bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of Cyanobacterial Phytochromes in Growth Under Different Light Qualitities and Quantities¶
Authors: Fledler Brita , Broc David , Schubert Hendrik , Rediger Anne , Börner Thomas , Wilde Annegret
Published: July 2010

Inactivation of the genes for the cyanobacterial phytochromes cph1 and cph2 in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 affected the growth of the cells under certain light conditions. Differences in growth were detected by recording growth curves and in competition experiments. Mutation of cph1 and cph2 resulted in different effects. The cph1− mutant strains exhibited a reduced growth rate under far‐red light (FRL), whereas the growth of the cph2− mutant strains was inhibited by red light (RL). The growth rate of a cphl−/cph2− double mutant was reduced under both RL and FRL. Furthermore, cph1−, cph2− as well as double‐mutant strains showed impaired growth under high‐light (HL) conditions. Acclimation of the photosynthetic apparatus of the mutants to RL, FRL and HL, as determined by pigment analysis, was similar to that of the wild type.
Molecular Contrast Optical Coherence Tomography: A Review¶
Authors: Yang Changhuei
Published: July 2010

This article reviews the current state of research on the use of molecular contrast agents in optical coherence tomography (OCT) imaging techniques. After a brief discussion of the basic principle of OCT and the importance of incorporating molecular contrast agent usage into this imaging modality, we shall present an overview of the different molecular contrast OCT (MCOCT) methods that have been developed thus far. We will then discuss several important practical issues that define the possible range of contrast agent choice, the design criteria for engineered molecular contrast agent and the implementability of a given MCOCT method for clinical or biological applications. We will conclude by outlining a few areas of pursuit that deserve a greater degree of research and development.
Two‐photon Excitation Induced Fluorescence of a Trifluorophore‐labeled DNA¶
Authors: Jockusch Steffen , Li Zengmin , Ju Jingyue , Turro Nicholas J.
Published: July 2010

Two‐photon excitation of a trifluorophore (6‐carboxyfluorescein, N, N, N′, N′‐tetramethyl‐6‐carboxyrhodamine and cyamine‐5 monofunctional dye) labeled DNA, which has a scaffold of 26 nucleotides, was achieved using focused laser light of a Q‐switched Nd‐YAG laser (1064 nm). The observed fluorescence signature (emission ratio from the three fluorophores) of the labeled DNA after two‐photon excitation is very different from the fluorescence signatures produced by one‐photon excitation at different wavelenght. The additional fluorescence signatures produced by two‐photon excitation of the fluorescent oligonucleotides will facilitate their use as combinatorial fluorescence energy transfer tags for multiplex genetic analysis.
Photochemistry and Phototoxicity of Fluocinolone 16,17‐Acetonide¶
Authors: Miolo Giorgia , Caffieri Sergio , Daizoppo Daniele , Ricci Andrea , Fasani Elisa , Albini Angelo
Published: July 2010

Fluocinolone 16,17‐acetonide is a corticosteroid used topically to treat various inflammatory skin diseases. Its photoreactivity was studied under UV‐A and UV‐B light in aqueous buffer in the presence of oxygen. This drug is photolabile under UV‐B light and, to a lesser extent, under UV‐A light, which is absorbed far less. In phosphate buffer, approximately 80% of fluocinolone acetonide decomposes after 5 J/cm2 of UV‐B irradiation, whereas under 30 J/cm2 of UV‐A light approximately only 20% decomposes. Both the drug and its photoproducts have been evaluated through a battery of in vitro studies and found to cause photohemolysis and induce photodamage to proteins (erythrocyte ghosts, bovine serum albumin) and linoleic acid. In addition, one of the photoproducts (the 17‐hydroperoxy derivative) is highly toxic in the dark. Therefore, both loss of therapeutic activity and light‐induced adverse effects may be expected when patients expose themselves to sunlight after drug administration. A major mechanism for phototoxicity involves radicals forming from drug breakdown, at least under UV‐B, although reactive oxygen species may play a role, particularly under UV‐A.
The Ultraviolet Radiation Environment of High Southern Latitudes: Springtime Behavior over a Decadal Timescale¶
Authors: Liao Yixiang , Frederick John E.
Published: July 2010

Four spectroradiometers located at latitudes from 55° to 90°S conducted near‐continuous measurements of ground‐level solar ultraviolet irradiance from 1990 through 2001. The behavior during months from October through December is of special interest because this period includes the springtime loss in column ozone and the naturally large irradiances of early summer. Monthly integrated irradiances using biological weightings for erythema and damage to DNA show a distortion of the normal annual cycle in irradiance, with enhanced values occurring in October and November. In some cases, these irradiances exceed those near summer solstice in December. Changes in local cloudiness and column ozone both contribute significantly to interannual variability in erythemal irradiance. This is particularly the case at Palmer Station, near 65°S, where the monthly integrated erythemal irradiance in November 1997 was more than double that observed 5 years earlier. In general, at sites on the Antarctic continent, interannual variability in monthly integrated erythemal irradiance is greatest in November, when the observation for any given year can fall 40% above or below the multiyear mean. Near the tip of South America, interannual variability is approximately half that seen in Antarctica.
Sensitized Photooxidation of Thyroidal Hormones. Evidence for Heavy Atom Effect on Singlet Molecular Oxygen [O2(1Δg)]‐mediated Photoreactions¶
Authors: Miskoski Sandra , Soltermann Arnaldo T. , Molina Patricia G. , Gönther Germán , Zanocco Antonio L. , García Norman A.
Published: July 2010

