bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractTriplet‐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

AbstractThe 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

AbstractNanosecond (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

AbstractThe 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

AbstractAlthough 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

AbstractPrevious 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

AbstractThe 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).
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.
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.
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.