bluuebunny/crossref_metadata_2025_split huggingface dataset:
EVIDENCE THAT THE ELECTRIC VECTOR GOVERNS LIGHT ABSORPTION IN VISION, PHOTOTROPISM AND PHOTOTAXIS*
Authors: Jaffe L. 
Published: January 2008

SummaryIt is shown that it is the electric, rather than the magnetic, vector which largely or entirely governs the absorption of light in instances of vision (the vertebrate rod), phototropism (spores and eggs of various lower plants), and phototaxis (chloroplast rotation in a green alga). The argument applies simple considerations of symmetry to data interpretable as a measure of the anisotropy of light absorption by the arrays of photoreceptor molecules in each of these cases.
PHOTOCHEMISTRY OF CYTOSINE NUCLEOSIDES AND NUCLEOTIDES—III. MONO‐ AND DI‐ METHYLAMINO ANALOGUES
Authors: Fikus M. , Wierzchowski K. L. , Shugar D. 
Published: January 2008

SummaryAn investigation has been made of the photochemical (2537 A) behaviour in aqueous medium of mono‐ and dialkylamino substituted cytosines, their nucleosides and nucleotides. The principal reaction in all instances is photohydration, the photoproducts being the 5‐hydro‐6‐hydroxy derivatives of the parent compounds, as for cytosine analogues with a free amino group. Alkylation of the amino group results in a decrease in quantum yield for photoproduct formation of two orders of magnitude; but the resulting photoproducts are much more stable. In the case of the free bases, the increased stability of the photo‐products has made it possible to confirm unequivocally the previous proposal that the photoproducts of cytosine and 1 ‐methylcytosine are also the hydrated derivatives. In the case of the glycosides, the stability of the photoproduct of 2′: 3′‐0‐isopropylidene‐mono‐methylaminocytidine is such as to offer a possibility of a direct NMR check as to whether the hydroxyl of the photo‐adduct is on the 6 position of the pyrimidine ring.The enhanced stability of the protonated forms of the photoproducts has been interpreted in terms of the conformation of the cytosine ring. The absorption spectrum of 173‐dimethylcytosine in acid medium supports the contention that protonation of the cytosine ring occurs on the N, ring nitrogen.Etherification of phosphoester hydroxyls was utilized to examine in greater detail the role of the phosphate groups in the stability of the photoproducts of cytosine nucleotides as a function of pH. The results are all discussed in relation to the photochemistry of nucleic acids.
INFLUENCE OF LIGHT ON THE RESISTANCE OF CELLULAR PROTOPLASMIC STREAMING IN PLANTS TO 2,4‐DINITROPHENOL
Authors: Lomagin A. G. , Antropova T. A. 
Published: January 2008

Abstract— Visible light sharply increases the resistance to 2,4‐dinitrophenol of the protoplasmic streaming in cells of green leaf disks of Tradescantia flurninensis Vell. and Campanula persicifolia L.Under the influence of light an increase in the resistance of the cellular semi‐permeability of Tradescantia fluminensis to 2,4‐dinitrophenol is also observed.Light produces no effect on the resistance to 2,4‐dinitrophenol of protoplasmic streaming in scale cells of Allium cepa L. bulbs, nor in the sensitivity of ciliated epithelium movement in the mucosus of the mouth cavity of the frog (Ram temporaria L.) to this inhibitor.Light does not produce changes in the protoplasmic streaming resistance of Tradescctntia fluminensis cells to sodium azide.Aeration eliminates the protective effect of light on plant cells injured by 2,4‐dinitrophenol. Maximum increase in the protoplasmic streaming resistance of Campanula persicifolia cells to 2;4‐dinitrophenol is attained at 1000 lux, which is considerably lower than the photosynthetic light saturation. Further increase or decrease in light intensity leads to a decrease in the resistance of protoplasmic streaming to this poison.It is suggested that the protective action of light on cells of green leaf disks injured by 2,4‐dinitrophenol, is due to the photo‐reduction of 2,4‐dinitrophenol to 2‐amino‐4‐nitrophenol. As experiments have shown the toxicity of 2‐aniino‐4‐nitrophenol is insignificant as compared to that of 2,4‐dinitrophenol.
KONSTRUKTION UND ERPROBUNG EINER LICHT‐BOGENTEMPERIERBAREN QUECKSILBERNIEDERDRUCKLAMPE
Authors: Kittler L. , Schweiss H. 
Published: January 2008

