bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF MOLECULAR SHAPE ON THE FLUORESCENT PROPERTIES OF 9, 10‐DIPHENYLANTHRACENE
Authors: Hamilton T. D. S.
Published: January 2008

Abstract. ESR measurements on 9, 10‐diphenylanthrace in solution show that the molecule is non‐planar, the two phenyl rings being twisted by about 66° relative to the anthracene nucleus. This agrees with previous predictions made on the basis of scale models.

Evidence from absorption and fluorescence spectra for a change of angle between ground and excited state is examined, and a decrease of about 6° is found for the excited state. On the basis of the large angle of twist possible reasons are suggested for the difference between anthracene and 9, 10‐diphenylanthracne with regard to dimer formation and quantum yield of fluorescence in solution.
PHOTOREDUCTION OF ZINC PORPHIN BY ASCORBIC ACID*
Authors: Seely G.R. , Talmadge K.
Published: January 2008

Abstract— Zinc porphin is photoreduced to zinc chlorin through an intermediate dihydroporphin (PH2) by ascorbic acid in ethanol containing 1% to 10% (v/v) piperidine. Under the same conditions zinc chlorin is more slowly photoreduced to zinc tetrahydroporphin. The reactions leading to chlorin are photosensitized by the product chlorin and so are autocatalytic in red light. Quantum yields for these reactions range up to 0.05.Other aliphatic amines catalyze these reactions, but at rates peculiar to the amine. The immediate product of reduction of zinc porphin, PH2, is distinguished by an intense band at 437 nm; it reverts to porphin in the dark in the presence of oxygen or dehydroascorbic acid. Its conversion to chlorin is effected by light absorbed by porphin or chlorin, but not by light absorbed by PH2 itself. A suggested structure for PH2, compatible with the observed reactions, has added hydrogens on one bridge carbon and one β‐pyrrole carbon. The possibility of an analogy between these reactions and the biochemical conversion of protochlorophyll to chlorophyll is discussed.
THE EFFECT OF RED AND FAR‐RED LIGHT ON NUCLEIC ACID METABOLISM IN RYE SEEDLING SHOOTS
Authors: Holdgate D. P. , Goodwin T. W.
Published: January 2008

Abstract— The quantitative changes in the levels of RNA and DNA in shoots treated with red and/or far‐red light are presented.

The results indicate that red light, but not far‐red light, stimulated cell division. The changes in RNA are discussed in relation to the nature of the light treatment.
THE CHEMILUMINESCENCE OF CERTAIN INDOLES*
Authors: Philbrook G. E. , Ayers J. B. , Garst J. F. , Totter J. R.
Published: January 2008

Abstract— A series of twenty‐four indoles and related compounds have been examined for chemiluminescent activity in aqueous solution and in dimethylsulfoxide. Seven compounds were found to chemiluminesce in the presence of base and peroxydisulfate in aqueous solution and eleven compounds gave chemiluminescence in dimethylsulfoxide with base using oxygen as the oxidizing agent. The relative intensities have been determined. There is no clear correlation between substitution patterns and the presence of chemiluminescence in either series. Some preliminary kinetic studies have been made on the indole system. Product studies indicate that the indole is degraded by at least two different pathways and that chemiluminescent process is probably only a small fraction of the total chemical change occurring.
INFLUENCE DES ÉCLAIREMENTS APPROXIMATIVEMENT MONOCHROMATIQUES SUR LE DEVELOPPEMENT DES TISSUS DE MOELLE DE TABAC CULTIVBS IN VZTRO EN PRESENCE D'AUXINE ET DE KINETINE
Authors: Beauchesne G. , Poulain Melle C.
Published: January 2008

Abstract— The influence of relatively monochromatic light (around 4350, 5250, 6600 and 8000 Å) on the growth of cultures of tobacco pith tissues with auxin and kinetin was studied. The cultures were subjected either to continued light or to alternations of 16 hr light with 8 hr darkness, or to a dark period followed by continuous light.

The influence of blue light was especially noted. The development in volume and weight of the cultivated tissues in blue light is generally less than in the other conditions (except for one or two exceptions); the differences are attenuated when a light period alternates with a period of darkness; the callus tissues of tobacco pith exposed to blue light are always chlorophyllic with a dense and hard appearance and histological studies show that tissues grown in blue light are mostly made of large cells with thick cell‐walls and many nodules while under the other conditions the tissues are mostly made of very small cells with few or no nodules.

These differences seem related to specific photoreceptors rather than to energies delivered to the cultures.
DISC ELECTROPHORESIS OF IRRADIATED TRYPSIN*
Authors: Ghiron Camillo A. , Ghiron Arlene F. , Spikes John D.
Published: January 2008

Abstract— Trypsin inactivated by u.v. radiation, gamma radiation, visible radiation in the presence of sensitizing dyes, and autolysis, was examined by the method of disc electrophoresis. Untreated Worthington twice crystallized salt‐free trypsin separated into four bands which moved toward the cathode; the main band, which had the greatest mobility, contained all of the detectable tryptic activity. The next most mobile band has been assumed to be a chymotrypsin contaminant. The other two bands are of unknown nature. A progressive loss of all the bands was observed when the enzyme was inactivated by those procedures which produce a ‘damaged’ class of trypsin molecules, i.e. flavin‐sensitized photooxidation, autolysis, and treatment with u.v. and gamma radiation. No loss of the main band was observed during photoinactivation with methylene blue and eosin Y as sensitizers. In this latter case, it is postulated that the trypsin inactivation products must be of such a nature that the net charge and conformation of the protein is not greatly changed, thus permitting all of the protein to remain in the same band during electrophoresis.
SOME NEW STABLE ULTRAVIOLET TRANSMITTING SOLUTION FILTERS
Authors: Wladimiroff W. W.
Published: January 2008

Abstract— For use with very intense light source, e.g. flash lamps and high‐pressure arcs, some new stable transmission filters for the U.V. were developed. All filters were composed to give maximum transmittance in the desired bands together with optimum absorbance of the visible light, at an optical path of 1 cm. The filters described are easy to prepare and have considerably better properties than the well known NiSO4‐‐CoSO4 filter and other filter combinations.

