bluuebunny/crossref_metadata_2025 huggingface dataset:
MECHANISM OF DNA CLEAVAGE MEDIATED BY PHOTOEXCITED NON‐STEROIDAL ANTIINFLAMMATORY DRUGS
Authors: Artuso Thierry , Bernadou Jean , Meunier Bernard , Piette Jacques , Paillous Nicole
Published: January 2008

Abstract–DNA damage photoinduced by four nonsteroidal antiinflammatory drugs (NSAID) have been investigated by neutral agarose gel electrophoresis. Upon irradiation at 300 nm, in phosphate buffered solution, benoxaprofen, naproxen, ketoprofen, tiaprofenic acid photosensitized the formation of single‐strand breaks (SSB) in double stranded supercoiled TH X174 DNA. The efficiency of the cleavage is higher in argon saturated solutions than in aerated solutions and it is not correlated with the quantum yield of photodegradation of the drugs. Simultaneously with the DNA strand breaks, NSAID promote a weak reduction of the electrophoretic mobility of the supercoiled form that may be attributed to the formation of pyrimidine dimers or other DNA unwinding products. These photodimerization processes suggest the involvement of a triplet‐triplet energy transfer between NSAID and DNA. Addition of mannitol and superoxide dismutase decreases the efficiency of the cleavage suggesting that HO' and O2 are involved in the DNA cleavage. Unexpectedly, addition of sodium azide quenches the cleavage both in aerated or in deaerated solutions. Substituting H2O by D2O does not change the number of SSB thus suggesting that 1O2 does not take an important place in the cleavage of DNA. From our data we tentatively assume that the cleavage occurs through a radical mechanism that may involve in a first step an energy or an electron transfer. Gel sequencing on NSAID‐photoinduced DNA breakage exhibits no particular specificity except in the case of benoxaprofen where a slight selectivity for cytosine is observed.
BORONIC ACIDS AS MECHANISTIC PROBES FOR THE BACTERIAL LUCIFERASE REACTION
Authors: Ahrens Matthias , Macheroux Peter , Eberhard Anatol , Ghisla Sandro , Branchaud Bruce P. , Hastings J. Woodland
Published: January 2008

References

Bacterial luciferase uses long chain aldehydes as substrates. Alkylboronic acid analogs of these substrates with chain lengths of C7 and C9 have been synthesized, characterized, and used as mechanistic probes for the light emitting reaction. They behave as inhibitors in the in vitro luminescence reaction. Contrary to an earlier report (Macheroux and Ghisla, 1985, Nachr. Chem. Tech. Lab. 33,785–790) they are not substrates for bacterial luciferase, in that they do not lead to light emission and are not oxidized by the flavin‐4a‐hydroperoxide to the products boric acid and the corresponding alcohol, as would be expected from a Baeyer‐Villiger reaction. However, the particular conformation of a putative boronic acid hydroperoxide at the active center might be such that it would preclude a Baeyer‐Villiger fragmentation. Thus, while the results do not support the postulate that luciferase proceeds via a Baeyer‐Villiger mechanism, they also do not exclude it. A further observation was that the endogenous light emission (no added aldehyde) decays more rapidly than does the luciferase bound flavin‐4a‐hydroperoxide. This suggests that the endogenous light is not caused by the decomposition of the flavin‐4a‐hydroperoxide.
THE PHOTOCHEMISTRY OF IODO, METHYL AND THIOMETHYL SUBSTITUTED ARYL AZIDES IN TOLUENE SOLUTION AND FROZEN POLYCRYSTALS
Authors: Leyva Elisa , Chang David H. S. , Platz Matthew S. , Watt David S. , Crocker Peter J. , Kawada Kenji
Published: January 2008

The photolysis of para‐methyl and para‐thiomethylphenylazide at 77 K produces the corresponding triplet nitrenes which can be detected by electron paramagnetic resonance (EPR) spectroscopy. Photolysis of these azides in frozen toluene at 77 K leads to insertion of the nitrene into a benzylic C‐H bond of the matrix in modest yields. Photolysis of iodinated aryl azides under these conditions does not produce triplet nitrenes that can be detected by EPR spectroscopy. In contrast to the para‐methyl and para‐thiomethyl substituted phenyl nitrenes, photo‐induced cgupling of iodo‐substituted phenyl nitrenes to toluene proceeds in very poor yield.
WAVELENGTH DEPENDENT FORMATION OF THYMINE DIMERS AND (6‐4)PHOTOPRODUCTS IN DNA BY MONOCHROMATIC ULTRAVIOLET LIGHT RANGING FROM 150 TO 365 nm
Authors: Matsunaga Tsukasa , Hieda Kotaro , Nikaido Osamu
Published: January 2008

Abstract—We investigated the wavelength dependence of cyclobutane thymine dimer and (6‐4)photo‐product induction by monochromatic UV in the region extending from 150 to 365 nm, using an enzyme‐linked immunosorbent assay with two monoclonal antibodies. Calf thymus DNA solution was irradiated with254–365 nm monochromatic UV from a spectrograph, or with220–300 nm monochromatic UV from synchrotron radiation. Thymine dimers and (6‐4)photoproducts were fluence‐dependently induced by every UV wavelength tested so far. We also examined the induction of both types of DNA damage by UV below 220 nm extending to 150 nm under dry condition. We detected the efficient formation of both types of damage in the shorter UV region, as well as at 260 nm, which had been believed to be the most efficient wavelength for the formation of UV lesions. The action spectra for the induction of thymine dimers and (6‐4)photoproducts were similar from 180 to 300 nm, whereas the action spectrum values for thymine dimer induction were about 9‐ and 1.4‐fold or more higher than the values for (6‐4)photoproduct induction below 160 nm and above 313 nm, respectively.
SPECTRAL MEASUREMENTS OF GLOBAL AND DIFFUSE SOLAR ULTRAVIOLET‐B RADIANT EXPOSURE AND OZONE VARIATIONS
Authors: Blumthaler M. , Ambach W.
Published: January 2008

