bluuebunny/crossref_metadata_2025 huggingface dataset:
AFFINITY‐CONTROLLED TRIPLET ENERGY TRANSFER FROM p‐BENZOYLBENZYL‐BOVINE SERUM ALBUMIN TO LOW MOLECULAR WEIGHT QUENCHERS
Authors: GLOVER George I. , Mariano Patrick S. , Hildreth Robert A.
Published: January 2008

Abstract— Methods for the controlled synthesis of modified protein photosensitizers which maximize affinity‐controlled energy transfer are discussed. Modified proteins containing covalently linked benzophenone groups were prepared by the reaction of bovine serum albumin with p‐benzoylbenzyl bromide under conditions limiting the number and locations of the introduced benzophenone chromophores. The mechanism of energy transfer responsible for quenching of triplet photochemical reactions of the modified proteins was explored using water soluble quenchers. In addition, methods were employed to determine the magnitude of the contribution of the affinity‐controlled mechanism for energy transfer in these systems. The utility of sodium‐cis‐8‐methylene‐4,9‐decadienoate as a triplet energy transfer indicator for macromolecular systems was demonstrated using the modified proteins as sensitizers. The trienoic acid was prepared starting with the known 4‐methylene‐5‐hexenal by the Wittig reaction with 3‐ethoxycarbonylpropylidene triphenylphosphorane followed by saponification. Triplet sensitized irradiation of this trienoic acid using p‐benzoylbenzyltriethylammonium chloride as sensitizer led to production of endo‐ and exo‐1‐vinyl‐5‐(3‐carboxyethyl)bicyclo[2.1.1]hexane along with the trans acid. Characterization of the bicyclohexane products was made on the basis of spectroscopic evidence. Results demonstrate that quenching of the intramolecular photoreactions of the modified proteins by trienoic acid must be a result of triplet energy transfer, since irradiation of these modified proteins in the presence of the trienoic acid salt led to the characteristic triplet photoproduct mixture.
CHLOROPLAST BIOGENESIS. XXIII. THE CONVERSION OF EXOGENOUS PROTOCHLOROPHYLLIDE INTO PHOTOTRANSFORMABLE PROTOCHLOROPHYLLIDE IN VITRO*
Authors: Mattheis J. R. , Rebeiz C. A.
Published: January 2008

Abstract— An in vitro assay is described for the quantitative conversion of nonphototransformable protochlorophyllide into phototransformable protochlorophyllide. The assay involves: (a) the conversion of exogenous nonphototransformable protochlorophyllide into phototransformable protochlorophyllide in the dark, and (b) the quantitative monitoring of this conversion by the disappearance of the phototransformable protochlorophyllide as it is converted to chlorophyllide a by a single, 15 s illumination. This was achieved under conditions where no significant photodestruction of protochlorophyllide occurred. The formation of phototransformable protochlorophyllide from nonphototransformable protochlorophyllide in vitro was further demonstrated by the conversion of exogenous nonphototransformable [14C]protochlorophyllide into [14C]chlorophyll. This was achieved in three steps: (a) the conversion of nonphototransformable [14C]protochlorophyllide into phototransformable [14C]protochlorophyllide in the dark; (b) the conversion of phototransformable [14C]protochlorophyllide into [14C]chlorophyllide a by a single 15 s illumination; and (c) the esterification of the newly formed [14C]chlorophyllide a to yield [14C]chlorophyll. The extent of these reactions was monitored by the incorporation of the 14C‐label into chlorophyll. About 96% of the radioactivity in the [14C]chlorophyll fraction was found in [14C]chlorophyll a.
THE PHOTOSENSITIZED OXIDATION OF SULPHIDES
Authors: Laver H. S. , MacCallum J. R.
Published: January 2008

Abstract— The rates of photosensitized oxidation of a number of sulphides were determined under standard conditions in 1, 1, 2,2‐tetrachloroethane and in methanol. It was found that the ratio of the rates of reaction in the two solvents was not constant for different sulphides and that t‐butyl sulphide does not react in methanol. It is inferred that the presence of an H atom in the α position is essential for reaction in polar solvents and an appropriate mechanism is suggested. The results indicate that reaction in chlorinated solvents may take place by a different mechanism which possibly involves H‐abstraction by triplet sensitizer.
CHEMIENERGIZED SPECIES IN PEROXIDASE SYSTEMS
Authors: Cilento Giuseppe , Durán Nelson , Zinner Klaus , Vidigal Carmen C. C. , Oliveira Olga M. M. Faria , Haun Marcela , Fauoni Adelaide , Augusto Ohara , Baptista Roberto Casadei de , Bechara Etelvino J. H.
Published: January 2008

Abstract— Several hemeprotein‐catalyzed reactions generate products of the type expected from the cleavage of a high energy intermediate. For some systems, the formation, in high yield, of a carbonyl compound in its excited triplet state has been firmly established on the basis of (i) equivalence of the chemiluminescence and phosphorescence spectra of the expected products; (ii) energy transfer to sensitizers containing heavy atoms and (iii) occurrence of photoproducts. The excited species appears to be generated within the enzyme and shielded from quenching by oxygen. It may be quenched, however, via long‐range triplet‐singlet energy transfer.