During initial irradiation with high‐intensity light sources the transmittance of the freshly prepared filter solutions increases slowly till maximum transmittance is attained. The position of the transmission bands, however, does not change.

Based on the fact that the 6700 Å absorption band of some non‐aqueous solutions of CoCl2 has an extinction coefficient about a hundred times larger than the 5100 Å absorption band of the aqueous solution with the same concentration, filter solutions were developed for the following transmission bands: 2600–3900 Å, 2900–3900 Å and 3100–3900 Å with transmission maxima of 90, 90 and 75 per cent respectively, and 2600–4600 Å, 2900–4500 Å and 3100–4600 Å with transmission maxima of 95, 95 and 90 per cent respectively, at an optical path of 1 cm.
AN ABSORPTION BAND NEAR 800 mμ ASSOCIATED WITH P870 IN PHOTOSYNTHETIC BACTERIA*
Authors: Clayton Roderick K. , Sistrom William R.
Published: January 2008

Abstract— Purple photosynthetic bacteria contain a component, absorbing near 805 mμ, distinct from the major light harvesting bacteriochlorophyll component. The minor component, designated P800, resembles P870 in that it resists oxidative treatments that destroy the light harvesting bacteriochlorophyll. Light induces a reversible blue‐shift of P800 together with the reversible bleaching of P870. The ratio of P800 to P870 in Rhodopseudomonas spheroides is constant. Both pigments are absent in phenotypes that cannot grow photosynthetically; they reappear together in revertants to photosynthetic competence.

Action spectra for light‐induced bleaching of P870 and for bacteriochlorophyll fluorescence show that P800 transfers energy more efficiently to P870 than to the bulk bacteriochlorophyll.

It is concluded provisionally that P800 is a specialized bacteriochlorophyll molecule in close proximity to the reaction center component P870.
ACTION SPECTRA FOR PHOTOREACTIVATION OF KILLING AND MUTATION TO PROTOTROPHY IN U.V.‐SENSITIVE STRAINS OF ESCHERICHIA COLI POSSESSING AND LACKING PHOTOREACTIVATING ENZYME*
Authors: Kondo Sohei , Kato Takesi
Published: January 2008

Abstract— Ultraviolet‐sensitive strains of E. coli, Hs30 (uvr‐ phr‐ arg‐), lacking the ability to repair ultraviolet damage in the dark (uvr‐), lacking photoreactivating‐enzyme activity (phr‐), and lacking the ability to synthesize arginine (arg‐), and Hs30–R (uvr‐ phr+ arg‐), having the same auxotrophic marker and the same high u.v.‐sensitivity, were derived, respectively, from resistant strain H/r30 (uvr+ phr‐ urg‐) and its revertant H/r30–R (uvr+ phr+ urg‐). Hs30 and Hs30–R have about 25 and 35 times higher sensitivity than H/r30 and H/r30–R for u.v.‐induced killing and mutation to prototrophy, respectively. Efficiency of photoreactivation (PR) of mutation in strain Hs30–R is about ten times higher than the PR efficiency in the parent strain H/r30–R at wavelengths between 3341 and 4358 Å but not that much higher at 3132 Å. On the other hand, Hs30 shows no PR at any of these wavelengths, although the parent strain H/r30 does show PR of mutation around 3341 Å., These results support the. previously described model that PR in H/r30 is an indirect effect of PR light which enhances dark repair. It is concluded that Hs30 and Hs30–R lack dark‐repair capacity for u.v.‐induced mutational damage and that the same type of photoreactivable DNA lesions as those responsible for U.V. killing, i.e. pyrimidine dimers, are the primary cause of u.v.‐induced mutation in the uvr‐strains. PR spectra for killing in Hs30–R and mutation in H/r30–R and H/r30 were obtained and compared, and the quantitative conclusions reached are discussed in connection with the hypothesis that the same kind of lesion (pyrimidine dimer) is the primary cause of mutation in the uvr+ strains as well.
CHLOROPHYLL MONOLAYERS AND MUTILAYERS—I. METHODS OF PREPARATION AND SPECTROSCOPIC CHARACTERIZATION*
Authors: Sperling Walter , Ke Bacon
Published: January 2008

Abstract— Precise methods of preparing monolayers and multilayers of chlorophyll a alone or mixed with arachidic acid on glass slides prewated with monolayers of barium arachidate are described in detail. Chlorophyll monolayers obtained by this method are mechanically stable and allow the absorption spectra or other spectroscopic characterizations to be readily made.

The data on absorption spectra indicate that uniformly deposited multilayers of over 100 pure chlorophyll a monolayers or over 400 mixed monolayers were obtained. Theabsorbance in the multilayer was directly proportional to the total number of layers. For a given surface pressure used in depositing the multilayers, the absorbance per layer was constant.
THE U.V. PHOTOCHEMISTRY OF CYTIDYLIC ACID
Authors: Becker H. , LeBlanc J. C. , Johns H. E.
Published: January 2008

Abstract The ultraviolet (u.v.) irradiation of the 3′ isomer of cytidylic acid (Cp) produces the hydrate (Cp*) with water added across the 5–6 double bond. The yield of this photo‐product has been measured by, (a) separating the photoproduct by electrophoresis and (b) by observing the loss in absorbance. When corrections are made for reversal of the hydrate during the experiment, both methods gave the same result. Cross sections and quantum yields for the production of the hydrate were measured over the wavelength range 220 to 290 nm and over a pH range from 1 to 10. The quantum yield is markedly dependent on pH being higher by a factor of 6 to 10 for the neutral form. We have also demonstrated the existence of a very short lived photoproduct (half life 8–9 min) in both Cp3′ and Cp5′: The nature of this short lived product is not known.
INVESTIGATION OF MAGNESIUM TETRABENZPORPHYRIN‐II.:REDOX AND PHOTOCHEMICAL PROPERTIES IN ORGANIC SOLVENTS AND AQUEOUS MEDIUM
Authors: Goedheer J. C.
Published: January 2008

