bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRIPLET‐TRIPLET ENERGY TRANSFER IN P‐TRYPSIN 1 THE ROLE OF THE INDOLE TRIPLET IN THE ULTRAVIOLET‐INDUCED PHOTOLYSIS OF β‐TRYPSIN
Authors: Ramachandran N. , Ghiron C. A. 
Published: January 2008

Abstract—Detection of triplet‐triplet energy transfer in an aqueous solution of P‐trypsin is reported. This conclusion is based on the observation that a light excited phenolate side chain can sensitize the destruction of an adjacent indole side chain. The role that the indole triplet might play in the UV‐induced photolysis of /l‐trypsin is also investi‐gated. The results suggest that the UV (309 nm)‐induced inactivation of P‐trypsin is not caused by indole ring destruction but by the disruption of disulfide bonds without thiol formation.
FACTORS INFLUENCING THE NEAR‐UV EFFECT ON DNA IN THE PRESENCE OF 8‐METHOXYPSORALEN: RENATURABILITY OF DNA.
Authors: Fujita Hitoshi , Sano Miyaharu , Suzuki Kenshi 
Published: January 2008

Abstract—Factors affecting the near‐UV induced reaction of calf thymus DNA in the presence of 8‐methoxypsoralen were examined. DNA became more renaturable with increasing concentration of 8‐methoxypsoralen and fluence. Existence of paramagnetic ions, Mn2+, Co2+, or Ni2+, largely repressed the photoreaction. It was ascertained that the highest renaturability was attained by the illumination with light between 310 and 345 nm.
SEASONAL PHOTOSENSITIVITY OF BLEPHARISMA: THE ROLE OF TEMPERATURE
Authors: Glese Arthur C. 
Published: January 2008

Abstract—Red blepharismas (B. japonicum) in Pyrex test tubes exposed near noon to clear summer daylight are killed. If similarly exposed at dawn, they turn blue as the red pigment blepharismin is oxidized to oxyblepharismin. and they resist further exposure to daylight. Red blepharismas similarly exposed to sunlight at dawn in winter are killed. The experiments reported seek the reasons for the seasonal difference in photosensitivity and the way in which blepherismas survive winter.Red blepharismas (B. japonicum) exposed to visible and near ultraviolet (UV) radiation from two 4W coolwhite fluorescent lamps (5 Wm‐2; 2151ux) resist an 8h exposure between 15° and 34°C. turning blue. Blue and colorless blepharismas also resist 8h exposures to the light at 15° and 34°C. At 8°C both red and blue populations are killed, death appearing to result from deranged water regulation; colorless ones are not affected.Red blepharismas are killed by fluorescent light at 8° C even when the near‐UV radiation is largely excluded by a Corning glass filter; blue and colorless ones are not. The reds are also killed at all temperatures by sunlight filtered through Pyrex glass if exposed near noon on a sunny day. At temperatures above 8° C they are not killed by direct sunlight passed through glass if exposed at dawn, but they turn blue. Blepharismas in fluorescent light divide at the same rate as controls in the dark, but they get smaller.When exposed to sunlight at dawn, at temperatures above 8°C. blepharismas in Pyrex test tubes containing stones or fruiting spikes of grass, hid in the shade of these objects, apparently by random movements. If exposed under similar conditions near noontime, the majority failed to find cover and were killed. Blepharismas survive in summer by avoiding sunlight, in winter by encystment.Colorless protozoans Paraineciurn multimicronucleatum, Colpidium colpoda and Spirostomum teres resisted killing in summer sunlight and with fluorescent light at all temperatures tested.
THE DETERMINATION OF PERIODICITIES IN SHORT‐TERM TIME‐SERIES DATA IN THE PRESENCE OF HIGH FREQUENCY NOISE AND LONG‐TERM TREND
Authors: Hopkins D. W. , Deitzer G. F. , Wagner E. 
Published: January 2008

