bluuebunny/crossref_metadata_2025_split huggingface dataset:
STUDIES OF THE ROLE OF THE COAT PROTEIN IN THE U.V. PHOTOINACTIVATION OF U(1) AND U(2) STRAINS OF TMV*
Authors: Streeter D. G. , Gordon M. P. 
Published: January 2008

Abstract— Two properties of the u.v. inactivation process in the u.v. sensitive U(2) strain have been investigated: (1) The increased binding of protein to RNA induced by irradiation of the virus at 254 nm; (2) The action spectrum for u.v. inactivation of U(2) between 250 nm and 285 nm. The extent of the u.v. induced binding of protein to RNA is similar to that previously found in the resistant U(1) strain, thereby eliminating the possibility that the capacity for this binding phenomenon bears any correlation to the difference in u.v. sensitivities of these two viruses at 254 nm. The results indicate that the radiation induced interaction of protein and RNA in U(1) and U(2) are probably similar.The action spectrum for U(2) resembles the absorption spectrum of the RNA between 250 nm and 285 nm implicating the RNA as the primary absorber leading to inactivation of the virus in this region of the spectrum.Quantum yields calculated for U(2) virus and free TMV‐RNA irradiated at 254 nm reveal that the irradiated free RNA may be as much as 1–4 times more sensitive to inactivation at this wavelength than RNA in the intact virus.It is concluded that the coat protein of U(2) probably offers some protection to the enclosed RNA against u.v. damage at 254 nm, therefore, the difference in u.v. sensitivity between U(1) and U(2) TMV at this wavelength is a consequence of a difference in the degree of protection offered by the respective coat proteins to the enclosed RNA.
THEORY ON THE RADIATIONLESS TRANSITIONS IN LARGE POLYATOMIC MOLECULES
Authors: Ting Chen‐Hanson 
Published: January 2008

Abstract— The stationary perturbation theory of Robinson and Frosch is shown to be inadequate to describe the radiationless transitions in polyatomic molecules. An alternative theory of radiative transfer of excitation energy proposed by Franck and Sponer is considered. Evidence shows that this theory leads to a general mechanism for many radiationless transitions in semi‐isolated molecules.Empirically, the rate constants of the excitation transfer between states i and f of the same energy can be expressed by a simple equation: kt‐f=1013(fi.ff)0.56sec‐1 where f's are oscillator strengths to the ground state. This equation is accurate to within an order of magnitude for various processes, such as internal conversions and intersystem crossings with rates differing by 14 orders of magnitude.The radiative transfer is the result of second order perturbation on the molecule by the radiation field. The equation of rate constant derived from the perturbation energy agrees fairly well with the above equation.
SENSITIZED PHOTOOXYGENATION ACCORDING TO TYPE I MECHANISM (RADICAL MECHANISM) ‐ PART I. FLASH PHOTOLYSIS EXPERIMENTS
Authors: KRAMER H. E. A. , MAUTE A. 
Published: January 2008

Abstract— The photooxygenation of allylthiourea (ATU) sensitized by thionine does not occur according to the singlet oxygen mechanism but rather proceeds via the formation of radicals. In oxygen‐free solution the primary process is a redox reaction between the thionine triplet and ATU where a semithionine‐ and an ATU‐radical are formed. In further reaction steps the leuco form of the dye is finally produced (reductive photobleaching; DR mechanism after Koizumi). The primary process in an oxygen‐containing aqueous solution is the same, since at high concentrations of ATU (0·2M) the amount of semithionine formed by a photolytic flash, as well as the time course of disappearance of semithionine, does not depend on the oxygen content of the solution.The reformation of thionine following flash photolysis has been investigated with regard to oxygen concentration and pH dependence. Two different excitation intensities were used. A quadratic dependence of thionine reformation on excitation intensity at high oxygen concentration was observed, indicating a reaction between two photoproducts.The dependence of the reaction rate of semithionine on the ionic strength has been investigated. These experiments show that the reaction partner of semithionine carries a charge of + 1 in oxygen‐free as well as in oxygen‐saturated solution.
QUANTUM YIELDS OF THE LUMINOL CHEMILUMINESCENCE REACTION IN AQUEOUS AND APROTIC SOLVENTS*
Authors: LEE J. , SELIGER H. H. 
Published: January 2008