This work strongly supports our hypothesis that excited electronic states are also formed in biological systems which are not necessarily bioluminescent. One of the functions which peroxidases may thus fulfill might be the utilization of the potential of photochemistry in the absence of light.
STEROL METABOLISM. XLII. ON THE INTERCEPTION OF SINGLET MOLECULAR OXYGEN BY STEROLS
Authors: Smith Leland L. , Stroud Jonathan P.
Published: January 2008

Abstract— The use of cyclic 1,3‐dienes and polycyclic aromatic hydrocarbons as xenobiotic substrates for the interception of electronically excited (singlet) molecular oxygen (1O2) in biological systems is reviewed and criticized, and the possibility of utilization of reactive endogenous substrates for 1O2 interception is considered. The common sterols, cholesterol, 5α‐cholest‐7‐en‐3β‐ol, and 5α‐lanost‐8‐en‐3β‐ol each give oxidation products with 1O2 different from those with ground‐state molecular oxygen that can be distinguished from one another by simple chromatographic means.
ON THE PHOTOSENSITIZING PROPERTIES OF N‐FORMYLKYNURENINE AND RELATED COMPOUNDS
Authors: Pileni Marie‐Paule , Santus René , Land Edward J.
Published: January 2008

Abstract— The photochemical and photosensitizing properties of N‐formylkynurenine (FK) and related compounds have been investigated using the laser flash photolysis technique by exciting water solutions with 265 nm or 353 nm radiation. The FK molecules in their first excited singlet state readily react with water leading probably to OH formation. FK triplet state reacts with many biological compounds including vitamins, amino acids and nucleic acid bases. The semi‐reduced FK thus formed can, in turn, reduce substrates such as cytochrome c or O2.
COMPARATIVE STUDY OF OXIDATION OF NUCLEIC ACID COMPONENTS BY HYDROXYL RADICALS, SINGLET OXYGEN AND SUPEROXIDE ANION RADICALS
Authors: Cadet Jean , Teoule Robert
Published: January 2008

Abstract— Superoxide radicals, singlet oxygen and hydroxyl radicals are individually or in combination involved in radiation or photochemical processes and in various enzymatic reactions. The reactivity and the mechanism of reaction of these oxygen species with some biologically significant DNA components were investigated through the characterization of the final oxidation products.

Superoxide radicals appear to be unreactive with purine and pyrimidine 2'‐deoxyribonucleosides. However, the autoxidation reaction of 6‐hydroxydopamine leads to extensive degradation of thymine through the intermediary of hydroxyl radicals. Chemically and microwave‐discharge generated singlet oxygen oxidation is specific to 2'‐deoxyguanosine. The main oxidized products of these reactions were also characterized as well as an as yet unidentified nucleoside in the methylene‐blue photooxydation of 2‐deoxyguanosine. These results, in addition to specific deuterium effect experiments, lend support to the involvment of singlet oxygen (type II mechanism) in the methylene‐blue photosentization. No singlet oxygen effect was observed in aqueous irradiated system.
AN OSCILLATING SYSTEM REGULATING DEVELOPMENT OF PLANTS
Authors: Gregory Anne , Klein Attila O.
Published: January 2008

Phytochrome conversion shifts the developmental pattern of dark‐grown bean (Phaseolus vulgaris) seedlings. Red light was found to initiate rapid oscillations in a system that links illumination with subsequent growth. A single 8 s flash of red light increased the average leaf weight measured 24 h later by 8%. When total illumination was kept constant but the interval between two 4 s flashes was varied, the resulting leaf weight increase was not uniform but depended on the length of the interval between flashes and showed a series of deep minima followed by sharp maxima. Weight increase at the maximum was 60% greater than at the minimum. The minimum‐maximum transitions recurred every 45 s for at least 22 min. Four s of far red light interposed between the two red flashes abolished the oscillation. Temperature between 15 and 30°C had no significant influence on the period of the oscillation but the period varied directly with the duration of the initial red flash. A 2 s initial flash resulted in a 35 s period, while 40 s of red light caused a 2 min period. Oat (Avena sativa) and radish (Raphanus sativus) seedlings were found to possess similar oscillating mechanisms of growth regulation. The lack of pronounced temperature effects as well as our other findings, suggest that this oscillating system may participate in the time measuring as well as growth regulating mechanisms by which phytochrome controls circadian periodicity and development.
EFFECT OF CHLORIDE ON CHLOROPHYLL PHOTOCHEMISTRY IN SOLUTION: ENHANCEMENT OF CATION RADICAL AND SEMIQUINONE YIELDS
Authors: Tollin Gordon , Rizzuto Frank
Published: January 2008

Abstract—Illumination with red light at low temperatures of a degassed ethanol solution of chlorophyll and ferric chloride reversibly produces an EPR signal due to the chlorophyll cation radical (Chl+). The magnitude of this signal is about ten times larger than is obtained with chlorophyll alone. When benzoquinone is also present, an EPR signal due to Chl+ and the neutral semiquinone radical (QH.) is photoproduced. The semiquinone signal is about five times larger than in the absence of ferric chloride. Both of these systems show first order radical decay when the light is turned off, suggesting that radical complexes are being formed. These results indicate that iron is capable of serving as an electron transfer bridge between chlorophyll and quinone.
A GENERAL METHOD FOR THE IDENTIFICATION OF PRIMARY REACTIONS IN SENSITIZED PHOTOOXIDATIONS*
Authors: Kraljic I. , Mohsni S. El , Arvis M.
Published: January 2008

Abstract— A kinetic method for the identification of primary reactions in sensitized photooxidations is described. It is based on the calculation of Fractions of primary reactions of triplet sensitizer (3S) and singlet oxygen (1O2) as a function of substrate concentration (A) and on the comparison of experimental and theoretical curves. The theoretical curve that coincides with the experimental one indicates the mechanism of the chemical change observed. Only the quenching rate constants of 3S and 1O2 are needed for this calculation. The method enables one to distinguish the free radical and 1O2 mechanism. Applications of the method with 3‐indole acetic acid, 1‐histidine and N‐3 using phenosafranine as the sensitizing dye (aqueous solutions, pH 7.C7.2) are described. The chemical change followed in these experiments is the bleaching of p‐nitrosodimethylaniline (RNO) which gives precise and reproducible results. The bleaching of RNO is induced by the presence of some substrates which produce reactive intermediates with an oxidizing character. The kinetic method can be applied to any chemical change observed in different systems of sensitized photooxidations. The quantum yield of 3S and 1O2 formation need not be known.
DNA SINGLE‐STRAND LESIONS DUE TO ‘SUNLIGHT’ AND UV LIGHT: A COMPARISON OF THEIR INDUCTION IN CHINESE HAMSTER AND HUMAN CELLS, AND THEIR FATE IN CHINESE HAMSTER CELLS
Authors: Elkind M. M. , Han Antun
Published: January 2008

