bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phototoxicity of Protoporphhyrin IX, Diarginine Diprotoporphyrinate and N,N‐Deiphenylalanyl Protoporphyrin Toward Human Fibroblasts and ketratinocytes In vitro: Effect of 5‐Methoxypsoralen†;
Authors: Bugaj Andrzej , Morllére Patrice , Santus René , Haigle Josiane , Dyderski Stanistaw 
Published: July 2010

AbstractThe phototoxicity of two new porphyrin photosensitizers, diarginine diprotoporphyrinate (PP(Arg)2) and N,N‐diphenylalanyl protoporphyrin (PP(Phe)2), and the synergistic effect of 5‐methaoxyposralen (5‐MOP) have been studied in comparison with that of protoporphyrin IX (PPIX). Under ultraviolet A (UV‐A) irradiation (λ= 365 nm), the phototoxicity of the porphyrins toward cultured human fibroblasts and keratino‐cytes decerases in the order: PPIX > PP(Arg)2 > PP(Phe)2. A synergistic efect of 5‐MOP on the phototoxicity of PPIX, PP(Arg)2 and PP(Phe)2 has been observed. The combination of PPIX, PP(Arg)2 and PP(Phe)2 with 0.1–0.5 μM 5‐MOP significantly potentiates the phototoxicity of the three porphyrins. The most effective potentiation was observed with the water‐soluble PP(Arg)2 and 5‐MOP concentrations lowere than 0.75 μM. Above this 5‐MOP concnetration this potentiation is abolished. The intracellular concentration of PPIX and PP(Phe)2 is independent of the presence of 5‐MOP. On the other hand, the intracellular contnet of PP(Arg)2 is decerased in concentration‐dependent manner by the psoralen. Illumination with red light, not absorbed by 5‐MOP, leads to a weak potentiation of the PP(Arg)2 phototoxic effect in the presence of 5‐MOP, suggesting that dark interaction of 5‐MOP with cell membranes aggravated by porphyrin photosensitization is involved in the observed phenomena. The results are tentatively explained by differences in hydrophobicity and molecular structure of the examined photosensitizers. PPIX, which is barely soluble in water, has a significantly higher affinity for cell membranes and simultaneously exerts a stronger phototoxic effect than PP(Arg)2 whose solubility in water is high. On the other hand, the weak phototoxicity of PP(Phe)2 could be explained by the steric hindrance brought by the phenylalanyl substituents on the pyrrole ring. The loss in the PP(Arg)2 cell content probably explains the inhibition of the synergistic effect of 5‐MOP on the PP(Arg)2 phototoxicity at high 5‐MOP concentration. This study suggests that PP(Arg)2 in combinatin with 5‐MOP might reveal a strong phototoxic effect when applied to skin cancer treatment.
Light Absorption by the Chlorophylla–bComplexes of Photosystem II in a Leaf with Special Reference to LHCII¶
Authors: Rivadossi Andrea , Zucchelll Giuseppe , Gariaschi Flavio M. , Jennigns Robert C. 
Published: July 2010

