bluuebunny/crossref_metadata_2025 huggingface dataset:
EMISSION SPECTRA FROM SYNTHETIC POLYNUCLEOTIDES AND DEOXYRIBONUCLEIC ACID IN AQUEOUS SOLUTIONS†
Authors: KLEINWÄCHTER V. , DROBNIK J. , AUGENSTEIN L.
Published: January 2008

A study has been made of the emission spectra at 77°K from poly A, poly U, poly C, their complexes, and from native and heat‐denatured DNA in buffered aqueous solutions containing 0·25 per cent glucose: no emission was observed from these polynucleotides at room temperature. The spectra differed from those obtained in the polyalcoholic glasses used by other workers. The principal differences between the emission spectra of poly A and adenosine at pH 7 in a water‐glucose mixture were: (a) a decrease in both P/F and the overall intensity in poly A; (b) absence of the structure normally found in adenosine phosphorescence; and (c) appearance of a new short‐lived component in the phosphorescence decay. Further changes in the emission characteristics (e.g. the increase of P/F, the proportional increase of the short‐lived component in the phosphorescence decay) from poly A were observed at pH 5. These can not be explained solely by protonization of adenosine residues, but rather appear to depend upon exciton interactions of the most intense π–π* transition in double‐stranded poly A. and perturbation of the lowest‐lying emitting band. When poly A or poly C is complexed with poly U or poly I the luminescence intensity decreases in two‐strand complexes and is completely quenched in poly (A + 2U), poly (A+2I) and poly (C++I); no emission was observed from either, single‐strand poly I or poly U. Identical emission patterns were obtained from native and heat‐denatured samples of DNA. The comparison of polynucleotide emission spectra in the water‐glucose medium with those obtained from polyalcoholic glasses leads to the conclusion that the emission spectra depend most critically upon the relative proportions of base‐solvent and base‐base interactions in each environment: the possible importance of proton tunneling and/or triplet‐triplet transfer mechanisms is briefly discussed.
ETUDE PAR RESONANCE PARAMAGNETIQUE ELECTRONIQUE ET PAR SPECTROPHOTOMETRIE D'ABSORPTION DES PROCESSUS PRIMAIRES DANS LA PHOTOCHIMIE DE SOLUTIONS AQUEUSES CONGELEES A 77°K D'ACIDES AMINES AROMATIQUES ET DE POLYPEPTIDES*
Authors: SANTUS R. , HÉLÈNE C. , PTAK M.
Published: January 2008

Abstract— Neutral, acidic or basic frozen aqueous solutions of aromatic amino acids undergo photoionisation under u.v. irradiation, at 77°K. In neutral or basic solutions, photo‐ejected electrons are trapped in the solvent matrix and exhibit a characteristic absorption band in the visible region. In acidic solutions electrons are trapped by protons and ESR signal spectrum of hydrogen atoms may be observed. Hydrogen atoms are also produced in low yield in neutral or basic frozen aqueous solutions, u.v. irradiated at 77°K. In basic media the ESR spectrum of 0‐ radical ions is observed. Kinetic studies as a function of light intensity show that photoionisation takes place after absorption of a second photon by the phosphorescent molecule in its lowest triplet state. Recombination of trapped electrons in neutral or basic solutions may be induced using secondary excitation with visible light. In all instances we could record the absorption spectrum of photolytic products of aromatic amino acids and polypeptides which are u.v. irradiated at 77°K.
PHOTOELECTRONIC EFFECTS IN ORGANIC MATERIALS‐I. CHLOROPHYLL‐CHLORANIL LAMELLAR SYSTEMS
Authors: REUCROFT P. J. , SIMPSON W. H.
Published: January 2008

Abstract— Photoinduced electron transfer in lamellar composites of chlorophyll a and p‐chloranil has been shown to lead to a voltaic effect. The photovoltage spectral response peaks at the absorption peak of chlorophyll in the red region, indicating that chlorophyll itself is the light absorbing species. Maximum power output of the system is approximately 10‐15 W. A dependence of photovoltage on the square of the incident intensity suggests a bi‐excitonic mechanism for charge separation.
COMMON FEATURES OF PHOTOPERIODISM IN PLANTS AND ANIMALS*
Authors: BÜNNlNG ERWIN
Published: January 2008

Abstract— Light break experiments show the role of the circadian clock in photoperiodic timemeasurement. Additional evidence comes from experiments which show the close relation between temperature‐ or light‐induced phase shifts in cycles of photoperiodic responsiveness and simultaneous phase shifts of other processes which are under control of the circadian clock. Using the circadian clock is a common feature of photoperiodism in plants and animals. This clock controls quantitative and qualitative changes in the responsiveness to light. However, quite different pigment systems may be involved, resulting in different action spectra for light break effects. In many cases, these action spectra differ also from the action spectra for phase shifts in the circadian clock.
LUMINESCENCE OF TAUTOMERIC FORMS OF THYMINE MONOANIONS
Authors: BERENS K. , WIERZCHOWSKI K. L.
Published: January 2008

Abstract— The fluorescence and phosphorescence emission and excitation spectra of monoan‐ions of thymine. I‐methyl‐thymine and 3‐methylthymine (in alkaline solutions, 10‐2N NaOH) at 300° and 77°K were measured. It was shown, that at 300°K only 3‐HT‐ tautomeric thymine monoanion fluoresces; at 77°K emissions of both monoanionic species contribute to the observed luminescence spectrum.
X‐RAY‐ AND U.V.‐INDUCED EXCITATION OF ADENINE, THYMINE AND THE RELATED NUCLEOSIDES AND NUCLEOTIDES IN SOLUTION AT 77°K*
Authors: HøNNÅS P. I. , STEEN H. B.
Published: January 2008

