bluuebunny/crossref_metadata_2025 huggingface dataset:
CELLULAR DELIVERY AND RETENTION OF PHOTOFRIN: II. THE EFFECTS OF HUMAN versus MOUSE AND BOVINE SERUM
Authors: Korbelik Mladen
Published: January 2008

Abstract—

The effects of human serum (HS), mouse serum (MS) and fetal bovine serum (FBS) on cellular delivery and retention of Photofrin were examined using human lung tumor cells (A.549) cultured in vitro. The results show that these three kinds of sera exhibit substantial differences in: (i) degree of inhibition of Photofrin cellular uptake, (ii) retention capacity of Photofrin delivered to the cells in their presence and (iii) efficacy of promoting the clearance of Photofrin from the cells. It is suggested that these differences originate from unequal interaction of each of the sera with Photofrin material, which in turn is the consequence of variability in composition and in the levels of serum proteins in HS, MS and FBS. The highest degree of Photofrin disaggregation and competitive binding of its constituents was attributed to HS. The lowest degree of Photofrin disaggregation, and the competitive binding limited mostly to monomeric porphyrin forms was implicated for FBS. For MS, the spectroscopic and cellular data indicated a lesser degree of Photofrin disaggregation than with HS, with little if any consequence in Photofrin retention characteristics. The implication of this comparative analysis is that in vitro studies using FBS may underestimate the extent of interaction of Photofrin with serum proteins in humans, and overestimate the retention capacity of the photosensitizer in human tissues. Studies in vivo using a mouse model may also underestimate the degree of disaggregation of Photofrin in human circulation, and give different photosensitizer tissue retention levels than in humans.
REVERSIBLE PHOTOCYCLOADDITION OF A 4′,5′‐DIHYDROPSORALEN DERIVATIVE WITH THYMINE
Authors: Decout Jean‐Luc , Lhomme Jean
Published: January 2008

Abstract—

The photocycloaddition reaction between a 4′,5′‐dihydropsoralen derivative and thymine was studied in solution using a synthetic bichromophoric model 8 in which the two rings are associated by a tetramethylene chain. In water this model molecule exhibits intramolecular ring‐ring stacking interactions as evidenced by UV and NMR spectroscopies. Irradiation at 365 nm at usual concentrations ( 5.10−‐4M) leads exclusively to a regio‐ and stereo‐selective dimerization reaction involving the 3,4 double bonds of the psoralen moities. Extreme dilutions (ca2.10−‐5M) were necessary to observe the intramolecular reaction which results in the exclusive formation of a 3,4cb‐antiadduct. This reaction is completely reversed by irradiation at 254 nm. These results are discussed with regard to the behavior of the homologous models in which the furan part of the psoralen ring is not hydrogenated, These latter compounds also lead exclusively to a 3,4cis‐antiadduct. It appears that saturation of the furan ring increases strongly the quantum yield of the photaddition at 365 nm (0.01 → 0.18) and that the triplet excited state of the 4′,5′‐dihydropsoralen is involved in the photoaddition.
MEROCYANINE 540‐SENSITIZED PHOTOINACTIVATION OF LEUKEMIA CELLS: EFFECTS OF DOSE FRACTIONATION
Authors: Qiu Kang , Sieber Fritz
Published: January 2008

Abstract—

The differential sensitivity to merocyanine 540 (MC540)‐sensitized photoirradiation of leukemia cells, selected solid tumor cells, and normal pluripotent hematopoietic stem cells has been successfully exploited for the extracorporeal purging of simulated autologous remission bone marrow grafts. In this communication, we compare the effects of fractionated vs continuous irradiation upon the MC540‐sensitized photoinactivation of L1210 and K562 leukemia cells. Exposure to MC540 (15 μg/mL) and fractionated doses of white light inactivated fewer in vitro clonogenic cells than exposure to an equivalent dose of continuous irradiation, provided the irradiation doses were small (8.1–16.2 kJ/m2) and spaced 1–2 h apart. The dye‐sensitized photoinactivation of leukemia cells was enhanced when cells were stored at 4°C instead of 37°C between irradiation periods, most likely in part because the cells were unable to repair sublethal photodynamic damages at the lower temperature. These data suggest that cells can recover from sublethal damage inflicted by the plasma membrane‐active photosensitizer, MC540.
THE EFFECT OF ORGANIC NITRATES IN PHYTOCHROME‐CONTROLLED GERMINATION OF Paulownia tomentosa SEEDS
Authors: Grubišić D. , Giba Z. , Konjević R.
Published: January 2008

Abstract—

The long light irradiation requirement in Paulownia tomentosa (empress tree) seeds can be substituted by organic nitrates such as nitroglycerine, isosorbide di‐ and mononitrate, and pentaerythri‐tyl tetranitrate and a pulse of red light (5 min). The most effective was nitroglycerine (0.1 mM). Its effect depended on the time of application, i.e. a simultaneous presence of Pfr and these compounds was required. The effect decreased with delayed time of application after red light pulse. In seeds imbibed in nitroglycerine, an escape from far‐red light reversible action was similar to that obtained for seeds which can be induced to germinate by a brief exposure to red light. However, the application of nitroglycerine to seeds after a far‐red light pulse was ineffective. The effectiveness of organic nitrates also depended on the number of nitro groups in the compound. Isosorbide mononitrate was less effective than isosorbide dinitrate. Substances with structures similar to nitroglycerine, such as glycerol and glyceryl triacetate, in combination with the pulse of red light, failed to reduce the long light requirement.
INACTIVATION OF GRAM‐NEGATIVE BACTERIA BY PHOTOSENSITIZED PORPHYRINS
Authors: Nitzan Yeshayahu , Gutterman Mina , Malik Zvi , Ehrenberg Benjamin
Published: January 2008