Since 1985, spectral solar UV‐B radiant exposure has been measured at the High Alpine Research Station Jungfraujoch, Bernese Alps, Switzerland (3576 m). Global (sun and sky) and diffuse (sky) UV‐B radiant exposure on a horizontal plane are measured simultaneously by two identical devices. The detecting system consists of a rotating filter wheel with 8 interference‐filters, centered at every 5 nm between 290 and 325 nm, and a halfbandwidth of ±3 nm. The special advantage of this detector is its waterproofness, allowing operation under all weather conditions. The ratio of the intensities at 305 and 315 nm is being analyzed with regard to ozone variations; for example, the ratio is reduced by a factor of 2 because of an increase in ozone content from 250 to 350 Dobson units. The relation between ozone variations and measured spectral UV‐B intensity is confirmed applying Green's radiation model.
SOLUBILIZATION OF PHOTOSYNTHETIC PIGMENT‐PROTEIN COMPLEXES
Authors: Allgood Leonard , Curtright Robert D. , Markwell John
Published: January 2008

Studies utilizing fractionation of photosynthetic pigment‐protein complexes from the chloroplast thylakoid membrane often employ dodecylsulfate at a concentration of 10 mg mL−1 to disrupt membrane structure prior to electrophoretic fractionation of the complexes. We investigated the effect of varying dodecylsulfate concentration on the solution/air interfacial surface tension in the absence and presence of the same concentrations of thylakoid membranes used by four different fractionation systems that have been commonly employed to fractionate photosynthetic pigment‐protein complexes. Concentrations of dodecylsulfate in the range5–10 mg mL−1, normally utilized to treat thylakoids prior to fractionation, were effective in reducing the interfacial surface tension to levels equivalent to control solutions without added thylakoid membranes. However, thylakoid membranes treated with these concentrations of dodecylsulfate are not resolved into discrete pigment‐protein complexes when subjected to electrophoresis on an agarose gel, and do not produce significant amounts of pigment‐containing complexes with a molecular size < 100 000 as measured by filtration with size‐exclusion membranes. We conclude that many surfactant systems empirically developed to fractionate photosynthetic pigment‐protein complexes may not fully solubilize the complexes prior to the electrophoretic step.
ARTIFACTS IN FLUORESCENCE EMISSION SPECTROSCOPY RELATED TO WOOD'S ANOMALY
Authors: Kessel David
Published: January 2008

Fluorescence emission spectra of porphyrins acquired with a monochromator using a 1500 line/mm holographic grating were affected by polarization‐induced effects (Wood's anomaly) which affected the transmission of different wavelengths of light. This effect resulted in a blue‐shift in the emission optimum, and distortions in the fluorescence spectrum at longer wavelengths. These anomalies could be eliminated by insertion of polarizers, orientation = 0°, in emission and excitation paths. A monochromator with a 1200 line/mm holographic grating was essentially free from these distortions.
LIGHT SCATTERING SPECTROPHOTOMETRY FROM ISOLATED CONTROL AND TRIAZOLE‐TREATED CHLOROPLASTS
Authors: Deshpande S. , Hofstra G. , Fletcher R. A. , Abrahamson E. W.
Published: January 2008

Light scattering relaxation spectrophotometry has proven to be a useful technique to monitor rapid cytophysical changes in chloroplast suspensions brought about by flash illumination. This paper compares the Mg‐ATP dependent light scattering behaviour of cholorplasts isolated from control and triazole‐treated wheat seedlings. Our results suggest that triazole‐treatment enhances Mg‐ATP dependent activity. This same enhancement in control chloroplasts can be brought about by introducing potassium ion in the presence of valinomycin. Therefore, the potassium ion might account for part of the stress resistance conferred by triazole treatment.
PHOTOINDUCED ELECTRON TRANSFER QUENCHING OF EXCITED Ru(II) POLYPYRIDYLS BOUND TO DNA: THE ROLE OF THE NUCLEIC ACID DOUBLE HELIX
Authors: Orellana Guillermo , Mesmaeker Andree Kirsch‐De , Barton Jacqueline K. , Turro Nicholas J.
Published: January 2008

In the presence of double helical polynucleotides (sodium poly(dA‐dT)‐poly(dA‐dT) or calf thymus DNA), the efficiency of oxidative or reductive electron transfer between photoexcited ruthenium(II) chelates Ru(tap)2(hat)2+ or Ru(phen)⅔+ (where tap =1,4,5,8‐tetraazaphenanthrene, hat = 1,4,5,8,9,12‐hexaazatriphenylene, and phen = 1,10‐phenanthroline) and appropriate cationic quenchers (ethidium, Ru(NH3)3/6+, methyl viologen, or M(phen)3/3+, where M = Co, Rh, Cr) increases1–2 orders of magnitude compared to the efficiency of the same quenching in microhomogeneous aqueous medium (kq= 0.3‐1.8 × 109 M's−1). The enhancement is more pronounced when the binding constant of the quencher (103 < Kh < 106M−1) is large. Similar trends are found when the biopolymers are replaced by sodium poly(styrenesulfonate) (PSS). The accelerated electron transfer process is proposed to be due mainly to the effect of accumulation of the reagents in the electrostatic field of the polymer; if corrections for this effect are introduced (e.g. ratioing [quencher]/[polynucleotide]), the reaction rate becomes essentially independent of the polymer concentration. Based upon a model for electron transfer reaction of the complexes within a small cylindrical interface around the DNA helix, calculations of the bimolecular electron transfer rate constants are computed to be 10′ times smaller when the reactants are bound to the double‐stranded polynucleotides and decreased mobility of the cationic species is apparent. The effect is less pronounced if a simpler polyelectrolyte (PSS) is employed. Emission lifetimes of the Ru(II) polypyridyls bound to the DNA (0.32–2μs, double exponential decays) are discussed as well.
ASYMMETRIC INDUCTION IN THE SOLID STATE PHOTOCHEMISTRY OF AMMONIUM SALTS*
Authors: Gudmundsdottir Anna D. , Scheffer John R.
Published: January 2008