Abstract— The light emitted by adenine and thymine and the related nucleosides and nucleotides in ethylene glycol/water glass during irradiation at 77°K with X‐rays and 270 nm U.V. light has been studied. It was found that the same radiative levels were excited by both types of radiation. However, the phosphorescence to fluorescence ratios observed with X‐rays were considerably enhanced relative to those obtained with U.V. light. This observation was taken to mean that a major fraction of the excitation results from ion recombination, although direct excitation of the triplet manifold as well as intersystem crossing between upper excited levels may have contributed to the enhancement as well. The yields of the X‐ray‐induced excitation of radiative levels. which were calculated by combining the yields of X‐ray‐induced emission and the quantum yields observed with u.v.‐excitation, corresponded to: G≥ 4.0 excitations per 100 eV of dose absorbed in the solute for adenine and G≥ 1.8 for thymine. The excitation yields obtained for the nucleosides and nucleotides were somewhat smaller than those observed for the corresponding bases. It was inferred from the yields that a substantial fraction of the dose absorbed in the ribose of the nucleosides was transferred to the radiative levels of the constituent bases.
MICROSPECTROPHOTOMETRIC STUDIES ON THE PIGMENTSIN VIVOOF SINGLE ALGAL CELLS‐I. PIGMENTS OFCHLORELLA PYRENOIDOSA
Authors: THOMAS JOSEPH , PHONDKE G. P. , TATAKE V. G. , GOPAL‐AYENGAR A. R.
Published: January 2008

Abstract—The pigmentsin vivoof single cells ofChlorella pyrenoidosawere studied by the microspectrophotometric technique. An accessory recording the first derivative of absorption was used to obtain fine resolution and enhanced accuracy. The results suggest that there are several long‐wavelength components of Chla in vivo.In addition, there seem to be four short‐wave forms of Chla.It is also likely that Chlbexistsin vivoin two different forms. The existence of all these forms was demonstrated at room temperature.
OYGEN DEPENDENCE AND REPAIR OF LETHAL EFFECTS OF NEAR ULTRAVIOLET AND VISIBLE LIGHT*
Authors: WEBB ROBERT B. , LORENZ JOHN R.
Published: January 2008

Abstract— –Lethality in a repairable strain (WP2) and an excision repair deficient strain (WP2hcr) of Escherichia coli was studied at wavelengths of 254, 313, 365, and 390–750 nm. Survival curves were empirically fitted to the expression S= 1 ‐ (1‐e‐kl)“, where S is the fraction surviving, D is the incident dose in ergs mm‐2, k is the inactivation constant in units of (erg mm‐2)‐1 and n is the ‘shoulder constant’. The repairable sector (k(hcr‐)–k(hcr‐)lk(hcr‐), a conservative estimate of the repair capability of E. coli WP2, was 0.91 at 254 nm, 0.92 at 313 nm, 0.60 at 365 nm, and 0.13 at 390–750 nm. Although there was no oxygen enhancement of inactivation at 254 nm and 313 nm, a strong enhancement was identified at 365 nm and 390–750 nm. These results suggest that oxygen‐dependent damage induced by near u.v. (365 nm) can be partially repaired by the excision‐repair system in E. coli.
HIGHER DERIVATIVE ANALYSIS OF COMPLEX ABSORPTION SPECTRA
Authors: BUTLER W. L. , HOPKINS D. W.
Published: January 2008

Abstract— –A small computer on line with a single‐beam spectrophotometer was used to obtain absorption spectra and higher derivatives (up to the fourth) of the absorption spectra. The spectral resolution was markedly enhanced in the higher derivative curves. The computer was also used to synthesize absorption spectra from Gaussian, Lorentzian and mixed Gaussian‐Lorentzian band shapes in order to explore the higher derivative analysis of completely defined spectra.
CHLOROPHYLL a AND CAROTENOID AGGREGATES AND ENERGY MIGRATION IN MONOLAYERS AND THIN FILMS
Authors: SINESHCHEKOV V. A. , LITVIN F. F. , DAS M.
Published: January 2008

Abstract— The spectra of absorption, fluorescence and excitation of monolayers and thin films containing chlorophyll a together with a carotenoid (cis‐β‐carotene, trans‐β‐carotene, fucoxanthin, or zeaxanthin), were measured at — 196°C. The concentration ratios used, (Chl)/(Car), were 6:1, 4:1, 3:1, 2:1, 1:1 and 1:3, and the area densities, 3·70, 2·55, 1·76, 0·71, 0·37 and 0·17 nm2/pigment molecule.

In dilute monolayers, (3·70 nm2/molecule), with a constant concentration ratio (Chl)/(Car) = 3:1, evidence of three β‐carotene forms, with absorption bands at 460, 500 and 520 nm (C460, C500 and C520), and of a chlorophyll a form with an absorption band at 669–672 (Chl669–672) was found. On increasing the density to 0·2–0·3 nm2/molecule, a conversion of C460 and C520 into C500, was observed, and several more additional (probably more strongly aggregated) chlorophyll a forms appeared, with absorption bands at 672–733 nm. With excess carotene [(Chi)/(Car) = 1:3] the forms C460, C500, C520 and Chl669–672 were present even in the most dense films (0·2–0·3 nm2/molecule). The same was found with other carotenoids: if one of the pigments was in excess, aggregated forms of the other tended to disappear.

In the transfer of energy from carotenoids to chlorophyll a, C500 was found to be the main donor. In layers with a concentration ratio (Chl)/(Car) = 3:1, the efficiency of transfer was less than 10 per cent at the lowest density used (3·70 nm2/molecule); it increased to 50 per cent, as the density was increased to 0·20 nm2/molecule. When the relative concentration of the carotenoid was increased to (Chl)/(Car) = 1:1, the efficiency of energy transfer dropped to 25 per cent even at 0·20 nm2/molecule. It seems that the efficiency of energy transfer between carotene molecules (prior to its transfer to chlorophyll a) is low, and effective transfer occurs only between β‐carotene and immediately adjacent chlorophyll a molecules.
ON THE MECHANISM OF QUENCHING OF SINGLET OXYGEN BY AMINES‐III. EVIDENCE FOR A CHARGE‐TRANSFER‐LIKE COMPLEX
Authors: YOUNG ROBERT H. , MARTIN R. L. , FERIOZI D. , BREWER D. , KAYSER R.
Published: January 2008