Thyronine derivatives are essential indicators of thyroid gland diseases in clinical diagnosis and are currently used as standards for developing ordinary biochemical assays. Photooxidation of gland hormones of the thyronine (TN) family and structurally related compounds (TN, 3,5‐diiodo‐thyronine,3,3′,5‐triiodothyronine and 3,3′,5,5′‐tetraiodothyronine or thyroxine) was studied using rose bengal, eosin and perinaphthenone (PN) as dye sensitizers. Tyrosine (Tyr) and two iodinated derivatives (3‐iodotyrosine and 3,5‐diiodotyrosine) were also included in the study for comparative purposes. Irradiation of aqueous solutions of substrates containing xanthene dyes with visible light triggers a complex series of competitive interactions, which include the triplet excited state of the dye (3Xdye*) and singlet molecular oxygen [O2(1Δg)]‐mediated and superoxide ion‐mediated reactions. Rate constants for interaction with the 3Xdye*, attributed to an electron transfer process, are in the order of 108‐109M−1 s−1 depending on the dye and the particular substrate. The photosensitization using PN follows a pure Type‐II (O2(1Δg) mediated) mechanism. The presence of the phenolic group in Tyr, TN and iodinated derivatives dominates the kinetics of photooxidation of these compounds. The reactive rate constants, kr, and the quotient between reactive and overall rate constants (krlkt values, in the range of 0.7–0.06) behave in an opposite fashion compared with the overall rate constants and oxidation potentials. This apparent inconsistency was interpreted on the basis of an internal heavy atom effect, favoring the intersystem‐crossing deactivation route within the encounter complex with the concomitant reduction of effective photooxidation.
Interaction of UV Radiation and Inorganic Carbon Supply in the Inhibition of Photosynthesis: Spectral and Temporal Responses of Two Marine Picoplankters¶
Authors: Sobrino Cristina , Neale Patrick J. , Lubián Luis M.
Published: July 2010

The effect of ultraviolet radiation (UVR) on inhibition of photosynthesis was studied in two species of marine picoplankton with different carbon concentration mechanisms: Nannochloropsis gaditana Lubián possesses a bicarbonate uptake system and Nannochloris atomus Butcher a CO2 active transport system. Biological weighting functions (BWFs) for inhibition of photosynthesis by UVR and photosynthesis vs irradiance (PI) curves for photosynthetically active radiation (PAR) were estimated for both species grown with an enriched CO2 supply (high dissolved inorganic carbon [DIC]: 1% CO2 in air) and in atmospheric CO2 levels (low DIC: 0.03% CO2). The response to UVR and PAR exposures was different in each species depending on the DIC treatment. Under PAR exposure, rates of maximum photosynthesis were similar between treatments in N. gaditana. However, the cultures growing in high DIC had lower sensitivity to UVR than the low DIC cultures. In contrast, N. atomus had higher rates of photosynthesis under PAR exposure with high DIC, but the BWFs were not significantly different between treatments. The results suggest that one or more processes in N. gaditana associated with HCO3− transport are target(s) for UV photodamage because there was relatively less UV inhibition of the high DIC‐grown cultures in which inorganic carbon fixation is supplied by passive CO2 diffusion. Time courses of photochemical efficiency in PAR, during UV exposure and during subsequent recovery in PAR, were determined using a pulse amplitude modulated fluorometer. The results were consistent with the BWFs. In all time courses, a steady state was obtained after an initial decrease, consistent with a dynamic balance between damage and repair as found for other phytoplankton. However, the relationship of response to exposure showed a steep decline in activity that is consistent with a constant rate of repair. A novel feature of a model developed from a constant repair rate is an explicit threshold for photosynthetic response to UV.
Effects of lodide on the Fluorescence and Activity of the Hydroperoxyflavin Intermediate of Vibrio harveyi Luciferase¶
Authors: Huang Shouqin , Tu Shiao‐Chun
Published: July 2010

The 4a‐hydroperoxy‐4a,5‐dihydroFMN intermediate (II or HFOOH) of Vibrio harveyi luciferase is known to transform from a low quantum yield IIx to a high quantum yield (λmax 485 nm, uncorrected) IIy fluorescent species on exposure to excitation light. Similar results were observed with II prepared from the αH44A luciferase mutant, which is very weak in bioluminescence activity. Because of the rapid decay of the αH44A II, its true fluorescence was obscured by the more intense 520 nm fluorescence (uncorrected) from its decay product oxidized flavin mononucleotide (FMN). Potassium iodide (KI) at 0.2 M was effective in quenching the FMN fluorescence, leaving the 485 nm fluorescence of II from both the wild‐type (WT) and αH44A luciferase readily detectable. For both II species, the luciferase‐bound peroxyflavin was well shielded from KI quenching. KI also enhanced the decay rates of both the WT and αH44A II. For αH44A, the transformation of IIx to IIy can be induced by KI in the dark, and it is proposed to be a consequence of a luciferase conformational change. The WT II formed a bioluminescence‐inactive complex with KI, resulting in two distinct decay time courses based on absorption changes and decreases of bioluminescence activity of II.
Molecular Beacon Probes of Photodamage in Thymine and Uracil Oligonucleotides¶
Authors: Yarasi Soujanya , McConachie Cheryl , Loppnow Glen R.
Published: July 2010