Abstract— Photosensitization of Escherichia coli and Pseudomonas aeruginosa cells by deuteroporphyrin (DP) is shown to be possible in the presence of the polycationic agent polymyxin nonapeptide (PMNP). Previous studies established complete resistance of Gram‐negative bacteria to the photodynamic effects of porphyrins. The present results show that combined treatment of E. coli or P. aeruginosa cultures with DP and PMNP inhibit cell growth and viability. No antibacterial activity of PMNP alone could be demonstrated and cell viability remained unchanged. Spectroscopically, PMNP was found to bind DP, a mechanism which probably assists its penetration into the cell's membranes. Insertion of DP into the cells was monitored by the characteristic fluorescence band of bound DP at 622 nm. Binding times were 5–40 min and the extent of binding increased with decreasing the pH from 8.5 to 6.5. DP binding constants, as well as the concentrations of PMNP which were required for maximal effect on the various Gram‐negative bacteria, were determined fluorometrically. By the treatment of DP, PMNP and light the growth of E. coli and P. aeruginosa cultures was stopped and the viability of the culture was dramatically reduced. Within 60 min of treatment the survival fraction of E. coli culture was 9 × 10–6 that of P. aeruginosa was 5.2 × 10–4. Electron microscopy depicted ultrastructural alterations in the Gram‐negative cells treated by DP and PMNP. The completion of cell division was inhibited and the chromosomal domain was altered markedly.
ALTERNATIVE MEASURES OF PHOTOSYSTEM II ELECTRON TRANSFER INHIBITION IN ANTHRAQUINONE‐TREATED CHLOROPLASTS
Authors: Karukstis K. K. , Moision R. M. , Johansen S. K. , Birkeland K. E. , Cohen S. M.
Published: January 2008

Abstract—We have previously used chlorophyll fluorescence measurements atFmaxconditions (i.e. with Photosystem II electron acceptor QAreduced) to monitor the action of 9,10‐anthraquinones on photosynthetic electron transport in plant chloroplasts. The present investigation employs two additional techniques to characterize the extent of electron transport inhibition induced by the addition of substituted anthraquinones to the suspending medium of spinach chloroplasts. Results are presented for spectrophotometric assays of the rate of electron transfer to an exogenous electron acceptor, 2.6‐dichloroindophenol (DCIP) and for electrochemical determinations of the rate of oxygen evolution in anthraquinone‐treated chloroplasts. In general, amino‐substituted anthraquinones are ineffective inhibitors, maintaining electron transfer rates to DCIP at levels ranging from 50 to 90% of normal rates and yielding rates of O2evolution averaging at 70% of the rate in untreated chloroplasts. In contrast, hydroxy‐substituted anthraquinones efficiently block Photosystem II electron transport, resulting in low rates of DCIP photoreduction ranging from 0 to 20% of normal values and reducing O2evolution rates to an average of 30% of the rate observed for untreated chloroplasts. Relative rates of DCIP photoreduction for anthraquinone‐treated chloroplasts show a strong linear correlation with the reported relativeFmaxchlorophyll fluorescence intensities. Relative O2evolution rates are observed to correlate with the Stern‐Volmer fluorescence quenching parameterKsv. We suggest that slight differences in the extent of inhibitory activity of an anthraquinone as measured by the three techniques are consistent with certain known Photosystem II heterogeneities. The similarities in relative rankings of inhibitory effects for the 9,10‐anthraquinones, however, demonstrate that the three techniques employed (measurements ofFmaxchlorophyll fluorescence, DCIP photoreduction rates, and O2evolution rates) are alternative assays of anthraquinone‐induced Photosystem II electron transport inhibition.
STRAND BREAKAGE IN POLY(C), POLY(A), SINGLE‐AND DOUBLE‐STRANDED DNA INDUCED BY NANOSECOND LASER EXCITATION AT 193 nm*
Authors: Görner Helmut , Wala Malgorzata , Schulte‐Frohlinde Dietrich
Published: January 2008

Abstract—Single‐ and double‐stranded calf thymus DNA and two polynucleotides (0.4 mM) were studied in aqueous solution at pH ≅ 7 using pulsed, 20 ns laser excitation at 193 nm. Monophotonic ionization of the nucleic acids is suggested from the linear dependences of the concentration of ejected electrons and the number of single‐ and double‐strand breaks (ssb, dsb, respectively) on laser intensity (IL) in the range (0.2–3) × 106W cm‐2. The quantum yields of formation of hydrated electrons (φe‐) and ssb and dsb (φSSband φdsb) are therefore independent ofIL. In contrast, under 248 nm excitation these quantum yields increase linearly withILunder otherwise comparable conditions. Nevertheless, several effects and mechanistic implications are analogous using Λexc= 193 and 248 nm. For polycytidylic acid, poly(C), in Ar‐saturated solution for example, the efficiency of ssb per radical cation (ηRC=φssb/φe‐) is similar to the efficiency of ssb per OH radical (ηOH). For polyadenylic acid, poly(A), and single‐ and double‐stranded DNA ηRC(Λexc= 193 nm) is significantly smaller than ηOH. The ratio φssb(N2O)/φssb(Ar) is =2 for poly(C), =4 for poly(A) and =10 for DNA; the conversion of hydrated electrons into OH radicals in N2O‐saturated solution and smaller ηRCthan ηOHvalues in the case of DNA account for these results. For double‐stranded DNA φdsbdoes not depend onILbut increases linearly with the dose, indicating an accumulative effect of two ssb to generate one dsb. The critical distance for this event is 60–85 phosphoric acid diester bonds.
ALTERED PTERIN PATTERNS IN PHOTOBEHAVIORAL MUTANTS OF Phycomyces blakesleeanus*
Authors: Hohl Norbert , Galland Paul , Senger Horst
Published: January 2008

