bluuebunny/crossref_metadata_2025_split huggingface dataset:
STEREOELECTRONIC PROPERTIES OF PHOTOSYNTHETIC AND RELATED SYSTEMS—VIII. AB INITIO QUANTUM MECHANICAL CHARACTERIZATION OF THE ELECTRONIC STRUCTURE AND SPECTRUM OF THE BACTERIOPHEOPHORBIDE a ANION RADICAL
Authors: Petke J. D. , Maggiora Gerald M. , Shipman Lester L. , Christoffersen Ralph E. 
Published: January 2008

Abstract— Ab initio configuration interaction wavefunctions and energies are reported for 16 doublet states of the anion radical of ethyl bacteriopheophorbide a (Et‐BPheo a‐˙), and are employed in an analysis of the electronic absorption spectrum.The lowest excited doublet state D1 is predicted to lie 8601 cm‐1 above the ground state D0; the D1← D0 transition is nearly forbidden, with a computed oscillator strength f= 0.002. The visible absorption spectrum is shown to consist of transitions to three 2(π, π*) states, D2, D3, and D4. The D4← D0 transition (y‐polarized, f= 0.91) appears to account for observed intense absorption at 15 800 cm‐1.The Soret band of Et‐BPheo a‐˙ is shown to consist of transitions to several 2(π,π*) states, D7‐D15. Transitions of particularly high intensity include D7← D0 (y‐polarized, f= 0.72), D10← D0 (y‐polarized, f= 1.1), D12← D0 (xy‐polarized, f= 0.86) and D15← D0 (y‐polarized, f= 0.83).Spin density data and plots are used to describe and compare the general features of the unpaired spin distributions in D0 and D1, which are in reasonable agreement with other reported calculated values and available experimental data for D0.
OPTICAL‐MICROWAVE DOUBLE RESONANCE SPECTROSCOPY OF IN VIVO CHLOROPHYLL
Authors: Clarke Richard H. , Jagannathan Surya P. , Leenstra Willem R. 
Published: January 2008

Abstract—At low temperatures, chloroplast and subchloroplast preparations exhibit complex fluorescence spectra. Emission bands can be attributed to photosystem (PS) particles and various antenna‐chl proteins as well as solubilized chls. Initial results from a systematic study of the components of these fluorescence spectra via optical‐microwave double resonance spectroscopy are presently reported. Conclusions regarding possible structural features are discussed. Experiments on triplet sublevel decay rates yielded data consistent with an interpretation of triplet energy transfer within antenna fragments.
FLASH‐INDUCED FAST CHANGE IN SURFACE POTENTIAL AND FLUIDITY OF PURPLE MEMBRANE STUDIED BY SPIN LABEL METHOD
Authors: Tokutomi Satoru , Iwasa Tatsuo , Yoshizawa Tǒru , Ohnishi Shun‐ichi 
Published: January 2008

Abstract— Flash‐induced changes in surface potential and fluidity of purple membrane were studied by a spin label method. Changes in surface potential and fluidity were monitored by observing the distribution of charged and uncharged spin labels between the purple membrane and the aqueous phase.On flash illumination, a transient hyperpolarization of the surface potential and a transient fluidization of the membrane hydrophobic region are induced. The former may probably reflect the proton movement near the purple membrane surface, while the latter may result from photo‐induced conformational changes of bacteriorhodopsin.The two events are different in time course. The relationships between the two events, and the formation and decay of the intermediates of bacteriorhodopsin in the photoreaction cycle are discussed.
ANALYSIS OF PRIMARY PHOTOCHEMICAL PROCESSES IN BACTERIORHODOPSIN
Authors: Dinur U. , Honig B. , Ottolenghi M. 
Published: January 2008

