bluuebunny/crossref_metadata_2025_split huggingface dataset:
WAVELENGTH DEPENDENCE AND DOSE‐RATE INDEPENDENCE OF UV RADIATION‐INDUCED IMMUNOLOGIC UNRESPONSIVENESS OF MICE TO A UV‐INDUCED FIBROSARCOMA
Authors: Fabo E. C. De , Kripke M. L. 
Published: January 2008

Abstract—Irradiation of BALB/c mice with FS40 sunlamps induces susceptibility to challenge with syngeneic UV‐induced fibrosarcomas that otherwise would be rejected immunologically. Plastic filters were used to remove various wavelengths from the radiation source to identify the active waveband. Wavelengths above 315 nm (those transmitted through a mylar filter) were ineffective in producing tumor susceptibility, even when the total amount of energy applied was the same as that emitted by the unfiltered FS40 sunlamps. Removal of wavelengths below 275 nm (with a polystyrene filter) did not reduce the activity of the radiation. Alteration of the dose‐rate of the radiation by as much as a factor of 10. by irradiating animals through neutral density filters, did not change the proportion of tumor‐susceptible mice, suggesting that there is reciprocity with regard to dose‐rate and time of UV exposure. Cell transfer studies were used to test whether similar immunologic mechanisms were responsible for the equal susceptibility to tumor challenge of mice given continuous UV exposure (one 12‐h treatment) or fractionated exposures (twelve 1‐h treatments). With both treatment regimens, tumor susceptibility could be transferred to X‐irradiated recipients with lymphoid cells, provided that sufficient time had elapsed after the single treatment.
LUMINESCENCE STUDIES OF QUINIZARIN AND DAUNORUBICIN
Authors: Capps Rodger N. , Vala Martin 
Published: January 2008

Abstract— The absorption and emission spectra of quinizarin (1,4‐dihydroxy‐anthraquinone) have been investigated in hydrocarbon and alcoholic solvents. Fluorescence spectra in 3 different Shpolskii matrices were recorded at 14 K. Vibrational analyses of these spectra revealed the presence of 3, 8, and 9 sites in octane, heptane, and hexane matrices, respectively. The fluorescence lifetime was found to be 6.5 ns in hexane and EPA. Fluorescence photoselection measurements in EPA (77 K) showed that the first 4 electronic transitions of quinizarin are polarized parallel, parallel, perpendicular, and parallel to the long molecular axis and can be assigned, in order of increasing energy, to 1B2, 1B2, 1A1 and 1B2 (ππ*)→1A1(C2v,) transitions, respectively. The fluorescent transition is assigned as 1B1 (ππ*)→1A1. The absence of phosphorescence is attributed to the intramolecular hydrogen bonding present which displaces the parent anthraquinone n→* states above the ππ* states, thereby rendering the intersystem crossing (S1‐T1) radiationless pathway inefficient.Photoselection measurements on daunorubicin, a substituted quinizarin and known anticancer drug, revealed an absorption band polarization pattern identical to that of quinizarin. These results are in part at variance with assumptions used in previous work on the intercalation specificity of daunorubicin with DNA.
EFFECTS OF SOLAR AND ARTIFICIAL ULTRAVIOLET‐B RADIATION ON LARVAL NORTHERN ANCHOVY, ENGRAULIS MORDAX*
Authors: Hunter John R. , Kaupp Sandor E. , Taylor John H. 
Published: January 2008