Abstract— Quantum yields for luminol (3‐aminophthalic hydrazide) chemiluminescence reactions fall into two classes depending on oxidizing conditions. In aprotic solvents the quantum yield is high and the excitation yield which allows for the fluorescence quantum yield of the product, is 0·09 and is unaffected by changes in solution temperature or polarity, or the presence of quenchers. In aqueous solution under optimum pH conditions (11–13), hydrogen peroxide oxidation results in a high chemiluminescence quantum yield with an excitation yield of 0·04 again unaffected by temperature, viscosity or quenchers. Other oxidizing conditions produce lower quantum yields probably by the introduction of competing chemical pathways.The luminol chemiluminescence light standard has been used to calibrate a spectrofluoro‐meter with results in good agreement with the quantum yields of the ferrioxalate actinometer and the fluorescence of quinine sulfate and diphenylanthracene.
QUANTITATIVE CORRELATION BETWEEN SPECTROPHOTOMETRIC PHYTOCHROME ASSAY AND PHYSIOLOGICAL RESPONSE
Authors: Oelze‐Karow H. , Mohr H. 
Published: January 2008

Abstract— Apparent synthesis* of the enzyme lipoxygenase in the cotyledons of the mustard seedling (Sinapis alba L.) is controlled by phytochrome (Pfr ground state)† through a threshold (all‐or‐none) mechanism. This response was used to determine physiologically the photostationary states, Λ that is, the [Pfr]/[Ptot] ratios established by different wavelengths in the red and far‐red range of the spectrum, including the standard red and far‐red sources used in this laboratory (Mohr, 1966). Under the premises (for which justification has been given on previous occasions) that the [Pfr]/[Ptot] ratio for standard red light is 0.8, and that the decay of Pfr is a first‐order process with a half‐life of 45 min, the [Pfr]/[Ptot] ratios determined physiologically by means of the lipoxygenase response agree with the [Pfr]/[Ptot] ratios determined spectrophotometrically by Hartmann and Spruit (cf. Fig. 9 in Hanke et al., 1969) in hypocotyl hooks of mustard seedlings. In the hook the fr, that is, the [Pfr]/[Ptot] ratio for standard far‐red, is found to be 0.023. In the cotyledons, this ratio is several times higher (Schafer et al., 1972). The conclusion that apparent lipoxygenase synthesis in the cotyledons is controlled by phytochrome located in the hook has been substantiated by further spectrophotometric (Schäfer et al., 1973) and physiological experiments (H. Oelze‐Karow and H. Mohr, in preparation). The minimum steepness of the threshold was determined. An increase of the Pfr level from 118 (relative units) to 130 leads to an instantaneous and total suppression of apparent lipoxygenase synthesis; a corresponding decrease from 130 (relative units) to 118 leads to an immediate resumption of apparent LOG synthesis at full speed. It is concluded that an explanation of the experimental facts requires a cooperative effect on the level of Pfr, a high degree of synchrony on the cellular and organismic level and rapid communication between the hypocotyl hook and the cotyledons.*The term ‘apparent synthesis’ is used operationally in the present paper to denote any increase of enzyme activity, although de novo synthesis of lipoxygenase has not so far been rigorously demonstrated. The usual inhibitor experiments (cf. Oelze‐Karow et al., 1970) have led to the conclusion that intact RNA and protein synthesis is required for an increase of lipoxygenase activity.
INCREASED QUANTUM YIELD OF PHOTOREDUCTION OF DYES (A CATALYTIC EFFECT)
Authors: Steiner U. , Hafner M. , Schreiner S. , Kramer H. E. A. 
Published: January 2008

