bluuebunny/crossref_metadata_2025_split huggingface dataset:
EXCIPLEX STUDIES–V. ELECTRON EJECTION FROM INDOLE AND METHYL‐INDOLE DERIVATIVES*
Authors: HOPKINS T. R. , LUMRY R. 
Published: January 2008

Abstract— Electron‐scavenging experiments with N2O as scavenger demonstrate at least two electron‐producing reactions of the excited singlet states of the exciplex species formed by indole or 1 ‐methyl‐indole with water. Most electrons reacting with N2O result from collision of the scavenger with a metastable state formed from the initial exciplex state but finite electron yields from indole and 1‐methyl‐indole at limiting scavenger concentrations suggest that the intermediate states also eject electrons directly into the solvent. The formation of the first metastable state from the fluorescent exciplex state has an activation energy, EM, estimated to be about 13 kcal/mole for both indole and 1 ‐methyl‐indole water exciplexes. The EM values for 1‐methyl‐indole from fluorescence and electron yields are the same, Indicating that at neutral and alkaline pH fluorescence quenching and electron extraction are both being controlled by the formation of the first metastable intermediate. Observed electron yields from indole‐water and indole‐methanol exciplexes are less than predicted using fluorescence data, although EM values of 1 kcal/mole are obtained for the indole‐methanol exciplex by both methods. At pH 12·0 and 28°C the total electron yields for indole‐water and 1 ‐methyl‐indole‐water exciplexes are 0·30 and 0·25, respectively. The residual yields attributed to outright formation of hydrated electrons from the initial exciplex excited stateare 0·11 and 0·05, respectively. Electron yields from the indole‐water exciplex are strongly pH dependent only near pH 1 where the fluorescence yields as well as the electron yields decrease rapidly with increasing acidity. The 1‐methyl‐indole‐water exciplex shows an additional pH dependence which is first‐order in hydrogen‐ion activity and has an effective pKa of about 11·5. Comparable yields for indole and 1‐methyl‐indole are found only above pH 12.High electron yields are found with indole in the exciplex‐forming solvent dioxane and in the non‐exciplex forming solvent cyclohexane. For the latter system electrons are probably derived only from the lowest excited state of indole on collision with N2O.
LIQUID‐HOLDING EFFECTS IN U.V.‐IRRADIATED PHAGE T3*
Authors: MARTIGNONI S. , HARM W. 
Published: January 2008

Abstract— Holding complexes of u.v.‐irradiated (254 nm) T3 phage in E. coli B/r cells for several hours at 37°C in buffer, or broth with chloramphenicol, affects the phage survival in at least two different ways: (1) by enhancing excision repair, resulting under certain conditions in liquid‐holding recovery (LHR), and (2) by destroying the phage (holding inactivation). LHR is most apparent in buffer containing 20 μg ml‐1 chloramphenicol (CAP). It is expressed by as much as a 10–fold increase in the fraction of complexes that display host‐cell reactivation (resulting from excision repair), but the percentage of u.v. lesions repaired within repair‐proficient complexes is slightly decreased. LHR is not observed if T3 infects the repair‐deficient strain Bs‐1.Holding inactivation is readily observed with unirradiated phage complexes in broth containing CAP. The response of irradiated‐phage complexes to liquid‐holding conditions is more complex: holding inactivation is less effective for irradiated than for unirradiated phage DNA (i.e. the irradiated DNA is to some extent ‘protected’), and processes leading to LHR are superimposed. Thus under certain holding conditions one observes the paradoxical phenomenon that the viable titer of irradiated phage is several times higher than that of unirradiated phage.The nature of holding inactivation is not known, nor is the mechanism by which irradiated DNA is partially protected against it. Holding inactivation does not require protein synthesis; it is rather enhanced at high CAP concentration and seems to be favored by otherwise active cell metabolism. At high CAP concentrations (200–400 μg ml‐1, as compared to 20 μg ml‐1) irradiated‐phage complexes show neither LHR nor protection against holding inactivation. Likewise they fail to undergo some step by which the phage DNA becomes insensitive to repair inhibition by caffeine.
MODIFICATION DU TAUX DES NUCLEOTIDES ADENYLIQUES (ATP, ADP et AMP), PAR UN ECLAIREMENT DE LUMIERE ROUGE‐CLAIR (660 nm)
Authors: SANDMEIER M. , IVART J. 
Published: January 2008