AbstractTo investigate the light‐harvesting properties of the Photsystem II chlorophyll (chl)a‐bcomplexes (major light‐harvesting complex of Photosystem II [LHCII], CP24, CP26, CP29) in a mature leaf under natural “daylight” illumination, the absorption spectra of the isolated complexes were converted into the photon absorption spectrum (1‐T) within a leaf, using the approach of Rivadossiet al. ([1991]Photosynth. Res.60, 209–215). In the Qyregion, significant enhancement of light harvesting by the chlbelectronic transitions, with respect to the absorption spectra (optical density [od]), as well as a large and generalized increase (between two‐ and four‐fold) associated with the vibrational bands of both chlaandb, was observed, which acquires an important light‐harvesting role (approximately 30–40% of total). In the Soret region, a small increase in light harvesting by chlb was indicated. To gain more detailed information on these aspects the light harvesting of LHCII in a leaf was investigated. This required describing the pigment absorption (chla andb, carotenoids) in the LHCII OD spectrum in therms of spectral subbands, which were subsequently used to estimate the relative light harvesting of each pigment type in LHCLL in leaf. When the entire visible spectral interval between 400 and 730nm is considered, the chlalight harvesting is essentially unchanged with respect to the absorption spectrum (OD) of isolated LHCII, whereas the chlbcontribution is 20% higher and the carotenoids are 33% lower. The relative enhancement of chlbabsorption is principally associated wiht the Qyelectronic transition region, the light‐harvesting contribution of which becomes prominent in the leaf.
Thylakoid‐associated Polyamines Adjust the UV‐B Sensitivity of the Photosynthetic Apparatus by Means of Light‐harvesting Complex II Changes¶
Authors: Sfichi Liliana , Loannidis Nikolaos , Kotzabasis Kiriakos 
Published: July 2010

AbstractThe sensitivity of the photosynthetic apparatus to ultraviolet‐B (UV‐B) irradiation was studied in cultures of unicellular green alga Scenedesmus obliquus incubated in low light (low photosynthetically active radiation intensity [LL]) and high light (high photosynthetically active radiation intensity [HL]) conditions, treated or not with exogenous polyamines. Biochemical and physicochemical measurement showed that UV‐B radiation induces a decrease in the thylakoid‐associated putrescine (Put) and an increase in spermine (Spm), so that the reduction of Put/Spm ratio leads to the increase of light‐harvesting complex II (LHCII) size per active reaction center and, consequently, the amplification of UV‐B effects of the photosynthetic apparatus. The separation of oligomeric and monomeric froms of LHCII from isolated thylakoids showed that UV‐B induces an increase in the oligomeric forms of LHCII, which was more intense in LL than in HL. By manipulating the LHCII size with exogenous polyamines, the sensitivity degree of the photosynthetic apparatus to UV‐B changed significantly. Specifically, the addition of Put decreased highly the sensitivity of LL culture to UV‐B because of the inhibitory effect of Put on the LHCII size increasing, wheres the addition of Spm enhanced the UV‐B injury induced in HL culture because of the increasing of LHCII size. The ability of the photosynthetic apparatus to recover the UV‐B induced changes was also investigated.
Photochemical Reduction of Cytochrome c by a 1,4,5,8‐Naphthalenediimide Radical Anion¶
Authors: Campos Ivana B. , Nantes Iseli L. , Politi Mario J. , Brochsztain Sergio 
Published: July 2010

AbstractSteady‐state UV irradiation of aqueous solutions containing cytochrome c (cyt c) and N,N′‐bis(2‐phosphonoethyl)‐1,4,5,8‐naphthalenediimide (BPNDI), a water‐soluble aromatic imide, resulted in the reduction of the heme iron from the Fe(III) to the Fe(II) oxidation state. The reaction kinetics were followed by the increase of the ferrocytochrome c absorbance band at 549 nm. The rate of the photochemical reaction was pH dependent, reaching its maximum values over the pH range 4–7. Addition of electrolyte (NaCl) at pH 5 resulted in a decrease in the reaction rate, as expected for reactions between oppositely charged species. Flash photolysis studies revealed that the actual reductant in the reaction was a photogenerated BPNDI radical anion, which transferred an electron to the cyt c heme iron. The participation of imide radicals in the process was confirmed by the ready reduction of cyt c by BPNDI radicals chemically generated with sodium dithionite.
Effects of Freezing on Thermoluminescence in Various Plant Species¶
Authors: Janda Tibor , Szalai Gabriella , Papp Nóra , Pál Magda , Páldi Emil 
Published: July 2010