Abstract— It has been shown that the lethal properties of germicidal UV light (254 nm) and sunlight‐simulating near UV light are qualitatively different (Elkind et al., 1978). Further to compare these two radiations, the induction of single‐strand DNA breaks (i.e. frank breaks plus alkali‐labile lesions) was measured in two cell lines. Equal numbers of breaks in Chinese hamster cells require a dose of UV 5.5% of a near UV dose but in HeLa cells a UV dose of 7.6% of a near‐UV dose is required. The rate of break production by these radiations is about 1/10‐th of that due to X‐rays when a comparison is made on an equal killing dose basis. The inventory of breaks in Chinese hamster cells was also followed and was found to be characteristically different for UV compared to near UV light. These data indicate that significant differences exist, at a molecular level, in the effects produced by ultraviolet and sunlight‐simulating light, and further emphasize the need for caution in attempting to extrapolate from observed molecular or biological effects due to the former to those to be expected from the latter.
THE WAVELENGTH DEPENDENCE OF ULTRAVIOLET ENHANCED REACTIVATION IN A MAMMALIAN CELL‐VIRUS SYSTEM
Authors: Coohill Thomas P. , James Leslie C. , Moore Sharon P.
Published: January 2008

Abstract— The effect of UV radiation in the wavelength region 230 nm to 302 nm on the ability of an irradiated mammalian cell to reactivate UV‐irradiated mammalian virus was tested. An action spectrum for radiation enhanced reactivation (RER) is presented. The shape of the action spectrum points to a combined nucleic acid‐protein target for UV radiation effects on this cellular parameter. An analysis of the results of others involving the biochemical and photobiological events involved in RER does not allow us to distinguish which macromolecule is the major contributor to this effect. Studies involving an analogous phenomenon in bacteria (Weigle reactivation) imply that RER and WR may involve similar mechanisms.
EVENTS SURROUNDING THE EARLY DEVELOPMENT OF EUGLENA CHLOROPLASTS. 12. SPECTROSCOPIC EXAMINATION OF THE PROTOCHLOROPHYLL(IDE) PHOTOTRANSFORMATION IN INTACT CELLS*
Authors: Kindman L. Allen , Cohen Charles E. , Zeldin Michael H. , Ben‐Shaul Yehuda , Schiff Jerome A.
Published: January 2008

Abstract— Absorption measurements in the 600–720 nm region of dark‐grown cells of Euglena gracilis Klebs var. bacillaris Cori were made in vivo at room temperature using computer‐assisted spectrophotometry. Dark‐grown wild‐type cells have a prominent absorption maximum at 634 nm due to protochlorophyll(ide) absorption. Upon illumination, the absorption at 634nm decreases and a peak appears at 674nm, representing the phototransformation of protochlorophyll(ide) to chlorophyll(ide). Using difference spectroscopy, the resynthesis in the dark of protochlorophyll(ide) by previously‐illuminated wild‐type dark‐grown cells was found to begin at about 10min after illumination and reached completion by about 25 min, the amount of protochlorophyll(ide) resynthesized being equivalent to that of dark‐grown cells. Resynthesis of protochlorophyll(ide) following a second illumination follows the same kinetics, indicating that protochlorophyll(ide) resynthesis is under tight regulation, possibly via feedback control. Cells of dark‐grown wild‐type and W3BUL, a mutant lacking protochlorophyll(ide) contain a component absorbing at 658 nm which does not undergo phototransformation when examined by difference spectroscopy at room and liquid N2 temperatures.

Following the phototransformation of protochlorophyll(ide) 634 to chlorophyll(ide) 674, the chlorophyll(ide) 674 shifts to shorter wavelengths, ultimately to 671 nm. Possible relationships among the various spectroscopic forms of protochlorophyll(ide) and chlorophyll(ide) at room temperature and liquid N2 temperature in Euglena and higher plants are presented. It is concluded that Euglena, unlike older, etiolated higher plants, contains only protochlorophyll(ide) 634, making it an excellent system in which to examine the phototransformation of this pigment species in the absence of other forms.
MECHANISM OF THE PHOTOCHEMICAL REACTION OF DIPHENYLAMINES WITH CARBON TETRACHLORIDE
Authors: Wyrzykowska K. , Grodowski M. , Weiss K. , Latowski T.
Published: January 2008

Abstract. The quantum yields of HCI (φHC1) formation have been measured for the photolysis of N‐methyldiphenylamine (MeDPA), triphenylamine (TPA) and diphenylamine (DPA) in the presence of CCl4 in polar solvents. The quantum yields of N‐methylcarbazole formation (φmφca) have also been determined for the system MeDPA‐CCl4. With increasing CCl4 concentration, φHCl increases as φMeCA decreases, and φHCl reaches maximum values 2.7 at 1 M CCl4. Using laser photolysis, transient spectra have been recorded for MeDPA in the absence and presence of CCl4 in polar and non‐polar solvents, and for TPA. Transient absorption due to the triplet states and photocyclization products (without CCU), exciplexes, the (C6H5)2 NCHi radical, the MeDPA+ cation radical, the (TPA+., CCl4) ion pair, and the TPA+ cation radical have been identified. The mechanistic implications of these results are discussed.
FLASH PHOTOLYSIS OF BOVINE SERUM ALBUMIN: IDENTIFICATION AND DECAY KINETICS OF TRANSIENT INTERMEDIATES
Authors: White M. , Kuntz R. R. , Ghiron C. A. , Volkert W. A.
Published: January 2008