Abstract Absorption and fluorescence properties of MgTBP were studied resulting from chemical oxidation and phtooxidation. The absorption spectra of the oxidised product in methanol and acetone are markedly different from those in aqueous solvents.
PRODUCTION OF PEPTIDE COMPOUNDS FROM ETHYLENE GLYCOL AND HYDROXYLAMINE BY RADIATIONINDUCED SYNTHESIS*
Authors: Cultrera R. , Zamorani A. , Ferrari G.
Published: January 2008

Abstract Aqueous solutions of ethylene glycol and hydroxylamine in a 10:1 weight ratio were irradiated with an immersion‐type mercury‐vapour lamp, under static and dynamic conditions. The photochemical products obtained were fractionated by means of ion‐exchange resins, gel filtration on Sephadex G 10, paper chromatography, and thin‐layer chromatography.

Biuret reaction was carried out on the various fractions, and different nitrogen forms as well as amino acids, before and after hydrolysis, were determined. Irradiation was found to bring about the formation of a number of organic compounds, including peptides. The yields of these compounds were determined in relation to the concentration and the flow rate of the solutions. The yields increased with increase in the two variables.

The fractions richest in peptide compounds, coming from gel‐filtration and thin‐layer chromatography, were studied by the technique of DNP‐derivatives. The constituent amino acids were found to be glycine, β‐alanine, α‐alanine, glutamic acid and leucine. The average length of the chains contained 7 amino acids.
THE FLUORESCENCE OF CAROTENOIDS
Authors: Wolf F. T. , Stevens M. V.
Published: January 2008

Abstract The carotenoids β‐carotene, lutein, lutein epoxide and violaxanthin are fluorescent compounds. Upon excitation around 280 mμ, at wavelengths close to those of their ultraviolet absorption maxima, these carotenoids fluoresce within the range 300–400 mμ, with maximal fluorescence at approximately 320–340 mμ.
THE EFFECTS OF HOST‐CELL REACTIVATION ON ASSAY OF U.V.‐IRRADIATED HAEMOPHILUS INFLUENZAE TRANSFORMING DNA
Authors: Patrick M. H. , Rupert C. S.
Published: January 2008

Abstract— The host cell reactivation (HCR) mechanism in Haemophilus influenzae cells is inhibited by sub‐microgram concentrations of acriflavine (as is already known to be true for Escherichia coli). Exposure of these cells to similar concentrations of the drug during bacterial transformation increases the apparent ultraviolet light (u.v.) sensitivity of previously irradiated transforming DNA, indicating a repair of this DNA after uptake by the cells under normal conditions. Repair is inhibited by applying acriflavine at any time up to one hour after competent cells contact the irradiated transforming DNA. The fraction of the u.v. damage repaired by HCR is very different for different genetic markers. Those markers which are most u.v. sensitive when assayed in the absence of acriflavine are most poorly repaired, suggesting that this is the reason for their higher sensitivity. For all markers the fraction of the damage repairable by in vitro photoreactivation is approximately constant, and strongly overlaps the damage repairable by HCR. The degree of HCR achieved can be altered by experimental treatment of the H. influenzae DNA prior to transformation. Thus treatment of irradiated DNA with an enzyme from Micrococcus lysodeikticus–known to attack u.v. damaged, but not undamaged DNA–prevents subsequent intracellular repair of the same u.v. lesions whose repair is inhibited by acriflavine. Similarly, partial replacement of the thymine in transforming DNA by 5‐bromouracil (BU) strongly inhibits repair of subsequent u.v. damage. As in bacteriophage, the BU effect is relieved if the u.v. exposure occurs in the presence of cysteamine. It is clear that intracellular repair must be considered in interpreting experiments with u.v.‐irradiated transforming DNA.
THE NON‐RADIATIVE DISSIPATION OF EXCITATION ENERGY IN SOLID CINNAMIC ACID BY DIMER FORMATION
Authors: Rennert J. , Ruggiero E. M. , Rapp J.
Published: January 2008

Abstract— The quantum efficiency for the photodimerization of trans‐cinnamic acid in the solid state is independent of intensity and is found to have a value approaching two. Thus, the reaction involves one excited and one un‐excited molecule.

During the exposure, a dimer film developing on the surface of the cinnamic acid layer attenuates the intensity of the radiation incident on the unreacted cinnamic acid. This gives the appearance of a decrease in the quantum yield with increasing number of photons incident.
THE PHOTOCHEMISTRY OF RIBOFLAVIN—II. POLAROGRAPHIC STUDIES ON THE HYDROXYETHYL AND FORMYLMETHYL ANALOGS OF RIBOFLAVIN*
Authors: Mcbride Martha M. , Moore William M.
Published: January 2008

Abstract— The anaerobic photobleaching of 6, 7‐dimethyl‐9‐(2′‐hydroxyethyl)‐isoalloxazine, 9‐(2′‐hydroxyethyl)‐isoalloxazine and 6,7‐dimethyl‐9‐(formylmethyl)‐isoalloxazine have been compared. Polarographic and spectrophotometric techniques were used for rate studies. The methyl groups on the aromatic ring at the 6 and 7 positions affects the product distributtion in these simple flavins. Formylmethylflavin is postulated to undergo a bimolecular photoredox reaction which is novel to flavin photochemistry. It was demonstrated that there is a common type of leucoflavin formed during anaerobic photobleaching of riboflavin, formylmethylflavin and hydroxyethylflavin. This leucocompound also formed during the photoreduction of formylmethylflavin but not during the photoreduction of the other flavins.
INFRARED SPECTRAL OBSERVATIONS OF CHLOROPHYLL‐a AND ETHYL CHLOROPHYLLIDE‐a IN THE SOLID STATE*
Authors: Sherman Gwendolyn , Wang Shu‐Fong
Published: January 2008

