MATSUO ITSURO , FUJITA HITOSHI
Published: January 2008

Abstract—

Fluorospectroscopic behavior of chlorpromazine, mequitazine, afloqualone and piroxicam, which are known to induce skin photosensitivity, was examined in both homogeneous solutions and human buccal mucosal cells. Each drug showed large Stokes' shifts and their fluorescence intensities increased in hydrophobic solvents. These results indicated that the drugs tested can be used as hydrophobic fluorescence probes. Fluorescence microscopic observations of buccal mucosal cells treated with these drugs showed that all the drugs, especially chlorpromazine and mequitazine, were distributed in intracellular membranous regions.
DETECTION OF PTERINS IN Phycomyces SPORANGIOPHORES*
Authors: KIEWISCH S. , FUKSHANSKY L.
Published: January 2008

Abstract—

Differential fluorometry with sodium dithionite showed pterin‐like signals in extracts of Phycomyces sporangiophores. After iodine oxidation, pterin, biopterin and neopterin could be separated. The concentrations determined for these three pterins exceed the calculated minimal concentration of 3 times 10−7M for the photoreceptor.
A SPECTROPHOTOMETRIC METHOD FOR CHLOROPLAST ATP SYNTHETASE ASSAY
Authors: KIM CHUL‐SU , JUNG JIN
Published: January 2008

Abstract—

In the present work an assay method of chloroplast adenosine triphosphate (ATP) synthetase has been studied in which the production of ATP from thylakoids was monitored spectrophotometrically by the reduction of NADP+via hexokinase and glucose‐6‐phosphate dehydrogenase reactions. The interference caused by photosynthetic NADPH production was completely eliminated by use of methyl viologen, a PSI electron acceptor. Under the assay conditions established in this study, the rate of ATP synthesis was directly proportional to the amount of chloroplast ATP synthetase. The method appears reliable, convenient and considerably sensitive. In addition, this technique provides a continuous measurement of ATP production from thylakoids with a limiting adenosine diphosphate concentration.
DIETARY HISTIDINE INCREASES MOUSE SKIN UROCANIC ACID LEVELS AND ENHANCES UVB‐INDUCED IMMUNE SUPPRESSION OF CONTACT HYPERSNSITIVITY
Authors: Reilly Sheryl K. , Da Fabo Edward C.
Published: January 2008

Abstract—

Urocanic Acid (UCA) exists in mammalian skin primarily as the trans isomer and is photoisomerized to cis UCA upon UVB absorption. Our previous studies indicated that the photoiaomerization of UCA is the initiating event in UVB‐induced suppression of cell‐mediated immunity (tUCA → cUCA → immune suppression). The purpose of this study was to verify the role of UCA in UV‐induced immune suppression of contact hypersensitivity (CHS) in BALB/c mice. Since UCA is a metabolite of the amino acid L‐histidine, we reasoned that increased dietary levels of histidine should raise skin tUCA levels. If skin tUCA is the UVB photoreceptor for immune suppression, this increase should enhance UV‐induced suppression of CHS. HPLC analysis of skin from BALB/c mice given a histidine‐rich diet (10%) showed that the total amount of UCA is significantly higher in these animals than in mice fed a normal diet. Further, levels of suppression of CHS of 3% and 49% in control fad mice, induced by 4.8 and 7.2 kJ/m2 UVB were significantly increased to 21% and 71% respectively in histidine‐fed animals at these same UVB doses. These findings provide additional support for the UCA model for immune suppression, and provide the first evidence that UV‐induced immune suppression can be enhanced by a dietary component, L‐histidine.
α‐TERTHIENYL PHOTOSENSITIZES DAMAGE TO pBR322 DNA
Authors: WANG TIAN P. , KAGAN JACQUES , TUVESON R. W. , WANG G. R.
Published: January 2008

