bluuebunny/crossref_metadata_2025_split huggingface dataset:
PSORALENS CLEAVE pBR322 DNA UNDER ULTRAVIOLET RADIATION
Authors: Kagan Jacques , Chen Xinsheng , Wang Tian P. , Forlo P. 
Published: January 2008

Abstract—supercoiled (SC) pBR322 was used to probe the recent claim that 5‐geranoxylpsoralen (5‐GOP) did not photoreact with DNA. Contrary to expectations, 5‐GOP was found to damage DNA in the presence of UV‐A through two competing pathways: (a) single strand breaks, identified by the conversion of supercoiled into open circular and linear DNA, and (b) cross‐linking, revealed by the fluence‐dependent decrease in the extent of denaturation of the double stranded supercoiled DNA to single stranded circular DNA. In addition, a fluence‐dependent modification reduced the ability of the restriction enzyme EcoR I to linearize the photosensitized DNA, and alkali‐labile lesions were generated.Psoralen, 5‐methoxypsoralerl, and 8‐methoxypsoralen, which are well‐known to undergo cycloaddi‐tion to DNA, had a more pronounced effect on supercoiled DNA. Single strand breaks occurred more readily than with 5‐GOP, and the surviving SC form remaining had reduced electrophoretic mobility in agarose gels. In all cases, the DNA damage was more prominent when oxygen was absent.
LASER MEDIATED RELEASE OF DYE FROM LIPOSOMES
Authors: Meulen David L. Vander , Misra Prabhakar , Michael Jason , Spears Kenneth G. , Khoka Mustafa 
Published: January 2008

Abstract—Liposomes made from phospholipids and containing sulforhodamine dye (1–50 mM) have been irradiated with nanosecond and picosecond laser pulses. Individual liposomes were locally heated by laser absorption of dye dimers during a single laser pulse, and heating was sufficient to release the liposome contents. The extent of dye release produced by a single laser pulse was shown to be quantitatively dependent on several interdependent variables, including dye concentration, liposome size, laser excitation parameters and initial temperature of the dye‐liposome system. Fluorescence lifetime data having three components have been obtained and analyzed in terms of three dye environments. Quantitative estimates support a photo‐induced thermal mechanism for liposome lysis and release of its contents. These results may be useful for laser induced delivery of therapeutic agents or other applications of lasers in biological systems.
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.
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

AbstractThe 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

AbstractThe 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

AbstractSteady‐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

AbstractFamilial 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

AbstractThe 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

AbstractFour 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

AbstractThe 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

AbstractAs 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

AbstractUsing 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

AbstractWild‐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.
PHOTOTOXICITY OF (1H‐INDENYL)THIOPHENES
Authors: Hekrnreiter Mignon , Kagan Jacques , Chen Xinsheng , Lau Ka Y. , D'Auria Maurizio , Vantaggi Anna 
Published: January 2008

AbstractThe (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.