Abstract— Infrared spectra of ethyl chlorophyllide‐a and chlorophlyll‐a in Nujol mulls show a shift of the C9 ketone carbonyl absorption band to higher frequencies when the pigments are subjected to drying processes. The ketone band can then be reversed back to lower frequencies by exposing the material to moisture. These observations indicate that the nature of chlorophyll aggregation in the solid state varies with the water content of the pigment.
ZUM WIRKUNGSMECHANISMUS PHOTODYNAMISCHER FUROCUMARINE PHOTOREAKTION VON PSORALEN‐(4‐14C) MIT DNS, RNS, HOMOPOLYNUCLEOTIDEN UND NUCLEOSIDEN
Authors: Krauch C. H. , Krämer D. M. , Wacker A.
Published: January 2008

Abstract— The photodynamic binding of psoralen to DNA and RNA was shown using different methods. This binding was found to be mainly located either at thymine or uracil. The concentration and pH dependancy was studied. The photoproduct obtained with uridine was isolated paper chromatographically and was split into initial components photochemically.

The results bring an evidence that psoralen with its 3,4‐double bond is able to form a cyclic derivative with the C6‐C6 doble bond of thymine or uracil.
DELAYED FLUORESCENCE AND SOME PROPERTIES OF THE CHLOROPHYLL TRIPLETS
Authors: Parker C. A. , Joyce Thelma A.
Published: January 2008

–P‐Type delayed fluorescence and sensitised P‐Type delayed fluorescence have been observed from solutions of chlorophylls a and b in ethanol. E‐Type delayed fluorescence has been observed from solutions in propylene glycol. The measurements in propylene glycol have yielded approximate values for the triplet energies of chlorophylls a and b. Measurements of the emissions from the ethanolic solutions have been used to calculate approximate values of the triplet formation efficiencies in this solvent. The sums of the fluorescence and triplet formation efficiencies in ethanol fall far short of unity and the triplet formation efficiencies therefore need to be confirmed by an independent method before they can be accepted with confidence.
THE EFFECT OF ENVIRONMENT ON CYSTINE DISRUPTION BY ULTRAVIOLET LIGHT*
Authors: Risi Sergio , Dose Klaus , Rathinasamy T. K. , Augenstein Leroy
Published: January 2008

When cystine is irradiated at pH 1 by 254‐nm u.v. the following yields are observed: 4 cystines → 5.2 cysteines + 2.8NH3. Thus, SH production accounts for only 0.65 of the cystine destruction; further C‐S breakage to give alanine or serine is not efficient. The yields for cystine and glutathione destruction are essentially the same at pH 1. However the presence of the glutamic and glycine residues stabilize the cystine in glutathione so that NH3 is not lost until the peptide bonds are hydrolyzed. Increasing the pH from 1 to 8.6 increases the yield of cystine destruction in glutathione by 50 per cent. The yield of cystine destruction is greater in both compounds when O2 is present during irradiation (e. g. the cysteic acid yield in glutathione is increased by 50 times). The overall production of SH varies by a factor of 2 in the four proteins‐insulin, RNase, trypsin and lysozyme. The present data further support the earlier observation that radiation damage is quite non‐random in RNase: at least two and perhaps three of the four constituent cystines must be disrupted before activity is lost: i.e. the most radiosensitive cystines are not critical for enzymic activity. Similarly, in both trypsin and lysozyme the integrity of the most radiosensitive cystines also does not appear to be critical for the retention of enzymic potential. In insulin, however, all three cystines appear to be crucial for activity and to have approximately equal radiosensitivities. These differences in sensitivity of cystines in different proteins must depend specifically upon energy transfer and/or chemical interactions between the chromophoric groups. If yields are calculated on the basis of those quanta absorbed only in the cystines, values about 5 to 8 times greater than those in the model compounds cystine and oxixized glutathione are obtained. The yields of cystine destruction are much higher in those protiens which contain trypotophan.
CHLOROPHYLL‐PHOTOSENSITIZED OXIDATION OF HYDROQUINONE AND p‐PHENYLENEDIAMINE DERIVATIVES
Authors: Fujimori Eiji , Tavla Maria
Published: January 2008

Abstract— ESR and photovoltaic studies on light‐induced one‐electron transfer between chlorophyll a and electron donors in the absence of oxygen show (1) the possible conversion of photo‐reduced chlorophyll a and p‐benzosemiquinone ion radicals to their non‐ionic radicals in methanol solutions of low pH, (2) the production of ESR absorption of tetrachloro‐p‐benzosemi‐quinone even in benzene, enhanced by the addition of triethylamine or methanol, and (3) the transfer of one electron from tetramethyl‐p‐phenylenediamine to either excited chlorophyll a or pheophytin a in methanol at pH above 3.6 but not to pheophytin a at pH below 1 0 where its radical cation appears to accept an electron from excited pheophytin a. Bacteteriochloro‐phyll is also shown to be capable of photooxidizing hydroquinones and tetramethyl‐p‐phenyl‐enediamine.

The presence of oxygen enhances chlorophyll a‐photosensitized oxidation of hydroquinone and tetrachloro‐hydroquinone by one‐electron transfer to oxygen and of trimethylhydro‐quinone probably by two‐electron trnasfer to oxygen. A free radical from excited chlorophyll a‐oxygen interaction is formed in these reactions, but rapidly quenched in the case of trimethyl‐hydroquinone. This, kind of free radical is not formed in pheophytin a. Tetramethyl‐p‐phenyl‐enediamine readily undergoes chlorophyll a‐photosensitized oxidation by oxygen in any pH region.
DEGRADATION OF THE DNA OF ESCHERICHIA COLI K12 REC‐ (JC1569b) AFTER IRRADIATION WITH ULTRAVIOLET LIGHT*
Authors: Horii Z. I. , Suzuki K.
Published: January 2008