Abstract— The sequence of primary events following light absorption by light adapted bacteriorhodopsin (bR570) is considered by analyzing recent picosecond absorption and emission data. The analysis is facilitated by theoretical calculations which allow us to characterize the properties of the first excited singlet state. It is concluded that excitation leads to the eventual population of a photochemically important nonfluorescent excited state (I) which decays into a photoproduct (J625)‐ In J625, which is most probably a ground state molecule, the chromophore has undergone a structural change, presumably trans→ 13‐cis isomerization. It is suggested that the subsequent processreflects a relaxation of the protein environment involving proton transfer.
LIGHT‐INDUCED PROTON DISSOCIATION AND ASSOCIATION IN BACTERIORHODOPSIN
Authors: Takeuchi Yasuaki , Ohno Koki , Yoshida Masasuke , Nagano Kei 
Published: January 2008

Abstract— Light‐induced proton release and uptake by acetylated and unmodified bacteriorhodopsin were measured. Bacteriorhodopsin, when illuminated, shows a net proton release at neutral and alkaline pH's, but in acidic pH, it shows an uptake of protons. In the presence of high concentrations of guanidine hydrochloride, light caused only proton release even in acidic pH and the maximum extent of the release was one proton per bacteriorhodopsin molecule around pH 8.Acetylation of bacteriorhodopsin caused no alteration in the absorption spectrum of purple complex (bR570) and M412‐intermediate, but decreased the decay rate of the M412‐intermediate. Light‐induced release of protons was not observed even in neutral pH values, and only the proton uptake was noticed by acetylated purple membrane fragments. In high concentrations of guanidine hydrochloride, no proton uptake or release by illumination was observed. Vesicles were reconstituted from acetylated purple membrane. These vesicles had almost no ability for light‐induced proton transport. The role of amino group(s) in light‐induced proton release and transport through the purple membrane is discussed.
P588, A SECOND RETINAL‐CONTAINING PIGMENT IN HALOBACTERIUM HALOBIUM
Authors: Weber H. J. , Bogomolni R. A. 
Published: January 2008

Abstract— Halobacterium mutant strains with defects in the biosynthesis of various pigments have been isolated. One of these strains, mutant ET‐15, is incapable of producing the light‐driven proton pump bacteriorhodopsin and the carotenoid bacterioruberin. However, ET‐15 synthesizes another photochemically active, retinal‐containing pigment, P588, which mediates light‐induced proton uptake enhanced by uncouplers. P588 and bacteriorhodopsin are simultaneously present in wild‐type cells grown under normal conditions; however, they can be distinguished by the following criteria.

They can be separated by independent mutational events.
Proton ionophores such as FCCP diminish bacteriorhodopsin‐driven proton translocation but enhance P588‐mediated proton flows. We define here proton translocations which can be diminished by the addition of uncouplers (e.g. FCCP) as ‘active’, others which can be enhanced by FCCP as ‘passive’.
The kinetic and spectral properties of the photocycle intermediates of bacteriorhodopsin and P588 are different.
The action spectrum for photocycling of P588 is red‐shifted with respect to that for bacteriorhodopsin.

A comparison of action spectra for proton translocations with that for photocycling links pigment P588 and light‐driven, passive proton uptake by ET‐15 envelope vesicles. When chemically bleached P588 was regenerated with all‐trans‐retinal, both photochemical activity and light‐induced proton inflow were restored to equal extents. This identifies P588 with the energizer for the passive proton flows.
PHOTOSENSITIZATION BY DRUGS IN SURFACTANT SOLUTIONS
Authors: Moore Douglas E. , Burt Christopher D. 
Published: January 2008