Abstract— Northern anchovy larvae were exposed to various amounts of both natural (global solar) and artificial (sunlamps filtered by cellulose triacetate) UV‐B energy over a 12‐day period. Dosage was determined on the basis of a weighting function for biological effectiveness. The action spectrum on which this biologically effective dose for anchovy mortality is based was developed using broad‐band spectroscopy. These experiments indicated that biologically adverse conditions exist near the sea surface. Larvae exposed in shallow containers to global solar UV for 12 days suffered significant UV mortality from February to October. Larvae surviving all solar and artificial UV doses were smaller than those not exposed to UV. [Lowest dosage = 398 J·m−2(bio.eff.).] Fifty percent of the larvae survived a cumulative dose of 605 J·m−2(bio.eff.), or 50 J·m−2·day−1(bio.eff). Dose reciprocity did not hold; when a similar cumulative dose was given in the first 4 days of 12, there were about one‐half as many survivors.One meter below the sea surface the daily solar UV dose (corrected for average cloud cover) is equal to or greater than 50 J·m−2(bio.eff.) (33°N, 118°W), the daily equivalent of the LD50, for 7 months of the year (March to September) at moderate chlorophyll‐a concentrations (0.5 mg‐m−3). These data suggest that larvae in the sea may be subject to some UV‐B stress at present. Owing to their seasonality of spawning and vertical distribution, anchovy populations may not be gravely endangered by moderate degree of stratospheric ozone diminution.
PHYTOCHROME and THE DEVELOPMENT OF PHOTOPHOSPHORYLATION CAPACITY—AN APPRAISAL OF THE EXPERIMENTAL APPROACH*
Authors: Oelze‐Karow H. , Mohr H. 
Published: January 2008

Abstract— Development of the capacity for photophosphorylation (= total capacity for light‐driven ATP formation) in the mustard (Sinapis alba L.) cotyledons is strongly influenced by a red light pulse pretreatment which operates through phytochrome. The present report deals with several objections raised against the in situ assay of the rate of photophosphorylation. Experimental evidence is given in support of the assumption that the linear increase of the ATP content of the cotyledons as measured over 1.5 min after the onset of saturating white light (370 Wm‐2) in fact represents the maximum rate of photophosphorylation (‘capacity’). Moreover, it is confirmed that control by phytochrome of the development of the photophosphorylation capacity and of the capacity for chlorophyll synthesis are unrelated phenomena. The failure of development of the capacity for photophosphorylation in isolated cotyledons from dark‐grown seedlings cannot be attributed to deficiencies of chlorophyll synthesis.It is concluded that the photophosphorylation response is particularly useful to study the mechanism of phytochrome (Pfr) action in case of a response which involves a threshold reaction and an interorgan (hook→cotyledon) cooperation.
UV‐ACTION SPECTRUM (254‐405 nm) FOR INHIBITION OF A K+ ‐STIMULATED ADENOSINE TRIPHOSPHATASE FROM THE PLASMA MEMBRANE OF ROSA DAMASCENA
Authors: Imbrie Catherine W. , Murphy Terence M. 
Published: January 2008

AbstractA K +‐stimulated ATPase from suspension‐cultured rose cells was isolated and subjected to UV radiation. The characteristics of the ATPase resembled those of a plasma‐membrane associated enzyme and not those of the mitochondrial enzyme. The ATPase required Mg2+ and was further stimulated up to 100% by K+. K+ stimulation was specific for ATP. The order of stimulation by monovalent cations was K+ > Na+ > Li+. The enzyme had a pH optimum of 6.5 in the presence of 50 mM K+. It was almost completely inhibited by diethylstilbestrol and partially inhibited by vanadate. but was not affected by azide or oligomycin. The inhibition of ATPase activity by various fluences of UV indicated that one fraction of the K+‐stimulated activity was very sensitive to radiation, while another fraction was relatively insensitive. It is possible that UV distinguished between two enzymes. The action spectra for inhibition of both fractions showed maxima at 290 nm and significant but much lower action throughout the near‐UV region, resembling spectra in the literature for the inhibition of transport processes in bacteria.
THE ELECTROCHEMICAL PROTON GRADIENT IN THE PHOTOSYNTHETIC PURPLE SULPHUR BACTERIUMCHROMATIUM VINOSUM
Authors: Davidson Victor L. , Knaff David B. 
Published: January 2008