Abstract— A series of amines were found to quench singlet oxygen in the order tertiary > secondary > primary, with a reasonable correlation between the log of their rate constant of quenching and their ionization potential. In addition, a Hammett rho plot gave a rho value of ‐ 1.39 for the quenching of singlet oxygen by a series of substituted N, N‐dimethylanilines, in good agreement with the results obtained by a different method. It was found that some of the amines (anilines) quenched the triplet state of the dye‐sensitizer (Rose Bengal) used for the production of singlet oxygen. Corrections in the results were made in the calculations of rates of quenching of singlet oxygen to allow for the triplet‐state quenching. No extensive quenching of the singlet state of the dye was observed at the concentrations of the amines necessary for singlet‐oxygen quenching. In one case (N, N, N′, N′‐tetramethylphenylenediamine) there was no observable chemical reaction between singlet oxygen and the amine. It was concluded that singlet oxygen undergoes physical quenching by the amines via partial charge‐transfer intermediates.
ULTRAVIOLET IRRADIATION OF NUCLEIC ACIDS COMPLEXED WITH HEAVY ATOMS—III. INFLUENCE OF Ag + AND Hg 2+ ON THE SENSITIVITY OF PHAGE AND OF TRANSFORMING DNA TO ULTRAVIOLET RADIATION
Authors: Rahn R. O. , Setlow J. K. , Landry L. C.
Published: January 2008

Abstract— We have studied the influence of the heavy metal ions Ag+ and Hg2+ on the photoinactivation and photodimerization of transforming DNA and of bacteriophage. The rate of inactivation of Haemophilus influenzae transforming DNA by ultraviolet (UV) radiation was enhanced by a factor of 30 when it was complexed with Ag+. This enhancement was correlated with a comparable increase in the rate of thymine dimerization. In contrast, mercuric ions led to a reduction in the rates of both inactivation and dimerization. When we examined the effects of these metal ions on the photobiology of bacteriophage, we again found that Ag+ enhanced and Hg2+ reduced the rate of ultraviolet inactivation. These results demonstrate that heavy metals may be useful tools for studying the photochemistry and photobiology of nucleic acids.
ENERGY TRANSFER BETWEEN NUCLEIC ACID BASES AND TRYPTOPHAN IN AGGREGATES AND IN OLIGOPEPTIDE‐NUCLEIC ACID COMPLEXES
Authors: Helene Claude
Published: January 2008

Abstract— Interactions and energy transfer processes between nucleic acid bases and tryptophan have been investigated in several Systems: mixed aggregates of nucleosides and tryptophan in frozen aqueous solutions; and poly‐rA and DNA complexes with oligopeptides containing lysyl and tryptophyl residues. Previous studies (Montenay‐Garestier, Th. and C. Hélène, 1971, Biochemistry10, 300–306) had shown that electron donor‐acceptor interactions in stacked complexes of tryptophan and nucleic acid bases led to the appearance of a new fluorescence at longer wavelengths with a low quantum yield. It is shown here that triplet‐triplet energy transfer can take place from bases to tryptophan in mixed aggregates at low [tryptophan]/[base] ratios and in oligopeptide‐poly‐rA (or DNA) complexes at low [oligopeptide]/[phosphate] ratios. Also the singlet excitation energy of bases can be transferred to base – tryptophan complexes. These results are discussed with respect to the structure of the complexes and to the involvement of energy transfer in nucleic acid – protein photochemistry.

Les transferts de l'énergie d'excitation résultant des interactions des bases des acides nucléiques avec le tryptophane ont étéétudiés dans divers systèmes: agrégats mixtes formés dans les solutions aqueuses congelées de nucléosides et de tryptophane; complexes du poly‐rA et du DNA avec des oligopeptides contenant des résidus lysine et tryptophane.

Des études antérieures (Montenay‐Garestier, Th. et C. Hélène, 1971, Biochemistry10, 300–306) ont montré que le tryptophane et les bases des acides nucléiques forment des complexes donneur‐accepteur d'électron, caractérisés par un spectre de fluorescence à plus grandes longueurs d'onde que les spectres des deux composants. L'énergie d'excitation des bases au niveau singulet peut être transférée vers ces complexes.

Dans les agrégats, quand le rapport des concentrations en tryptophane et en adénosine est faible (inférieur à 0.2) un transfert d'.énergie est observé au niveau triplet de l'adénosine vers le tryptophane. L'énergie d'excitation est délocalisée au niveau triplet dans les agrégats d'dénosine sur environ 200 molécules. Un transfert d'énergie du même type est observé dans les complexes du poly‐rA (ou du DNA) avec des oligopeptides contenant le tryptophane.

L'énsemble des résultats obtenus est en accord avec la structure des complexes formés, déterminée par résonance magnétique nucléaire. Le rôle éventuel des transferts d'énergie des bases vers le tryptophane dans la photochimie des complexes protéines–acides nucléiques est discuté.
APPEARANCE AND DEVELOPMENT OF PHOTOSYNTHETIC ACTIVITIES IN WHEAT ETIOPLASTS GREENED UNDER CONTINUOUS OR INTERMITTENT LIGHT—EVIDENCE FOR WATER‐SIDE PHOTOSYSTEM II DEFICIENCY AFTER GREENING UNDER INTERMITTENT LIGHT*
Authors: Remy RENÉ
Published: January 2008

Abstract— Etiolated wheat seedlings are greened under continuous or intermittent light. Under continuous light the onset of photosystem II (PS II) activity appears after 4 h of illumination. Under intermittent light (1 ms flashes alternating with 15 min dark periods), PS II activity cannot be detected after 300–400 flashes, although the pigment composition and structural development of these plastids are similar to those observed after 4 h of continuous light. However, the appearance of PS II activity in isolated plastids can be observed in two different ways: (1) in vivo by exposing the seedlings to a short period of continuous light after the intermittent light; or (2) in vitro by addition to the isolated plastids of an electron donor for PS II, such as diphenylcarbazide. It is concluded that the intermittent light induces development of the electron transport chain from PS II to PS I, but that a deficiency occurs on the water‐side of PS II.
BIPHOTONIC PROCESSES IN PROTEINS: COMPARATIVE STUDIES OF DELAYED FLUORESCENCE AND ISOTHERMAL OR OPTICALLY STIMULATED RECOMBINATION LUMINESCENCE
Authors: Bazin M. , Aubailly M. , Santus R.
Published: January 2008