AbstractThe aim of this study was to monitor the effect of sudden frost on the photosynthetic electron transport chain in the leaves of various plant species using the thermoluminescence (TL) technique. A short period of freezing caused a decrease in the afterglow (AG) band in young maize leaves, with a slight upshift in the maximum temperature. The B band induced by far‐red (FR) illumination started to decrease at a significantly lower temperature. The flash‐induced B band also showed a substantial decrease in intensity after short preliminary freezing. In contrast to other species, for which there was always a well‐detectable TL signal even after relatively drastic freezing, there was no TL singal at all in geranium below a threshould temperature. The behavior of the FR‐induced TL curve in cucumber plants was a mixture of that found in wheat or pea, on the one hand, and maize, on the other: the AG band gradually decreased with decreasing temperature and finally totally disappeared, as in maize. The FR‐induced B band showed an upshift after freezing. These results suggest that AG is a normal component of TL bands induced not only by FR, but also by single turnover flash.
Primary Photochemical Processes of the Phototoxic Neuroleptic Cyamemazine: A Study by Laser Flash Photolysis and Steady‐state Irradiation¶
Authors: Morlière Patrice , Bosca Francisco , Miranda Miguel A. , Castell José V. , Santus René 
Published: July 2010

AbstractThe photophysical and photochemical properties of the UV‐A‐absorbing phototoxic drug cyamemazine (CMZ) (2‐cyano‐10‐(3‐[dimethylamino]‐2‐methyl‐propyl)‐phenothiazine) have been investigated in neutral buffered aqueous solutions. The transient absorbances of the hydrated electrons, of the first excited triplet state (3CMZ*) with a characteristic absorption band peaking at 420 nm and of the radical cation (•CMZ+) (maximum absorbance at 500 nm) have been observed by 355 nm laser flash spectroscopy of deaerated solutions. All these transient species are formed by monophotonic processes and react with oxygen. Bimolecular reaction rate constants of •CMZ+ and 3CMZ* with O2 are 2 × 107M−1 s−1 and 4 × 109M−1 s−1, respectively. The 3CMZ* reacts only sluggishly (reaction rate constant, 9 × 106M−1 s−1) with tryptophan chosen as a Type‐I photodynamic substrate. Steady‐state irradiations with 365 nm light demonstrate that CMZ is rapidly photolyzed (quantum yield, 0.04) in O2‐saturated solutions leading to oxidation of the sulfur atom and of the side‐chain nitrogen of CMZ. This photoproduct (2‐cyano‐10‐(3‐[dimethylamino, N‐oxide]‐2‐methyl‐propyl)‐5‐oxide‐pheno‐thiazine), is a good Type‐I and Type‐II photodynamic photosensitizer producing singlet oxygen in high yield (‐0.45) and could play a major role in the phototoxicity of CMZ.
Purification and Initial Characterization of a Putative Blue Light‐regulated Phosphodiesterase from Escherichia coli¶
Authors: Rajagopal Sudarshan , Key Jason M. , Purcell Erin B. , Boerema David J. , Moffat Keith 
Published: July 2010

AbstractThe Escherichia coli protein YegF contains a photosensory flavin adenine dinucleotide (FAD)‐binding BLUF domain covalently linked to an EAL domain, which is predicted to have cyclic‐di‐guanosine monophosphate (GMP) phosphodiesterase activity. We have cloned, overexpressed and purified this protein, which we refer to as blue light‐regulated phosphodiesterase (Blrp) for its putative activity. Blrp undergoes a reversible photocycle after exposure to light in which the spectrum of its photostationary state and kinetics of recovery of the dark state are similar to those of the isolated BLUF domain of the AppA protein. Unlike the AppA BLUF domain, the chromophore environment in the context of full‐length Blrp is asymmetric, and the protein does not undergo any detectable global changes on exposure to blue light. When overexpressed in E. coli, Blrp copurifies with certain proteins which suggests that it plays a protective role in response to oxidative stress. Predicted proteins from Klebsiella pneumoniae and from a bacterium in the Sargasso Sea are similar to E. coli Blrp in both their BLUF and EAL domains, which suggests that blue light sensing in these bacteria may follow similar pathways.
Spectroscopic Properties of Various Quinolone Antibiotics in Aqueous—organic Solvent Mixtures¶
Authors: Park Hyoung‐Ryun , Oh Chu‐Ha , Lee Hyeong‐Chul , Lim Sam Ryong , Yang Kiyull , Bark Ki‐Min 
Published: July 2010