Abstract—The presence of periodicities in biological data may often be obscured by superposition of a background trend or high frequency oscillations. A method of least squares curve fitting was utilized to remove the trend in signal level. Subsequent removal of higher frequency noise utilizing smoothing convolution functions allows the determination of rhythmic components. A new “noise” convolution function gives a measure of the noise in data containing both signal and noise and allows the estimation of a limit above which an observed oscillation is considered significant. The effects of treating data with these convolution functions are discussed with reference to amplitude‐frequency response curves. The results of data analysis utilizing convolution functions are compared with results obtained utilizing a moving interval Fourier technique (Blume, 1965). The convolution analysis have the advantages that they are easily programmed and rapidly calculated by programmable calculators, give results relatively insensitive to the length of convolution interval, and allow estimation of the variation in period and amplitude of the rhythm investigated.
PHOTOCHEMICAL GENERATION OF REDUCED QUINONE CATALYSTS OF PHOTOSYSTEM I CYCLIC PHOTOPHOSPHORYLATION ACTIVITY
Authors: Robinson Howard H. , Yocum Charles F. 
Published: January 2008

Abstract—When reaction mixtures containing 9,10‐anthraquinone‐2‐sulfonate and chloroplasts poisoned with 3–(3,4‐dichlorophenyl)‐l, l′‐dimethylurea were illuminated with white light, photosystem I‐catalyzed cyclic photophosphorylation was observed. Illumination of identical reaction mixtures with red light produced no ATP synthesis. This phenomenon is due to photoreduction of the anthraquinone which is supported by the electron donor activity of Tricine buffer. The photoreduction reaction was used to generate reduced catalysts (anthraquinone sulfonate, menadione bisulfite) of photosystem I cyclic photophosphorylation activity. The rates of ATP synthesis obtained by this method (250–300 μmol/h‐mg chlorophyll) indicate that sulfonated quinones are efficient mediators of cyclic electron transport around photosystem I. Although the activity catalyzed by these compounds is highly sensitive to dibromothymoquinone, very little decrease in activity is observed with antimycin A.
SPECTRAL CHARACTERIZATION OF MONOMERIC C‐PHYCOERYTHRIN FROM PSEUDANABAENA W 1173 AND ITS α AND β SUBUNITS: ENERGY TRANSFER IN ISOLATED SUBUNITS AND C‐PHYCOERYTHRIN
Authors: Zickendraht‐Wendelstadt Barbara , Friedrich Josef , Rüdiger Wolfhart 
Published: January 2008

Abstract— Molecular weight determination by gel chromatography and analytical ultracentrifugation revealed that C‐phycoerythrin from Pseudanabaena W 1173 exists as the monomer ∝βat a concentration up to 7μM and as the dimer (∝β)2 at 40 μM. The purified subunits were monomeric species ∝ or β, respectively at 20 μM. Native monomeric C‐phycoerythrin was compared with the renatured subunits in a number of spectral properties: absorption spectroscopy including determination of molar extinction coefficients, fluorescence emission and excitation at 293 and 4 K, and fluorescence polarization. Whereas spectra of denatured subunits and denatured C‐phycoesythrin are identical, substantial changes occurred upon renaturation. Linear superposition of the absorption spectra of renatured subunits results in a curve identical with the absorption of native monomeric C‐phycoerythrin.The following conclusions were drawn: (a) Chromophore conformation is identical in renatured subunits and in native αβ monomer of C‐phycoerythrin. (b) In C‐phycoerythrin there are two fluorescing chromophores, degenerate in energy, one in the α‐ and the other in the β‐subunit and three sensitizing chromophores which differ in their energies and spectral shapes, (c) The energy transfer in C‐phycoerythrin occurs not only within but also between the subunits. (d) A weak fluorescence from sensitizing chromophores observed at low temperature (4 K) in the α‐subunit and in C‐phycoerythrin shows the limitations of the concept of sensitizing chromophores.C‐PE, C‐phycoerythrin; P, degree of polarization; R, degree of anisotropy; SDS, sodium dode‐cyl sulfate; s20, sedimentation coefficient
TRIPLET EXCITED STATE OF THE 4'5' PHOTOADDUCT OF PSORALEN AND THYMINE
Authors: Bensasson R. V. , Salet C. , Land E. J. , Rushton F. A. P. 
Published: January 2008