Abstract—The properties of delayed fluorescence (DF) of proteins are studied in parallel with their properties of recombination luminescence, produced after ultraviolet excitation and photoionization of chromophoric residues at low temperature, in water‐ethylene glycol glasses. It is shown that the DF emission of proteins, originating from tryptophan residues, is produced via triplet‐triplet absorption processes, photoionization of tryptophan residues, and recombination of the charged species. Electron scavengers that reduce the DF yield act differently upon the DF emission and the recombination luminescence as a consequence of the protein structure. Influence of energy transfer on the protein DF yield is also emphasized.
LASER PHOTOLYSIS OF RETINAL AND ITS PROTONATED AND UNPROTONATED n‐BUTYLAMINE SCHIFF BASE
Authors: Fisher Michael M. , Weiss Karl
Published: January 2008

Abstract—The pulsed ruby laser (347 nm) flash photolysis technique has been used to measure the triplet‐triplet absorption spectra and triplet lifetimes of trans ‐retinal, N‐frans‐retinylidene‐n ‐butylamine (NRBA), and protonated NRBA (NRBAH+) at room temperature. In methylcyclohexane solution, the triplet lifetimes are in the range 10–20 μs and decrease in the order NRBAH+ > NRBA > trans ‐retinal. Intersy stem‐crossing efficiencies (φISC) were determined by a comparison technique using anthracene and 1,2‐benzanthracene as reference compounds. For trans ‐retinal, φISC is 0–50 pM 0–05 in methylcyclohexane and 0–08 in methanol, which confirms that earlier values of 0–11 and 0–017 in these solvents are in error. For NRBA and NRBAH+ in methylcyclohexane, ΦISC values are 0008 and < 0–001, respectively. Evidence is presented for a significant solvent effect in the isomerization of retinal via the triplet state, and that cisφtrans isomerization occurs from the triplet state of NRBAH+. The relation between the intersystem‐crossing properties of model compounds and the photochemistry of rhodopsin is discussed.
PHOTOCHEMISTRY OF HIGH MOLECULAR WEIGHT PHYTOCHROME IN VITRO*
Authors: Pratt Lee H.
Published: January 2008

Abstract— –Photochemical properties of phytochrome have been reexamined with preparations of high molecular weight chromoproteins from etiolated oat (Avena sativa L., cv. Garry), rye (Secale cereale L., cv. Balbo) and pea (Pisum sativum L., cv. Alaska) shoots. The proportion of the total phytochrome pool in such preparations present as the far‐red‐absorbing form (Pfr) at photoequilibrium in red light is 0–75. The ratio of the quantum yields for the phototransformation of the red‐absorbing form (Pr) to Pfr and of Pfr to Pr is 1‐0. The absolute quantum yield for these two photoreactions is 017.
ON THE PHOTOCHEMISTRY OF X‐RAY PRODUCED RADICALS TRAPPED IN FROZEN ETHANOL MATRICES
Authors: Moan Johan
Published: January 2008

Abstract— Ethanol and ethanol‐water matrices were exposed to X‐rays at 77K and the photochemistry and paths of radical conversion were investigated by EPR methods. The main X‐ray induced radical, CH3?HOH, is probably photoionized by 254 nm light. The following radicals are produced during prolonged UV‐irradiation of CH3?HOH radicals: ?H3, ?HO, H and 2 types of radicals giving singlet EPR spectra. One of these radicals (d) is bleachable with 580 nm light, ?H3 and ?H3?HOH being formed during the bleaching, the other one (e) is unbleachable and the most stable radical in the matrix during annealing. The CH3 radicals decay at 77 K (τ? 10 min) and produce CH3‐CHOH radicals and the unbleachable radical (e). Stable H‐atom signals were seen in X‐irradiated ethanol‐water mixtures (volume ratio 2:1) at 77 K. The H‐atom signals increased during photobleaching of the trapped electrons in the matrix and during UV‐photolysis of CH3CHOH radicals.
SYNERGISTIC KILLING EFFECT IN PRE‐UV‐IRRADIATED MICROCOCCUS RADIOPHILUS
Authors: Lewis Norman F. , Shah Anjani R. , Kumta Umesh S.
Published: January 2008

Abstract— Both the UV‐ and y‐radiation survival curves of Micrococcus radiophilus are distinguished by large shoulders. However, a combination radiation treatment results in an enhanced killing effect. Pre‐UV treatment is found to give a synergistic kill as compared to an additive kill when the sequence of radiation treatments is reversed.
REC A +‐DEPENDENT SYNERGISM BETWEEN 365 NM AND IONIZING RADIATION IN LOG‐PHASE ESCHERICHIA COLI: A MODEL FOR OXYGEN‐DEPENDENT NEAR‐UV INACTIVATION BY DISRUPTION OF DNA REPAIR
Authors: Tyrrell Rex M.
Published: January 2008

Abstract—The oxygen dependence of 365 nm inactivation of colony‐forming ability of Escherichia coli has been investigated in two series of DNA repair‐deficient K12 mutants grown to mid‐exponential phase. All strains except a uvr A rec A double mutant are more sensitive to inactivation under O2 and show a lower threshold dose. The inactivation of photoreactivating enzyme in a crude cell extract and DNA repair disruption are both reduced when irradiation is carried out under nitrogen. The rec A gene‐dependent synergism between 365 nm and ionising radiation is reversible if cells are incubated in full growth medium before ionising radiation treatment. In a wildtype strain, incubation for 2.5 h in full growth medium after 106 J m‐2 365 nm radiation changes a sensitised response to a protection from ionising radiation. Protection is not seen at 1.5 times 106 J m‐2. A tentative model for near UV lethality in logarithmic phase cells is suggested which proposes two classes of lesions. One requires oxygen for it's induction, is rapidly fixed as a lethal event as a result of repair disruption, and is primarily responsible for cell death after aerobic 365 nm irradiation. The other lesion, possibly pyrimidine dimers, may lead to cell death under anaerobic conditions.
BIOLUMINESCENCE OF THE AUSTRALIAN GLOW‐WORM, ARACHNOCAMPA RICHARDSAE HARRISON
Authors: Lee John
Published: January 2008

