bluuebunny/crossref_metadata_2025 huggingface dataset:
FLUORESCENCE INDUCTION IN THE RED ALGA PORPHYRIDIUM CRUENTUM
Authors: MOHANTY P. , PAPAGEORGIOU G. , GOVINDJEE
Published: January 2008

Abstract— The intensity dependence and the spectral changes during the fast (sec) and the slow (min) transient of chlorophyll (Chl) a fluorescence yield, measured at 685 nm, have been analyzed in the red alga Porphyridium cruentum. Both the fast and the slow fluorescence yield changes are affected differently by the inhibitors of electron transport (e.g., DCMU) and by the uncouplers of phosphorylation (atebrin and FCCP). Fixation of Porphyridium cells with glutaraldehyde abolishes most of the fluorescence yield changes except for the so‐called very fast (OI) phase. The same fixed cells, however, reduce DCPIP (a Hill oxidant) but do not evolve O2 when CO2 is used as electron acceptor. We interpret these and other results by the hypothesis that fluorescence transients in intact cells are linked to both electron transport and the energy dependent structural changes in the thylakoid membrane.
CHANGES IN U.V. SURVIVAL CURVES OF ESCHERICHIA COLl B/r CONCOMITANT WITH CHANGES IN GROWTH CONDITIONS
Authors: RUDÉ J. , ALPER TIKVAH
Published: January 2008

Abstract— For E. coli B/r u.v.‐irradiated while in logarithmic growth, the nature of the dose‐response curve was strongly dependent on both pre‐ and post‐irradiation conditions of growth. Survival curves for cells grown in nutrient medium, or minimal medium with glucose, and plated immediately after irradiation, demonstrated an initial insensitive or ‘shoulder’ region provided the plating medium was such that no derepression was required of operons controlling inducible enzyme systems. If, however, such derepression was called for, survival curves were of exponential form. Delay in plating resulted in the return of the survival curve to the shouldered form even when ‘shift‐down’ media were used.

Of those cells grown before u.v.‐irradiation in minimal media and plated thereafter with the same sugar as carbon source, only those grown with glucose (or lactose) demonstrated the shouldered survival curve.
FORMES TRANSITOIRES DES CAROTENOIDES: ETAT TRIPLET ET RADICAL‐CATION
Authors: MATHIS P. , VERMEGLIO A.
Published: January 2008

Abstract— Reactions between toluidine blue (a thiazine dye) and carotenoids (β‐carotene and zeaxanthine) were studied by flash photolysis, in ethanolic solutions. Two types of reactions were evidenced:

a triplet‐triplet energy transfer from the triplet state of monoprotonated toluidine blue to the carotenoid whose triplet state decays rapidly (t1/2= 5μsec).

an electron transfer from the carotenoid to the mono‐ and bi‐protonated triplet states of toluidine blue. This produces a radical‐cation of the carotenoid (Car+) which decays slowly (t1/2˜ 200 μsec) and has a strong absorption band around 900 nm.
THE TIME SEQUENCE OF EVENTS DURING EXCISION REPAIR IN TETRAHYMENA PYRIFORMIS
Authors: BRUNK C. F.
Published: January 2008

Abstract— The time sequence of events during excision repair of DNA in Tetrahymena pyriformis was investigated after sublethal dose of u.v. radiation. Buoyant‐density analysis of the DNA from repairing cells grown in medium containing 5′‐bromodeoxyuridine makes it possible to distinguish repair synthesis from normal synthesis. Analysis of the DNA synthesized at various times after irradiation clearly indicates that repair synthesis starts very quickly after irradiation and is completed within 3 to 4 hr. Immediately after irradiation, normal DNA synthesis is greatly depressed but gradually resumes until it predominates after 3 to 4 hr. The molecular weight of DNA strands is reduced and the net rate of DNA synthesis is depressed immediately after irradiation. Both of these parameters are restored to their pre‐irradiation values by 3 to 4 hr after irradiation. During the repair period the majority of the pyrimidine dimers are removed. All of the data indicate that repair begins immediately after irradiation and is completed in 3 to 4 hr (about two thirds of a generation period).
ESR STUDY OF A NEW LIGHT‐SENSITIVE FREE RADICAL IN THE COATS OF WHEAT AND OTHER SEEDS
Authors: WINDLE J. J.
Published: January 2008

