bluuebunny/crossref_metadata_2025 huggingface dataset:
FLUORESCENCE PROBE FOR MICROENVIRONMENTS: A NEW PROBE FOR MICELLE SOLVENT PARAMETERS AND PREMICELLAR AGGREGATES
Authors: Law K. Y.
Published: January 2008

Abstract— A previous study on the electronic spectroscopy of p‐N,N‐dialkylaminobenzylidenemalononitrile, 1, has been extended to a larger variety of organic solvents and to micelles of ionic and nonionic surfactants. By comparing the fluorescence emission (λF and φ∫) of 1 in micelles and in homogeneous organic solvents, the effective polarity and the microviscosity of the micellar environments of potassium dodecanoate, sodium dodecyl sulfate, cetyltrimethylammonium bromide and Triton X‐100 micelles have been determined to be 40, 40, 36 and 28, respectively and 23, 31, 34 and 28 cP, respectively. These results indicate that the fluorescence probe is located in the micelle–water interface of a micelle and this region of a micelle is polar and viscous. 1 has also been studied in different surfactants with varying surfactant concentrations. The φ∫ of 1, a microviscosity gauge for micellar aggregates, remains unchanged at the critical micelle concentrations of various surfactants, but decreases at much lower surfactant concentrations. This is attributable to the formation of premicellar aggregates of surfactant molecules below their critical micelle concentrations.
TIN CHLORIN‐ISOBACTERIOCHLORIN: EVIDENCE FOR A REVERSIBLE PHOTOREDOX PROCESS
Authors: Debaig‐Valade C. , Bagno O. , Pommier J. C. , Joussot‐Dubien J.
Published: January 2008

Abstract— It is shown that the photoreduction of tin tetraphenylporphyrin using a variety of reducing agents does not stop at the tetraphenylchlorin stage but proceeds to the isobacteriochlorin derivative. However, this latter compound can be photooxidized in the presence of oxygen to yield exclusively tin chlorin which in turn can again be photoreduced to the isobacteriochlorin. The process appears to be photoreversible at this stage. These reactions have been studied in homogeneous and micellar solutions.
LASER‐UV‐MICROIRRADIATION OF CHINESE HAMSTER CELLS: THE INFLUENCE OF THE DISTRIBUTION OF PHOTOLESIONS ON UNSCHEDULED DNA SYNTHESIS
Authors: Cremer C. , Cremer T. , Jabbur G.
Published: January 2008

Abstract— Fibroblastoid Chinese hamster cells synchronized by mitotic selection were microirradiated in G1, using a low power laser‐UV‐microbeam (λ= 257 nm). The incident energy was either concentrated on a small part of the nucleus (mode 1) or distributed over the whole nucleus (mode 11). Using the same incident UV energy, the local UV fluences were estimated to differ by two orders of magnitude. Following microirradiation the cells were incubated with [3H]‐thymidine for 2 h and thereafter processed for autoradiography. Silver grains were concentrated over the microirradiated part after mode 1 and distributed over the whole nucleus after mode 11 irradiation. To quantify the amount of unscheduled DNA synthesis, the number of grains per nucleus was determined. It increased with the total incident energy, but was not or only slightly affected by the mode of microirradiation, if appropriate autoradiographic conditions were used. The findings suggest that within the investigated range of energy densities (2.7–1000 J/m2), the total amount of unscheduled DNA synthesis depends on the total number of pyrimidine dimers but not on their distribution in nuclear DNA.
PROTECTION BY DABCO AGAINST INACTIVATION OF TRANSFORMING DNA BY NEAR‐ULTRAVIOLET LIGHT: ACTION SPECTRA AND IMPLICATIONS FOR INVOLVEMENT OF SINGLET OXYGEN
Authors: Peak J. G. , Foote C. S. , PEAK M. J.
Published: January 2008

Abstract— Diazobicyclo (2.2.2) octane (DABCO) protects the genetic activity of purified transforming Bacillus subtilis DNA against inactivation by near‐, but not far‐, UV light. The maximum dose‐modifying factor is 0.4, at 0.1 M DABCO. Maximal protection is at about 350 nm and no protection occurs below 313 nm. The spectrum for protection is similar to that described for 2‐aminoethylisothiouronium bromide hydrobromide. The relevance of these observations with regard to the role of singlet oxygen in near‐UV effects is discussed.
WAVELENGTH EFFECTS ON THE PHOTOPROCESSES OF INDOLE AND DERIVATIVES IN SOLUTION
Authors: Zechner J. , Köhler G. , Getoff N. , Tatischeff I. , Klein R.
Published: January 2008

Abstract— The two main primary photoprocesses (electron ejection and H‐atom release) for indole, 5‐methoxyindole and N‐methylindole in various polar and nonpolar solvents were studied as a function of the excitation energy and were correlated with the corresponding fluorescence quantum yields. In hydrocarbon solvents, N–H bond cleavage is the main primary photoprocess from the 1Bb band of the substrates with the exception of N‐methylindole. In alcohols, both processes are of negligible importance. Hydrated electrons (e−aq) are ejected from the relaxed singlet states of all three compounds in aqueous solutions with a similar yield for excitation at 280 and 254 nm (1La and 1Lb states). The yield increases when the excitation is into the 1Bb band. The quantum yields of the two primary processes from the higher excited states are generally lower than the fraction of molecules not converting to the fluorescent state. This is explained by an efficient back reaction in competition with a thermally activated radical release from an intermediate state or radical pair formed from the S2 (1Bb) state. The non‐occurrence of a photoionization energy threshold is discussed.
ENERGY TRANSFER FROM SODIUM N‐ALKYL CARBAZOLE SULFONATE TO ZINC TETRAPHENYLPORPHYRIN IN MICELLAR SOLUTIONS
Authors: Ebbesen Thomas Wren , Delgado Olavio , Valla Alain , Giraud Michel , Saito Yoshio , Tachibana Hideki , Wada Akiyoshi
Published: January 2008