Abstract. Using the method of flash photolysis, the triplet of the single indole side chain of human serum albumin was detected at room temperature. In a nitrogen saturated solution, this species was found to decay exponentially for over a factor of ten with a lifetime τ 0.5 ms. Analogous experiments, reported here, with bovine serum albumin yield a non‐exponential decay which may be decomposed into two components. The yield of the longer lived triplet, with an average τ of ∼6 ms, is significantly enhanced by addition of a 20 fold excess of sodium dodecyl sulfate or 1 M Br‐. The yield of the shorter lived triplet, τ 0.4 ms, is unaffected by these treatments as was previously observed for the single indole in HSA. Thus, the short lived triplet may be assigned to the indole in BSA which is homologous to the one in HSA. The longer lived triplet may be assigned to the remaining indole of BSA. On the bases of wavelength dependence studies, two additional transients may be identified; the electron adduct of the disulfide bond, λ; 420 with a τ 30 ms, and the neutral indole radical,λ; 520 nm with τ ls. These results suggest that the triplet, because of its long τ, will be a valuable intrinsic reporter group for the study of the structure and dynamics of proteins in solution at room temperature.
THE REACTION CENTER OF PHOTOSYNTHETIC BACTERIA
Authors: LeslieDutton P. , Prince RogerC. , Tiede DavidM.
Published: January 2008

Abstract. Investigations on the bacterial photosynthetic reaction center have recently made several important steps forward. Progress has been made in measuring the time course of the light‐driven reactions, and in understanding the thermodynamics of these processes, in determining the chemical‐structural properties of the protein and its constituents, and in elucidating the functional relationship of the reaction center with the chromatophore membrane. Although the well‐characterized Rhodopseudomonas sphaeroides reaction center has been the main exploratory vehicle in many of these studies, we now have an ever increasing body of information from bacteria of other species and genera. This work is providing information from which we can underline features that are common to bacterial reaction centers, but it also reveals differences which may reflect different selection pressures on the separate species.

In this report we shall describe the early photochemical events of the reaction center, summarize the comparative biology of the reaction center, and discuss some of the current physical‐chemical problems pertaining to the redox components of the reaction center.
PHOTOCHEMICAL AND FREE RADICAL INITIATED REACTIONS OF1,3‐DIMETHYLTHYMINE WITH ISOPROPANOL
Authors: Shetlar Martin D.
Published: January 2008

Abstract— A photochemically induced reaction of1,3‐dimethylthymine (DMT) with isopropanol leads to the formation of four alcohol adducts. The products have been identified as the cis and trans isomers of5,6‐dihydro‐1,3‐dimethyll‐6‐(2‐hydroxy‐2‐propyl) thymine (I and II), 2.4‐diaza‐8‐hydroxy‐2.4,6.8‐tetramethylbicyclo[4.2.0]octan‐1,3‐dione (III), and5,6‐dihydro‐1,3‐dimethyl‐6‐(2‐oxo‐l‐propyl)‐thymine (IV). An acetone photosensitized reaction of DMT with isopropanol gives the same products in a similar relative yield distribution. In both of these reactions, cyclobutane dimers of DMT are produced as well. Free radical reactions of 2‐hydroxyisopropyl radicals with DMT, initiated by decomposition of di‐t‐butyl peroxide, leads to formation of only one of the cis and trans isomers described above. along with1,3‐dimethyl‐5‐(2‐hydroxy‐2‐methyl‐1‐propyl)uracil (V).
TEMPERATURE DEPENDENCE OF THE PHOSPHORESCENCE LIFETIMES OF HETEROGENEOUS TRYPTOPHAN RESIDUES IN GLOBULAR PROTEINS BETWEEN 293 AND 77 K
Authors: Kai Yoshiyuki , Imakubo Keiichi
Published: January 2008

Abstract— The phosphorescence of five globular proteins containing tryptophan residues was observed in deoxygenated neutral ethylene glycol‐phosphate buffer (1:1 by volume) at 293 and 77 K. Their spectral features at 293 K are closely identical to those at 77 K apart from a lack of tyrosine phosphorescence at 293 K. and are independent of the excitation wavelength between 250 and 310 nm. From the present results. it can be concluded that the buried tryptophan residues are the only phosphorescing centers at room temperature. Their phosphorescence lifetimes were measured as a function of temperature in the range from 77 to 293 K. At room temperature, their phosphorescence lifetimes are between about 1 and 500 ms. On the basis of their temperature dependence, the heterogeneous tryptophan environments are discussed in terms of a temperature‐activated nonradiative rate. We suggest that the observation of the phosphorescence characteristics of globular proteins containing tryptophan residues buried in the interior of the protein molecule at room temperature is likely to prove useful in probing the protein structure in solution.
THE TRIPLET EXCITED STATES OF BILIVERDIN AND BILIVERDIN DIMETHYL ESTER
Authors: Land E. J.
Published: January 2008

Abstract— The triplet states of biliverdin and biliverdin dimethyl ester have been generated using pulse radiolysis excitation. Biliverdin triplet was formed by energy transfer from biphenyl triplet in acetone, absorbed throughout the wavelength range studied (380–1000 nm) and had a half‐life of 11.7μs under the cpnditions chosen. Biliverdin dimethyl ester triplet was formed by energy transfer from biphenyl triplet in benzene, likewise absorbed throughout the wavelength range studied (360–1000 nm) and had a half‐life of 6.7μs under the conditions used. Both biliverdin and biliverdin dimethyl ester efficiently quench anthracene, naphthacene, but not μ‐carotene, triplet states. On the other hand. neither μ‐carotene nor oxygen were found to quench the triplet states of biliverdin or biliverdin dimethyl ester. Estimates or limits for the rate constants of all these quenching reactions were obtained. These reactivities suggest that the triplet levels of both biliverdin and biliverdin dimethyl ester lie around 90 kJ mol‐1. The triplet energy transfer rate from bilirubin to biliverdin dimethyl ester in benzene was measured to be 1.9 × 109 M‐1 s‐1. The singlet‐triplet intersystem crossing efficiencies of both molecules were very low, limits of 0.004 and 0.001 being found for biliverdin and biliverdin dimethyl ester, respectively, using 347 nm laser excitation.
EFFECTS OF INDOLE AND TRYPTOPHAN ON FURAN OXIDATION BY SINGLET OXYGEN IN MICELLAR SOLUTIONS
Authors: Miyoshi Norio , Tomita Giiti
Published: January 2008