Abstract— The endogenous free radical signal in the coat of wheat and other seeds is found to increase rapidly upon exposure to light from a high pressure mercury lamp reaching a saturation value in about one hour. Upon dark storage the signal slowly decays to approximately its initial value after a number of days. Re‐exposure to the light causes the signal to again increase. The signal also depends inversely and reversibly upon moisture content. The dynamic behavior of the signal indicates that the radicals are produced from a limited number of centers in the seed coat. The identity of these centers is still unknown, but our results rule out such possibilities as chlorophyll, melanin and phenolic compounds and suggest that a new light‐sensitive component is present in the outer coating of seeds.
IN VIVO MEASUREMENTS OF THE PHYTOCHROME PHOTOSTATIONARY STATE IN FAR RED LIGHT
Authors: SCHÄFER E. , MARCHAL B. , MARMÉ D.
Published: January 2008

Abstract— The in vivo photostationary state, ϕfr= ([Pfr]fr/[P]), of phytochrome in far red light has been determined in mustard seedling cotyledons by three different methods. The ϕfr is a function of the length of time of etiolation (t= 36 hr, ϕfr= 0·14; t= 72 – 120 hr, ϕfr= 0·075). The calculated ϕr= 0·8. The amount of Ptot is strongly dependent on the time of onset of far red light. These data imply that it would be almost impossible to maintain a constant level of Pfr in mustard cotyledons over a considerable period of time.
PHOTOSENSITIZED DIMERIZATION OF URACIL
Authors: JENNINGS B. H. , PASTRA‐LANDIS S. , LERMAN J. W.
Published: January 2008

Abstract— The four isomeric dimers of uracil were isolated from photochemical reactions which were sensitized by acetone. Product analyses, made on the basis of the chemical properties of the compounds, showed that the h, h dimers predominate. Infrared and mass spectra for the dimers are here presented as well as nuclear magnetic resonance data. The syn h, h dimer has been found in two polymorphic forms.
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.
PHOTODISSOCIATION OF CARBON TETRACHLORIDE SENSITIZED BY NAPHTHALENE DERIVATIVES‐I. RADICAL‐CHAIN REACTION IN THE SYSTEM NAPHTHALENE‐METHANOL‐CARBON TETRACHLORIDE
Authors: SCHLICHT G. , SCHULTE‐FROHLINDE D.
Published: January 2008

Abstract— Irradiation of naphthalene in methanol in the presence of carbon tetrachloride with light of 313 nm wavelength forms hydrochloric acid, chloroform, and formaldehyde as the main products. The quantum yields of these products are larger than 1 (up to 50, depending on the concentrations of reactants and sensitizer and on temperature). The quantum yield for the disappearance of the sensitizer naphthalene is smaller than 0.3. From these results it is concluded that the products are built up by a chain reaction with CC13 and CH2OH radicals as intermediates.
CORRECTION FACTORS IN CALCULATING ABSORBED LIGHT INTENSITIES
Authors: JONES S. H. , SALISBURY K.
Published: January 2008

Abstract— A semi‐rigorous treatment for errors involved in correcting absorbed light intensities based on measurement of transmitted intensities is given. Several common systems are discussed: vapour system with a vapour actinometer, vapour system with a liquid actinometer, and liquid system with a liquid actinometer. In each case, correction factors have been calculated, which can be conveniently applied to the majority of quantitative photochemical systems. In addition, a treatment is given for the case where a separate cell containing the actinometer is used in place of a photodiode.
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 MECHANISM OF FLUORESCENCE QUENCHING IN PYRENE‐ AND 3,4‐BENZOPYRENE‐1,3,7,9‐TETRAMETHYLURIC ACID SYSTEMS
Authors: MATSUYAMA A. , NAGATA C.
Published: January 2008

The interaction between aromatic hydrocarbons and purine or its analogues has been widely noted in connection with the possibility of complex formation between carcinogens and DNA or its precursors. Weil‐Malherbe[1], Boyland and Green[2] reported that 1,3,7,9‐tetramethyluric acid (TMUA) solubilizes aromatic hydrocarbons in aqueous solution and exerts a strong quenching action on fluorescence of the hydrocarbons. The solubilization has been attributed to formation of a molecular complex [2]. Complex formation is now thought to be mainly due to van der Waal's force (polarization and dispersion force) rather than charge transfer (CT) one[2,3–5]. Van Duuren [3,5] examined fluorescence spectra of TMUA‐hydrocarbon complexes both in solution and in potassium bromide pellets. In solution, the fluorescence spectrum of the complex showed no change in the position of the maximum and in intensity, when compared with that of the free hydrocarbon. In the solid state, however, a blue shift was observed for the fluorescence of the complex. From these results, it was concluded that the complex is entirely dissociated in solution and the fluorescence shift observed in the solid state is the result of the interaction in the excited state. The present note describes a new observation which is useful for understanding the mechanism of fluorescence quenching in the hydrocarbons‐TMUA systems.
AGREGATION DES CHLOROPHYLLES IN VITRO‐II. PHOTODECOLORATION DE LA CHLOROPHYLLE a ADSORBEE SUR DES PARTICULES DE LIPOPROTEINES EXTRAITES DU LAIT
Authors: DINANT M. , AGHION J.
Published: January 2008

