bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURE‐REACTIVITY RELATIONSHIPS IN REDOX‐PHOTOSENSITIZED SPLITTING OF PYRIMIDINE DIMERS AND UNUSUAL ENHANCING EFFECT OF MOLECULAR OXYGEN *
Authors: Pac Chyongjin , Kubo Junichi , Majima Tetsuro , Sakurai Hiroshi
Published: January 2008

Abstract Redox photosensitization using the phenanthrene‐p‐dicyanobenzene pair in acetonitrile has been applied to the respective four isomeric dimers of N.N′‐dimethylthymine (DMT) and N,N′‐dimethyluracil (DMU) as well as to several related cyclobutane compounds. The head‐to‐head (syn) dimers of both DMT and DMU can undergo photosensitized splitting in the following order of efficiency: cis, syn dimer of DMT > cis, syn dimer of DMU > trans, syn dimer of DMT. On the other hand, the head‐to‐tail (anti) dimers are totally unreactive and have higher oxidation potentials than the corresponding syn dimers. It is suggested that the key mechanistic pathway is the formation of π complexes between the dimers and the photo‐generated cation radical of phenanthrene by way of which splitting of the cyclobutane ring catalytically occurs without the formation of the discrete cation radical of the dimers. Structure‐reactivity relationships are interpreted in terms of through‐bond interactions between the n orbitals of N(l) and N(l′) involving the C(6)‐C(6′) bond, as well as in terms of steric repulsion. It was found that aeration of solution greatly enhances the quantum yields of photosensitized splitting; the limiting quantum yield for splitting of the cis, syn dimer of DMT is 100.
PHOTODYNAMIC EFFECTS INDUCED BY FUROCOUMARINS ON A MEMBRANE SYSTEM. COMPARISON WITH HEMATOPORPHYRIN
Authors: Salet C. , Moreno G. , Vinzens F.
Published: January 2008

Abstract Isolated rat liver mitochondria have been used as a model to investigate the photodynamic action of psoralen (Ps) and 4,5′,8‐trimethylpsoralen (TMP) on cellular membrane systems in comparison with hematoporphyrin (Hp). Oxidation was detected by the consumption of free oxygen as measured polarographically in the respiratory chamber when irradiated with UV light (320‐380 nm). In the presence of Ps, singlet oxygen was produced in the respiratory medium but neither the respiration nor the oxidative phosphorylation were affected. On the contrary the hydrophobic derivative TMP impaired the respiration with rapid uncoupling of oxidative phosphorylation as did Hp. The ineffectiveness of Ps as well as the effectiveness of TMP vs. Hp is explained on the basis of photophysical properties of the molecules and their partition coefficient. These results may indicate that, in the photochemiotherapy of skin diseases, furocoumarins can drive photodynamic reactions at various subcellular levels according to their hydrophobicity.
BLOCKAGE OF RESTRICTION ENDONUCLEASE CLEAVAGE BY THYMINE DIMERS
Authors: Hall Robert K. , Larcom L. L.
Published: January 2008

Viral DNAs were subjected to 254 nm irradiation and then digested with type II restriction endonucleases. At the fluences used, irradiation inhibited cleavage by nucleases which recognize sites containing neighboring thymines. Cleavage by endonucleases with other recognition sequences was not affected. In viral and plasmid DNAs, this effect could be used to study thymine dimer formation at a few specific, mapped sites of defined base sequence.
TIME‐RESOLVED FLUOROMETRY OF BACTERIORHODOPSIN
Authors: Sherman Warren V.
Published: January 2008

