bluuebunny/crossref_metadata_2025 huggingface dataset:
Photodynamic Treatment of the Dermatophyte Trichophyton rubrum and its Microconidia with Porphyrin Photosensitizers¶
Authors: Smijs Threes G. M. , van der Haas Richard N. S. , Lugtenburg Johan , Liu Yan , de Jong Rob L. P. , Schuitmaker Hans J.
Published: July 2010

The application of photosensitizers for the treatment of fungal infections is a new and promising development within the field of photodynamic treatment (PDT). Dermatophytes, fungi that can cause infections of the skin, hair and nails, are able to feed on keratin. Superficial mycoses are probably the most prevalent of infectious diseases in all parts of the world. One of the most important restrictions of the current therapeutic options is the return of the infection and the duration of the treatment. This is especially true in the case of infections of the nail (tinea unguium) caused by Trichophyton rubrum, an anthropophilic dermatophyte with a worldwide distribution. Recently, we demonstrated that 5,10,15‐tris(4‐methylpyridinium)‐20‐phenyl‐[21H,23H]‐porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester were excellent photosensitizers toward T. rubrum when using broadband white light. This study demonstrates the photodynamic activity of these photosensitizers with red light toward both a suspension culture of T. rubrum and its isolated microconidia. The higher penetration depth of red light is important for the PDT of nail infections. In addition, we tested the photodynamic activity of a newly synthesized porphyrin, quinolino‐[4,5,6,7‐efg]‐7‐demethyl‐8‐deethylmesoporphyrin dimethylester, displaying a distinct peak in the red part of the spectrum. However, its photodynamic activity with red light toward a suspension culture of T. rubrum appeared to be only fungistatic. Sylsens B was the best photosensitizer toward both T. rubrum and its microconidia. A complete inactivation of the fungal spores and destruction of the fungal hyphae was found. In studies into the photostability, Sylsens B appeared to be photostable under the conditions used for fungal PDT. A promising result of this study is the demonstration of the complete degradation of the fungal hyphae in the time after the PDT and the inactivation of fungal spores, both with red light. These results offer the ingredients for a future treatment of fungal infections, including those of the nail.
Bioluminescence Imaging of the Response of Rat Gliosarcoma to ALA‐PpIX‐mediated Photodynamic Therapy¶
Authors: Moriyama Eduardo H. , Bisland Stuart K. , Lilge Lothar , Wilson Brian C.
Published: July 2010

Photodynamic therapy (PDT) is a promising modality for the treatment of solid tumors that combines a photosensitizing agent and light to produce cytotoxic reactive oxygen species that lead to tumor cell death. The recent introduction of bioluminescence imaging (BLI), involving the use of the luciferase gene (luc) transferred into target tumor cells, followed by systemic administration of luciferin and detection of the emitted visible chemiluminescence photons, offers the potential for longitudinal imaging of tumor growth and therapeutic response in single animals. We demonstrate in this study the first results of the use of BLI to assess the response of an intracranial brain tumor model (9L rat gliosarcoma) to aminolevulinic acid (ALA)‐mediated PDT. Complementary in vitro experiments with the luciferase‐transfected 9L cells show that the decrease in the luminescent signal after PDT correlates with cell kill. In vivo imaging shows a decrease in the BLI signal from the tumor after ALA‐PDT treatment, followed by tumor regrowth. Furthermore, preliminary studies using cells transfected with a hypoxiaresponsive vector show an increase in bioluminescence within 4 h after Photofrin‐mediated PDT, demonstrating the ability to observe stress‐gene responses. These results suggest that BLI can be used to provide spatiotemporal information of intracranial brain tumor responses after PDT and may serve as a valuable response‐endpoint measure.
Lifetime of Fluorescent Pyrene Butyric Acid Probe in Single Living Cells for Measurement of Oxygen Fluctuation¶
Authors: Ribou Anne‐Cecile , Vigo Jean , Salmon Jean‐Marie
Published: July 2010

We study the fluorescence lifetime of the well‐known 1‐pyrene butyric acid (PBA) to assess oxygen concentrations in living cells. The behavior of the probe is first studied in water, ethanol, protein solution and liposome suspension. The Stern‐Volmer plot of these solutions is linear, and the bimolecular reaction rate constant agrees with previous observations. In single living cells, the PBA lifetime decreases with oxygen concentration (185 to 55 ns). The probe lifetime differences between living cells and liposome suspension, especially under nitrogen atmosphere, suggest a supplemental pathway for the deactivation of the probe. We simplify further the complex living cells system by stopping the cell functions and studying freshly fixed cells. In this case, we obtained an increase of PBA lifetime under nitrogen atmosphere (215 ns).
Involvement of Human Small Fragment Nuclease in the Resistance of Human Cells to UV‐C‐induced Cell Death¶
Authors: Ito Seiro , Kita Kazuko , Zhal Ling , Wano Chieko , Suzuki Toshikazu , Yamaura Akira , Suzuki Nobuo
Published: July 2010

