bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOCHROMIC SYNERGISM OF BACTERIORHODOPSIN‐ and HALORHODOPSIN‐MEDIATED PHOTOPHOSPHORYLATION IN Halobacterium halobium*
Authors: WAGNER Gottfried , Traulich Bernhard , Hartmann KarlM. , Oesterhelt Dieter 
Published: January 2008

Quantitative action spectroscopy was performed in Halobacterium halobium. using four suited pigment mutants, namely the bacteriorhodopsin and halorhodopsin positive mutant strain M‐l (BR+, HR+), the bacteriorhodopsin positive but halorhodopsin negative strain M‐18 (BR+, HR‐), the bacteriorhodopsin negative but halorhodopsin positive strain L‐33 (BR‐, HR+), and the bacteriorhodopsin and halorhodopsin negative strain L‐07 (BR‐, HR+).The approached questions were: First, photoenergetic synergism of halorhodopsin and bacteriorhodopsin in intact cells; second, photochromism and cellular function of the blue light‐absorbing intermediates, i.e. M‐412 and HR‐410 in bacteriorhodopsin and in halorhodopsin, respectively.Dark‐adapted cells of mutant strain M‐l show wavelength‐dependency of quantum yield of photo‐phosphorylation, φATP. An 1.4‐fold enhancement was found at 575 nm wavelength where the long wavelength absorbance bands of bacteriorhodopsin and halorhodopsin intersect. The enhancement vanished after a 30 min pulse of orange light (600 Wm‐2 bandpass from 495 to 750 nm), but was restored after a 30 min pulse of blue light (100 Wm‐2 bandpass from 325 to 480 nm). Photoreversibility of this enhancement probably reflects phototransformation of halorhodopsin from its ground state into its inactive intermediate, HR‐410, and vice versa. The halorhodopsin‐mediated enhancement with maximum quantum yield of photophosphorylation, φATP= 0.06, i.e. a quantum requirement of = 17 photons/ATP, is partly substituted by a rise in phosphate potential and explained in terms of a voltage‐regulated gating effect on the H+‐driven ATP‐synthase, superimposed on the chemiosmotic mechanism of energy coupling.The blue‐absorbing photochromic intermediate, M‐412 of bacteriorhodopsin, dissipates light energy upon photoexcitation that is reflected by a spectral decline in quantum yield of photophosphorylation to a minimum value of = 0.01 at 415 nm, i.e. a quantum requirement of = 100 photons/ATP.
FURTHER CHARACTERIZATION OF ANESTHETIC‐TREATED PURPLE MEMBRANES
Authors: Henry Nathalie , Beaudoin Normand , Baribeau Johanne , Boucher François 
Published: January 2008

Abstract— The absorption maximum of bacteriorhodopsin is shifted from 568 nm to 480 nm when halogenated volatile anesthetics (enflurane; halothane) are added to purple membranes. Analysis of the rate of formation of this new species upon addition of the anesthetic and of the back‐formation of native bacteriorhodopsin upon its removal indicate that in purple membranes, the dark‐adapted chromophore is much less reactive than its light‐adapted counterpart. Lipid‐soluble molecules thus have a lower accessibility to the dark‐adapted chromophore.In addition, activity of the 480 nm bacteriorhodopsin was investigated. Flash and steady‐state photolysis experiments reveal that this blue shifted chromophore has full photochemical activity. It has a meta‐intermediate absorbing maximally at 380 nm. The photocycle ofBR–480 is mainly characterized by a slow decay of the “O” intermediate, enabling the direct observation of the branching reaction between the “M” intermediate and the parentBR–480 pigment.
SPECTROSCOPIC INVESTIGATION OF DIH YDRONICOTIN AMIDES‐II. DIHYDRONICOTINAMIDE ADENINE DINUCLEOTIDE COMPLEXES WITH DEHYDROGENASES
Authors: BAUMGARTEN BRIGITTE , HONES JOACHIM 
Published: January 2008