Molecular beacons (MB) are becoming more common as sequence‐selective detectors of nucleic acids. Although they can easily detect single‐base mismatches, they have never been used to directly detect DNA or RNA damage. To measure the degree of ultraviolet (UV) light damage in oligonucleotides, we report a novel MB approach for general detection of photoproducts in UV‐irradiated rU17 and dT17 oligonucleotides. With monochromatic UV light irradiation at ca 280 nm under anoxic conditions, the oligonucleotide absorption decays with a single‐exponential time constant of 123 ± 1 min for rU17 and with double‐exponential time constants of 78 ± 0.5 min (99%) and 180 ± 5 min (0.05%) for dT17 oligonucleotides. Under the same conditions, the MB fluorescence decays more quickly, with single‐exponential time constants of 19 ± 2 and 26 ± 3 min for rU17 and dT17, respectively. Similar kinetics were observed with broadband UV light irradiation of oligonucleotides. The differences in the UV damage kinetics of dT17 and rU17 and their detection by absorption and fluorescence techniques will be discussed in the context of differential instabilities introduced in the nucleic acid‐MB duplex by the different photoproducts formed.
An Action Spectrum of the Riboflavin‐photosensitized Inactivation of Lambda Phage¶
Authors: Martin Christopher B. , Wilfong Erin , Ruane Patrick , Goodrich Raymond , Platz Matthew
Published: July 2010

The Action Spectrum of riboflavin (RB) sensitized inactivation of lambda phage was determined between 266 and 575 nm. Below 304 nm, RB depresses the phage reduction by screening phage from radiation that it would otherwise absorb directly. Between 308 and 525 nm, RB sensitizes the inactivation of phage. Enhanced phage reduction is observed at 320 and 500 nm because of binding of RB to the phage and the shifting of the absorption curve of the phage‐bound flavin relative to free flavin in phosphate‐buffered saline. Enhanced inactivation at 320 and 500 nm and depressed phage inactivation between 360 and 410 nm is also influenced by the inner filter effect.
Update on the Positive Effects of Light in Humans†
Authors: Roberts Joan E.
Published: July 2010

The adverse effects of sunlight, from melanoma to cataracts, are well known and frequently reported (1). However, because humans evolved under sunlight, it is not surprising that there are many positive effects of light on human health. Light that reaches the human eye has two fundamental biological functions: regulation of the visual cycle and of circadian rhythm. We report here the most recent developments in both of these areas.
Long‐term Lens Organ Culture System with a Method for Monitoring Lens Optical Quality¶
Authors: Dovrat A. , Sivak J. G.
Published: July 2010

The Scan Tox™ System is a method for monitoring lens optical quality (focus or lack of focus) in culture conditions, which mimic conditions inside the eye. The ocular lens is an ideal organ for long‐term culture experiments because it has no direct blood supply and no connection to the nervous system. The Scan Tox™ System makes it possible to keep lenses for long‐term studies of up to a few weeks. The use of cultured lenses, mainly bovine, replaces the need for testing the effects of potentially damaging agents on live animals. This optical monitoring apparatus uses a computer‐operated scanning laser beam, a video‐camera system and a video frame analyzer to record the focal length and transmittance of the cultured lens. The scanner is designed to measure the focal length at points across the diameter of the lens. The lens container permits the lens to be exposed to a vertical laser beam from below. The laser source projects its light onto a plain mirror, which is mounted at 45° on a carriage assembly. The mirror reflects the laser beam directly up through the test lens. The mirror carriage is connected to a positioning motor, which moves the laser beam across the lens. The camera sees the cross section of the beams and, by examining the image at each position of the mirror, Scan Tox™ software is able to measure the quality of the lens by calculating the back vertex distance for each beam position. The cultured lenses continue to maintain their original refractive function. When foreign substances are introduced to a cultured lens, the Scan Tox™ System measures the resulting optical response. This provides a very sensitive means to follow early damage to the eye lens. Because the lens is maintained in an intact state in solutions that are similar to those inside the eye, the lens retains its normal recuperative powers. So in addition to measuring early damage, this system allows measurement of recovery from damage.
Phototoxicity of Indocyanine Green on Human Retinal Pigment Epithelium in Vitro and its Reduction by Lutein¶
Authors: Wu Wen‐Chuan , Hu Dan‐Ning , Roberts Joan E.
Published: July 2010

Previous work has shown that indocyanine green (ICG)‐assisted peeling of the internal limiting membrane during vitreoretinal surgery may damage the retinal pigment epithelium (RPE). The present study tested the direct toxic effects and phototoxic effects of ICG on cultured human RPE. RPE cells were exposed to ICG (0.5%, 5 min) with or without lutein (20 μM), followed by light irradiation at different doses of light energy (1.0,3.0 and 10.0 J/cm2). After 48 h, cells were collected and stained with trypan blue to obtain the number of viable and nonviable cells in different groups. Cultures exposed to ICG without light irradiation showed a significant decrease of viable cells (‐13.3%) and an increase of nonviable cells (x2.5‐fold) compared with cultures not exposed to either ICG or light, indicating the presence of direct toxic effects of ICG. In cultures exposed to ICG plus light irradiation (10.0 J/cm2), viable cells decreased significantly (‐45.0%) and nonviable cells increased significantly (x4.4‐fold) compared with cultures exposed to ICG alone. The damage to the RPE cells depended on the dose of light (1.0–10.0 J/cm2), indicating that ICG has a phototoxic effect as well as a toxic one. Lutein, an endogenous ocular antioxidant, had a protective effect on cultures exposed to ICG and light, cells treated with leutin showed an increase of viable cells (+74.6%) and decrease of nonviable cells (‐74.4%) compared with cultures without leutin but not on cultures exposed to ICG alone. Thus, it seems that photoactivated ICG kills cells through a photoxidative mechanism. Our study suggests that preoperative oral administration of lutein may protect against the phototoxic‐induced damage of ICG on the RPE cells.
Photochemical Behavior of 6‐Methylpterin in Aqueous Solutions: Generation of Reactive Oxygen Species¶
Authors: Cabrerizo Franco M. , Lorente Carolina , Vignonl Mariana , Cabrerizo Romina , Thomas Andrés H. , Capparelli Alberto L.
Published: July 2010