Human small fragment nuclease (Sfn) is one of the cellular proteins that were reported to degrade small, single‐stranded DNA and RNA. However, the biological role of Sfn in cellular response to various stressors such as UV‐C (mainly 254 nm wavelength ultraviolet ray) remains unclear. We have examined whether modulation of human SFN gene expression affects cell survival capacity against UV‐C‐induced cell death, analyzing colony survival ability in UV‐C‐sensitive human RSa cells treated with short double‐stranded RNA (siRNA) specific for SFN messenger RNA (mRNA). The expression levels of SFN mRNA in the siRNA‐treated RSa cells decreased to about 15% compared with those in the control siRNA‐treated cells. The siRNA‐treated RSa cells showed lower colony survival and higher activity of caspase‐3 after UV‐C irradiation than the control siRNA‐treated RSa cells. Furthermore, the removal capacity of cyclobutane pyrimidine dimers (CPD) in the siRNA‐treated RSa cells decreased compared with the control siRNA‐treated RSa cells. There was no difference in the colony survival and CPD removal capacity after UV‐C irradiation between the control siRNA‐treated RSa cells and mock‐treated RSa cells. These results suggest that SFN expression is involved in resistance of RSa cells to UV‐C‐induced cell death through the roles it plays in the DNA repair process.
Estimating UV Erythemal Irradiance by Means of Neural Networks¶
Authors: Alados Inmaculada , Mellado José Antonio , Ramos Francisca , Alados‐Arboledas Lucas
Published: July 2010

In recent years, there has been a substantial increase in attempts to model the flux of ultraviolet radiation (UV). UV irradiance at surface level is a result of the combined effects of solar zenith angle, surface elevation, cloud cover, aerosol load and optical properties, surface albedo and the vertical profile of ozone. In this study, we present the development of an artificial neural network (ANN) model that can be used to estimate solar UV irradiance on the basis of optical air mass, ozone columnar content, latitude, horizontal visibility data and cloud information such as type, coverage and height. ANN are widely accepted as a technology offering an alternative way to tackle complex and ill‐defined problems. They can learn from examples, are fault tolerant in the sense that they are able to handle noisy and incomplete data, are able to deal with nonlinear problems and, once trained, can perform prediction and generalization at high speed. In this study, a multilayer perceptron network (MLP) consisting of an input layer, an output layer and one hidden layer was used. Training of the neural network was done using the Bayesian regulation back propagation algorithm. The study was developed using data from three stations on the Iberian Peninsula: Madrid and Murcia during the period 2000–2001 and Zaragoza in 2001. To train and validate the MPL neural networks, independent subsets of data were extracted from the complete database at each station. The results suggest that a MLP neural network using optical air mass, ozone columnar content, latitude and total cloud coverage provides the best estimates, with mean bias deviation and root mean square deviation of −0.1% and 18.0%, 1.6% and 19.6%, 0.1% and 14.6% at Madrid, Murcia and Zaragoza, respectively. Despite the dependence of the cloud radiative effect on cloud type, the use of additional information such as cloud type or cloud elevation did not improve these results. The performance of the developed ANN has been checked regarding its ability to estimate the UV index (UVI); results indicate that in more than 95% of the cases, the difference between estimated and measured values does not exceed one unit of UVI.
Phototoxic Effect of Visible Light on Porphyromonas gingivalis and Fusobacterium nucleatum: An In Vitro Study¶†
Authors: Feuerstein Osnat , Persman Nir , Weiss Ervin I.
Published: July 2010

