bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF LIGHT ON OSCILLATIONS OF ENZYME ACTIVITY DURING PHOTOMORPHOGENESIS IN CHENOPODIUM RUBRUM L.
Authors: Deitzer G. F. , Hopkins D. W. , Haertlé U. , Wagner E. 
Published: January 2008

AbstractAn approach to determine the photomorphogenic effect of light (white or continuous far‐red) on the development of rhythmic enzyme activity in Chenopodium rubrum L. is described. Previous results, obtained from mature seedlings grown in white light, demonstrated stable oscillations with periods ranging between 12 and 15 h for all of the enzymes tested. The present results, obtained during deetiolation, were complicated by the presence of a higher frequency component with a period of about 6 h. When the various oscillating components were defined, the analysis showed: (1) the enzymes of the Krebs cycle (malate and isocitrate dehydrogenase), the closely associated glutamate dehydrogen‐ase, and the glycolytic pathway ((NAD) glyceraldehyde‐3‐phosphate dehydrogenase) had a dominant period in the range of 12–15 h, (2) those of the oxidative pentose phosphate pathway were either weakly circadian (glucose‐6‐phosphate dehydrogenase) or apparently arhythmic (6‐phosphogluconate dehydrogenase), (3) the (NADP) glyceraldehyde‐3‐phosphate dehydrogenase from the Calvin cycle was circadian when kept in continuous darkness but becomes 15 h when placed in light, and (4) only the Calvin cycle enzyme is affected by light in the level of its activity and in its oscillatory behavior.
CHARACTERIZATION OF THE 32,000 DALTON MEMBRANE PROTEIN—I. EARLY SYNTHESIS DURING PHOTOINDUCED PLASTID DEVELOPMENT OF SPIRODELA
Authors: Reisfeld AVI , Gressel Jonathan , Jakob Karl M. , Edelman Marvin 
Published: January 2008

AbstractThe kinetics of 35S methionine incorporation into soluble and membrane proteins during the transition from steady state dark growth to greening was studied in Spirodela. A sharp increase in the rate of incorporation occurred at 3 h, which was several h before major increases in chlorophyll were apparent. Part of this enhanced incorporation was due to enhanced synthesis of a 32,000 dalton membrane protein. This synthesis was paralleled by a temporal increase in in uitro template capacity for this protein and an increase in 0.5 × 106 dalton plastid messenger RNA.
THE EFFECT OF LEVULINIC ACID ON THE LIGHT INDUCED DEVELOPMENT OF PHOTOSYSTEM I AND II ACTIVITIES IN GREENING MAIZE LEAVES*
Authors: Konis Y. , Klein S. , Ohad I. 
Published: January 2008

AbstractPhotosystem I and Photosystem II activities were measured in chloroplasts isolated after 0–20 h illumination from etiolated maize leaves in which chlorophyll synthesis was specifically inhibited by levulinic acid. In control leaves not treated with levulinic acid, Photosystem I activity/chlorophyll developed rapidly during the first 2h in light, then fell off, and reached a constant level after 6h of illumination. In levulinic acid treated leaves, in which chlorophyll accumulation was inhibited up to 60%, a similar initial rise in Photosystem I activity was observed. However, the decrease in activity was much slower and continued for at least 20 h. The development of Photosystem I activity calculated on a leaf fresh weight basis was similar for control leaves or leaves treated with levulinic acid. This indicates that development of Photosystem I activity may not be related to chlorophyll accumulation during greening.Photosystem II activity/chlorophyll in leaves treated with or without levulinic acid increased similarly during the first 6h and then remained constant. Activity of Photosystem II per leaf fresh weight increased linearly, after the first h, for 20 h in the control leaves; in levulinic acid treated leaves this development was reduced by about 60%. Thus, development of Photosystem II activity can be related to chlorophyll accumulation. SDS gel electrophoresis of plastid membranes from control leaves illuminated for 12 h showed the presence of chlorophyll‐protein complex I as well as Chl‐protein 11; in the case of levulinic acid treated leaves only Chl‐protein complex I was detectable, while Chl‐protein complex II was markedly reduced.
PROTEIN‐RNA CROSSLINKS IN RIBOSOMES: ULTRAVIOLET ACTION SPECTRA. COMPARISON WITH INACTIVATION ACTION SPECTRUM
Authors: Muel B. , Giocanti N. , Ekert B. 
Published: January 2008