Abstract— In oat meSocotyl tissue (Avena sativa, var. Nuprime), red light (660 nm) modifies the level of adenylic nucleotides. Two types of action have been shown. The first takes place during illumination; there is an increase in the level of ATP and, at the same time, a decrease of ADP. This effect disappears within 5 min after the end of illumination. The second takes place 1–2 hr after illumination when mesocotyl segments are put in growth medium. The ATP level drops in the red‐illuminated fragments compared to those kept in the dark. There is no difference in the ADP level under these two conditions.It is not yet known if this light action is a phytochrome‐mediated process.
ABSORPTION SPECTRA OF TCA‐DENATURED RHODOPSIN AND OF A SCHIFF BASE COMPOUND OF RETINAL
Authors: SUZUKI T. , KITO Y. 
Published: January 2008

Abstract— When TCA‐denatured rhodopsin was frozen in liquid nitrogen, Λmax was markedly shifted to longer wavelengths as the concentration of TCA increased. After TCA denaturation, species specific absorption disappeared and the absorption maxima of the squid pigments became identical with those of corresponding pigments of octopus.In solutions at 5° the bathochromic shift of Λmax of TCA denatured rhodopsin was observed at higher concentrations of TCA than in the frozen state. Λmax of N‐retinylidene‐butylamine (NRB) was also displaced towards longer wavelengths with increasing concentrations of TCA. This bathochromic shift was enhanced by freezing. The mode of the bathochromic shift of Λmax provoked by TCA was very similar both in the cases of denatured rhodopsin and of NRB. The absorption spectrum of NRB was identical in shape with that of TCA‐denatured rhodopsin, as the half‐band widths of both materials were about 5500 cm‐1 in the liquid state and 5000 cm‐1 in the frozen state. Λmax of retinal and NRB were red shifted in polar and polarizable solvents.It was concluded that the strong acidity and the relatively large polarizability of TCA are responsible for the bathochromic shift of Λmax of the Schiff base in TCA‐denatured rhodopsin.
ON THE FORMATION OF PHOTOSYNTHETIC MEMBRANES IN BEAN PLANTS*
Authors: Argyroudi‐Akoyunoglou J. H. , Akoyunoglou G. 
Published: January 2008

Abstract— The formation of lamellar chlorophyll‐protein complexes I and II, solubilized by sodium dodecyl sulfate, was studied by hydroxylapatite column chromatography during greening of etiolated Phaseohis vulgaris leaves.The protein moiety of both complexes preexists in the prolamellar body of etiolated tissue. The complex II to complex I protein ratio is of the order of 0.5. During greening in intermittent illumination the ‘proto’‐chloroplast is agranal, and contains ‘primary’ thylakoids and chlorophyll a (Chl a). At this stage the complex II to complex I protein ratio increases only slightly. Further greening of the plant tissue in continuous illumination results in grana, Chi b (chlorophyll b) and more Chl a formation. The complex II to complex I protein ratio in unfractionated thylakoids is now of the order of 2.5, while in grana it is of the order of 4.0.The binding of chlorophyll formed during greening to the protein moiety of the two complexes is found to be selective. The Chi a selectively formed under intermittent illumination is more strongly bound to the complex I protein. The Chi b and Chl a formed in continuous illunination are found bound to both complex I and complex II proteins.Analysis by hydroxylapatite column chromatography of subchloroplast fractions obtained by different fractionation procedures have shown that these two chlorophyll‐protein complexes are most probably derived from the PSI (photosystem I) and PSII (photosystem II) particles of the photosynthetic membrane. These findings suggest that PSI units are assembled ahead of PSII units. Moreover, they indicate that the complex I protein is the main protein component in the prolamellar body membranes, the ‘primary’ thylakoids. and the stroma lamellae, while in the grana membranes the major protein is the complex II protein. Finally our results show that formation of the photosynthetic membranes is a multi‐step process.
FLUORESCENCE AND PHOTOCHEMISTRY OF OLIGOCYTIDYLIC AND POLYCYTIDYLIC ACIDS IN AQUEOUS SOLUTION
Authors: Vigny Paul , Favre Alain 
Published: January 2008