Abstract— A new low pressure mercury lamp was constructed and described in detail. The silica‐lamp surrounds the analytical vessel and has two water‐cooled circuits. The first one for cooling the mercury electrodes and the second one for cooling of the arc. The temperature dependence of the arc intensity was studied and discussed.The lamp was calibrated for two wavelengths (253·7 nm and 365 nm) by using an u.v.‐standard lamp. The effective intensity within the analytical cell has a value of 6·7 × 10‐6 Einstein cm‐2 min‐l.
PHOTOSYNTHETIC EFFICIENCY OF A PHYCOCYANIN‐LESS MUTANT OF CYANIDIUM*
Authors: Volk S. L. , Bishop N. I. 
Published: January 2008

Abstract— 1. R‐II is a u.v. induced mutant of cyanidium caldarium which lacks the major accessory pigment phycocyanin.2. Loss of phycocyanin does not impair photosynthesis or the Hill reaction.3. The action spectrum for the quantum yield indicates an efficiently operating photosynthetic mechanism which is shifted in peak efficiency toward longer wavelengths when compared to the wild‐type spectrum. The red drop is also shifted toward the far red in R‐II.4. Although 30 per cent enhancement was obtained in wild‐type Cyanidium, no enhancement was observed when phycocyanin was absent.5. A pigment absorbing at 720 nm has been observed and may possibly represent a chlorophyll‐phycocyanin complex.
STRUCTURE OF DYE AGGREGATES AND THE MECHANISM(S) OF PHOTOSENSITIZATION OF AgBr*,†
Authors: Bird George R. , Zuckerman Bernard , Ames Allan E. 
Published: January 2008

Abstract— This paper reports the present conclusions of an extended investigation on photo‐sensitization of silver bromide. A general molecular packing structure for dye aggregates on the AgBr (111) surface is proposed. This structure, along with the observed spectral absorption displacements of small aggregates, is used to elucidate the phenomena of antisensitization and supersensitization. Supersensitization is seen as a partitioning of large dye aggregates into small aggregates by a deliberately added second component or by gaps between the aggregates. This partitioning isolates antisensitizing dye in a small fraction of the aggregates and minimizes its effect. The smallest aggregates are least likely to contain an antisensitizer, and show the highest quantum efficiency for photoconductivity and photographic action. Photoconductivity measurements establish that supersensitization occurs before the electron appears in the AgBr phase.The question of direct electron injection vs. energy transfer as mechanisms for AgBr photosensitization is examined in terms of radiationless transfer to surface Ag2S on AgBr. The absorption of surface Ag2S is shown to be adequate for acceptance of Förster transfer from the dye, and surface Ag2S is known to be photographically active. However, this mechanism is inefficient, and inadequate to account for observed high efficiency infrared sensitization. Direct electron injection is seen as the more probable mechanism for efficient dye sensitization of AgBr.
SENSIBILISIERTE PHOTOOXIDATION DURCH METHYLENBLAU, THIOPYRONIN UND PYRONIN‐I MITTEILUNG: FLASH‐PHOTOOXIDATION VON p‐DIAMINOTOLUOL
Authors: GOLLMICK F. A. , BERG H. 
Published: January 2008

AbstractThe dye (F)*sensitized photooxidation of p‐diaminotoluene (RH2) was examined by flash‐spectroscopy and the mechanism was elucidated. The first chemical reaction is the generation of two free radicals from the triplet dye and the hydrogen donor. These radicals may react in several ways without oxygen:or additionally with oxygen:The connection of this mechanism with photodynamic action is discussed.
ACTION OF PHOTOREACTIVATING LIGHT ON PYRIMIDINE HETEROADDUCT IN BACTERIA*
Authors: IKENAGA M. , PATRICK M. H. , JAGGER J. 
Published: January 2008

Abstract— In stationary‐phase Escherichia coli B/r, photoreactivation (PR) at 313 nm of ultraviolet (u.v.) killing is inefficient compared with PR at 405 nm, and can be explained solely by photoenzymatic reversal of pyrimidine dimers.In Staphylococcus epidermidis, PR shows a maximum at 313 nm, suggesting that this organism shows the Type III PR proposed by Jagger et al.[5] for Streptomyces strains. Reversal of pyrimidine dimers is not sufficient to explain this PR. The mechanism of Type III PR remains unknown.With both S. epidermidis and E. coli B/r, the amount of uracil–thymine heteroadduct in DNA hydrolysates decreases if the cells are given a post‐u.v. treatment at 313 nm, but no decrease is observed if the post‐u.v. treatment is at 405 nm. The biological significance of this adduct and of its removal is not clear. It may play a role in Type III PR.
ELECTRON SPIN RESONANCE STUDIES OF THE EXCITED TRIPLET STATES OF DL‐5‐HYDROXY‐TRYPTOPHAN, 5‐HYDROXYINDOLE, 6‐HYDROXY‐NICOTINIC ACID, INDOLE AND HIPPURIC ACID‡,‡
Authors: CHEN TZENG‐MING 
Published: January 2008