Abstract— RNA‐protein crosslinking by UV of different wavelengths was studied in 70S E. coli ribosomes by three techniques: sucrose gradient centrifugation in the presence of sodium dodecyl sulfate (SDS), RNA solubilization in LiCI‐urea concentrated solutions and RNA adsorption on nitrocellulose filters in the presence of SDS.The centrifugational technique shows that the crosslinking reaction occurs in two steps, the first one corresponding to the fixation of a few protein molecules on 16 or 23 s RNAs and the second one corresponding to extensive RNA‐protein crosslinking so that most protein molecules are no longer released by SDS from 30S and 50S subunits.The initial rates for the first step of crosslinking were evaluated by the solubilization and adsorption techniques at 7 (or 6) wavelengths of irradiation between 223 and 290 mm. The action spectrum for RNA solubilization in LiCl‐urea is perturbed at 223 nm by the breakage of protein chains. The action spectrum for retention on nitrocellulose filters seems to be exempt of this defect. It corresponds at high wavelengths to a nucleic chromophore and at low wavelengths to a proteic one. This means that RNA‐protein crosslinking may occur through RNA and protein excitation. The similarity between the action spectrum for RNA retention on nitrocellulose filters and the action spectrum for inactivation of ribosomal synthesis activity suggests that RNA‐protein crosslinking may be responsible for inactivation of ribosomes by UV.
CORTICOSTEROID (METHYLPREDNISOLONE) MODULATION OF PHOTOPEROXIDATION BY ULTRAVIOLET LIGHT IN LIPOSOMES
Authors: Seligman M. L. , Mitamura J. , Shera N. , Demopoulos H. B. 
Published: January 2008

Abstract— UV irradiation of ovolecithin liposomes produced a dose dependent wave of peroxidation which reached a peak and then fell again coincident with substrate exhaustion. This correlated well with subsequent increases in membrane permeability. There was a progressive loss of unsaturated fatty acids, and when cholesterol was incorporated into liposomes, the UV produced a progressive loss of this steroid.Methylprednisolone sodium succinate, a synthetic corticosteroid, was found to inhibit this peroxidation in a dose dependent manner, also ameliorating membrane permeability increases when present during irradiation, but not able to compensate for pre‐existing damage. When cholesterol was present in the liposomes, methylprednisolone sodium succinate was also able to protect this steroid from UV peroxidative damage.The rates of reaction in this system suggested that polyunsaturated fatty acids, even when present in extremely small concentrations, underwent an initial rapid wave of peroxidation, which served to initiate the slower rate of lipoperoxidation within the bulk of mono‐ and di‐“unsaturates”. At low concentrations, the corticosteroid preferentially blocked damage to mono‐ and di‐unsaturated fatty acids, affecting the polyunsaturated fatty acids as well, at higher concentrations.This study suggests that the corticosteroid, methylprednisolone sodium succinate, possesses antioxidant properties in lipid systems subjected to free radical peroxidation.
LIGHT‐INDUCED CONFORMATIONAL CHANGES IN CATTLE RHODOPSIN AS PROBED BY MEASUREMENTS OF THE INTEFFACE POTENTIAL
Authors: Trissl H‐W. 
Published: January 2008