Abstract— Chlorophyll a (chl a) adsorbed on milk proteins or lipoproteins has absorption maxima at 437 ± 1 nm and 671 ± 1 nm, whatever its concentration. A 750‐nm‐absorbing form appears when (chl/proteins) > 2 × 10‐2 mg chl/mg proteins, in the case of lipoproteins; or 4.5 × 10‐3 mg chl/mg proteins, in the case of proteins. In both cases, the apparent molar extinction coefficient at 671 nm is the same (3 × 104 liter mole‐1 cm‐1) at the highest (chl/proteins) ratio for which no 750 nm absorbancy appears. It is shown that adsorbed chl a undergoes irreversible (in the present conditions) photo‐oxidation by light in the presence of oxygen. The reaction is second order, with similar rate constants for chl a adsorbed to proteins or to lipoproteins.
INTERPRETATION DES MODIFICATIONS SPECTRALES SUBIES PAR LES HYDROCARBURES AROMATIQUES LORS DE LEUR INTERCALEMENT AU SEIN DES ACIDES NUCLEIQUES
Authors: MANTIONE MARIE‐JOSÉ
Published: January 2008

Abstract— This work presents a calculation of the large bathochromic shift observed in the ultraviolet spectrum of aromatic hydrocarbons (such as pyrene and 3,4 benzopyrene) when they are stacked with nucleotides and polynucleotides. For this, an estimation of the increase of molecular polarizability in the excited states is necessary. This increase is responsible for the fact that the stabilization of the stacked hydrocarbon by dispersive interactions with base pairs becomes stronger in the excited state. The calculated increases of stabilization energies are in satisfactory agreement with the observed spectral shifts.
PHOTOREDUCTION OF METHYLENE BLUE BY WATER*
Authors: SOMER GÜLER , GREEN MICHAEL E.
Published: January 2008

Abstract— The photoreduction of methylene blue in acid solution has been studied electrochemically. It has been found that methylene blue photoreduction proceeds in red light, with only water available as reducing agent. Reaction energy considerations require two photons to reduce each methylene blue molecule. A two‐photon mechanism involving a long‐lived dimer intermediate is proposed, and is shown to lead to the observed kinetics, including the dependence of rate on light intensity and methylene blue concentration.
DEACTIVATION OF EXCITED AZO DYE MOLECULES BY ENERGY TRANSFER
Authors: MÖBIUS DIETMAR , DREIZLER GISELA
Published: January 2008

Abstract— Förster energy transfer from an excited azo dye monolayer to a luminescent cyanine dye monolayer was investigated. It is concluded that higher vibronic levels of the excited singlet state are efficiently deactivated by processes other than thermal equilibration.
LOW TEMPERATURE ABSORPTION SPECTRUM STUDIES: LIGHT‐INDUCED PIGMENT CHANGES IN PORPHYRIDIUM CULTURES
Authors: HOARAU J. , LECLERC J. C.
Published: January 2008

Abstract— A single‐beam spectrophotometer with a low‐temperature sample chamber has been built. An automatic mechanical device gives a suitable baseline and allows very reproducible absorption spectra to be obtained. The red alga Porphyridium grown, during a few days, under high‐intensity monochromatic light, showed a decrease in the amount of chlorophyll a forms directly or indirectly excited. Furthermore, a 585 nm absorption band is observed in red algae such as Porphyridium, Rhodymenia and Calliblepharis. This 585 nm band is labile to many damaging agents.
THE SYNERGISTIC ACTION OF ULTRAVIOLET AND X RADIATION ON MUTANTS OF ESCHERICHIA COLI K‐12
Authors: Martignoni Klaus D. , Smith Kendric C.
Published: January 2008

Abstract— Prior UV irradiation increased the X‐ray sensitivity of wild‐type E. coli K‐12. This synergistic effect of combined UV and X irradiation was also observed, but to a reduced extent, in uvrA, uvrB, uvrC, and polA mutants, but was absent in exrA, recA, recB, or recC mutants of E. coli K‐12. Alkaline sucrose gradient studies demonstrated that the wand err gene‐controlled, growth‐medium‐dependent (Type III) repair of X‐ray‐induced DNA single‐strand breaks was inhibited by prior UV irradiation. This inhibition probably explains the synergistic effect of these two radiations on survival.
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.
FLASH PHOTOLYSIS‐ELECTRON SPIN RESONANCE STUDIES OF THE INTERACTION OF PHENAZINE METHOSULFATE WITH REACTION‐CENTER PREPARATIONS FROM THE R‐26 MUTANT OF RHODOPSEUDOMONAS SPHEROIDES*
Authors: Cost Konstantine , Bolton James R.
Published: January 2008