Abstract— Chlorpromazine, promazine, anthracene and furosemide were tested as photosensitizers using 365 nm UV light in micellar solutions of cationic, anionic and nonionic surfactants. In all cases, micelles enhanced the ability of these compounds to photosensitize the oxidation of 2,5‐dimethylfuran and the free radical polymerization of acrylamide. pH variation showed that the base form of chlorpromazine and the acid form of furosemide are the principal photosensitizing forms of these compounds. Rate differences between cationic and anionic surfactant media indicate the cation radical to be the major photochemical species formed from chlorpromazine and promazine in micellar media. Photodechlorination of chlorpromazine accounted for a significantly higher reactivity of chlorpromazine over promazine. Anthracene was found to be a very active photosensitizer by the singlet oxygen mechanism but also yielded a small concentration of cation radicals in micellar solution. In its neutral form, furosemide reacted strongly in both photooxidation and photopolymerization systems.The implications of this study to drug‐induced photosensitivity are that (i) free radical reactions may play a major role, and (ii) these sensitizers are more reactive in a hydrophobic environment, suggesting that the cellular membrane or the hydrophobic surfaces of proteins or DNA are more important sites of action in photosensitivity.
EFFECTS OF GLYCEROL UPON THE BIOLOGICAL ACTIONS OF NEAR‐ULTRAVIOLET LIGHT: SPECTRA AND CONCENTRATION DEPENDENCE FOR TRANSFORMING DNA AND FOR ESCHERICHIA COLI B/r
Authors: Peak J. G. , Peak M. J. , Foote C. S. 
Published: January 2008

AbstractThe concentration dependence for the protection of isolated transforming DNA and Escherichia coli by glycerol against 365‐nm monochromatic near‐ultraviolet light (UV) was measured. Glycerol protection saturates at a concentration of about 0.1 M for DNA and 1.0 M for E. coli. Action spectra for glycerol protection of transforming DNA (tryptophan and histidine markers) are similar to those obtained previously for diazobicyclo[2.2.2.˜octane (DABCO) protection, with protection reaching a maximum near 350‐nm UV and decreasing rapidly at wavelengths above and below 350 nm. However, glycerol protects against near‐UV about twice as efficiently as DABCO. The action spectrum for protection of E. coli by glycerol against the lethal effects of near‐UV was not the same as the spectrum for DNA since glycerol sensitized the cells, but not the DNA, at wavelengths longer than about 380 nm. A possible role of hydroxyl or other radicals was supported by the observation that benzoate also protected DNA against inactivation by 334‐nm UV.
TOXICITY, DNA DAMAGE AND INHIBITION OF DNA REPAIR SYNTHESIS IN HUMAN MELANOMA CELLS BY CONCENTRATED SUNLIGHT
Authors: Parsons P. G. , Musk P. 
Published: January 2008

AbstractA 1 m diameter water lens was used to focus solar radiation, giving an 8‐fold concentration of the total spectrum and a cytocidal flux similar to that of laboratory UV sources. Survival curves for human melanoma cells were similar for sunlight and 254 nm UV, in that Dq, was usually larger than Do. An xeroderma pigmentosum lymphoblastoid line was equally sensitive to both agents and human cell lines sensitive to ionizing radiation (lymphoblastoid lines), crosslinking agents or monofunctional alkylating agents (melanoma lines) had the same 254 nm UV and solar survival responses as appropriate control lines. Two melanoma sublines derived separately by 16 cycles of treatment with sunlight or 254 nm UV were crossresistant to both agents. In one melanoma cell line used for further studies, DNA strand breaks and DNA‐protein crosslinking were induced in melanoma cells by sunlight but pyrimidine dimers (paper chromatography) and DNA interstrand crosslinking (alkaline elution) could not be detected. The solar fiuence response of DNA repair synthesis was much less than that from equitoxic 254 nm UV, reaching a maximum near the Do value and then declining; semiconservative DNA synthesis on the other hand remained high. These effects were not due to changes in thymidine pool sizes. Solar exposure did not have a major effect on 254 nm UV‐induced repair synthesis.
TRIPLET STATES OF CAROTENOIDS BOUND TO REACTION CENTERS OF PHOTOSYNTHETIC BACTERIA: TIME‐RESOLVED RESONANCE RAMAN SPECTROSCOPY
Authors: Lutz Marc , Chinsky Laurent , Turpin Pierre‐Yves 
Published: January 2008