Abstract— Pterins were extracted with methanol from sporangiophores of the lower fungus Phycomyces blakesleeanus and separated and identified by high performance liquid chromatography (HPLC) with fluorescence detection. The following pterins were found and identified for the wild‐type strain NRRL1555: carboxypterin (6.7 × 10‐6M), neopterin (4.2 × 10‐7M), xanthopterin (5.3 × 10‐6M), biopterin (3.9 × 10‐7M), pterin (9.1 × 10‐7M), and 6,7‐dimethylpterin (1.2 × 10‐6M). The HPLC elution profiles of the wild type were compared to a set of phototropism mutants (genotype mad) with specific defects in the light‐transduction pathway. The mutant profiles were qualitatively similar to those of the wild type. Quantitative differences were, however, discerned for madA, madC, and madH mutants. The madA mutation was associated with increased amounts of biopterin and 6,7‐dimethylpterin and a reduction of neopterin, pterin, xanthopterin, and unidentified pterins eluting at 14–18 min. The stimulatory effect of the madA mutation on biopterin and 6,7‐dimethylpterin appears to be compensated by a secondary mutation (pde) which is responsible for the loss of 75% of adenosine 3',5'‐cyclic monophosphate (cAMP)‐phosphodiesterase activity. In a madA pde double mutant the amounts of biopterin and 6,7‐dimethylpterin fell below the wild‐type level. These results suggest that an increased level of endogenous cAMP represses the biosynthesis of these pterins. The madC mutation increased the amounts of biopterin and xanthopterin and that of the unidentified pterins which could be derivatized to carboxypterin. Single madB mutations had, compared to the wild type, two times higher amounts of biopterin and two times lower amounts of neopterin. In a madH mutant the identified pterins occurred at normal concentrations while the total pool of pterins and of unidentified pterins were elevated. Complex changes of the pterin pattern were obtained in various double mad‐mutants suggesting that some mad gene products synergistically control the pterin content. The results of this and the accompanying paper (Hohl et al., 1992, Photochem. Photobiol.55) show that some of the mad genes affect pterin as well as flavin levels in Phycomyces. We propose that photoreception of Phycomyces requires a balanced and precisely controlled ratio of endogenous pterins and flavins. For some of the mutants the relative excess of certain pterins may cause the known sensitivity changes in the near‐UV.
ALTERED FLAVIN PATTERNS IN PHOTOBEHAVIORAL MUTANTS OF Phycomyces blakesleeanus*
Authors: Hohl Norbert , Galland Paul , Senger Horst
Published: January 2008

Abstract— Flavins were extracted from sporangiophores of the lower fungus Phycomyces blakesleeanus and identified by HPLC with fluorescence detection. In the wild‐type strain NRRL1555 they were found to be present at the following concentrations: riboflavin (5.5 × 10‐6M), flavin mononucleotide (FMN) (4.0 × 10‐6M) and flavin adenine dinucleotide (1.4 × 10‐6M). The HPLC elution profiles of the wild type were compared to a set of behavioral mutants (genotype mad) with specific defects in their light‐transduction pathway. The photoreceptor mutants C109 (madB), C111 (madB) and L1 (madC) had normal amounts of flavins. The most prominent changes were found in single mutants with a defective madA gene which contained about 25% of riboflavin and about 10% of FMN and FAD normally found in the wild type. A hypertropic mutant with a defective madH gene contained instead 80% of riboflavin and 120% of FMN and FAD. The double mutant L52 (madA madC) and the triple mutant L72 (madA madB madC) had normal amounts of FAD and FMN. This indicates that the madC mutation, which itself causes loss of light sensitivity and which affects the near‐UV/blue‐light receptor (Galland and Lipson, 1985, Photochem. Photobiol.41, 331–335) functions as a restorer of the flavin content in a genetic madA background. The double mutant L51 (madA madB) had about 40% of FMN and FAD, suggesting that the madB mutation functions as a partial restorer of flavin content. The photogravitropic thresholds (450 nm) reported for the wild type and the madA and madH mutants were positively correlated to the endogeneous concentrations of FMN and FAD. The endogenous concentrations of riboflavin appeared to be irrelevant for the photogravitropic sensitivity, because exogenously added riboflavin did not restore the sensitivity of madA mutants. Our results suggest that FMN, FAD or other flavins derived from riboflavin are part of the near‐UV/blue‐light receptor system of Phycomyces and that they possibly act as receptor pigments.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID BILAYER VESICLES: GENERATION OF PROTON GRADIENTS ACROSS THE BILAYER COUPLED TO QUINONE REDUCTION AND HYDROQUINONE OXIDATION
Authors: Zhao Zhan‐Gong , Tollin Gordon
Published: January 2008

Abstract— A chlorophyll‐containing small unilamellar lipid bilayer vesicle system with a sulfonated quinone molecule (MQS) in one aqueous compartment and a sulfonated hydroquinone molecule (H2QS) in the other has been investigated, using laser flash photolysis and steady‐state irradiation, as a means of storing light energy in the form of a proton gradient across the lipid bilayer. Under optimal conditions, an efficiency of 39% based on the chlorophyll triplet state quenched has been achieved for vectorial electron transfer across the bilayer; this corresponds to a quantum yield of 23% based on absorbed photons. As a consequence of irradiation by a single laser flash, 0.2 μM of protons were taken up by quinone reduction (MQS → H2MQS) in the outer compartment. The same number of protons were released in the inner compartment by hydroquinone oxidation (H2QS → QS). Since the volume occupied by the vesicles was only 1/1000 of the total volume of the sample, the local concentration of protons in the inner compartment was 1000 times larger (i.e.≅ 200 μM), resulting in the generation of an appreciable proton gradient across the bilayer.
QUANTUM YIELDS AND KINETICS OF THE PHOTOBLEACHING OF HEMATOPORPHYRIN, PHOTOFRIN II, TETRA(4‐SULFONATOPHENYL)‐PORPHINE AND UROPORPHYRIN
Authors: Spikes John D.
Published: January 2008