Abstract—In addition to the monomer‐like fluorescence, a long‐wavelength emission (Λmaxem= 410 nm) has been detected in the dinucleoside 5′‐5′ pyrophosphate (CppC) at room temperature. This emission looks very similar to that previously reported for the acidic forms of Poly C (Poly C. Poly C+ and Poly I. Poly C. Poly C+). Only the monomer‐like emission (Λmaxem= 330 nm) can be detected in neutral Poly C, acidic CppC, and the neutral or protonated forms of the dinucleoside phosphate CpC.A correlation between the room temperature fluorescence of oligo and polycytidylic acids and their photochemical behaviour is found. Irradiation of all the polymeric samples at both neutral and acid pH results in the formation of minor photoproducts. They have been characterized by their absorbance (in the range 300–400 nm) and their fluorescence spectra. The same product is obtained in all cases where the monomer‐like fluorescence only is detected. Distinct products are formed in neutral CppC and in the acidic Poly C forms.The results are discussed with respect to the conformation of the oligo and polycytidylic acids and possible relationships between the 410–420 nm emission and adduct formation. An excimer is proposed as a common, intermediate excited state in both radiative deactivation and adduct formation in neutral CppC and the acidic Poly C forms.
EVIDENCE AGAINST DNA AS THE TARGET FOR 334 NM‐INDUCED GROWTH DELAY IN ESCHERICHIA COLI*
Authors: Ramabhadran T. V. , Jagger J. 
Published: January 2008

Abstract— Growth delay was induced with near‐UV (334 nm) radiation in Escherichia coli K12 bacterial strains followed by attempts at photoreactivation (PR) of this effect at 405 nm. In the UV‐sensitive strain AB2480, a small PR of the observed population growth delay occurred after 334 nm irradiation at 35°C and a much larger PR after 334 nm irradiation at 5°C. However, much of the population growth delay in this strain can be explained as being due to killing, and all or most of the observed PR pertains only to this killed fraction of the population. The true cell growth delay (i.e. that of surviving cells) thus appears to be only slightly, if at all, photoreactivable. This conclusion is supported by studies with a wild‐type strain KW8, which shows growth delay at non‐lethal doses; this growth delay shows no PR, regardless of the temperature during 334 nm irradiation. These findings indicate that photoreactivable lesions (cyclo‐butyl pyrimidine dimers) are not an important cause of near‐UV‐induced growth delay.Strain AB2480 lacks known dark‐repair systems for DNA damage induced by far‐UV (below 300 nm) radiation, yet shows the same efficiency for 334‐nm‐induced growth delay as the wild type, which possesses these dark repair systems. This indicates that lesions in DNA that are dark‐repairable by the systems not tunctional in AB2480are not responsible for 334‐nm‐induced growth delay. It is possible, however, that fragmentary repair systems in AB2480 can operate on some DNA lesion that might cause growth delay.Spontaneously decaying lesions are unlikely, since growth‐delay damage decays at a very low rate in non‐nutrient medium.Since most of the known types of DNA damage and repair are thus eliminated, these considerations suggest that DNA damage is not involved in near‐UV‐induced growth delay.
ACTION SPECTRUM AND ELECTROPHYSIOLOGICAL RESPONSES CORRELATED WITH THE PHOTOPHOBIC RESPONSE OF STENTOR COERULEUS
Authors: Wood David C. 
Published: January 2008

Abstract— The blue‐green ciliate. Stentor coeruleus, is found predominantly in shady places. This concentration occurs because stentor responds when swimming from a shaded area to a lighted area by reversing the direction of its ciliary beat and reorienting its swimming direction until it once again is in the shaded area. A graded receptor potential is recorded from microelectrodes in vacuoles of stentor when the animal is photically stimulated. For all but very weak stimuli this receptor potential is sufficient to elicit a regenerative transmembrane response of variable amplitude in a swimming animal. Suprathreshold electrical stimuli also elicit this regenerative response. In turn the regenerative response is coupled to ciliary reversal. Thus ciliary reversal appears to be produced whenever the photic receptor potential crosses the threshold for elicitation of the regenerative response.Using the threshold for production of ciliary reversal as a criterion response, an action spectrum was obtained. This action spectrum correlates well with the absorption spectrum of the major pigment of S. coeruleus, stentorin. Stentor bleached of pigment also have an elevated threshold for ciliary reversal. Thus stentorin seems to be the photosensitive pigment in stentor responsible for its photophobic behavior.
A SURVEY OF EPR INVESTIGATIONS OF BACTERIAL PHOTOSYNTHESIS
Authors: Corker G. A. 
Published: January 2008