Abstract— The triplet‐triplet absorption spectrum of the 4'5' psoralen‐thymine mono‐adduct has been determined in water and methanol using the technique of laser flash photolysis. The extinction coefficient of the triplet was measured by the energy‐transfer method with retinol triplet as standard, and used to determine the singlet → triplet intersystem crossing quantum yield for 353 nm excitation. Reaction rate constants for mono‐adduct triplet with thymine and tryptophan were measured in water. Long‐lived transient absorptions detected after quenching the mono‐adduct triplet with thymine and tryptophan are assigned mainly to the corresponding mono‐adduct radical anion, whose spectrum was established in separate pulse radiolysis studies of the mono‐adduct in aqueous formate.The significant singlet → triplet quantum yields found for the mono‐adduct might be consistent with the involvement of triplet excited mono‐adduct in DNA cross‐link formation, as also may be the high reactivity obtained for the triplet with thymine. The initial quenching products observed resulted from a charge‐transfer reaction.
STEREOELECTRONIC PROPERTIES OF PHOTOSYNTHETIC AND RELATED SYSTEMS—VII. AB INITIO QUANTUM MECHANICAL CHARACTERIZATION OF THE ELECTRONIC STRUCTURE AND SPECTRA OF CHLOROPHYLLIDE a AND BACTERIOCHLOROPHYLLIDE a CATION RADICALS
Authors: Petke J. D. , Maggiora Gerald M. , Shipman Lester L. , Christoffersen Ralph E. 
Published: January 2008

Abstract— Ab initio configuration interaction wavefunctions and energies are reported for 29 doublet states and three quartet states of the cation radicals of ethyl chlorophyllide a (Et‐Chl a+) and ethyl bacteriochlorophyllide a (Et‐BChl a+).In Et‐Chl a.+ I the lowest excited doublet state D1 is estimated to lie 5220 cm‐1 above the ground state D0, with a negligibly small D1← D0 transition probability. The lowest quartet state, Q1, is estimated to lie 7980 cm‐1 above D1. The absorption spectrum up to 20,000cm‐1 is shown to consist primarily of numerous low‐intensity ‘background’ transitions, with transitions to D5 and D11 accounting for the observed peaks at 12,200cm‐1 and 17,500cm‐1, respectively. The large intense band at 25,000cm‐1 is due primarily to transitions to D22 and D23, with numerous lower‐intensity transitions to neighboring states.In Et‐BChl a.+ D1 is estimated to lie 7112 cm‐1 above D0, and Q, is approximately 5725 cm‐1 above D. A pair of states, D3 and D5, account for the absorption at 11,000 cm‐1, while another pair of states, D13 and D14, are associated with the broad, weak absorption near 20,000 cm‐1. The two prominent intense peaks at 23,700 cm‐1 and 27,700 cm‐1 are assigned to D23 and D28, respectively, while the shoulder located at 25,500cm‐1 is attributed to transitions to D24 and D26. As in Et‐Chl at, numerous background transitions are found throughout the spectrum.The π spin density distribution in D0 of both molecules is similar, with spin density found predominantly on the α‐carbon atoms. In both systems, approximately 65% of the π spin density in D1 is found on the methine carbon atoms, with the remainder found largely on the nitrogen atoms.
MULTIPLE EFFECTS OF UV RADIATION (265–330 NM) ON FUNGAL SPORE EMERGENCE
Authors: Owens Olga v. H. , Krizek Donald T. 
Published: January 2008