A general approach to using crystal chirality in asymmetric synthesis is described. An example consists of the preparation of crystalline salts of dimethyl 9‐amino‐9,10‐ethenoanthracene‐11, 12‐dicarboxylate (1) with optically active sulfonic acids. Photolysis of the salts in the solid state generates a product that has chiral centers in the amine‐containing portion of the molecule (di‐π‐methane photorearrangement). The optical activity in the photoproduct was determined by polarimetry and NMR chiral shift reagent analysis, which revealed enantiomeric excesses ranging from 30 to 68% depending on the optically active sulfonic acid employed. In contrast to the results in the crystalline state, irradiation of the salts in acetonitrile gave racemic photoproduct.
MONOALKYL α‐OXOAMIDES: PHOTOCHEMISTRY IN HOMOGENEOUS and IN MICROHETEROGENEOUS MEDIA*
Authors: Richard Wanda G. , Chesta Carlos A. , Whitten David G.
Published: January 2008

An investigation of the photoreactivity of the amphiphilic α‐oxoamide, N‐(12‐dodecanoic acid)benzoylformamide, (1), in aqueous (pH 10) solution and its inclusion complexes with β‐cyclodextrin (β‐CD) and carboxymethylamylose (CMA). In all three media photolysis of 1 yields predominantly the fragmentation products from hydrolysis, mandelamide and the corresponding aldehyde. The most reasonable mechanism for the reaction is an intramolecular quenching of a ketone‐localized excited state by electron transfer from the amide nitrogen followed by proton transfer and a second electron transfer (zwitterion‐1 → diradical ⇄ zwitterion‐2) to yield ultimately the mandelamide‐imine precursor which hydrolyzes to the observed products. The quantum yields for 1 decomposition and mandelamide appearance in aqueous solution (pH 10) are 0.21 and 0.16, respectively. Compound 1 forms a 1:1 and 1:2 complex with β‐CD and shows enhanced quantum efficiencies for reaction, especially the 1:2 complex. 1 also forms a complex with CMA which shows a similar binding constant to other similar chain length amphiphiles in other studies. Here again reactivity is enhanced for the photoreaction of 1 upon complexation, indicating that neither the electron transfer quenching of the excited states nor reaction of subsequent intermediates is prohibited in the complexes. Mechanistic implications of these results are discussed.
PHOTOPHYSICS OF DIOXORHENIUM(V) IN NAFION*
Authors: Thorp H. Holden , Gray Harry B.
Published: January 2008

The emission properties of [ReO2(py)4]+ in Nafion perfluorosulfonated membranes have been investigated. The excited state of [ReO2(py)4]+is a sensitive probe of microheterogeneous environments in aqueous solution (Thorp el al. (1989) J. Am. Chem. SOC. 111,4364–4368). The absorption and emission maxima indicate that the interior of the membrane is quite polar, similar to ethylene glycol (Z‐85). Two well‐resolved emission components show different lifetimes (τ1(H2O) = 250 ns, τ2,(H20) = 1.3 μs) and isotope effects (3.0, 2.4), indicative of varying degrees of solvent accessibility. The evidence suggests that [ReO2(py)4]+ occupies two distinct regions in the polymer film, assigned as the interfacial region and the ion‐cluster region based on previous electrochemical studies involving other metal ions.
HYDRATED ELECTRON FORMATION ON LASER EXCITATION OF P‐PYRIDOXYL AMINO ACIDS and PROTEINS
Authors: T.Greenaway Frederick , Redmond Robert W. , Ledbetter John W.
Published: January 2008

Evidence from a characteristic transient spectrum, its lifetime and quenching by N2O demonstrates that XeCl excimer laser excitation of the reduced form of pyridoxal 5′‐phosphate bound to lysine residues will produce the hydrated electron. The phenoxyltype radical coproduct was also observed. The results identify a useful label of protein structures for site‐specific electron generation which can occur outside the region of light absorption by aromatic residues of protein. The results also represent the first observation of hydrated electron formation from flash excitation of a vitamin B6 cofactor.
THE EFFECTS OF PLASMA LIPOPROTEINS ON in vitro TUMOR CELL KILLING and in vivo TUMOR PHOTOSENSITIZATION WITH BENZOPORPHYRIN DERIVATIVE
Authors: Allison B. A. , Waterfield E. , Richter A. M. , Levy J. G.
Published: January 2008

The influence of lipoprotein association on in vitro tumor cell killing and in vivo tumor photosensitization with benzoporphyrin derivative (BPD) has been investigated in M‐1 tumor bearing mice. The association of benzoporphyrin mono acid ring A with either low or high density lipoprotein increased tumor cell killing in an in vivolin vitro cytotoxicity assay performed 3 h post intravenous drug administration. Eight hours following photosensitizer injection only low density lipoprotein (LDL) mixtures produced significant (P≤ 0.005) increases in tumor cell killing compared to BPD in unfractionated plasma. The efficacy of in vivo photosensitization in the presence of lipoproteins correlated with the in vivolin vitro cytotoxicity. Association of BPD with low or high density lipoproteins resulted in delayed tumor regrowth and higher cure rates when light exposure (125J/cm2) was performed 3 h post drug administration. When light exposure was performed 8 h post‐injection only LDL‐BPD mixtures led to enhanced tumor eradication compared to BPD administered in aqueous solution or unfractionated plasma.
SUBCELLULAR LOCALIZATION OF PORPHYRINS USING CONFOCAL LASER SCANNING MICROSCOPY
Authors: WOODBURN K. W. , Vardaxis N. J. , Hill J. S. , Kaye A. H. , Phillips D. R.
Published: January 2008