Abstract— In order to study energy transfer to zinc tetraphenylporphyrin (ZnTPP) in micellar solution, a series of surface active agents of sodium N‐alkyl carbazole sulfonate, were synthesized. The energy transfer efficiency from the carbazole group near the surface to ZnTPP located in the core of sodium lauryl sulfate (NaLS) micelles was found to be 30%, as observed through the fluorescence of ZnTPP. The critical micelle concentrations (CMC) of the sodium N‐alkyl carbazole sulfonate surfactants, determined by scattering, were 2 times 10‐4 M, 3 times 10‐5M and 3 times 10‐6 M, respectively, for alkyl: octyl, dodecyl and hexadecyl. The sensitivity of the CMC of NaLS to the presence of foreign surfactants and solubilizates was also investigated.
THE EFFECT OF A PERMANENT ELECTRIC FIELD ON THERMOLUMINESCENCE OF CHLOROPLASTS
Authors: Knox Peter P. , Garab Gyozo I.
Published: January 2008

Abstract— The effect of a permanent electric field on the thermoluminescence (TL) of pea chloroplasts was studied. The field was applied to suspensions at lowtemperatures(–15 to ‐40oC) and to dry films of various humidity. A permanent electric field increased TL at low temperatures at the expense of the peaks above OAoC. When the field strength was high, an increase in the quantum yield could be observed. When a field was applied at ‐15OC, the band around +10oC was reduced preferentially, but when a field was applied at – 40AoC, TL bands emitted above OAoC decreased to a similar extent. Analogies between the behaviour of solid suspensions and dry films of various humidity, and the isotope effect with D2O, indicated that the efficiency and mode of action of an electric field on TL depends on the conformational mobility of the microsurroundings of the traps in the membrane.
PHOTOCHROMISM OF 2,6‐DINITRODIPHENYL ETHERS ENHANCED IN THE PRESENCE OF A HOST BIOMOLECULE*
Authors: Cahnmann Hans J. , Matsuura Teruo
Published: January 2008

Abstract— The photochromic behavior of 2,6‐dinitrodiphenyl ethers is described. In the course of a study for the photoaffinity labeling of the binding site for thyroxine on human prealbumin, it was found that the thyroxine analog 3‐[4‐(4‐hydroxy‐3,5‐diiodophenoxy)‐3,5‐dinitrophenyl]propionic acid (1), on irradiation with >350nm light in the presence of prealbumin, gave a pink species (λmax 508 nm). In the absence of prealbumin, no color formation was observed. Irradiation of 3‐[4‐(4‐hydroxyphenoxy‐3,5‐dinitrophenyl]propionic acid (2) and 3‐(4‐phenoxy‐3,5‐dinitrophenyl)propionic acid (3), analogs of 1, in acetonitrile, aqueous bicarbonate, or ethanol gave a colored species (λmax 500–520 nm depending on the solvent) in the absence of a host molecule. In the presence of β‐cyclodextrin, which may be considered a model for a binding site on a protein, photocoloration occurred at a faster rate than in the absence of ß‐cyclodextrin. For both 2 and 3, the colored species underwent thermal back reaction to the starting compound. The activation energy for the thermal back reaction was estimated to be about 40 kj/mol.
RESOLVED FLUORESCENCE EMISSION SPECTRA OF IRON‐FREE CYTOCHROME c
Authors: Angiolillo Paul J. , Leigh J. S. , Vanderkooi Jane M.
Published: January 2008

Abstract The fluorescence emission of iron‐free cytochrome c (0Cyt c) in a glassy matrix was investigated under conditions of very low temperature (4.2 K.) and narrow bandwidth laser excitation. Excitation into the vibronic band, Qx(1,0) resulted in highly resolved emission spectra of linewidth 10‐20 cm−1. Using the model of selective excitation developed by Abram el al. (1975) and McColgan et al. (1978), the emission spectra of vibronic excitation afforded a method to investigate excited state vibrational structure. Furthermore, emission profiles have shown that in 0Cyt c, the site distribution (inhomogeneous broadening) has a width in the order of 200cm−1.
RESEARCH NOTE: PHOTOREACTION OF 4′, 5′‐DIHYDROPSORALEN WITH THYMINE
Authors: Shim Sang Chul , Koh Jong Sung , Shim Hyun Kwan
Published: January 2008

Abstract— The photocycloaddition reaction of 4′,5′‐dihydropsoralen with thymine was carried out in solution and in the frozen state. A major photoadduct was isolated and characterized by elemental analysis and physical methods. The photoadduct was proven to be the 1:1 C4‐cycloaddition product, an analogue of furocoumarin‐DNA biadduct, with the stereochemistry of anti‐head‐to‐head formed through 2+2 addition reaction between the pyrone double bond of 4′, 5′‐dihydropsoralenand 5,6‐double bond of thymine.
MESODIPHENYLHELIANTHRENE—THE MOST REACTIVE SINGLET OXYGEN ACCEPTOR
Authors: Acs A. , Schmidt R. , Brauer H.‐D.
Published: January 2008

Abstract— The self‐sensitized photooxidation of mesodiphenylhelianthrene in various solvents has been investigated. The involvement of 1O2 as the reactive intermediate in the formation of the endoperoxide has been demonstrated by the quenching of the photooxidation by the efficient 1O2‐quencher β‐carotene. The rate constant for the addition of 1O2 to mesodiphenylhelianthrene has been determined to be kR≅ 1010M‐1 s‐1, which is the highest value hitherto known in the literature. The probability factor p, which describes the concentration independent part of the overall quantum yield, has been measured to be p=0.17.
OCCURRENCE OF PHOTOREVERSIBLE ABSORPTION CHANGES IN DISSOCIATED ALLOPHYCOCYANIN AND PHYCOCYANIN
Authors: Murakami Akio , Fujita Yoshihiko
Published: January 2008

Abstract— Photochromic response of allophycocyanin (APC) and phycocyanin (PC) was studied. Phycobiliproteins were isolated from the blue‐green alga Tolypothrix tennis and supplementary from Anabaena cylindrica. The response was found in both APC and PC when they were dissociated into monomer in the presence of propylene glycol at high concentration. APC in propylene glycol solution showed two photoresponses identical with those of “phycochromes”c and d, respectively. PC showed the photoresponse “phycochrome”a type. After re‐association by removal of propylene glycol, photoresponse activities disappeared.