Abstract— The electron spin resonances of the metastable triplet states of DL‐5‐hydroxy‐tryptophan, 6‐hydroxynicotinic acid, and other related compounds have been observed in various glasses at 77°K. These compounds are biologically interesting in connection with photochemical processes. The Δm= 2 transitions were observed and the spin‐spin interaction parameter (D2+ 3E21/2 was determined. However, for indole, it was also able to observe the Δm= 1 transitions from which D and E were determined separately. From the values of (D2+ 3E2)1/2, D and E whenever possible and from the decay times of the triplet states, it was possible to characterize the lowest triplets as π—π* states in all cases.Studies of the pH dependence of DL‐5‐hydroxytryptophan, 5‐hydroxyindole, and 6‐hydroxynicotinic acid indicate that the unionized molecule exhibits a resonance different from that of the related ion with a proton removed from the phenolic hydroxyl group.The zero‐field splitting parameters D* and the lifetime of the triplet states have also been measured in various glasses and in Lucite. Both temperature and the specific nature of the host media affected the values of these parameters.
DECOMPOSITION PHOTOSENSIBILISEE DE SOLVANTS ORGANIQUES A 77°K PAR UNE AMINE AROMATIQUE, LA DIPHENYLPARAPHENYLENEDIAMINE*
Authors: CHACHATY C. , SCHOEMAKER D. , BENSASSON R. 
Published: January 2008

Abstract— –By e.s.r. we have studied the photoexcitation of an aromatic amine to its triplet state at 77°K, its photoionization to a radical cation and the simultaneous formation of solvent radicals proceeding from the photosensitization of the organic glassy matrix.In the case of methanol and ethanol matrix we observe approximately one solvent radical per solute radical cation. In the case of isopropanol and methyltetrahydrofuran we find respectively three and two solvent radicals per solute radical cation. The results suggest two possible processes of photosensitization. By successive absorption of two photons, the amine reaches an excited triplet state which is able either to dissociate giving one electron and one cation radical or to transfer its energy to the solvent, this last being decomposed.It is assumed that in the case of methanol and ethanol, the radicals from the solvent are only formed by reaction on the matrix by the released electron, whereas in the case of isopropanol and methyltetrahydrofuran, the second process is prevalent or exclusive.
EXCIPLEX STUDIES‐IV. RADIATIVE AND NON‐RADIATIVE RELAXATION OF THE FLUORESCENT STATE OF INDOLE†
Authors: WALKER M. S. , BEDNAR T. W. , LUMRY R. , HUMPHRIES F. 
Published: January 2008

Abstract— Rate constants for both radiative and non‐radiative relaxation of the fluorescent state of indole and several methyl‐indoles in solution have been calculated from fluorescence lifetime and quantum yield values.Radiative relaxation for indoles is solvent dependent while non‐radiative relaxation is attributed to at least two processes, one of which is both solvent and temperature dependent. The latter process measured in aqueous solvents manifests a pattern of compensation of activation enthalpy by activation entropy with an isokinetic temperature for indole of 283°K.A quantitatively consistent description of the excited‐state behavior of 1‐Me‐indole in both free and exciplex state is provided. Small deviations in fluorescence parameters for indole suggest a more complicated set of events.
PHOTOCHEMICAL REACTIONS OF AROMATIC KETONES WITH NUCLEIC ACIDS AND THEIR COMPONENTS–III. CHAIN BREAKAGE AND THYMINE DIMERIZATION IN BENZOPHENONE PHOTOSENSITIZED DNA*
Authors: CHARLIER M. , HELENE C. , CARRIER W. L. 
Published: January 2008

Abstract— Excitation of benzophenone in the presence of calf thymus and E. coli DNA leads to photosensitized damages to the macromolecule. Two main reactions are observed: thymine dimerization and chain break formation. Benzophenone photosensitized chain breaks are also observed in polyadenylic acid.The melting temperature of DNA decreases with the duration of irradiation.Under our experimental conditions, the ratio of the yields of dimers and single‐chain breaks produced in DNA is about 1. Photosensitized damage to deoxyribose residues leading to chain breakage is shown to be similar to that produced by X or γ ray irradiation. The oxygen effect upon chain break production is studied and discussed in relation with its effect upon intermediate species.Thymine dimers are formed following energy transfer from benzophenone in its triplet state. In previous flash‐photolysis studies we showed that benzophenone in its triplet state reacts with water molecules to give ketyl and OH radicals. Ketyl radicals are not involved in reactions with DNA. It is proposed that OH radicals produced in the above reaction are responsible for the production of single‐chain breaks by attack on the deoxyribose residues.
AUTOMATIC SCANNING SPECTROPHOTOMETER WITH PUNCH TAPE OUTPUT FOR BIO‐APPLICATIONS
Authors: SEIM T. , PRYDZ S. , HOLTSMARK T. 
Published: January 2008