Pterins are a family of heterocyclic compounds present in a wide range of living systems that participate in relevant biological functions and are involved in different photobiological processes. 6‐Methylpterin (MPT) was investigated for its efficiency of singlet‐oxygen (1O2) production and quenching in aqueous solution. The quantum yields of 1O2 production (φΔ) was determined by measurements of the 1O2 luminescence in the near‐infrared upon continuous excitation of the sensitizer. Values of φΔ were found to be 0.10 ± 0.02 and 0.14 ± 0.02 in acidic and alkaline media, respectively. Studies of the photo‐oxidation of MPT in acidic (pH = 5.0–6.0) and alkaline (pH = 10.2–10.8) aqueous solutions at 350 nm and room temperature have been performed. The photochemical reactions were followed by UV‐visible spectrophotometry, high‐performance liquid chromatography and an enzymatic method for H2O2 determination. MPT is not light sensitive in the absence of oxygen, but it undergoes a photooxidation reaction in the presence of oxygen, yielding several nonpteridinic products. The quantum yields of MPT disappearance were determined and values of 2.4 (±0.5) × 10−4 and 8.1 (±0.8) × 10−4 were obtained in acidic and alkaline media, respectively. H2O2 was detected and quantified in irradiated solutions of MPT. The rate constant of the chemical reaction between 1O2 and MPT (kr) was determined to be 4.9 × 106M−1 s−1 in alkaline medium and the role of 1O2 in the photooxidation of MPT is discussed.
Proteome Analysis of UV‐B‐Induced Anti‐apoptotic Regulatory Factors¶
Authors: Ibuki Yuko , Naitou Hirotaka , Ohashi Norio , Goto Rensuke
Published: July 2010

Ultraviolet (UV) irradiation is well known to induce apoptosis, a hallmark event of which is the occurrence of sunburn cells in the epidermis. Keratinocytes in which DNA damaged by UV irradiation is not repaired undergo apoptosis as sunburn cells. However, we have previously reported that low‐dose UV‐B irradiation (∼0.1 J/cm2) suppressed the apoptosis induced by cell detachment and serum depletion. Dysregulation of apoptosis is important in tumor progression and malignancy and in promoting resistance to cancer therapy. To develop a better understanding of the antiapoptotic effect of UV irradiation, and to design the effective induction of apoptosis, we tried the proteome analysis of the molecules regulating apoptosis in low‐dose UV‐B‐irradiated NIH3T3 cells, using two‐dimensional difference gel electrophoresis (DIGE). Of a total of 3811 protein spots detected, 42 were found to be different between the cells undergoing apoptosis and cells after the irradiation. Of the spots selected, 25 were identified using MALDI‐TOF/TOF‐MS, some as structural proteins. Although typical apoptosis‐related molecules were not detected, possibly because proteins with low molecular weights were difficult to identify in the gel conditions used in this study, some of the proteins were considered to be involved in apoptosis. The DIGE system used in this experiment has advantages (including a high level of statistical confidence) for discovering new functional proteins related to the regulation of apoptosis.
Photophysical Parameters, Photosensitizer Retention and Tissue Optical Properties Completely Account for the Higher Photodynamic Efficacy of meso‐Tetra‐Hydroxyphenyl‐Chlorin vs Photofrin¶
Authors: Mitra Soumya , Foster Thomas H.
Published: July 2010

Meso‐tetra‐hydroxyphenyl‐chlorin (mTHPC) is one of the most potent photosensitizers currently available for clinical photodynamic therapy (PDT). However the reason or reasons for its high photodynamic efficacy remain(s) unresolved. To investigate the PDT efficacy of mTHPC vs Photofrin we use the knowledge of photophysical parameters extracted from the analysis of oxygen electrode measurements in spheroids to compute and compare their respective singlet oxygen (1O2 dose depositions. The electrode measurements indirectly report the bleaching kinetics of mTHPC and indicate that its photobleaching mechanism is consistent with 1O2‐mediated reactions. mTHPC's photodegradation via1O2 reactions is confirmed by a more direct evaluation of the spatially resolved fluorescence in confocal sections of intact spheroids during irradiation. The PDT efficacy comparisons establish that mTHPC's enhanced potency may be accounted for completely on the basis of its ability to sequester tightly in cells and its photophysical properties, in particular its higher extinction coefficient at a redshifted wavelength. We extend the efficacy comparison to include the influence of hemoglobin absorption of PDT treatment light and show that incorporating the influence of wavelength‐dependent light attenuation in tissue further contributes to significantly higher efficacy for mTHPC‐ vs Photofrin‐PDT.
Effect of Digitonin on the Rhodopsin Meta I‐Meta II Equilibrium¶
Authors: Szundi Istvan , Lewis James W. , Kliger David S.
Published: July 2010