We concluded that (i) some of monomer APC's and PC's became photoreactive when APC and PC were dissociated into monomer thus that (ii) photoresponses of “phycochromes”a, c and d were not attributed to the special pigments independent of APC and PC, but were responsible to special molecules of monomer APC and PC. Spectral patterns of photoresponses were discussed in relation to dissociation‐association of protein.
METHYL VIOLOGEN AGGREGATION
Authors: Ebbesen T. W. , Ohgushi M.
Published: January 2008

Abstract— Methyl viologen (paraquat, l,l'‐dimethyl‐4, 4'‐bipyridinium dichloride) has been observed to start forming aggregates in methanol at 2.5 times 10‐3 M, and in aqueous solutions at about 10‐2 M depending on other experimental parameters. The number of molecules per aggregate is 2–3 for concentrations < 0.1 M.
EFFECT OF CONTINUOUS FAR‐RED PREIRRADIATION ON THE LAG PHASE OF CHLOROPHYLL A ACCUMULATION IN PHARBITIS NIL COTYLEDONS
Authors: Yoshida Kazuichi , Konishi Michio
Published: January 2008

In Pharbitis nil cotyledons, the lag phase of chlorophyll a (Chi a) accumulation which continues for about 2 h after the onset of continuous white light is eliminated by preirradiation with far‐red light (FR) for 24 or 48 h. When the period of FR preirradiation is prolonged to 72 h or more, however, the lag phase is observed again (FR‐induced lag phase) and the rate of Chi a accumulation during the rapid accumulation phase is lowered below the dark control level.

The application of exogenous 5‐aminolevulinate (J‐ALA) completely eliminates the FR‐induced lag phase, but this treatment eliminates the normal lag phase in dark‐grown cotyledons only partially (i.e. Chi a is accumulated but only slowly during the first few h). Application of a 5‐ALA precursor, such as glycin + succinate. 2‐ketoglutarate or glutamate, eliminates neither the FR‐induced lag phase nor the normal lag phase.

A 24‐ or 48‐h FR irradiation seems not only to enable the synthesis of 5‐ALA but also to make the other regulatory factors favourable for Chi accumulation. When the period of FR irradiation is prolonged to 72 h or more, the ability to synthesize 5‐ALA may be lost.
HYPOCALCEMIA ASSOCIATED WITH PHOTOTHERAPY IN NEWBORN RATS: LIGHT SOURCE DEPENDENCE
Authors: Gutcher Gary R. , Odell Gerard B.
Published: January 2008

Littermate pups of the congenitally jaundiced Gunn rat were studied at 4 days of age. Control animals were shaded from irradiation by opaque cardboard while littermates were exposed to daylight, blue, green or pink fluorescent light. Initially no significant differences were demonstrable between irradiated and control animals with reference to body weight, sex distribution, blood hematocrit, or serum bilirubin and serum calcium concentration. In all control groups, serum bilirubin values were unchanged or increased by the end of the study and serum calcium values were also unchanged. In the light‐exposed groups, serum bilirubin values decreased significantly in all except those exposed to pink light. The serum calcium level was decreased significantly only in pups exposed to fluorescent daylight at 5.00 μW/cm2/nm but in none of the other irradiated groups.
PRIOR EXPOSURE OF HUMAN CELLS TO NEAR UV‐RADIATION GIVES A DECREASE IN THE AMOUNT OF THE UNSCHEDULED DNA‐SYNTHESIS INDUCED BY FAR UV‐RADIATION
Authors: Holmberg M.
Published: January 2008

Pretreatment of human cells with near UV radiation (UVA) in fluences exceeding 5 × 104 Jm−2 caused a decrease in the amount of the unscheduled DNA synthesis induced by far UV radiation (UVC). The DNA repair synthesis, as measured by the incorporation of [3H] ‐thymidine, is reduced by nearly a factor of 2 for a UVA radiation exposure of 1.5 × 105 Jm−2. Since solar UVA fluence rate is rather independent of latitude, this figure corresponds to a UVA exposure time of 50‐60 min from noon sunlight in the summer time.
ACTION SPECTRA FOR INACTIVATION OF NORMAL and XERODERMA PIGMENTOSUM HUMAN SKIN FIBROBLASTS BY ULTRAVIOLET RADIATIONS
Authors: Keyse S.M. , Moss S. H. , Davies D. J. G.
Published: January 2008

—Action spectra for UV‐induced lethality as measured by colony forming ability were determined both for a normal human skin fibroblast strain (lBR) and for an excision deficient xeroderma pigmentosum strain (XP4LO) assigned to complementation group A using 7 monochromatic wavelengths in the range 254‐365 nm. The relative sensitivity of the XP strain compared to the normal skin fibroblasts shows a marked decrease at wavelengths longer than 313 nm. changing from a ratio of about 20 at the shorter wavelengths to just greater than 1.0 at the longer wavelengths. The action spectra thus indicate that the influence on cell inactivation of the DNA repair defect associated with XP cells is decreased and almost reaches zero at longer UV wavelengths. This would occur, for example, if the importance of pyrimidine dimers as the lethal lesion decreased with increasing wavelength. In common with other studies both in bacterial and mammalian cells, our results are consistent with pyrimidine dimers induced in DNA being the major lethal lesion in both cell strains over the wavelength range 254‐313 nm. However, it is indicated that different mechanisms of inactivation operate at wavelengths longer than 313 nm.
FREE ENERGY DEPENDENCE OF THE QUENCHING OF CHLOROPHYLL a FLUORESCENCE BY SUBSTITUTED QUINONES*
Authors: Natarajan L. V. , Blankenship R. E.
Published: January 2008

