bluuebunny/crossref_metadata_2025 huggingface dataset:
DETECTION AND QUANTITATION OF THREE PHYTOCHROMES IN UNIMBIBED SEEDS OF: Avena sativa L.
Authors: Wang Yu‐Chie , Cordonnier‐Pratt Marie‐Michèle , Pratt Lee H.
Published: January 2008

Abstract—

Three phytochrome apoproteins in unimbibed seeds of Avena saliva L. were identified with monoclonal antibodies directed to, and specific for, three oat phytochromes with monomeric molecular masses of 125, 124 and 123 kDa [Wang et al., 1991, Planta 184, 96–104]. All three phytochromes were readily detected in embryo‐containing portions. Only trace amounts were found in endosperm tissue. Phytochrome photoreversibility was detected after concentration and partial purification of embryo extracts by fractionation with ammonium sulfate, indicating that at least one of these seed phytochromes had its chromophore prosthetic group bound to it. Immunoblot analyses were performed to quantitate each of the three phytochromes in unimbibed seeds. Quantitation of phytochromes in detergent‐free extracts led to serious underestimates of phytochrome contents in the unimbibed seeds. In contrast, more than 93% of each of the three phytochromes in the unimbibed seeds was extracted when a modified sodium dodecyl sulfate sample buffer was used as the extraction medium. In such extracts, we measured per embryo 1.40 ± 0.12. 1.60 ± 0.05 and 6.13 ± 0.31 ng of 125–, 124– and 123‐kDa phytochrome, respectively.
THE PHOTOPERIODIC CONTROL OF FLOWERING: PROGRESS TOWARD UNDERSTANDING THE MECHANISM OF INDUCTION
Authors: O'Neill Sharman D.
Published: January 2008

Abstract—

The mechanism of photoperiodic flower induction remains a major unsolved problem in plant development. Although it is firmly established that phytochrome is the primary photoreceptor in photoperiodic responses including flowering, the intermediate processes of induction including signal transduction, biochemistry of the induced state, and synthesis and identification of the floral stimulus are still obscure. In this review, advances in key areas of research that have contributed to our understanding of photoperiodic flower induction are discussed. These include the role of phytochrome in photoperiodic flowering, physiological characterization of the photoperiodic flowering response, the mechanism of photoperiodic time measurement during induction, and the nature of flower‐promoting and flower‐inhibiting substances. Finally, the role of alterations in gene expression in mediating photoperiodic flower induction is considered along with emerging opportunities for future research that may increase our understanding of the mechanism of flower induction.
ACRYLAMIDE QUENCHING OF THE FLUORESCENCE OF GLYCERALDEHYDE‐3‐PHOSPHATE DEHYDROGENASE: REVERSIBLE AND IRREVERSIBLE EFFECTS
Authors: Bastyns Katrin , Engelborghs Yves
Published: January 2008

Abstract— The acrylamide quenching of the tryptophan fluorescence of apo and holo glyceraldehyde‐ 3‐phosphate dehydrogenase (GAPDH) was studied. In the case of apo‐GAPDH, the steady state fluorescence quenching cannot be described by the classical Stern‐Volmer equation: strong cooperative quenching is observed. In the presence of Pi and/or cofactor NAD+ an inaccessible fraction appears. Cooperative quenching is partially suppressed in the presence of Pi and fully absent in the presence of NAD+.

The measurements of the fluorescence lifetimes of the holo‐enzyme by phasefluorometry allow the resolution of two lifetimes. The long‐lived component is quenched by acrylamide, the short‐lived component is not. Quenching induces a red shift of the steady state emission peak. The quenching parameters from the lifetime measurements allow the quantitative description of the steady state fluorescence quenching data.

In agreement with the observations of orstan and Gafni (Photochemistry and Phorobiology, (1990) 31, 725–731), we find that acrylamide causes a slow, irreversible loss of activity and a reduction of titratable thiol groups when it acts on the apo‐enzyme. This inactivation is strongly reduced in the presence of NAD+. We show that this inactivation is also slowed down by the presence of Pi, and that it is accompanied by a loss of the NAD+ binding site.

Blocking the thiol groups with 5,5'‐dithio‐bis‐(2‐nitrobenzoic acid) does not lead to a protection against the irreversible inactivation by acrylamide, showing that reactions other than thiol modifications are involved in the irreversible effect. A fraction of the inactivation can be reversed by treatment with mercapto‐ethanol.
FLUORESCENCE STUDIES WITH HUMAN EPIDERMAL GROWTH FACTOR
Authors: Ghiron Camillo A. , Eftink Maurice R. , Engler David A. , Niyogi Salil K.
Published: January 2008

Abstract— Steady‐state and time‐resolved fluorescence studies have been performed with human epidermal growth factor, a small globular protein having two adjacent tryptophan residues near its C‐terminus. Based on the relatively red fluorescence and accessibility to solute quenchers, the two tryptophan residues are found to be exposed to solvent. Anisotropy decay measurements show the dominant depolarizing process to have a sub‐nanosecond rotational correlation time indicating the existence of rapid segmental motion of the fluorescing tryptophan residues. From an analysis of the low‐temperature excitation anisotropy spectrum of the protein (and in comparison with that of tryptophan, the peptide melittin, and the dipeptide trp‐trp), it is concluded that homo‐energy transfer and/or exciton interaction occurs between the adjacent tryptophan residues. A thermal transition in the structure of the protein, which is observed by circular dichroism measurements, is not sensed by the steady‐state fluorescence of the protein. This result, in conjunction with the anisotropy decay results, indicates that the two tryptophan residues are in a highly flexible C‐terminus segment, which is not an integral part of the three‐dimensional structure of the protein. Fluorescence measurements with three site‐directed mutants also show very little variation.
PHOTOSENSITIZATION BY PHOTOFRIN II DELIVERED TO WI26VA4 SV40‐TRANSFORMED HUMAN FIBROBLASTS BY LOW DENSITY LIPOPROTEINS: INHIBITION OF LIPID SYNTHESIS AND FATTY ACID UPTAKE
Authors: Biade S. , Mazière J. C. , Mora L. , Santus R. , Morlière P. , Mazière C. , Salmon S. , Gatt S. , Dubertre L.
Published: January 2008