Abstract— Degradation of the DNA of a rec‐ mutant of Escherichia coli K12 (JC1569 b) induced by u.v. light was investigated. The rate of degradation was much larger by growing bacteria than by stationary cells. When growing bacteria were starved for amino acids, their DNA became resistant to irradiation. The mode of u.v.‐induced degradation was investigated by comparing the time course of release from the acid‐insoluble fraction of the label for two growing cultures; the one was pulse‐labeled with 3H‐thymidine and the other was pulse‐labeled and chased thereafter for 12 min. It was found that the label incorporated into the former culture begins to be lost from the acid‐insoluble fraction prior to the loss of the label incorporated into the latter culture. It was concluded that breakdown of the replicating point precedes degradation of the bulk of the DNA. This result suggested that the replicating point is a sensitive site to irradiation and the u.v.‐induced degradation of DNA seemed to be influenced by the state of chromosome at the time of irradiation. Experiments of centrifugation of lysed spheroplasts of bacteria uniformly labeled with 3H‐thymidine in alkaline sucrose demonstrated that DNA of low molecular weight appeared after irradiation with only 5 ergs/ mm2, and that the molecular weight could not be restored by post‐irradiation incubation. Considering these results, an hypothesis is proposed concerning the initiation of induced degradation of the DNA of the rec‐ mutant.
THE LIGHT REQUIREMENT OF ACID‐BASE TRANSITION INDUCED LUMINESCENCE OF CHLOROPLASTS
Authors: Mayne B. C.
Published: January 2008

Abstract— The luminescence that occurs when chloroplasts are taken from an acid environment to a basic one is shown to be dependent on prior illumination of the chloroplasts. The relation between the light absorbed and luminescence is given by the following equation L=Lmax(1‐eal where L and Lmax are the light emitted and maximum light emission at high flash energy, respectively, J quanta absorbed per chlorlphyll molecule, and α a constant with a value of approximately 200 chlorophyll molecules per quanta absorbed. The action spectrum of the luminescence is consistent with that of photosystem II. The metastable state formed during illumination decays in the dark via a temperature dependent second order process.
ESR STUDIES OF CHLOROPHYLL ONE‐ELECTRON PHOTOCHEMISTRY: KINETICS AND MECHANISM OF REVERSIBLE HYDROQUINONE OXIDATION IN SOLUTION*
Authors: Cho D. H. , Tollin G.
Published: January 2008

Abstract— ESR studies have been made of the kinetics of semiquinone radical formation and disappearance resulting from the reversible photosensitization by chlorophyll of hydroquinone oxidation in a pyridine‐water solvent. The rate of radical decay was found to be second order with respect to the radical concentration, with a rate constant of 6.7 × 105 l./mole sec at ‐30°C and an activation energy of 6900 cal/mole. The rate of radical formation was recombination‐limited and, through the use of β‐carotene as a quencher, the rate constant was determined to be 8.81 × 105 l./mole sec at ‐30°C. The effect of light intensity and hydroquinone concentration on the rate of semiquinone radical formation and on the steady state radical concentration was also investigated and possible mechanisms to explain the results are discussed.
DELAYED LUMINESCENCE OF ORGANIC MIXED CRYSTALS. VIII. THE LUMINESCENCE OF IMPURE CRYSTALS*,†
Authors: Mcglynns S. P. , Kinoshita M. , Mccarville M. , Srinivasna B. N. , Rabalais J. W.
Published: January 2008

Abstract— This paper represents an attempt to understand the delayed luminescence behavior of a real (i.e. impure) mixed crystal. The growth and decay of delayed luminescence is analyzed and shown to be complex. The studies embrace guest and guest concentration dependencies, temperature dependence and excitation intensity and wavelength variation. It is shown that a simple model enables proper interpretation of certain limiting characteristics of the delayed luminescence growth and decay behavior. It is also shown that the temperature dependence of phosphorescence spectra of mixed crystals is readily rationalized and that the complex growth and decay behavior of real crystals are interpretable in terms of guest‐guest, guest‐trap and trap‐trap annihilation phenomena. Differences in the growth and decay lifetimes of a given luminescence are analyzed fully and the reasons for the differences substantiated experimentally. The systems studied consist of aromatics and simple amino acids.
RADICAUX LIBRES INDUITS PAR L'ACTION DU RAYONNEMENT ULTRAVIOLET SUR CERTAINS CONSTITUANTS DE L'ACIDE DEOXYRIBONUCLEIQUE
Authors: LACROIX et M. , VORST A. VAN DE
Published: January 2008

The action of ultra violet rays of 260 nm on aqueous solutions of bases, nucleosides and nucleotides of DNA at 77°K is studied by electron spin resonance. It is shown that the free radicals observed are similar, with a few noteworthy exceptions to those induced by X‐rays, under the same conditions of temperature, in the solid state. Contrary to what might be excepted on the basis of the results obtained by X‐rays, the variation in the yield in paramagnetic centres in each sequence studied does not seem to be important.
PHOTOINHIBITION OF GROWTH OF‐ A YELLOW AND A COLORLESS FORM OF CHLAMYDOMONAS REINHARDTII*
Authors: Gross R. E. , Dugger W. M.
Published: January 2008

Abstract— Long‐term growth on acetate in darkness of a permanently yellow and a white‐in‐darkness mutant of Chlamydomonus reinhardtii showed no requirement for light. Room light or moderate intensities of white light severely inhibited the white mutant, but allowed continuous growth of the yellow form. Blue light (460 nm) stops motility and growth, and induces clumping, in the white form at energy levels which only reduce the growth rate of the yellow mutant. Green light (550 nm) had no effect on either strain, while red light (630 nm), at equal energy levels, affected the white mutant only, however, not as severely as blue light. The mechanism of action of blue and red light is unknown. Evidence suggested the inhibition is not due to cell exudates.
A SPECTROSCOPIC STUDY OF THE PHOTODECOMPOSITION OF DIAZOMETHANE
Authors: Ogilvie J. F.
Published: January 2008