The antibacterial effect of visible light irradiation combined with photosensitizers has been reported. The objective of this was to test the effect of visible light irradiation without photosensitizers on the viability of oral microorganisms. Strains of Porphyromonas gingivalis, Fusobacteriurm nucleatum, Streptococcus mutans and Streptococcus faecalis in suspension or grown on agar were exposed to visible light at wavelengths of 400–500 nm. These wavelengths are used to photopolymerize composite resins widely used for dental restoration. Three photocuring light sources, quartz‐tungsten‐halogen lamp, light‐emitting diode and plasma‐arc, at power densities between 260 and 1300 mW/cm2 were used for up to 3 min. Bacterial samples were also exposed to a near‐infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. The results show that blue light sources exert a phototoxic effect on P. gingivalis and F. nucleatum. The minimal inhibitory dose for P. gingivalis and F. nucleatum was 16–62 J/cm2, a value significantly lower than that for S. mutans and S. faecalis (159–212 J/cm2). Near‐infrared diode laser irradiation did not affect any of the bacteria tested. Our results suggest that visible light sources without exogenous photosensitizers have a phototoxic effect mainly on Gram‐negative periodontal pathogens.
A Phytochrome‐like Protein AphC Triggers the cAMP Signaling Induced by Far‐red Light in the Cyanobacterium Anabaena sp. Strain PCC7120¶
Authors: Okamoto Shinobu , Kasahara Masahiro , Kamlya Asako , Nakahira Yuka , Ohmori Masayuki
Published: July 2010

In the filamentous, nitrogen‐fixing cyanobacterium Anabaena sp. PCC7120, red light (630 nm) decreased, whereas far‐red light (720 nm) increased cellular adenosine 3′,5′‐cyclic monophosphate (cAMP) content. To find a red and far‐red light photoreceptor that triggers the cAMP signal cascade, we disrupted 10 open reading frame having putative chromophore‐binding GAF domains. The response of the cellluar cAMP concentration to red and far‐red light in each open reading frame disruptant was determined. It was found that only the mutant of the gene all2699 failed to respond to far‐red light. The open reading frame named as aphC encoded a protein with 920 amino acids including GAF domains similar to those involved in Cph2, a photoreceptor of Synechocystis sp. PCC6803. To determine which adenylate cyclase (AC) is responsible for far‐red light signal, we disrupted all AC genes and found that CyaC was the candidate. The enzymatic activity of CyaC might be controlled by a far‐red light photoreceptor through the phosphotransfer reaction. The site‐specific mutant of the Asp59 residue of the receiver (R1) domain of CyaC lost its light‐response capability. It was suggested that the far‐red light signal was received by AphC and then transferred to the N‐terminal response regulator domain of CyaC. Then its catalytic activity was stimulated, which increased the cellular cAMP concentration and drove the subsequent signal transduction cascade.
Evidence for Intracellular Aggregation of Hypericin and the Impact on its Photocytotoxicity in PAM 212 Murine Keratinocytes¶
Authors: Theodossiou Theodossis , Spiro Michael D. , Jacobson Jake , Hothersall John S. , MacRobert Alexander J.
Published: July 2010

We have assessed photoinduced toxicity of hypericin in PAM 212 murine keratinocytes and the relationship between concentration, incubation time and light fluence to evaluate the effect of intracellular aggregation at high concentrations. Confocal microscopy was used to establish the subcellular localization of hypericin at 5 and 50 μM and incubation times of 1 and 3 h. From fluorescence uptake time course studies, intracellular hypericin was demonstrated to exist predominantly in the monomeric form for up to 26 h incubation at 5 μM. However, there was a pronounced aggregation effect at 50 μM, with intracellular hypericin fluorescence levels initially showing an increase followed by a decrease with incubation time. This effect was subsequently shown to exert an effect on the phototoxicity of hypericin. On irradiation, the photocytotoxicity for 1 and 7 h incubation with 50 μM hypericin was comparable, whereas using 5 μM the photocytotoxicity showed good correlation with the intracellular fluorescence measurements at 1 and 7 h incubation.
Reflectance Spectra of Pigmented and Nonpigmented Skin in the UV Spectral Region¶
Authors: Nielsen Kristian P. , Zhao Lu , Juzenas Petras , Stamnes Jakob J. , Stamnes Knut , Moan Johan
Published: July 2010

We present measurements of reflectance spectra from human skin in vivo in the spectral range from 250 to 700 nm. These measurements show that the reflectance from strongly pigmented skin is higher than that from weakly pigmented skin at wavelengths shorter than approximately 300 nm. We simulate the measured results using a new radiative transfer model developed to study light propagation in skin tissue. Our simulations mimic the measured spectra when scattering from melanosomes, and fragmented melanosomes are taken into account. Scattering from microstructures with high relative refractive indices plays a major role in tissue optics. Our results show that scattering from melanosomes and fragmented melanosomes is of particular significance.
Effect of Netropsin on One‐electron Oxidation of Duplex DNA¶†
Authors: Roberts Lezah W. , Schuster Gary B.
Published: July 2010