Abstract— Detailed investigations are reported on absorption and fluorescence of dihydronicotinamide adenine dinucleotide in binary and ternary complexes with lactate dehydrogenase or malate dehydrogenase and substrates or substrate analogues. Polarity of the active site, as extracted from fluorescence maxima, reveals two types of dihydronicotinamide environment comparable to an aqueous and a dimethyl sulfoxide medium, respectively. Absorption maxima argue for absence of carboxamide/ acceptor hydrogen bonds in general. Vibrational fine structure in the absorption bands of some ternary complexes indicates the absence of carboxamide/donor hydrogen bonds. In these complexes, rotation of dihydronicotinamide within the binding site is established by means of fluorescence anisotropy decay.These findings are interpreted in terms of the interaction between active site and dihydronicotinamide being highly specific for each individual complex. At the same time, they render any direct analogies between binding of reduced and oxidized coenzyme, and also between abortive and productive ternary complexes, highly problematical.
RHYTHMS IN BLUE‐LIGHT‐INDUCED CONIDIATION OF WILD TYPE AND A MUTANT STRAIN OF Trichoderma harzianum
Authors: DEITZER GERALD F. , Horwitz BENJAMIN A. , Gressel Jonathan 
Published: January 2008

Abstract— Trichoderma harzianum normally requires light for conidiation. Conidiation of colonies grown in continuous light does not appear to be rhythmic, but sharp banding patterns are formed under light/dark cycles. A single pulse of blue light produces a sharp band of conidia that forms where the growing edge of the mycelia is located at the time when the light is given. A period of about 24 h is required following the light pulse to produce mature conidia. During this time colonies are insensitive to further induction by light. The fluence required to produce 50% saturation varies by a factor of about 3 depending on when the pulse is given. This change of sensitivity is rhythmic with a period length of approximately 27 h when grown on medium containing deoxycholate.The pattern of conidiation in a mutant strain (B119), which is able to form conidia in the dark, is rhythmic and the period length is dependent on the composition of the medium. Addition of deoxycholate to the medium increased the interval between dark bands from 12 to 24 h. The rhythmic banding is suppressed in constant light and a double banding pattern is produced in light/dark cycles. A pulse of blue light induces a band of conidia in this mutant, as in the wild type, but it also delays the reappearance of the dark banding pattern. The extent of this delay depends on when the pulse is given and, although the period length of the dark conidiation rhythm is affected by deoxycholate, the effect of blue light on its phase is not. Of the various rhythmic responses of Trichoderma studied here. the delay in reappearance of the dark banding pattern in B119 is the most promising for further detailed studies, for example of wavelength and temperature dependence.
INTERACTION OF ENZYME‐GENERATED SPECIES WITH CHLOROPHYLL‐a AND PROBES BOUND TO SERUM ALBUMINS
Authors: Bohne Cornelia , Faljoni‐Alario Adelaide , Cilento Giuseppe 
Published: January 2008

Abstract— The interaction of serum albumin‐bound acceptors with enzyme‐generated and protected triplet species was studied in two types of systems. Chlorophyll‐a bound to bovine and human serum albumins is efficiently excited by enzymatically generated triplet acetone and acetaldehyde. When the Chl‐a concentration is much lower than that of the albumin the interaction occurs with chlorophyll in an aggregate in which one Chl‐a is surrounded by several protein molecules. When the Chl‐a concentration is higher than that of the protein, the aggregate contains the proteins and fluorescent chlorophylls in a 1:1 ratio. The excess chlorophylls, although able to interact with the donors, are not fluorescent.In another study, probes bound to various specific sites of serum albumins were used as quenchers of the enzymatically generated triplet acetone. The efficiency of quenching by all the bound probes is equal and in one case even stronger than for the free probes.A model for the interaction of the excited species contained in the enzyme with the acceptor(s) located in the protein is proposed.The present results provide further evidence that enzyme‐generated and protected triplet carbonyl species can interact through a collisional process with acceptors bound to or constituents of macromolecules.
THE CONTROL OF METABOLISM BY BLUE LIGHT IN Acetabularia mediterranea—II. SELECTIVE TRANSLATIONAL CONTROL AND DIFFERENTIAL DEGRADATION OF ENZYMES
Authors: Nickl Bernhard , Söllner Bruno , Schmid Rainer 
Published: January 2008