AbstractThe spectroscopic properties of enoxacin (ENO), oxolinic acid (OXO) and nalidixic acid (NAL) were studied in various H2O‐CH3OH and H2O‐CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. ENO has piperazinyl group, but OXO and NAL do not have this substituent. The fluorescence emission spectra of ENO were very sensitive to the composition of the solvents. In the Lippert‐Mataga analysis of the steady‐state fluorescence data, clear reverse solvatochromism was exhibited for ENO in both mixed solvents. This observation can be explained using the excited state twisted intramolecular charge transfer (TICT) from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. The nonradiative and radiative rate constants of these molecules were analyzed as a function of dipolarity–polarizability (π*) and hydrogen bond donor acidity (α) of the mixed solvents. These results for ENO were consistent with the suggested mechanism of the TICT very well. The influence of bulk dielectric effect was more significant relative to the specific hydrogen bonding interactions. The emission spectra of OXO and NAL do not exhibit any characteristic responses to the properties of the solvent.
Effect of pH on inhibition and enhancement of luminol‐H2O2‐Co2+ chemiluminescence by phenolic compounds and amino acids
Authors: Cui Hua , Shi Ming‐Juan , Meng Rong , Zhou Jian , Lai Chun‐Ze , Lin Xiang‐Qin 
Published: July 2010

AbstractThe effect of pH on inhibition and enhancement of luminol‐H2O2‐CO2+ chemiluminescence (CL) by 18 phenolic compounds and 20 amino acids was studied. It was found that most of the tested compounds showed an inhibiting effect of lower pH and an enhancing effect at higher pH. At a midrange pH, for some phenolic compounds with two ortho‐position ‐OH, both an inhibiting and an enhancing peak were simultaneously observed. UV‐visible spectra of the tested phenolic compounds at different pH values were studied. The mechanism for CL inhibition and enhancement was proposed. It is likely that the competition of the ‐OH or the ‐NH2 group and other reducing groups in the molecules with luminol for O2*− led to the CL inhibition. A reaction of ‐COO− and quinone or ketone formed by phenolic compounds at higher pH via deprotonation with O2*− also resulted in the CL enhancement.
Effect of monovalent and divalent cations on the photoinactivation of bacteria with meso‐substituted cationic porphyrins
Authors: Lambrechts Saskia A. G. , Aalders Maurice C. G. , Langeveld‐Klerks Diana H. , Khayali Youssef , Lagerberg Johan W. M. 
Published: July 2010

AbstractIt is well established that for successful photoinactivation (PI) of gram‐negative bacteria a cationic photosensitizer is required. This requirement suggests a charge‐dependent interaction between the photosensitizer and the gram‐negative bacterium, which may be influenced by the presence of ions in the suspending medium. The aim of the present study was to investigate the effect of cations Na+ and Ca2+ on the efficacy of the PI of the gram‐negative Pseudomonas aeruginosa and the gram‐positive Staphylococcus aureus. The bacteria were suspended in buffer containing either meso‐tetra(N‐methyl‐4‐pyridyl)‐porphyrin or meso‐mono‐phenyl‐tri(N‐methyl‐4‐pyridyl)‐porphyrin as photosensitizer and various concentrations of Na+ or Ca2+. The cell suspensions were exposed to a broadband light dose of 9 J/cm2. In buffer without added cations, P. aeruginosa and S. aureus were equally sensitive to PI. Addition of cations strongly decreased the sensitivity of both bacteria to PI, with the PI of P. aeruginosa being much more decreased than that of S. aureus, and Ca2+ being more effective than Na+. The decreased sensitivity was accompanied by a reduced binding of the photosensitizers to the bacteria.
Redox Photochemistry of Thiouredopyrenetrisulfonate¶
Authors: Kottyar Alexander B. , Borovok Natalia , Khoroshyy Petro , Tenger Katalin , Zimányi László 
Published: July 2010