Abstract— Using the technique of flash photolysis‐electron spin resonance, we have shown, by means of a kinetic analysis, that phenazine methosulfate (PMS) interacts with reaction‐center preparations from the blue‐green mutant R26 of Rhodopseudomonas spheroides. At intermediate concentrations of PMS, biphasic decay kinetics of the P870+ ESR signal are observed demonstrating that the PMS radical interacts with reaction centers by a specific binding mechanism. With PMS bound to reaction centers, the P870+ ESR signal decays in ˜ 1 ms; whereas, in unbound reaction centers the decay is ˜ 120 ms. A model is proposed involving the interaction of PMS on the donor side of P870.
DELAYED FLUORESCENCE AND THE REVERSAL OF PRIMARY PHOTOCHEMISTRY IN RHODOPSEUDOMONAS VIRIDIS
Authors: Fleischman Darrell
Published: January 2008

Abstract— Delayed fluorescence from chromatophores of the photosynthetic bacterium Rhodopseudomonas viridis was measured at temperatures below 0°C. A component with a decay half‐time of about 7 ms was found. Its intensity was directly proportional to the number of reaction centers in the P985+·A‐ state. During prolonged illumination it faded as electrons moved forward along the electron transport chain from the primary acceptor, A, (P985+·A‐→P985+·A), and its decay in the dark paralleled the disappearence of the P985+ electron paramagnetic resonance absorption. The data suggest that this component of delayed fluorescence results from a direct reversal of the primary light reaction. While the rate of the P985+middot;A‐→P985·A reaction was almost independent of temperature, delayed fluorescence intensity displayed an apparent activation energy of 0°2 eV. It is concluded that the P985+·A‐→P985·A reaction proceeds by parallel radiative and nonradiative routes. The direct proportionality between delayed fluorescence and the concentration of P985+·A‐ pairs seems to preclude an involvement of triplet‐triplet annihilation or dependence of delayed fluorescence upon the variable prompt fluorescence yield.
PHOTO‐OXIDATION OF N'‐FORMYLKYNURENINE AND TRYPTOPHAN PEPTIDES BY SUNLIGHT OR SIMULATED SUNLIGHT
Authors: Pirie Antoinette , Dilley K. J.
Published: January 2008

Abstract— N'‐Formylkynurenine, a photochemical breakdown product of tryptophan in proteins, was exposed to sunlight or simulated sunlight at neutral pH. N‐Formylanthranilic acid and 4‐hydroxyquinoline were identified in the reaction products. Neither has been previously described as a photo‐oxidation product of tryptophan‐containing compounds. They were not found after photo‐oxidation of glycyltryptophan or tryptophylglycine, although the indole ring was broken in both compounds.
EFFECTS OF BICARBONATE ION ON CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND DELAYED LIGHT EMISSION FROM MAIZE CHLOROPLASTS
Authors: Stemler Alan , Govindjee
Published: January 2008

Abstract— Using high‐intensity actinic light, the chlorophyll a fluorescence transient from HCO‐3‐depleted chloroplasts shows a rapid initial rise (O → I) followed by a slow phase (I → P). In the presence of HCO‐3, the O → I rise is delayed but the I → P phase is much more rapid. Using low‐intensity actinic light, the chlorophyll a fluorescence transient from 3‐(3,4‐dichlorophenyl)‐1,1 dimethylurea (DCMU)‐treated chloroplasts is delayed in the presence of HCO‐3. Bicarbonate increases the amount of delayed light emission from chloroplasts given 10 s illumination with weak blue light (0·4 W/m2). DCMU greatly increases the amount of delayed light seen in the presence of HCO‐3 under these conditions but decreases the amount seen in the absence of HCO‐3. It is suggested that HCO‐3 may somehow form or stabilize, in the dark, a number of reaction centers corresponding to the S1 state in the model of B. Forbush, B. Kok and M. McGloin (Photochem. Photobiol. 14, 307–321, 1971).
DETERMINATION OF INTRINSIC CONSTANTS FOR THE KINETICS OF GROWTH AND DECAY OF FREE RADICALS IN ILLUMINATED KERATIN
Authors: Shatkay Adam
Published: January 2008