Abstract—We have investigated the influence of narrow‐band UV radiation, 265–330 nm. on germination of spores of the fungus Cladosporium cucumerinum Ellis and Arth., using a Xe arc lamp and filters. Reciprocity of time and dose rate was demonstrated when fungal spores were subjected to UV radiation at 325 nm but failed to hold at 265 nm. Based on these findings, data on fluence response, and partial action spectra, we propose that there are two biologically active sites in this organism that are affected by radiation between 265 and 330 nm and that might be influenced by changes in the stratospheric ozone layer: a short‐wave‐sensitive site (265–295 nm) and a long‐wave‐sensitive site (300–330 nm). Data obtained with narrow‐band interference filters confirmed previous reports of damage to nucleic acid from UV at 265–295 nm and in addition demonstrated significant inhibition by UV at 300–320 nm. Further studies of the 300 330 nm portion of the spectrum, using combinations of plastic and glass filters, showed that the influence of UV radiation in this region was primarily to produce a non‐photoreactivable delay in germ‐tube emergence.
POLAROGRAPHIC DETECTION OF AN ENDOGENOUS REDUCTANT GENERATED DURING FLASH ILLUMINATION OF CHLOROPLASTS
Authors: Jursinic Paul 
Published: January 2008

Abstract—A Joliot‐type polarographic electrode with the platinum surface biased 200 mV positive with respect to the Ag/AgCl junction was found to give a signal upon flash illumination of chloroplasts. The presence of either methyl viologen or ferricyanide as electron acceptors greatly enhanced the positivebias signal. By varying the electrode bias, a polarogram is obtained of this positive‐bias signal. A half‐wave reduction potential of 340 mV indicates that this signal is not due directly to superoxide (O‐2) nor the direct interaction of reduced methyl viologen or ferrocyanide with the electrode. Instead, the reduced exogenous acceptors act as intermediates in the generation of superoxide, and superoxide reduces an unidentified acceptor which is endogenous to chloroplasts, has a 340 mV redox potential, and gives rise to the positive bias polarographic signal. The extent of intersystem electron carrier oxidation can be changed by varying electrode bias with ferricyanide present. As the platinum is made more positive than 250 mV with respect to the Ag/AgCl junction, P700 becomes largely oxidized during 5 min dark adaptation.
INTERMEDIATES IN THE ROOM TEMPERATURE FLASH PHOTOLYSIS AND LOW TEMPERATURE PHOTOLYSIS OF PURINE SOLUTIONS
Authors: Arce R. , Jimenez L. A. , Rivera V. , Torres C. 
Published: January 2008

Abstract—The flash photolysis of purine in acetonitrile and in water at different pH was studied. The transients produced on flash excitation of degassed aqueous solutions have been identified as the triplet excited state, the hydrated electron, a purine radical cation and radical anion on the basis of quenching experiments and comparison to transients observed in low temperature photolysis.
PHOTOREVERSIBLE Ca2+‐DEPENDENT AGGREGATION OF PURIFIED PHYTOCHROME FROM ETIOLATED PEA AND RYE SEEDLINGS
Authors: Yamamoto Kotaro T. , Jr William O. Smith , Furuya Masaki 
Published: January 2008

Abstract—The aggregation of phytochrome purified from etiolated pea (Pisum satirum cv. Alaska) and rye (Secale cereale cv. Cougar) tissues was investigated by centrifugation and turbidimetry. Purified pea phytochrome (A669/A280= 0.88), if irradiated with red light, became precipitable in the presence of CaCl2. The precipitation upon red‐light irradiation was optimal at a Ca2‐ or Mg2+ concentration of 10–20 mM, was greater at increased phytochrome concentration or lower pH values, and was inhibited by 0.1 M KG. The precipitated phytochrome slowly became soluble after far‐red light exposure.Turbidity of pea phytochrome solutions after red‐light irradiation also increased rapidly in the presence of either Ca2+ or Mg2+. Far‐red light exposure after the red light cancelled the turbidity increase. Rye phytochrome showed less turbidity increase than pea phytochrome and occurred only in the presence of Ca2+. Partially degraded pea phytochrome produced by endogenous proteases in the extract did not show the turbidity increase. Undegraded pea phytochrome also associated with microsomal fractions under conditions similar to those described above, but the partially degraded phytochrome did not.
SPECTRAL CHARACTERISTICS AND MECHANISM OF CHEMILUMINESCENCE FROM TRYPTOPHAN SOLUTIONS INDUCED BY UV‐IRRADIATION
Authors: Slawiński Janusz , Elbanowski Marian , Slawińska Danuta 
Published: January 2008