AbstractCells of the photosynthetic purple bacteriumChromatium vinosumgenerate a transmembrane electrochemical proton gradient (δμH+H+) on illumination. The steady state values of the two components of δμH+m+, δpH and the membrane potential (δψ) have been measured as a function of both the pH and ion composition of the external medium. While δψ and δpH vary considerably as the external pH is varied from 5.5 to 7.5, the magnitude of δμH+h+remains relatively constant over this pH range. δψ is relatively unaffected by the ion composition of the medium but δpH and δμH+H+both vary considerably depending upon the cation present in the medium. The use of specific ionophores to eliminate either δpH or δψ results in changes in the magnitude of the other component. The δpH values determined here were used to predict the direction of Tl+flux via the potassium‐proton antiport and to demonstrate the reversibility of this antiport.
IRREVERSIBLE PHOTO IN ACTIVATION OF NITRATE REDUCTASE DURING THE FLAVIN‐SENSITIZED PHOTOCHEMICAL ASSAY OF ITS CATALYTIC ACTIVITY
Authors: Rosa Miguel A. Dela , Rosa Francisco F. Dela 
Published: January 2008

Abstract—The classic photochemical system in which flavin and EDTA act as photosensitizer and electron donor, respectively, has been employed for assayingin vitrothe catalytic activity ofAnkistrodesmus brauniinitrate reductase. When the photochemical assay is performed under air, but not in anaerobiosis, a considerable decay in the nitrite photoproduction rate is observed after 10–15 min. which is accompanied by a decrease of reduced methyl viologen‐nitrate reductase activity. The first enzyme activity, i.e. diaphorase is photoinactivated even more quickly and does not present any initial lag phase. Some oxygen species (superoxide and/or hydrogen peroxide) are probably involved in the photoinactivating mechanism, which appears to be non‐specific and irreversible.The use of flavin/EDTA photosystems is therefore, very practical for thein vitroassay of nitrate reductase activity, although anaerobic conditions are required for optimum results. Since inactivation of the terminal activity is, however, relatively slow, anaerobiosis would not be required for assay times shorter than 10 min.
PHOTOINDUCTION OF PROTOPERITHECIA IN NEUROSPORA CRASSA BY BLUE LIGHT
Authors: Innocenti F. Degli , Pohl U. , Russo V. E. A. 
Published: January 2008

AbstractBlue light induces the formation of Neurospora crassa protoperithecia.This photoinduction is completed in less than 24 h. Its threshold is about 4.2 J/m2. Red light is ineffective. The Bunsen‐Roscoe law is obeyed at the fluence of 12.6 J/m2 for fluence rates from 5.25 × 10 2 to 1.05 W/m2.
REMARKABLE INHIBITION OF OXYGEN QUENCHING OF PHOSPHORESCENCE BY COMPLEXATION WITH CYCLODEXTRINS
Authors: Turro Nicholas J. , Cox G. Sidney , Li Xin 
Published: January 2008

AbstractThe phosphorescence of the 4‐bromo‐l‐naphthoyl group is readily quenched by molecular oxygen in homogeneous solvents. However, when this lumophore is complexed with γ‐cyclodextrin in aqueous solution at room temperature, its phosphorescence is observed even under 1 atm of oxygen! Phosphorescence decay data indicated that two types of probe/cyclodcxtrin complexes are formed with lifetimes of 600 u,s and 3.5 ms. Oxygen completely quenches the fast decay, but only partially quenches the slow decay.
PHOTOPRODUCTS OF CHLORPROMAZINE WHICH CAUSE RED BLOOD CELL LYSIS
Authors: Kochevar Irene E. , Hom Jennie 
Published: January 2008