Abstract— The 1,3‐diphenylisobenzofuran oxidation by singlet oxygen was investigated in aqueous dode‐cyltrimethylammonium chloride micellar solutions using pyrene as photosensitizer. It was found that indole and tryptophan markedly enhanced the furan oxidation in micellar solutions. This enhancement effect strongly depended on the ethanol content in micellar solutions; enhancement effect below about 0.3 mol fraction of ethanol and inhibition effect above this mole fraction. In the former ethanol range, a quenching of pyrene fluorescence by indole or tryptophan and a difference spectrum of furan between micellar solutions in the presence and absence of indole or tryptophan appeared strongly, but they were weakened in the latter ethanol range. The interactions between indole or tryptophan and pyrene and/or furan might be responsible for the enhancement effect observed. Discussion was made in connection with the micelle structure.
A POSSIBLE MECHANISM FOR THE ROLE OF N‐RETINYLIDENE PHOSPHATIDYL ETHANOLAMINE IN THE REGENERATION OF RHODOPSIN
Authors: Rabinovitch B.
Published: January 2008

Abstract— A series of molecular orbital calculations on a model Schiff base comparable to protonated N‐retinylidene phosphatidyl ethanolamine isomers has been made. The effect of the charged oxygen atoms of the phosphate moiety on the distribution of positive charge along the polyene chain of these isomers has been calculated. The stabilizing coulombic energy of interaction of these opposite charges and the possibility of free rotation around carbonxarbon double bonds in the electronically excited state has led to the conclusion that an 11‐cis Schiff base isomer is the most probable product of the photoisomerization of an all‐trans Schiff base.

The formation of a stable unprotonated all‐trans Schiff base in aqueous detergent dispersion and its subsequent conversion to the protonated form, both with absorption spectra in conformity with the literature, is demonstrated.
POWER‐ AND TIME‐RESOLVED RESONANCE RAMAN STUDIES AND CONFORMATIONAL CHANGES IN BACTERIORHODOPSIN
Authors: El‐Sayed M. A. , Terner James
Published: January 2008

Abstract— By comparing the resonance Raman spectra of the retinal of the intermediates of bacteriorho‐dopsin (obtained by using fixed flow with residence of time of 10 ps. variable laser power and frequency as well as computer subtraction techniques) with those of model compounds and with each other, the following possible conclusions can be obtained: (1) There exists stronger interaction between the retinal and the opsin in bacteriorhodopsin than that present in rhodopsin. (2) Conformational changes seem to take place during the dark light adaptation process as well as during the photosynthetic cycle. (3) The appearance of the spectrum of the retinal in the fingerprint region for the bL550 and bM412 intermediates is similar despite large shifts in their optical absorption maxima. This might argue against the theory that proposes ground state retinal conformational changes to explain the observed red shift in the optical spectra of retinal upon combining with the opsin. (4) Contrary to bM412, the bL550 species seems to be protonated. The fact that loss of proton does not seem to change the retinal conformation greatly might suggest that the protein and its ionic environment might carry the larger share of the load in the deprotonation process.
CHEMILUMINESCENCE FROM EUKARYOTIC AND PROKARYOTIC CELLS: REDUCING POTENTIAL AND OXYGEN REQUIREMENTS*
Authors: Allen Robert C.
Published: January 2008

Abstract— The postphagocytic microbicidal activity of polymorphonuclear leukocytes (PMNL), the effector phagocytes of the acute inflammatory response, is metabolically characterized by increased glucose oxidation via the hexose monophosphate shunt and by increased non‐mitochondrial oxygen consumption. These metabolic alterations result from the phagocytic activation of a membrane‐associated NADPH:O, oxidoreductase. The products of univalent reduction of O2 by this enzyme, O‐2 and H +, may further react to yield potential microbicidal oxidants such as H2O2, OC1‐‐, OH, and 1AgO2. The microbicidal activity of PMNL is associated with the generation of luminescence. This chemiluminescence correlates with the metabolic generation of reducing potential and O2 consumption, and is proposed to originate from the relaxation of the electronically excited products of microbicidal oxidation. The importance of O2 in microbicidal metabolism will be considered, and data demonstrating the O2‐dependence of PMNL‐chemiluminescence are presented. The phenomenon of chemiluminescence from non‐bioluminescent bacteria is also described, and preliminary data from luminescence studies of Streptococcus faecalis are presented. The relationship of light emission to bacterial metabolism and O2 toxicity is considered. Evidence for the bacterial generation of O‐2 is presented, and the role of O‐2 and H2O2 in oxidative reactions productive of electronic excited molecular products is discussed.
PSORALEN PLUS ULTRAVIOLET RADIATION‐INDUCED INHIBITION OF DNA SYNTHESIS AND VIABILITY IN HUMAN LYMPHOID CELLS IN VITRO*
Authors: Kraemer Kenneth H. , Waters Haywood L. , Ellingson Owen L. , Tarone Robert E.
Published: January 2008