Abstract— A novel technique of capacitative coupling of oriented rhodopsin at a polar/apolar interface allows the time resolved investigation of conformational changes following a flash. Electric signals arise as a consequence of changes of the interface potential. A signal occurring within milliseconds behaves like the R2‐phase of the “early receptor potential” (= ERP). This response is interpreted as a conformational change of rhodopsin. No correlation of this signal is found to the spectroscopically defined metarhodopsin I‐metarhodopsin II transition.The temperature dependence of the conformational change coincides with the temperature dependence of the latency of the ‘a‐wave’ of the electroretinogram, reported by Arden and Ikeda (1968). It is suggested that the command step of visual excitation is the conformational change and not one of the spectroscopically defined photolysis steps of rhodopsin.Analysis of slower electrical signals following the fast response is in accordance with the model of a light‐induced pore formation.
ULTRAVIOLET EFFECTS ON KILLING, FRUITING BODY FORMATION AND THE SPORES OF DICTYOSTELIUM DISCOIDEUM
Authors: Ohnishi Takeo , Nozu Keiichi 
Published: January 2008

Abstract— ‐Ultraviolet effects on amoeboid cells of three strains of Dictyosrrlium discoidruin, NC‐4. γs‐13 and γs‐18. for killing. fruiting body formation, spore formation and viability of the spores were studied.The strain of γs‐13 was more sensitive to UV light for killing than NC‐4 at 10% survival. In addition. γs‐13 was the most sensitive strain among the three for fruiting body formation and spore formation. The developmental process of this organism, however, showed a large resistance to UV light when compared with the killing. The spores of γs‐13 formed after UV irradiation were mostly non‐viable, though those of γs‐18 and NC‐4 were fully viable
ELECTRONICALLY EXCITED SPECIES IN THE PEROXIDASE CATALYZED OXIDATION OF INDOLEACETIC ACID. EFFECT UPON DNA AND RNA
Authors: Vidigal Carmen C. C. , Faljoni‐Alário Adelaide , Durán Nelson , Zinner Klaus , Shimizu Yoshiaki , Cilento Giuseppe 
Published: January 2008

Abstract— The electronically excited species generated in the peroxidase (oxidase) catalyzed oxidation of the plant hormone indole‐3‐acetic acid is an excited state of indole‐3‐carboxaldehyde.The chemiexcited species is able to induce in DNA the same alterations as observed with light or with enzyme‐generated triplet acetone. The chemiexcited species can also alter r‐RNA.
PHOTOCHEMICAL REACTIONS OF CYTOSINE N‐METHYL ANALOGS IN ALCOHOLIC SOLUTION
Authors: Ekpenyong Kieran I. , Shetlar Martin D. 
Published: January 2008

Abstract— –The photochemical reactions of 1‐methylcytosine (la), 1, N4‐dimethylcytosine (Ib), and 1, N4. N4‐trimethylcytosine (Ic) in isopropanol have been investigated. In all three reactions addition of isopropanol occurs across the 5,6‐double bond of the pyrimidine ring. For example, in the case of Ir photo‐reaction with isopropanol leads to formation of 5,6‐dihydro‐6–(2‐hydroxy‐2‐propyl)‐l, N4, N4‐trimethylcytosine (IIc). In all three reactions 5,6‐dihydro‐l‐methyluracil (III) was also isolated as a product; in the case of Ic, 5,6‐dihydro‐1, N4, N4‐trimethylcytosine (IV) was isolated as well. Evidence is presented that indicates cytosine, cytidine, and 2',3'‐isopropylidene cytidine also form adducts with isopropanol. Photoinduced reaction of Ic with ethanol leads to formation of 5.6‐dihydro‐6–(l‐hydroxy‐l‐ethyl)‐l, N4. N4‐trimethylcytosine (V).Both acetone sensitization and di‐t‐butyl peroxide initiated free radical reactions of Ib with isopropanol leads to formation of an adduct identical to that formed in the unsensitized photochemical reaction of Ib with isopropanol.
PHOTOREACTIVITY OF ISOLATED PHOTOSYSTEM I PARTICLES UPON COMBINATION WITH ARTIFICIAL LIPID MEMBRANES OR TRITON X‐100 MICELLES*
Authors: GINKEL GIJS VAN 
Published: January 2008