Abstract— Irradiation with 365 nm light of Wi26VA4 SV40‐transformed human fibroblasts cultured for 24 h in the presence of low density lipoproteins loaded with the anticancer porphyrin mixture Photofrin II resulted in a near complete inhibition of [14C]oleic acid incorporation into triacylglycerols, cholesteryl esters and phospholipids. More than 80% reduction of the fatty acid incorporation in all lipid classes was observed following an irradiation dose of 1 J/cm2. The activities of the respective acyltransferases, measured in vitro on cell homogenates, were also markedly diminished, but to a lesser extent than lipid synthesis from oleic acid. Moreover, oleic acid uptake by cells was strongly and rapidly reduced. It is suggested that the rapid inhibition of membrane phospholipid synthesis upon cell photosensitization, due to both a direct inactivation of acyltransferases and to a reduction of fatty acid utilization, could play an important role in the photocytotoxic effect of Photofrin II.
WAVELENGTH‐DEPENDENT QUANTUM YIELD FOR Z →E ISOMERIZATION OF BILIRUBIN COMPLEXED WITH HUMAN SERUM ALBUMIN
Authors: Agati Giovanni , Fusi Franco , Pratesi Riccardo , McDonagh Antony F.
Published: January 2008

Abstract— The quantum yield, φZE, for configurational photoisomerization (4Z,15Z→ 4Z,15E) of bilirubin bound non‐covalently to human serum albumin was determined (at 23 ± 2°C) by laser excitation and chromatographic analysis of products. Values obtained for photoexcitation at 465 nm were about one‐half those previously reported. The quantum yield was dependent on excitation wavelength, decreasing from a value of 0.109 ± 0.010 for excitation at 457.9 nm to a value of 0.054 ± 0.005 for excitation at 514.5 nm. The wavelength dependence is consistent with rapid transfer of excitation energy between the two non‐identical pyrromethenone chromophores of bilirubin in the singlet excited state. Since the quantum yields for photoisomerization and luminescence of bilirubin bound to serum albumin at room temperature are both low, internal conversion processes, rather than Z→E configurational isomerizations, are probably the major pathways for deactivation of photo‐excited bilirubin.
ON THE ORIGIN OF 628 nm FLUORESCENCE IN CERTAIN CHLOROPHYLL PREPARATIONS
Authors: Seely G. R.
Published: January 2008

Abstract— A fluorescence band at 628 nm seen in certain preparations of chlorophyll on polyethylene particles swollen with tetradecane comes not from an impurity of protochlorophyll in the original chlorophyll, but from a substance like protochlorophyll formed upon adsorption of chlorophyll to the particles. Much of the chlorophyll is grafted to polyethylene in the same particles by a process that does not affect the chromophore. These and other properties peculiar to the particles are tentatively ascribed to a prior free radical oxidation process in the swollen particles.
PHOTOSTATIONARY FLUORESCENCE EMISSION AND TIME RESOLVED SPECTROSCOPY OF SYMMETRICALLY DISUBSTITUTED ANTHRACENES ON THE meso AND SIDE RINGS: THE UNUSUAL BEHAVIOR OF THE 1,4 DERIVATIVE*
Authors: Brotin T. , Desvergne J.‐P. , Fages F. , Utermöhlen R. , Bonneau R. , Bouas‐Laurent H.
Published: January 2008

Abstract— Steady state and time resolved fluorescence emission properties of symmetrical dialkoxy‐anthracenes (especially substituted on the side rings) 1‐X, Y were studied in methylcylohexane. At room temperature, the fluorescence spectra of 1‐X, Y show bands in the region of 380–550 nm and quantum yields (φF) in the range of 0.2–1. The fluorescence emission decays were found to be single exponential. The determination of the intersystem crossing quantum yields (φisc) for the weakly fluorescent compounds (1–1,5, 1–1,8 and 1–2,3) demonstrates that internal conversion is negligible compared with fluorescence emission and intersystem crossing, as previously observed for other anthracene derivatives. The fluorescence emission efficiency of compounds 1‐X,Y is controlled by the relative mutual positions of the second triplet T2 (whose energy varies significantly with substitution) and the first excited singlet S1 states, respectively. An unusual solvatochromism was found for compound 1–1,4 which has a very weak permanent dipole moment in the ground state. This behavior was assigned to strong changes in the electronic densities between the excited singlet state and the ground state.
KINETIC SALT EFFECTS IN THE PHOTOCHEMICAL REACTION BETWEEN* Ru(bpy)2/3+ Fe3+
Authors: Rodríguez Amalia , Rosa Francisco F. De la , Galán Manuel , Sanchez Francisco , Moyá Maria Luisa
Published: January 2008

Abstract— The photochemical reaction between the excited state of the complex Tris‐(2,2'‐bipyridine)ruthenium(II), *Ru(bpy)2/3+ iron(III) has been studied in different concentrated electrolyte solutions. A positive salt effect is found, which is specific in that its magnitude depends upon the nature of the salt. Since the rate constants are close to the diffusion limit the possibility has been considered that the process was controlled by either activation or diffusion. The influence of the electrolyte on kact, the true activation rate constant and on kdiff, the diffusion‐controlled rate constant, has been investigated. Results indicate that in concentrated electrolyte solutions the photochemical reaction studied is mainly diffusion controlled.
DIFFERENTIAL EFFECT OF ULTRAVIOLET‐B RADIATION ON CERTAIN METABOLIC PROCESSES IN A CHROMATICALLY ADAPTING Nostoc
Authors: Tyagi Rashmi , Srinivas G. , Vyas Deepak , Kumar Ashok , Kumar H. D.
Published: January 2008