AbstractTime‐resolved, low‐temperature resonance Raman spectra of triplet states of the carotenoids specifically present in bacterial reaction centers in a strained cis conformation have been obtained, thus demonstrating the possibility of studying intermediate transient states of these structures using resonance Raman spectroscopy. Resonance Raman spectra of triplet cis spheroidene and cis methoxyneurosporene present in reaction centers of Rhodopseudomonas spheroides, (strains 2.4.1. and Ga, respectively) exhibit marked differences with those of triplet, all‐trans carotenoids previously studied in vitro. These differences, together with the frequency shifts measured for the v1 modes, indicate that triplet carotenoids bound to reaction centers retain a cis conformation, and that probably no isomerization occurs to all‐trans carotenoids upon T ← S0 excitation. Pi electron distributions along the polyene backbone are probably less regular in the triplet state than in the singlet ground state, although probably not to the extent suggested by previous theoretical calculations. The apparently anomalous behaviour of the v2 bands of all‐trans carotenoids upon T ← S0 excitation is shown to result largely from the actual complexity of this region of the Raman spectra, together with a weak participation of the vc—–c internal coordinate in the corresponding modes. Finally, the Raman scattering efficiency of triplet spheroidene bound to reaction centers is lower than that of the singlet, ground state form, under equivalent excitation conditions.
PHOTOBIOLOGICAL ACTIVITY OF MARMESIN (5‐B‐HYDROXYISOPROPYL‐4–5 DIHYDROFUROCOUMARIN) IN CHINESE HAMSTER V79 CELLS
Authors: Uwaifo Anthony O. , Heidelberger Charles 
Published: January 2008

Abstract— Marmesin was isolated from the medicinal plant, Afraegle paniculata. Its cytotoxicity and mutagenicity in Chinese hamster V79 cells when sensitized to near ultraviolet (NUV) and long wavelength ultraviolet light or black light (BL) were assayed.Marmesin was extremely cytotoxic in the dark. This cytotoxicity was photoenhanced in NUV and BL; the photoenhanced lethality being higher in NUV than in BL. The LD50 of marmesin under NUV and BL photosensitization were 0.002 μM and (0.012 μM), respectively. In the absence of NUV and BL, marmesin's LD50 was 0.013 μM. NUV and BL without marmesin were not significantly cytotoxic at the fluence rates of 0.29 W/m2 and 4.2 W/m2, respectively, for up to 20 min. In contrast to the observed high cytotoxicity of marmesin, its mutagenicity at the HGPRT locus (AzGr) was weak. The implication of this result in the high incidence of skin cancer in Nigeria in which A. paniculata is used as a medicinal plant is discussed.
STREAK CAMERA MEASUREMENT OF TRYPTOPHAN AND RHODAMINE MOTIONS WITH PICOSECOND TIME RESOLUTION
Authors: Nordlund T. M. , Podolski D. A. 
Published: January 2008

Abstract—We have used a signal averaging laser (30 ps pulse)‐streak camera system to measure fluorescence anisotropy decays of dyes in solution and protein tryptophan chromophores with picosecond time resolution. Emission polarization as a function of time can be measured directly and simultaneously for both polarization directions and stored in an optical multichannel analyzer. The corrected anisotropy is computed after background subtraction. Rotations of free dyes in solution (Sulforhodamine 101, tryptophan) and the temperature‐dependent internal motions of human serum albumin (tryptophan emission) are displayed.
PHOTOPHARMACOLOGY OF THE TRANQUILIZER CHLORDIAZEPOXIDE IN RELATION TO ITS PHOTOTOXICITY
Authors: Bakri† A. , Henegouwen G. M. J. Beijersbergen van , Chanal J. L. 
Published: January 2008