AbstractA mechanism for chlorpromazine (CPZ) phototoxicity has been proposed that attributes the response to formation of stable, toxic photoproducts which cause cell membrane disruption. We have characterized these toxic photoproducts as dimers and higher multimers of CPZ. Chlorpromazine solutions (3 or 10 mA/) were irradiated with a medium pressure Hg lamp filtered to exclude λ < 280 nm. Five low mol wt photoproducts were separated by high performance liquid chromatography. Two were identified as CPZ‐sulfoxide and promazine. Higher mol wt photoproducts were separated by Sephadex G‐50 chromatography into 3 broad bands which were characterized by their absorption and fluorescence spectra. Band A (mol wt > 800) had λmaxabs= 263 nm, λmaxfl= 490 nm and Band B (mol wt = 350‐800) had λmaxabs= 255 nm, λmaxfl= 450 nm. Based on the mol wt of CPZ, Band A contained trimers and higher mol wt compounds and Band B was composed of dimeric structures. BandC(λmaxabs= 255,310 nm; λmaxfl= 445 nm) was composed of CPZ (mol wt = 315) and the low mol wt photoproducts. Red blood cell lysis was used as an assay for the ability of photoproducts to cause membrane disruption. Bands A and B, but not Band C, caused cell lysis. These data indicate that the CPZ photoproducts which cause cell membrane disruption are dimers (Band B) and higher multimers (Band A).
PICOSECOND LASER PHOTOLYSIS STUDIES OF FLUORESCENCE QUENCHING MECHANISMS OF FLAVIN: A DIRECT OBSERVATION OF INDOLE‐FLAVIN SINGLET CHARGE TRANSFER STATE FORMATION IN SOLUTIONS and FLAVOENZYMES
Authors: Karen Akiya , Ikeda Noriaki , Mataga Noboru , Tanaka Fumio 
Published: January 2008

AbstractFormation of singlet charge transfer (heteroexcimer) states in the course of the fluorescence quenching of lumiflavin and riboflavin tetrabutyrate by indole and N‐methylindole have been directly observed by means of time‐resolved absorption spectral measurements using a picosecond laser photolysis method. Similar transient spectra have been observed also in the case of a flavoenzyme, D‐amino acid oxidase.
HALORHODOPSIN and PHOTOSENSORY BEHAVIOR INHalobacterium halobiumMUTANT STRAIN L‐33
Authors: Traulich Bernhard , Hildebrand Eilo , Schimz Angelika , Wagner Gottfried , Lanyi Janos K. 
Published: January 2008

AbstractHalobacterium halobium, strain L‐33, which is deficient in bacteriorhodopsin (BR) but synthesizes increased amounts of halorhodopsin (HR), shows behavioral responses upon changes in fluence rate with visible light or with UV light. The observations support the earlier report (Schimzet al., 1982). that BR is not essential for photosensing inH. halobium.In the UV‐range, changes in light intensity elicit the maximal response at λ= 370 nm. In the visible range, changes in light intensity show the maximal response at Δ= 565 nm and a secondary peak at Δ= 590 nm. The latter corresponds to the absorption maximum of HR (Δmax= 588 nm). This light‐energy converting retinal pigment ofH. halobiumthus appears to contribute to photosensory behavior.
ACTINOMETRY IN MONOCHROMATIC FLASH PHOTOLYSIS: THE EXTINCTION COEFFICIENT OF TRIPLET BENZOPHENONE AND QUANTUM YIELD OF TRIPLET ZINC TETRAPHENYL PORPHYRIN
Authors: Hurley John K. , Sinai Naomi , Linschitz Henry 
Published: January 2008

Abstract— The extinction coefficient εT, of triplet benzophenone in benzene has been directly determined by absolute measurements of absorbed energy and triplet absorbance, ΔD0T, under demonstrably linear conditions where incident excitation energy, E0, and ground state absorbance, A0, are both extrapolated to zero. The result, 7220 ± 320 M‐1 cm‐1 at 530 nm, validates and slightly corrects many measurements relative to benzophenone of triplet extinction coefficients made by the energy transfer technique, and of triplet yields obtained by the comparative method.As E0 and A0 both decrease, ΔD0T becomes proportional to their product. In this situation, the ratio R= (1/A0)(dΔD0T/dE0) = (εT ‐ εG)φT. Measurements of R, referred to benzophenone, give (εT ‐ εG)φT for any substance, without necessity for absolute energy calibration.Both absolute and relative laser flash measurements on zinc tetraphenyl porphyrin (εT ‐ εG at 470 nm = 7.3 × 104M‐1 cm‐1) give φT= 0.83 ± 0.04.
STUDIES ON PHYTOCHROME PHOTOCONVERSIONS IN VITRO WITH LASER‐INDUCED OPTOACOUSTIC SPECTROSCOPY*
Authors: Jabben Merten , Heihoff Klaus , Braslavsky Silvia E. , Schaffner Kurt 
Published: January 2008