Abstract— While studying the photoreduction of some dyes (D) by reducing agents (R), it was observed that the quantum yield of the photoreduction increases considerably upon addition of a third substance (C), whereas it is very small when the dye is photoreduced by C alone (catalytic effect), (see Table 1).The system thionine (D), allylthiourea (R), and azulene (C) was investigated in detail using both flash photolysis and continuous illumination. On photolysis, thionine is converted into its photo‐reduced form, leucothionine. Azulene reacts with the basic form of the thionine triplet 3TH+ to produce the semithionine radical. In the system thionine and azulene, most of these radicals revert back to thionine. When ATU (˜ 102‐M) is added to thionine and azulene (3 × 10‐4M), the semithionine radicals are reduced to leucothionine; the quantum yield of this reduction is considerably higher than in the system thionine and allylthiourea. Flash experiments demonstrate that allylthiourea does not react with the semithionine radicals.At very high ATU concentrations (≥ 10‐1M), however, the primary reaction is between thionine triplet and allylthiourea; under these conditions the quantum yield is not influenced by azulene (3 × 10‐4M).
COMPARATIVE ANALYSES OF ACTION SPECTRA OF GLYCOLATE EXCRETION (“PHOTORESPIRATION”) AND PHOTOSYNTHESIS IN THE BLUE‐GREEN ALGA AN ACYSTIS NIDULANS
Authors: Sörensen Leonard , Halldal Per 
Published: January 2008

Abstract. The action spectra were determined by measuring photosynthetic H14CO‐3‐fixation and 14C‐glycolate excretion to the medium during 15 min exposure to light at 15 different wavelengths in the visible region using interference filters and a 2500 W high pressure Xe lamp at a constant photon flux of about 1.51 × 1019 quanta m‐2.s‐1 at all wavelengths.When plotted on relative scales the action spectrum of glycolate excretion lies below that of photosynthesis at all wavelengths shorter than 517 nm. As glycolate excretion had an exponential relationship to photosynthetic rates, different methods were used to analyze for a specific blue light effect which demonstrated that the relative amount of glycolate excretion was depressed by blue light compared with that by green and red. The greatest difference was observed around 460–480 nm. However, on statistical grounds it is not permitted to draw a difference spectrum which might indicate the absorption characteristics of pigment(s) involved.A hypothesis is discussed assuming that some glycolate is consumed in an oxidation process for supply of electrons to Photosystem I when Photosystem II is poorly excited in the blue region of the spectrum, which was the case for Anacystis used in the present investigation.
THE HABER‐WEISS CYCLE
Authors: Koppenol Willem H. , Butler John , Leeuwen Johan W. van 
Published: January 2008

Abstract— The Haber‐Weiss cycle:
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was investigated at low pH by radiolysis of oxygen or nitrogen saturated solutions of hydrogen peroxide. It was found that reaction 2 has a low rate constant: k2= 3.0 ± 0.6 M‐1 s‐1 (pH 2.3, 22°C). The rate determining step of reaction 2 is most probably the transfer of an electron from a π8* orbital of HO2 to the empty s̀u* orbital of H2O2. Overlap between these two orbitals is hindered by the filled π8* orbitals of H2O2. Fe(HI)EDTA catalyses reaction 2.
PHOTOINDUCTION OF PHARBITIS FLOWERING: RELATIONSHIP TO RNA SYNTHESIS AND OTHER METABOLIC EVENTS
Authors: Gressel J. , Zilberstein A. , Strausbauch L. , Arzee T. 
Published: January 2008