Abstract— The decomposition of diazomethane by photolytic means has been studied both in inert gas matrices near 4°K and in the gas phase near 295°K. The direct detection of the diazomethyl radical, HCNN and DCNN, and evidence for the participation of methanal azine, H2C=‐N=CH2, by vibrational spectroscopy proved that both species play a significant role in the decomposition schemes under the conditions of investigation. The present results make possible the reinterpretation of the data from earlier published experiments to conform to these schemes. The isomerisation of diazomethane is also discussed, and evidence is presented for the production of both diazirine and isodiazomethane under certain photolytic conditions, the former by an intramolecular process and the latter by the recombination of the diazomethyl radical with a hydrogen atom. The vibronic absorption spectra of gaseous diazomethane at 295°K are presented, and deductions concerning photochemical processes are drawn.
AUTOMATIC RECORDING OF ACTION SPECTRA OF PHOTOBIOLOGICAL PROCESSES, SPECTROPHOTOMETRIC ANALYSES, FLUORESCENCE MEASUREMENTS AND RECORDING OF THE FIRST DERIVATIVE OF THE ABSORPTION CURVE IN ONE SIMPLE UNIT
Authors: HALLDAL PER
Published: January 2008

Abstract— A compact, rugged and simply constructed instrument has been designed which measures action spectra of photosynthesis by delivering equal numbers of quanta between 400 and 720 nm to a sample placed upon the cathode of an oxygen sensor. The absorption spectrum is measured delivering equal numbers of quanta over the spectrum to a sample placed directly above a photoreceiver that has been adjusted in wavelength sensitivity to function as a quantum counter. All the details that are recorded by conventional high precision spectro‐photometers for samples with relatively broad absorption bands (e.g. chlorophyll, carotenoids, phycobilins and living material such as algal suspensions) are resolved by the instrument. Corrected excitation spectra of fluorescence are obtained with the same instrument. Likewise the first derivative of the absorption curve may be scanned. Such recordings amplify details in the absorption spectrum, and they are particularly useful in analyses of small changes in slope. The functions described above may be operated separately or combined. The instrument has a total weight of about 10 kg, and the dimensions are ca. 60 × 40 × 30 cm. It is constructed for use in field laboratories and on board research vessels, and also for courses in biology where the principles behind photobiological analyses are illustrated. It is possible that a device of this type could be used for investigations of photosynthesis on other planets.
EFFECT OF MERCAPTAN ON PHOTOREDUCTION OF ACETONE. NON‐REPAIR HYDROGEN TRANSFER REACTIONS†
Authors: COHEN SAUL G. , AKTIPIS STELIOS , RUBINSTEIN HARRY
Published: January 2008

Abstract— Ultraviolet (u.v.) irradiation of solutions of benzhydrol in acetone leads to formation of ‐2‐propanol, benzpinacol and some benzophenone, apparently from the free radicals (CH3)2COH, II, and (C6H5)2COH, I. 2‐Propanol is formed more rapidly and benzophenone is formed to a much larger extent and persists longer when the solution contains mesityl mercap‐tan, as radical II is reduced by mercaptan and radical I is oxidized by thiyl radical. The same hydrogen atom transfer reactions, which retard by a repair mechanism the photoreduction of benzophenone by 2‐propanol, accelerate and alter the course of photoreduction of acetone by benzhydrol. Irradiation of acetone leads to 2‐propanol, and this is formed more rapidly in the presence of mercaptan. Irradiation of benzophenone in acetone leads to no apparent reaction. The courses of reaction of the several systems are discussed.
THE FLUORESCENCE EXCITATION SPECTRUM OF QUININE BISULFATE
Authors: GILL JAMES E.
Published: January 2008

Abstract— A new measurement of the fluorescence excitation spectrum of chromatographically homogeneous quinine bisulfate has been made using a spectrometer offering high resolution and high sensitivity. Comparison of this spectrum with the absorption spectrum of the compound indicates that its quantum yield is independent of the wave number of the exciting light within ± 5 per cent for 2.57 μ‐lv 5.0μ‐1.
FREE RADICALS PRODUCED IN A RIGID SOLUTION OF TRYPTOPHAN BY A BIPHOTONIC PROCESS
Authors: STEEN H. B.
Published: January 2008

Abstract— Free radicals were trapped by irradiation of tryptophan in an ethylene glycol/water glass with 250 nm U.V. light at 77°K. The ESR‐spectrum was attributed to approximately equal amounts of trapped electrons and ethyl radicals. The electrons could be transformed into the ethyl type radicals by heating or bleaching with near u.v. or visible light. The quantum yield of trapped radicals increased with increasing intensity of the irradiation by more than one order of magnitude over the range of intensities studied. A kinetic model was formulated on the assumption that the radicals were produced by the successive absorption of two light quanta, the absorption of the first giving rise to a transient intermediate which subsequently absorbs a second quantum to produce the radicals. The experiments confirmed the applicability of this model to the present case. The decay time obtained for the intermediate was 6.8 sec which equals the phosphorescence decay time of tryptophan under similar conditions, indicating that the intermediate involved was the lowest triplet level of this molecule. The absorption cross section of this intermediate at 250 nm with regard to the formation of trapped radicals was found to be 8000 l./mol cm.
ESR TRIPLET SPECTRA OF ACRIDINE DYES
Authors: Schmidt H.
Published: January 2008

Abstract— The triplet states of some acridine dyes (proflavine, acriflavine, acridine yellow, acridine orange, ethacridine (Rivanol), benzoflavine), dissolved in a dimethylformamide/water matrix were investigated at 90°K by ESR. Zero‐field splitting parameters were calculated from the ESR spectra. The relationship between the zero‐field splitting and the distribution of the spin‐density of the electrons of the triplet state of the acridine derivatives is discussed.
ON THE PHOTODECOMPOSITION OF CHLOROPHYLL IN VITRO ‐I. REACTION RATES*
Authors: JEN J. J. , MACKINNEY G.
Published: January 2008