Abstract— The impact of UV‐B radiation on growth, pigmentation and certain physiological processes has been studied in a N2‐fixing chromatically adapting cyanobacterium, Nostoc spongiaeforme. A brownish form (phycoerythrin rich) was found to be more tolerant to UV‐B than the blue‐green (phycocyanin rich) form of N. spongiaeforme. Continuous exposure to UV‐B (5.5 W m‐2) for 90 min caused complete killing of the blue‐green strain whereas the brown strain showed complete loss of survival after 180 min. Pigment content was more strongly inhibited in the blue‐green strain than in the brown. Nitrogenase activity was completely abolished in both strains within 35 min of UV‐B treatment. Restoration of nitrogenase occurred upon transfer to fluorescent or incandescent light after a lag of 5–6 h, suggesting fresh synthesis of nitrogenase. Unlike the above processes, in vivo nitrate reductase activity was stimulated by UV‐B treatment, the degree of enhancement being significantly higher in the blue‐green strain. Like the effect of UV‐B on nitrogenase, 14CO2 uptake was also completely abolished by UV‐B treatment in both strains. Our findings suggest that UV‐B may produce a deleterious effect on several metabolic activities of cyanobacteria, especially in cells lacking phycoerythrin. Strains containing phycoerythrin appear to be more tolerant to UV‐B, probably because of their inherent property of adapting to a variety of light qualities.
BLUE AND ULTRAVIOLET‐B LIGHT PHOTORECEPTORS IN PARSLEY CELLS
Authors: Ensminger Peter A. , Schäfer Eberhard
Published: January 2008

Abstract— Ultraviolet‐B (UV‐B) and blue light photoreceptors have been shown to regulate chalcone synthase and flavonoid synthesis in parsley cell cultures. These photoreceptors have not yet been identified. In the present work, we studied UV‐B photoreception with physiological experiments involving temperature shifts and examined the possible role of flavin in blue and UV‐B light photoreception. Cells irradiated with UV‐B light (0.5–15 min) at 2°C have the same fluence requirement for chalcone synthase and flavonoid induction as controls irradiated at 25°C. This is indicative of a purely photochemical reaction. Cells fed with riboflavin and irradiated with 6 h of UV‐containing white light synthesize higher levels of chalcone synthase and flavonoid than unfed controls. This effect did not occur with blue light. These results indicate that flavin‐sensitization requires excitation of flavin and the UV‐B light photoreceptor. The in vivo kinetics of flavin uptake and bleaching indicate that the added flavin may act at the surface of the plasma membrane. In view of the likely role of membrane‐associated flavin in photoreception, we measured in vitro flavin binding to microsomal membranes. At least one microsomal flavin binding site was solubilized by resuspension of a microsomal pellet in buffer with high KPi and NaCl concentrations and centrifugation at 38000 g. The 38000 g insoluble fraction had much greater flavin binding and contained a receptor with an apparent KD of about 3.6 μM and an estimated in vivo concentration of at least 6.7 × 10–8M. Flavin mononucleotide, roseoflavin, and flavin adenine dinucleotide can compete with riboflavin for this binding site(s), although each has lower affinity than riboflavin. Most microsomal protein was solubilized by resuspension of the microsomal pellet in non‐denaturing detergents and centrifugation at 38 000 g; however, this inhibited flavin binding, presumably because of disruption of the environment of the flavin receptor. The parsley microsomal flavin binding receptor(s) have a possible role in physiological photoreception.
REGULATION OF PROTEIN PHOSPHORYLATION BY PHYTOCHROME IN Sorghum bicolor
Authors: Doshi Ashootosh , Aneeta  , Sopory Sudhir K.
Published: January 2008

Abstract— In vitro phosphorylation of some polypeptides was affected in extracts obtained from 5‐and 6‐day‐old plants irradiated with 5 min of red light. The phosphorylation of 55 kDa polypeptide in both 5‐ and 6‐day‐old plants, a 60 kDa, and 76 kDa polypeptide in 6‐day‐old plants and 70 kDa, 67 kDa polypeptide in 5‐day‐old plants was stimulated by red light. This effect was reversible by far‐red light. The extent of stimulation by red light and reversal by far‐red light varied for different polypeptides. No differential effect of red and far‐red light was seen on the phosphorylation of 94 and 40 kDa polypeptides. In fact, phosphorylation of 94 kDa polypeptide in 6‐day‐old plants decreased on red light irradiation. These results show that the phosphorylation or dephosphorylation of some proteins is affected by phytochrome and the effect of light is also dependent on the age of the plant.
Stentor coeruleus SHOWS POSITIVE PHOTOKINESIS
Authors: Iwatsuki Kenji
Published: January 2008

Abstract— Stentor coeruleus responds to a sudden increase in light intensity with a step‐up photophobic response (avoiding reaction), and to collimated light with negative phototaxis. The peaks of the action spectra for the photophobic response and for the phototaxis are in common, 610 nm.

5. coeruleus showed changes in its steady‐state swimming velocity induced with varying intensities of light (photokinesis). The cells swam fast in light regions but slowly in dark ones (positive photokinesis); the mean velocity of swimming was about 0.6 mm/s at 100 lx but reached about 1.0 mm/s at 50000 lx. The peak of the action spectrum for this photokinesis was about 680 nm.

The organism is the first protozoan cell reported to show three types of photoresponse: photophobic response, phototaxis and photokinesis.
HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF PIGMENTS FROM GUARD CELL PROTOPLASTS AND MESOPHYLL TISSUE OF Vicia faba L.
Authors: Karlsson P. E. , Bogomolni R. A. , Zeiger E.
Published: January 2008

Abstract— Pigments extracted from guard cell protoplasts (GCP) and mesophyll tissue from Vicia faba L., were separated by high performance liquid chromatography and identified by absorbance spectroscopy. Water soluble, UV‐absorbing pigments, presumably flavonoids, were present in the GCP in large amounts. Chlorophyll and carotenoid content in GCP and mesophyll tissue was qualitatively similar, with both cell types having chlorophylls, xanthophylls and carotenes. Some quantitative differences were found. Beta‐carotene was less abundant in the GCP, while some of the xanthophylls, notably violaxanthin and lutein‐antheraxanthin, were more abundant. Lutein and neoxanthin occurred in similar amounts. The similarity between the action spectrum for the stimulation of stomatal conductances by blue light and the absorbance spectrum of guard cell carotenoids points to carotenoids as putative photoreceptors in the stomatal response to blue light.
SITE‐DIRECTED MUTAGENESIS OF THE LH2 LIGHT‐HARVESTING COMPLEX OF Rhodobacter sphaeroides: CHANGING βLys23 TO Gin RESULTS IN A SHIFT IN THE 850 nm ABSORPTION PEAK
Authors: Fowler Gregory J. S. , Crielaardt Wim , Visschers Ronald W. , Grondelle Rienk van , Hunter C. Neil
Published: January 2008