Abstract— Stable dry powders of the light organ of the glow‐worm, Arachnocampa richardsae (Diptera) have been prepared and although the amounts of material are extremely limited, a semi‐quantitative description of the bioluminescence reaction can be given. The in vivo and in vitro bioluminescence spectra are the same, maximum 488 nm (corrected) and the shape of the in vitro emission spectrum is not influenced by pH (5.9–8.5). Light is produced by addition of buffer (optimum pH 7) to the powder, but is stimulated several fold if the buffer contains adenosine 5'‐triphosphate (ATP), about 0.3 mM being required for half maximum stimulation. A number of other high‐energy phosphates do not stimulate. Ethylenediaminetetraacetate quenches the ATP stimulation implicating a Mg2+ requirement, but not ethylene‐bis(oxyethylene‐nitrilo)‐tetraacetate which chelates Ca2+ but not Mg2+. Inorganic pyrophosphate (2 mM) also quenches if added with the ATP but in contrast to the firefly (Coleoptera) reaction, does not stimulate the light emission if added post‐ATP. The decay of the ATP‐stimulated glow‐worm bioluminescence is first‐order unlike the strongly product inhibited firefly kinetics. Oxygen is required for both in vivo and in vitro bioluminescence. A glow‐worm can emit more than 1015 photons in its lifetime but at any one time, appears to possess only about 10% of this total capacity.
A NEW FACET IN RHODOPSIN PHOTOCHEMISTRY
Authors: Meer K. van der , Mulder J. J. C. , Lugtenburg J.
Published: January 2008

Abstract— A structure is proposed for the prosthetic group of the visual pigments rhodopsin, prelumirhodopsin (bathorhodopsin) and lumirhodopsin. The intrinsic photochemical step in this model is tautomerization of the prosthetic group of rhodopsin to a hexaeneamine retrotautomer with an exomethylene group for prelumirhodopsin. Based on the proposed structures, molecular orbital calculations were carried out; the absorption maxima calculated snowed the same trends as the Λmax values observed. An exact fit was not obtained because many interactions had to be neglected. Essential information of the laser Raman resonance spectrum of prelumirhodopsin can be interpreted based on the structures proposed by our model.

The model elucidates why some retinal derivates can and others cannot form visual pigments with opsin and visual pigments having vastly differing absorption maxima yet employ the same mechanism for their photoreaction.
INTERACTION OF RESTORATION PROCESSES IN UV IRRADIATEDESCHERICHIA COLZCELLS
Authors: Sedliakova M. , Brozmanova J. , Masek F. , Slezarikova V.
Published: January 2008

Abstract—An attempt was performed to estimate survival and course of DNA synthesis inEscherichia coliB/rhcr'andhcr‐cells in relation to the amount of unexcised dimers.

In exponential growinghcr+cells irradiated with 30 Jm‐2, dimers were almost completely excised and survival of cells was equal to about 3%. In thehcr+cells prestarved for amino acid and thymine and irradiated by the same fluence, survival of cells was almost equal while two thirds of dimers remained unexcised and could be detected in the hybrid DNA consisting of parental and daughter chains. In exponentially growinghcr+‐cells irradiated with 20Jm‐, the same amount of dimers was produced which remained unexcised in the prestarvedhcr+cells. However, their survival was equal to about 0.02%.

Despite the great differences in dimer contents, about one third of DNA was replicated after UV in both exponentially growing and prestarvedhcr+cells producing well defined HL‐hybrid peak, and the newly synthesized DNA was normal‐sized. Inhcr+cells which contained approximately the same amount of dimers as inhcr+prestarved cells, the amount of replicated DNA was too low to form a detectable density labelled hybrid peak, and the newly synthesized DNA was in short pieces.

Thus, whenhcr+andhcr+‐cells contain the same number of residual dimers, they have different levels of tolerance to these dimers.
ANION AND SOLVENT EFFECTS ON THE RATE OF REDUCTION OF TRIPLET EXCITED THIAZINE DYES BY FERROUS IONS
Authors: Wildes P. D. , Lichtin N. N. , Hoffman M. Z. , Andrews L. , Linschitz H.
Published: January 2008

Abstract— The lifetimes of the triplet excited states of thionine and methylene blue were measured in aqueous and 50 v/v% aqueous acetonitrile solutions acidified with 0.01 N sulfuric or trifluoromethyl‐sulfonic acid. The rate constants for reaction of the triplet excited dyes with ferrous ions were measured in the same solutions. The triplet lifetimes in the absence of added quenchers were insensitive to a change in acid from trifluoromethylsulfonic to sulfuric or to a change in solvent from water to 50v/v% aqueous acetonitrile (τ for triplet thionine ˜7.5 μs, τ for triplet methylene blue ˜4.5 μs). In contrast, the rate constant for reaction of the triplet dyes with ferrous ions increased by nearly a factor of 10 with a change in acid from trifluoromethylsulfonic to sulfuric. In solutions containing sulfate ions this reaction rate constant increased with increasing sulfate concentration and with a change in solvent from water to 50 v/v% aqueous acetonitrile. The results are discussed in terms of the possibility of association of the positively charged reactive ions with sulfate anions. Quenching of the triplet excited dyes by ferric ions or by ground state dye molecules was shown to be negligible at the concentration used for the ferrous ion quenching study.
A PRELIMINARY INVESTIGATION OF THE USE OF LIMONENE FOR DETECTING SINGLET OXYGEN AS A COMPONENT OF POLLUTED AIR
Authors: Rawls H. Ralph , Estes Frances L.
Published: January 2008

Abstract— Exploratory experiments using simulated conditions indicate that the terpene, (+)‐limonene can serve to detect O2(1Δg) in polluted atmospheres. 1O2 attack on limonene results in the formation of specific oxidation products in a specific distribution; quantitative identification of these products is a highly specific test for 1O2.
THE REACTIONS OF HYDROXYL RADICAL WITH SOME TRANSITION‐METAL COMPOUNDS CONTAINING ORGANIC MOLECULES
Authors: Waltz William L. , Woods Robert J. , Whitburn Kevin D.
Published: January 2008