Abstract— Chlorophyll solutions are irreversibly bleached by light in the presence of oxygen. The action spectra parallel the absorption spectra for both chlorophyll a and b. The reaction is of second order with a Q10 of 1.26. The reaction rates for chlorophylls a and b are of the same order of magnitude. Depending upon the light source, the initial rate for chlorophyll a is slightly higher, by a factor of 1.15 to 1.30. The rate for pheophytin is lowe 3 by several orders of magnitude. No pheophytin has been detected in the reaction products of the irradiated chlorophyll solutions in the absence of water.
THE MECHANISM OF PHOTOCHEMICAL ADDITION OF CYSTEINE TO URACIL AND FORMATION OF DIHYDROURACIL
Authors: JELLINEK T. , JOHNS R. B.
Published: January 2008

Abstract— A proposed mechanism for the photochemical addition of L‐cysteine to uracil with the concurrent formation of dihydrouracil is shown to proceed through the triplet excited state of uracil which can abstract hydrogen atoms from cysteine to form dihydrouracil. This triplet state is the same one as that leading to photodimerization. The thiyl radicals generated add to ground state uracil molecules. The data permit a re‐evaluation of the quantum yield for intersystem crossing of uracil in water which shows dimerization in aqueous solution to have a maximum efficiency of 56 per cent. The formation of the cross‐adduct and dihydrouracil may be sensitized but the efficiency of the reaction is related to the ability of the sensitizer to be photoreduced and not to its triplet energy.
ENERGETICS OF PHOTOPHYSICAL PROCESSES IN CHLOROPHYLL‐LIKE MOLECULES
Authors: GRADYUSHKO A. T. , SEVCHENKO A. N. , SOLOVYOV K. N. , TSVIRKO M. P.
Published: January 2008

Abstract— The values of the absolute quantum yields of fluorescence and of intersystem crossing have been obtained for porphin and its derivatives by methods based on relative measurements involving flash photolysis. For a given compound the sum of these quantum yields is unity within experimental error which shows that the energetics of the molecules investigated is determined by competition of only two processes, viz., fluorescence and intersystem crossing, while internal conversion plays a negligible role. The values of the corresponding transition probabilities have been determined with the help of phase‐fluorometric measurements. The dependence of the transition probabilities on molecular structure is discussed.
CONTRIBUTION A L'ETUDE DE LA LUMINESCENCE DIFFEREE DE COLORANTS EN MILIEU RIGIDE. PHOTOIONISATION DE LA FLUORESCEINE DANS L'ACIDE BORIQUE PAR UN PROCESSUS A DEUX PHOTONS
Authors: LESCLAUX ROBERT , OHAYON SYLVAIN , JOUSSOT‐DUBIEN JACQUES
Published: January 2008

Abstract— A study of the delayed luminescence and thermoluminescence of fluorescein and others dyes in boric acid glass gives evidence of photoionisation of these compounds. To account for the energetic aspect of the photoionisation, a two photon process involving solute‐solvent proton exchange is proposed. The participation of the heterogeneous structure of the glass in the mechanism of the photoionisation is confirmed.
NUMBER AND DISTRIBUTION OF CHROMOPHORE TYPES IN NATIVE PHYCOBILIPROTEINS
Authors: DALE R. E. , TEALE F. W. J.
Published: January 2008

Abstract— Fluorescence lifetimes and absolute quantum yields of a number of chromatographically pure phycobiliproteins have been determined. In conjunction with absorption, fluorescence emission and polarization spectra, these data were used to calculate the number of different types of chromophore, sensitizing and fluorescing, per chromoprotein.

To characterize the spatial distributions of the chromophores, the observed emission anisotropies were compared with those calculated from models, using the Förster transfer mechanism and the Jablonski ‘active sphere’ approximation. The experimental values are more consistent with surface locations for the fluorescing chromophores rather than with their distribution throughout the volume.

Theoretical efficiencies of transfer between sensitizing and fluorescing chromophores on the same macromolecule are consistent with those observed. The transfer efficiency from phycoerythrin prosthetic groups to chlorophyll a compared with that for transfer via phycocyanin indicates that the latter process is probably the favoured migration route.
RADIATIVE AND NON‐RADIATIVE LOSSES IN THE RETINOL POLYENES
Authors: DALLE JEAN PAUL , ROSENBERG BARNETT
Published: January 2008

Abstract— The radiative fluorescence lifetimes of the all‐trans, 9 cis and 13 cis retinol, have been measured at various temperatures, and in various solvents. The comparison of these results and of the data calculated from the absorption spectra using the Strickler and Berg equation shows that the transition probabilities are at least one hundred times lower for the radiative emission than for the absorption. Such a discrepancy, which is a general property of the polyenic structure, is closely related to the magnitude of the shift between absorption and fluorescence spectra. We interpret the observed elongation of the radiative fluorescence lifetimes and the temperature dependence of the radiative transitions in the case of all trans retinol as being due to the fact that only the lowest vibrorotational sublevels of 1S1, have a reasonable radiative transition probability: the temperature dependence of the radiationless transitions is considered to be due to the existence of a non radiative decay pathway at 550cal/mole above the ‘0’ level.
PHOTOREACTIVATION OF KILLING IN STREPTOMYCES: ACTION SPECTRA AND KINETIC STUDIES*
Authors: JAGGER JOHN , TAKEBE HIRAKU , SNOW JEANNE M.
Published: January 2008

Abstract— An action spectrum was obtained for photoreactivation of killing (PR) of Streptomyces griseus conidia. This spectrum shows a major peak around 436 nm, originally observed by A. Kelner, and a secondary peak at 313 nm not previously reported. The rate of PR shows a strong dependence upon temperature and dose rate of the PR light at 436 nm, but this decreases to only a slight dependence upon these parameters at 313 nm. These findings suggested that PR at 436 nm in this organism is of the usual photoenzymatic type, but that PR at 313 nm might be of a different kind.