The present study describes the construction of a Rhodobacter sphaeroides light‐harvesting (LH2) mutant in which the charged residue βSLys23 is changed by site‐directed mutagenesis to a Gin residue, and the characterization of the resulting mutant complex by a range of spectroscopic techniques. In the 77 K absorption spectrum of the mutant, the peak equivalent to the 850 nm peak in the wild‐type membrane is blue‐shifted by approximately 18 nm to 837 nm; except for this blue‐shift, the 77 K. fluorescence excitation and emission spectra and the circular dichroism spectrum of the mutant are very similar to the equivalent spectra from the wild‐type membranes, suggesting that the mutation βLys23 → Gin probably does not cause any major changes in the conformation or aggregation state of these membranes. Possible causes of the 18 nm blue‐shift in the absorption spectrum are discussed.
CAROTENOID‐TO‐BACTERIOCHLOROPHYLL SINGLET ENERGY TRANSFER IN CAROTENOID‐INCORPORATED B850 LIGHT‐HARVESTING COMPLEXES OF Rhodobacter sphaeroides R‐26.1
Authors: Frank Harry A. , Farhoosh Roya , Aldema Mila L. , DeCoster Beverly , Christensen Ronald L. , Gebhard Ronald , Lugtenburg Johan
Published: January 2008

Four carotenoids, 3,4,7,8‐tetrahydrospheroidene, 3,4,5,6‐tetrahydrospheroidene, 3,4‐dihydrospheroidene and spheroidene, have been incorporated into the B850 light‐harvesting complex of the carotenoidless mutant, photosynthetic bacterium, Rhodobacter sphaeroides R‐26.1. The extent of π‐electron conjugation in these molecules increases from 7 to 10 carbon‐carbon double bonds. Carotenoid‐to‐bacteriochlorophyll singlet state energy transfer efficiencies were measured using steady‐state fluorescence excitation spectroscopy to be 54 ± 2%, 66 ± 4%, 71 ± 6% and 56 ± 3% for the carotenoid series. These results are discussed with respect to the position of the energy levels and the magnitude of spectral overlap between the S, (2′AJ state emission from the isolated carotenoids and the bacteriochlorophyll absorption of the native complex. These studies provide a systematic approach to exploring the effect of excited state energies, spectral overlap and excited state lifetimes on the efficiencies of carotenoid‐to‐bacteriochlorophyll singlet energy transfer in photosynthetic systems.
FLUORESCENCE AND CIRCULAR DICHROISM STUDIES ON THE PHYCOERYTHROCYANINS FROM THE CYANOBACTERIUM
Authors: Sai P. S. Maruthi , Siebzehnrübl S. , Mahajan S. , SCHEER H.
Published: January 2008

Two phycoerythrocyanin (PEC) fractions have been obtained from the phycobilisomes of the cyanobac‐terium Westiellopsis prolifica ARM 365. They have been characterized by absorption, fluorescence and circular dichroism spectroscopy. One of them is spectroscopically similar to a PEC trimer known from other organisms. Whereas efficient energy transfer from its violin (α‐84) to the cyanin (β‐84, 155) chromophores is efficient in the trimer (αβ it is impeded after dissociation to the monomer (α,β). A second fraction of PEC which we earlier termed PEC(X) (Maruthi Sai et al., Photochem. Photobiol.55,119–124, 1992), exhibited the spectral properties similar to that of the α‐subunit of PEC from Mastigocladus laminosus. With this highly photoactive fraction, the circular dichroism spectra of the violobilin chromophore in both photoreversible states were obtained.
STUDIES ON CHROMOPHORE COUPLING IN ISOLATED PHYCOBILIPROTEINS. IV. FEMTOSECOND TRANSIENT ABSORPTION STUDY OF ULTRAFAST EXCITED STATE DYNAMICS IN TRIMERIC PHYCOERYTHROCYANIN COMPLEXES*
Authors: Hucke Mathias , Schweitzer Gerd , Holzwarth Alfred R. , Sidler Walter , Zuber Herbert
Published: January 2008

The excited state dynamics of trimeric phycoerythrocyanin has been studied by two‐color femtosecond transient absorption spectroscopy with a time‐resolution better than 200 fs. Upon selective excitation of the short‐wavelength phycobiliviolin chromophore at 575 nm absorption bleachings are observed. An isotropic ultrafast decay of the initial bleaching of 585 ± 40 fs has been resolved at short detection wavelength (578 nm). Upon stepwise increase of the detection wavelength up to 617 nm, the bleaching showed a delayed rise above 593 nm with rrice=380–580 fs. All other isotropic kinetic components in this wavelength range were longer than 100 ps. The ultrafast component is discussed in terms of an energy transfer process from the α‐84 phycobiliviolin chromophore to the β‐84 chromophore in adjacent monomer subunits of the trimer. It is concluded that the β‐155 chromophore is the longest‐wavelength chromophore. Exciton relaxation between closely spaced chromophore pairs is discussed as an alternative interpretation for the ultrafast component.
DELAYED MICROSECOND LUMINESCENCE OF PHYCOBILISOMES
Authors: Frackowiak Danuta , Planner Alfons , Dudkowiak Alina
Published: January 2008

The time‐resolved luminescence spectra (in the microsecond range) of phycobilisomes and biliproteins in buffer and polymer matrix were measured in the temperature range from 8 K. to 293 K. Delayed luminescence located in the same spectral region as prompt fluorescence of investigated samples (DLF) and the long‐wavelength delayed emission in the720–760 nm range (DL1) was observed. The temperature and viscosity dependencies of DLF and DL1 luminescences were different, but both do not have uniexponential decays and are not quenched by oxygen. This means that delayed luminescence could be generated without the participation of the triplet states, or the chromophores could be shielded by protein against interaction with oxygen. The linear dependence of delayed luminescence on exciting light intensity shows that delayed luminescence is monophotonically induced.