Abstract— 8‐Methoxypsoralen (8‐MOP) plus high intensity long wavelength ultraviolet radiation (UV‐A) is presently being used to induce remissions of psoriasis and mycosis fungoides. Previous studies demonstrated inhibition of DNA synthesis in circulating leukocytes from some patients during this therapy. The present study is designed to determine whether conditions of 8‐MOP concentration and UV‐A exposure attained during therapy might be sufficient to result directly in decreased lymphoid cell DNA synthesis and viability in vitro. Tritiated thymidine (3HTdR) incorporation and cell growth in suspension culture following UV‐A exposure alone or with therapeutic concentrations of 8‐MOP was examined in peripheral blood lymphocytes and in Ebstein‐Barr virus transformed human lymphoblas‐toid cell lines. UV‐A exposure alone induced a dose‐dependent inhibition of HTdR incorporation in both types of lymphoid cells (3000 J/m2 resulted in 77% of control 3HTdR incorporation). Pre‐incubation with 0.1 μg/m/ 8‐MOP before UV‐A exposure induced a significantly greater inhibition of 3HTdR incorporation (3000 J/m2 resulted in 61% of control 3HTdR incorporation). Greater inhibition of 3HTdR incorporation was observed by preincubation of the lymphoblastoid cells with 1.0μg/mC 8‐MOP (3000 J/m2 resulted in 41% of control) but not in the lymphocytes (3000 J/m2 resulted in 63% of control). The concentration of viable lymphoblastoid cells did not decrease below the original concentration after the highest dose of UV‐A alone (29,000 J/m2) but preincubation with 0.1 μg/mC 8‐MOP resulted in 40% survival after 3000 J/m2 (D37 approximately 3000 J/m2) and preincubation with 1.0 μg/ 8‐MOP resulted in 0.6% survival after 3000 J/,2 (D37 approximately 800 J/m2). This study suggests that the low doses of 8‐MOP and UV‐A received by patients' lymphocytes may be sufficient to explain the decreased DNA synthesis found in their circulating leucocytes. The long term consequences of such damage remain to be determined.
ON THE OPTICAL SPECTRA OF SOLID FILMS OF RETINYL POLYENES. ISOMERIZATION DURING THE AUTOXIDATION?
Authors: Finkelshtein E. I. , Kozlov E. I.
Published: January 2008

Abstract— The UV spectra of solid amorphous films of all‐trans retinyl polyenes. i. e. retinyl acetate, retinyl palmitate, axerophtene and retinal, on supports are investigated. It is shown that in the absence of oxygen the spectra of the films do not change at room temperature; in the presence of O2 the fast oxidation of the polyenes occurs which in the case of retinol esters and axerophtene is accompanied by the shift of the absorption maxima to the shorter wavelengths. Consequently, the interpretation of blue shift of UV spectra of retinyl polyene films given by Hotchandani and Leblanc (1976) is incorrect. The formation of the only compound is shown to occur during the first stage of the oxidation of retinyl acetate and retinyl palmitate films. Proceeding from IR spectra of oxidized films the compound is assigned to the corresponding 11‐cis isomer.
SURVIVAL, SPORE FORMATION AND EXCISION REPAIR OF UV‐IRRADIATED DEVELOPING CELLS OF DICTYOSTELIUM DISCOIDEUM NC‐4
Authors: Ford W. T. , Deering R. A.
Published: January 2008

Abstract— The synchronously developing aggregates of the cellular slime mold, Dictyostelium discoideum NC‐4, were disaggregated into individual cells and irradiated with 254 nm UV light at preaggregation (0h), late interphase (6h), late aggregation (12 h), and preculmination (18 h). When assayed for replica‐tive ability (colony formation), the developing cells at 0, 6, 12, and 18h showed the same sensitivity as vegetative cells; the 10% survival dose (D10) was 160 J/m2. The spores were more sensitive, with D10 of 70 J/m2. Excision repair of the nuclear DNA of the developing cells was studied by alkaline sucrose gradients. UV‐induced single‐strand breakage and rejoining of the DNA occurred to the same final extent in the cells from the 0, 6, 12 and 18 h stages of development, but a longer time was required for the completion of rejoining at the later stages (for example, at 54 J/m2, 6.6 h for preculmination cells, 3.3 h for preaggregation cells). When the cells irradiated at various stages were required to redevelop, as measured by the relative numbers of spores produced, their sensitivity for completing this development increased the later the stage from which they were taken. The D10s for spore production were 200, 130, 100 and 70 J/m2 for cells at the 0, 6, 12 and 18 h stages, respectively. The fractional viability among the spores that appeared after this treatment was the same independent of the stage at which the cells were irradiated; the D10 for this viability was 160 J/m2, the same as if the cells had been plated immediately with no intervening developmental sequence. We conclude that DNA excision repair as related to replicative ability is retained at all stages of development; however, development seems independent of replicative ability and depends upon DNA and/or non‐DNA damage in a more complex way.
FLASH PHOTOLYTIC INVESTIGATIONS OF THE ELECTRON TRANSFER BETWEEN AROMATIC HYDROCARBON RADICALS AND TRYPTOPHAN IN MICELLAR SOLUTIONS
Authors: Putna Libor , Reske Günter , Schmidt Hartmuti
Published: January 2008

Abstract— Electron transfer reactions between tryptophan and cation radicals of various polycyclic hydrocarbons which are known to differ with respect to their carcinogenic and photodynamic activity have been investigated by flash spectroscopy. The hydrocarbons were solubilized in sodium dodecyl sulfate micelles. Their cation radicals were produced by photoionization probably via the excited singlet states. In the case of benz[a]anthracene, benzo[ghi]perylene, pyrene, benzo[rst]pentaphene, dibenz[a, h]‐anthracene and anthracene, the electron transfer takes place in the Stern layer of the micelles and leads to neutral tryptophan radicals. It is assumed that tryptophan forms charge transfer complexes with the cation radicals of 3‐methylcholanthrene and 7,12‐dimethylbenz[a]anthracene. With perylene tryptophan only reduces the radical yield. New species could not be detected in this case. No correlation exists between the carcinogenic or the photodynamic activity of the hydrocarbons and the electron transfer behaviour of their cation radicals.
PHOTOCHEMICAL DECOMPOSITION OF 1, 4‐BENZODIAZEPINES. NITRAZEPAM*
Authors: Cornelissen P. J. G. , van Henegouwen G. M. J. Beijersbergen
Published: January 2008

Abstract— The photochemical activity of nitrazepam, a drug of which phototoxic effects are known, is investigated. Nitrazepam decomposes photochemically in an oxygen‐poor medium, while it is relatively stable in the presence of oxygen. It appears that this quenching of excited nitrazepam by molecular oxygen leads to the formation of singlet oxygen. This is demonstrated in three different ways:

1. In the presence of 2‐methyl‐2‐pentene as acceptor of singlet oxygen, two characteristic products are formed: 2‐methyl‐1‐penten‐3‐ol and 2‐methyl‐3‐penten‐2‐ol.