Abstract A mode‐locked Nd:YAG laser was used to excite the aromatic amino acid residues of bacteriorhodopsin in the purple membrane and the tryptophan (Trp) fluorescence decay analyzed with a streak camera (λ> 380 nm). The decay kinetics are resolvable into two first‐order half‐times (1.5 and 0.17 ns, respectively), while for retinylidene‐free bacterioopsin, only the longer‐lived Trp emission was observed. The shorter‐lived species reappeared upon regeneration of bacteriorhodopsin by addition of retinal to bacterioopsin but not on treatment of the latter with an equivalent of retinol. It is proposed that these results are consistent with a structural model in which the 7‐8 Trp's distributed among sections A, C, E and F of the seven helical segments A‐G of native bacteriorhodopsin are distinguishable by their distances from the chromophore. Assuming a Förster mechanism for energy transfer with Ro= 25 and 32 Å, respectively, for retinylidene chromophore and retinol the Trp's may be divided into two groups: (i) those completely quenched by retinol and partly quenched by retinal (τ= 0.17) with R ≃ 18 Å and (ii) those (τ= 1.5 ns) which are quenched neither by chromophore nor retinol with R > ca. 30 Å. These results are consistent with and support some of the best models of Engelman et al. (1980) for the protein conformation in the purple membrane.
FLUORESCENCE LIFETIMES OF CHLOROPHYLL a: SOLVENT, CONCENTRATION AND OXYGEN DEPENDENCE
Authors: Connolly John S. , Janzen A. Frederick , Samuel Edward B.
Published: January 2008

Fluorescence lifetimes (τf) of chlorophyll a (Chi a) have been measured by the single‐photon‐counting technique over a wide range of concentrations (˜10‐7˜10‐4M) in deoxygenated pyridine, diethyl ether, toluene and methanol. At pigment concentrations ˜1 μM, reabsorption of fluorescence induces significant artifacts on measured values of τf which are dependent on detection wavelength and the specific geometry of the experiment. There is a clear dependence of τf on the nature and degree of solvation, including both coordination of the central magnesium and hydrogen‐bonding of the solvent (viz. alcohols) to the macrocycle. Quenching of the excited singlet state by molecular oxygen was measured quantitatively in ether, and a bimolecular rate constant markedly slower than the diffusion‐controlled limit was obtained.
MICROSPECTROFLUOROMETRIC APPROACH TO THE STUDY OF FREE/BOUND NAD(P)H RATIO AS METABOLIC INDICATOR IN VARIOUS CELL TYPES
Authors: Salmon Jean‐Marie , Kohen Elli , VIALLET Pierre , Hirschberg Joseph G. , Wouters Alain W. , Kohen Cahide , THORELL Bo
Published: January 2008

Under excitation at 365 nm, the cell fluorescence is mainly due to bound and free NAD(P)H, plus a small contribution from flavins. Resolution is first attempted in the simplest case. i.e. the increase spectrum (δIf) due to microinjection of glucose‐6‐phosphate (G6P) into EL2 ascites cells. Above 510 nm, δIF is identical to the spectrum of free NADH. Below 510 nm. the presence of a second component is suggested, i.e. the intensity of the free NADH spectrum is lower than the measured δIF level. The difference between δIf and the free NADH spectrum (maximum at 475 nm) yields a spectrum suggestive of bound NADH with maximum at 450 nm. Thus, with free and bound NADH, the entire δIF can be reconstructed, with some assumptions as to the relative quantum yields of the two components. This seems to leave no place for a flavin component.

The questions raised by the lack of such a component are answered using a new microspectrofluorometer, which aiiows correlated monitoring of NAD(P)H and flavins with excitations at 365 and 436 nm, respectively. As detected by excitation at 436 nm, injections of G6P, malate, ADP, and treatments with azide, cyanide or partial anaerobiosis, all indeed show a redox change of flavins, in the sense of decreased emission. It is understandable, however, that such a change which is not very large even using 436 nm excitation should remain undetected when flavins are excited at 365 nm, i.e. using the tail of their excitation spectrum.

In contrast to the increased δIF spectrum recorded in response to injected substrate, the initial spectrum (If) of the cell prior to a metabolic perturbation reveals a third component, even with 365 nm excitation. The position and reactivity of this component shows flavin‐like properties. The structural resolution attainable makes it possible to obtain the evaluation of free vs. bound NAD(P)H and flavin fluorochromes in the mitochondrial and cytosolic compartments of the intact cell.
PREBIOTIC FORMATION OF HIGHER MOLECULAR WEIGHT COMPOUNDS FROM THE PHOTOLYSIS OF AQUEOUS ACETIC ACID
Authors: Mendoza Alicia Negrón , Ponnamperuma Cyril
Published: January 2008