The quenching of chlorophyll a (Chl a) fluorescence hy a series of substituted benzoquinones. naphthoquinones and anthraquinones has been examined employing ethanol and acetonitrile as solvents. All quinones are good quenchers of fluorescence. There is an excellent linear relation between the Stern‐Volmer quenching constants, K, and the polarographic half wave potentials (E12) of the quinones, with more oxidizing quinones being better quenchers. The quenching data are consistent with the excited state half wave potential of −1.31 eV predicted theoretically, demonstrating that the kinetically estimated value of the Chl a excited state reduction potential agrees with that expected on spectroscopic grounds. The results of quenching are not in agreement with the conventional Marcus theory of electron‐transfer reactions, as there is no evidence of quenching constant. Kq. decrease vsΔG0 even for free energy changes nearly twice that expected for the onset of the Marcus inverted region. However, the kinetically estimated Kq values are in good agreement with the ones calculated by using the Rehm and Weller equation for fluorescence quenching by electron transfer. Our experimental results support the electron transfer mechanism of quenching proposed by Seely.
MONOFUNCTIONAL3,4‐and4′,5′‐PHOTOCYCLOADDUCTS BETWEEN 4,5′‐DIMETHYLANGELICIN and THYMINE
Authors: Dall'Acqua F. , Caffieri S. , Vedaldi D. , Guiotto A. , Rodighiero P.
Published: January 2008

By irradiating (365 nm) an aqueous liquid solution of 4,5′‐dimethylangelicin. a monofunctional photosensitizing furocoumarin, in the presence of an excess of thymine, two new compounds, I and II, have been obtained; they do not show fluorescence when observed with Wood's light. The nuclear magnetic resonance data, the marked similarity of UV absorption and fluorescence spectra of these compounds with those of synthetic 3.4‐dihydro‐4,5′‐dimethylangelicin and their capacity to undergo photodissociation (254 nm) yielding the starting thymine and 4,5′‐dimethylangelicin in equimolecular amounts, are consistent with C4‐cycloadducts between the 3,4‐double bond of the furocoumarin and 5,6‐double bond of thymine. Nuclear magnetic resonance data indicate for I and II a head‐to‐head and a head‐to‐tail structure, respectively. When irradiation is carried out in the frozen state, two adducts. III and IV, fluorescent at Wood's light, have been obtained other than the two above‐mentioned compounds I and II. Compounds III and IV have been identified as 4′.5′‐fluorescent adducts between the 4′,5′‐double bond of the furocoumarin and the 5.6‐double bond of thymine; one of them (III) is identical to that formed in the photoreaction between DNA and 4,5′‐dimethylangelicin; for this last compound a cis head‐to‐head structure has been suggested.
PICOSECOND KINETICS and A MODEL FOR THE PRIMARY EVENTS OF BACTERIORHODOPSIN
Authors: Gillbro Tomas , Sundström Villy
Published: January 2008

The picosecond absorption kinetics of light adapted bacteriorhodops in (BR) are reported for water and glycerol‐water suspensions of purple membrane from Halobacieriwn hulobium at different temperatures (77‐300 K) and pH (5‐10). It is shown that a photoproduct of BR, called P‐BR (pseudo‐bacteriorhodopsin). is responsible for the 16 ± 2 ps relaxation lifetime observed under steady state irradiation (i.e. with a train of ps pulses) at room temperature. At 77 K the absorption recovery lifetime is 62 ± 5 ps in good agreement with previous fluorescence lifetime studies. The observed signal is very sensitive to the sample flow rate and at the highest flow rates a fast absorbance increase (≤ 2 ps) is observed at λ > 620 nm. while at 576 nm a similarly fast absorption recovery alter bleaching is observed. These results imply that the reaction BR → K‐BR occurs within 2 ps. In order to explain the simultaneous formation of P‐BR and K‐BR at 77 K. a model for the primary events including a traus‐cis isomerization and a protein relaxation about the chromophore is suggested. The same model can also be used in explaining the simultaneous formation of batho‐ and hypsorhodopsin in some rhodopsins. Finally, a scheme for the last steps in the photocycle of bacteriorhodopsin including protonation, protein relaxation and cis‐trans isomerization is proposed
RECOVERY OF Escherichia coli K‐12 FROM NEAR‐ULTRAVIOLET RADIATION‐INDUCED MEMBRANE DAMAGE
Authors: Kelland L. R. , Moss S. H. , Davies D. J. G.
Published: January 2008

Abstract A wild‐type Escherichia coli K‐12 strain was irradiated with broad‐band near‐ultraviolet radiation (from Black‐Light Blue fluorescent lamps) and after holding at 37°C for various times in a complex recovery medium, was assessed for viability on either complex medium (YENB) or minimal medium containing a high inorganic salt content. A near‐ultraviolet radiation fluence was used which reduced the surviving fraction to approximately 10% when assessing for viability on the complex medium plates. A near‐ultraviolet radiation induced sensitivity to inorganic salt was observed which was largely recoverable by holding treated cells in a complex recovery medium. The majority of the recovery process occurred in the initial 2 h post‐irradiation holding period. No inhibition of the recovery process was produced by adding chloramphenicol (40 μg/ml) or penicillin G (11 units/ml) to the recovery medium, indicating that neither protein synthesis nor cell wall synthesis, respectively, were required for recovery. However, by adding bacitracin, an antibiotic which acts in part by inhibiting membrane synthesis, to the recovery medium, an effect on recovery from salt sensitivity was observed. At the concentrations of bacitracin used (0.6 and 0.2 units/ml), little or no effect was observed on unirradiated cells, but both concentrations decreased the amount of recovery of irradiated cells. These results demonstrate that recovery from near‐ultraviolet radiation‐induced salt sensitivity occurs, it is independent of cell growth and the effect of bacitracin suggests that membrane synthesis may be required for recovery.
HYDROGEN AND OXYGEN PHOTOPRODUCTION BY TITANATE POWDERS
Authors: Magliozzo Richard S. , Krasna Alvin I.
Published: January 2008

Abstract— Uncoated powders of TiO2 or SrTiO3 did not produce H2 or O2 on UV irradiation of aqueous suspensions of the powders. TiO2 powders coated with platinum or rhodium photoproduced H2 on irradiation (effective wavelengths 334 and 366 nm) and the reaction was stimulated by catalytic quantities of methyl viologen. The turnover numbers for H2 production relative to TiO2 were very low suggesting that the powders were not acting catalytically. Hydrogen production was never stoichiometric with respect to TiO2 and the kinetics of H2 production were first order, not zero order as would be expected for catalytic photolysis of water. Oxygen was never detected and it appears that H2 did not arise from water photolysis but rather from oxidation of reduced sites in TiO2. A rhodium‐coated SrTiO3 powder prepared photochemically produced both H2 and O2 on irradiation but the turnover numbers were very low. A Rh‐SrTiO3 powder prepared thermally showed higher turnover numbers for H2 photoproduction and may be acting catalytically. However, little O2 was detected with this powder. When the turnover numbers for the different titanate powders were expressed with respect to the number of surface monolayer hydroxyl groups calculated from the surface area of the powders, some turnover numbers greater than one were obtained.
ABSORPTION POLARIZATION PROPERTIES OF LIGHT‐ADAPTED BACTERIORHODOPSIN IN THE 266–620nm REGION
Authors: Fukumoto Joseph M. , El‐Sayed M. A.
Published: January 2008