Abstract— This study demonstrates that photobiological effects by exogenous molecules are not per se restricted to the skin. As an example the photopharmacology of chlordiazepoxide (e.g. LibriumR) was studied. Rats being exposed to UV‐A after administration of 14C2 labeled chlordiazepoxide (CDZ) showed a marked change in the pattern of urinary metabolites; the quantity of metabolites without N4‐oxide function increased, whereas that of compounds with N4‐oxide function decreased. Covalent binding to organ tissue of especially liver and skin of the irradiated rats was found. This would mean that in the irradiated rats oxaziridines which may also react with tissue of the inner organs are formed from CDZ and its N4‐oxymetabolites.Further, the combination of light and CDZ leads to a 30% decrease in weight of the liver, indicating liver damage. This is also supported by the percentage of conjugated urinary metabolites being 1.5–2.5 times lower than in the non‐irradiated CDZ‐treated rats, possibly caused by a decrease of enzymatic activity.The administration of CDZ‐oxaziridine to non‐irradiated rats provoked the same effects, such as a decrease of the weight of the liver comparable to that of irradiated CDZ‐treated rats. On the other hand the combination of light and treatment with N4‐desoxy CDZ did not have any effect, as expected.
RIBOFLAVIN‐PHOTOSENSITIZED OXIDATIVE DEGRADATION OF A VARIETY OF LIGNIN MODEL COMPOUNDS
Authors: Kutsuki Hidetoshi , Enoki Akio , Gold Michael H. 
Published: January 2008

AbstractOxidation of several lignin model compounds with alkylated paraphenolic groups by photosensitizing riboflavin (RF). rose bengal (RB) and methylene blue (MB) was examined. Photosensitizing RF cleaved l–(3‘‐4’‐diethoxyphenyl)‐1.3 dihydroxy‐2‐(4‐methoxyphenyl)propane (I). 4‐ethoxy‐3‐methoxyphenylglycerol‐(3‐guaiacyl ether (II) and l‐(4‘‐ethoxy‐3’‐methoxyphenyI)‐1,3 dihydroxypropane (IV) at their respective Cα‐Cβ bonds. Riboflavin also oxidized 3.4‐diethoxy‐benzaldehyde (VI) to the corresponding acid, and hydroxylated the conjugated olefin l‐(4‘‐ethoxy‐3’‐methoxyphenyl)1.2 propene (III) to yield the initial product IV. In contrast, MB and RB hydroxylated III but had no effect on I, II, IV or VI under identical conditions. This suggested RF effected transformations via a hydrogen radical abstraction (Type I) rather than a 1O2 mediated reaction.To confirm this, the effects of deuterium oxide (D:0) and oxygen pressure on the photosensitizing dye reactions were examined. The effect of D20 on tryptophan (Trp) oxidation and hydroxylation of III by MB and RB was significant, indicating involvement of 1O2. D2O had no significant effect on cleavage of the diarylpropane (I) and the olefin (III) by RF, indicating these reactions did not proceed by a Type II mechanism. While O2 pressure effect on Trp oxidation by MB was insignificant, it had a large negative effect on cleavage of I by RF. These results, coupled with the relatively slow oxidation rate of Trp by RF. indicate that photosensitizing RF produces 1O2 inefficiently and is not effecting oxidation of these lignin model compounds via a Type II mechanism.
USE OF THE DYE HOECHST 33258 TO INCREASE THE PHOTOSENSITIVITY OF BROMODEOXYURIDINE‐CONTAINING CELLULAR SLIME MOLDS
Authors: Graetzer R. , Deering R. A. 
Published: January 2008

AbstractThe photosensitivity of amoebae of Dictyostelium discoideum to near‐ultraviolet light (near‐UV; 365 nm peak) was investigated following growth in 5‐bromodeoxyuridine (BrdUrd) and treatment with the dye Hoeschst 33258. Cell killing was studied as a function of dye‐treatment time and concentration, and BrdUrd incorporation time and concentration. For example, cells grown for 13 h in 50 μg BrdUrd/ml and then treated for 1 h in 10 μg dye/ml were reduced to 10% survival by a near‐UV exposure of 0.8 min. Combinations of any two of the three factors (BrdUrd, dye, near‐UV) were ineffective for killing. The sensitivity of the cells to near‐UV decreased rapidly as the holding time between the end of the dye treatment and the start of the UV exposure was increased.
PHOTOMOVEMENT RESPONSES OF THE HETEROTRICHOUS CILIATE Blepharisma Japonicum
Authors: Kraml Manfred , Marwan Wolfgang 
Published: January 2008