A mutant (PHR‐1) of S. griseus was found that shows only a narrow range of PR (roughly 310–400 nm) with a single peak at 313 nm. The PR efficiency was lower than for wild type and the PR sector not greater than one‐half that of wild type. This PR shows no temperature dependence. Essentially similar behavior was observed with wild‐type Streptomyces coelicolor. These findings show that at least some of the PR at 313 nm is a separable phenomenon. It is therefore unlikely to involve a mechanism identical to that at 436 nm.

The nature of PR at 313 nm in Streptomyces is not known. If it is enzymatic, it is remarkable in having little or no dependence upon temperature and dose rate. Absence of photoprotection and liquid‐holding recovery indicate that it is not indirect PR. Some of it (that part exhibited by S. griseus PHR‐1 and S. coelicolor) might result from a direct photochemical action on DNA.
THE PHOTOCHEMICALLY INDUCED REACTIONS OF SULFUR DIOXIDE WITH ALKANES AND CARBON MONOXIDE*
Authors: TIMMONS RICHARD B.
Published: January 2008

Abstract— The gas phase photochemical reactions of SO2 induced by 3130 Å radiation have been studied in the presence of added alkanes or added CO. The quantum yields obtained in the reactions with the low molecular weight alkanes employed are lower than those obtained by previous workers. The quantum yields were found to be pressure dependent increasing slowly with increasing pressure. A stoichiometric ratio of one SO2 removed per molecule of hydrocarbon consumed was observed only under experimental conditions of [SO2] < [RH]. For reaction mixtures where [SO2] < [RH] the ratio of [SO2]/[RH] reacted always exceeded unity. The quantum yields decreased slightly with increasing temperature. In all the alkane reaction systems studied, the deposition of viscous, nonvolatile reaction products was observed. In the experiments with added CO, the quantum yields were computed with respect to the rate of CO2 formation. At 25°C and equal pressures of SO2 and CO, φco2 was observed to be 0.005 and it decreased slightly with increasing temperature. The results obtained are interpreted in terms of the sulfoxidation of the alkanes and the oxidation of CO proceeding by way of a 3SO2 reaction intermediate.
ABSORPTION BAND SHAPE AND EMISSION IN RHODOPSIN†
Authors: ROSS ROBERT T.
Published: January 2008

Abstract— –The Planck law relationship between absorption and emission spectra is applied to the spectral sensitivity curve of human rod vision, assumed to be equivalent to the absorption spectrum of the visual pigment rhodopsin, to compute a hypothetical emission spectrum for rhodopsin. When 17, 100 cm‐1 is used as the reflection axis, the mirror image of this hypothetical emission substantially matches the activation spectrum over 2500 cm‐1. The predicted emission increases exponentially at long wavelengths, in contrast to published observations of fluorescence at 580 nm; this discrepancy, and an estimate of excited state lifetime based on the Planck law theory, suggest that emission occurs from a meta‐stable vibrationally‐excited state. The exceptionally slow falloff in absorption at long wavelengths is explained as being due to the smaller dependence of potential energy on angle of twist about bonds in the polyene chain in the lowest π, π* singlet state of rhodopsin than in its ground state; a model assuming six or seven essentially flat vibronic modes in the excited state accurately fits the observed action spectrum.
PHOTOPRODUCTS OF BROMOURACIL‐LABELED DNA AND THE STRUCTURE OF 5‐BROMODEOXYURIDYLYL‐(3' → 5')‐THYMIDINE PHOTOPRODUCT
Authors: PETER HEINRICH H. , DREWER ROBERT J.
Published: January 2008

Abstract— –An attempt was made to identify some of the ultraviolet (u.v.) photoproducts of 5‐bromouracil‐labeled DNA (BrU‐DNA). Two synthetic dinucleotides, 5‐bromodeoxyuridylyl‐(3' →5 ')‐thymidine (BrdUpT) and 5‐bromodeoxyuridylyl‐(3' → 5')‐deoxycytidine (BrdUpdC), were prepared. Each gave a single u.v. photoproduct which in turn gave a single acid hydrolysis product. 2‐14C‐BrU‐DNA. prepared from E. coli B3, was irradiated (275–280 nm), hydrolyzed, and paper chromatographed in four systems. Comparison with the two synthetic photoproducts showed that if present at all, BrdUpT and BrdUpdC photoproducts could account for no more than 10 and 3.5 per cent respectively of the total photoproducts. At 55 per cent conversion of BrU into photoproducts, the major 14C‐photoproduct was uracil (78 per cent); the remaining 22 per cent was made up of at least six products, three of which were reversed by 232 nm irradiation.

The debrominated cyclobutane structure proposed by Haug for BrdUpT photoproduct has been shown to be incorrect. It was found to contain one atom of bromine per molecule. On the basis of nuclear magnetic resonance and u.v. spectra, two possible structures are proposed for the photoproduct, each containing an eight‐membered ring.
PHOTOREACTIONS ASSOCIATED WITH IN VITRO HEMOLYSIS IN ERYTHROPOIETIC PROTOPORPHYRIA*
Authors: HSU JOSEPH , GOLDSTEIN BERNARD D. , HARBER LEONARD C.
Published: January 2008

Abstract— –Photohemolysis of erythrocytes. from patients with erythropoietic protoporphyria results from damage to the cell membrane following photoexcitation of the protoporphyrin molecule by 400 nm radiation. Photochemical reactions were assessed for their roles in initiating cell destruction in an in vitro model in which erythrocytes from patients with erythropoietic protoporphyria were irradiated. Electron transfer properties were demonstrated using 2,3,6‐trichloroindophenol as an electron acceptor. Photohemolysis of these abnormal cells is due to cell membrane damage initiating colloid osmotic hemolysis. Additional data are offered demonstrating that this type of photohemolysis is oxygen‐dependent, associated with peroxide formation, and preceded by increased osmotic fragility. An hypothesis explaining the interrelationship of the photochemistry of protoporphyrin with the photobiologic observation of hemolysis is offered.