The in vitro subcellular distribution patterns of 10 porphyrins, varying in hydrophobicity and charge, were studied using confocal laser scanning microscopy on two cell lines (V79 and C6 glioma cells) for incubation times up to 24 h. All of the porphyrins were taken up rapidly by both cell lines and distinct classes of subcellular distribution patterns were observed: general cytoplasmic staining; localization in lysosomes (usually associated with general cytoplasmic staining); localization in mitochondria (and general cytoplasmic staining); localization in mitochondria with subsequent uptake into lysosomes. Structure‐localization relationships which have emerged are that porphyrins with dominantly cationic side chains localize in mitochondria, whereas those with a more anionic character tend to localize in lysosomes.
EFFECTS OF CHRONIC EXPOSURE ULTRAVIOLET‐A INCLUDING 2% ULTRAVIOLET‐B ON FREE RADICAL REDUCTION SYSTEMS IN HAIRLESS MICE
Authors: Maeda Kazuhisa , Naganuma Masako , Fukuda Minoru
Published: January 2008

Chronic ultraviolet (UV) irradiation is known to cause a variety of changes in the skin, including wrinkles, pigmented spots and carcinogenesis. To explore time dependent changes in several parameters with chronic UV irradiation, we examined the molecular changes in connective tissue, intracellular defence enzymes and free radical antioxidant substances in hairless mice skin caused by chronic exposure to UV‐A including 2% UV‐B. Connective tissue changes were estimated using hydroxyproline and isodesmosine assays as a measure of collagen and elastin concentrations, respectively.

After 6 weeks irradiation, the insoluble collagen and elastin were both substantially elevated, as were the activities of glutathione peroxidase (GSH‐Px) and superoxide dismutase (SOD). Continued UV irradiation resulted in a steady decline in SOD and lipid soluble antioxidants, while the GSH‐Px remained elevated, suggesting that SOD and lipid soluble antioxidants in the skin may be involved in protecting it from UV damage and deteriorate with chronic irradiation.
RELATIVE INDUCTION OF CYCLOBUTANE DIMERS and CYTOSINE PHOTOHYDRATES IN DNA IRRADIATED in vitro and in vivo WITH ULTRAVIOLET‐C and ULTRAVIOLET‐B LIGHT
Authors: Mitchell David L. , Jen Jin , Cleaver James E.
Published: January 2008

SV40 DNA was irradiated in vitro and in vivo with UV‐C (240–280nm) and UV‐B (280–320nm) light, and damaged sites sensitive to digestion with Escherichia coli endonuclease III (endo III) and bacteriophage T4 endonuclease V (endo V) were quantified. The frequency of endo Ill‐sensitive sites (primarily cytosine photohydrates) induced was1–2% of the frequency of endo V‐sensitive sites (cyclobutane dimers) in both purified SV40 DNA and intracellular episomal SV40 DNA. Endo III‐ and endo V‐sensitive sites in DNA were induced in the same relative proportion at both UV‐C and UV‐B wavelengths. We found no evidence to support earlier inferences that intracellular conditions enhance the formation of cytosine photohydrates or other monobasic forms of DNA damage.
ENHANCEMENT OF ULTRAVIOLET‐DNA REPAIR IN den V GENE TRANSFECTANTS and T4 ENDONUCLEASE V‐LIPOSOME RECIPIENTS
Authors: Kibitel Jeannie Tsimis , Yee Vivian , Yarosh Daniel B.
Published: January 2008

The phage T4 deri V gene, coding for the pyrimidine‐dimer specific T4 endonuclease V, was transfected into human repair‐proficient fibroblasts, repair‐deficient xeroderma pigmentosum fibroblasts, and into wild type CHO hamster cells. Transfectants maintained den V DNA and expressed deri V raRNA. Purified T4 endonuclease V encapsulated in liposomes was also used to treat repair‐proficient and ‐deficient human cells. The den V transfected clones and liposome‐treated cells showed increased unscheduled DNA synthesis and enhanced removal of pyrimidine dimers compared to controls. Both den V gene transfection and endonuclease V liposome treatment enhanced post‐UV survival in xeroderma pigmentosum cells but had no effect on survival in repair‐proficient human or hamster cells. The results demonstrate that an exogenous DNA repair enzyme can correct the DNA repair defect in xeroderma pigmentosum cells and enhance DNA repair in normal cells.
EFFECTS OF ULTRAVIOLET LASER RADIATION ON VENEZUELAN EQUINE ENCEPHALOMYELITIS VIRUS*
Authors: Nikogosyan David N. , Kapituletz Sergei P. , Smirnov Yuri A.
Published: January 2008

The effects of usual low‐intensity continuous (Λ= 254 nm,I= 10 W/m2) UV radiation and high‐intensity laser nanosecond (Λ= 266 nm, ‐τp= 10 ns,I= 109W/m2) or picosecond (Λ= 266 nm, τP= 23 ps,I= 1012W/m2) UV radiation on Venezuelan equine encephalomyelitis virus (a member of the Togaviridae family) were compared. The quantum yields of infectivity inactivation, pyrimidine dimer formation and RNA‐protein crosslinking were determined.
PROTON TRANSLOCATION and CONFORMATIONAL CHANGES DURING THE BACTERIORHODOPSIN PHOTOCYCLE: TIME‐RESOLVED STUDIES WITH MEMBRANE‐BOUND OPTICAL PROBES and X‐RAY DIFFRACTION*
Authors: Dencher Norbert A. , Heberle Joachim , Bark Carola , Koch Mlchel H. J. , Rapp Gert , Oesterhelt Dieter , Bartels Klaus , Büldt Georg
Published: January 2008

Abstract– For the first time, we monitored time‐resolved conformational changes inherent in bacterio‐rhodopsin's reaction cycle as well as the H+‐release events directly at the surface of bacteriorhodopsin (bR) at room temperature. Signals of optical pH‐indicators in the aqueous bulk phase were compared with those of probes covalently linked to bR. The kinetics of H+‐translocation and the correlation of the photocycle with the pumping cycle can only be determined with indicators bound to bR. The proton appears at the extracellular surface during the L550 to M412 transition. Upon short photo‐excitation, diffraction patterns were obtained from both guanidine hydrochloride‐treated wild type bR and an Asp96Asn mutant with millisecond time resolution by x‐ray synchrotron radiation. The measured time course and location of the structural changes confirm and extend our previous static neutron diffraction study at ‐180°C. The temporal correlation of photocycle intermediates and proton translocation steps with structural changes in the protein under similar environmental conditions strongly contribute to the understanding of the pumping mechanism.
KINETIC ANALYSIS OF TIME‐RESOLVED INFRARED DIFFERENCE SPECTRA OF THE L and M INTERMEDIATES OF BACTERIORHODOPSIN*
Authors: Chen Wei‐Ge , Braiman Mark S.
Published: January 2008