In the study of chemical evolution, experiments simulating primitive earth conditions have shown that many compounds of biological significance can be produced from simple precursors. In an attempt to search for the origin of polycarboxylic acids, the UV irradiation of aqueous acetic acid was performed. Among the products detected were succinic, citric and malonic acids which are key compounds in metabolic pathways, suggesting that these compounds might have been formed on the primitive Earth prior to life itself.
ASSOCIATION OF CHLOROPHYLL WITH AMIDES ON PLASTICIZED POLYETHYLENE PARTICLES—I. N, N‐DIMETH YLM YRISTAMIDE*
Authors: Seely G. R. , Rutkoski A. M. , Kusumoto Y. , Senthilathipan V. , Shaw E. R.
Published: January 2008

Abstract— Model systems have been prepared in which chlorophyll a (Chl a) and N.N‐dimethylmyristamide (DMMA) are adsorbed together in various ratios to particles of polyethylene swollen with undecane. The adsorption is performed by equilibrating the particles with methanol‐water solutions of increasing water content. Absorption spectra of the coated particles in viscous suspenions show sharp well‐marked bands over much of the composition range examined. With the aid of second derivative spectra. the red absorption band has been resolved into three components. at 661.5. 674 and 680 nm. Fluoresccnce spectra have also been resolved into their principal components with some assistance from comparison with spectra of Chl in undecane solution containing DMMA. At room temperature (295 K) the resolvable components are of monomeric Chl at 670 nm. and of associated species at 681 and 725 nm. Fluorescence at 77 Kis of similar intensity but is distributed differently. in favor of longer‐wave components. Corresponding to the 295 K components are emission bands at 675, 683–5 and 735 nm. Othcr components appear under certain conditions: at 695–700 nm when the Chl and DMMA conccntrations are both high, and at 705 nm whcn the ratio of DMMA to Chl is low. If DMMA is absent or at low concentration, much of the Chl exists as an aggregated form absorbing near 741 nm and fluorescing weakly near 760 nm at 77 K. Adsorption isotherms indicate some degree of cooperativity in the binding of Chl and DMMA to the particles. The photoreduction of p‐dinitrobenzene by hvdrazobenzene. scnsitized by these particles, has been demonstrated
PICOSECOND FLUORESCENCE KINETICS IN SPINACH CHLOROPLASTS AT LOW TEMPERATURE
Authors: Reisberg Paul , Nairn John A. , Sauert Kenneth
Published: January 2008

Abstract— At 77 K the fluorescence from spinach chloroplasts excited using picosecond mode‐locked laser pulses at 620 nm is made up of 5 separate kinetic components. Three of these are predominant at short wavelengths. between 650 and 690 nm, and they appear to correspond to the 3 decay phases seen at room temperature. The 2 new components. a 100 ps rise and a 3000 ps decay, characterize the longer (730–770 nm) wavelength fluorescence. The temperature dependence of the kinetic components of the long wavelength fluorescence shows that the 3000 ps decay accounts for essentially all of the large increase in fluorescence yield observed at low temperature. Furthermore, it appears that this increase does not result entirely from an increase in the fluorescence lifetime, as has been proposed. The dependences of these 2 new components (the 100 ps rise and 3000 ps decay) on emission wavelength and temperature are similar enough to suggest they have a common origin, presumably the chlorophyll pigment component C705. The amplitudes (yield/lifetime) of these 2 phases are approximately equal, and they are opposite in sign. Thus. we see evidence of time‐resolved excitation transfer from those pigment molecules that absorb the 620 nm radiation to those that give rise to the long wavelength fluorescence at low temperature.
THE USE OF DIFFUSERS IN THE MEASUREMENT OF TRANSMISSION OF HUMAN EPIDERMAL LAYERS
Authors: Bruls Wel A. G. , van der Leun Jan C.
Published: January 2008

Abstract— The transmission of the outermost layers of human skin is measured, by use of a diffuser. The sample is transferred to the diffuser and inserted into the measuring beam. The reference beam is also measured after passing through the diffuser. The diffuser transforms the light in both the sample and reference beams into a completely diffuse flux. The radiant flux of light emerging from the diffuser is directly proportional to the radiant flux of the light impinging on the diffuser, but does not depend on the angular distribution of the impinging light. Because of this particular property, a diffuser may be used to measure the transmission of scattering specimens. The analogy between a diffuser and an integrating sphere is pointed out.