Abstract— The growth and the decay of free radicals in illuminated keratin of five samples of wool have been studied by electron paramagnetic resonance. Illumination of the different samples varied from 10‐9 to 10‐7 Einstein cm‐2s‐1. The paramagnetic resonance spectra were measured both during illumination and during the decay of signals in the dark. The curves obtained during illumination gave two typical shapes: one approaching the apparent “saturation value”, and the other passing through a maximum and then decreasing despite continuing illumination. All the above results are discussed in terms of only two prevalent free‐radical species, whose growth and decay are determined for each species by a single intrinsic growth constant, and a single intrinsic decay constant. These four constants allow a reasonable fit for the complete behaviour of all five samples.
THE DIPOLE MOMENT IN THE LOWEST SINGLET π*→π STATE OF INDOLE DETERMINED BY THE OPTICAL STARK EFFECT*
Authors: Chang Chiang‐Tung , Wu Chung‐Yung , Muirhead Alan R. , Lombardi John R.
Published: January 2008

Abstract— A Stark effect is observed in the rotational fine structure of the 0–0 band of the lowest π*π state of indole. This yields a dipole moment change |ΔμA| = 0·14±0·05. D. Evidence is presented which indicates that the sign of ΔμA is positive. An increase of dipole moment on excitation is in agreement with the value (+ 0·06 D) corresponding to the previously calculated orbitals of Song and Kurtin. The direction of the transition moment, calculated from the results of rotational analysis published by Mani and Lombardi, is found to be 26° from the molecular A‐axis.
ULTRAVIOLET‐ENHANCED REACTIVATION OF HERPES VIRUS IN HUMAN TUMOR CELLS
Authors: Lytle C. D. , Benane S. G. , Bockstahler L. E.
Published: January 2008

Abstract—Virus‐host cell interactions may be investigated by study of the enhancement of infectivity of ultraviolet (UV)‐irradiated virus obtained by UV‐irradiating the host cell [ultraviolet reactivation (UVR)]. This phenomenon was studied with Herpes simplex virus and normal (embryonic lung) and malignant (HeLa) human cells. Although the lung cells displayed no UVR, both the HeLa cells and a Sendai‐virus carrier culture of HeLa cells demonstrated UVR capabilities. This UVR persisted at equal or increased levels for at least 24 h. Since the lung cells and HeLa cells have similar host‐cell‐reactivation (HCR) abilities, the differences in UVR suggests that UVR and HCR may operate by different mechanisms.
PRIMARY PHOTOCHEMICAL PROCESSES OF CATIONIC ACRIDINE ORANGE IN AQUEOUS SOLUTION STUDIED BY FLASH PHOTOLYSIS
Authors: Kellmann Arlette
Published: January 2008

Abstract—Photochemical reactions of cationic acridine orange (AO+) in aqueous solution were studied using the flash photolysis technique. Complete conversion to the triplet state was achieved. The triplet dye decays by first‐ and second‐order reactions, which partly regenerate the dye in the ground state and partly produce semi‐oxidized and semi‐reduced acridine orange. These radical species are formed by an electron‐transfer mechanism between two triplet molecules. The radicals recombine rapidly to give the dye in the ground state. An efficient photooxidation reaction is observed in acridine orange solution containing ferric ions. Semi‐oxidized dye is formed in high yield by reaction between the triplet and the oxidant; the semi‐oxidized radicals disappear, yielding permanent photoproducts. Tetra‐methylparaphenylene diamine (TMPD) reacts efficiently with the acridine orange triplet to give the semi‐reduced dye and the semi‐oxidized form of TMPD; this reduction was found to be reversible. Absorption spectra of the transient species were determined and rate constants for the observed reactions measured. The results are compared with results from a previous study of neutral acridine orange.
TRIPLET STATES AND cis‐trans PHOTOISOMERIZATION PROCESSES IN THE SCHIFF BASES OF RETINAL ISOMERS
Authors: Rosenfeld T. , Alchalel A. , Ottolenghi M.
Published: January 2008

Abstract—The triplet states of the n‐butyl‐amine Schiff bases of 11‐cis, 9‐cis, 13‐cis and all‐trans retinal are produced via triplet‐triplet energy transfer. Their absorption spectra, peaking around 435 nm, and their decay kinetics are recorded using pulsed‐laser photolysis. Direct‐excitation (φDISO) and triplet‐sensitized (φTISO) photoisomerization yields, determined using steady irradiation methods, are found to be: φTISO (9‐cis) = 0.06, φTISO (11‐cis) = 045, φTISO (13‐cis) = 008, φTISO (all‐trans) = 0.02‐0.05, φDISO (11‐cis, = (4 ± 1) × 10‐3, φDISO (all‐trans) = (2 ± 1) × 10‐3. The possible role of the triplet state in the isomerization of rhodospin is discussed.
ELECTRON PARAMAGNETIC RESONANCE SIGNAL II IN SPINACH CHLOROPLASTS—I. HIGH RESOLUTION SPECTRA AND MORPHOLOGICAL LOCATION
Authors: Esser Alfred F.
Published: January 2008