Abstract— Using the method of polarized photochemistry, the polarization of the first daughter (K610) in the photocycle of light‐adapted bacteriorhodopsin (bR570) is determined relative to the polarization of the photolysis pulse for different absorption regions of bR570. The results are discussed in terms of recent spectroscopic assignments of bR570, and in the 310–266 nm region, in terms of energy transfer processes between the apoprotein and the retinal.
TIME‐RESOLVED RESONANCE RAMAN SPECTROSCOPY OF THE BACTERIORHODOPSIN PHOTOCYCLE ON THE PICOSECOND AND NANOSECOND TIME SCALES
Authors: Hsieh Chung‐Lu , El‐Sayed M. A. , Nicol Malcolm , Nagumo Mark , Lee Jai‐Hyung
Published: January 2008

Abstract— Resonance Raman spectra of the picosecond bacteriorhodopsin intermediate(s) have been obtained by microbeam, flow and subtraction techniques using a synchronously pumped, cavity‐dumped dye laser. Nanosecond spectra also were measured with this laser by cavity dumping without mode‐locking. The picosecond spectra in the fingerprint region, which is sensitive to the configuration of the retinal chromophore, differ from spectra of the parent bR570 but could be correlated to the spectrum of bRDA550, a “13‐cis” species which has been determined from spectra of bR570 and bRDA560. The picosecond transient and bRDA550 also are similar in the 950–1050 cm‐1“deuteration fingerprint” region when the medium is changed from H2O to D2O. These results suggest that trans—cis isomerization occurs during the 40‐ps pulse duration. The shift relative to the parent bR570 in the ethylenic stretch region suggests that the picosecond and nanosecond transients absorb at wavelengths longer than 570 nm. The C band at 1646 cm‐1 is found to shift or to broaden upon photolysis in the picosecond time scale. This might suggest a change in the electronic structure of the group and its environment on the picosecond time domain.

The nanosecond spectra obtained in this work (with 15‐ns pulses) are similar to the spectra previously observed on the 100‐ns time scale but are slightly different from the picosecond spectrum. These data suggest that more than one transient species appears on the picosecond‐to‐nanosecond time scale. The temporal evolution of Raman bands in the fingerprint as well as the low energy (950–1050 cm‐1) region and its implications are discussed.
CONTROL OF HYPOCOTYL GROWTH IN MUSTARD SEEDLINGS AFTER LIGHT‐DARK TRANSITIONS
Authors: SCHAUFER E. , EBERT C. , SCHWEITZER M.
Published: January 2008

Abstract— Six hours of irradiation with white or far‐red light strongly stimulates the ‘end of day’ inhibition of hypocotyl elongation in dark grown Sinapis alba L. Measurements of both reversion kinetics of the inductive light pulse and ‘null point’ experiments (Hillman, 1965. 1972) indicate that this response is controlled by stable phytochrome. The extent of the reversible response (i. e. length after far‐red light minus length after red light) showed rhythmic oscillations after a 6, 48 and 54 h white light pretreatment. The rhythm is started by the transition from light to dark and neither phase nor amplitude is influenced by the level of P at this transition.
THE TRANSMISSION OF COMBINED NEUTRAL DENSITY FILTERS
Authors: POFF KENNETH L. , BURKART UHLAND , HAUDER DONAT‐P. , VIERSTRA RICHARD D.
Published: January 2008

Abstract— Stacking of neutral density filters to decrease transmission causes various problems, depending on the type of filters used. Combining reflective filters results in a higher total transmission than the product of the individual transmissions suggests. The error increases dramatically with increasing reflection of the filters due to multiple reflection between the filters. Equations are presented which allow the calculation of combinations of reflective filters and those combining both reflection and absorption.
TRIPLET STATES OF ISOMERS OF THE C15‐ALDEHYDE AND THE C18‐KETONE: LOWER HOMOLOGUES OF RETINAL
Authors: BENSASSON R. V. , LAND E. J. , LIU R. S. H. , LO K. K. N. , TRUSCOTT T. G.
Published: January 2008

Abstract— Triplet extinction coefficients, singlettriplet intersystem crossing yields and triplet state kinetic data of all‐trans, 7‐cis, 9‐cis, 7, 9‐dicis isomers of the C15‐aldehyde and the C18‐ketone. lower homologues of retinal, have been determined in hexane using the methods of laser flash photolysis and pulse radiolysis.
AMPHIPHILIC COPOLYMERS AS MEDIA FOR LIGHT‐INDUCED ELECTRON TRANSFER‐II. ELECTROSTATIC EFFECT ON THE BACK ELECTRON TRANSFER
Authors: Itoh Yoshihiro , Morishima Yotaro , Nozakura Shun‐ichi
Published: January 2008

Abstract— Photosensitized reduction of zwitterionic viologen (SPV) and methyl viologen (MV2+) was investigated using an amphiliphilic copolymer having phenanthryl and sulfonate groups (APh) as photosensitizer in aqueous solutions. In the presence of triethanolamine the accumulation of SPV * (photoproduct) was found to be faster than that of MV+. This attributed to the electrostatic repulsion between SPV. and anionic segments of APh. Such difference between SPV and MV2+ was minimized in the case of the related monomer model. Retardation of the back reaction for the APh‐SPV system was also demonstrated by laser photolysis, kb= 8.7 × 107M‐1 s‐1 for the polymer system as compared to kb= 2.8 × 109M‐1 s‐1 for the monomer model system. Strong salt‐effects on the yield of the photoreduction and the rate of back reaction confirm the strong electrostatic interaction between the photoproducts and polyanions. This remarkable electrostatic effect of the polyanions was simulated by electrochemical redox reactions by using a graphite electrode coated with APh.
ROLE OF ENDOSYMBIOTIC ALGAE IN PHOTOKINESIS AND PHOTOPHOBIC RESPONSES OF CILIATES
Authors: Reisser Werner , Häder Donat‐P.
Published: January 2008