Abstract—Porphyrins used as sensitizers for the photodynamic therapy (PDT) of tumors are progressively destroyed (photobleached) during illumination. If the porphyrin bleaches too rapidly, tumor destruction will not be complete. However, with appropriate sensitizer dosages and bleaching rates, irreversible photodynamic injury to the normal tissues surrounding the tumor, which retain less sensitizer, may be significantly decreased. This paper surveys the quantum yields and kinetics of the photobleaching of four porphyrins: hematoporphyrin (HP), Photofrin II (PF II), tetra(4‐sulfonatophenyOporphine (TSPP) and uroporphyrin I (URO). The initial quantum yields of photobleaching, as measured in pH 7.4 phosphate buffer in air, were: 4.7 × 10‐5, 5.4 × 10‐5, 9.8 × 10‐5, and 2.8 × 10‐5for HP, PF II, TSPP and URO respectively; thus, the rates of photobleaching are rather slow. Low oxygen concentration (2 μM) significantly reduced the photobleaching yields. However, D2O increased the yields only slightly, and the singlet oxygen quencher, azide, had no effect, even at 0.1M.Photosensitizing porphyrins in body fluids, cells and tissues may be closely associated with various photooxidizable molecules and electron acceptors and donors. Therefore, selected model compounds in these categories were examined for their effects on porphyrin photobleaching. A number inhibited and/or accelerated photobleaching, depending on the compound, the porphyrin and the reaction conditions. For example, 1.0 mMfurfuryl alcohol increased the photobleaching yields of HP and URO more than 5‐fold, with little effect on PF II or TSPP. In contrast, the electron acceptor, methyl viologen, increased the photobleaching yield of TSPP more than 10‐fold, with little accelerating effect on the other porphyrins. These results suggest that the mechanism(s) of the photobleaching of porphyrin photosensitizers in cells and tissues during PDT may be complex.
DNA ASSOCIATED WITH THE CELL MEMBRANE IS INVOLVED IN THE INHIBITION OF THE SKIN REJECTION RESPONSE INDUCED BY INFUSIONS OF PHOTODAMAGED ALLOREACTIVE CELLS THAT MEDIATE REJECTION OF SKIN ALLOGRAFT
Authors: Perez Maritza I. , Yamane Yasuhiro , John Lori , Gasparro Francis P. , Edelson Richard L.
Published: January 2008

Abstract— Cell membrane DNA (cmDNA) is a form of DNA located on the surface of human and murine T‐cells. It has recently been characterized as a target for photomodification by 8‐methoxypsoralen (8‐MOP) and long‐wave ultraviolet light (UV‐A). Whereas 8‐MOP itself is biologically inert, photoactivated 8‐MOP is covalently bound to pyrimidine bases in DNA. We have investigated the possible involvement of cmDN A photomodification in the induction of the suppression of skin allograft rejection in BALB/c mice preimmunized with 8‐MOP/UV‐A photodamaged alloreactive cells which mediates this allograft rejection. This suppression is demonstrated by inhibition of delayed‐type hypersensitivity (DTH) and mixed leukocyte culture (MLC) responses. Splenocytes from BALB/c mice undergoing rejection of CBA/j skin graft which contained an expanded population of the effector T lymphocytes that mediate the rejection were treated with DNAse to remove cmDNA before or after treatment with 8‐MOP and UV‐A prior to infusion into naive BALB/c recipients. Mice that received pretreated effector cells were tested for MLC responses to CBA/j or B10 alloantigens before and after the DTH response. The DTH response of all groups of pretreated BALB/c mice to the relevant alloantigen was specifically suppressed as compared with the response of control mice. However, adoptive transfer of the suppression of the DTH response was optimally demonstrable only in syngeneic recipients of cells from donor mice treated with photodamaged alloreactive cells. Also, splenocytes from BALB/c mice immunized with photodamaged alloreactive cells demonstrated highly significant hyporesponsiveness and suppression of the MLC response of naive mice to the relevant alloantigen in the case of the primary MLC response, and to both alloantigens in the secondary MLC response which was totally eliminated by prior pretreatment of these effector cells with DNAse. Therefore, it appears that the suppression of the DTH response can be induced by pretreatment of the effector cells with DNAse and/or 8‐MOP and UV‐A but is adoptively transferable optimally only from mice which are recipients of photodamaged alloreactive cells. Moreover, the effectiveness of this treatment is decreased by prior removal of cmDNA from these cells. The presence of cmDNA is necessary for induction of suppression of the primary and secondary MLC responses in mice treated with photodamaged cells of allograft rejection.
RESOLUTION ENHANCEMENT AND DECONVOLUTION INTO VIBRONIC BANDS OF THE FLUORESCENCE AND ABSORPTION SPECTRA IN THE RED REGION OF DILUTE SOLUTIONS OF CHLOROPHYLL a IN VARIOUS SOLVENTS
Authors: Bélanger Daniel , Leblanc Roger M. , Kurucsev Tomas
Published: January 2008

Abstract— The fluorescence spectra of chlorophyll a in less than 10–6 mol dm‐3 solutions of benzene, toluene, tetrahydrofurane, EPA and ethanol were determined at both room temperature and at 77 K. Resolution enhancement using Fourier transform methods revealed the presence of vibronic bands with essentially solvent‐invariant separation between their origins; this was confirmed by the quantitative deconvolution of the spectra into Gaussian bands. It was concluded that the fluorescence is due to a single spectroscopically distinct species. The absorption spectra in the above solvents include a band absent from the fluorescence spectra which, from its position and intensity, may be identified as the longest wavelength X‐polarized electronic transition of chlorophyll a. Differences observed between the shapes of the low‐and high‐temperature absorption spectra may be attributed primarily to the narrowing of bandwidths with decreasing temperature and to intensity redistribution within the bands; the apparent increase in the integrated intensity on cooling the solutions appears to be due largely to the increase in the volume concentration of the solute as a result of solvent contraction.
A VALIDATION STUDY OF THE ROBERTSON‐BERGER METER
Authors: Kennedy Brian C. , Sharp William E.
Published: January 2008