AbstractWe have previously shown that a wave of enhanced uridine incorporation into RNA occurs in the more vegetative parts of the plumule at the end of the single dark period that evokes flowering in Pharbitis nil. We demonstrate here that a light break that suppresses flowering suppresses this wave as well. It does not shift the kinetics of the wave of uridine incorporation to a different time. The enhanced incorporation is into all RNA fractions.It had been concluded from excision experiments that the floral stimulus reaches the apex much after photoinduction. There is a metabolic shock caused by such excision of the cotyledons or surgical removal of the plumule that can suppress flowering if it is performed near the end of the inductive dark period. The terminal bud is more affected by this shock than lateral buds. Excision of the cotyledons enhances the rate of incorporation of exogenous uridine into the plumule. We propose that the “floral stimulus” stimulating incorporation into RNA reaches the plumule immediately after the end of the critical dark period.
USE OF REGRESSION ANALYSIS TO ESTIMATE UV SPECTRAL IRRADIANCE FROM BROAD BAND RADIOMETER READINGS UNDER FS‐40 FLUORESCENT SUNLAMPS FILTERED WITH CELLULOSE ACETATE
Authors: Krizek Donald T. , Koch E. James 
Published: January 2008

Abstract— Weighted and unweighted UV spectral irradiances were measured under a 2‐lamp fluorescent fixture containing Westinghouse FS‐40 fluorescent sunlamps filtered with (6 h aged) 0.127 mm (0.005 in.) cellulose acetate by use of newly developed broadband UV radiometers and an automated UV spectro‐radiometer. Measurements were taken at 10‐cm intervals between 20 and 110 cm from the lamps. Correlations were determined between sets of data measured with the broadband radiometers and the UV spectroradiometer.By use of linear regression analyses on the weighted and unweighted spectral data, regression equations were developed for predicting UV‐B irradiance (unweighted mWm‐2), biologically effective UV (BUV) (weighted mWm) in the 280–320 nm (UV‐B) region, UV‐B sun equivalents, and incident flux density in the UV‐B region in photons m‐2× 1021 integrated over a 6‐h exposure. Examination of the correlation coefficients (r values) indicated that agreement was excellent between measured and predicted values for all comparisons (r values from 0.9972 to 0.9998).Use of regression equations should permit accurate. rapid estimation of both weighted and unweighted UV irradiances at any location in an experimental set‐up and provide a useful means for intra‐ and inter‐laboratory comparisons of spectral measurements, made in the interagency BACER program under FS‐40 fluorescent sunlamps filtered with 0.127 mm cellulose acetate (aged for 6h).
EFFECT OF INTRACELLULAR INJECTION OF EGTA AND TETRAETHYLAMMONIUM CHLORIDE ON THE RECEPTOR POTENTIAL OF LOCUST PHOTORECEPTORS
Authors: Tsukahara Yasuo 
Published: January 2008

Abstract— The depolarizing photoreceptor potential of locust, Valanga irregularis, as that of other arthropods, has an initial transient phase that declines to a stable sustained phase. In this work, the effect of intracellular injection of EGTA and TEA on these phases was studied.(1) Reversal potential of the transient phase was higher than that of the sustained phase.(2) EGTA and TEA enhanced both phases and the enhancement was more prominent in the sustained phase.(3) Resting potential was shifted slightly upward by the injection. The amplitude of the maximum response was also increased.(4) Current injected through an electrode filled with 2 M KCl had a significant effect on the shape of the response depending on the direction of the current.(5) It is suggested that the activation of K+ conductance induced by an increase of intracellular free Ca2+ concentration causes a decrease in amplitude of the sustained phase.
SPECIFIC PHOTOALKYLATION OF POLY U AND OF POLY A WITH 2‐PROPANOL AND THEIR MESSENGER PROPERTIES
Authors: Livneh Zvi , (Noy) Etta Livneh , Sperling Joseph 
Published: January 2008

Abstract—Ultraviolet light induced free radical alkylation of poly U or of poly A with 2‐propanol leads to the specific formation of 6‐(2‐hydroxy 2‐propyl) 5,6‐dihydro‐UMP or 8‐(2‐hydroxy 2‐propyl)‐AMP residues, respectively. The biochemical significance of the alterations in the modified polynucleotides was studied by testing their messenger activities in a cell free system of E. coli. Both photoalkylated poly U and poly A have reduced functional activity, with no change in functional specificity. This was demonstrated by inhibition of polymerization of phenylalanine and lysine directed by photoalkylated poly U and poly A, respectively, and by lack of misincorporation of other amino acids. The modification of poly U also caused the disappearance of misincorporation of serine that was found with the native polynucleotide.
THE PHOTOREACTIONS AND PHOTOSENSITIVITY OF 3,4‐DEHYDRO‐BACTERIORHODOPSIN AT LOW TEMPERATURES
Authors: Iwasa Tatsuo , Tokunaga Fumio , Ebrey Thomas G. , Yoshizawa Tǒru 
Published: January 2008