Deviations of commercially available diffusers from the perfect behaviour lead to deviations in the measured transmissions that are negligible (< 3%) for epidermal and corneal samples. Spectral transmission data from representative skin samples are presented. It is found that correction for fluorescence is necessary. Due to this correction the epidermal UV‐C transmission is lower by a factor of 10–100 than without correction, and the epidermal absorption maximum is shifted from 275 towards 265 nm.
A FLASH PHOTOLYSIS STUDY OF 1‐METHYLINDOLE
Authors: Pepmiller Craig , Bedwell Eleanor , Kuntz Rlobert R. , Ghiron Camillo A.
Published: January 2008

Abstract— The conventional flash photolysis of 1‐methylindole in aqueous media was studied at Λexcitation≥290 nm. The transients observed 20 μs after excitation consisted mainly of the radical cation (R+). the hydrated electron (e‐aq) and the triplet state (T). Electron counting experiments indicate that photoionization is the only source of R+ with e‐aq/R+= 1.07±0.09 in neutral media. Quenching of the R+ yield with H+ indicates that the fluorescent state is the precursor to 80% of the photoionization events with the remainder probably arising from a prefluorescent state. The triplet decays with a lifetime of 29 μs in deaerated neutral media. This decay is unchanged by N2O saturation, but T reacts with acrylamide with k≥2.8 × 109M‐1. In 2 M Br‐, R+ and T yields are increased by factors of 2–3. Consideration of fluorescence quenching and T enhancement by Br‐permits an estimate of φIsc between 0.33 and 0.49. The increased R+yield at high Br‐concentrations cannot be accounted for by induced photoionization or triplet state reactions.
FOLLOW UP ON SYSTEMIC INFLUENCE OF PARTIAL PRE‐IRRADIATION ON UV‐TUMORIGENESIS
Authors: Gruijl Frank R. De , Leun Jan C. Van Der
Published: January 2008

Abstract— In a previous paper we presented experimental data which showed that partial pre‐irradiation of a mouse enhanced subsequent UV‐tumorigenesis in formerly unexposed skin areas: a systemic effect. In those experiments pre‐irradiation was carried out up to the point where tumors started to appear in the pre‐irradiated skin areas. Here we present the results of an experiment in which pre‐irradiation was discontinued long before the appearance of tumors. The systemic effect induced by the pre‐irradiation remained detectable, though‐it was weaker than in the previous experiment. It is suspected that the observed systemic effect affects the initiation of tumors rather than the growth. A discussion is presented on how changes in initiation may best be detected, which may also prove to be useful for the design of other comparative studies on UV‐tumorigenesis.
SUBSTITUTION OF RETINAL BY ANALOGUES IN RETINAL PIGMENTS OFHALOBACTERIUM HALOBIUM.CONTRIBUTION OF BACTERIORHODOPSIN AND HALORHODOPSIN TO PHOTOSENSORY ACTIVITY
Authors: Schimz A. , Sperling W. , Ermann P. , Bestmann H. J. , Hildebrand E.
Published: January 2008

Abstract—InHalobacrerium hnlobium.retinal is the chromophore of the light‐energy converting pigments bacteriorhodopsin (BR) and halorhodopsin (HR) and of the sensory photosystems. PS 370 and PS 565. In both photosystems as well as in BR and HR. retinal was substituted by retinal analogues.Retinal2(3,4‐dehydro‐retinal).shifts the main sensitivity maximum of PS 370 and of PS 565 by about 1.5 nm to longer wavelengths. The absorption maxima of BR and HR are both shifted in the same direction, but by 37 nm.13‐Ethylretinaland13‐propylretirnalshift the main sensitivity maximum of each sensory photosystem to shorter wavclengths; the absorption maxima of BR and HR are shifted in the same direction but to a smaller extent. Both sensory photosystems are equally active with retinal and with each of the three analogues as the chromophore. After substitution of retinal by the analogues, the action spectra of PS 565 of the BR‐containing strain R1L3show a secondary bensitivity peak in addition to the main peak. This secondary peak matches the absorption maximum of the corresponding BR. In the action spectra of the BR‐deficient strainET–15 this secondary peak is missing. Action spectra of PS 565 of the BR‐deficient strainL–33, which synthesizes increased amounts of HR. with all retinals show a secondary peak which matches the absorption maximum of the corresponding HR.