Abstract— An evaluation of the Robertson‐Berger meter was done in order to address the question of whether instrumental and calibration factors can cause what might be interpreted as a change in the ground level solar ultraviolet‐B (UV‐B) flux. The evaluation consisted of reviewing information about the instrumentation and components in the published literature, a review of the records and procedures in both operations and calibrations, and examination of two instruments including temperature tests of them. It is shown that the instrument is basically stable and that the calibration procedures did not support data drift. There is a slight dependance of the two instruments upon temperature, 0.3°C/y and 0.6°C/y, which is not sufficient to lead to the reported UV‐B trends of the order of 0.7 %/y. There is negligible temperature drift in the control electronics.
INVARIABLE TRAPPING TIMES IN PHOTOSYSTEM I UPON EXCITATION OF MINOR LONG‐WAVELENGTH‐ABSORBING PIGMENTS
Authors: Trissl H.‐W. , Hecks B. , Wulf K.
Published: January 2008

The primary charge separation in photosystem (PS) I was measured on stacked pea thylakoids using the light‐gradient photovoltage technique. Upon 532 nm excitation with picosecond flashes, a trapping time of 80 ± 10 ps for PS I was found, which is in close agreement with literature data. In the wavelength range between 700 nm and 717 nm the trapping time was essentially the same although there was an indication for a slight decrease. To further analyze the data we performed a spectral decomposition of PS I with Chiaandbsolvent spectra. This procedure yielded bands at around 682 nm, 690 nm, 705 nm and 715 nm. According to this decomposition, a selective excitation of long‐wavelength antenna pigments at wavelengths Λ > 710 nm is possible, because the direct excitation of the main 682 nm band is small compared to the excitation of the two most red‐shifted bands. The invariability of the trapping time of the excitation wavelength suggests thermal equilibration of the excitation energy among all antenna pigments according to their excited state energy levels and their abundance. Hence, we conclude that trapping in PS I is essentially rate‐limited by the primary charge separation much as it is the case in PS II. Then, according to our spectral decomposition in a time constant of2–3 ps is predicted for the primary charge separation in PS I.
FLUORESCENT POLYENE ALIPHATICS AS SPECTROSCOPIC AND MECHANISTIC PROBES FOR BACTERIAL LUCIFERASE: EVIDENCE AGAINST CARBONYL PRODUCT FROM ALDEHYDE AS THE PRIMARY EXCITED SPECIES
Authors: CHO KI‐WOONG , TU SHIAO‐CHUN , SHAO RUXIN
Published: January 2008

The fluorescent α‐parinaric acid (α‐PAC) and β‐parinaric acid (β‐PAC) were converted to the corresponding aldehydes and alcohols all of which exhibited absorption and fluorescence properties closely resembling those of the parent acids. α‐PAC and β‐PAC each binds to luciferase in competition with aldehyde. The hydrophobic nature of the aldehyde site was indicated by the enhanced fluorescence quantum yields of the bound α‐PAC and β‐PAC. These two polyene acids and the β‐parinaryl alcohol were shown to stabilize the luciferase flavin‐peroxide intermediate. α‐Parinaraldehyde (α‐PAD) and bt‐parinaraldehyde (β‐PAD) were active substrates for Vibrio harveyi and Vibrio fischeri luciferases and, for the former enzyme, exhibited Km, values similar to and quantum yields about20–30% as those for decanal and dodecanal. For the V. harveyi luciferase with reduced FMN as a co‐substrate, the α‐PAD‐ or β‐PAD‐initiated luminescence was indistinguishable from the normal emission obtained with octanal (γmax 495 nm) showing no additional 430‐nm component correlatable with emission from excited α‐PAC or β‐PAC. In reactions using reduced 2‐thioFMN for V. harveyi luciferase or reduced FMN for V. fischeri luciferase plus yellow fluorescent protein, the replacement of octanal by β‐PAD again resulted in no additional 430‐nm emission. The lack of any emission correlatable with excited α‐PAC, β‐PAC, or equivalent carbonyl product was not due to the quenching of the polyene moiety by chemical transformation, binding to luciferase, or a 100% energy transfer to the flavin 4a‐hydroxide emitter. These results strongly favor singlet state of flavin 4a‐hydroxide rather than singlet or triplet carbonyl product from aldehyde as the primary excited species in the normal luciferase reaction in the absence of any additional fluorescent protein.
MODULATION AND DYNAMICS OF PHASE PROPERTIES IN PHOSPHOLIPID MIXTURES DETECTED BY LAURDAN FLUORESCENCE*
Authors: Parasassi Tiziana , Ravagnan Giampietro , Rusch Ruth M. , Gratton Enrico
Published: January 2008

Steady‐state and dynamic fluorescence properties of 6‐lauroyl‐2‐dimethylaminonaphthalene (Laurdan) have been used to ascertain the coexistence of separate phase domains and their dynamic properties in phospholipid vesicles composed of different mole ratios of dilauroyl‐ and dipalmitoyl‐phosphatidylcholine (DLPC and DPPC, respectively). The recently introduced generalized polarization together with time‐resolved emission spectra have been utilized for detecting changes. The results indicate the coexistence of phospholipid phase domains in vesicle compositions in the range between 30 mol% and 70 mol% DPPC in DLPC. Below and above these concentrations a homogeneous phase is observed, with averaged properties. In the case of coexisting phase domains, the properties of each individual phase are largely influenced by the presence of the other phase. Implications on fluctuations between the coexisting phases and on the size and shape of domains are discussed.
FLUORESCENCE INVESTIGATIONS OF ALBUMIN FROM PATIENTS WITH FAMILIAL DYSALBUMINEMIC HYPERTHYROXINEMIA*
Authors: Dughi Coco , Bhagavan Nadhipuram V. , Jamesont David M.
Published: January 2008