Absorbance difference spectra were recorded from 10 μs to 540 ms after photoexcitation of sonicated suspensions of hypotonically washed bovine rod outer segments with varying amounts of the detergent digitonin added (0 to 2%) at 20°C. Metarhodopsin I480 and metarhodopsin II displayed the expected anomalous pH dependence at pH 6 and 8 (i.e. opposite to that expected from direct protonation of the chromophore Schiff base). However, increasing levels of digitonin eliminated the pH dependence of the equilibrium, and at 2% digitonin the pH 6 and pH 8 data were both similar to the data collected at pH 8 without digitonin. Addition of 0.5% azolectin restored approximately 50% of the anomalous pH dependence at pH 6 in the 2% digitonin sample. The possibility that digitonin induced large‐scale aggregation of rhodopsin in the disk membrane that could be reversed by azolectin was tested using time‐resolved linear dichroism. Those results showed that even 0.3% digitonin disrupted the membrane, and no large aggregates were detectable under any conditions. Thus, digitonin reduces the activity of a component of the disk membrane required for metarhodopsin II formation, and that deficiency can be compensated for by azolectin.
Virus Particles and Receptor Interaction Monitored by Fluorescence Spectroscopy¶
Authors: Alimova Alexandra , Katz A. , Podder Rakhi , Minko Glenn , Wei Hui , Berriman John , Alfano R. R. , Gottlieb Paul
Published: July 2010

Native fluorescence spectroscopy (NFS), primarily from tryptophan (trp), was used for in situ investigation of the virus‐receptor attachment process in φ6, a lipid‐containing bacteriophage from the Cystoviridae family. NFS allowed us to monitor the viral attachment directly to its receptor, which was isolated from the pseudomonad host. Immediately upon mixing, an increase in tryptophan emission intensity was observed followed by a subsequent decrease in emission intensity. The initial increase in emission intensity reflects changes in trp quantum efficiency as the φ6 surface proteins change their conformation as a result of virus attachment to the pilus. The cystovirus spike protein P3 is responsible for receptor recognition and the fluorescence changes observed are likely to be the consequence of its conformational transition at this initial infection stage, providing a kinetic view of this process. The subsequent decrease in trp emission intensity could be due to changes in viral proteins as a result of disassembly of the pili. The technique may have important applications for the dynamic monitoring of additional stages of the virus replication cycle such as assembly, interaction with nucleic acids and maturation. This work expands on a previous demonstration that fluorescence offered a novel tool to detect virus particle interaction with its host cell.
Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials¶
Authors: Petrov E. P. , Clchos F. , Wagner F. , Spange St. , von Borczyskowski C.
Published: July 2010

Distibazolium dyes are investigated by steady‐state and time‐resolved fluorescence techniques in a series of low‐ and highviscosity polar solvents and in a silica sol‐gel matrix. In all solvents and the sol‐gel matrix, an interplay of photoinduced switching between different cis‐trans isomers and solvation dynamics is observed. Even in a viscous solution (glycerol) and in silica gel, cis‐trans isomerization is solvent‐controlled. Whereas in glycerol the solvation results in a time‐dependent fluorescence Stokes shift, the solvation‐induced spectral heterogeneity in silica gel is mostly static, possibly due to a close proximity of dye molecules to the silica surfaces of the nanopores. Compared to low‐viscosity solvents, where the cis‐trans isomerization process takes place with a solvent‐dependent rate on the timescale of about 120–150 ps, it slows down to about 1100–1400 ps in glycerol and about 1500 ps in a sol‐gel matrix. Additionally, fluorescence kinetics of the dyes in the sol‐gel reveals the presence of a range of different “frozen‐in” conformers exhibiting a broad spectrum of lifetimes from 20 to 300 ps.
Photophysical Properties of Methyl Triazone Included in MCM‐41¶
Authors: Ricci Andrea , Chrétien Michelle N. , Sayari Abdelhamid , Scaiano J. C.
Published: July 2010

Methyl triazone (4,4′,4″‐[l,3,5‐triazine‐2,4,6–triyItriimino]tris‐trimethyl benzoate) has been included in mesoporous MCM‐41 (Mobil's composition of matter‐41) silica, and its fluorescence emission has been compared in solution and in the solid state. Although inclusion does not affect significantly the absorption properties, a fluorescence emission shift and a behavior similar to the solid state has been observed by increasing the loading. It is believed that this observation reflects molecular aggregation inside the MCM‐41 channels. The potential of formulations of this type for sunscreen applications is discussed.
Protective Effects of an Antioxidant Derived from Serine and Vitamin B6 on Skin Photoaging in Hairless Mice¶
Authors: Kitazawa Manabu , Ishitsuka Yukiko , Kobayashi Misako , Nakano Takashi , Iwasaki Keiji , Sakamoto Kazutami , Arakane Kumi , Suzuki Tadashi , Kligman Lorralne H.
Published: July 2010

The generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N‐(4‐pyridoxylmethylene)‐L‐serine (PYSer) was designed as an antioxidant to suppress iron‐catalyzed ROS generation by its iron‐sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV‐B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV‐B irradiation. A histological study indicated that UV‐B‐induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV‐B‐induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron‐sequestering activity.
Monitoring Cell Survival After Extraction of a Single Subcellular Organelle Using Optical Trapping and Pulsed‐Nitrogen Laser Ablation¶
Authors: Shelby J. Patrick , Edgar J. Scott , Chiu Daniel T.
Published: July 2010

