bluuebunny/crossref_metadata_2025_split huggingface dataset:
LIGHT‐INDUCED LINEAR DICHROISM IN PHOTOREVERSIBLY PHOTOCHROMIC SENSOR PIGMENTS–II. CHROMOPHORE ROTATION IN IMMOBILIZED PHYTOCHROME
Authors: Sundqvist Christer , Björn Lars Olof 
Published: January 2008

Abstract‐Large phytochrome immobilized via anti‐phytochrome immunoglobulin bound to Sepharose beads was irradiated to saturation with unpolarized far‐red light. The apparent absorbance level was recorded in a dual wavelength spectrophotometer with both measuring beams set to either 660 or 730 nm and polarized perpendicular to each other. The sample was then irradiated with red polarized light. The apparent change in absorbance obtained after this irradiation indicated that purified phytochrome could show linear dichroism. From the absorbance values obtained it was computed that the direction of the long‐wavelength transition moment changes by either 32 or 148o, when phytochrome is transformed from Pr to Pfr. Considering the model of Hahn and Song (1981) the latter value appears more likely. In light of these results, the conclusions drawn from in vivo experiments on action dichroism in Dryopteris (Etzold, 1965), Adiantum (Kadota et al., 1982) and Mougeoutia (Haupt. 1970), which point to a 90o rotation. should be reconsidered.
A COMMENT ON SPECTRAL TRANSMITTANCE IN MAMMALIAN SKELETAL MUSCLE
Authors: Preuss L. E. , Bolin F. P. , Cain B.W. 
Published: January 2008

AbstractSpectral transmittance studies, related to photoradiation therapy light dosage, were carried out in vitro on mammalian skeletal muscle with expanded beam, broad band, white light (420‐1100 nm). Spectra were collected by an EG&G 550/555 spectroradiometer with a 550‐2A silicon detector. Bovine striated muscle imposes heavy absorption and distinct spectral structure, reflecting tissue absorption maxima at short wavelengths. Transmission above 650 nm is improved by a 10' factor, relative to blue light, in 1 cm of muscle. Half value layers were 0.82 mm in the 630 nm region, and were sensitive to tissue composition. Bovine muscle exhibited spectral effects related to the cadaver studies done by Wan et at. (1981b) but show singular differences, due primarily to complex tissue composition encountered in cadaver wall measurements, as contrasted with simple muscle. Spectral transmittance is a function of wavelength, tissue type and thickness.
NANOSECOND LASER PHOTOLYSIS OF RHODOPSIN AND ISORHODOPSIN
Authors: Horwitz J. S. , Lewis J. W. , Powers M. A. , Kliger D. S. 
Published: January 2008

AbstractKinetic and spectral measurements have been carried out on the primary intermediate in the photolysis of rhodopsin and isorhodopsin, initiated by a 457 nm, 6 ns (FWHM) laser pulse. In rhodopsin the kinetic decay of bathorhodopsin was found to be 140 ± 15 ns at 20°C. The decay of bathorhodopsin to lumirhodopsin has an activation energy of 51 ± 4 kJ/mol (12.2 ± 1 kcal/mol). The decay kinetics of bathorhodopsin were found to be the same for rhodopsin in membrane and detergent solubilized suspensions. The kinetic decay of the batho product in the photolysis of isorhodopsin was found to be the same as rhodopsin.The corrected transient spectrum 50 ns following excitation in rhodopsin has two peaks near 560 and 440 nm. A peak was also observed in isorhodopsin near 550 nm at 50 ns following excitation but no transient was observed in the blue. The 550 nm peak in isorhodopsin has an intensity similar to that in rhodopsin indicating that the quantum yields for the formation of batho products of rhodopsin and isorhodopsin are similar under the irradiation conditions used here. Transient spectra for rhodopsin and isorhodopsin 1 μs following excitation are also different. In isorhodopsin the corrected transient spectrum has a peak at 500 nm, similar to low temperature steady state irradiation spectra. The 1 μs transient spectrum in rhodopsin is more intense than in isorhodopsin and shows a peak at 475 nm.
OPTICAL PROPERTIES OF PHYTOCHROME IN THE BLUE‐ SPECTRAL REGION AS MEASURED IN VIVO AND IN VITRO
Authors: Epel B. L. , Horwuz B. A. , Baron O. 
Published: January 2008