Familial dysalbuminemic hyperthyroxinemia (FDH) is an autosomal dominant syndrome in which clinically euthyroid patients have elevated total thyroxine levels. These high serum thyroxine levels are traceable to altered binding of thyroxine to the patient's albumin. Albumin from FDH patients and normal volunteers have been purified. Reverse‐phase and ion‐exchange high performance liquid chromatography and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis on the FDH‐human serum albumin (HSA) samples show a single band that comigrates with normal HSA. In both protein solutions the intrinsic fluorescence, upon 280 nm excitation, is predominantly due to the single tryptophan residue. The quantum yield of this intrinsic fluorescence in the FDH‐HSA solutions is, however, reduced relative to that of HSA. Furthermore, the “average” lifetime value of the tryptophan emission in the FDH‐HSA sample is less than that of normal HSA, consistent with its reduced quantum yield. The binding of thyroxine to both albumins effectively quenches the tryptophan emission probably via a nonradiative energy transfer mechanism. Time‐resolved data suggest that the albumin from the dysalbuminemic patients is actually an approximately equimolar mixture of normal HSA and FDH‐HSA indicative of heterologous expression. Quenching of the intrinsic HSA and FDH‐HSA fluorescence by serial additions of thyroxine showed enhanced quenching of FDH‐HSA relative to HSA at any T4 to albumin mole ratio, therefore supporting earlier reports of increased thyroxine affinity to FDH‐HSA.
THE EFFECT OF MERCURIC IONS ON THE EXCITED STATES OF DNA‐INTERCALATED ETHIDIUM BROMIDE
Authors: Atherton Stephen J. , Beaumont Paul C.
Published: January 2008

The first excited triplet state of DNA‐intercalated ethidium bromide is produced with a quantum yield of 0.010.002 on irradiation at 532 nm. A difference extinction coefficient of 1.50.2103 m2 mol−1 is measured for the triplet state at 380 nm. Mercuric ions quench the first excited singlet state of DNA‐intercalated ethidium bromide via induced spin orbit coupling to give an increased yield of ethidium triplet states. The same mercuric ion that quenches the singlet state then quenches the triplet state, via the same mechanism, with a rate constant of ca 3.5103 s−1. An upper limit for the rate of detachment of Hg2+ from its binding site in DNA may be fixed at ca 103 s−1.
BENZO‐ and TETRAHYDROBENZO‐PSORALEN CONGENERS: DNA BINDING and PHOTOBIOLOGICAL PROPERTIES
Authors: Gia O. , Mobilio S. , Palumbo M. , Pathak M. A.
Published: January 2008

Four new benzo‐ and tetrahydrobenzo‐psoralens have been examined in their reversible interaction toward DNA and in their DNA‐photobinding properties. These compounds were also examined for their ability to produce singlet oxygen and in vivo skin photosensitization reaction. Fluorescence and equilibrium dialysis measurements show that the complexation ability of benzoderivatives is remarkably high. Binding is less effective in the case of the tetrahydrocongeners. All compounds photoreact quite effectively to DNA. The photoadducts were obtained by enzymatic hydrolysis of drug‐modified DNA and were characterized by high performance liquid chromatographic elution techniques. The 3,4 position represents the unique photoreactive site for benzopsoralens. Denaturation‐renaturation experiments confirm that the benzoderivatives are purely monofunctional, while the tetrahydrocongeners form interstrand cross‐links, even though to a remarkably lesser extent than 8‐methoxypsoraien (8‐MOP). The new compounds, in the presence of long‐wavelength ultraviolet radiation, are very moderately effective in forming reactive oxygen species; they are ineffective in promoting oxidation of tyrosine and 3‐(3,4‐dihydroxyphenyl)alanine to do‐pachrome and melanin. Skin photosensitizing experiments on guinea pigs indicate that benzo‐ and tetrahydroben‐zopsoralen derivatives are almost devoid of any phototoxic effects. Thus, this class of compounds appears to be interesting for the development of new, less phototoxic chemotherapeutic agents that interact with DNA better than 8‐MOP.
AN ULTRAVIOLET RADIATION ACTION SPECTRUM FOR IMMEDIATE PIGMENT DARKENING
Authors: Irwin Christopher , Barnes Angelit , Veres Denise , Kaidbey Kays
Published: January 2008

The wavelength dependence for immediate pigment darkening (IPD) was investigated by exposing the midback skin of volunteers to a series of incremental fluences of narrow waveband radiation isolated by band‐pass filters in the310–400 nm region. The threshold IPD fluence for each waveband was determined by visual assessment of the skin responses immediately after each exposure. The action spectrum, constructed from the mean threshold fluences, was broad and extended from 320 nm to 400 nm with a peak at around 340 nm. No IPD could be evoked at 310 nm, even after erythemogenic fluences. The spectrum was similar in each of the three skin types investigated (III, IV, V). The broad nature of the action spectrum within the UVA region suggests that IPD may serve as an alternative endpoint for measuring photoprotection against these wavelengths.
PROTECTION OF THE D1 PHOTOSYSTEM II REACTION CENTER PROTEIN FROM DEGRADATION IN ULTRAVIOLET RADIATION FOLLOWING ADAPTATION OF Brassica napus L. TO GROWTH IN ULTRAVIOLET‐B
Authors: Wilson Michael I. , Greenberg Bruce M.
Published: January 2008