This paper characterizes cell viability in three different cell lines—Chinese hamster ovary cells (CHO), neuroblastoma cells fused with glialoma cells (NG108‐15) and murine embryonic stem cells (ES‐D3)—after N2 laser disruption of the cell membrane and removal, via optical trapping, of a single subcellular organelle. Morphological changes and viability (as determined by live/dead fluorescent stains) of the cell were monitored every half hour over a 4‐h period postsurgery. The ability of the cell to survive organelle extraction was found to depend both on the conditions under which surgery was performed and on the cell type. The average viability after surgery for CHO cells was approximately 80%, for NG 108 cells it was approximately 30% and for ES‐D3 cells postsurgery viability was approximately 10%. From over 600 surgeries we found the survival of the cell is determined almost exclusively within the first hour postsurgery regardless of cell line. The optimal pulse energy for N2 laser ablation was approximately 0.7 μJ. The N2 pulse produced an approximately 1–3 μm hole in the cell membrane and proved to be the primary source of cell death in those cells that did not survive the procedure.
UV‐A Fingerprint Mutations in Human Skin Cancer¶
Authors: Halliday Gary M. , Agar Nita S. , Barnetson Ross St.C. , Ananthaswamy Honnavara N. , Jones Alexandra M.
Published: July 2010

This review of our work, presented at the Photocarcinogenesis Symposium of the 14th International Congress on Photobiology, shows that UV‐A causes a similar number of gene mutations as UV‐B in human skin cancer. Areas of about 20 keratinocytes from solar keratoses and squamous cell carcinomas, which are benign and malignant skin cancers, respectively, were sampled by laser capture microdissection. Automated sequencing of the p53 gene was used to detect mutations in these tumor areas, and the cause of the mutations was attributed on the basis of previously published studies. UV‐A and UV‐B caused similar numbers of p53 gene mutations in both benign and malignant human skin tumors, with UV‐B–induced mutations being restricted to the upper areas of the tumors and UV‐A–induced mutations predominating at the basal layer. Furthermore, each microdissected region within a tumor had distinct mutations showing that the skin tumors consisted of different clones of cells. This is not consistent with how human skin carcinogenesis is currently understood, and hypotheses to explain our data are presented. We propose that the UV‐A waveband of sunlight is as important as UV‐B in causing skin cancer in humans.
Inverse Relationship Between Increased Apoptosis and Decreased Skin Cancer in UV‐irradiated CD1d‐/‐ Mice¶
Authors: Matsumura Yasuhiro , Moodycliffe Angus M. , Nghiem Dat X. , Ullrich Stephen E. , Ananthaswamy Honnavara N.
Published: July 2010

We previously demonstrated that CD1d knockout mice were resistant to ultraviolet (UV)‐induced immunosuppression. Because immune suppression is a critical factor in the development of UV‐induced skin cancers, we investigated the response of wild type (WT) and CD1d‐/‐ mice to UV carcinogenesis. We found that although 100% of WT mice developed skin tumors after 45 weeks of UV irradiation, only 60% of CD1d‐/‐ mice developed skin tumors. To investigate the mechanisms involved in the resistance of CD1d‐/‐ mice to UV‐induced carcinogenesis, we determined the time course and kinetics of keratinocyte cell death after UV irradiation. After acute UV exposure, the terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end‐labeling (TUNEL)‐positive keratinocytes were eliminated from the skin of WT mice by 72 h post‐UV, but they still persisted until 96 h in CD1d‐/‐ mice. The kinetics of p53 protein expression closely followed the kinetics of apoptotic cell death. Chronic UV irradiation resulted in induction of a significantly higher number of apoptotic keratinocytes in CD1d‐/‐ than WT mice. In addition, epidermis and dermis from chronically UV‐irradiated CD1d‐/‐ mice harbored significantly fewer p53 mutations than WT mice. These results indicate that the resistance of CD1d‐/‐ mice to UV carcinogenesis may be due to increased cell death and elimination of keratinocytes and fibroblasts containing DNA damage and p53 mutations.
UV Exposure, Genetic Targets in Melanocytic Tumors and Transgenic Mouse Models¶
Authors: de Gruijl Frank R. , Van Kranen Henk J. , Van Schanke Arne
Published: July 2010

The genetic changes and corruption of kinase activity in melanomas appear to revolve around a central axis: mitogenic signaling along the RAS pathway down to transcription regulation by pRB. Epidemiological studies point to the importance of ultraviolet (UV) radiation in the etiology of melanoma, but where and how UV radiation is targeted to contribute to the oncogenic signaling remains obscure. Animal models of melanoma genesis could serve to clarify this issue, but many of these models are not responsive to UV exposure. Most interesting advances have been made by using transgenic mice that carry genetic defects that are known to be relevant to human melanoma: specifically, dysfunction in the tumor suppressive action of p161NK4a or a receptor tyrosine kinase/RAS pathway, that is constitutively activated in melanocytes. The latter types of mice appear to be most responsive to (neonatal) UV exposure. Whether this is due to a general increase in target cells by melanocytosis and a paucity or complete lack of pigment, or a possible UV‐induced response of the promoter–enhancer of the transgene or a genuinely independent and additional genetic alteration caused by UV exposure needs to be established. Importantly, the full effect of UV radiation needs to be ascertained in mice with different pigmentation by varying the wavelengths, UV‐B versus UV‐A1, and the exposure schedules, i.e. neonatal versus adult and chronic versus intermittent overexposure. Intermittent UV‐B overexposure deserves special attention because it most strongly evokes proliferative responses in melanocytes.
DNA Molecular Photonics¶†
Authors: Lewis Frederick D.
Published: July 2010