Abstract— During prolonged continuous irradiation with red light the specific activity of uridine 5′‐diphosphoglucose (UDPG) pyrophosphorylase (uridine 5′‐triphosphate: glucose 1‐phosphate uridylyl‐transferase EC 2.7.7.9) decreased in Acetabularia mediterranea Lamouroux (=A. acetabulum (L.) Silva). Subsequent blue light restored the original activity within a comparatively short period of 3 to 4 days. Computer‐aided quantitative evaluation of density labelling experiments showed that the synthesis of the enzyme was accelerated about four‐fold during the period of activation by blue light. A similar increase in the rate of synthesis was found for hydroxypyruvate reductase (EC 1.1.1.81), a control enzyme that showed no blue light‐dependent changes in the specific activity under these conditions. The increase in the rate of enzyme synthesis was caused by an overall stimulation of the cytosolic translation. Degradation of UDPG pyrophosphorylase was unaffected by blue light, while the half life of hydroxypyruvate reductase was shortened about two‐fold compared to continuous red light. Thus, degradation of proteins appears to be selectively light dependent in Acetabularia.Model calculations for enzyme amount and enzyme synthesis were carried out using the measurements of enzyme activity, rates of cytosolic protein synthesis, and degradation constants of the enzymes. Assuming that activities represented amounts of the given enzymes, these calculations indicated a selective activation of UDPG pyrophosphorylase synthesis by blue light since it did not coincide with the overall stimulation of protein synthesis in the cytosol, in contrast to hydroxypyruvate reductase.
FLAVINS IN LIPOSOMES‐ANOMALOUS PHOTOCHEMICAL EFFECTS AT HIGH PIGMENT CONCENTRATIONS
Authors: HEELIS P. F. , PHILLIPS G. O. , LENCI F. , COLOMBETTI G. 
Published: January 2008

Abstract Laser flash photolysis of riboflavin tetrabutyrate incorporated in lecithin liposomes has been studied as a function of the number of flavins per liposome, NRFTB.Both the flavin triplet decay rate and its susceptibility to quenching by oxygen and glycyl‐tyrosine depend markedly on the value of NRFTB. The results are interpreted on the basis of the existence of two distinct locations for the flavin chromophore within the liposome structure.
RECOVERY OF VIRAL CAPACITY IN IRRADIATED EXPONENTIALLY GROWING CELLS
Authors: Sayed Nadira I. , Rupert Claud S. 
Published: January 2008

Abstract—Exponentially growing cells of the PtK‐2 line (ATCC No. CCL56, from the marsupial Potorous tridactylus) require protein and RNA synthesis in a limited period following UV‐radiation damage for optimal recovery as colony formers [Overberg et al. (1988) Mutat. Res. 194, 83–92]. Overall behavior suggests the operation of damage‐induced recovery processes. The capacity of confluent cell monolayers for infection with unirradiated herpes simplex virus 1 (HSV‐1) is sharply reduced by UV‐irradiation. We have followed capacity changes in exponentially growing cells after irradiation and varying amounts of photoreactivation by means of an infectious center assay. These changes closely parallel changes of colony formation. Spontaneous recovery of capacity in the dark occurs over approximately the same time period that the UV sensitivity of colony formation depends on macromolecular synthesis. The effect of photoreactivation is complementary rather than additive to this recovery, suggesting that the dark recovery in this period concerns pyrimidine dimers in cell DNA.
DIFFERENCE SPECTRA OF THE OXIDIZED INTERMEDIATES IN THE PHOTOSYNTHETIC OXYGEN‐EVOLVING SYSTEM: EVIDENCE FOR A SMALL S0→S1 ABSORPTION CHANGE
Authors: Lavergne Jearome 
Published: January 2008