It seems that both DLF and DL1 are related to electron‐cation recombination, which yields excited singlet states. The DLF is emitted from the first excited singlet state of biliprotein chromophores and DL1 from the same state of the excimers or from the triplet state of some groups of chromophores. Ionization energy of chromophores can be lowered as a result of their interactions with the environment. Delay of emission is due to the trapping or solvation of electrons. Every type of biliprotein consisting of phycobilisomes possesses its own “trap” and can emit the DL. In the case of native phycobilisomes a competition between the excitation energy trapping and transfer occurs.
STRUCTURES OF THE BERGAMOTTIN PHOTOPRODUCTS
Authors: Martin M.‐T. , Valla A. , Giraud M. , Brouard J.‐P. , Morliere P. , Haigle J. , Santus R.
Published: January 2008

The extensive use of bergamot oil in perfumery and cosmetics led us to study the photoreactivity of 5‐geranoxypsoralen (bergamottin), the major chromophore in this oil. Structure determination of the bergamottin photoproducts was achieved using extensive NMR techniques including two‐dimensional NMR: 1H‐13C correlation by long‐range coupling, 1H‐1H correlation spectroscopy (COSY) and 1H‐1H COSY phase sensitive (COSYPH). Bergaptol is formed according to the well‐known fragmentation of allyl‐aryl ethers. The other photoproducts arise from an intramolecular [2 + 2] photocycloaddition and appeared as an equimolecular mixture of diastereomeric cyclobutyl derivatives. The relative configurations were determined by nuclear Overhauser effect analysis. These structures were further corroborated by X‐ray crystal analysis. The facile formation of an intramolecular cyclobutyl derivative in bergamottin might prevent the intermolecular cyclobutane adduct formation with pyrimidine DNA bases responsible, in part, for phototoxicity of psoralens.
THE PHOTOPHYSICS OF MONOMERIC BACTERIOCHLOROPHYLLS c AND d AND THEIR DERIVATIVES: PROPERTIES OF TRIPLET STATE AND SINGLET OXYGEN PHOTOGENERATION AND QUENCHING
Authors: Krasnovsky A. A. , Cheng P. , Blankenship R. E. , Moore T. A. , Gust D.
Published: January 2008

Measurements of pigment triplet‐triplet absorption, pigment phosphorescence and photosensitized singlet oxygen luminescence were carried out on solutions containing monomeric bacteriochlorophylls (Bchl) c and d, isolated from green photosynthetic bacteria, and their magnesium‐free and farnesyl‐free analogs. The energies of the pigment triplet states fell in the range 1.29‐1.34 eV. The triplet lifetimes in aerobic solutions were200–250 ns; they increased to 280 pL 70 us after nitrogen purging in liquid solutions and to 0.7‐2.1 ms in a solid matrix at ambient or liquid nitrogen temperatures. Rate constants for quenching of the pigment triplet state by oxygen were (2.0‐2.5) × 109 M−1 s−1. which is close to 1/9 of the rate constant for diffusion‐controlled reactions. This quenching was accompanied by singlet oxygen formation. The quantum yields for the triplet state formation and singlet oxygen production were55–75% in air‐saturated solutions. Singlet oxygen quenching by ground‐state pigment molecules was observed. Quenching was the most efficient for magnesium‐containing pigments, kq= (0.31‐1.2) × 109 M−1 s−1. It is caused mainly by a physical process of singlet oxygen (1O2,) deactivation. Thus, Bchl c and d and their derivatives, as well as chlorophyll and Bchl a, combine a high efficiency of singlet oxygen production with the ability to protect photochemical and photobiological systems against damage by singlet oxygen.
ULTRAVIOLET RESONANCE RAMAN SPECTRA OF PHYTOCHROME: A COMPARISON OF THE ENVIRONMENTS OF TRYPTOPHAN SIDE CHAINS BETWEEN RED LIGHT‐ABSORBING AND FAR‐RED LIGHT‐ABSORBING FORMS
Authors: TOYAMA AKIRA , NAKAZAWA MIKI , MANABE KATSUSHI , TAKEUCHI HIDEO , HARADA ISSEI
Published: January 2008

Ultraviolet resonance Raman spectra of phytochrome in the red light‐absorbing form (Pr) and the far‐red light‐absorbing form (Pfr) are reported. The spectra excited at 240‐nm provide structural information about the protein part of phytochrome. The protein contains only a very small amount of β‐sheet structure and most of the tyrosine side chains are located in hydrophobic environments. Indole rings of tryptophan (Trp) interact with neighboring groups in the Pr form and these interactions become weaker with the conversion from Pr to Pfr. Some Trp side chains of Pfr are surrounded by aliphatic groups but such is not the case in Pr. These changes in the environment occur at the same time as changes in orientation of Trp side chains. Our observations suggest that interactions between Trp residues and the tetrapyrrolic chromophore occur in the Pr form and that the strength of these interactions diminishes in the Pfr form.
LIPID PHASES IN RENAL BRUSH BORDER MEMBRANES REVEALED BY LAURDAN FLUORESCENCE*
Authors: Levi Moshe , Wilson Paul V. , Cooper Otis J. , Gratton Enrico
Published: January 2008

Steady‐state fluorescence properties of 6‐dodecanoyl‐2‐dimethylaminonapththalene (Laurdan) have been used to determine the coexistence of separate lipid‐phase domains in apical brush border membrane vesicles isolated from the rat renal cortex. The temperature dependence of generated polarization has been utilized to quantitate the lipid phases. Finally, the effect of cholesterol enrichment on these parameters has been studied. The results indicate the coexistence of lipid‐phase domains in brush border membranes based on the values of the generalized polarization and assuming that the membrane state can be described by coexistence of gel and liquid crystalline state. At 37°C, approximately19–32% of the brush border membrane lipids are in the gel phase, and cholesterol enrichment causes a further concentration‐dependent increase in the gel phase of brush border membrane lipids.
USE OF LAURDAN FLUORESCENCE IN STUDYING PLASMA MEMBRANE ORGANIZATION OF POLYMORPHONUCLEAR LEUKOCYTES DURING THE RESPIRATORY BURST*
Authors: Fiorini R. , Curatola G. , Kantar A. , Glorgi P. L. , Gratton E.
Published: January 2008