Abstract—

α‐Terthienyl photosensitizes single strand breaks in pBR322 DNA. Almost identical results were observed under oxygen and under argon. In the presence of oxygen, this DNA nicking was enhanced by histidine and was not affected by superoxide dismutase, catalase, or the antioxidant BHT. Although chemical damage to DNA treated with α‐terthienyl plus near‐UV was clearly demonstrated in vitro, transformation in E. coli with this damaged pBR322 DNA still took place. Likewise, Haemophilus influenzae DNA transforming activity was not significantly decreased by photosensitization with α‐terthienyl.
NANOSECOND KINETIC ABSORPTION AND CALORIMETRIC STUDIES OF CYCLOPENTENONE: THE TRIPLET, SELF‐QUENCHING, AND THE PREDIMERIZATION BIRADICALS
Authors: CALDWELL RICHARD A. , TANG WEI , SCHUSTER DAVID I. , HEIBEL GEORGE E.
Published: January 2008

Abstract— The photolysis of 2‐cyclopentenone has been studied by a combination of kinetic absorption spectrophotometry and time‐resolved photoacoustic calorimetry. The lifetime of the cyclopentenone triplet is strongly concentration dependent and corresponds to a value of 380 ± 75 ns at infinite dilution in acetonitrile. The biradical intermediate (or pair of isomeric biradicals) immediately preceding formation of photodimer forms with very high efficiency upon quenching of triplet cyclopentenone by a second ground state cyclopentenone molecule and has an energy of 47 kcal/mol relative to two molecules of reactant. Quenching of the cyclopentenone triplet by conjugated dienes is much slower than expected, which is the reason that early estimates of the triplet lifetime were much too short.
QUENCHING OF EXCITED TRIPLET LUMIFLAVIN BY LUMIFLAVIN RADICALS FORMED IN ITS T‐T REACTION
Authors: YOSHIMURA AKIO , OHNO TAKESHI
Published: January 2008

Abstract— Reactions of the triplet state of lumiflavin (3LF) in water adjusted at pH 7.2 were reexamined by means of a Xe‐flash photolysis and a laser photolysis. Measurements of the decay of 3LF were made on solutions of LF ranging in the concentration from 4 to 61 times 10‐6 mol/dm3. A one‐electron reduced and a one‐electron oxidized species of lumiflavin (LF‐ and LF+) were produced in the first decay stage of 3LF with a high efficiency (0.6 ± 0.1) in a bimolecular triplet‐triplet reaction. The product radicals (LFH‐ and LF+) quench 3LF very efficiently (3 ± 0.8 × 109 mol‐1dm3 s‐1) compared with LF in the ground state (> 2 × 107 dm3 mol‐1).
POLYMER BOUND PYRROLE COMPOUNDS–VI. PHOTOPHYSICAL PROPERTIES OF MONOMERIC MODELS FOR POLYSTYRENE‐BOUND PORPHYRINS
Authors: NONELL SANTIAGO , SESÉ MARÍA L. , MÁRTIRE DANIEL O. , BRASLAVSKY SILVIA E. , TRULL FRANCESC R.
Published: January 2008

Abstract— Several porphyrin esters used as models for polystyrene‐bound porphyrins have been prepared and their excited states have been studied by laser flash photolysis, IR phosphorescence of singlet molecular oxygen, O2(1Δg), and steady‐state fluorescence. The photophysical properties of the porphyrin esters in solution are affected by the presence of nitro group(s) in the chain. In this case, an important decrease in φf, φT and φδ (to ca 0.7–0.4 of the value for the parent dimethyl ester) is observed. This is mainly due to intramolecular electron‐transfer quenching [by the nitro group(s)] of the first excited singlet state of the porphyrin. The thermodynamic feasibility of this deactivation pathway has been confirmed polarographically. Quenching of the porphyrin triplet state and of O2(1Δg) by the nitro groups is negligible. The present conclusions explain also the results obtained previously for the photooxidation of bilirubin sensitized by the parent insoluble polystyrene‐bound porphyrins. In that case the photooxidation rates were correlated directly with the quantum yield of O2(1Δg) production by the sensitizer. The consequences of these results for the use of polystyrene‐bound porphyrins in sensitized photooxidation processes are discussed.
LIGHT PROMOTION OF SEED GERMINATION IN Datura ferox IS MEDIATED BY A HIGHLY STABLE POOL OF PHYTOCHROME
Authors: CASAL J. J. , SANCHEZ R. A. , DI BENEDETTO A. H. , DE MIGUEL LUCILA C.
Published: January 2008