Abstract—The electron paramagnetic resonance Signal II of spinach chloroplasts was recorded under high‐resolution conditions. The signal is asymmetric, has five lines of unequal intensity and splitting, a derivative linewidth of 20.0 G, and a g‐value of 2.0051. The latter value varies between 2.0045 and 2.0052 since other signals contribute to the center portion of the spectrum. Signal II is present in dark‐adapted leaves and chloroplasts at a concentration of 50 per cent of the maximum light signal. It is not exhibited by stroma lamellae but is seen in grana thylakoid fractions. The maximum concentration of the material providing Signal II is found in a fraction (40 K) which has a very low Photosystem II activity. The unknown substance giving rise to Signal II may not be required for either Photosystem I or Photosystem II activity. Evidence presented here indicates that Signal II probably is not due to a free, mobile plastosemiquinone or a free, mobile plastochromanoxyl radical.
THE FATE OF PYRIMIDINE DIMERS IN THE DNA OF ULTRAVIOLET‐IRRADIATED CHINESE HAMSTER CELLS
Authors: Meyn Raymond E. , Vizard Douglas L. , Hewitt Roger R. , Humphrey Ronald M.
Published: January 2008

Abstract—As an aid to understanding the relationship between dimer repair and cellular recovery, we have studied dimer removal and replication of dimer‐containing DNA in Chinese hamster ovary (CHO) cells irradiated with ultraviolet light (254 nm). These investigations demonstrated that (1) dimers are not excised as polynucleotides of less than 500,000 mol. wt, (2) fractionation of the ultraviolet dose does not enhance dimer excision, (3) dimer‐containing DNA is replicated in ultraviolet‐irradiated CHO cells, and (4) the dimers are conserved in the replicated DNA. These findings support the proposed mechanism of bypass of photoproducts during DNA replication in mammalian cells.
MICELLAR EFFECTS ON URACIL PHOTODIMERIZATION
Authors: Fendler Janos H. , Bogan Gary
Published: January 2008

Abstract—Initial quantum yields for the formation of all four uracil dimers, anti h, t (I); anti h, h (II); syn h, h (III) and syn h, t (IV), have been quantitatively determined in aqueous degassed and air‐saturated solutions as well as in degassed and air‐saturated solutions of micellar sodium dodecyl sulfate (NaLS) and hexadecyltrimethylammonium bromide (CTAB). In aqueous solutions the order of dimer yields is IV > III > II > I. Percentages of dimer III decreases from 18‐9 per cent in water to 2–7 per cent in micellar CTAB and to 6.0 per cent in micellar NaLS, but those for dimers I and II increase in the micellar solutions.
PHOTOCHEMICAL INACTIVATION OF TRYPSIN*
Authors: Arun  , Grossweiner L. I.
Published: January 2008

Abstract—The quantum yield for inactivation of aqueous trypsin fits the expression φf=Σrfrφ‘r, where fr, is the fraction of incident light absorbed by residues of type r and the φ’r are constants. The values φ‘trp= 0.012, φtyr= 0.005 and φ’eys= 0.10, obtained at pH 3 in the wavelength range 240–290 nm, are attributed to independent events by comparing with quantum yields of the initial photochemical products and permanent residue destruction. The proposed inactivating processes are photoionization of one essential tryptophyl residue, photolysis of one essential cystyl residue, and splitting of an essential cystyl residue induced by light absorption in a nearby tyrosyl residue. The initial photochemical process from pH 3–7 identified by flash photolysis is the ejection of electrons from approximately two tryptophyl residues, leading to the formation of the disulfide bridge electron adduct and the hydrated electron. It is proposed that one photoionized tryptophyl residue is permanently disrupted and the other is restored through a back reaction that leads to a damaged, active enzyme form. An enhanced inactivation quantum yield at flash photolysis light intensities is attributed to a biphotonic process. A model based on one‐photon photoionization of tryptophan from a short‐lived precursor of the fluorescent state and the biphotonic photoionization of tryptophan via the triplet state is consistent with the experimental results.
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.
LOW‐TEMPERATURE FLUORESCENCE SPECTRA OF CHLOROPHYLL a SOLUTIONS
Authors: Kaplanová M. , Vacek K.
Published: January 2008