Abstract—A consensus has emerged in the recent literature on the fact that the UV difference spectrum of the first oxidation step (S0→ S1) of the photosynthetic oxygen‐evolving complex is significantly different and generally smaller than the spectra of the higher oxidation steps (S0→ S1and S2→ S3). Discrepancies still persist, however, notably in the 300 nm region where the S0→ S1 change was either reported to be markedly smaller than the other changes, or, at variance, to have a similar amplitude. A novel approach is proposed here for estimating the ratio of these changes, requiring no estimate of the Kok model parameters, such as the initial S0/S1ratio, or damping coefficients. This was achieved by comparing the absorption difference between two fully deactivated states, differing only in their S0/S1, distribution, with the flash‐induced changes measured from these states. The results show that, at two wavelengths around 300 nm, the S0→ S1 change is at least 4 times, and probably 5–6 times smaller than the S0→ S1change.
INTERACTION OF DIBUCAINEHCl LOCAL ANESTHETICS WITH BACTERIORHODOPSIN IN PURPLE MEMBRANE: A SPECTROSCOPIC STUDY
Authors: LIN C. T. , CHYAN Y. G. , KRESHECK G. C. , JR HERBERT C. BITTING , EL‐SAYED M. A. 
Published: January 2008

AbstractSeveral spectroscopic techniques (absorption, emission, transient absorption and differential scanning calorimetry–DSC) were used to investigate the deprotonation of dibucaine‐HCl in a hydrophobic environment, and the interaction sites and mechanisms of the local anesthetic dibucaine‐HCl on bacteriorhodopsin (bR) in purple membrane. The important results are summarized as follows: (1) the visible absorption features of native (γmax= 568 nm) and deionized (γmax= 608 nm) bR are sensitive to the amount of dibucaine‐HCl added; (2) the emission spectrum of dibucaine‐HCl embedded in the retinal‐free mutant bR is similar to that of dibucaine free base in Triton X‐100 micellar solutions; (3) the phosphorescence emission of dibucaine at 77 K is completely quenched by bR and the fluorescence quenching rate for the incorporated dibucaine‐HCl in bR was determined as kδ= 4.09 × 1013M‐1s‐1; (4) the incorporation of dibucaine‐HCl in bR inhibits the slow component rate of formation of M412 and decreases the amount of M412 formation in the photochemical cycle of bR; and (5) the thermal stability of native bR was measured by DSC in the presence and absence of dibucaine and yielded an endothermic transition at 95.9 ± 1.0°C with 13.6 J/g (3.25 ± 0.12 cal/g) of enthalpy changes. All observations suggest that the action site of the local anesthetic, dibucaine‐HCl, is near or at the chromophore, i.e. the retinal Schiff base of bR. The anesthetic action on bR purple membrane is probably via a specific site binding, but not a conformational mechanism.
AMERICAN SOCIETY FOR PHOTOBIOLOGY (ASP) HISTORY: 1983–1987
Authors: Jagger John 
Published: January 2008