Abstract— Investigations in which EPR has been used as a probe of the mechanism of the primary quantum conversion reaction and/or electron transport reactions in bacterial photosynthesis are surveyed. These investigations include studies of whole cell organisms and simpler sub‐cellular preparations, chromatophores and bacteriochlorophyll‐protein complexes.Electron paramagnetic resonance studies have successfully demonstrated that the primary donor of the photosynthetic, photochemical reaction involves a dimer of bacteriochlorophyll, generally referred to as P870. P870 is photochemically oxidized to a cation radical which exhibits a g= 2.0025 EPR signal. Comparative studies of the time behaviour of this signal in whole cells and in sub‐cellular preparations show that electron flow in the whole cells is substantially different than in the cell‐free systems.The primary acceptor molecule of the photochemical reaction has not been conclusively identified. When it is photochemically reduced, it exhibits a broad EPR absorbance centered at g= 1.8 observable only at low temperatures. This signal involves an iron atom and a quinone molecule. Two possible identifications of the species responsible for the g= 1.8 signal are an iron‐quinone complex and an iron‐sulfur protein. The latter identification would require that one primary acceptor function for two primary donors and that the removal of a tightly held quinone alter the integrity of the system so as to inhibit the photochemistry.When the primary acceptor is chemically reduced, a photo‐induced, polarized triplet EPR spectrum is detected. Both absorption and emission lines are, observed as if only one substate (m= 0) of the triplet manifold is populated. The zero field parameters of the triplet spectrum suggest that the triplet is formed through a decay of a biradical, not through an optical singlet to triplet transition.Low temperature EPR studies of photosynthetic preparations which had been poised at room temperature by subjecting the preparations to different redox potentials and/or dark adaptation and illumination show the presence of a number of light‐influenced, EPR active components. The spectral characteristics of these components are indicative of iron‐heme (both low and high‐spin forms) and iron‐sulfur (both oxidized and reduced) proteins and at least one other organic free radical distinct from P870+. The spectra varied for different strains of bacteria. Also, some of the signals detected in the whole cell organism were not detected in cell free preparations and the kinetics of the light influenced signal amplitudes were different in the whole cells than in chromatophores.
PHOTOSENSITIZING EFFECTS OF 8‐METHOXYPSORALEN ON THE SKIN OF HAIRLESS MICE—11. TRAIN AND SPECTRAL DIFFERENCES FOR TUMORIGENESIS
Authors: Grube D. D. , Ley R. D. , Fry R. J. M. 
Published: January 2008

Abstract— The photosensitizing effects of 8‐methoxypsoralen on the skin of two strains of hairless mice were studied using fractionated exposure to UV Spectral dependent differences for tumorigenesis were studied by comparing the tumor responses to three different spectra; the exposure levels for each spectrum here adjusted in proportion to their relative efficiencies for tissue damage and cytokinetic responses. There were no strain differences in the spectral dependent induction of cutaneous damage or estimates of the photomediated interstrand cross‐linking of epidermal DNA by 8‐methoxypsoralen.Squamous cell carcinomas were induced in the photosensitized skin of both strains of mice after fractionated exposures to emissions at principally 365 nm. Exposures to a broader spectrum of light resulted in the earlier appearance of tumors in the photosensitized skin of the SKH: hairless‐1 mice, but produced few or no tumors in the HRS/J/Anl strain. In a second series of experiments; mice were exposed to a fluorescent sun lamp prior to each combined treatment of psoralen and exposure at 365 nm to determine the influence of shorter wavelengths of UV on the tumor response. These treatments resulted in an enhanced expression of tumors in the SKH:hairless‐1 mice as compared to the HRS/J/Anl strain.Under the conditions of the experiments, the marked strain and spectral dependent differences for tumorigenesis demonstrated that although treatments that induce psoralen photoadducts also induce tumors. there was no apparent quantitative correlation between the occurrence of DNA cross‐links and the incidence of tumors. The results also suggested, first, an interaction between UV (280–400 nm) induced photoproducts and psoralen photoadducts and secondly, a strain difference in the oncogenic effects of this interaction.
THE EFFECT OF MOLECULAR POLARIZATION ON THE ELECTROCHROMISM OF CAROTENOIDS—I. THE INFLUENCE OF A CARBOXYLIC GROUP
Authors: Reich Roland , Sewe Kai‐Udo 
Published: January 2008