Abstract— Recent reports that have appeared in the literature concerning the reactions in aqueous media of hydroxyl radical with some transition‐metal compounds containing bound organic molecules are discussed and experimental results on the reactions of hydroxyl radical with some platinum complex ions are presented. Emphasis is placed on the comparison of the behavior of the free ligand relative to that of the complexed and protonated forms. The occurrence of metal‐ion complexation can modify to varying degrees the reactivity of organic entities towards hydroxyl radical and the subsequent behavior of the products. The influence of the metal center is considered to involve its Lewis acidity, π‐bonding capabilities as well as features such as its formal oxidation state.
THE ROLE OF SUPEROXIDE AND SINGLET OXYGEN IN LIPID PEROXIDATION
Authors: Svingen Bruce A. , O'Neal Fredrick O. , Aust Steven D.
Published: January 2008

Abstract— An investigation into the mechanism of lipid peroxidation catalyzed by xanthine oxidase showed a dependence upon superoxide, singlet oxygen and adenosine 5'‐diphosphate chelated iron (ADP‐Fe3+). In the absence of ADP‐Fe3+ or in the presence of superoxide dismutase there is complete inhibition of enzymatic peroxidation. Initiation of peroxidation likely occurs through an ADP‐perferryl ion complex formed by ADP‐Fe3+ and superoxide. Use of the singlet oxygen trapping agent 2,5‐diphenylfuran showed that singlet oxygen does not participate in the initiation of peroxidation but rather in the propagation of peroxidation. The mechanisms of NADPH‐cytochrome P450 reductase‐catalyzed and ADP‐Fe2+ catalyzed lipid peroxidation parallel that of xanthine oxidase in that initiation occurs through a superoxide dismutase‐sensitive reaction and that singlet oxygen is present during propagation of lipid peroxidation.
RADIATION ACTIVATION OF CARCINOGENS AND THE ROLE OF OH AND O2‐
Authors: Greenstock Clive L. , Ruddock George W.
Published: January 2008

Abstract— Radiation‐induced covalent binding of labelled carcinogens to DNA has been investigated under a variety of conditions using ultrafiltration or millipore filtration of TCA precipitable complexes. High yields of carcinogen binding at high DNA concentrations are also observed for a variety of small molecules and are not carcinogen‐specific. At high carcinogen concentrations, radiation‐induced unstable electrophilic carcinogenic species are produced, and undergo free‐radical reactions which simulate cellular redox reactions involved in metabolic carcinogen activation, leading to the formation of covalently bound carcinogen adducts to DNA as a potential target macromolecule. The yields of carcinogen‐DNA adducts increase linearly with dose and depend upon carcinogen concentration. The results of scavenger studies indicate that the oxidising species O2‐ and OH are the principal activating species. Rate constants for the selective radiation‐induced oxidation reactions of various chemical carcinogens with superoxide have been measured by a competition kinetic method using pulse radiolysis. The relatively long‐lived superoxide radical reacts with carcinogens at a rate which is two orders of magnitude slower than the diffusion‐controlled rate for the hydroxyl radical, thus allowing a measure of O2‐ specificity in the presence of competing reactants within the cell.
DNA POLYMERASE I‐MEDIATED REPAIR OF 365 NM‐INDUCED SINGLE‐STRAND BREAKS IN THE DNA OF ESCHERICHIA COLI*
Authors: Ley Ronald D. , Sedita B. Ann , Boye Erik
Published: January 2008

Abstract. Irradiation of closed circular phage Λ DNA in vivo at 365 nm results in the induction of single‐strand breaks and alkali‐labile lesions at rates of 1.1 × 10‐14, and 0.2 × 10‐14/dalton/J/m2, respectively. The sum of the induction rates is similar to the rate of induction of single‐strand breaks plus alkali‐labile lesions (1 × 10‐14/dalton/J/m2) observed in the E. coli genome. Postirradiation incubation of wild‐type cells in buffer results in rapid repair of the breaks (up to 80% repaired in 10 min). No repair was observed in a DNA polymerase I‐deficient mutant of E. coli.
TYROSINE‐SENSITIZED PHOTODIMERIZATION OF THYMINE IN AQUEOUS SOLUTION
Authors: Kaneko Motohisa , Matsuyama Akio , Nagata Chikayoshi
Published: January 2008

Abstract. Photodimerization of thymine in aqueous solution in the presence of tyrosine was studied with monochromatic UV irradiation. The total dimer formation was sensitized in the presence of tyrosine. The action spectrum of sensitized total dimer formation has a peak near 280 nm corresponding to the absorption maximum of tyrosine. Triplet quenchers reduced the sensitization substantially. It seems probable that tyrosine‐sensitized photodimerization of thymine occurred via triplet‐triplet energy transfer from tyrosine to thymine.
EFFECT OF PSORALEN AND NEAR UV ON VERTEBRATE CELLS IN CULTURE: COMPARISON OF LASER WITH STANDARD LAMP
Authors: Peterson Scott P. , Berns Michael W.
Published: January 2008

Abstract. 4′‐Aminoethyl‐4,5′,8‐trimethylpsoralen, a DNA photoreagent, was used in conjunction with near UV light to modify cell growth and morphology. Since near UV radiation is needed to trigger the photoreactions, various doses of classical and laser near UV light were exposed to cells growing in media containing psoralen. It was found that near UV light caused a reduction in cell viability as indicated by complete inhibition of growth. The specificity of psoralens for nucleic acids was also investigated by using a tritium labeled psoralen derivative and tracing its appearance in different fractions of DNA from treated and untreated cells.
APPLICATIONS OF CALCIUM‐SENSITIVE PHOTOPROTEINS IN EXPERIMENTAL BIOLOGY
Authors: Blinks J. R.
Published: January 2008