Abstract— PS‐I particles isolated according to Shiozawa et al. (1974) show increased rates of O2‐‐ and H +‐uptake with ascorbate as electron donor upon combination with an artificial vesicular lipid membrane. The amount of increase varies depending on the reconstitution procedure used. Combination of PS‐I particles with Triton X‐100 micelles increases these photochemical activities even more. The observed proton uptake in PS‐I lipid vesicles is not caused by the well‐known proton gradient found in thylakoid membranes, since lipid vesicles containing extracted leaf Chl show the same activities and uncouplers have no effect. Because these phenomena are also caused by solubilized Chl, it is concluded that there is no obvious correlation with PS‐I activity.Proton uptake most probably is caused by oxidation of ascorbate by either singlet oxygen, superoxide or OH‐radicals formed in the light. Experimental results are obtained which indicate that Chl in lipid catalyzes formation of superoxide and singlet oxygen. However, it is not clear whether superoxide formation is caused by direct electron transport from excited Chl to oxygen or by a secondary reaction. Diphenylcarbazone disproportionation has been reported as a specific photosystem I reaction. However, PS‐I lipid vesicles and Chl‐lipid‐Triton X‐100 mixtures oxidize DPCN at comparable rates, showing that the reaction is not specific for PS‐I. Cations stimulate DPCN disproportionation in Chl‐lipid‐Triton X‐100 mixtures but do not affect the rate of P700 photooxidation at all. Therefore it is suggested that Gross and Greniers (1978) conclusion that cation regulation of PSI electron flow (studied by DPCN disproportionation of PS‐I particles in Triton X‐100 micelles) provides a fine tuning mechanism for energy transfer, has to be reevaluated.
PHOTOACOUSTIC SPECTROSCOPY AND RADIANT ENERGY CONVERSION: THEORY OF THE EFFECT WITH SPECIAL EMPHASIS ON PHOTOSYNTHESIS
Authors: Malkin Shmuel , Cahln David 
Published: January 2008

Abstract—The use of photoacoustic spectroscopy in the study of photoactive samples (photochemical, luminescent, photovoltaic) is considered. After a short explanation of the parameters important in this technique and ways of measuring them, photochemical processes are considered in detail. Relations are derived for the determination of the energy stored in photochemical products and the quantum yield for the photochemical processes.One‐ and two‐step photochemical processes are treated in detail and the dependence of the photo‐acoustically detected products on modulation frequency is considered, showing the possibility of separating reaction steps according to their rate constants. Particular attention is given to the photosynthetic process and the potential of this method for determination of energy conversion efficiencies of the different stages of photosynthesis is demonstrated. Also the use of the technique in the study of photovoltaic processes is outlined.
LIGHT‐INDUCED PERTURBATION OF AROMATIC RESIDUES IN BOVINE RHODOPSIN AND BACTERIORHODOPSIN*
Authors: Rafferty Charles N. 
Published: January 2008

Abstract—Light‐induced changes in the UV absorption spectrum of bovine rod outer segment membranes were measured by conventional difference spectroscopy and by flash photolysis methods. Different thermal intermediates of rhodopsin (lumirhodopsin, metarhodopsin I, metarhodopsin II, and meta‐rhodopsin III) have absorption spectra in the ultraviolet which differ from the rhodopsin spectrum and from each other. The spectra associated with metarhodopsin I, metarhodopsin II, and metarhodopsin III are characteristic of perturbation of a small number of tyr. and/or trp residues, most likely one trp residue. These aromatic residues are in the neighborhood of the retinal Schiff base and undergo coordinated changes of interaction with retinal during the bleaching sequence. At the metarhodopsin II stage, the magnitude of the UV spectral changes is consistent with the exposure of a previously shielded trp residue to an aqueous environment. The present results are consistent with previous spectral studies which limit the extent of light‐induced conformational changes to regions of the protein in the neighborhood of the retinal Schiff base. An analogous study was made on light‐adapted purple membranes of Halobacterium halobium. The UV absorption spectrum associated with the deprotonated Schiff base intermediate of the trans‐bacteriorhodopsin cycle is indicative, in part, of aromatic residue perturbation. However, significant changes in the secondary and tertiary structures of the bacterio‐rhodopsin protein characteristic of a delocalized conformational change are unlikely at this intermediate stage.
ACTION SPECTRA OF PHOTOPHOSPHORYLATION–I. ATP FORMATION COUPLED TO NON‐CYCLIC ELECTRON FLOW
Authors: Ginkel Gus Van , Hammans Johan W. Kleinen 
Published: January 2008