Abstract— The duration of the far‐red light‐absorbing form of phytochrome (Pfr) of the photoreceptor pool involved in the control of seed germination was investigated for Datura ferox seeds. These seeds require both Pfr and alternating temperatures (20/30°C) to germinate. After 24 h imbibition (25°C), the seeds received pretreatment‐light pulses providing different phytochrome photoequilibria (Pfr/P), followed by a 24 h dark incubation (25°C), and test‐light pulses providing different Pfr/P immediately prior to transfer to alternating temperatures. Germination increased with increasing Pfr/P provided by the test‐light pulses, but was unaffected by the pretreatment‐light pulses. This suggests that phytochrome synthesis, phytochrome degradation and phytochrome‐mediated changes in response to phytochrome were negligible. In other experiments, red light‐pretreatment pulses were followed by dark incubations (25°C) of different duration before transfer to alternating temperatures. The proportion of Pfr remaining after the 25°C incubation period was estimated by comparing germination rates with those of seeds that received test‐light pulses of known calculated Pfr/P immediately prior to the start of the cycles of alternating temperatures. More than 80% of the Pfr established by a Pfr/P= 0.87 light pulse was present and active even after 48 h dark incubation at 25°C. Surprisingly, when a pretreatmentlight pulse providing a Pfr/P= 0.70 was given, the reduction in [Pfr] was significantly faster.

Germination of Datura ferox seeds is under the control of a highly stable (type II like) phytochrome pool. Apparently, this pool follows Pfr dark reversion to the red light‐absorbing form, the times to reach half the original Pfr pool being > 96 h or <14 h after light pulses providing Pfr/P= 0.87 or 0.70, respectively.
MOUSE SKIN PHOTOSENSITIZATION WITH BENZOPORPHYRIN DERIVATIVES AND PHOTOFRIN®: MACROSCOPIC AND MICROSCOPIC EVALUATION
Authors: RICHTER ANNA M. , YIP STEPHEN , WATERFIELD ELIZABETH , LOGAN PATRICIA M. , SLONECKER CHARLES E. , LEVY JULIA G.
Published: January 2008

Abstract— A comparative study, at both the macroscopic and microscopic level, of skin photosensitivity caused by four isomeric forms of benzoporphyrin derivative (BPD) has been carried out, and compared to effects of Photofrin®. Animals injected intravenously with BPD analogues and exposed to light 3 h later showed extensive photosensitivity. Animals receiving the monoacid derivatives of BPD (BPD‐MA and BPD‐MB) showed markedly more photosensitivity than those receiving the diacid derivatives (BPD‐DA and BPD‐DB). Animals receiving BPD analogues which were exposed to light 24 h or more later showed only minimal reactivity. Histological examination of biopsies taken after photosensitizer injection and light exposure showed extensive changes in epidermis and dermis, including epidermal erosion, degranulation of the stratum granulosum, spongiosis, depletion in cellularity and mast cell degranulation. These changes were noted to be similar to changes caused by Photofrin®.
In vitro PHOTODYNAMIC INACTIVATION OF Herpes simplex VIRUS WITH SAPPHYRINS: 22 π‐ELECTRON PORPHYRIN‐LIKE MACROCYCLES
Authors: JUDY M. M. , MAITHEWS J. L. , NEWMAN J. T. , SKILES H. L. , BORIACK R. L. , SESSLER J. L. , CYR M. , MAIYA B. G. , NICHOL S. T.
Published: January 2008

Abstract— The photodynamic inactivation of HSV‐1, a virus having a membranous envelope, with both a decaalkyl sapphyrin and its dicarboxy‐substituted analog was studied. The decaalkyl sapphyrin was as efficient in the inactivation of HSV‐1 on a per macrocycle basis as DHE, whereas the efficiency of the dicarboxy‐substituted sapphyrin was approximately two orders of magnitude less. Fluorescence studies of sapphyrin's binding to liposomes and VSV suggested that the decaalkylsapphyrin bound monomerically to cholesterol‐rich regions of the viral envelope, whereas its charged analog localized in a more polar environment.
PHOTOCHEMICAL CROSS‐LINKING OF THE CYCLIC ADENOSINE 3′, 5′MONOPHOSPHATE RECEPTOR PROTEIN TO Escherichia coli 5‐BROMOURACIL‐SUBSTITUTED DNA. ROLE OF THE EFFECTORS
Authors: KATOUZIAN‐SAFADI MEHRNAZ , BLAZY BERNADETTE , CHARLIER MICHEL
Published: January 2008