AbstractIn the blue spectral region, the phototransformation difference spectrum of oat phytochrome extracted as Pfr differs from that of phytochrome extracted as Pr. The difference absorbance maximum for phytochrome extracted as Pfr is at 420 nm, while that extracted as Pr is at 412 nm. The phototransformation difference spectrum measured in the blue in oat coleoptile tips without inner leaves, corresponds very well with that of phytochrome as extracted in its Pfr form. There is, however, a slight apparent attenuation of the blue difference band relative to those in the red‐far‐red. In coleoptile tissue containing inner leaves, the blue difference band is relatively even more highly attenuated. A similar attenuation is observed in the blue, in the protochlorophyllide to chlorophyllide phototransformation difference spectrum. In the spectrum measured with excised coleoptile without inner leaves, there is a small attenuation, while in coleptile tissue with inner leaves the attentuation is nearly 9‐fold. These data suggest that the observed attenuation is probably artifactual. Neither instrumental non‐linearity nor fluorescence induced by the measuring beam could explain the observed attenuation. It is suggested that the observed attenuation is probably mainly the result of wavelength dependent scatter amplification, the amplification in the blue being attenuated by the high background absorption of other pigments in this region.
RED EMISSION FROM CHLOROPLASTS ELICITED BY ENZYME‐GENERATED TRIPLET ACETONE AND TRIPLET INDOLE‐3‐ALDEHYDE
Authors: Nassi Lilian , Cilento Giuseppe 
Published: January 2008

Abstract—Enzyme‐generated triplet acetone and triplet indole‐3‐aldehyde transfer energy very efficiently to chloroplasts, as indicated by the intensity of the sensitized red emission that is observed. The intermediacy of excited species of oxygen (1O2, O2−, HO) has been excluded. Our results open the way for investigating energy transfer in architecturally organized systems in the absence of light.
INTRAMICELLAR QUENCHING OF 2,3‐DIMETHYLNAPHTHALENE FLUORESCENCE BY PEROXIDES and HYDROPEROXIDES
Authors: Encinas M. V. , Lissi E. A. 
Published: January 2008

AbstractHydrogen peroxide, t‐butyl hydroperoxide, di‐t‐butyl peroxide and dibenzoyl peroxide efficiently quench the fluorescence of 2,3‐dimethylnaphthalene incorporated into sodium dodecyl sulfate and cetyltrimethylammonium chloride micelles. Potassium persulfate only is effective when the probe is incorporated into a cationic micelle. The binding constant of the peroxides and the intramiccllar quenching rate constants have been evaluated for all the systems considered and the data are compared to that obtained in homogeneous solution. It is concluded that, even for processes which are not diffusion controlled, the quenching process is slower in the micelles.
CIRCANNUAL COURSE OF PHOTOMORPHOGENETIC REACTIVITY IN ETIOLATED BEAN SEEDLINGS
Authors: Spruyt E. , Maes L. , Verbelen J.‐P. , Moereels E. , De Greef J. A. 
Published: January 2008

AbstractHook opening and leaf expansion, measured 24 h after standard red light illumination, were considered as parameters determining the photoactivity of etiolated Phaseolus vulgaris L. seedlings. The experiment was repeated every h during one 17‐h period each month for 1 year. The mean values for each experimental period indicated that the photoactivity of the etiolated seedlings changed markedly throughout the year according to a seasonal pattern.
RESISTANCE OF THE SCRAPIE AGENT TO INACTIVATION BY PSORALENS
Authors: Mckinley MichaelP. , Masiarz FrankR. , Isaacs StephenT. , Hearst JohnE. , Prusiner StanleyB. 
Published: January 2008

Abstract–In searching for a nucleic acid within the scrapie agent, we employed psoralens which penetrate the coats of most conventional viruses, form photoadducts with their genomes, and block replication of the viruses. Five psoralens, at concentrations up to 500 times greater than those required to inactivate conventional viruses, did not influence scrapie agent titers in partially purified preparations from murine spleen and hamster brain. 3H‐psoralens were used to monitor the formation of photoadducts within nucleic acid standards added to preparations of the scrapie agent. Since no inhibition of psoralen photoadduct formation was observed in these preparations, one of three possibilities seems likely: the scrapie agent is devoid of nucleic acid, the psoralens failed to penetrate the protein coat of the agent, or its nucleic acid is unreactive with psoralens.
SOME PHOTOPHYSICAL PROPERTIES OF 3‐CARBETHOXYPSORALEN, 8‐METHOXYPSORALEN and 5‐METHOXYPSORALEN TRIPLET STATES
Authors: Craw M. , Bensasson R. V. , Ronfard‐Haret J. C. , Melo M. T. Sae , Truscott T. G. 
Published: January 2008