AbstractLight‐induced movement responses of the heterotrichous ciliate Blepharisma japonicum were studied by physiological experiments. Two photosensory responses could be identified. A step‐up photophobic response is observed as a very rapid backward movement. Microbeam irradiations of individual cells showed that only the anterior part of the ciliate is able to perceive the light stimulus that mediates the phobic reaction. The action spectrum peaks at approximately 400 nm, which indicates that a blue light receptor is involved.Positive photokinesis of Blepharisma could be shown as a forward movement that is accelerated by increasing the applied photon fluence rate. The steady state level of the velocity depends highly on wavelength and photon fluence rate of the actinic light. After specific inhibition of the phobic reaction bv 1 m/W NH4+, photokinesis can be induced by microbeam irradiation at any part of the cell.We isolated two main pigments by thin layer chromatography and characterized them as hypericin‐like compounds: a red pigment that is obviously responsible for the red color of the ciliates (= blepharismin). and a yellow one with maximal absorption near 420 nm. The possible photoreceptor functions of these pigments are discussed.We could not find in Blepharisma a distinct phototactic behavior which is so typical for the related ciliate Stentor.
ASSOCIATION OF CHLOROPHYLL WITH AMIDES ON PLASTICIZED POLYETHYLENE PARTICLES–III. UNUSUAL SPECTRA OF CHLOROPHYLL a WITH N‐METHYLMYRISTAMIDE*
Authors: Kusumoto Y. , Senthilathipan V. , Seely G.R. 
Published: January 2008

Abstract—The absorption spectrum of chlorophyll a, adsorbed with the amphiphilic amide, N‐methylmyristamide. to particles of polyethylene swollen with tetradecane, is unusual in that the red band apparently consists of three main components, which by Gaussian deconvolution are located at 664.5, 678 and 687 nm. The last is very narrow, with a band width of only 5‐6 nm at half maximum. At low amide concentration, the 744 nm band of chlorophyll hydrate is also observed. Room temperature fluorescence is weak, and indistinctly resolved into bands. However, on gradual cooling to 80 K, the fluorescence intensifies greatly and becomes resolvable into at least eight bands. The circular dichroism spectrum of the red band region shows optical rotatory strength in two narrow bands at 677 and 686 nm which is enormous, compared to that of monomeric chlorophyll or even the 744 nm hydrate. It is suggested that cyclic oligomer structures, in which adjacent chlorophylls are linked through the amide group of N‐methylmyristamide, might be responsible for the spectral phenomena. Unsubstituted myristamide and N.N‐dimethylmyristamide do not produce these narrow‐banded phenomena with chlorophyll at all.
THE PHOTOLYSIS OF PENICILLAMINE DISULPHIDE IN ACIDIC AQUEOUS SOLUTION
Authors: Grant D. W. , Stewart J. H. 
Published: January 2008

AbstractQuantum yields of penicillamine (PenSH), valine (PenH), β‐hydroxyvalinc (PenOH), penicillamine trisulphide (PenSSSPen). ammonia, a keto acid and penicillamine sulphinic acid (PenSO2H) were determined in the 254 nm‐photolysis of aqueous solutions of penicillamine disulphide (PenSSPen) at pH 1.8. Oxygenation of the PenSSPen solutions prior to irradiation had no effect on the yield of PenSH, but increased the yields of PenOH, ammonia, keto acid and oxyacids of sulphur and decreased the yields of PenSSSPen and PenH. Evidence was obtained that deamination of PenSSPen is initiated by Pen. radicals in deoxygenated and PenO2 radicals in oxygenated solutions. Flash photolysis was used to detect the PenSS. radical in irradiated PenSSPen solutions and to study its rate of decay. Comparison of the results of the investigation with those published for cystine indicate that substitution of the methylene hydrogens in cystine by methyl groups leads to a substantial increase in the importance of photochemical C‐S bond fission.