As depletion of the stratospheric ozone layer continues, the biosphere will most likely be exposed to higher levels of ultraviolet‐B (UV‐B) irradiation (290–320nm). For plants, damage from UV‐B can occur at several molecular targets with the photosynthetic apparatus being especially vulnerable. We are interested both in the mechanisms of UV‐B‐induced damage and identifying adaptation processes that can confer protection from UV‐B. Toward this end,Brassica napus(oil seed rape) plants grown under visible light plus a low level of UV‐B radiation (adapted plants) were compared to plants grown under visible light alone (control plants). Relative to the control plants, the adapted plants showed little evidence of damage at the levels of morphology or photosynthesis, indicating thatB. napushas some tolerance of UV‐B and that the plants may have protection mechanisms. Consistent with this, a strong UV‐B adaptation process was observed in the plants‐accumulation of flavonoids in the epidermis. These pigments seemed to screen a molecular target in the mesophyll. Namely, the D1 photosystem II reaction center protein, which is rapidly degraded in UV‐B, was partially protected from degradation in UV‐B in the adapted plants. Moreover, the extent that the half‐life of the D1 protein increased in the adapted plants was on par with the elevation in total flavonoid concentrations. These experiments demonstrate that degradation of the D1 protein can be used as anin vivoassay of penetration of UV‐B photons to the mesophyll.
OSCILLATORY LOW‐LEVEL CHEMILUMINESCENCE FROM A NONEQUILIBRIUM β‐NICOTINAMIDE ADENINE DINUCLEOTIDE‐PEROXIDASE SYSTEM: EXPERIMENTAL OBSERVATIONS and COMPUTER SIMULATIONS
Authors: Watanabe Nobuyuki , Inaba Humio
Published: January 2008

Using a highly sensitive photon counting technique, oscillatory low‐level chemiluminescence was observed from a non‐equilibrium oxidation of β‐nicotinamide adenine dinucleotide (NADH) by horseradish peroxidase (HRP). Emergence and stability of the oscillation were affected by the concentration of HRP, 2,4‐dichlorophenol and infusion rate of NADH. We also constructed a simultaneous rate equation to explain the oscillatory phenomena of this non‐equilibrium system, in which the photon emission was assumed to be generated from NAD'‐O2 interaction.
LASER‐LIGHT INDUCED CHROMOSOME ABERRATIONS IN CHINESE HAMSTER CELLS
Authors: Virsik‐Peuckert P. , Hillrichs G. , Neu W. , Harder D.
Published: January 2008

Wild‐type Chinese hamster cells CHO Kl and their radiosensitive mutant xrs5 were irradiated at 308 nm, using light pulses of a XeCl excimer laser with total energy fluences of 0.1 kj/m2 to 4.08 kj/m2. Chromosome‐type and chromatid‐type chromosome aberrations have been observed at pulse irradiances of 2.5 × 107 W/m2 and 1.7 × 108 W/m2, indicating that in mammalian cells DNA double‐strand breaks occur already in this irradiance range. The results obtained with laser irradiation are compared with X‐ray irradiation.
ALTERATION OF DYNAMIC QUATERNARY STRUCTURE AND CALCIUM‐BINDING ABILITY OF ß‐CRYSTALLIN BY LIGHT
Authors: Sharma Yogendra , Krishna A. Gopala , Balasubramanium D.
Published: January 2008

Abstract— ß‐crystallin, one of the three main constituent proteins of the eye lens, exists as an equilibrium population of oligomeric (ßH), trimeric (ßL1) and dimeric (ßL2) species. This equlibrium is dependent on various factors such as the protein concentration, ionic strength and pH of the medium. WE have studied the effect of ultraviolet B radiation on the aggregational patterns of ß‐crystallin, using size‐exclusion chromatography. Irradiation of a solution of ßH‐crystallin at 295 nm for about 30 min causes the deaggregation of the hexameric population into dimers. Irradiation for a longer time, however, produces cross‐linked high molecular weight products. Irradiation of a ßL2 solution for 30 min does not perturb the elution profile, while irradiation for a longer time increases the content of ßL1 (trimeric) crystallin. Irradiation also causes a decrease in the calcium‐binding affinity of the ß‐crystallins.
COMPARTMENTALIZATION OF ZINQII) TETRAPHENYLPORPHYRIN IN A HYDROPHOBIC MICRODOMAIN OF AN AMPHIPHILIC POLYELECTROLYTE: A PHYSICOCHEMICAL MODEL OF BIOLOGICAL METALLOPORPHYRIN SYSTEMS
Authors: Aota Hiroyuki , Morishima Yotaro , Kamachi Mikiharu
Published: January 2008

Abstract— Small mole fractions of zinc(II) tetraphenylporphyrin (ZnTPP) moieties were covalently incorporated into amphiphilic polysulfonates having bulky hydrophobic groups such as lauryl, cyclododecyl, and (2‐naphthyi)methyl (Np) groups in their side chains. The ZnTPP moieties are “compartmentalized” in the hydrophobic domains of these amphiphilic polyelectrolytes in aqueous solution. For comparison, the ZnTPP moieties were covalently incorporated into a polysulfonate without hydrophobic groups. The ZnTPP moieties in this reference polymer are exposed to water in aqueous solution. The compartmentalized ZnTPP systems in aqueous fluid solution emitted phosphorescence and thermally activated delayed fluorescence at room temperature. This is due to an extremely long‐lived triplet excited state in the compartmentalized systems at room temperature in aqueous solution, e.g. 19 ms for ZnTPP compartmentalized in Np domains, compared with 3 ms for ZnTPP in the reference polymer. These remarkable compart‐mentalization effects may be attributed to a restriction of motional freedom of the ZnTPP moiety isolated in a rigid and hydrophobic microenvironment provided by the amphiphilic polyelectrolytes in aqueous solution.
In situ SUSCEPTIBILITIES OF PHOTOSYSTEMS I AND II TO PHOTOSENSITIZED DEACTIVATION via SINGLET OXYGEN MECHANISM
Authors: Kim Chang Sook , Han Gwang Hyun , Kim Jin Man , Jung Jin
Published: January 2008