Abstract—Electrochromism of oriented all‐trans‐β‐apo‐8′‐carotenoic acid is studied in thin capacitors. The linear electrochromism is very strong, in contrast to that of symmetrical carotenoids. It is proportional to the first derivative of the absorption spectrum. The quadratic electrochromism can be described as a superposition of fractions proportional to the first and second derivatives of the absorption spectrum. The permanent dipole moment difference between the ground state and the excited state of the carotenoic acid molecule is Δμ= 3.6 × 10‐29C·m (±20%) (10.7 Debyes). The polarizability difference parallel to the long axis of the molecule is Δα|| = 1.17 × 10‐37C·m2·V‐1(±20%) (1050 Å3). Furthermore, the relative permittivity of the solid carotenoic ethyl ester isr= 3.5 ± 0.2.Δμ is due to the polarizing force of the carboxylic group. This force is equivalent to a mean local electric field ofFt≅3 × 106V/cm. Such a “local field” may also be exerted on a symmetrical carotenoid in the membrane of photosynthesis, e.g. by asymmetrical complex formation with a polarizing molecule. To obtain an effective permanent field ofFp≅ 2 × 106V/cm across the membrane, as postulated in photosynthesis, a local field ofFl≅ 5.5 × 105V/cm would be sufficient.Fpis shown to be directed from inside to outside of the thylakoid. To realize this, e.g. a positive polar (i.e. electron‐attracting) complex partner of the carotenoid, located more to the inside of the thylakoid, can be postulated.
THE EFFECT OF IRON ON THE DISTRIBUTION OF SUPEROXIDE AND HYDROXYL RADICALS AS SEEN BY SPIN TRAPPING AND ON THE SUPEROXIDE DISMUTASE ASSAY
Authors: Buettner Garry R. , Oberley Larry W. , Leuthauser Susan W. H. Chan 
Published: January 2008

Abstract— Using the spin trap 5,5‐dimethyl‐1‐pyrroline‐1‐oxide we have demonstrated the presence of OH in the xanthine‐xanthine oxidase system when iron and/or iron‐EDTA (ethylenediamine‐tetraacetic acid) is present. With increasing iron (or iron‐EDTA) concentration the intensity of the O2‐ spin adduct decreased while that of OH increased. However, use of diethylenetriaminepentaacetic acid (DETAPAC) as a metal chelator in the reaction mixture suppressed the OH spin adduct signal while maintaining the intensity of the signal from the O2‐ spin adduct.Use of EDTA to eliminate the interfering effects of metal ions in the superoxide dismutase assay employing xanthine oxidase and nitroblue tetrazolium introduces an artifact from the iron present. The interference in the assay from metal ions, including iron, can be eliminated with use of DETAPAC as a metal chelator. Thus, it is possible to make comparisons of measured superoxide dismutase activities even when there are variations in the amount of iron present in the samples.
THE REACTION BETWEEN SUPEROXIDE ANION AND HYDROGEN PEROXIDE
Authors: Ferradini Christians , Foos Jacques , Houee Chantal , Pucheault Jacques 
Published: January 2008

Abstract— In order to obtain a better understanding of the kinetics of the Haber‐Weiss reaction
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often proposed as a source of OH radicals, we have measured the decomposition rate of H2O2 in aqueous solutions by y rays and for different pH values. This decomposition proceeds by a chain reaction involving the preceding one as the propagating step.The rate constant found is to be
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THE EFFECT OF 1,4‐DIAZABICYCLO[2.2.2]OCTANE ON THE RADIOSENSITIVITY OF BACTERIA
Authors: Anderson Robert F. , Patel Kantilal B. 
Published: January 2008

Abstract— Hydroxyl radicals ('OH) are scavenged by 1,4‐diazabicyclo[2.2.2]octane (DABCO) at a diffusion‐controlled rate of 1.25 ± 0.1 × 109M‐1s‐1. Unlike other efficient 'OH scavengers which exhibit protection of bacteria against irradiation both in oxic and hypoxic conditions, DABCO has been shown to protect Serratia marcescens and various strains of Escherichia coli only in oxic conditions.DABCO appears to eliminate a component of the sensitization afforded by oxygen in all strains of E. coli tested. The level of this protection increases from ∼15% in the wild type AB 1157 to ∼100% in the recA uvrA mutant AB 2480. It is suggested that DABCO protects against lethal events that can occur on macromolecules other than DNA such as the cell membrane.Results with added glycerol, as well as work in D2O solution, indicate that DABCO is more likely to be acting by scavenging radicals rather than by quenching 1O2. If 1O2 is a component of the sensitization afforded by oxygen, then it is unlikely to be formed in a hydrophilic environment in the cell.