The results show that the analogues can substitute retinal in both sensory pigments as well as in BR and HR. Moreover, the data support the previous assumption that both BRand HR, although not required for photosensory activity can contribute to photosensing through PS 565.
PHYTOCHROME‐MEDIATED PHOTOTROPISM IN PROTONEMATA OF THE MOSS Ceratodon purpureus BRID
Authors: Hartmann Elmar , Klingenberg Bernd , Bauer Leopold
Published: January 2008

Abstract— Protonemata of the moss Ceratodon purpureus cultured in white light were transferred to darkness for 3 days and then used for phototropic experiments. Irradiation of the apical region of vertically position protonemata with small beams (0.2 mm) of red light induced a growth response towards the irradiated side (positive phototropism). The phototropic response showed irradiance dependence. The effect of red light was completely reversed by far‐red light following red light irradiations, demonstrating that phytochrome was the photoreceptor pigment. Far‐red light or UV‐blue light had no influence on either bulging or phototropism. Experiments with linearly polarized red or far‐red light showed a different dichroic distribution of phytochrome in its different forms, the red‐absorbing form, Pr and the far‐red‐absorbing form, Pfr. Red light with a vibration plane parallel to the long axis of the filaments was most effective. The effectiveness of far‐red light was expressed best when its vibration plane was 90° to the electrical vector of the inductive red light.
COMPLEX FORMATION BETWEEN ETHIDIUM BROMIDE AND THE NUCLEOTIDES AMP AND GMP
Authors: Maniooth D. , Georghiou S.
Published: January 2008

Abstract— The antimicrobial drug ethidium bromide (EB) has been found to form molecular complexes with nucleotides, the strongest being those with the purines AMP and GMP. For the EB‐AMP and EB‐GMP complexes (which we characterized) the values of the ground‐state association constant have been found to be 100 and 103 M‐1, respectively. The fluorescence of the drug is enhanced when complexed to AMP, GMP, and TMP by about 60, 30 and 10%, respectively, whereas it is quenched by about 20% when complexed to CMP. Fluorescence enhancement analysis has yielded the values of 1.1 × 1010 and 0.7 × 1010M‐1 s‐1 for the excited‐state rate constant of complex formation with the former two nucleotides, respectively. About one out of two collisions between an excited EB molecule and an AMP or GMP molecule results in complex formation. The potential implications of these findings for the EB‐DNA interaction are discussed.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—VI. IDENTIFICATION OF THE FREE RADICALS GENERATED DURING THE PHOTOLYSIS OF MUSK AMBRETTE, MUSK XYLENE AND MUSK KETONE
Authors: Motten Ann G. , Chignell Colin F. , Mason Ronald P.
Published: January 2008

Abstract—

Musk ambrette (4‐tert‐butyl‐3‐methoxy‐2,5‐dinitrotoluene), a common component of perfumes, soaps, and some food flavorings, can cause cutaneous photosensitization reactions including photoallergy. These may be mediated through free radicals formed during photolysis. When musk ambrette was photolyzed under nitrogen in basic methanol, two distinct nitro anion radicals were identified by electron spin resonance. One radical was centered on a nitro group in the plane of the aromatic ring, while the other was centered on a nitro group twisted out of the plane of the ring due to steric hindrance by bulky substituents on either side of the group: the two radicals appeared to interconvert and maintain an equilibrium concentration ratio. Two closely related compounds which are also used in perfumes, but have not been reported to cause photosensitizing reactions, also produced free radicals during photolysis. Musk xylene (2,4,6‐trinitro‐1,3‐dimethyl‐5‐tert‐butylbenzene) generated two nitro anion radicals, both of which were centered on twisted nitro groups, while musk ketone (3,5‐dinitro‐2,6‐dimethyl‐4‐tert‐butylacetophenone) produced only one nitro anion radical, which is also twisted. Athough these nitro anion radicals are probably the first step in the photolysis of these nitroarornatic molecules, it seems likely that in vivo they will undergo further reduction to produce more reactive species including the corresponding nitroso and hydroxylamine derivatives. In addition, autoxidation of the nitro anion radical intermediate forms superoxide.
DETERMINATION OF THE BINDING CONSTANT OF H14 CO−3 TO THE PHOTOSYSTEM II COMPLEX IN MAIZE CHLOROPLASTS: EFFECTS OF INHIBITORS AND LIGHT
Authors: Stemler Alan , Murphy Judith
Published: January 2008