Abstract— The photoreaction of the artificial pigment synthesized from bacterioopsin and rrans‐3,4‐dehydro‐retinal, [3,4‐dehydro]bacteriorhodopsin ([3,4‐deH]bRt) was investigated with low temperature spectrophotometry.The amount of batho‐product formed from the light‐adapted pigment of [3,4‐deH]bR (designated as batho‐[3,4‐deH]bRt) by irradiation at 77 K was much less than that from trans‐bacteriorhodopsin (bRt) and depends on temperature at irradiation of the sample. The kinetics of photoconversion of [3,4‐deH]bRt to batho‐[3,4‐deH]bRt and that of its reversion were measured at several temperatures with a so‐called “double Dewar system”. The results showed that the photosensitivity of [3,4‐deH]bRt was temperature dependent. When batho‐[3,4‐deH]bRt was warmed above 143 K, it was converted to lumi‐[3,4‐deH]bRt. Lumi‐[3,4‐deH]bRt was also produced by irradiation of [3,4‐deH]bRt at 143 or 163 K. The maximum in the difference spectrum between lumi‐[3,4‐deH]bRt and [3,4‐deH]bRt was located at about 540 nm. The irradiation of [3,4‐deH]bRt at 183 K produced an intermediate analogous to meta‐bRt, but under similar conditions bRt does not produce meta‐bRt. These results indicate that intermediates of [3,4‐deH]bRt are less stable than those of bRt.The differences between bacteriorhodopsin and [3,4‐dehydro]bacteriorhodopsin were discussed and compared with the differences between rhodopsin and [3,4‐dehydro]rhodopsin.
OCCURRENCE OF PHOTOREVERSIBLE ABSORPTION CHANGES IN DISSOCIATED ALLOPHYCOCYANIN AND PHYCOCYANIN
Authors: Murakami Akio , Fujita Yoshihiko 
Published: January 2008

Abstract— Photochromic response of allophycocyanin (APC) and phycocyanin (PC) was studied. Phycobiliproteins were isolated from the blue‐green alga Tolypothrix tennis and supplementary from Anabaena cylindrica. The response was found in both APC and PC when they were dissociated into monomer in the presence of propylene glycol at high concentration. APC in propylene glycol solution showed two photoresponses identical with those of “phycochromes”c and d, respectively. PC showed the photoresponse “phycochrome”a type. After re‐association by removal of propylene glycol, photoresponse activities disappeared.We concluded that (i) some of monomer APC's and PC's became photoreactive when APC and PC were dissociated into monomer thus that (ii) photoresponses of “phycochromes”a, c and d were not attributed to the special pigments independent of APC and PC, but were responsible to special molecules of monomer APC and PC. Spectral patterns of photoresponses were discussed in relation to dissociation‐association of protein.
EFFECT OF CONTINUOUS FAR‐RED PREIRRADIATION ON THE LAG PHASE OF CHLOROPHYLL A ACCUMULATION IN PHARBITIS NIL COTYLEDONS
Authors: Yoshida Kazuichi , Konishi Michio 
Published: January 2008