Abstract Triplet absorption spectra, extinction coefficients (ɛT), decay rates (K1), oxygen quenching rates (kq) and intersystem crossing yields (φT) for 3‐carbethoxypsoralen (3‐CPs). 8‐methoxypsoralcn (8‐MOP) and 5‐methoxypsoralen (5‐MOP) in methanol are reported. For 8‐MOP and 3‐CPs corresponding values are also reported with water as the solvent. Some photophysical data are also reported for 5‐MOP in water, but ɛT and φT were not obtained.The phosphorescence spectra for these furocoumarin derivatives in ethanol at 77 K are reported together with the corresponding lowest triplet energy and lifetime. The values of the various photophysical properties obtained are compared with values reported by previous workers.
THE TRIPLET AND RADICAL SPECIES OF HAEMATOPORPHYRIN AND SOME OF ITS DERIVATIVES
Authors: Bonnett R. , Lambert C. , Land E. J. , Scourides P. A. , Sinclair R. S. , Truscott T. G. 
Published: January 2008

Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0‐acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).After 347 nm irradiation in water containing 2% Triton X‐100, haematoporphyrin forms the triplet state (φT= 0.92) and photoionises monophotonically (φI= 0.03). For the O‐acyl derivatives, φT approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates (k1˜104s‐1) and oxygen quenching constants (kQ˜1.5times109M‐1s‐1) for the triplet state have been measured. The difference and corrected spectra for the semi‐reduced species in methanol and semi‐oxidised species in aqueous Triton X‐100 are presented.The photophysical characteristics in fluid solution of haematoporphyrin and its 0‐acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins.
PHOTOCHEMICAL INACTIVATION OF SINGLE‐STRANDED VIRAL DNA IN THE PRESENCE OF UROCANIC ACID*
Authors: Tessman Irwin , Morrison H. , Bernasconi C. , Pandey G. , Ekanayake† L. 
Published: January 2008

Abstract— Urocanic acid (UA) has previously been shown to react photochemically in vitro with N,N‐dimethylthymine. In this study, mixtures of UA and phage G4 single‐stranded DNA have been irradiated with UV light (λ≥ 254 nm) and the DNA assayed for infectivity. At the concentrations of UA employed (typically 5.4 × 10‐3M) there is extensive absorption of the incident light by the UA. The DNA is inactivated at rates greater than that predicted from the calculated shielding by UA, indicating that photosensitization is occurring. Photosensitization is also indicated by the fact that at high UA concentrations the inactivation rate does not decrease to zero but approaches a residual value. Furthermore, the ability to photoreactivate DNA that has been photolyzed in the presence of UA is much reduced relative to that observed upon photolysis of the DNA alone. UA is therefore responsible for the production of UV‐induced DNA lesions, which are resistant to photoreactivation.A general analysis of the effects of photosensitization on the kinetics of UV inactivation is presented in an appendix.
AN EXPERIMENTAL STUDY OF THE CHANGES IN PIGMENTATION IN HUMAN SKIN IN VIVO WITH VISIBLE AND NEAR INFRARED LIGHT
Authors: Kollias N. , Baqer A. 
Published: January 2008

Abstract— The skin of the lower inner arm of volunteers was irradiated, with a 390–1700 nm light source, through a fiber optic bundle for times of up to 1.2 × 104 s and with powers of up to 0.35 W/cm2. Simultaneously with the irradiation, spectra (390–720 nm) of the remitted intensity were measured, while a 5.0 cm in diameter area of the skin around the fiber bundle was maintained at constant temperature, within 0.2°C. The generation of a photoproduct was observed and measured as changes in the remitted intensity within 600 s (10 min) of the start of irradiation.The photoproduct formed was characterized by a weak absorption in the blue part of the spectrum (400–450 nm), leading to a bluish appearance in the irradiated area only. The color change appears as a two step process. It starts with a “soluble” photoproduct, which disappears, within 24 h after irradiation, and an “insoluble” photoproduct which appears with irradiation greater than 3 ×103 s (50 min). No spectral differences were detected between the two photoproducts. The “insoluble” photoproduct persists for periods of up to 8 weeks. The color change in the skin is immediate and there is no erythema associated with this color change.
POLARIZED UV‐ABSORPTION SPECTRA OF RETINAL ISOMERS—II. ON THE ASSIGNMENT OF THE LOW AND HIGH ENERGY ABSORPTION BANDS
Authors: Drikos G. , Rüppel H. 
Published: January 2008