Abstract—The spectral distribution of the chemiluminescence, fluorescence and phosphorescence of tryptophan aqueous solutions irradiated with high and low pressure mercury lamps has been measured. The blue emission bands in the region of 380–520 nm observed both in the chemi‐ and photoluminescence, as well as an absorbance increase at 230 and 330 nm, indicate oxidative degradation of tryptophan leading to the formation of derivatives of N‐formylkynurenine, xanthurenic and anthranilic acids. Red emission bands at 630 and 705 nm in the spectrum of the chemiluminescence, an enhancement of light intensity by D2O and its decrease by NaN3 and DABCO suggest a partial contribution of O2(1Δg) to the photooxidation and chemiluminescence of tryptophan. The enthalpy of the exergonic reactions, leading to the formation of luminescing products, was calculated to average ‐270 kJ‐mol.
VIABILITY OF THE SPORES FORMED AFTER UV IRRADIATION IN DICTYOSTELIUM DISCOIDEUM
Authors: Nozu Kliichi , Ohnishi Takeo , Okaichi Kumio 
Published: January 2008

Abstract—Both abilities of germination of spores formed after UV irradiation and of growth of amoeboid cells emerged from the spores were studied on two kinds of Dictyostelium discoideum strains, NC‐4 and ys‐13.An inhibition of germination was observed on the spores of ys‐13 when formed after UV irradiation, while no inhibition was detected on the ability of germination of spores of NC‐4. The amoeboid cells of ys‐13 emerged from the spores showed a heavy delay of growth, although no delay of growth was detected even on the amoeboid cells of NC‐4 emerged from the spores formed after UV irradiation. The strain of NC‐4 must repair UV lesions fully before spore formation, while the spores of ys‐13 must keep some UV lesions unrepaired and send them to the next generation of amoeboid cells. The characters of UV lesion inheritable through the spores to the next amoeboid cells in ys‐13 were discussed.
PHOTOREACTIVATING ENZYME FROM STREPTOMYCES GRISEUS—III. EVIDENCE FOR THE PRESENCE OF AN INTRINSIC CHROMOPHORE
Authors: Eker A. P. M. 
Published: January 2008

Abstract—Evidence is presented that DNA photoreactivating enzyme from Streptomyces griseus consists of a high molecular protein part and a low molecular chromophore which is released by denaturation. The free chromophore is highly fluorescent and has an absorption maximum at 420 nm. In native photoreactivating enzyme the chromophore fluorescence is almost completely quenched and there is an additional absorption band at 445 nm. Native photoreactivating enzyme spontaneously looses its chromophore following first order kinetics as measured by the increase of fluorescence intensity. A good correlation was found between the increase of fluorescence intensity and the decrease of biological activity, stressing the importance of the chromophore‐protein bond. The presence of DNA greatly retards the spontaneous release of chromophore, and with UV‐irradiated DNA the photoreactivating enzyme is almost completely stable. In five different chromatographic systems, cochromatography of biological activity and enzyme‐bound chromophore was found, thus ruling out the possibility that the observed chromophore belongs to a contamination in the enzyme preparation. Photoreactivating enzyme binds very strongly to Blue‐Sepharose indicating the presence of a positive charge in the polynucleotide binding site.
DNA EXCISION REPAIR IN LYMPHOCYTES FOLLOWING PHOTOAFFINITY LABELING WITH ETHIDIUM MONOAZIDE
Authors: Cantrell Charles E. , Yielding K. Lemone 
Published: January 2008