The changes in plasma membrane polarity of polymorphonuclear leukocytes (PMN) during the activation of the respiratory burst were investigated by measuring the steady‐state fluorescence emission spectra of 2‐dimethylamino(6‐lauroyl) naphthalene (Laurdan), which is known to be incorporated at the hydrophobic‐hydro‐philic interface of the bilayer, displaying spectral sensitivity to the polarity of its surroundings. Laurdan shows a marked steady‐state emission blue shift in nonpolar solvents, with respect to polar solvents. Our results show a blue shift of the fluorescence emission spectra of Laurdan during activation of PMN with phorbol myristate acetate or AT‐formyl‐methionyl‐leucyl‐phenylalanine. These results suggest that the activation of the respiratory burst of PMN is accompanied by a decrease in polarity in the hydrophobic‐hydrophilic interface of the plasma membrane.
INVOLVEMENT OF DRUG‐DERIVED PEROXIDES IN THE PHOTOTOXICITY OF NAPROXEN and TIAPROFENIC ACID
Authors: Castell Jose V. , Gomez‐Lechon Maria J. , Grassa Carmina , Martinez Luis A. , Miranda Miguel A. , Tarrega Pilar
Published: January 2008

Photodegradation of naproxen and tiaprofenic acid in aqueous buffered solutions leads to decarboxylated products with ethyl, 1‐hydroxyethyl and/or acetyl side chains. The photomixtures obtained in the presence of oxygen were clearly more toxic to cultured hepatocytes than those obtained under anaerobic conditions. This effect was more noticeable in the case of naproxen. Based on the composition of the oxygenated photomixtures and the relative toxicity of the different photoproducts, it is possible to account for most of the observed toxicity in the case of tiaprofenic acid but not in the case of naproxen. This is explained as a result of the presence of drug‐derived peroxidic species in the photomixtures and their contribution to the observed toxicity. Peroxides were determined by the peroxidase‐catalyzed oxidation of dichlorodihydrofluorescein to its fluorescent analog. The amount of peroxides present in naproxen photomixtures was much higher than in the case of tiaprofenic acid. A dose‐dependent depletion of intracellular glutathione was observed when hepatocytes were incubated with peroxide‐containing naproxen photomixtures. This effect was prevented by the addition of catalase or jV‐acetylcysteine to the culture medium.
SEASONAL TRENDS IN ERYTHEMAL and CARCINOGENIC ULTRAVIOLET RADIATION AT MID‐SOUTHERN LATITUDES1989–1991
Authors: Smith Gerald J. , White Malcolm G. , Ryan Ken G.
Published: January 2008

A network of solar carcinogenic/erythemal ultraviolet radiometers has been established in New Zealand. Daily integrated irradiances of this biologically harmful ultraviolet radiation for 1989, 1990 and 1991 are reported from radiometers located at Wellington (41°S) and Christchurch (43.5°S) and for 1990 and 1991 from the Auckland (37°S) radiometer. Although the monitoring program has not been running sufficiently long to discern any long‐term changes in levels of solar ultraviolet radiation, shorter term trends are apparent, which are attributed to a seasonal cycle in levels of ozone at midlatitudes and changes in atmospheric aerosols.
ABSORPTION SPECTRA OF LEAVES CORRECTED FOR SCATTERING and DISTRIBUTIONAL ERROR: A RADIATIVE TRANSFER and ABSORPTION STATISTICS TREATMENT
Authors: Fukshansky L. , Remisowsky A. Martinez V. , McClendon J. , Ritterbusch A. , Richter T. , Mohr H.
Published: January 2008

A comprehensive treatment of light propagation through intact leaves based on the theories of radiative transfer and absorption statistics was used to calculate the theoretical absorption spectra of the chlorophyll‐containing particles under conditions of multiple scattering and pigment spatial distribution equivalent to those in a leaf. These spectra were compared with the experimental in vivo spectra of leaves and in vitro spectra of chlorophyll‐protein complexes extracted form these leaves. We conclude that the main discrepancies between the in vivo and in vitro spectra are apparently due to the optical artifacts specific for light propagation in leaves‐multiple scattering and distributional error. Alterations of the pigment properties upon extraction significantly contribute to these discrepancies. The method has an estimated accuracy of about 10% and can be applied to derive the intrinsic optical properties of the photosynthetic mechanism in a leaf, as well as for the systematic study of their changes in the course of light adaptation.
REINVESTIGATION OF THE PHOTOPHYSICS OF 2‐(2′‐HYDROXY‐4′‐DIETHYLAMINOPHENYL)BENZOTHIAZOLE
Authors: Chou Pi‐Tai , Martinez Marty L.
Published: January 2008

Abstract— The photophysical properties of 2‐(2′‐hydroxy‐4′‐diethylaminophenyl) benzothiazole (HABT) have been investigated by steady‐state and time‐resolved spectroscopies. In n‐heptane HABT exhibits both normal and tautomer emissions with ∼equal fluorescence intensity at room temperature, in contrast to a previous report in which negligible tautomer emission was observed. The normal/tautomer (400/500 nm) ratio of emission intensity increases as the temperature decreases. Two possible excited‐state intramolecular proton transfer (ESIPT) mechanisms are proposed, which cannot be resolved at the present stage. One proposed mechanism incorporates state mixing between ‐OH and ‐N(C2H5)2 charge transfer states, resulting in a significant energy barrier for ESIPT. An alternative mechanism is also proposed in which fast proton tunneling may take place between enol and keto forms, which are in equilibrium in the excited singlet state.
In vitro GRANULOMA FORMATION BY SPLEEN CELLS TREATED WITH PSORALEN PLUS LONG‐WAVE ULTRAVIOLET RADIATION
Authors: Okamoto Hiroyuki , Guo Zaipei , Imamura Sadao
Published: January 2008