Abstract The polarized UV‐absorption spectra of all‐trans retinal and both crystal forms of 11‐cis, 12‐s‐cis retinal (presented in the previous paper, Part I) are analyzed using Lowry‐Hudson functions to describe the band profiles. The polarization ratios of the polarized bands is used to determine the direction of the corresponding transition moments. For all‐trans retinal the polarization spectra show that the absorption between 23 and 36 X 103 cm−1 is caused by three overlapping bands labeled S, A and B. For 11‐cis retinal the B‐band is also clearly resolved whereas the S and A bands are separated with much less certainty than for all‐trans retinal.Comparing these bands with the excited state manifold resulting from semiempirical CI‐calculations including double excitations, the S‐band could be assigned to the 1Ag−→1Ag‐* and the A‐band to the 1Ag−→1Bu+* transition. However, no transition is found in this manifold which could positively be assigned to the B‐band because the transitions predicted in this spectral region have negligible oscillator strengths. In all the crystal spectra a further band C is observed around 39 X 103 cm−1 which is particularly pronounced in the case of 11‐cis retinal. For this band an assignment to the 1Ag−→1Ag+*‐transition is proposed.
ROLE OF ELECTRIC POLARIZATION IN THE THERMOLUMINESCENCE OF CHLOROPLASTS
Authors: Knox P. P. , Venediktov P. S. , Kononenko A. A. , Garab Gy. I. , Faludi‐Dániel Á. 
Published: January 2008

Abstract Effect of an external electric field on thermoluminescence and thermodepolarization currents were studied in suspensions and dry films of pea chloroplasts. The external electric field was applied either during interrupted heating at a given temperature (“direct effect”) or was “stored” in the sample during cooling in the range –25°C and –70°C (“electret effect”).It is shown that in chloroplast suspension both the luminescence burst upon “direct effect” and the new band peaking between –40°C and –50°C induced by the “electret effect” are accompanied by a preferential decrease in the intensity of the thermoluminescence band around +10°C.A correlation was established between the polarized state of thylakoids and the thermoluminescence burst induced by the external field. In electret samples of chloroplast suspension the intensity of field induced low temperature thermoluminescence band under different experimental conditions varied in parallel with the intensity of thermodepolarization current. In dry films of chloroplasts, in addition to parallel changes in intensities of thermoluminescence and thermodepolarization current, also the peak positions shifted in the same manner when either humidity of samples or temperature of illumination and of application of external field were varied.We conclude that the polarization state of thylakoid membrane, which can be governed by an external electric field, plays an important role in determining charge stabilization and recombination properties of photosynthetic units. Our results implicate that electric field induces conformational changes in the membranes which increases the frequency factor ascribed to the recombination processes.
FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS BY ALIPHATIC AMINO ACIDS. EVIDENCE FOR EXCITED STATE COMPLEXES
Authors: Bohorquez M. del V. , Cosa J. J. , Garcia N. A. , Previtali C. M. 
Published: January 2008

Abstract The fluorescence quenching of indole, tryptophan, tryptamine and indole‐3‐acetic by aliphatic amino acids was studied. The bimolecular rate constant (kq) for the deactivation of the excited state was determined. The kq values were in the range 0.6 × 108–1.6 × 109M–1 S–1 and they increased in the order tryptophan < tryptamine < indole ≈ indole‐3‐acetic acid. When the rate constant was corrected for diffusion al effects a good linear correlation was found between the log (k'q) and the ionization equilibrium constant of the carboxylic group of the amino acid (pka1). This was interpreted as arising from a charge transfer mechanism in which the indole moiety acts as an electron donor and the carbonyl group of the amino acid as the acceptor.The activation parameter for the quenching processes were also determined. The ΔH≠ values were in the range —4.0 to +4.0 kcal/mol and the ΔH≠ in the range –7 to –37 e.u. For the systems with lower values of kq negative values for ΔH≠ were observed. A good enthalpy‐entropy compensation was found with an isokinetic temperature of 229 K. These results suggest that a common mechanism is operating for all the systems and that it involves the formation of an excited state complex between the indolic compound and the amino acid.
PHOTOCHEMICAL EXCHANGE REACTIONS OF THYMINE, URACIL AND THEIR NUCLEOSIDES WITH SELECTED AMINO ACIDS
Authors: Shetlar Martin D. , Taylor John A. , Hom Kellie 
Published: January 2008