ABSTRACT1‐Thiouredopyrene‐3,6,8‐trisulfonate (TUPS) has recently been used as a photoinduced covalent redox label capable of reducing various cofactors of proteins. A new reaction of this dye, whereby its excited triplet state oxidizes suitable electron donors, is now reported. The characteristic difference spectrum of the reduced radical of TUPS is determined. We also observe the self‐exchange electron transfer between two TUPS molecules in their triplet excited states and determine the reaction scheme and the rate constants of the various pathways in the process of triplet depletion. The ability of photoexcited TUPS to withdraw an electron from reduced cytochrome‐c is also observed. It is thus demonstrated that TUPS is an appropriate photoinduced covalent redox label for initiating both the oxidative and reductive phases of electron transfer processes in biological macromolecules.
Inhibition of DNA Polymerization and Antifungal Specificity of Furanocoumarins Present in Traditional Medicines¶
Authors: Smith Myron L. , Gregory Peter , Bafi‐Yeboa Nana F. A. , Arnason John T. 
Published: July 2010

ABSTRACTAntifungal activity is positively correlated to furanocoumarin content in extracts of the traditional phytomedicine northern prickly ash (Zanthoxylum americanum Mill. [Rutaceae]). The specificity of these furanocoumarins in inhibiting replication of DNA was investigated with reference to significant base composition differences between fungal and mammalian mitochondrial DNA. We developed a polymerase chain reaction‐based assay to investigate whether (1) furanocoumarins inhibit DNA polymerization and (2) distinct furanocoumarins specifically inhibit DNA replication depending on base composition. Specific inhibition of DNA polymerization by 5‐methoxypsoralen and psoralen through high‐adenine and thymine (AT) (84.3%) and low‐AT (51.9%) DNA, respectively, suggests that furanocoumarins inhibit replicative functions of genomes or of regions within the genome that differ in base composition. Greater overall inhibition of DNA polymerization by Z. americanum husk extracts than with single or mixed furanocoumarins suggests that inhibitory compounds in addition to the major furanocoumarins are present in Z. americanum.
Toward Understanding the Mechanism of Chromophore‐assisted Laser Inactivation–Evidence for the Primary Photochemical Steps¶
Authors: Horstkotte Elke , Schröder Torsten , Niewöhner Jens , Thiel Erwin , Jay Daniel G. , Henning Stefan W. 
Published: July 2010

ABSTRACTChromophore‐assisted laser inactivation (CALI) is a lightmediated technique used to selectively inactivate proteins of interest to elucidate their biological function. CALI has potential applications to a wide array of biological questions, and its efficiency allows for high‐throughput application. A solid understanding of its underlying photochemical mechanism is still missing. In this study, we address the CALI mechanism using a simplified model system consisting of the enzyme β‐galactosidase as target protein and the common dye fluorescein. We demonstrate that protein photoinactivation is independent from dye photobleaching and provide evidence that the first singlet state of the chromophore is the relevant transient state for the initiation of CALI. Furthermore, the inactivation process was shown to be dependent on oxygen and likely to be based on photooxidation of the target protein via singlet oxygen. The simple model system used in this study may be further applied to identify and optimize other CALI chromophores.
Photoreactions of 1,4‐Naphthoquinones: Effects of Substituents and Water on the Intermediates and Reactivity¶
Authors: Görner Helmut 
Published: July 2010