Abstract—Calcium‐sensitive photoproteins are “precharged bioluminescent proteins that are triggered to emit light by binding Ca2+ or certain other inorganic ions. Neither molecular oxygen nor any organic cofactor is required. The first such protein to be described was aequorin, and for various reasons that has been the one most widely studied. Photoproteins have been used as Ca2+‐indicators both in vitro and in living cells. Their chief advantages for this are (1) ease of signal detection, (2) high sensitivity, (3) relative specificity for Ca2+, and (4) lack of toxicity. Difficulties in the experimental use of the photoproteins stem from (1) their one‐time reactivity, (2) their large molecular size, (3) their scarcity, (4) the influence of experimental conditions on the sensitivity to Ca2+, (5) the nonlinearity of the relation between [Ca2+] and light intensity, and (6) the limited speed with which light intensity follows sudden changes in [Ca2+]. Photoproteins have now been used as intracellular calcium indicators in more than two dozen types of cells, and experience with the method is rapidly growing. They are also useful in the determination of calcium binding constants for other substances in vitro, and as models for studies of receptor‐ligand interactions in general.
INTRODUCTION: ULTRAFAST REACTIONS IN PHOTOSYNTHESIS
Authors: Govindjee
Published: January 2008

The present issue of Photochemistry and Photobiology deals with the “ultra‐fast reactions” in the primary process of photosynthesis. The definition of what one calls “ultra‐fast reactions” was left to the individual authors; it ranged from picoseconds (ps) to microseconds (μs). All of the papers were invited for this issue; these include those presented by the various speakers (to be cited at appropriate places) at the symposium on “Primary Photoprocesses in Photosynthesis: Ultrafast Reactions” held at the 5th annual meeting of the American Society for Photobiology, May 11–15, 1977, in San Juan, Puerto Rico. All the papers in this issue were reviewed by three authorities in the field, and the authors have incorporated as many of their suggestions as possible. I thank all the reviewers for their help and their names will be included in the annual list of the reviewers of the entire journal of Photochemistry and Photobiology.
SENSITIZED PHOTOOXIDATION OF ISOEUGENOL TO VANILLIN
Authors: Bkins K.
Published: January 2008

Abstract— The photochemical conversion of isoeugenol to vanillin can proceed via the 1O2 (1Δg) state of oxygen and can be effected over a wide range of base and dye concentrations. A typical situation involving methylene blue (0.3 mM), isoeugenol (24 mM) and a base concentration of 0.1 N will give yields of approximately 35% of the theoretical amount.
THERMAL AND PHOTOSENSITIZED DECOMPOSITION OF DIMERIC VALEROPHENONE PEROXIDE FORMED BY OZONATION OF VALEROPHENONE OXIME ETHER*
Authors: Ito Yoshikatsu , Konishi Mitsuo , Matsuura Teruo
Published: January 2008

Abstract— Ozonation of valerophenone oxime o‐methyl ether (4) produced a stereoisomeric mixture of crystalline dimeric valerophenone peroxides, 5a and 5b. N‐n‐butyl‐N‐methoxybenzamide (6) and N‐methoxy‐N‐phenylvaleramide (7) along with valerophenone (1). Thermolysis of the higher melting peroxide 5a at 170–180°C, where a chemiluminescence was visible from added perylene. gave 1 and butyl benzoate (8) in addition to small amounts of the Norrish Type 11 products of 1. i.e. acetophenone (2) and cis‐ and trans‐ 2‐methyl‐1‐phenylcyclobutanols. Biacetyl‐sensitized photolysis of 5a in benzene yielded 2 in much higher yield in addition to 1, 8, and biphenyl. These results suggest that the triplet excited state of 1 is formed by the decomposition of 1 in low yield in thermolysis and in much higher yield in sensitized photolysis. although some of the Type II products may not arise from the triplet valerophenone.
PHOTOALLERGIC RESPONSES TO CHEMICALS
Authors: Kochevar Irene E.
Published: January 2008

Abstract— –Photochemical and immunologic knowledge about photoallergy to chemicals is briefly summarized. Studies in in vitro systems have demonstrated that photoallergic compounds can covalently bond to proteins through a photochemical reaction. The immunologic nature of the photoallergic response is based mainly on clinical observations, induction of photoallergy in man and in guinea‐pigs and on results of in vitro immunologic tests.

Studies of the photoreactions of the photoallergic compound, 3,3′,4′,5‐tetrachlorosalicylanilide (TCSA), with proteins are discussed. TCSA noncovalently bonds to human serum albumin prior to irradiation. Prior interaction is essential for formation of a photoaddition product indicating that a short‐lived reactive species derived from TCSA is involved in the photoaddition and limiting the number of skin proteins which can participate in antigen formation. By fragmentation of the TCSA‐albumin photoadduct with CNBr, it was determined that TCSA can bond to at least three sites on the albumin molecule. TCSA also can sensitize the photooxidation of histidine in albumin.
GENETIC CONTROL OF NEAR‐UV (300–400nm) SENSITIVITY INDEPENDENT OF THE recA GENE IN STRAINS OF ESCHERICHIA COLI K12
Authors: Tuveson R. W. , Jonas Richard B.
Published: January 2008

Abstract— Stationary cells of isogenic pairs of Escherichia coli K12 strains presumably differing only in the recA function have been inactivated with near‐UV (300–400 nm) radiation. Based on near‐UV inactivation kinetics, the strains can be divided into two discrete categories in which near‐UV sensitivity does not necessarily correlate with far‐UV sensitivity conferred by two different recA alleles. Lack of overlap between near‐UV and far‐UV (recA) sensitivity can be explained hy assuming that a different chromosomal gene (nur) controls near‐UV sensitivity. Support for this hypothesis comes from a mating experiment in which four selected recombinants, isogenic with respect to auxotrophic markers, were identified exhibiting all four possible combinations of far‐UV (recA1 vs recA +) and near‐UV sensitivity (nur vs nur+). Transduction with phase P1 has shown that introduction of the recA1 allele into a recA+ recipient does not affect the near‐UV sensitivity of the recipient. Additional matings together with transduction experiments suggest that the nur gene is located at a position on the E. coli linkage map clearly separable from recA (minute 58).
SOLUTE‐SOLVENT INTERACTION AND ITS EFFECT ON THE VIBRONIC AND VIBRATIONAL STRUCTURE OF PYRENE SPECTRA
Authors: Lianos P. , Georghiou S.
Published: January 2008