Abstract Fluorescence and fluorescence polarization spectra of chlorophyll a dissolved in ethanol, n‐propanol, EM (ethanol‐methanol, 4:1) and EPE (ether, n‐pentane, ethanol, 5:5:2) were measured at 77 K. An emission band (‘shoulder’) between the two usual fluorescence bands appears in such spectra of dilute solutions (concentration ˜ 10‐5M) of chlorophyll a (except in EPE). The position, intensity and half‐width of this band were calculated using a computer. The correlation between electronic transitions of chlorophyll a and these emission bands is discussed.
A STUDY OF SOLAR ERYTHEMA RADIATION DOSES*
Authors: Green A. E. S. , Mo T. , Miller J. H.
Published: January 2008

Abstract—Using semi‐empirical analytic formulas for the transmitted and scattered ultraviolet spectral irradiance at the ground (Green, A. E. S., T. Sawada and E. P. Shettle, Photochem. Photobiol. 19, 251–259, 1974), we calculate erythema dose rates and daily erythema doses. Results are illustrated graphically, and for the purpose of photobiological applications are given in terms of approximate analytic forms, with parameters presented in tabular form. The relative erythema data assembled by W. W. Coblentz and R. Stair (U.S. Bureau of Standards J. Res. 12, 13–14, 1934), as fit by an analytic form, is taken as a standard spectrum in our calculations. Other forms of erythema spectra are also compared.
CHEMISTRY OF SINGLET OXYGEN—XVIII. RATES OF REACTION AND QUENCHING OF α‐TOCOPHEROL AND SINGLET OXYGEN*
Authors: Christopher S. , Foote  , Ching Ta‐Yen , Geller George G.
Published: January 2008

Abstract—α‐Tocopherol scavenges singlet oxygen (produced by methylene blue photosensitization in methanol) by a combination of chemical reaction (4.6 times 107M‐1s‐1) and quenching (6.2 times 108M‐1 s‐1). The total rate of scavenging (6.7 times 108 M‐1s‐1) makes it an effective protective agent against photooxidation mediated by singlet oxygen.
STUDY OF THE EFFECTS OF ULTRAVIOLET LIGHT ON BIOMEMBRANES—IV. THE EFFECT OF OXYGEN ON UV‐INDUCED HEMOLYSIS AND LIPID PHOTOPEROXIDATION IN RAT ERYTHROCYTES AND LIPOSOMES
Authors: Roshchupkin D. I. , Pelenitsyn A. B. , Potapenko A. Ya. , Talitsky V. V. , Vladimirov Yu. A.
Published: January 2008

Abstract— Hemolysis induced by irradiation with ultraviolet (UV) light at 254 nm showed a pronounced oxygen effect: under irradiation in vacuum, the rate of hemolysis was decreased by an order of magnitude. Irradiation at 254 nm in air but not under vacuum caused the peroxidation of erythrocyte membrane lipids. These results suggest that membrane lipid photoperoxidation is one of the causative factors of UV hemolysis. Irradiation at different wavelengths showed that UV‐induced lipid photoperoxidation in erythrocyte membranes developed while the antioxidant α‐tocopherol was directly photooxidized. It is shown that the process of lipid photolysis in erythrocyte membranes involves sensitization, possibly by protoporphyrin, whose presence in liposomes accelerates the photoperoxidation at 254 and 365 nm of unsaturated fatty acid residues in lecithin. Possible mechanisms of photochemical damage to erythrocyte membranes are discussed.
pH DEPENDENCE OF SINGLET OXYGEN PRODUCTION IN AQUEOUS SOLUTIONS USING THIAZINE DYES AS PHOTOSENSITIZERS
Authors: Bonneau R. , Pottier R. , Bagno O. , Joussot‐Dubien J.
Published: January 2008

Abstract— The production of singlet oxygen by thiazine dye photosensitization, as measured by the rate of photooxidation of tryptophan, was found to be very sensitive to changes of pH in the range 5–9. For methylene blue in aerated solutions, the production of 1O2* is approximately five times more efficient in basic than in acidic medium. This was shown to be related to the pK's of the triplet dyes, by evaluating the yields of 1O2* from the lifetimes and the quenching rate constants for the two ionic species of sensitizer triplets measured by laser flash photolysis. Changes in the quenching rate constants of the thiazine triplet states can be correlated with the triplet energies.
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 OF VISIBLE LIGHT ON ENZYMES IN CELL ENVELOPES OF MICROCOCCUS ROSEUS
Authors: Ascenzi J. M. , Cooney J. J.
Published: January 2008