Abstract— Cyclic AMP receptor protein (CRP) is a regulatory protein implicated in the transcription of several operons in Escherichia coli. Its activity is modulated by effectors, such as cAMP or cGMP, which could induce (or not) structural changes in the protein, and activate (or not) the transcription. CRP can bind non‐specifically to DNA, and we investigated the photocross‐linking of the protein to E. coli 5‐bromouracil‐substituted DNA, in the absence and in the presence of effectors. The photochemistry of the protein alone, under the conditions used for the cross‐linking reaction, was studied. We show that tryptophyl residues are more photoreactive than tyrosyl ones. Photocross‐linking of the protein implicates only one of the two subunits, and the rate of the reaction is not modified upon cAMP binding. Binding of cGMP reduces the rate of photocross‐linking by a factor of two. These new results show that the protein in the CRP‐cGMP complex behaves differently from the free protein.
PHOTOREACTIVATION IN THE EXTREME HALOPHILIC ARCHAEBACTERIUM Halobacterium cutirubrum
Authors: EKER A. P. M. , FORMENOY L. , WIT L. E. A. DE
Published: January 2008

Abstract— Photoreactivation in the extreme halophilic archaebacterium Halobacterium cutirubrum was studied both in vivo and in vitro. Cells irradiated with ultraviolet (UV)‐fluences up to 350 J/m2 could be completely photoreactivated, indicating very efficient repair of pyrimidine dimers in UV‐irradiated DNA. Dark repair is apparently absent in Halobacterium since liquid holding under non‐growth conditions did not influence the survival of UV‐irradiated cells, while cells remained completely photoreactivable with no change in the kinetics of photoreactivation. Experiments with Halobacterium isolates of different carotenoid content indicated that carotenoids do not influence either UV‐inactivation or photoreactivation. Small differences in the rates of UV‐inactivation and photoreactivation could be assigned to the occurrence of gas vesicles. Flash experiments and the temperature dependence of photoreactivation indicated an enzymatical reaction. This was confirmed by in vitro experiments with partially purified photoreactivating enzyme. The in vivo action spectrum of photoreactivation showed a main band in the 400‐470 nm region with a maximum at 440 nm. Comparison with action spectra of other microorganisms classified the Halobacterium enzyme as a 8‐hydroxy‐5‐deazaflavin type photoreactivating enzyme.
MECHANISMS OF CITRAL PHOTOTOXICITY
Authors: Asthana Archana , Larson Richard A. , Marley Karen A. , Tuveson R. W.
Published: January 2008

Abstract—

Citral, a monoterpene aldehyde synthesized by several plant genera, has been reported to exhibit antimicrobial activity. For the first time, we report that citral exhibits UV‐A (315–400 nm) light enhanced oxygen‐dependent toxicity against a series of Escherichia coli strains differing in DNA repair and catalase proficiency. Those E. coli strains carrying a gene leading to catalase deficiency (katF) are particularly sensitized to inactivation by citral and UV‐A treatment when compared to catalase proficient strains (katF+). Consistent with these in vivo observations, citral when treated with UV‐A in vitro produces H202. When tested against Fusarium oxysporum and F. solani, fungal root pathogens of Citrus, enhanced toxicity by citral in the presence of UV‐A was demonstrated, while dark toxicity was negligible. When the plasmid pBR322 was treated with citral in the presence of UV‐A, a change in conformation from the covalently closed circular to the open circular and, ultimately, the linear form was observed. The change in plasmid conformation corresponded to a reduction in transforming activity. Holding plasmid DNA which had been treated with UV‐A light in the presence of citral at 4°C for 22 h in the dark resulted in continued degradation of the DNA and loss of transforming activity. Holding plasmid DNA treated with UV‐A or citral alone under identical conditions had no detectable effect on either plasmid conformation or transforming activity.
INTERPHOTORECEPTOR RETINOID‐BINDING PROTEIN AND α‐TOCOPHEROL PRESERVE THE ISOMERIC AND OXIDATION STATE OF RETINOL
Authors: Crouch Rosalie K. , Hazard E. Starr , Lind Thomas , Wiggert Barbara , Chader Gerald , Corson D. Wesley
Published: January 2008