Abstract— Photophosphorylation action spectra were measured with the utmost precision to identify the different pigment forms involved in the light‐harvesting process for formation ofadenosine–5′‐triphosphate (ATP).With ferricyanide‐ions as electron acceptor freshly prepared thylakoid membranes yield a typical photosystem 2 (PS II) action spectrum peaking at 672 nm and with pronounced shoulders at 650 and 680 nm. Because ferricyanide‐ions can be reduced by both photosystems we suggest that due to the poor accessibility of these hydrophilic ions to the PS II acceptor site, the PS II electron flow is rate‐limiting. When the thylakoid membranes are aged, the maximum of the action spectrum shifts to 675 nm and bands in the spectral region690–725 nm are observed, which are generally attributed to photosystem 1 (PS I). Obviously, as a result of the aging, the rate‐limiting effect of PS II electron flow decreases and activity of both photosystems is observed.With nicotinamide adenine dinucleotide phosphate (NADP) and ferredoxin as electron acceptors also a typical PS II action spectrum is obtained peaking at 676 nm and with a sharp drop in activity at 695 nm. However, the spectrum shows a pronounced peak at706–707 nm, which is attributed to a pigment involved in the light‐harvesting for either of the two photosystems.Curve‐analysis of the action spectra suggests that four forms of Chi a exist at room temperature in the spectral region660–685 nm. However, a definite conclusion about the occurrence of different pigment forms will be drawn on the basis of combined results from this and the following publication. This is done to yield a conclusion that is statistically more reliable.ATP–adenosine‐5′‐triphosphate; BSA– bovine serum albumin; Chl–chlorophyll; DBMIB–2,5‐dibromo‐3‐methyl‐6‐isopropylbenzoquinone; DCMU–3‐(3,4)‐dichlorophenyl‐1,1‐dimethyl urea; NADP –nicotinamide adenine dinucleotide phosphate; Pi–orthophosphate‐ion; PMS–N‐methyl‐phenazonium sulphate or phenazinemethosulphate;PS–1–photosystem 1;PS–2–photosystem 2.
ACTION SPECTRA OF PHOTOPHOSPHORYLATION–II. ATP FORMATION CATALYZED BY PHENAZINEMETHOSULPHATE SUGGESTING THE INVOLVEMENT OF LONG WAVELENGTH PIGMENT FORMS IN THE LIGHT‐HARVESTING PROCESS FOR PS II AND PS I
Authors: Ginkel Gus Van , Hammans Johan W. Kleinen 
Published: January 2008