2. The photosensitized oxidation of L‐dopa in the presence of nitrazepam is increased when D2O, instead of H2O, is added to the solvent system, due to the longer lifetime of singlet oxygen in D2O.

3. The β‐value, the ratio of the rate of decay of singlet oxygen to its rate of reaction, is determined with L‐dopa as acceptor of singlet oxygen. The same value is obtained with both nitrazepam and methylene blue, a known singlet oxygen generator.
LIGHT‐REGULATED PERMEABILITY OF RHODOPSIN‐PHOSPHOLIPID MEMBRANE VESICLES*
Authors: O'Brien D. F.
Published: January 2008

Abstract—Light absorption by rhodopsin in receptor cell membranes initiates the excitation of the receptor cell. Rhodopsin‐phospholipid membrane vesicles were studied to localize initial transduction events. Rhodopsin‐phospholipid recombinant membranes are thermally stable and light sensitive and may be chemically regenerated after bleaching in the same manner as receptor cell membranes. Rhodopsin‐containing vesicles prepared from unsaturated phosphatidylcholine (PCho) or PCho and phosphatidylethanolaminc display kinetics for the metarhodopsin I to II transition which are comparable to those of receptor cell membranes. NMR spectroscopy was used to examine the permeability of the membrane vesicles to added shift (Eu3+) or relaxation reagents (Mn2+, Co2+). Unexposed rhodopsin‐phospholipid vesicles are sealed to ion movement and become permeable after light exposure. Selected ions (Ca2+, Mn2+, Co2+) may be photoreleased from the interior of loaded membrane vesicles. The quantity released is proportional to the initial ionic concentration. The number of ions released/rhodopsin bleached is dependent on the light intensity, and high yields (40–160) of Ca2+/rhodopsin bleached are observed at low levels of light bleaching. The present results indicate that rhodopsin spans the phospholipid bilayer membrane, and are consistent with an increase in the permeability of the membrane initiated by light excitation of rhodopsin.
7‐cis‐PORPHYROPSIN FROM 7‐cis‐3‐DEHYDRORETINAL AND CATTLE OPSIN*
Authors: Matsumoto Hiroyuki , Asato Alfred E. , Liu Robert S. H.
Published: January 2008

Abstract 7‐cis‐3‐Dehydroretinol, prepared by photoisomerization of the all‐trans isomer in a polar solvent, was found to combine with cattle opsin to form a visual pigment analogue with an absorption maximum at 464 nm. The pigment is only moderately stable in hydroxylamine or in Ammonyx LO. and cannot be purified by column chromatography using Ammonyx LO. 9‐cis‐Porphyropsin, prepared in a manner similar to that reported by Azuma et al., is stable and has been purified by passing through a hydroxylapatite column. Three fractions were collected with eluant of increasing ionic strength. All fractions exhibit similar absorption properties with Λmax at 498 nm. These results further indicate that the binding of opsin is a flexible one.
THE ACTION SPECTRA OF FREE RADICALS PRODUCED BY THE IRRADIATION OF KERATIN CONTAINING BOUND IRON(III) IONS
Authors: Smith Gerald J. , Claridge Rodney F. C. , Smith Carolyn J.
Published: January 2008

Abstract—The action spectra have been determined for two free radical species produced by irradiating wool protein containing bound iron(III) ions with light between 330 and 540 nm. The faster growing free radical displays an action spectrum with a peak at 405–415 nm. It is suggested that an iron (III) ion‐sulphur complex is the chromophore responsible for the formation of this carbon type radical.
NEW SPECTRAL COMPONENTS IN HIGH RESOLUTION ABSORPTION SPECTRA OF GREEN BACTERIAL REACTION CENTER COMPLEXES AT 5K*
Authors: Whitten William B. , Pearlestein Robert M. , Olson John M.
Published: January 2008

Abstract—absorption spcctra of reaction center Complexes I and II from Chlorobium limicola f. thiosul‐fatophilum were taken from 760 and 860 nm at 5 K. Fourth and eighth derivatives of the spectra were calculated from the digital data. Light‐minus‐dark difference spectra were taken, also at 5 K, with 590 nm actinic light. A shoulder not visible at 77 K appears on the long wavelength side of the 834 nm peak in Complex I. In Complex II, which is derived by guanidine HCI treatment of I, the shoulder is much more pronounced; derivative peaks appear at 834 and 838 nm. In the difference spectra, there are troughs at 832 and 838 nm. The latter trough is the first instance in green bacteria of a wavelength coincidence between a light‐induced bleaching and a peak in (derivative) absorbance. There is also a nearly symmetrical pair of features, a trough at 814 nm and a peak at 818 nm, that appear to represent a light‐induced bathochromic shift of the absorbance at 816 nm, a peak which occurs in both complexes as well as the photochemically inert bacteriochlorophyll a (Bchl a) protein. Other features in the absorption spcctra of both Complexes occur at virtually the same wavelengths as the peaks in purified Bchl a‐protein trimer. We conclude that a large fraction of the Bchl a in Complex II is in a conformation similar to that of a single subunit of Bchl a‐protein.
FLAVIN COMPOUNDS AS AGENTS FOR THE OXIDATION OF PLASTOCYANIN IN BLUE LIGHT
Authors: O'Kelley Joseph C. , Hardman John K.
Published: January 2008

Abstract—Flavins, flavin nucleotides and selected flavoproteins have been compared in a reaction using blue light. in which plastocyanin is oxidized as the flavin is photoreduced. Per unit of light absorbed. flavin mononucleotide is more effective than flavin adenine dinucleotide, ribotlavin or lumiflavin. Of the flavoproteins tested, diaphorase from Clostridium kluyveri was most effective, but was less active than free flavin mononucleotide. The oxidation of plastocyanin requires aerobic conditions. and appears to be mediated by the production of singlet oxygen when the flavin is irradiated.
THE USE OF BENZOPHENONE AS A PHOTOAFFINITY LABEL, LABELING IN p‐BENZOYLPHENYLACETYL CHYMOTRYPSIN AT UNIT EFFICIENCY
Authors: Campbell Peter , Gioannini Theresa L.
Published: January 2008