Abstract—Irradiation of ethidium monoazide by fluorescent light promotes a chemical decomposition of the azide into a highly reactive nitrene intermediate. Covalent bonding of this electrophile to the DNA in the cell provokes repair of damage which can be monitored by incorporation of [3H]‐thymidine. Human lymphocytes were labeled with [14C]‐ethidium azide and then allowed to undergo DNA repair. Repair incorporation of [3H]‐thymidine showed saturation at 5 µM ethidium azide, but excision of the labeled drug failed to saturate at 20 µM, suggesting that excision and resynthesis are two separate events. Cells were also labeled with the photosensitive drug and/or exposed to UV radiation, and then allowed to undergo a period of DNA repair. The tritium incorporation for the combined insults was less than the sum of the two insults. Quinacrine, progesterone and chloroquine inhibited repair incorporation of [3H]‐thymidine, but had no effect on the excision of the drug from the DNA. After damage by ethidium azide, chromatin was isolated from lymphocytes which had been allowed to repair label with [3H]‐thymidine. Partial digestion of the chromatin with micrococcal nuclease released 80% of the tritium when approximately 40% of the DNA had been hydrolyzed by the enzyme.
PHOTOCHEMICAL ADDITION OF L‐LYSINE TO 1,3‐DIMETHYL‐4‐THIOURACIL*
Authors: Ito Satoru , Saito Isao , Nakata Akira , Matsuura Teruo 
Published: January 2008

Abstract—Irradiation of an aqueous solution of 1,3‐dimethyl‐4‐thiouracil (1) in the presence of l‐lysine (2) with a high‐presure mercury lamp through a Pyrex filter gave a 1:1 mixture of two photoproducts. One of the products was isolated in a pure form, which on treatment with acetic anhydride‐pyridine yielded the starting material 1. Based on the spectral data (1H and 13C NMR) and the chemical reaction, the structure of the photoproduct was assigned to 3. The photochemical reaction is considered as a nucleophilic addition of l‐lysine to photoexcited 1.
THE EFFECT OF DARK COMPLEXING ON THE PHOTOSENSITIZED FORMATION OF 8‐METHOXYPSORALEN CROSS‐LINKS WITH DNA*
Authors: Grossweiner L. I. , Sherman W. V. 
Published: January 2008

Abstract—The near‐UV dose at 365 nm required for the formation of 8‐methoxypsoralen (8‐MOP) cross‐links with calf thymus DNA was found to be insensitive to the concentration ratio of nucleotides to 8‐MOP over the range 100:1 to 5:1. The proposed explanation is that only the dark‐complexed 8‐MOP contributes to the photosensitized formation of monoadducts and cross‐links. A kinetics analysis indicates that the fluence required for cross‐linking should be inversely proportional to the square root of the fraction of dark‐complexed 8‐MOP per nucleotide (the binding ratio), a quantity that is insensitive to the ratio of nucleotides to 8‐MOP. These findings predict a small dependence of photosensitivity on the total 8‐MOP concentration in cellular systems in which cross‐links are the major lethal lesion.
GENETIC CONTROL OF NEAR‐UV SENSITIVITY INDEPENDENT OF EXCISION DEFICIENCY (uvrA6) IN ESCHERICHIA COLI K12
Authors: Tuveson R. W. 
Published: January 2008

Abstract—By appropriate matings, recombinant strains carrying all four possible combinations of genes controlling near‐UV (nur vs nur+) and far‐UV (uvrA6 vs uvrA+, excision repair function) sensitivity have been constructed. Near and far‐UV inactivation experiments with the four recombinant strains reveal that inactivating events induced by near and far‐UV do not appear to overlap. These results are analogous to our previously reported experiments (Tuveson and Jonas, 1979) with recombinant strains carrying all four possible combinations of genes controlling near‐UV sensitivity (nur vs nur+) and recombination proficiency (far‐UV sensitivity, recA1 vs recA+). The results of these two sets of experiments taken together may mean that any recA+ or uvrA+ repairable lesions induced by near‐UV are repaired equally well by either system and do not require the simultaneous participation of both repair systems.
PHOTOTACTIC ORIENTATION BY THE CILIATE, STENTOR COERULEUS
Authors: Song Pill‐Soon , Häder Donat‐P. , Poff Kenneth L. 
Published: January 2008

Abstract—Stentor coeruleus exhibits negative phototaxis to visible light, in addition to a step‐up photophobic response. The negative phototaxis was established by demonstrating the swimming of Stentor toward a focused beam away from the light source. The action spectrum showed a maximum at 610–620 nm and is essentially identical to that of the step‐up photophobic response. Proton uncouplers such as micromolar concentrations of FCCP and TPMP+ inhibited the negative phototaxis.