Abstract—

Retinol decomposes rapidly into a number of products, including its aldehyde form, retinal, when introduced into buffer in phospholipid vesicles or ethanol. Interphotoreceptor retinoid‐binding protein at low concentrations is found to protect retinol from isomerization and oxidation. The addition of α‐tocopherol to either liposomes or an ethanolic‐buffer solution also prevents decomposition. Neither of these agents interferes with the successful regeneration of pigment with 9‐cis retinal in rod outer segment preparations or the restoration of sensitivity by retinoids in isolated rod photoreceptors.
PHOTOPHYSICAL PROBES FOR MONITORING THE ELECTRIC FIELD/MICROPOLARITY WITHIN THE FAUJASITE SUPERCAGE*
Authors: Ramamurthy V. , Sanderson D. R. , Eaton D. F.
Published: January 2008

Abstract—

The micropolariry of the supercages of zeolites is a reflection of the electric field provided by the cations present within them. The notion of polarity within the cages of X and Y zeolite does not have precisely the same meaning as in solution. In this study, pyrene, pyrenealdehyde, and para‐dimethylaminobenzonitrile have been used as photophysical probes to monitor the polarity of the zeolite interior. With pyrenealdehyde and para‐dimethylaminobenzonitrile the supercage wherein the probe is expected to reside is more polar or possesses a higher electric field when the cation is Li or Na. The polarity/electric field of the supercage decreases with cation size (Li > Na > K > Rb > Cs) and the supercage is more polar in the case of X zeolites than in Y zeolites. The results with pyrene are generally consistent with those with the other two probes. However, pyrene is unable to sense the difference between Li. Na and other cations.
SINGLET OXYGEN QUANTUM YIELD OF SULFUR AND SELENIUM ANALOGS OF PSORALEN
Authors: Seret A. , Piette J. , Jakobs A. , Vorst A. Van de
Published: January 2008

Abstract—

The quantum yield of singlet oxygen production by eight newly synthesized sulfur and selenium analogs of psoralen irradiated with UV‐A (366 nm) has been determined in CCI, with the help of the steady state luminescence technique. The new psoralen derivatives are generally better singlet oxygen producers than psoralen itself. In particular, the replacement of selenophene for furan and/or of thiopyrone for pyrone induces an important enhancement of the singlet oxygen quantum yield.
DIHYDROXY‐CAROTENOID LIPOSOMES INHIBIT PHOTOTOXICITY IN Paramecium caudatum
Authors: Rich Marvin R. , Strulle Ronald de , Ferraro Greg , Brody Steven S.
Published: January 2008

Abstract—

The phototoxic effects of hematoporphyrin derivative, using Paramecium cuudatum as a model system, are significantly reduced in the presence of carotenoid‐containing liposomes. Multilam‐melar large or small unilammelar vesicles, containing specific carotenoids, were effective in protecting the organism, whether administered exogenously in the bathing solution, or via incubation of paramecia in starved culture media containing carotenoid liposomes. The effectiveness of the carotenoids as inhibitors of phototoxic effects was found to depend on the mode of administration, with small unilammelar being more effective than multilammelar large vesicles for all carotenoids tested. Small unilammelar vesicles containing the dihydroxy‐carotenoids zeaxanthin or astaxanthin afforded the greatest protection in both exogenous and endogenous studies. The results of this study suggest that carotenoid efficacy may be determined, in part, by the environment of the carotenoid molecules.
APPLICATION OF TIME‐RESOLVED DIFFUSE REFLECTANCE TECHNIQUES IN STUDIES OF REACTION INTERMEDIATES IN SUSPENSIONS OF BACILLUS SUBTILIS
Authors: BERINSTAM A.B. , SCAIANO J.C. , BOHNE C. , MALENFANT P.R.L. , SPROIT G.D.
Published: January 2008