Abstract— In vitro gransulomas ar induced by culturing murine spleen cells with artificial microparticles, dextran beads. In the presence of 0.5 μg/mL 8‐methoxypsorlen, UVA radiation (0.2‐2.0 J/cm2 suppressed granuloma formatin in a UVA dose‐ dependent manner. The dose of PUVA did not affect the cell viability as assessed by trypan blue exclusion. The time course of granuloma formation in 0.5 J/cm2 PUVA‐treated cells was similar to that of normal spleen cells, with a miximum granuloma index at day 3 of culture, althought a49–63% suppression of granuloma formation was observed in PUVA‐treated, adherent cells even when they were cultured with normal nonadherent cells. These data suggests that PUVA alters macrophages, resulting in the suppression of granuloma formation in vitro
CONSTRUCTION AND CHARACTERIZATION OF HYBRID LUCIFERASES CODED BY lux GENES FROM Xenorhabdus luminescens AND Vibrio fischeri
Authors: Xi Lei , Tu Shiao‐Chun
Published: January 2008

Abstract— Molecular cloning techniques were employed to obtain hybrid luciferases with their α and β subunits encoded by luxA and luxB genes, respectively, from Xenorhabdus luminescens strain HW or Vibrio fischeri. Although the two wild‐type luminous bacteria are phylogenetically diverged, the hybrid luciferase Xf comprising an α from V. fischeri and a β from X. luminescens HW were both functional in bioluminescence. Their general kinetic properties were close to the wild type enzymes from which the α subunit was derived. The X. luminescens HW enzyme is distinct in having a high optimal temperature for in vitro bioluminescence, a high thermal stability and a sensitivity to aldehyde substrate inhibition. Comparisons of the Xf and VI hybrid luciferases with the two wild‐type enzymes indicated that these unusual properties of the X. luminescens HW luciferase originated primarily from the α subunit.
LASER PHOTOLYSIS STUDIES OF SUPEROXIDE ADDUCTS OF COBALT(II) AND ZINC(II) PORPHYRINS IN DIMETHYLFORMAMIDE
Authors: Hoshino Mikio , Seki Hiroshi , Yamaji Minoru , Hama Yoshimasa
Published: January 2008

Abstract— Photochemistry of superoxide adducts of cobalt(II) and zinc(II) porphyrins has been studied by laser photolysis. It was found that the former in dimethlformamide photodissociates the superoxide anion radical, O2‐, with the quantum yield of 0.5 ± 0.05 at the excitation wavelenths 355 and 532 nm, and the latter gives flurescence and the triple state without giving rise to the photodissociation of O2‐
VISUALIZATION OF ULTRAVIOLET LIGHT‐INDUCED THYMINE DIMERS IN DNA BY IMMUNOELECTRON MICROSCOPY
Authors: Udono Masako U. , Hori Makoto , Hirayama Michiko , Yoshida Hikotaro , Suematsu Tadashi , Suematsu Takashi , Mori Toshio , Matsunaga Tsukasa , Mizuno Terumi , Nikaido Osamu
Published: January 2008

Abstract— To see the damage of DNA due to ultravoilet‐B more distinctly, immunoelectron microscopic studies using a monoclonal antibody against cyclobutane‐type thymine dimers were performed. As a result, we could detect the existence of thymine dimers on human genomic DNA and pUC18 plasmid DNA visually. This technique can be useful to locate the photoproducts formed on DNA.
ESTABLISHMENT and CHARACTERIZATION OF A MONOCLONAL ANTIBODY RECOGNIZING THE DEWAR ISOMERS OF(6–4)PHOTOPRODUCTS
Authors: Matsunaga Tsukasa , HATAKEYAMA YURI , Ohta Michi , Mori Toshio , Nikaido Osamu
Published: January 2008

Abstract— We established a monoclonal antibody(DEM–1) that recognizes UV‐induced DNA damage other than cyclobutane pyrimidine dimers or(6–4)photoproducts. The binding ofDEM–1 antibody to 254 nm UV‐irradiated DNA increased with subsequent exposure to UV wavelengths longer than 310 nm, whereas that of the 64M‐2 antibody specific for the(6–4)photoproduct decreased with this treatment. Furthermore, the increase inDEM–1 binding was inhibited by the presence of the 64M‐2 antibody during the exposure. We concluded that theDEM–1 antibody specifically recognized the Dewar photoproduct, which is the isomeric form of the(6–4)photoproduct. TheDEM–1 antibody, however, also bound to DNA irradiated with high fluences of 254 nm UV, suggesting that 254 nm UV could induce Dewar photoproducts without subsequent exposure to longer wavelengths of UV. Furthermore, an action spectral study demonstrated that 254 nm was the most efficient wavelength for Dewar photoproduct induction in the region from 254 to 365 nm, as well as cyclobutane dimers and(6–4)photoproducts, although the action spectrum values in the U V‐B region were significantly higher compared with those for cyclobutane dimer and(6–4)photoproduct induction.
FOURIER‐TRANSFORM INFRARED SPECTROSCOPIC STUDY OF THE STRUCTURE OF CHLOROPHYLL a and CHLOROPHYLL b IN HIGHLY DILUTE WATER‐SATURATED CARBON TETRACHLORIDE SOLUTIONS
Authors: Okada Kouichi , Uehara Kaku , Ozaki Yukjhiro
Published: January 2008