The effect of netropsin on the oxidative reactions of duplex DNA was examined. One‐electron oxidation of DNA creates a radical cation that migrates through duplex DNA and reacts primarily at GG steps. Netropsin is a dication that specifically binds primarily by hydrogen bonding in the minor groove at sites that have four or more contiguous A‐T base pairs. We showed that the oxidation potential of netropsin is less than that of any of the four nucleobases. We find that netropsin quenches the oxidative reactions of DNA independent of whether it is specifically bound. Within the Perrin model of static quenching, a netropsin within a rather large fixed volume around the DNA is an effective quencher.
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

The 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

To 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

The 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

Steady‐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

The 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

The 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

The 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

The 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

The 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

It 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

1‐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

Antifungal 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

Chromophore‐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

The 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

The 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

The 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.
Photodynamics of Cataract: An Update on Endogenous Chromophores and Antioxidants¶
Authors: Balasubramanian D.
Published: July 2010

Cataract of the eye lens is characterized by (1) Progressive opacification or los of transparency; (2) accumulation of molecules that absorb in the UV ‐visible range of the spectrum; and (3) formation of fluid‐filled vacuoles, particularly in diabetics when sugar levels in teh lens are high. Of the various causative factors for cataract, light is an important one. Because the level of light below 320 nm reaching the lens is quite low, photodynamic effects of endogenous compounds absorbing in the UV‐A‐visible region become important in this connection. In this uupdate we summarize a list of accumulant chrompphores tha have been identified in aging and cataract human lenses and theilr roles as potential sensitizers, antioxidants or as benign filters. Because such photodynamic cataractogenesis is oxidative in nature, we also cite examples where administratiion of antioxidants could help delay cataract progression.
Time‐resolved Microspectrofluorimetry and Fluorescence Lifetime Imaging of Hypericin in Human Retinal Pigment Epithelial Cells¶
Authors: Taroni Paola , Valentini Gianluca , Comelli Daniela , D'Andrea Cosimo , Cubeddu Rinaldo , Hu Dan‐Ning , Roberts Joan E.
Published: July 2010

Hypericin is the active ingredient of the off‐the‐shelf antidepressant St. John's Wort. It is an effective phototoxic agent and its systemic administration at therapeutic doses could induce particular damage in the eye due to continuous light exposure. Hypercin is strongly fluorescent and its fluorescence properties can be monitored to investigate noninvasively its localization and interactions. To this aim, time‐resolved microspectrofluorimetry and fluorescence life‐time imaging were used to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by retinal pigment epithelium (RPE) cells treated with Hyp at concentrations in the micromolar range (0.5–10 μM). In the presence of hypericin, the emission peaks at 600‐605 nm and the fluorescence decay is best fitted with three lifetimes (5.5‐7 ns, 1.9‐2.5 ns and < 0.8 ns). Spectral and temporal differences were observed between high (≥5 μM) and low hypericin concentrations. In particular, upon increasing concentration, the emission spectrum of the slow component broadens and its lifetime shortens. The latter change is observed also when high concentrations are reached locally, due to more efficient localization within the cell.
Rhodopsin Phosphorylation in Rats Exposed to Intense Light¶
Authors: Ablocnzy Z. , Darrow R. M. , Knapp D. R. , Organisciak D. T. , Crouch R. K.
Published: July 2010

The damaging effects of intense light on the rat retina are known to vary depending on the time of day of exposure. The purpose of this study was to determine if rhodopsin phosphorylation patterns, a measure of the activity of the pigment, varied in a similar manner. After 10 min in strong light (1400 lux), all six threonine and serine sites in the rat rhodopsin C‐terminus were phosphorylated, with mono‐ to tetraphosphorylation being substantially more prominent than penta‐ to hexaphosphorylation. The level and multiplicity of rhodopsin phosphorylations were reduced both with the duration of light exposure and the duration of subsequent darkness. Although showing vast differences in susceptibility to light damage, rats exposed at 5 P.M. or 1 A.M. showed similar rhodopsin phosphorylation levels and patterns. These data indicate that a process controlled by circadian rhythm other than rhodopsin phosphorylation is involved either in damaging or mediating the damage evoked by intense light exposure.
A Comparison of the Sensitivity of Photodamage Assays in Rat Basophilic Leukemia Cells¶
Authors: Barth Erin E. , Hallworth Richard , Nichols Michael G.
Published: July 2010