Abstract– Infrared difference spectra with 4 cm−1 spectral resolution and 10‐u.s temporal resolution, obtained previously with a stroboscopic Fourier‐transform difference technique (Braiman et al., 1991, Proc. Natl. Acad. Sci. USA 88, 2388), were analyzed by means of a global exponential fitting procedure based on singular value decomposition. Using a simple linear kinetic model K → L → M for the bacteriorhodopsin (bR) photocycle in the time range10–1000 μ.s at 16.5°C, it was possible to generate bR → L and bR → M difference spectra with signal/noise ratios comparable to those obtainable with low temperature difference spectroscopy. The resulting time‐resolved bR → L and bR‐→ M difference spectra are both very similar to the corresponding static FTIR difference spectra obtained at 175 K and 250 K, respectively. In the bR → L spectrum, however, there are interesting differences that may indicate a greater degree of deprotonation of Asp‐96 when L is formed at physiological temperatures than when it is observed in a low‐temperature steady state.
RING OXIDIZED RETINALS FORM UNUSUAL BACTERIORHODOPSIN ANALOGUE PIGMENTS*
Authors: Beischel C. J. , Mani V. , Govindjee R. , Ebrey T. G. , Knapp D. R. , Crouch R. K.
Published: January 2008

Abstract– Three ring oxidized retinal analogues have been isolated from the exhaustive oxidation of all‐trans retinal. All‐trans 4‐oxoretinal and 2,3‐dehydro‐4‐oxoretinal have similar absorption maxima to that of all‐trans retinal and have been shown to be in the 6‐s‐cw conformation in solution. Pigments formed with bacterioopsin exhibit absorption maxima (520 nm) blue‐shifted from that of bacteriorhodopsin (bR), indicating a disturbance of the external point charge by the electronegative carbonyl moiety at the 4 position. The third analogue contains a ring contracted to a cyclopentenyl‐α, β‐dione. Unlike the majority of retinals, this analogue displays a 6‐s‐trans conformation in solution and has a red‐shifted absorption maximum at 435 nm. The resulting bR analogue pigment (515 nm) is formed five times faster than the other oxoretinal pigments. All three oxoretinal pigments show an irreversible 20 nm blue shift upon exposure to white light. The 4‐oxo and 2,3‐dehydro‐4‐oxoretinal pigments, after irradiation, undergo a small reversible blue shift (4–8nm) on dark adaptation. These two pigments pump protons, although with slowed photocycle kinetics, demonstrating that these structural changes (addition of the carbonyl at the C‐4 and insertion of a double bond in the ring) do not block the function of the pigment. Extraction of the C‐15 tritiated analogue retinals from illuminated and non‐illuminated pigments of all three oxoretinals yield identical results. Therefore, any crosslinking of these oxoretinals to the protein is by linkages which are unstable to the extraction procedures.
PURPLE FISSION YEAST: OVEREXPRESSION and PROCESSING OF THE PIGMENT BACTERIORHODOPSIN IN Schizosaccharomyces pombe*
Authors: Hildebrandt Volker , Polakowski Frank , Büldt Georg
Published: January 2008

Abstract– The purple pigment bacteriorhodopsin (BR) acts as a light‐driven proton pump in the cytoplasmic membrane of the archaebacterium Halobacterium halobium. The original gene encoding for the precursor of bacterio‐opsin (bop‐gene) and a shortened gene, where the first nucleotides encoding for the presequence are deleted, were introduced in yeast expression vectors. Northern blot analysis of transformed Schizosaccharomyces pombe cells revealed the strong transcription of the archaebacterial DNA directed by the constitutive alcohol dehydrogenase promoter of the fission yeast. The translated precursor and the second construction without the presequence were accumulated in the plasma membrane fraction of the eukaryote. Yeast cells containing the mature BR showed a weaker color than those harboring the precursor protein, if the cells were grown in minimal medium with 2% glucose. At higher glucose concentrations (7%) the expression of BR increased with and without presequence. The overexpressed precursor leads to coryneform fission yeast, whereas cells transformed with the vector containing the bop‐gene without the presequence, producing the mature protein, retained the rod‐shaped form.
ALL‐trans‐RETINAL IS THE CHROMOPHORE BOUND TO THE PHOTORECEPTOR OF THE ALGA: Chlamydomonas reinhardtii*
Authors: Derguini Fadila , Mazur Paul , Nakanishi Koji , Starace Dorine M. , Saranak Jureepan , Foster Kenneth W.
Published: January 2008

Abstract– Rhodopsin is the general name for a family of visual pigments that receive light and transmit this signal to the rest of an organism. Chlamydomonas reinhardtii is a unicellular eukaryote whose light‐tracking system consists of a single eye. Through spectral studies of Chlamydomonas' reaction to light of different wavelengths (action spectroscopy), it has been shown in vivo that the photoreceptor of Chlamydomonas is functionally similar to vertebrate rhodopsin. We seek to characterize the photoreceptor further by identifying the molecule that is incorporated into the rhodopsin of Chlamydomonas forming the chromophore. High performance liquid chromatography analysis of organic extracts of retinaloximes from membrane fractions enriched in eye‐spots and in cells virtually free of interfering carotenoids identified syn‐all‐trans as the existing retinaloxime isomer. We conclude that all‐trans‐retinal is the native molecule that is available to be incorporated into the rhodopsin of Chlamydomonas and therefore forms the functioning chromophore on binding.
AUSTRALIAN Halobacteria and THEIR RETINAL‐PROTEIN ION PUMPS*
Authors: Mukohata Yasuo , Ihara Kunio , Uegaki Koichi , Mlyashita Yukiya , Sugiyama Yasuo
Published: January 2008