Abstract— A comparative study was carried out on the in situ susceptibilities to photoinactivation of the photosystem I (PS I) and II (PS II) complexes of spinach thylakoids treated with efficient type II sensitizers. While the presence of the exogenous sensitizers caused a substantial increase in the extent of photoinactivation of whole chain electron transport, it did not affect PS I activity of thylakoids in light but exerted an enhanced photoinactivating effect only on PS II. The measurements of the action spectrum for the inhibition of PS II activity of the sensitizer‐incorporated thylakoids and that for the generation of singlet oxygen (1O2) from them revealed that photosensitized inactivation of PS II is directly related to the photoproduction of 1O2 in thylakoid membranes. The results obtained in the present work clearly demonstrate an exceptional sensitivity of PS II to 1O2, providing circumstantial evidence that high light‐induced damage to PS II may result from photosensitization reactions mediated by 1O2, which is not necessarily produced within the PS II complex.
PHOTOTOXICITY OF (1H‐INDENYL)THIOPHENES
Authors: Hekrnreiter Mignon , Kagan Jacques , Chen Xinsheng , Lau Ka Y. , D'Auria Maurizio , Vantaggi Anna
Published: January 2008

The (1H‐indenyl)thiophene derivatives 2 and 3 were recently reported to be excellent singlet oxygen sensitizers. comparable to α‐terthienyl (1). The phototoxicity of these compounds was compared, using human erythrocytes, Aedes aegypti mosquito larvae. Daphnia magna. and fish (fathead minnows, Pimephales promelas). The known ranking of the photooxidation properties was found to be a good predictor of phototoxic properties in erythrocytes and mosquito larvae but not in daphnias. All three compounds photosensitized the cleavage of supercoiled pBR322 DNA to the same extent.
PHOTOLESIONS AND BIOLOGICAL INACTIVATION OF PLASMID DNA ON 254 nm IRRADIATION AND COMPARISON WITH 193 nm LASER IRRADIATION
Authors: Gurzadyan Gagik G. , Gorner Helmut , Schulte‐Frohlinde Dietrich
Published: January 2008

Plasmid pTZ18R and calf thymus DNA in aerated neutral aqueous solution were irradiated by continuous 254 nm light. The quantum yields are φssb= 4.0 × 10‐5and φdsb= 1.4 × 10‐6for single‐ and double‐strand break formation, respectively, φbr= 2.3 × 10‐5for base release, φdn=2.1 × 10‐3for destruction of nucleotides, and φicl×φlds× 1 × 10‐6for interstrand cross‐links and locally denatured sites, respectively. The presence of Tris‐HCI/ ethylenediaminetetraacetic acid (10:1, pH 7.5) buffer strongly reduces φssb, The corresponding φ values, obtained on employing pulsed 193 nm laser irradiation, are much larger than those using λirr, = 254 nm. This is ascribed to a contribution of chemical reactions induced by photoionization, which is absent for 254 nm irradiation. The quantum yields of inactivation of plasmid DNA (λirr= 254 nm) were measured by transformation of theEscherichia colistrains AB1157 (wild type), φina(1157) = 1.6 × 10‐4, AB1886 (uvr‐), φina(1886) = 4.2 × 10‐4, AB2463 (rec‐), φina(2463) = 4.1 × 10‐4and AB2480 (uvr‐rec‐), φina(2480) = 3.1 × 10‐3. The quantum yields of inactivation of plasmid DNA are compared with those of the fourE. colistrains (denoted as chromosomal DNA inactivation) obtained from the literature. The results forE. colistrain AB2480 show that the chromosomal DNA and the plasmid DNA are both inactivated by a single pyrimidine photodimer per genome. With theE. colistrain AB2463 inactivation of plasmid and chromosomal DNA is the same for the same total damage per genome and is ∼ 10 times smaller than for AB2480. This is explained by photodimer repair in chromosomal and plasmid DNA and by the absence of dsb repair in both cases. In the repair wild‐type strain AB1157, inactivation of the plasmid DNA is roughly 100 times higher than that of the chromosomal DNA. We postulate that a portion of this difference is due to repair of dsb by the recA system in chromosomal DNA and that such repair does not take place in the plasmid DNA. The biological results from 254 nm irradiation are compared with those from 193 nm laser irradiation.
A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA
Authors: Fiedor L. , Gorman A. A. , Hamblett I. , Rosenbach‐Belkin V. , Salomon Y. , Scherz A. , Tregub I.
Published: January 2008

Two amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O2(lΔ8), with essentially unit efficiency as evidenced by time‐resolved IR luminescence measurements.
FLAVIN‐PHOTOSENSITIZED MONOMERIZATION OF DIMETHYLTHYMINE CYCLOBUTANE DIMER IN THE PRESENCE OF MAGNESIUM PERCHLORATE
Authors: Miyake Kunihito , Masaki Yasuhiro , Miyamoto Ikuya , Yanagida Shozo , Ohno Takeshi , Yoshimura Akio , Pac Chyongjin
Published: January 2008

We have investigated the photosensitized monomerization of the cis,syn‐cyclobutane dimer of 1,3‐di‐methylthymine using riboflavin tetraacetate and a 5‐deazaflavin derivative as photosensitizer. Although little monomerization of the dimer is induced by photoexcitation of the flavins in the absence of any additives, the flavins can function as an efficient photosensitizer in the presence of magnesium perchlorate. Mechanistic studies involving spectroscopic, quantum‐yield and flash‐photolysis measurements demonstrated that the photosensitized monomerization exclusively proceeds through electron transfer from the dimer to the triplet flavins complexed with Mg2+. The effects of magnesium perchlorate are compared with those on the chloranil‐photosensitized monomerization and also with the effects of HClO4 on the flavin‐photosensitized reaction.
TWO DIFFERENT TYPES OF PHOTOCHEMISTRY IN PHYCOERYTHROCYANIN α‐SUBUNIT*
Authors: Hong Qiang , Zhao Kai‐Hong , Scheer Hugo
Published: January 2008

The photochemical activities of phycoerythrocyanin α‐subunits fromMastigocladus laminosusseparated by isoelectric focusing were tested by irradiating at 500, 550, 577 and 600 nm. Two types of photoreversible photochromic responses have been characterized by absorption and absorption difference spectroscopy. Type I is the well‐known absorption shift from 571 to 506 nm. Type II is a new response characterized by a line‐broadening of the 570 nm absorption.