Abstract— An automated scanning spectrophotometer has been constructed for the measurement of color‐vision test stimuli and various types of luminescence. Recorder and paper tape output data have been provided. Processing of the spectral information is performed on a CDC 3300 computer.Photoelectric detection is employed. An inexpensive Jarrel‐Ash 0.25 m,f/3.6 Ebert type monochromator is employed with two gratings, blazed for 300 and 600 nm, respectively.The spectral sweep range can be easily set by electromechanical registers, as can the number of sweeps required. Photon numbers are integrated by a counter over 5 nm blocks, and this procedure sets the limit of resolution. At present the spectral range is from 400 to 800 nm. By calibration against an ultraviolet‐emitting standard lamp the useful range can easily be extended downwards to 250 nm.Computer programs have been written which add several spectra when these are faint and produce a mean spectrum in the form of listed and plotted output. The mean noise level is subtracted. Subprograms have been made for the smoothing of poor spectral data where noise predominates and for the correction for stray light and grating ‘ghosts’ in the monochromator. A program has been made which performs colorimetric analyses of light sources, spectral filters, and pigmented surfaces. The dominant wavelength and the excitation purity are computed and given in CIE chromaticity coordinates and three‐stimulus values.
PRIMARY PHOTOCHEMISTRY OF PHOTOSYNTHESIS Report on a Conference held at Argonne National Laboratory, November 1971
Authors: LOACH PAUL , KATZ JOSEPH J. 
Published: January 2008

SummaryIn conclusion, the conference was judged to be extremely useful for the 230 persons who attended, and all departed with an optimistic enthusiasm about the certainty of progress in this field over the next 5 to 10 years. A statistic that perhaps represents a new record and should be shared to underscore the significance of the meeting to researchers in this area of photosynthesis is that out of 59 scheduled speakers all were in attendance and only one had to be replaced because of a commitment to take part in ceremonies for the 150th anniversary of a famous university in the East. From our experience with the form of the meeting, we feel that the open attendance but limited subject concept is a highly desirable meeting form and should be used for most scientific meetings.
PHOTOCHIMIE DES ACIDES AMINES AROMATIQUES EN SOLUTION ‐ I. dl‐PHENYLALANINE, dl‐TYROSINE ET l‐DOPA
Authors: HASSELMANN C. , LAUSTRIAT G. 
Published: January 2008

Abstract— The action of ultraviolet radiation on dl‐phenyldanine, dl‐tyrosine and l‐dopa has been studied in dilute aqueous solutions (10‐2M–5 × 10‐3M). Irradiation was performed in nitrogen or in air, at a wavelength of 254nm. The photoproducts of low molecular weight (amino acids, carboxylic acids, amines) were isolated either by chromatography on an ion exchange column or by thin‐layer chromatography and identified mainly by ultraviolet absorption and staining with ninhydrin. The isolation of photopolymers was carried out by chromatography on a Biogel column; identification of these photoproducts was mainly achieved by ultraviolet and infrared spectroscopy.With phenylalanine, which is the most photosensitive amino acid, the principal reaction results in splitting of the side chain, giving alanine, glycine, and four other amine compounds whose structure has not been determined. In air, additional minor products resulting from photooxydation are obtained: ortho, meta and paratyrosine. Traces of phenylethylamine were isolated after irradiation in an inert atmosphere. The polymers produced under air and nitrogen are similar. They probably result from rearrangement of aromatic radicals formed by splitting of the side chain.Tyrosine and dopa, irradiated in air, yield mainly melanin; before polymerization, tyrosine is first converted into dopa. In a inert atmosphere, these aromatic aminoacids also polymerize, giving monophenolic and biphenolic compounds with structure close to that of melanin. The biphenolic polymer (thus obtained from dopa) shows the properties of a leuco derivative of melanin. The monophenolic polymer can be converted into melanin by the combined action of oxygen and ultraviolet radiation. Other reactions give only minor products: parahydroxy‐phenyllactic acid and 3,4‐dihydroxyphenyllactic acid by deamination‐hydroxylation of tyrosine and dopa (in air): meta and paratyrosine by dehydroxylation of dopa, either in air or in nitrogen.
INHIBITION OF THE extra GENE‐DEPENDENT BRANCH OF THE DNA EXCISION REPAIR SYSTEM IN ESCHERICHIA COLI K‐12 BY 2, 4‐DINITROPHENOL
Authors: Schueren Emmanuel Van der , Smith Kendric C. 
Published: January 2008