Short lived reaction intermediates such as triplet stam and free radicals can be detected in vivo using laser photolysis techniques with time‐resolved diffuse reflectance detection. This novel approach is illustrated for bacterial suspensions of Bacillus subtilis.
LIGHT‐GROWN PLANTS OF THE CUCUMBER LONG HYPOCOTYL MUTANT EXHIBIT BOTH LONG‐TERM AND RAPID ELONGATION GROWTH RESPONSES TO IRRADIATION WITH SUPPLEMENTARY FAR‐RED LIGHT
Authors: Smith Harry , Turnbull Matthew , Kendrick Richard E.
Published: January 2008

Abstraet—

Seedlings of wild type (WT) and the lh mutant of Cucumis sativus were grown in white light and given supplementary far‐red radiation either to the whole plant, or via fiber‐optic probes directed at the apical region of the hypocotyl. In both WT and mutant seedlings, reducing the ratio of red to far‐red radiation resulted in significant increases in extension growth. Direct measurement of extension rate by transducer techniques revealed that the mutant seedlings responded to additional far‐red radiation by an increment in extension rate that was equivalent to that observed with the WT seedlings. Assuming that the lh mutant is deficient in phytochrome B (Kendrick and Nagatani, The Plant Journal1: 133–139, 1991), these results indicate that although phytochrome B clearly has an important role in the induction of the shade avoidance syndrome, it is unlikely to be the sole responsible receptor.
THE TEMPERATURE DEPENDENCE OF Pfr ACTION GOVERNS THE UPPER TEMPERATURE LIMIT FOR GERMINATION IN LETTUCE
Authors: Fielding Anthony , Kristie David N. , Dearman Peter
Published: January 2008

Abstract—

In most cultivars of lettuce (Lactuca saliva L,), red light acting through the red/far‐red reversible phytochrome system promotes full germination within the20–30°C range, but at progressively higher temperatures germination declines sharply. The relationship between this upper ternperature limit for germination and the temperature dependence of phytochrome action was investigated in Grand Rapids lettuce. In fresh seeds the GT50 (temperature giving half maximal germination) was ca 29–30°C. In these seeds, escape from far‐red reversibility did not occur at 35°C, a temperature above the GT50, but occurred rapidly at 27°C, a temperature below the upper limit. Increasing periods of dark pretreatment at high temperature (35°C) or increasing concentrations of the germination inhibitor coumarin caused a progressive decline in the GT50, Escape from photoreversibility did not occur at 27°C in seeds in which the GT50 had been reduced to less than 25°C by coumarin or by prolonged high temperature pretreatment. These results indicate that there is a close correlation between the position of the upper temperature limit for germination, and the temperature dependence of phytochrome action. We conclude that factors that alter the upper temperature limit for germination do so by changing the temperature dependence of phytochrome action.
PHYTOCHROME‐MEDIATED RAPID CHANGES IN THE LEVEL OF PHOSPHOINOSITIDES IN ETIOLATED LEAVES OF Zea mays
Authors: Guron Kuljeet , Chandok Meena R. , Sopory Sudhir K.
Published: January 2008

Abstract—

The role of the active form of phytochrome in Zea mays on the polyphosphoinositide cycle was studied. As little as 15 s of red irradiation of etiolated leaves immediately increased the level of phosphatidylinositol bisphosphate (PIP2) 3–6‐fold compared to unirradiated leaves. The elevated level of PIP2 decreased with longer red irradiations up to 5 min, but remained higher than in unirradiated leaves. The level of PIP2 decreased if red irradiation was followed by far‐red irradiation. Far‐red alone had no effect. Levels of phosphatidylinositol phosphate (PIP) and phosphatidylinositol did not change significantly. Since red irradiation significantly changed PIP, but not PIP, photocontrol appears to be at the PIP kinase and phospholipase level. In related studies of the effect of light on phospholipids, 5 min of red irradiation induced significant decreases in phosphatidylcholine and phosphatidylethanola‐mine.