Many aspects of cellular function or physiology can be used to indicate the level of damage resulting from the application of potentially deleterious agents such as drugs, solvents or even light. The dose required to reach a specific biological endpoint will necessarily depend on the characteristics of the damage induced by the agent. By using multiple biological probes, it is possible to get a more complete description of the type of damage induced. Photodamage was induced in rat basophilic leukemia cells by either 254‐nm UVC light exposure or rose bengal photosensitization. Damage was measured by three quantitative assays employing fluorescent probes: calcein, to measure nonspecific esterase activity, propidium iodide (PI), to measure loss of plasma membrane integrity, rhodamine 123 (R123) to measure mitochondrial depolarization, and the incorporation of 5′‐bromodeoxyuridine (BrdU), to measure the progress of cell replication. BrdU incorporation was found to be the most sensitive indicator for both forms of photodamage. For UVC photodamage, the BrdU assay was 330 times more sensitive than the other two assays. For rose bengal photosensitization, the BrdU assay was 48 or 62 times more sensitive than either the R123 or calcein/PI assays, respectively.
Environmental UV‐A and UV‐B Threshold Doses for Apoptosis and Necrosis in Humans Fibroblasts¶
Authors: Matta Jaime L. , Ramos Juan M. , Armstrong Roy A. , D'Antoni Hector
Published: July 2010

Apoptosis involves a highly organized and programmed series of events aimed at maintaining genomic stability by eliminating defective host cells. The purpose of this study was to determine the threshold doses and environmental UV‐A and UV‐B exposure times necessary to produce apoptosis and necrosis in the normal cells of a human fibroblast cell line. Enviromental UV‐A and UV‐B doses were measured over a 6 year period with a four‐channel UV radiometer. The fibroblasts were irradiated once using an Oriel UV Solar Simulator with six doses of environmentally‐based UV. Doses corresponded to 0,11,19,23 and 45 min of average environmental UV‐A and UV‐B radiation at solar noon in Puerto Rico. The Annexin‐V binding method was used to differentiate between normal fibroblasts and apoptotic or necrotic fibroblasts. The threshold dose from apoptosis to necrosis was found between 24–28 kJ/m2, which corresponded to 19 and 23 min of environmental UV‐A and UV‐B exposure. This study provides the first data that specify the environmental threshold doses of UV‐A and UV‐B at which human fibroblasts undergo apoptosis and necrosis. These results may provide valuable dose‐response thresholds for apoptosis and necrosis for future mechanistic studies and baseline data for skin cancer prevention programs.
Studies on the Subcellular Localization of the Porphycene CPO¶
Authors: Kessel David , Conley Mary , Graç M. , Vicente H. , Reiners John J.
Published: July 2010

This study was designed to provide more detailed information on the subcellular sites of binding of the porphycene, termed 9‐capronyloxytetrakis (methoxyethyl) porphycene (CPO), with a fluorescence resonance energy transfer (FRET) technique. The proximity of CPO to two fluorescent probes was determined: nonyl acridine orange (NAO), a dye with specific affinity for the mitochondrial lipid cardiolipin, and dihexaoxacarbocyanine iodide (DiOC6), an agent that labels the endoplasmic reticulum (ER). FRET spectra indicated energy transfer between DiOC6 and CPO but no significant transfer between NAO and CPO. These results confirm data obtained by fluorescence microscopy, suggesting a similar pattern of subcellular localization by CPO and DiOC6 but not by CPO and NAO. However, when cells containing CPO were irradiated and then loaded with NAO, FRET between the two fluorophores was observed. Hence, a relocalization of CPO can occur during irradiation. These data provide an explanation for recent studies on CPO‐catalyzed photodamage to both ER and mitochondrial Bcl‐2.
Photosynthetically Active Sunlight at High Southern Latitudes¶
Authors: Frederick John E. , Liao Ylxiang
Published: July 2010

A network of scanning spectroradiometers has acquired a multiyear database of visible solar irradiance, covering wavelengths from 400 to 600 nm, at four sites in the high‐latitude Southern Hemisphere, from 55°S to 90°S. Monthly irradiations computed from the hourly measurements reveal the character of the seasonal cycle and illustrate the role of cloudiness as functions of latitude. Near summer solstice, the combined influences of solar elevation and the duration of daylight would produce a monthly irradiation with little latitude dependence under clear skies. However, the attenuation associated with local cloudiness varies geographically, with the greatest effect at the most morthern locations, Ushuaia, Argentina and Palmer Station on the Antartic Peninusula. Near summer solstice, the South Pole experiences the largest monthly irradiation of the sites studied, where relatively clear skies contribute to this result. Scaling factors derived from radiative‐transfer calculations combined with the measured 400–600 nm irradiances allow estiamting irradiances integrated over the wavelength band 400–700 nm. This produces a climatology of photosynthetically active radiation for each month of the year at each site.