Abstract— Ultraviolet (UV)‐irradiated E. coli K‐12 wild‐type cells were sensitized by a post‐irradiation treatment with 10‐2M 2, 4‐dinitrophenol (DNP). This effect was not seen in strains carrying a uvr mutation, suggesting that DN P interferes with the excision repair process. The polA strain was sensitized to the same extent as the wild‐type strain, while the exrA strain was not affected by DNP treatment.Recombination deficient strains (recA, recB and recA recB) were protected by DNP treatment after UV irradiation. This protection was abolished by the addition of a uvr mutation (i.e., in strains recA uvrB and recB uvrB).Alkaline sucrose gradient sedimentation studies showed that DNP treatment interfered with the rejoining of DNA single‐strand breaks induced by the excision repair process. This interference was apparently specific for the exr gene‐dependent branch of the uvr gene‐dependent excision repair process, since the uvr and exr strains were not sensitized while the wild‐type and polA strains were sensitized.
A LINEAR DICHROISM STUDY USING CHLOROPLASTS OF VARIOUS STRUCTURE and PIGMENT COMPOSITION
Authors: Faludi‐Dániel ÁGnes , Breton Jacques 
Published: January 2008

Abstract— The orientation of pigments was studied in maize chloroplasts of different granum content and pigment composition. Comparison of the linear dichroism (LD)t of granal and agranal chloroplasts exhibited differences in the chl a forms, Ca 670 and Ca 691. The chl b content of the chloroplasts appeared to have little effect on the LD spectra.In the LD spectra of carotenoid deficient mutant chloroplasts, the red band corresponding to oriented Ca 678 was considerably smaller than in those of normal chloroplasts. LD spectra of lycopenic chloroplasts revealed a band at 740 nm not present in the spectra of normal chloroplasts. Various signals of carotenoids observed in the LD spectra of carotenoid deficient mutant chloroplasts imply that the different carotenoids can be oriented in a different manner in the photosynthetic membrane.
STUDIES ON HOOK‐OPENING IN PHASEOLUS VULGARIS L. BY SELECTIVE R/FR PRETREATMENTS OF EMBRYONIC AXIS and PRIMARY LEAVES*
Authors: Caubergs R. , Greet J. A. De 
Published: January 2008

Abstract— Hook‐opening of etiolated bean seedlings was studied by inductive light pretreatments, selectively applied to the embryonic axis and to the primary leaves. Statistical analysis of the experimental results substantiated that hook unbending in intact plants is mutually influenced by both organs. When the leaves were excised immediately after their selective preirradiation, hook opening was the same as in the intact control series.Far red light could only fully reverse a red inductive effect when both light qualities were administered to the intact plant.When the cotyledons were removed prior to the light treatments the results did not change qualitatively. Our data indicate that a very precise, highly ordered biophysical recognition system of light signals exists in plants. The transmission of these signals between different organs is very rapid and phytochrome‐mediated.
CHEMILUMINESCENCE FROM THE OXIDATION OF AUXIN DERIVATIVES
Authors: Durán Nelson , Zinner Klaus , Baptista Roberto Casadei de , Vidigal Carmen C. C. , Cilento Giuseppe 
Published: January 2008

Abstract— The thiophenyl ester of indole‐3‐acetic acid and indole‐3‐acetonitrile produce chemiluminescence in aerated dimethylsulfoxide in the presence of potassium t‐butoxide. The emitter is the aromatic aldehyde. In the case of acetonitrile, the other product expected from the cleavage of an intermediate dioxetane, cyanate/isocyanate, has also been identified. Other auxins also chemiluminesce under similar conditions, but the emitters have not been properly identified.These systems are models for the peroxidase catalyzed oxidation of indole‐3‐acetic acid to indole‐3‐carboxaldehyde and as such support the earlier inference (Vidigal et al, 1975) that the excited aldehyde is generated in the enzymic process.An additional result is the observation of an exciplex between excited indole‐3‐carboxaldehyde and the thiophenylester of indole‐3‐acetic acid. This appears to be the first case of chemical generation of an exciplex by a route other than radical ion reaction, presumably by the dioxetane route.