Abstract— The photobehavior of the ciliates Climacostomuum virens, Euplotes daidaleos and Paramecium bursaria associated with endosymbiotic green algae (Chlorella sp.) was compared with that of aposymbiotic ciliates (ciliates free of algae) and with the always aposymbiotic Paramecium arcticum. The aposymbiotic ciliates showed step‐up photophobic responses. The responses were more frequent and occurred at lower light intensities when the organisms contained endosymbiotic algae. In contrast, step‐down photophobic responses and photoaccumulations, as well as photokinesis, were never observed in aposymbiotic cells. These responses could be found only in ciliates when endosymbionts were present with the exception of C. virens, which showed none of these photoresponses.
MODELS FOR THE CHROMOPHORE STRUCTURE OF THE PHOTOTRANSFORMATION INTERMEDIATES OF PEA PHYTOCHROME IN VITRO
Authors: Sugimoto Tohru , Inoue Yasunori , Suzuki Hideo , Furuya Masaki
Published: January 2008

Abstract— The changes in the chromophore structure of pea phytochrome during phototransformation in vitro from the red‐light‐absorbing form (Pr) to the far‐red‐light‐absorbing form (Pfr), and from Pfr to Pr, were analysed in terms of wavelength and oscillator strength of absorption, using the zero‐differential overlap approximation of the molecular orbital theory for electrons. The effect of a point‐charge and a point‐dipole on the optical absorption of phytochromobilin intermediates were examined using the stationary perturbation theory for degenerate states. The results indicate that the cis‐trans photoisomerization of the pyrrole ring D, if any, occurred within 10 μs after a laser‐flash excitation of the phytochrome, and that the conformations of phytochromobilin and the protein moiety of phytochrome were not significantly changed during the period of examination of phototransformation in either direction.
INFLUENCE OF RUTHENIUM, RHODIUM AND VANADIUM IONS ON PHOTOPRODUCTION OF HYDROGEN BY Chlorella fusca
Authors: Paveti M. , Tausch H. , Stehlik G. , Roehr M.
Published: January 2008

Abstract Ru3+ and Rh3+ supplied at a concentration of 1 x 10−5 mol/l in the nutrient medium are incorporated preferably by the chloroplasts of Chlorella fusca cells as shown by electron micrographs without using any contrasting agent. Both elements cause a significant increase of production rate as well as of total hydrogen production. In experiments with synchronized C. fusca the maturing cells yielded maximal hydrogen production. Inhibition of hydrogen photoproduction by DCMU indicates that both photosystems are involved. Ru(bipy)32+, an essential component of photocatalysts, also is incorporated to a great extent and preferably bound to the thylakoid membranes of the chloroplasts but shows a negative influence on hydrogen production. V3+ is incorporated only to a small extent without any enrichment to the chloroplasts and shows no effect on hydrogen production.
AN EXAMPLE OF HOW PHOTOPHYSICAL PROPERTIES CAN INFLUENCE THE MAGNITUDE OF SOLVENT ISOTOPE EFFECTS UPON PHOTO‐OXIDATION REACTIONS
Authors: Davidson R. Stephen , Pratt Julie E.
Published: January 2008

Abstract Substantial isotope effects have been observed for the dye sensitised photo‐oxidation of 1,3‐diphenyl‐2‐pyrazoline in both polar and non polar solvents, implicating singlet oxygen as a reactive intermediate. By way of contrast, a solvent isotope effect upon the direct photo‐oxidation of the pyrazoline was only observed when a protic solvent (methanol) was used. It was found that the photophysical properties (e.g. quantum yields and fluorescence lifetimes) of pyrazolines are sensitive to the isotopic composition of protic solvents but not aprotic solvents. The solvent isotope effect observed for the direct photo‐oxidation reaction in methanol may not therefore be a true indication of the participation of singlet oxygen. Since this reaction may not be singlet oxygen mediated, an alternative mechanism is proposed.
ANOXIC PHOTODAMAGE IN THE PRESENCE OF PORPHYRINS: EVIDENCE FOR THE LACK OF EFFECTS ON MITOCHONDRIAL MEMBRANES
Authors: Salet C. , Moreno G. , Vever‐Bizet C. , Brault D.
Published: January 2008

Abstract When isolated mitochondria are irradiated in the presence of 50 μg/ml hematoporphyrin or hematoporphyrin derivative in the respiratory medium, the irradiation is at least twenty‐fold less effective in impairing the Ca2+ pump in the absence of oxygen than in its presence. This result suggests that photosensitization by non oxygen‐depending pathways has few or no effects on cell membranes, a result somewhat at variance with those observed with liposomes.
THE α‐CHYMOTRYPSIN EFFECT ON VARIOUS 9‐AMINOACRIDINE FLUORESCENT PROBE EMISSION
Authors: Marty Alain , Bourdeaux Madeleine , Amico Monique Dell' , Viallet Pierre
Published: January 2008

Abstract The influence of a‐chymotrypsin upon the fluorescence of various 9‐aminoacridine derivatives was examined. Fluorescence is quenched in the presence of this protein. Moreover, quenching is suppressed by the coexistence of hydrocinnamic acid, a competitive inhibitor of the enzyme activity. This leads us to conclude that there is a fluorescent complex formation between protein and fluorophores. Then, the apparent association constants were calculated and the florescence lifetimes of “free” and “bound” 9‐aminoacridine were determined by phase‐modulation fluorometry.

It is deduced that 9‐aminoacridine compounds are probably located in the enzymatic active site and that the fluorescence quenching is not due to specific interactions with amino acid residues but is a consequence of the characteristics of this binding site, in particular its hydrophobicity and polarity.