AbstractAfter excitation at room temperature with a 15 ns dye laser pulse, phytochrome (60 kDalton) from etiolated oat seedlings was studied by optoacoustic spectroscopy, which records the heat emission caused by non‐radiative deactivation processes of the photoexcited molecule. The action spectrum for the heat emitted by Pr deviates from the absorption spectrum around 610 and 695 nm, indicating the build‐up of photoproduct(s) within 15 ns after excitation. It is proposed that the 695 nm product is identical with I700 and lumi‐R known to be the first intermediate on the Pr× Pfr pathway, and that the photochemical back reaction of I700 to Pr occurs on the same time scale. About 90% of the absorbed light energy was lost by radiationless deactivation. Values for the rate constants of excited state deactivation of Pr and for the internal energy content difference of the primary photoproducts are calculated.
ULTRAVIOLET ACTION SPECTRA FOR DNA DIMER INDUCTION, LETHALITY, AND MUTAGENESIS IN Escherichia coli WITH EMPHASIS ON THE UVB REGION
Authors: Peak M. J. , Peak J. G. , Moehring M. P. , Webs R. B. 
Published: January 2008

Abstract —Ultraviolet (UV) action spectra were obtained for lethality and mutagenesis (reversion to tryptophan independence) in Escherichia coli WP2s for wavelengths 254–405 nm with detailed analysis in the UVB region (290–320 nm). Parallel chemical assay yields of pyrimidine dimers in DNA of E. coli RT4 were determined at the same wavelengths. Spectral regions isolated from a Xe arc and resonance lines from a high‐pressure Hg‐Xe arc lamp were both used for irradiation. In all cases, precise energy distributions throughout the isolated Xe bands regions were defined.Lethality, mutagenesis, and dimer induction all decreased in efficiency in a similar fashion as the wavelengths of the radiation increased. Between 300 and 320 nm, all characteristics measured showed differences of about two and a half orders of magnitude. Between these wavelengths, the values of the three end points used either coincide with or parallel the absorption spectrum of DNA. The mutagenesis action spectrum coincides closely with the absorption spectrum of DNA. The lethality spectrum is closely parallel to the mutagenicity spectrum; the points, however, consistently occur at about 2 nm longer wavelengths. A calculation derived from the slope of the UVB spectra reveals that a 1‐nm shift of the solar UV spectrum to shorter wavelengths would result in a 35% increase in its mutagenic potential. At 325 nm, both biological action spectra show sharp decreases in slope. In addition, above 325 nm the spectra for lethality. mutagenicity, and dimer formation diverge sharply; lethalities at these UVA wavelengths were approximately tenfold greater relative to mutagenicity than at shorter wavelengths. The relative yield of dimer formation by 365 nm radiation is intermediate between the yields for lethality and mutagenesis.
ACTION SPECTRA FOR HEMATOPORPHYRIN DERIVATIVE AND PHOTOFRIN II WITH RESPECT TO SENSITIZATION OF HUMAN CELLSIN VITROTO PHOTOINACTIVATION
Authors: Moan Johan , Sommer Stein 
Published: January 2008

Abstract—Human cells of the line NHIK 3025 were labelled with hematoporphyrin derivative (Hpd) or Photofrin II (PII). Absorption and fluorescence excitation spectra of cell‐bound porphyrins were recorded. Furthermore, the corresponding action spectra for photoinactivation of the cells were determined in the spectral region 350–650 nm. The cell‐bound porphyrins were also analysed by means of HPLC. The following conclusions are drawn:(a) Porphyrins with low polarity are selectively bound to the cells.(b) Aggregated as well as unaggregated porphyrins are bound to the cells.(c) The action spectra indicate that the aggregated porphyrins do not contribute significantly to the photosensitivity of the cells.(d) The action spectra closely resemble the fluorescence excitation spectra of porphyrins bound to proteins.
SHORT‐TERM ADAPTATION OF HIGHER PLANTS TO CHANGING LIGHT INTENSITIES AND EVIDENCE FOR THE INVOLVEMENT OF PHOSPHORYLATION OF THE LIGHT HARVESTING CHLOROPHYLLalbPROTEIN COMPLEX OF PHOTOSYSTEM II
Authors: Dau Holger , Canaani Ora 
Published: January 2008