Synthetic DNA conjugates in which one or both ends of a short duplex is capped by a stilbene chromophore have been prepared and characterized crystallographically. Selective excitation of the chromophore can be used to initiate electron transfer processes in which a nucleobase serves as either an electron donor or an electron acceptor. These processes include hole‐ and electron injection and hole migration. The dynamics of these processes and its dependence on distance, driving force, and base sequence have been investigated by means of femtosecond time‐resolved spectroscopy. Duplexes with identical chromophores at both ends have been used to study both the dynamics of electron transfer processes and exciton coupling between the two chromophores by means of circular dichroism spectroscopy. Duplexes with different chromophores can also be used to study distance dependence of both electron transfer and exciton coupling.
Comparison of Structural and Chemical Properties of Black and Red Human Hair Melanosomes¶
Authors: Liu Yan , Hong Lian , Wakamatsu Kazumasa , Ito Shosuke , Adhyaru Bhavin , Cheng Chi‐Yuan , Bowers Clifford R. , Simon John D.
Published: July 2010

Melanosomes in black and red human hair are isolated and characterized by various chemical and physical techniques. Different yields of 4‐amino‐hydroxyphenolanaline by HI hydrolysis (a marker for pheomelanin) and pyrrole‐2,3,5‐tricarboxylic acid by KMnO4/H+ oxidation (a marker for eumelanin) indicate that the melanosomes in black hair are eumelanosomes, whereas those in red hair are mainly pheomelanosomes. Atomic force microscopy reveals that eumelanosomes and pheomelanosomes have ellipsoidal and spherical shapes, respectively. Eumelanosomes maintain structural integrity upon extraction from the keratin matrix, whereas pheomelanosomes tend to fall apart. The black‐hair eumelanosomes have an average of 14.6 ± 0.5% amino acids content, which is attributed to the internal proteins entrapped in the melanosomes granules. The red‐hair melanosomes contain more than 44% of amino acid content even after extensive proteolytic digestion. This high content of amino acids and the poorly reserved integrity of red‐hair melanosomes suggest that some proteins are possibly covalently bonded with the melanin constituents in addition to those that are entrapped inside the melanin species. Soluene solubilization assay indicates the absorbance of melanin per gram of sample, adjusted for the amino acid content, is a factor of 2.9 greater for the black‐hair melanosomes than the red‐hair melanosomes. Metal analysis reveals significant amounts of diverse heavy metal ions bound to the two types of melanosomes. The amount of Cu(II) and Zn(II) are similar but Fe(III) content is four times higher in the red‐hair melanosomes. 13C solid‐state nuclear magnetic resonance spectra and infrared spectra are presented and are shown to be powerful techniques for discerning differences in the amino acid contents, the 5,6‐dihydroxyindole‐2‐carboxylic acid:5,6‐dihydroxyindole ratio, and the degree of cross‐linking in the pigment. Excellent agreement is observed between these spectral results and the chemical degradation data.
Effects of the Binding of α/β‐type Small, Acid‐soluble Spore Proteins on the Photochemistry of DNA in Spores of Bacillus subtilis and In Vitro¶
Authors: Douki Thierry , Setlow Barbara , Setlow Peter
Published: July 2010

The main lesion produced in DNA by UV‐C irradiation of spores of Bacillus subtilis is 5‐thyminyl‐5,6‐dihydrothymine (spore photoproduct [SP]). In contrast, cyclobutane pyrimidine dimers (CPD) and pyrimidine (6–4) pyrimidone photoproducts (6–4PP) are the main photolesions in other cell types. The novel photochemistry of spore DNA is accounted for in part by its reduced hydration, but largely by the saturation of spore DNA with α/β‐type small, acid‐soluble spore proteins (SASP). Using high‐performance liquid chromatography‐mass spectrometry analysis of the photoproducts, we showed that in wild‐type B. subtilis spores (1) UV‐C irradiation generates almost exclusively SP with little if any CPD and 6–4PP; (2) the SP generated is ∼99% of the intrastrand derivative, but ∼1% is in the interstrand form; and (3) there is no detectable formation of the SP analog between adjacent C and T residues. UV‐C irradiation of spores lacking the majority of their α/β‐type SASP gave less SP than with wild‐type spores and significant levels of CPD and 6–4PP. The binding of an α/β‐type SASP to isolated DNA either in dry films or in aqueous solution led to a large decrease in the yield of CPD and 6–4PP, and a concomitant increase in the yield of SP, although levels of interstrand photoproducts were extremely low.
Autophosphorylation, Electrophoretic Mobility and Immunoreaction of Oat Phototropin 1 Under UV and Blue Light¶
Authors: Knieb Elke , Salomon Michael , Rüdiger Wolfhart
Published: July 2010