ABSTRACTThe photochemistry of lapachol and other 1,4‐naphthoquinone (NQ) derivatives, e.g. 2‐methoxy‐1,4‐naphthoquinone (MeONQ), 2‐hydroxy‐1,4‐naphthoquinone (2‐HONQ) or 5‐hydroxy‐1,4‐naphthoquinone (5‐HONQ) and 2‐methyl‐5‐hydroxy‐1,4‐naphthoquinone (P‐NQ) in solution at room temperature was studied by ultraviolet‐visible spectroscopy after nanosecond laser pulses at 248 nm. The triplet state and semiquinone radicals were observed for MeONQ, HONQ and P‐NQ, whereas for lapachol, intramolecular H‐atom and charge transfer processes take place, as in the case of vitamin K1. The photoinduced reaction of NQ into HONQ is initiated by nucleophilic water addition to the triplet state, and for the secondary reactions, a modified mechanism is proposed.
Kinetics of Protoporphyrin IX Formation in Rat Oral Mucosa and Skin After Application of 5‐Aminolevulinic Acid and its Methylester¶
Authors: Kristiansson Stefan , Juzeniene Asta , Juzenas Petras , Iani Vladimir , Löfgren Lennart , Moan Johan 
Published: July 2010

ABSTRACTThe kinetics of accumulation of protoporphyrin IX (PpIX) after topical application of 5‐aminolevulinic acid (ALA) and its methylester (5‐aminolevulinic acid methylester [ALA‐Me]) was studied on rat oral mucosa. The accumulation of PpIX in mucosa and skin after intravenous injection of ALA and ALA‐Me was also studied. The elimination rate of PpIX was dependent on drug and dose as well as on administration route. Application of ALA on rat oral mucosa and skin caused a systemic effect with PpIX building up in remote skin sites not exposed to the drugs. No such systemic effect was seen after application of ALA‐Me either in mucosa or on skin. Intravenous injection of the drugs (0.2 g/kg) leads to more fluorescence in the skin than topical application of the drug (20%). For mucosa, the opposite is true. Maximal PpIX fluorescence appeared later after application of high concentrations of the drugs (around 8 h for 5% and 20% wt/wt) than after application of low concentrations (around 3–5 h for 1% and 2% wt/wt).
The Effect of pH on the Topography of Porphyrins in Lipid Membranes¶
Authors: Bronshtein Irena , Smith Kevin M. , Ehrenberg Benjamin 
Published: July 2010

ABSTRACTThe effect of the acidity of the environment on the topography and photophysics of sensitizer molecules in homogeneous solutions, and when embedded in a lipid microenvironment, was studied. Four hematoporphyrin (HP) analogs were studied, which have chemical “spacers” of varying lengths between the chromophoric tetrapyrrole and the carboxylate moiety. These derivatives have essentially the same chemical attributes and reactivity as the parent compound, HP IX, which is used in clinical procedures of photodynamic therapy. The binding constants of these HP derivatives to membrane model systems increase with the length of carboxylate chain in the pH range 3.0–6.6. This effect of chain length is attributed to an increase in the hydrophobicity of the molecule on elongation of the alkyl chains. A strong pH dependence of the quenching efficiency of the porphyrins' fluorescence by iodide ions was observed in aqueous solution and is attributed to a unique electrostatic interaction between the fluorophore and the quencher. The quenching efficiency in liposomes, relative to the quenching in buffer, as a function of pH, shows that porphyrins in the neutral form penetrate deeper inside the lipid bilayer and are less exposed to external quenching than when negatively charged at the carboxylic moiety. This vertical displacement in the membrane is also evidenced in the effect of pH on the photosensitized oxidation efficiency of a membrane‐bound chemical target. Increasing the pH causes a significant decrease in the sensitization efficiency in liposomes. This trend is attributed to the vertical localization, and protonation of the carboxylic groups on lowering the pH leads to sinking of the sensitizer into the lipid bilayer and to a consequent generation of singlet oxygen at a deeper point. This increases the dwell time of singlet oxygen within the bilayer, which results in greater photodamage to a membrane‐residing singlet oxygen target.