Abstract– Halophiles collected in Western Australia have been found to be examples of extremely halophilic rod‐shaped archaebacteria, members of the genus Halobacterium. Most of them contain retinal proteins, and these proteins differ from one another and also from both bacteriorhodopsin (bR) and halorhodopsin [and sensory rhodopsins (sR)] isolated from Halobacterium salinarium (halobium), as revealed by their peptide maps and amino acid sequences. However, these retinal proteins still have the ability to pump protons or chloride ions in the light. These new ion pumps, designated archaerhodopsins (aR) [Mukohata et al. (1988) Biochem. Biophys. Res. Commun.151,1339–1345], are almost identical in terms of their molecular sizes and transient photochemical properties to the ion pumps identified previously. Differences are found in the: (1) apparent extinction coefficient of dark/light‐adapted aR‐2; (2) titration profiles at acidic pH of the absorption spectra of all aRs; and (3) circular dichroism spectra, which are influenced by the coexistent isoprenoid bacterioruberin. The amino acid sequences of two proton pumps from the Australian halobacteria, namely aR and aR‐2, are approximately 90% homologous and both sequences are about 60% homologous with that of bR. Hydropathy plots suggest that these pumps also have a seven‐helical structure similar to that of bR. The amino acid residues are highly conserved in the helical regions, in particular in the case of helices C and G (91 and 84%, respectively), among the three proton pumps.
RELATIONSHIP BETWEEN LIGHT QUALITY DEPENDENCE AND IRRADIANCE ADAPTATION OF PHOTOSYNTHESIS IN Acetabularia mediterranea*
Authors: SCHMID RAINER
Published: January 2008

Abstract—

Characteristic differences in the light intensity curves of photosynthesis after growth of cells of Acetabularia mediterranea Lamour. (A. acetabulum (L.) Silva) in weak and strong white light were similar to those for red and blue light‐treated cells, respectively. This indicated that responses to white light quantity and those to light quality might be causally related. Small differences in the thylakoid polypeptide composition of cells grown in high and low intensities of white light were not significant and thus did not help to clarify whether the adaptations to blue or red light, respectively, were the same.

When the red to blue‐light ratio was varied, keeping the total photon fluence rate constant, the photosynthetic capacity (red light saturated O2‐production) was dependent on blue light irradiance in a logarithmic fashion. The specific influence of red light was not detectable, indicating that only blue light was effective for light irradiance adaptation in Acetabularia.

The situation was different, at least for a transient period, when adaptation to light irradiance was allowed to proceed from a low photosynthetic activity after preirradiation of the cells with prolonged red light. The effect of low white light irradiances was pronounced, causing a maximum increase of photosynthetic activity within 3 days. The response to blue light was enhanced as well, and a very low photon irradiance added to continuous red light caused a change of the same order as that produced by high irradiances of blue light alone. This elevated action of low intensity white and blue light is most likely due to increased metabolite supply derived from the degradation of starch enhanced by this light quality. Therefore, photosynthetic effectiveness in Acetabularia is regulated by the irradiance of blue light and by feedback via photosynthetic products.
ELECTRONIC STATES OF THE INDOLE‐ACRYLAMIDE MOLECULAR PAIR
Authors: ILICH PREDRAG , PRENDERGAST FRANKLYN G.
Published: January 2008

Abstract—

A model is suggested for tryptophan fluorescence quenching by acrylamide based on the prediction that acrylamide can absorb a photon from the excited indole moiety and then dissipate the optical energy into a sink of fast exchanging conformations. Semiempirical electronic structure calculations of the indole‐acrylamide pair indicate little actual intermolecular orbital mixing a1 van der Waals contact distances. However, the two lowest singlet transitions of the molecular pair, assigned to the acrylamide {π*}←n(O) line and to the indole 1Lb←1A1 line, respectively, vary significantly in energies and in transition and excited state moments with the geometry of interaction between the two entities. The distribution of optimal quenching coordinations depends separately on the benzene and pyrrole portions and has a distinctly non‐spherical shape at these distances.
FLUORESCENCE ENERGY TRANSFER BETWEEN DIMETHYLDIAZAPEROPYRENIUM DICATION AND ETHIDIUM INTERCALATED IN POLY d(A‐T)
Authors: MERGNY JEAN‐LOUIS , SLAMA‐SCHWOK ANNY , MONTENAY‐GARESTIER THÉRÈSE , ROUGÉE MICHEL , HÉLÈNE CLAUDE
Published: January 2008

Abstract—

Dimethyldiazaperopyrenium is one of the largest known DNA intercalators. Fluorescence energy transfer occurred between dimethyldiazaperopyrenium (donor) and ethidium (acceptor) when these dyes were bound to a double‐stranded polynucleotide such as poly d(A‐T). The addition of increasing amounts of ethidium bromide led to a marked shortening of the fluorescence lifetime of the donor, whereas the excited state of the acceptor was progressively populated via energy transfer from the donor. Critical Förster distance between these two chromophores was calculated to be 3.8 nm. The observed transfer efficiency was lower than that calculated on the basis of this critical distance and a statistical distribution of bound drugs. These results are discussed taking into account the conformational change induced by intercalation of dimethyldiazaperopyrenium in the double‐stranded polynucleotide.
ENHANCEMENT OF PHOTOREPAIR OF ULTRAVIOLET‐DAMAGE BY PREILLUMINATION WITH FLUORESCENT LIGHT IN CULTURED FISH CELLS
Authors: YASUHIRA SHINJI , MITANI HIROSHI , SHIMA AKIHIRO
Published: January 2008