Phototropins are UV‐A/blue light photoreceptors containing two flavin mononucleotide (FMN)–binding domains, light, oxygen and voltage (LOV)1 and LOV2, of which LOV2 is more sensitive toward light and more important for the physiological response compared with LOV1. Some physiological responses are plant phototropism, chloroplast migration and stomatal opening. Oat phototropin 1 together with light‐dependent autophosphorylation shows a reduced electrophoretic mobility and reduced immunoreaction against a heterologous antiserum; both effects were suggested to be caused by phosphorylation at the same sites (M. Salomon, E. Knieb, T. von Zeppelin and W. Rüdiger [2003] Biochemistry42, 4217–4225). In this study, we show that both effects can be separated from each other: at low temperature, reduced immunoreaction preceded the mobility shift, and irradiation with UV‐C light led to the mobility shift without the loss of immunoreactivity. We demonstrated that UV‐C light at 280 nm, which does not match any absorption maximum of FMN, leads to autophosphorylation of phototropin. It is hypothesized that UV‐C light causes differential activation of the LOV domains via energy transfer from aromatic amino acids.
The Separation of Hypericin's Enantiomers and Their Photophysics in Chiral Environments¶
Authors: Sanders Lindsay , Halder Mintu , Xiao Tom Ling , Ding Jie , Armstrong Daniel W. , Petrich Jacob W.
Published: July 2010

We report the first separation of the enantiomers of hypericin. Their steady‐state optical spectra and ultrafast primary photoprocesses are investigated in chiral environments. Within experimental error, there is no difference between the two enantiomers in any of the systems considered. This is consistent with the emerging picture that the rich and extended absorption spectrum of hypericin is not a result of ground‐state heterogeneity. It is also consistent with the observation that the spectra and photophysics of hypericin are generally insensitive to environments in which it does not aggregate.
Vertical Migration and Motility Responses in Three Marine Phytoplankton Species Exposed to Solar Radiation†
Authors: Richter Peter R. , Häder Donat‐P. , Gonçalves Rodrigo J. , Marcoval M. Alejandra , Villafañe Virginia E. , Helbling E. Walter
Published: July 2010

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280–400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280–700 nm), PA (320–700 nm) and P (400–700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV‐B displaying a significant decrease in swimming speed and percentage of motile cells after 2–3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub‐lethal effects of solar radiation are species‐specific and they might have important implications for the aquatic ecosystem.
Photobleaching of Melanosomes from Retinal Pigment Epithelium: I. Effects on Protein Oxidation
Authors: Burke Janice M. , Henry Michele M. , Zareba Mariusz , Sarna Tadeusz
Published: July 2010

Melanin in the long‐lived melanosomes of the retinal pigment epithelium (RPE) may undergo photobleaching with aging, which appears to diminish the antioxidant function of melanin and could make photobleached melanosomes less efficient in protecting biomolecules from oxidative modification. Here we analyzed whether photobleaching of melanosomes affects their ability to modify the oxidation state of nearby protein. As conventional methods developed to study soluble antioxidants are not well suited for analysis of granules such as melanosomes, we developed a new analytic method to focus on particle surfaces that involves experimentally coating granules with the cytoskeletal protein β‐actin to serve as a reporter for local protein oxidation. Isolated porcine RPE melanosomes were photobleached with visible light to simulate aging, then photobleached melanosomes, untreated melanosomes and control particles (black latex beads) were actin coated and illuminated in a photosensitized cell free system. Protein was re‐stripped from particles and analyzed for carbonylation by Western blotting. Quantitative densitometry showed no reproducible differences for protein associated with untreated melanosomes when compared with control particles. Melanin has both anti‐ and pro‐oxidant functions when light irradiated, but neither of these functions predominated in the protein oxidation assay when untreated melanosomes were used. However, protein extracted from photobleached melanosomes showed markedly increased carbonylation, both of associated actin and of endogenous melanosomal protein(s), and the effect increased with extent of granule photobleaching. Photobleaching of RPE melanosomes therefore changes the oxidation state of protein endogenous to the organelle and reduces the ability of the granule to modify the oxidation of exogenous protein near the particle surface. The results support the growing body of evidence that photobleaching of RPE melanosomes, which is believed to occur with aging, changes the physicochemical properties of the organelle and reduces the likelihood that the granules perform an antioxidant function.
Bid Is Required in NPe6‐PDT‐induced Apoptosis
Authors: Wan Qingling , Liu Lei , Xing Da , Chen Qun
Published: July 2010

Photodynamic therapy (PDT) employing photosensiter N‐aspartyl chlorin e6 (NPe6) can induce lysosome disruption and initiate the intrinsic apoptotic pathway. Yet the precise signal transduction pathway remains poorly understood. In this study, we have investigated the molecular mechanism in NPe6‐PDT‐induced apoptosis in human lung adenocarcinoma cells (ASTC‐a‐1). A recombinant fluorescence resonance energy transfer (FRET) Bid probe was utilized to determine the kinetics of Bid cleavage. The results show that cleavage of the Bid‐FRET probe occurred 150 ± 5 min after NPe6‐PDT treatment, and this process lasted for 45 ± 5 min. The Bid cleavage coincided with a translocation of tBid from cytoplasm to mitochondria. Remarkably, a significant protection against cell death was observed by using small interfering RNA for Bid. Therefore, our study clearly showed the dynamics of Bid activation and redistribution during NPe6‐PDT‐induced apoptosis by using real‐time analysis in living cells, and the inhibition of cell death by silencing Bid with interference strongly suggested that activation of Bid is required for inducing apoptosis in this experimental model.
Juvenile Courts Needed
Authors: Herter Hon. Christian A.
Published: July 2010

Note: The following is extracted from an address to the Massachusetts Association of Women Lawyers, in Boston.