AbstractIn Pharbitis nil cotyledons, the lag phase of chlorophyll a (Chi a) accumulation which continues for about 2 h after the onset of continuous white light is eliminated by preirradiation with far‐red light (FR) for 24 or 48 h. When the period of FR preirradiation is prolonged to 72 h or more, however, the lag phase is observed again (FR‐induced lag phase) and the rate of Chi a accumulation during the rapid accumulation phase is lowered below the dark control level.The application of exogenous 5‐aminolevulinate (J‐ALA) completely eliminates the FR‐induced lag phase, but this treatment eliminates the normal lag phase in dark‐grown cotyledons only partially (i.e. Chi a is accumulated but only slowly during the first few h). Application of a 5‐ALA precursor, such as glycin + succinate. 2‐ketoglutarate or glutamate, eliminates neither the FR‐induced lag phase nor the normal lag phase.A 24‐ or 48‐h FR irradiation seems not only to enable the synthesis of 5‐ALA but also to make the other regulatory factors favourable for Chi accumulation. When the period of FR irradiation is prolonged to 72 h or more, the ability to synthesize 5‐ALA may be lost.
HYPOCALCEMIA ASSOCIATED WITH PHOTOTHERAPY IN NEWBORN RATS: LIGHT SOURCE DEPENDENCE
Authors: Gutcher Gary R. , Odell Gerard B. 
Published: January 2008

AbstractLittermate pups of the congenitally jaundiced Gunn rat were studied at 4 days of age. Control animals were shaded from irradiation by opaque cardboard while littermates were exposed to daylight, blue, green or pink fluorescent light. Initially no significant differences were demonstrable between irradiated and control animals with reference to body weight, sex distribution, blood hematocrit, or serum bilirubin and serum calcium concentration. In all control groups, serum bilirubin values were unchanged or increased by the end of the study and serum calcium values were also unchanged. In the light‐exposed groups, serum bilirubin values decreased significantly in all except those exposed to pink light. The serum calcium level was decreased significantly only in pups exposed to fluorescent daylight at 5.00 μW/cm2/nm but in none of the other irradiated groups.
PRIOR EXPOSURE OF HUMAN CELLS TO NEAR UV‐RADIATION GIVES A DECREASE IN THE AMOUNT OF THE UNSCHEDULED DNA‐SYNTHESIS INDUCED BY FAR UV‐RADIATION
Authors: Holmberg M. 
Published: January 2008

AbstractPretreatment of human cells with near UV radiation (UVA) in fluences exceeding 5 × 104 Jm−2 caused a decrease in the amount of the unscheduled DNA synthesis induced by far UV radiation (UVC). The DNA repair synthesis, as measured by the incorporation of [3H] ‐thymidine, is reduced by nearly a factor of 2 for a UVA radiation exposure of 1.5 × 105 Jm−2. Since solar UVA fluence rate is rather independent of latitude, this figure corresponds to a UVA exposure time of 50‐60 min from noon sunlight in the summer time.
ACTION SPECTRA FOR INACTIVATION OF NORMAL and XERODERMA PIGMENTOSUM HUMAN SKIN FIBROBLASTS BY ULTRAVIOLET RADIATIONS
Authors: Keyse S.M. , Moss S. H. , Davies D. J. G. 
Published: January 2008

Abstract—Action spectra for UV‐induced lethality as measured by colony forming ability were determined both for a normal human skin fibroblast strain (lBR) and for an excision deficient xeroderma pigmentosum strain (XP4LO) assigned to complementation group A using 7 monochromatic wavelengths in the range 254‐365 nm. The relative sensitivity of the XP strain compared to the normal skin fibroblasts shows a marked decrease at wavelengths longer than 313 nm. changing from a ratio of about 20 at the shorter wavelengths to just greater than 1.0 at the longer wavelengths. The action spectra thus indicate that the influence on cell inactivation of the DNA repair defect associated with XP cells is decreased and almost reaches zero at longer UV wavelengths. This would occur, for example, if the importance of pyrimidine dimers as the lethal lesion decreased with increasing wavelength. In common with other studies both in bacterial and mammalian cells, our results are consistent with pyrimidine dimers induced in DNA being the major lethal lesion in both cell strains over the wavelength range 254‐313 nm. However, it is indicated that different mechanisms of inactivation operate at wavelengths longer than 313 nm.