SummaryOverall, this pentad (1983‐87) was a time of relative stability. Numbers of papers published in Photochemistry and Photobiology (P&P) was nearly constant (Fig. 1).Total membership was constant, then rose 13% over the last two years (Table 4). Sustaining membership, however, has tripled in recent years.Finances showed some disturbing trends. Two of the last three years showed deficits (Table 6), and the Fund Balance was lower in the last two years than in the previous six. Library subscriptions to P&P (a major source of funding for the Society) continued its steady drop of about 12 per year since 1974 (Fig. 3).These trends suggest that the Society was beginning to grow toward the end of the period, but also becoming less financially sound.The two major functions of the ASP are to publish P&P and to hold the Annual Meeting. Both of these activities were carried out successfully. During this pentad other activities were also proceeding at a healthy pace. Efforts were made to be more responsive to such public issues as suntan salons, and to have symposia or lectures on environmental problems, such as damage to the stratospheric ozone layer. Efforts were made to advertise the Society more widely, and to encourage photochemical and photobiological publications. A research award and an archives were established. The new format of the Newsletter, its columns on history, and its airing of such issues as the role of ASP in world photo‐biology, added to the effectiveness and the prestige of the Society.
FORMATION OF INTRAMOLECULAR EXCIMER IN ARYL PHOSPHATES AND THEIR REACTIVITIES
Authors: Okamoto Yoshiki , Nakamura Mitsunobu , And Min Shi , Takamuku Setsuo 
Published: January 2008

Abstract—The fluorescence spectra of bis(4‐methoxyphenyl) hydrogen phosphate and tris(4‐meth‐oxyphenyl) phosphate showed two emission bands. A longwavelength emission band arose from the intramolecular excimer of two 4‐methoxyphenyl groups and a short band arose from a 4‐methoxyphenyl group itself. There was a good correlation between the relative intensity of the monomer/excimer emissions and the quantum yield of 4,4′‐dimethoxybiphenyl, which was an intramolecular coupling product.
Molecular Mechanism of Photosensitization XI. Membrane Damage and DNA Cleavage Photoinduced by Enoxacin
Authors: Sortino S. , Condorelli G. , De Guidi G. , Giuffrida S. 
Published: January 2008

AbstractThe photosensitizing activity of enoxacin, 1‐ethyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(1‐piperazinyl)‐1,8‐naphthyridine‐3‐carboxilic acid (ENX), toward membranes and DNA has been studied, taking into account human erythrocyte photohemolysis, unilamellar liposome alterations and plasmid pBR322 DNA photocleavage. Hydroxyl radicals and an aromatic carbene generated from ENX photode‐fluorination seem to be the active intermediates involved in the photosensitization process. The steady‐state photolysis products do not participate in the process. The mechanism of photosensitization responsible for the membrane damage depends on the oxygen concentration and follows a different path with respect to that operative for DNA cleavage. Between oxygenated radicals, the hydroxyl seems the species mainly responsible for membrane damage, whereas DNA cleavage is mainly produced by the carbene intermediate. A molecular mechanism of the photosensitization induced by ENX is proposed.
Magnetic Field Effects on the Dynamics of Radical Pairs: The Partition Effect in Vesicles
Authors: Kleinman Mark H. , Shevchenko Tatiana , Bonne Cornelia 
Published: January 2008

AbstractA combination of product studies and laser flash photolysis (LFP) was used to study the recombination of radical pairs derived from dibenzyl ketone (DBK) and its methyl derivative. Two sizes of vesicles consisting of dioctade‐cyldimethylammonium chloride (DODAC) were generated. In the product studies, irradiation of the ketone led to a substantial overall cage effect both above and below the phase‐transition temperature. However, LFP results demonstrate that no geminate reactions, that correspond to the reactions of radicals generated from the same precursor molecule are occurring even at room temperature. The results are discussed in terms of the partition effect where the cage effect is determined by the differences in the solubility of the radical inside the vesicle bilayer and in the aqueous phase. In small (30 nm diameter) vesicles, most of the random recombination occurs after re‐entry of the radicals into the bilayer, whereas in large (˜150 nm) liposomes, a significant proportion of the recombination reactions takes place in the bulk water. This work demonstrates that magnetic fields can efficiently alter the reactivity of radicals involved in nongeminate pathways and further supports the use of the radical pair mechanism to explain possible effects of magnetic fields in biological systems.
Fluorescence Photobleaching of ALA‐induced Protoporphyrin IX during Photodynamic Therapy of Normal Hairless Mouse Skin: The Effect of Light Dose and Irradiance and the Resulting Biological Effect
Authors: Robinson Dominic J. , de Bruijn Henriëtte S. , van der Veen Nynke , Stringer Mark R. , Brown Stanley B. , Star Willem M. 
Published: January 2008