Abstract— Fluorescent light (FL) illumination of RBCF‐1 cells, derived from a goldfish, prior to 254 nm UV‐irradiation enhanced their ability to photorepair. The cells were illuminated with FL for 1 h (29 W/m2) and incubated for 8 h in the dark before being irradiated with 10 J/m2 UV. The surviving fraction of FL‐treated cells after UV‐irradiation rose about 7‐fold (from 3 to 20%) by 20 min photorepair treatment with the same FL source, whereas 4‐fold (from 1.6 to 6%) in the FL nontreated cells. Flow cytometric analysis showed that FL treatment did not affect the distribution of cell cycle phase at the time of UV‐irradiation (8 h after FL treatment). Pyrimidine dimers induced by UV were measured by the use of UV endonuclease of Micrococcus luteus and alkaline agarose gel electrophoresis. Initial yields of dimers after exposure to 10 J/m2 UV were almost the same (about 0.11 dimer/kb) between FL treated and non‐treated cells. But after 20 min photorepair treatment, about 70% of dimers were removed in the FL treated samples, while less than 20% were removed in the non FL‐treated ones.
AN ACTION SPECTRUM FOR ULTRAVIOLET INDUCED ELASTOSIS IN HAIRLESS MICE: QUANTIFICATION OF ELASTOSIS BY IMAGE ANALYSIS
Authors: KLIGMAN LORRAINE H. , SAYRE ROBERT M.
Published: January 2008

Abstract— To determine an action spectrum for ultaviolet (UV)‐induced elastosis, four groups of 24 albino hairless mice each were exposed to four different spectra emitted by a xenon are solar simulator fitted with cut‐off filters (Schott WG 320, 335, 345, and 360). These filters progressively removed more of the shorter wavelengths until, in the final spectrum, only long wavelength UVA (> 335 nm) remained. Exposures continued up to 62 weeks. A fifth group of mice served as controls. Skin biopsies were taken at pre‐determined dose points and were processed for light microscopy. Elastosis was quantified by computerized image analysis, yielding dose‐response curves for each spectrum. The total energy required for a 50% increase in elastic tissue compared to controls was determined graphically for each spectrum. These were: WG 320, 65 J/cm2; WG 335, 865 J/cm2; WG 345, 1230 J/cm2; and WG 360, 2000 J/cm2. Our results were tested against published action spectra for erythema, photocarcinogenesis and elastosis. The erythema spectrum was the most predictive for elastosis except that the longer UVA wavelengths were less effective for elastosis than for erythema. Solar simulating radiation (WG 320 filter) with its UVB component was the most effective in inducing elastosis. Full spectrum UVA (WG 345) required 20 times more energy while long wavelength UVA (WG 360) required 30 times more energy to induce equivalent elastosis.
PHOTOTOXICITY INVOLVING THE OCULAR LENS: in vivo AND in vitro STUDIES
Authors: LERMAN SIDNEY , MANDAL KRIS , MISRA BIJAY , SCHECHTER ANDREW , SCHENCK JOHN
Published: January 2008

Abstract— Our laboratory has demonstrated the cataractogenic potential of UV radiation and several photosensitizing drugs in laboratory animals and in humans. We have utilized lens fluorescence measurements (which we have demonstrated to be a reliable marker for pre‐cataractous and early cataractous changes), NMR pulse relaxation techniques, and our recently developed magnetic resonance imaging method to measure lens T2 values in the normal and UV exposed Degus lens (in vivo and in vitro) to detect pre‐cataractous changes in the lens. These approaches will permit us to employ two parameters (increased non‐tryptophan fluorescence and a decrease in T2 values) to monitor for such changes months before the lens opacities become manifest by conventional slit lamp examinations.
MODULATION BY THIOLS OF THE MEROCYANINE 540‐SENSITIZED PHOTOLYSIS OF LEUKEMIA CELLS, RED CELLS, AND Herpes simplex VIRUS TYPE 1
Authors: GAFFNEY DAVID K. , O'BRIEN JILL M. , SIEBER FRITZ
Published: January 2008

Abstract— This paper reports on the role of endogenous and exogenous thiols in the merocyanine 540 (MC 540)‐sensitized photoirradiation of L1210 leukemia cells, human erythrocytes, and human Herpes simplex virus type 1. Several measures taken to decrease the intracellular content of glutathione enhanced the cells sensitivity to MC 540‐sensitized photoirradiation while stimulation of glutathione biosynthesis or supplementation of the extracellular or extraviral thiol content decreased the photosensitivity of cells and viruses. Taken together, these data suggest that endogenous and exogenous thiols can modulate the sensitivity of cells and enveloped viruses to MC 540‐sensitized photoirradiation. They also pose new questions as to the mechanism of MC 540‐sensitized photolysis.
LOW TEMPERATURE FTIR STUDIES OF THE PROTONATION OF A RETINYLIDENE SCHIFF BASE
Authors: LAROUCHE D. , GÉLINAS A. , LE‐THANH H. , SANDORFY C. , VOCELLE D.
Published: January 2008

Abstract— This note supplements the paper by Badilescu et al. (1989) [Photochem. Photobiol.49, 313‐318]. Low temperature solution spectra of 1: 2 and 2: 1 mixtures of trans‐retinylidene‐tertbutylamine and propanoic acid are presented. The results show that the degree of protonation is both temperature and concentration dependent.
PHOTOCHEMICAL AND SPECTRAL PROPERTIES OF A PARTICULATE MODEL SYSTEM OF CHLOROPHYLL WITH AMPHIPHILES PREPARED FROM HISTAMINE
Authors: SEELY G. R. , REHMS ADEN A.
Published: January 2008