AbstractThe short‐term adaptation of intact leaves to an increase in light intensity was studied by an analysis of chlorophyll fluorescence and oxygen evolution monitored by photoacoustics. An increase in light intensity led to an oxygen “gush”. This “gush” was followed by a large (up to 120%) biphasic increase in the yield of oxygen evolution characterized by a fast phase (T = 0.5–2 min) and a slow phase (T = 4–20 min). The fast phase of the increase in oxygen yield was coupled to a decrease of fluorescence, whereas the slow phase was accompanied by a parallel fluorescence increase. A comparison of fluorescence parameters with oxygen yield indicates that the slow phase of the increase in oxygen yield was coupled to an increase in the antenna size of photosystem II. The slow phase was not inhibited by the uncoupler Nigericin but it was absent in chlorophyll‐b‐less barley mutants dencient in the light harvesting chlorophylla/bprotein complex of photosystem II (LHC II). These experiments indicate that changes in the LHC II mediated energy distribution, which occur in the time‐range of several minutes, are involved in the adaptation to changing light intensities. Moreover, electrophoretic analysis of32P orthophosphate labeled leaf discs adapted to low and high light intensities suggests that the slow phase of the increase in oxygen evolution involves dephosphorylation of the 25 kDa polypeptide of LHC II, by a small extent of 12%. The trigger for the slow phase of the increase in oxygen yield does not involve the oxidation of the plastoquinone pool. It was found that in response to the increased light intensity, the plastoquinone pool became more reduced as judged by model calculations. Experiments with the uncoupler Nigericin suggest that the control of the slow phase of adaptation to increased light intensity was also not exerted by the pH gradient across the thylakoid membrane.The similarities between the adaptation to increased light intensity and the state II to state I transition suggest that both adaptation phenomena involve LHC II dephosphorylation possibly triggered by the cytochromeb6/fcomplex.
FAR UV IRRADIATION OF DNA IN THE PRESENCE OF PROTEINS, AMINO ACIDS OR PEPTIDES
Authors: Larcom L. L. , Rains C. A. 
Published: January 2008

Abstract—The DNA of bacteriophage SP02c12 was subjected to 254 nm irradiation in solutions containing lysozyme or histone. In these solutions, the protein‐DNA mass ratios and the ionic strengths of the solvents were varied to change the amount of protein associated with the DNA. Lysozyme‐DNA binding constants were measured under the same conditions. The sensitivity of phage DNA to biological inactivation by UV increased as the amount of lysozyme bound per DNA strand increased. Although binding constants could not be measured for the DNA‐histone interaction, this protein had a protective effect which was greater under conditions which cause enhanced binding. No crosslinking of either protein could be detected even at doses ten‐fold greater than those giving a surviving fraction of 0.01.Irradiation was also performed in the presence of various amino acids and short peptides. These were chosen to include amino acids which: (1) are positively charged, (2) absorb UV of this wavelength or (3) form UV‐induced crosslinks to DNA. None of the amino acids tested affected sensitivity of the DNA to biological inactivation. Peptides containing a UV‐absorbing amino acid and a positively charged amino acid enhanced sensitivity. For each of these peptides, a mixture of the constituent amino acids had the same effect as the peptide itself. Under the conditions used, no evidence for formation of DNA‐amino acid crosslinks was found. The results indicate that proteins and peptides can sensitize DNA to UV inactivation by mechanisms other than covalent crosslink formation. Such mechanisms could include energy or electron transfer or alterations in the conformation of the DNA.