Abstract— The enhancement of weakly allowed electronic and vibrational transitions of pyrene in polar solvents at room temperature has been studied by optical and infrared techniques. We previously reported the formation of molecular complexes between pyrene and alcohols by monitoring the changes in the fundamental stretching vibrational band of the —OH group of alcohols in the presence of pyrene. The infrared spectrum of pyrene in the region 1575–1700cm‐1 has been found in the present work to undergo changes in polar solvents, consistent with complex formation, with the appearance of new bands at wavenumbers where symmetry‐forbidden transitions exist. The enhancement of weak bands in the electronic spectra is attributed to the reduction in the symmetry of the pyrene molecule brought about by complex formation. Further support for this interpretation is provided by the finding that I‐methylpyrene, which has reduced symmetry, shows the enhancement in the electronic spectra and the appearance of new bands in the infrared spectra even in inert solvents. The anomalous behavior of aromatic solvents is discussed.
DAMAGE TO THE ALBINO RAT RETINA PRODUCED BY LOW INTENSITY LIGHT*
Authors: Rapp L. M. , Williams T. P.
Published: January 2008

Abstract—Continuous exposure of albino rats to low intensity light causes progressive deterioration of the photoreceptor cells. Losses in ERG (b‐wave) sensitivity which accompany this ‘light damage’ are directly related to lowered rhodopsin levels in the retina. The same relationship has been observed in light adaptation studies in which the retina is not damaged. Thus, it appears that the production of b‐wave responses is not seriously altered when photoreceptor morphology is disrupted.
RAPID REDUCTION OF P‐700 PHOTOOXIDIZED BY A FLASH AT LOW TEMPERATURE IN SPINACH CHLOROPLASTS
Authors: Mathis P. , Conjeaud H.
Published: January 2008

Abstract—Excitation of chloroplasts at low temperature (down to 4.2 K) by short laser flashes causes largely reversible absorption changes which are attributed to the photooxidation of P‐700, the primary electron donor of Photosystem I. At temperatures below 100 K the dark re‐reduction of P‐700+ is biphasic. with half‐times of about 122μs and 1.7 ms. The relative contribution of the two phases varies with temperature with the fast phase becoming dominant at the lowest temperatures (˜90% at 5 K). The results are interpreted in terms of tunnelling of the electron from one or two primary accepting sites back to P‐700, a process which is largely dominant over the process of charge stabilisation.
A SEROLOGICAL STUDY OF REMOVAL OF UV‐INDUCED PHOTOPRODUCTS IN THE DNA OF TETRANYMEN A PYRIFORMIS GL: INFLUENCE OF CAFFEINE, QUINACRINE AND CHLOROQUINE
Authors: Lakhanisky Th. , Hedrickx B. , Mouton R. F. , Cornelis J. J.
Published: January 2008

Abstract—Antisera that recognize specifically UV‐photoproducts in DNA have been used to follow the elimination of photolesions in UV irradiated Tetrahymena pyriformis. The amount of bound tritiumlabelled antibodies to nuclei has been estimated by autoradiography. Curves of dose‐response of DNA photoproducts, their elimination by dark repair, and effect of caffeine, quinacrine and chloroquine on the disappearance of UV‐lesions have been evaluated.
REVISED SPECTRA FOR THE INACTIVATION OF HAEMOPHILUS INFLUENZAE TRANSFORMING DNA BY MONOCHROMATIC ULTRAVIOLET LIGHT: EFFECT OF HISTIDINE
Authors: Peak M. J. , Tuveson R. W.
Published: January 2008

Abstract—It was reported previously that histidine sensitizes the genetic activity of Haemophilus influenzae transforming DNA to pure 334 nm ultraviolet light, Further measurements show that this apparent 334 nm sensitization was probably erroneous and that in fact, histidine protects DNA against inactivation by 334 nm light. This is now consistent with all previous observations that transforming DNA is protected by histidine against all near‐UV wavelengths (above 320 nm) investigated.

A modified spectrum for the protection of H. influenza transforming DNA by histidine against ultraviolet light is described.
CUT‐OFF FILTERS FOR THE NEAR ULTRAVIOLET
Authors: Klein Richard M.
Published: January 2008

Abstract—A series of transmission curves of liquid and solid sheet filter materials in the 280–400 nm range is presented. These filters may be useful as cut‐off filters for the near UV.
ON THE PHOTOIONIZATION ENERGY THRESHOLD OF TRYPTOPHAN IN AQUEOUS SOLUTIONS
Authors: Amouyal E. , Bernas A. , Grand D.
Published: January 2008

Abstract— To investigate the existence and energy position of a photoionization threshold. tryptophan (Trp) has been photoionized in desecrated neutral aqueous or alcoholic solution under monochromatic light of variable frequency, in presence of N2O to scavenge the photoelectron.

Present findings and some literature data converge to show the existence of a threshold for the one photon ionization process. This threshold is located at 4.5 ± 0.1 eV and 4.85 ± 0.1 cV for Trp in aqueous and ethanol solutions. respectively, which corresponds to a lowering with respect to the gas phase ionization potential of 3.4 and 3.0 eV.

The photoionization quantum yields for Trp is found about 4 times greater at 250 nm than at Λcx= 265 nm, where ϕe‐4M=0.080±0.025. In such spectral range. at most one photoelectron out of 4–5 escaping geminate recombination would lead to Trp photodegradation in acrated solutions.

These results also point out that the neutral radical Trp. which has been previously observed for Λcx > 275 nm, i.e. below the ionization threshold energy—would not necessarily derive from Trp + deprotonation or cation‐electron dissociative recombination. Similarly, the opening of the indole ring with formylkynurenine (FK) formation which is observed under aerobic conditions and Λcx >, 280 nm would not imply an electron attachment on O2 but reactions such as Trp +3O2 or Trp*+3O2 or else