AbstractThe photoinduced exchange reactions of thymine with lysine at basic pH, using 254 nm light, have been studied. Three products have been isolated, namely, 6‐amino‐2‐(1‐thyminyl)hexanoic acid (Ia), 2‐amino‐6‐(1‐thyminyl)hexanoic acid (IIa) and 1‐amino‐5‐(1‐thyminyl)pentane (IIIa). Compound IIIa was shown to be a secondary product, produced by photochemical decarboxylation of Ia. Photochemical reaction of thymine with glycine and alanine at basic pH led, respectively, to formation of 2‐(1‐thyminyl)acetic acid (Ic) and 2‐(1‐thyminyl)propionic acid (Id). Compounds Ic and Id underwent photolysis to produce the decarboxylated secondary products 1‐methylthymine and 1‐ethylthymine, respectively. Thymidine reacts photochemically with glycine and alanine to produce the same products.Irradiation of DNA in the presence of lysine at basic pH led to the formation of the same products formed in the thymine‐lysine system, namely Ia, IIa and IIIa.Uracil was found to undergo analogous photochemical exchange reactions with lysine to form 6‐amino‐2‐(1‐uracilyl) hexanoic acid (Ib), and 2‐amino‐6‐(1‐uracilyl)hexanoic acid (IIb). Compound Ib was found to undergo photodecarboxylation to form 1‐amino‐5‐(1‐uracilyl)pentane (IIIb), analogous to the secondary photoreaction of Ia. Photoreaction of uracil with 1,5‐diaminopentane (cadaverine) likewise led to formation of IIIb.
A STUDY OF THE FLASH INDUCED 518 NM ABSORBANCE CHANGE KINETICS UNDER ANAEROBIC CONDITIONS
Authors: Popovic Radovan , Bruce Doug , Colbow Konrad , Vidaver William 
Published: January 2008

AbstractThe preillumination induced acceleration of the flash‐induced 518 nm absorbance change (ΔA518) decay was studied in lettuce leaves and chloroplasts. In leaves, the acceleration was inhibited by DCMU or reversibly by removal of oxygen. In chloroplasts with added ADP and phosphate and/or reconstructed electron transport, the acceleration was also inhibited by DCMU or the lack of O2.Anaerobic inhibition of ΔA518 decay acceleration was no longer observed when hydroxylamine replaced water as electron donor to PSII. Anaerobiosis was also shown to reversibly inhibit the initial rate of FeCN reduction in chloroplasts. These results suggest the mechanism of anaerobic inhibition of ΔA518 decay acceleration to be associated with the O2 evolving system.
ABSORPTION AND FLUORESCENCE STUDY OF TYROSINE‐DERIVED CROSSLINKING AMINO ACIDS FROM COLLAGEN
Authors: SAKURA S. , FUJIMOTO D. 
Published: January 2008

AbstractIsotrityrosine, an isomer of trityrosine with an ether linkage, is a new crosslinking amino acid recently found in cuticle collagen of Ascaris lumbricoides. The absorption and fluorescence spectra of this new amino acid were examined and compared with other tyrosine‐derived crosslinking amino acids. Isotrityrosine showed UV absorption maximum at 283 nm in acidic and neutral solutions and at 303 nm in strongly basic solution. The wavelengths are almost the same with those at dityrosine and trityrosine. The values of pKa, for chromophore phenols are 7.5 and 11.0. This means that two proton dissociations occur progressively one by one. Boric acid did not have any influence on isotrityrosine, though the effect on dityrosine and trityrosine was substantial. These facts mentioned above may suggest structural inequality of two phenols in an ether‐linked isomer. The wavelength of emission maximum was 450 nm, which was the longest wavelength among relative compounds examined. The fluorescence quantum yield was as small as 0.027, and the value was about one‐tenth of those of dityrosine and trityrosine. Isotrityrosine was also found in cuticle collagen of other worms which belong to the phylum nematoda.
USE OF SYNTHETIC POLYNUCLEOTIDES TO CHARACTERISE AN ANTISERUM MADE AGAINST UV‐IRRADIATED DNA
Authors: L. Mitchell David , Clarkson Judith M. 
Published: January 2008

AbstractUV—irradiated single‐stranded synthetic homopolymers were used to characterise an antiserum made against UV‐irradiated DNA. Using induction data obtained by reversed‐phase high performance liquid chromatography, the relative antigenicity of the polymers could be converted to relative binding affinity for each DNA photoproduct. Since no Pyr(6–4)Pyo adducts could be detected at 320 nm under these conditions, the affinity of the antiserum for this lesion could be compared with that for cyclobutane dimers. The relative binding capacity of Thy(6–4)Thy: Thy(5–6)Thy: Cyt(6–4)Cyt: Cyt(5–6)Cyt = 166: 1: 0.25: 0.062.