Alternatively, when these fluorescent probes are located in the vicinity of some aromatic amino acids (histidin, tryptophan and tyrosin), then the production of non fluorescent complex takes place. It is concluded that 9‐aminoacridine compounds can be used for the determination of the type of amino acid residues in the binding sites of proteins.
EXCITATION OF CHLOROPHYLL DURING THE PEROXIDASE‐CATALYZED OXIDATION OF ETHYL α‐FORMYLPHENYLACETATE
Authors: Adam Waldemar , Encarnación Luiz A. Arias , Cilento Giuseppe , Marcela H , Nassi Lilian
Published: January 2008

Abstract When micelle‐solubilyzed chlorophyll is present during the horseradish peroxidase catalyzed aerobic oxidation of ethyl α‐formylphenylacetate its fluorescence is observed. The excitation of chlorophyll may occur via energy transfer from the enzyme‐generated triplet ethyl benzoylformate. These results imply that excited states may be generated in the roots of Datura innoxia.
MECHANISM OF PHOTOINACTIVATION OF PLANT PLASMA MEMBRANE ATPASE
Authors: Imbrie C. W. , Murphy T. M.
Published: January 2008

Abstract UV radiation at 290 and 365 nm inactivates two forms of the K+‐stimulated ATPase associated with the plasma membrane of suspension‐cultured cells of Rosa damascena. One form is 15 and 36 times more sensitive than the other to 290 and 365 nm, respectively. For both forms, the inactivation requires oxygen, is inhibited by azide and diazobicyclo(2.2.2.2)octane, but not glycerol, and is enhanced up to 7.5 times in deuterium oxide solvent. Inactivation occurs concomitantly with loss of absorbance at 290 nm. Cs+ and NO−3, quenchers of tryptophan fluorescence, inhibit inactivation. The results suggest that inactivation involves singlet‐oxygen mediated destruction of tryptophans in the ATPases.
CAFFEINE‐ENHANCED PHOTOMOVEMENT IN THE CILIATE, STENTOR COERULEUS
Authors: Prusti Rabi K. , Song Pill‐Soon , Häder Donat‐Peter , Häderi Maria
Published: January 2008

The effects of caffeine, ionophores and calcium flux blockers on the step‐up photophobic response, phototactic orientation and the intracellularly recorded, light‐induced electrical action potential were studied in the ciliate, Stentor coeruleus. Caffeine alters the absorption and CD spectra and enhances the fluorescence of the photoreceptor pigment, stentorin. Independent of its effects on the spectroscopic properties of the photoreceptor pigment, caffeine shortens the photophobic response time by enhancing the Ca2+ conductivity of membranes, while Ca2+ flux blockers (LaCI3 or ruthenium red) prolong it; both effects cancel each other. Evidence is presented that phototactic orientation is brought about by repetitive photophobic responses, since a change in the phobic response time results in a decreased accuracy of phototaxis.
PHOTOSTIMULATION OF AGGREGATION IN THE CELLULAR SLIME MOLD Polysphondylium violaceum
Authors: Arnal Frank , Recer Gregg , Hanna Michael. H.
Published: January 2008

Abstract Aggregation in Polysphondylium violaceum is stimulated by light with an increase in the number of aggregates being one effect of light incubation. An aggregation‐stimulating factor, D factor, has been shown previously to cause phenotypic reversal of the aggregation‐defect in aggA mutants. The phenotypic reversal caused by D factor is stimulated by light. The initial time after starvation is the sensitive period for the light‐stimulated increase in aggregate formation in wild type strains and also for light‐stimulated sensitivity to D factor. At low light intensities both blue and green light have the greatest effect on the number of aggregates formed. However, the intensity dependence of the response is weak over the range tested (0.2 to 10 μW/cm2). Light also affects D factor causing as much as a 60‐fold decrease in production and a change in the proportion of the three active components of D factor when compared to D factor produced in darkness. Light affects a decrease in D factor production when it is present during development but only significantly affects the proportions of the D factor components if present prior to aggregation.
ACTION SPECTRA FOR THE IRIDOPHORE LIGHT RESPONSE IN THE NEON TETRA
Authors: Lythgoe J. N. , Shand Julia
Published: January 2008

Abstract The iridophores of some fishes such as the neon tetra (Paracheirodon innesi) are composed of alternating layers of guanine and cytoplasm. In the dark adapted state, the guanine layers are close together and reflect violet light. After illumination these layers separate and the iridophores reflect green light. The spacing change results from a direct action of light. Dose‐response curves show that more than one light sensitive mechanism are involved, but that at threshold the action spectrum fits a 461 nm porphyropsin absorbance curve.
PHOTOSENSITIZATION VIA CHARGE TRANSFER OR REVERSIBLE ELECTRON TRANSFER. OXIRANE ISOMERIZATION AND SULFUR DIOXIDE EXTRUSION
Authors: DAS P. K. , MULLER A. J. , GRIFFIN G. W. , GOULD I. R. , TUNG C.‐H. , TURRO N. J.
Published: January 2008

Abstract— N, N, N′ N′‐Tetramethylbenzidine (NTMB) photosensitizes the cis‐trans isomerization of stilbene oxiranes (SO) and the extrusion of SO2 from dibenzyl sulfone (DBS). In acetonitrile solution it is found that in the absence of SO or DBS, singlet NTMB undergoes three processes: intersystem crossing to triplet NTMB (φISC= 0.63, kISC= 6.3 × 107s‐1), fluorescence (φf= 0.30, kf= 3 × 107s‐1), and formation of a cation by electron ejection (φion= 0.09). Both singlet and triplet sensitization are observed. A charge transfer or reversible electron transfer mechanism is proposed to explain the results.
AN ACTION SPECTRUM FOR PHOTOTAXIS BY PSEUDOPLASMODIA OF Dictyostelium discoideum
Authors: POFF KENNETH L. , HÄDER DONAT‐P.
Published: January 2008

Abstract— The sensitivity of phototactic orientation of pseudoplasmodia (slugs) of the cellular slime mold Dictyosrelium discoideum has been measured for white light and monochromatic light using computer aided directional statistics. The zero threshold for white light was found at about 10‐5 Ix. An action spectrum for positive phototaxis has been calculated from fluence rate‐response curves; it shows two major maxima at about 420 and 440 nm and secondary peaks at 560 and 610 nm. This action spectrum is significantly different from the one for phototactic orientation in Dictyostelium amoebae.
ANALYSIS OF MULTIPLE PHOTORECEPTOR PIGMENTS FOR PHOTOTROPISM IN A MUTANT OF Arabidopsis thaliana
Authors: Konjević Radomir , Khurana Jitendra P. , Poff Kenneth L.
Published: January 2008