Abstract—p‐Benzoylphenylacetyl chymotrypsin, an acyl enzyme derivative containing the benzophenone group in the hydrophobic binding pocket, was prepared and is indefinitely stable at low pH. Photolysis of this covalent derivative leads to loss of enzymic activity and incorporation of the labeling group via formation of a second covalent bond. The efficiency of the photochemical processes is exceptionally high, producing 100% incorporation and at least 92% inactivation. Analysis of active site titration data for the photolyzed enzyme show that at least two different photochemical processes must be involved. Elimination of phosphorescence emission and reduction of UV absorption upon photolysis are consistent with initial hydrogen abstraction by benzophenone triplet state, followed by radical coupling, much as has been observed for the photoreaction of benzophenone with model systems. Photoaffinity labeling of chymotrypsin is also efficiently accomplished using two benzophenone derivatives which bind noncovalently to the enzyme's active site, although the rates of labeling are somewhat less than in the covalent complex.
VISUAL PIGMENTS—10. SPECTROSCOPY AND PHOTOPHYSICAL DYNAMICS OF RETINOL AND RETINYL ETHER
Authors: Chihara Kohji , Takemura Takeshi , Yamaoka Tsuguo , Yamamoto N. , Schaffer Arnold , Becker Ralph S.
Published: January 2008

Abstract— The absorption and emission spectra, lifetimes and quantum yields of all‐trans retinol have been examined as a function of solvent and temperature. In addition, the spectroscopy of retinyl ether and 2 other polyene alcohols have been determined. Based on the results obtained, we conclude that the singlet excited state of retinol and retinyl cther is of a forbidden character and of the type loosely called 1A‐g. Retinol forms a dimer in an alkane solvent when cooling from 298 to 77 K. A general structure for the dimer is proposed.
BIPHASIC PHOTOCHEMISTRY: PHOTOCHEMICAL REGIOSPECIFICITY AND CRITICAL MICELLE CONCENTRATION DETERMINATION
Authors: Lee K. H. , Mayo P. de
Published: January 2008

Abstract— The irradiation of 3‐n‐butylcyclopentenone has been shown to give cyclobutane dimers, the ratio of head‐to‐head and head‐to‐tail isomers being solvent dependent. It is now shown that in aqueous medium this ratio is dependent on surfactant concentration both for charged and uncharged species. A very abrupt change in regiospecificity occurs at the critical micelle concentration, and c.m.c. values are obtained in which there is no ambiguity from extrapolation and which are in excellent agreement with values in the literature. This technique represents a new method for c.m.c. determination.
STERIC HINDRANCE IN PROPOSED PHOTOISOMERS OF BILIRUBIN
Authors: Geddes A. J. , Potterton Elizabeth , Willis G.
Published: January 2008

Abstract— Semi‐empirical potential energy calculations have been used to examine the stabilities of the proposed geometric isomers of bilirubin. The calculations show that for either of the dipyrrole moieties, the ‘anti‐E’ and ‘syn‐E’ planar conformations are sterically unacceptable. The most stable form of the E isomer has the two pyrrole rings almost at right angles and in this conformation there can be no π‐delocalisation between the rings.
INHIBITION OF UV AND PSORALEN‐PLUS‐LIGHT MUTAGENESIS IN PHAGE T4 BY GENE 43 ANTIMUTATOR POLYMERASE ALLELES
Authors: Yarosh, Daniel B. , Johns Virginia , Mufti Siraj , Bernstein Carol , Bernstein Harris
Published: January 2008

Abstract— Mutagenesis by UV light or psoralen‐plus‐light was measured by increases in the reversion of nonsense mutants of phage T4. In the presence of either of two gene 43 antimutator polymerase alleles, tsCB120 or tsCB87, UV‐induced reversion was inhibited. Likewise psoralen‐plus‐light mutagenesis was inhibited when the tsCB120 allele was present. These results imply that the gene 43 DNA polymerase has a role in the formation of mutations from the DNA lesions induced by UV and psoralen‐plus‐light.
SOLVENT‐INDUCED ENHANCEMENT OF WEAKLY ALLOWED VIBRONIC TRANSITIONS OF AROMATIC HYDROCARBONS
Authors: Mukhopadhyay A. K. , Georghiou S.
Published: January 2008

Abstract— The enhancement of weakly allowed vibronic bands in the fluorescence and absorption spectra of 1,12‐benzoperylene, 1,2,3,4‐dibenzanthracene, naphthalene and 1‐methylnaphthalene has been observed in polar solvents at room temperature. No satisfactory correlation has been found between the extent of solvent effect and the solvent dielectric constant, dipole moment or the Kosower's Z‐value. It is proposed that, as we previously found for pyrene, the enhancement is the result of complex formation between the hydrocarbons and the polar solvents which reduces the molecular symmetry and gives, in turn, rise to the intensification of weakly allowed vibronic transitions. The finding that the 2‐methyl, 1,3‐dimethyl and 1,6‐dimethyl derivatives of naphthalene, which have in inert solvents more strongly allowed transitions than naphthalene, do not show the solvent effect to any appreciable extent is consistent with this interpretation.
ENHANCEMENT OF THE FAR‐UV LETHALITY IN YEAST CANDIDA GUILLIERMONDII BY NEAR‐UV POST‐IRRADIATION
Authors: Fraikin G. Y. , Pospelov M. E. , Rubin Leonid B.
Published: January 2008

Abstract— In experiments with the non‐photoreactivable yeast Candida guilliermondii, radiations at 313, 334 and 365 nm, having no effect on untreated cell populations, produced an ‘enhancing’ effect on the lethality of 254 nm‐pretreated cells. Wavelengths in the visible region of the spectrum did not exhibit a similar effect.