Abstract— In the photosynthesis model system described, chlorophyll a at an interface photosensitizes the transfer of hydrogen equivalents from a hydrocarbon phase to an aqueous phase. The hydrocarbon phase, to which chlorophyll is adsorbed, consists of polyethylene particles swollen with tetradecane. The particles are also charged positive by co‐adsorption of dodecylpyridinium iodide. Furthermore, chlorophyll is ligated with the imidazole function of one of several amphiphiles derived from histamine, which may or may not contain a reducible nitroaromatic group that can serve as primary electron acceptor from photoexcited chlorophyll. The fluorescence quantum yield of chlorophyll on these particles is diminished by self‐association of the pigment and by reaction with an oxidizing amphiphile; in the latter case, the quantum yield is correlated with the one‐electron redox potential of the amphiphile. Fluorescence‐lifetime analysis reveals that most excited singlet states of chlorophyll are quenched rather quickly, and that most of the fluorescence comes from a small fraction of chlorophyll with long lifetime. All preparations sensitize the photoreduction of 5,5′‐dithiobis(2‐nitrobenzoate) (DTNB) to the water‐soluble thiolate by hydrazobenzene. When the amphiphile that ligates chlorophyll is not oxidizing, the quantum yield of photoreduction is unrelated to the fluorescence yield of the particles, but may be related to the degree of self‐association of chlorophyll. When the amphiphile that ligates chlorophyll is oxidizing, the kinetics of photoreduction of DTNB require that the electron passes through the primary oxidant to DTNB. Quantum yields for photosensitized reducton of oxidizing amphiphiles in the absence of DTNB have a reversed correlation with redox potential, which can be rationalized in terms of the Marcus theory of electron transfer. All data are most consistently accounted for if the primary photoproduct is an ion pair of chlorophyll and primary oxidant when the latter is available, and a chlorophyll radical ion pair when it is not, both formed by electron transfer from the singlet excited state of chlorophyll.
ENHANCED GROWTH AND EXPERIMENTAL METASTASIS OF CHEMICALLY INDUCED TUMOR IN ULTRAVIOLET IRRADIATED SYNGENEIC MICE
Authors: GENSLER HELEN L. , CHEN HWUDAURW
Published: January 2008

Abstract— Recent studies have shown that ultraviolet (UV) irradiation induces a systemic effect which enhances subsequent tumor induction by benzo[a]pyrene in a manner which is dependent on the dose of benzo[a]pyrene. The present study was designed to test whether UV‐B irradiation renders mice susceptible to subcutaneous or intravenous injection of a regressor tumor induced by benzo[a]pyrene. The sources of UV‐B irradiation were banks of 6 Westinghouse FS‐40 sunlamps, situated 20 cm above the mouse cages. Female BALB/cAnNHsd received five 30‐min dorsal UV‐B radiation treatments per week for 12 weeks, resulting in a total dose of approx. 6.4 × 105 J m‐2. Two to seven days after termination of UV treatments, syngeneic regressor tumor cells (BP2) induced by benzo[a]pyrene were injected subcutaneously or intravenously into irradiated mice and unirradiated controls. By 38 days post subcutaneous implantation, 24/30 and 3/30 BP2 implants were detectable in the irradiated and unirradiated mice, respectively. Ultraviolet irradiated mice were also unable to reject lung colonies resulting from intravenous administration of BP2 cells, although they were rejected by unirradiated mice. The mean number of lung colonies per mouse was 16‐ to 35‐fold greater in UV irradiated mice than in unirradiated controls, at 14 to 17 days post injection. Thus, UV irradiation rendered mice, with no known exposure to benzo[a]pyrene, susceptible to a subcutaneous or intravenous injection of a regressor tumor induced by benzo[a]pyrene.
ATMOSPHERIC SUN PROTECTION FACTOR ON CLEAR DAYS: ITS OBSERVED DEPENDENCE ON SOLAR ZENITH ANGLE AND ITS RELEVANCE TO THE SHADOW RULE FOR SUN PROTECTION
Authors: Holloway Leith
Published: January 2008

Abstract—

Global irradiances measured in seven 5‐nm bands of UV‐B at Rockville, MD (39.1°N, 77.1oW) on 28 clear days near the summer solstice are convoluted with the erythemal action spectrum of human skin to determine dose rates at various hours of the day. These rates are averaged with respect to solar zenith angle to obtain the diurnal variation of mean dose rate and of the Sun Protection Factor (SPF) of the atmosphere (reciprocal of the normalized atmospheric transmissivity) on a typical clear summer day in Rockville. At a 45o zenith angle the atmospheric SPF is computed to be 2.7 and increases rapidly to greater than 7 at 60o.

Dose rates are integrated with respect to time to obtain estimates of mean doses for various periods during clear days at Rockville in mid summer and near the autumnal equinox. In mid summer the effective erythemal UV‐B exposure during the period when the solar zenith angle is less than 45o is about five times greater than that during the remainder of the day. These observations provide scientific basis for a shadow rule for solar UV‐B protection: when shadows are shorter than objects casting them, sunburn is much more likely than at other times.
TUMORICIDAL CAPACITIES OF MACROPHAGES PHOTODYNAMICALLY ACTIVATED WITH HEMATOPORPHYRIN DERIVATIVE
Authors: Yamamoto Nobuto , Hoober J. Kenneth , Yamamoto Nobuyukr , Yamamoto Shinji
Published: January 2008

Abstract—

Four days after administration to mice of small amounts (30–600ng/mouse) of hematoporphyrin derivative (HPD), peritoneal macrophages exhibited a greatly enhanced Fc‐receptor mediated phagocytic capacity as assayed by ingestion activity of IgG‐coated sheep erythrocytes. Much higher doses (>3000 ng/mouse) did not have this effect. The peritoneal macrophages activated by administration of HPD have tumoricidal capacity for IgG‐coated retinoblastoma cells. We then studied in vitro photodynamic activation of macrophages by white and red fluorescent light irradiation of mouse peritoneal cells (mixture of macrophages and B and T lymphocytes) in media containing very low concentrations of HPD. A short (5 s) white fluorescent light exposure (lWm‐2) of peritoneal cells in a medium containing 0.03 ng HPD/mL produced the maximal level of ingestion activity of macrophages. A 15 s red fluorescent light exposure (lWm‐Z) of peritoneal cells in a medium containing 0.1 ng HPD/mL produced the maximal level of ingestion activity of macrophages. Thus, photodynamic activation of macrophages with white fluorescent light is more efficient than that with red fluorescent light. This can be explained by the fact that HPD has a large absorption peak at about 364 nm which extends into the visible range, and decreasingly smaller absorption bands at 500, 535, 570 and 630 nm. In vitro photodynamically activated macrophages showed efficient tumoricidal activity regardless of the type (white or red) of light used. These results suggest that a low level of HPD promotes therapeutic immunopotentiation