Abstract

The shape of the fluence‐response relationship for the phototropic response of the JK224 strain of Arabidopsis thaliana depends on the fluence rate and wavelength of the actinic light. At low fluence rate (0.1 μmol m‐2s‐1), the response to 450‐nm light is characterized by a single maximum at about 9 μmol m‐2. At higher fluence rate (0.4 μmol m‐2s‐1), the response shows two maxima, at 4.5 and 9 μmol m‐2. The response to 510‐nm light shows a single maximum at 4.5 μmol m‐2. Unilateral preirradiation with high fluence rate (25 μmol m‐2s‐1) 510‐nm light eliminates the maximum at 4.5 μmol m‐2 in the fluence response curve to a subsequent unilateral 450‐nm irradiation, while the second maximum at 9 μmol m‐2 is unaffected. Based on these results, it is concluded that a single photoreceptor pigment has been altered in the JK224 strain of Arabidopsis thaliana.
DETERMINATION OF CYTOSINE‐CYTOSINE PHOTODIMERS IN THE DNA OF CLOUDMAN S91 MELANOMA CELLS USING HIGH PRESSURE LIQUID CHROMATOGRAPHY
Authors: Niggli Hugo J.
Published: January 2008

Abstract

I measured the induction of cytosine‐cytosine dimer (C‐C) densities after UV‐C (< 290 nm) and UV‐B irradiation (290–320 nm) in the 2′‐deoxy‐[3H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV‐B exposure resulted in 0.000034% C‐C/J m‐2 of the total cytosine radioactivity which is 10 times less than the rate during UV‐C irradiation. Previous work with these melanoma cells showed a 4‐fold lower rate of induction of thymine‐containing pyrimidine dimers by UV‐B than UV‐C light (Niggli Photochem. Photobiol. 52, 519–524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV‐C and UV‐B exposure. However, UV‐C and UV‐B light induce 10–20 times more thymine‐containing pyrimidine dimers than C‐C in the DNA of S91 cells.
THE EFFECT OF pH ON THE AEROBIC and ANAEROBIC PHOTOLYSIS OF TRYPTOPHAN AND SOME TRYPTOPHAN‐CONTAINING DIPEPTIDES
Authors: Hibbard L. B. , Kirk N. J. , Borkman R. F.
Published: January 2008

Abstract— Rates of photolysis, quantum yields of fluorescence, and fluorescence emission maxima for the dipeptides glycyltryptophan (Gly‐Trp) and tryptophylglycine (Trp‐Gly) and for free tryptophan (Trp) were determined under both degassed and aerated conditions in the pH range 4.5‐10.0. The photolyses were performed at 25°C using 290 nm radiation from a 1000 W xenon lamp. Photolysis rates were determined by monitoring tryptophan fluorescence loss with time. It was found that Trp‐Gly and free Trp showed similar behavior in that their fluorescence quantum yields and photolysis rates increased significantly above neutral pH. In contrast, the Gly‐Trp fluorescence yield was smaller than that of Trp or Trp‐Gly, showing no significant increase at high pH and the photolysis rate for Gly‐Trp decreased with increasing pH. In comparing aerated to degassed samples, it was found that degassing had a far greater effect on the photolysis rates of Trp and Trp‐Gly than on the photolysis rate of Gly‐Trp especially at higher pH. But, degassing did not change the relative fluorescence quantum yields or fluorescence emission maxima of any of the three compounds. Possible mechanisms for photolysis under various experimental conditions were examined in light of the data.
THE USE OF SHORT LIVED FLUORESCENT DYES TO CORRECT FOR ARTIFACTS IN THE MEASUREMENTS OF FLUORESCENCE LIFETIMES
Authors: Mauzeraix D. , Ho P. P. , Alfano R. R.
Published: January 2008

Abstract— The ultrafast emission for fluorophores can be used as the effective excitation pulse for prompt response measurements by photo detectors in the same spectral region as that of unknown samples. This method corrects for such artifacts as wavelength and spatial dependence of the response function of the photodetector. It is shown that the emission from triphenylmethane dyes is an excellent effective pulse with relaxation time 2 ps in the red region of the spectrum. A microchannel plate photomultiplier has only a 35 ps increase in response or lag time between excitation at 420 nm and emission at 680 nm.
LIGHT INDUCED FLUORESCENCE SPECTRAL CHANGES IN NATIVE PHYTOCHROME FROM Secale cereale L. AT LIQUID NITROGEN TEMPERATURE
Authors: Inoue Yasunori , Hamaguchi Hiro‐o , Yamamoto Kotaro T. , Tasumi Mitsuo , Furuya Masaki
Published: January 2008

Abstract— Fluorescence spectra of native rye phytochrome were determined under different light conditions at liquid nitrogen temperature. Fluorescence spectrum of the red‐light‐absorbing form (Pr) had a major peak at about 685 nm (14 600 cm−1) and a broad sub‐peak at about 515 nm (19 400 cm−1). The peak height at 685 nm was reduced by irradiation with monochromatic light of 640 nm, and a new peak became obvious at about 702 nm (14250 cm−1). This spectral change was almost completely reversed by subsequent irradiation with 700‐nm light. Fluorescence spectrum of the photoequilibrium mixture of Pr and far‐red‐light absorbing form under continuous red light showed a sharp peak at about 685 nm having a peak height ca. 12% of Pr, and a broad sub‐peak at about 508 nm (19 700 cm−1). Light of 730 nm did not reduce the peak height at about 685 nm but induced a new shoulder at about 699 nm (14300 cm−1). Monochromatic light of 640 and 700 nm given following the light of 730 nm could not reverse the spectral change at 699 nm induced by the irradiation with 730‐nm light. Fluorescence spectrum of Pr in partially degraded phytochrome was similar to that in native phytochrome but the peak position in the red region was shifted by about 5 nm (100 cm−1) to the blue.