Abstract— Envelopes were isolated from the carotenogenic bacterium Micrococcus roseus, which is subject to photodynamic killing in the presence of a photosensitizing dye but not in the absence of such a dye. Envelope preparations contained 88 per cent of the total cellular carotenoids, 20% of the NADH oxidase, 100 per cent of the ATPase and 30% of the succinic dehydrogenase activity. NADH oxidase activity in envelopes was stimulated 2–5‐fold by light in the presence of dye; this was followed by inactivation. In the presence of dye, ATPase was inactivated by light and 25 per cent of the succinic dehydrogenase activity was lost. In the absence of dye, responses were extended over a longer period of time, but similar patterns were observed for the three enzymes, indicating that envelopes contain an endogenous photosensitizer(s). Carotenoid‐deficient cells were obtained after growth in medium containing diphenylamine. But all three enzymes showed evidence of instability in envelope preparations, indicating that diphenylamine affects membrane structure in addition to inhibiting synthesis of colored carotenoids.
EFFECTS OF 8‐METHOXYPSORALEN‐INDUCED PHOTOTOXIC EFFECTS ON MAMMALIAN EPIDERMAL MACROMOLECULE SYNTHESIS IN VIVO
Authors: Epstein John H. , Fukuyama Kimie
Published: January 2008

Abstract— The influence of 8‐methoxypsoralen (8‐MOP) and ultraviolet (UVA; 315–400 nm) radiation‐induced phototoxic responses on DNA, RNA and protein synthesis and the DNA repair phenomenon were investigated utilizing the hairless mouse epidermis in vivo. The radioactive tracers TdR‐3H, cytidine‐3H and histidine‐3H were used to examine changes in these macromolecules. Using these techniques, we found that the 8‐MOP‐UVA phototoxic injury inhibited premitotic semiconservative DNA synthesis in the germanitive layer of the epidermis within the first few hours post‐irradiation. Recovery occurred by 24 h, followed by a progressive acceleration of this function over the next 7 days. No depression in RNA or protein formation was noted through 36 h. By 48 h the cells in the upper 1/2 to 1/3 of the epidermis lost their normal appearance and discontinued synthesizing these macromolecules. At 72 h RNA and protein synthesis was again active throughout the epidermis and the apparently dead cells had desquamated. At this time the epidermis was notably acanthotic and the epidermal cells were markedly enlarged. Examination for the dark repair response revealed no evidence of unscheduled DNA synthesis following irradiation indicating that the excision repair process was not demonstrable within the first 15min after the phototoxic injury. These responses differ in a number of parameters from the phototoxic reactions induced by UV rays shorter than 320 nm.
PHOTOINDUCED LUMINESCENCE AND EPR SIGNALS OF POLYPHENOL AND QUINONE POLYMERS
Authors: Slawinska D. , Slawinski J. , Sarna T.
Published: January 2008

Abstract— Aqueous basic solutions, pH 9.0 of humic acids and melanin‐like, synthetic polymers, obtained with adrenochrome, hydroquinone and purpurogallin, were illuminated with visible light under N2 or O2 atmospheres. It has been found that light enhances a singlet electron‐paramagnetic‐resonance (EPR) signal of polymers both under N2 and O2, and induces ultra‐weak luminescence in the presence of O2. Degradative oxidation of polymers, accelerated by light, leads to a decrease of EPR signal intensity and generates weak chemiluminescence.
SINGLET ENERGY TRANSFER BETWEEN AROMATIC AMINO ACIDS AND NUCLEIC ACID BASES. THEORETICAL CALCULATIONS
Authors: Montenay‐Garestier T.
Published: January 2008

Abstract— Critical Forster distances for excitation energy transfer at the singlet level between the tyrosyl or tryptophyl residues of proteins and nucleic acid bases have been calculated. Efficient singlet energy transfer can be expected from tyrosine to nucleic acid bases both at room temperature (10 <R0 < 17 A) and at low temperature (20 < R0 < 23 Å). At low temperature nucleic acid bases should be able to transfer their singlet excitation energy to the indole ring of tryptophan with a reasonable probability (9 < R0 < 15 A).
PHOTOCHEMISTRY OF REDUCED LUMIFLAVIN IN ITS ACIDIC FORM
Authors: Lasser Nehama , Levanon Haim , Feitelson Jehuda
Published: January 2008

Abstract— The photooxidation of reduced lumiflavin in its acidic form, LfH3+, takes place in two consecutive steps. Upon illumination of LfH3+ in its absorption band at 313 nm the semiquinone, LfH3+, is formed. Two LfH2+ ions are consumed for every LfH2+ formed. Illumination of the semiquinone in its absorption band at 495 nm causes further oxidation so that the oxidized LfH+ ion is formed. In this reaction one LfH3+ ion is photolyzed for every LfH+ formed. In addition, a hydrogen atom is released in the photooxidation of LfH2+. Mechanisms for the two photoreactions are proposed.