Abstract— Fourier‐transform (FT) infrared (IR) absorption spectra have been measured for chlorophyll a (Chi a), chlorophyll b (Chi b), pheophytin a (Pheo a), and pheophytin b (Pheo b) in highly dilute (10‐5‐10‐6M) water‐saturated carbon tetrachloride solutions. Frequencies of IR bands due to C=O stretching modes of the 9‐keto group indicate that Chi a assumes largely a dimeric structure in the concentrated (10‐2‐10‐3M) water‐saturated carbon tetrachloride solutions but it remains mostly a monomer with one or two coordinated water molecules in dilute (10‐5‐10‐6M) solutions. Although it seems that Chi b also assumes predominantly dimeric form in concentrated solutions and monomelic form in dilute solutions, the relative intensity change of two C=O stretching bands ascribed to the free and coordinated 3‐aldehyde groups with decreasing concentration suggests that the aldehyde group is also involved in formation of the dimer. The relative intensity of two C=O stretching bands due to the free and coordinated aldehyde groups changes significantly for Pheo b in water‐saturated carbon tetrachloride solutions. This observation suggests that some of Pheo b also assume dimeric form via the aldehyde group in concentrated solutions.
EFFECTS OF MUTAGENETIC SUBSTITUTION OF PROLINES ON THE RATE OF DEPROTONATION and REPROTONATION OF THE SCHIFF BASE DURING THE PHOTOCYCLE OF BACTERIORHODOPSIN
Authors: Zhang Yi N. , El‐Sayed Mostafa A. , Stern Lawrence J. , Marti Thomas , Mogi Tatushi , Khorana H. Gobind
Published: January 2008

Abstract— Membrane‐buried proline residues are found in many transport proteins. To study their roles in the structure and function of bacteriorhodopsin (bR), effects of the individual substitutions ofPro–50,Pro–91 andPro–186 on the deprotonation and reprotonation kinetics of the Schiffbase (SB) were determined by flash photolysis. The obtained rate constants and the amplitudes of the slow and fast components were compared with those of ebR (wild‐type bR, the native protein that is expressed in Escherichia coli). The deprotonation rates of PSB were found to be 10 times faster than that of ebR for P50A, P91A and P91G mutants, and 4 times faster for the P50G mutant. These mutations also increased the initial reprotonation rate of the SB, although the overall change in the reprotonation rate is not as significant as that in the deprotonation rate. Our results indicate thatPro–50 andPro–91, as well asPro–186, are important for the proton‐pumping function of bR.
PHOTOBIOLOGICAL CHARACTERIZATION OF A SPORE GERMINATION MUTANT dkgl WITH REVERSED PHOTOREGULATION IN THE FERN Ceratopteris richardii
Authors: Cooke Todd J. , Hickok Leslie G. , VANDERWOUDE William J. , Banks Jo Ann , Scott Rodney J.
Published: January 2008

Abstract— This paper describes the mutant dkgl in the fern Ceratopteris richardii, which shows rapid germination in darkness but is markedly inhibited by white light. Action spectra plotted at 10 nm intervals from 400 to 800 nm are presented for germination responses of wild‐type and mutant spores to photon flux densities of 0.004, 0.04 and 0.4 jtmol/mVs. The action spectra for wild‐type spores exhibit a sharp phytochrome‐mediated peak at 660 nm, a broad peak from 670 to 740 nm resulting from an apparent high irradiance response and no germination below 560 nm. In the corresponding action spectra for mutant spores, the blue region displays rather complex fine structure with prominent minima at 450 and 470 nm, which suggests that cryptochrome is unaltered in these spores. The region from 550 to 640 nm shows the greatest inhibition of spore germination, but this region exhibits no obvious fine structure, which argues rather strongly against the possibility of a unique photoreceptor being active in mutant spores. The mutant spectra resemble the wild‐type spectra in the region from 650 to 800 nm, and thus phytochrome seems normal in the mutant spores. The dkgl mutation appears to act late in the phytochrome transduction pathway where a hypothetical coupling protein may regulate the light‐sensitive step in spore germination.
THE USE OF LIQUID CHROMATOGRAPHY‐MASS SPECTROMETRY TO MONITOR THE ALLOMERIZATION REACTIONS OF CHLOROPHYLL a and PHEOPHYTIN a:m IDENTIFICATION OF THE ALLOMERS OF PHEOPHYTIN a
Authors: Rahmani ALI , Eckardt Christian B. , Brereton Richard G. , Maxwell James R.
Published: January 2008

Abstract— This paper reports a new method for monitoring the allomerization reactions of chlorophyll a and pheo‐phytin a. Complex mixtures are generated from illuminating pure compounds and monitored using both diode array high‐performance liquid chromatography (DAD‐HPLC) and liquid chromatography‐mass spectrometry (LC‐MS). LC‐MS allows molecular weight and fragment ion analysis of significant HPLC peaks. Five products of the degradation of chlorophyll a can be simultaneously detected in a mixture, namely the monohydroxy allomer, the methoxylactone allomer, pheophytin a and the two corresponding allomers of the pheophytin. It is demonstrated that more than one pathway must be involved in the in vitro photodegradation of chlorophyll a as shown by the simultaneous existence of several intermediates.
PHOTOSENSITIZATION OF MITOCHONDRIA BY LIPOSOME‐BOUND PORPHYRINS
Authors: Ricchelli Fernanda , Gobbo Silvano , Jori Giulio , Moreno Giuliana , Vinzens Françoise , Salet Christian
Published: January 2008

We have compared the photodynamic activities of hematoporphyrin (HP) and protoporphyrin (PP) on isolated rat liver mitochondria by measuring the decline of the respiratory control ratio (RCR) after irradiation at 365 nm. Before addition to the respiratory mcdium, the dyes were dissolved in phosphate‐buffered saline (PBS) or incorporated into unilamellar liposomes of dipalmitoyl‐phosphatidylcholine (DPPC), sometimes enriched with cholesterol (Chol) or cardiolipin (Card), which are naturally present in mitochondrial membranes. Chol and especially Card strongly increase the porphyrin uptake by mitochondria. In all experimental conditions, PP is taken up by mitochondria to a higher extent than HP. Nevertheless, under conditions giving the same amount of mitochondriabound dye, HP is a morc efficient photosensitizer than PP. As the efficiency of singlet oxygen production has been shown to be equivalent for the two porphyrins in monomeric state, the resulting photobiological effects are explained in terms of different localization of HP and PP in the mitochondrial membrancs. In particular, HP preferentially localizes in the protein‐rich polar domains of the inner mitochondrial membrane, whereas PP dissolvcs in the lipid regions of the mcmbrancs.