ABSTRACTThe photobleaching of 5‐aminolaevulinic acid (ALA)‐induced protoporphyrin IX (PpIX) was investigated during superficial photodynamic therapy (PDT) in normal skin of the SKH HRt hairless mouse. The effects of light dose and fluence rate on the dynamics and magnitude of photobleaching and on the corresponding PDT‐induced dam‐age were examined. The results show that the PDT damage cannot be predicted by the total light dose. Photo‐bleaching was monitored over a wide range of initial PpIX fluorescence intensities. The rate of PpIX photo‐bleaching is not a simple function of fluence rate but is dependent on the initial concentration of sensitizer. Also, at high fluence rates (50–150 mW/cm2, 514 nm) oxygen depletion is shown to have a significant effect. The rate of photobleaching with respect to light dose and the corresponding PDT damage both increase with decreasing fluence rate. We therefore suggest that the definition of a bleaching dose as the light dose that causes a 1/e reduction in fluorescence signal is insufficient to describe the dynamics of photobleaching and PDT‐induced dam‐age. We have detected the formation of PpIX photoproducts during the initial period of irradiation that were themselves subsequently photobleached. In the absence of oxygen, PpIX and its photoproducts are not photo‐bleached. We present a method of calculating a therapeutic dose delivered during superficial PDT that demonstrates a strong correlation with PDT damage.
Significance of Dosimetry in Photodynamic Therapy of Injured Arteries: Classification of Biological Responses
Authors: Adili Farzin , van Eps Randolph G. Statius , LaMuraglia Glenn M. 
Published: January 2008

AbstractWith conflicting results in the literature on the ability of photodynamic therapy (PDT) to inhibit intimal hyperplasia (IH), the present study systematically investigated the effects of drug and light dosimetry on the biologic responses in the artery wall. The rat common carotid artery was balloon‐injured and pressurized with benzopor‐phyrin‐derivative monoacid ring (BPD). Then, PDT was performed with an external laser at different fluences and the biologic responses of the artery wall were histologically examined at 24 h and at 2 weeks. Photodynamic therapy effects on injured arteries can be classified into four stages: low‐dose PDT using 0.5 (ig/mL BPD at 50 J/cm2(stage I) resulted in incomplete cell eradication and significant IH at 2 weeks. Irradiation with 100 J/cm2at the same BPD concentration (stage II) completely eradicated the cells in the artery wall at 24 h but still led to IH at 2 weeks. However, 25 (tg/mL BPD at 100 J/cm2(stage in) resulted in total cell eradication at 24 h and inhibition of IH at 2 weeks. In contrast, high‐dose PDT with 25 μg/mL BPD and 200 J/cm2(stage TV) led to thrombus development and vascular occlusion at 24 h. These data, demonstrating the different stages of PDT effects on injured arteries, emphasize the critical importance of appropriate PDT dosimetry for the effective inhibition of IH.
Stepwise Solid‐Phase Synthesis of Nucleopeptides
Authors: Grandas Anna , Marchán Vicente , Debéthune Laurent , Pedroso Enrique 
Published: January 2008

AbstractPhosphodiester‐linked peptide‐oligonucleotide conjugates (nucleopeptides) are obtained by stepwise solid‐phase procedures. The peptide is first assembled on a suitably derivatized solid matrix and the oligonucleotide is subsequently elongated at the free hydroxyl group of the linking amino acid. Temporary acid‐labile and permanent base‐labile protecting groups are combined. Careful choice of the protection scheme is required to prevent and minimize side reactions that may degrade the target molecule. Curr. Protoc. Nucleic Acid Chem. 31:4.22.1‐4.22.54. © 2007 by John Wiley & Sons, Inc.