Abstract— Action spectra of phenazinemethosulfate (PMS)‐catalyzed photophosphorylation, measured under aerobic conditions without added reductants, show the involvement of both photosystem 2 (PS II) and photosystem 1 (PS I). Addition of low concentrations 3‐(3,4)dichlorophenly‐l, 1‐dimethylurea (DCMU) changes the shape of the curves and causes formation of typical PS II action spectra. This can be understood by the partial inhibition of PS II electron flow by DCMU, which therefore becomes rate‐limiting. The presence of DCMU causes a strong decrease of photochemical activity in these spectra at 638, 660 and 690 nm, which we attribute to decreasing activity of PS I pigments.Curve analysis of the action spectra suggests the presence of different Chi forms at room temperature peaking at: 641.6; 650.3; 661.2; 669.8; 677.1; 684.0 and 690.6 nm. Comparison of our data with published data from low temperature absorption spectra indicates that lowering the temperature causes a decrease in halfwidth of the absorption bands but no significant change in peak position. Our data support the hypothesis of French and co‐workers that there are four universal forms of Chi a also at 25â°C.Careful investigation of data in literature does not give evidence that the pigment peaking at 641 nm is a second form of Chi b, as is sometimes assumed.Because our action spectra show two small but distinct maxima at703–705 and718–720 nm when PS II is rate‐limiting, we also measured action spectra of PS I (reduced PMS + DCMU) and PS II (ferricyanide‐ions + 2,5‐dibromo‐3‐methyl‐6‐isopropylbenzoquinone) separately.They show, in agreement with published data, that PS I is operating more efficiently in the spectral region690–725 nm than PS II. The Chi form peaking at 690 nm is absent in the PS II action spectrum, whereas this curve has two small but distinct maxima around703–705 and718–720 nm, respectively, which are also present in the PS I action spectrum.We, therefore, suggest that light absorbed by these pigments can be transferred to either of the two photosystems, and not to PS I exclusively as is sometimes assumed.ATP,adenosine–5′‐triphosphate; BSA, bovine serum albumin; Chi, chlorophyll; DBMIB, 2,5‐dibromo‐3‐methyl‐6‐isopropylbenzoquinone; DCMU, 3‐(3,4)‐dichlorophenyl‐1,1‐dimethyl urea; NADP, nicotinamide adenine dinucleotide phosphate; Pi orthophosphate‐ion; PMS, JV‐methylphenazonium sulphate or phenazinemethosulphate; PS I, photosystem 1; PS II, photosystem 2.
PHOTOPHYSICS AND IONIC PHOTODISSOCIATION OF POLYESTERS WITH PENDANT 1‐PYRENYL GROUPS IN SOLUTION
Authors: Masuhara H. , Ohwada S. , Seki Y. , Mataga N. , Sato K. , Tazuke S. 
Published: January 2008

Abstract—Primary photoprocesses of polyesters with pendant pyrenyl groups in solution were studied by means of nanosecond laser flash photolysis method. The intrapolymer process of the Sl Sl annihilation was observed. Intense laser excitation brings about dense population of several fluorescent states in a polymer chain, and their mutual interaction leads to efficient deactivation. This process is confirmed by excitation intensity dependence of fluorescence spectra and fluorescence intensity. It was also confirmed that the T‐T absorption intensity decreases as the degree of polymerization increases. This low formation yield of the triplet state in the polyesters is ascribed mainly to the above Sl Sl interaction. In addition the polymer effect on the ionic photodissociation yield of the polyester‐electron acceptor was investigated. The yield decreases as the degree of polymerization increases. This effect is due to slow solvation processes, which may be due to low micropolarity and high microviscosily around the polymer chain.
THE INTERACTION OF CHLOROPHYLL‐A WITH DETERGENT MICELLES
Authors: Brown Robert G. , Evans E. Hilary 
Published: January 2008

Abstract—Absorption and fluorescence spectra of Chl‐a in ethanol, ethanol/water mixtures and aqueous sodium dodecyl sulphate are reported. Contrary to a previous report, it is found that Chl‐a is not solubilized in the anionic detergent as a microcrystalline form.
LONG‐RANGE TRIPLET‐SINGLET ENERGY TRANSFER FROM ENZYME GENERATED TRIPLET ACETONE TO XANTHENE DYES
Authors: Durán Nelson , Cilento Giuseppe 
Published: January 2008

Abstract—Enzyme‐generated and protected acetone transfers its energy to xanthene dyes by a nontrivial process. The relative populations of the S1 state are indicative of the operation of a heavy atom effect, being 1:15:100 for fluorescein, eosine and Rose Bengal. On the other hand Stern‐Volmer constants and kET0 values are similar for the three dyes and are remarkably higher than for collisional processes.It is tentatively suggested that at least for eosine and Rose Bengal, a triplet‐triplet cxciton transfer may occur to populate an upper triplet state of the dye followed by heavy‐atom enhanced intersystem crossing to the S1 state.