Abstract—

The binding (dissociation) constant for HCO−3 to the photosystem II complex in maize chloroplasts is approximately 80 μM. One HCO−3 binds per 500–600 chlorophyll molecules. In the dark, formate is a competitive inhibitor of HCO−3 binding, while 3‐(3′,4′‐dichlorophenyl)‐1, 1‐dimethylurea (DCMU) inhibits HCO−3 binding non‐competitively. Light decreases HCO−3 binding in the presence of formate. Light increases the binding of HCO−3 in the presence of DCMU. The high binding constant for HCO, discriminates strongly among the various hypotheses attempting to explain the “bicarbonate‐effect” on photosystem II. The proposal by Stemler and Jursinic (Arch. Biochem. Biophys. 221, 227–237 1983), that HCO−3 is one of a class of monovalent anionic inhibitors of photosystem II, is favored. These anions compete for a specific binding site on the photosystem II complex.
PHOTOSENSITIZATION OF PYRIMIDINES BY 2‐METHYLNAPHTHOQUINONE IN WATER: A LASER FLASH PHOTOLYSIS STUDY
Authors: Fisher Gordon J. , Land Edward J.
Published: January 2008

2‐Methylnaphthoquinone (MQ) has been excited in water with a 20 ns laser flash at 353 nm and the resultant transient species have been observed optically. Triplet‐state MQ (3MQ) decays on a sub‐microsecond time scale. It has been characterized in terms of its absorption spectrum and quantum yield. Rate constants have been measured for the decay of3MQ in infinitely dilute solution, for self‐quenching by ground‐state MQ, and for reactions of3MQ with oxygen, thymine, uracil, 6‐methyluracil, and orotic acid. The interaction of3MQ with pyrimidines involves charge transfer to give the pyrimidine cation radical and the MQ : anion radical. These reactions are discussed in relation to the mechanism of pyrimidine photooxidation sensitized by MQ.
DOSE‐TIME DEPENDENCY OF TUMOR FORMATION BY CHRONIC UV EXPOSURE
Authors: R.DeGruijl F. , Der Meer J.B. Van , Der Leun J. C. Van
Published: January 2008

‐An animal experiment is presented which involved a total of 223 albino hairless mice (Skh hr 1). These mice, excluding 24 of them which served as controls, were divided over 6 groups, each of which received a different but constant daily dose of UV radiation from fluorescent sunlamps (Westinghouse FS40TL12). The range of daily doses encompassed a factor of 33. Data on the response of each group as a whole are presented. The group responses are measured in two ways: (1) the proportion of tumor bearing mice (prevalence), and (2) the average number of tumors per survivor (yield). The data provide information on the variation of the group response with time, daily dose and tumor size.

The relationship between the daily dose and the duration of the treatment till 50% of the mice have tumors is given for several sizes of tumors. From these results, and from direct measurements of tumor growth, it appears that the growth of tumors is virtually dose‐independent and, in consequence, only the initiation of tumors is dose‐dependent. This implies that the theoretical model of UV‐tumorigenesis presented by Blum (1959). based on UV‐accelerated growth, is incorrect. It is pointed out that, in similarity to chemo‐ and radiotumorigenesis, the total dose delivered to a mouse for the induction of tumors has to be higher if a high daily dose is used than if a low daily dose is used. It seems as though an animal becomes more resistant to the UV‐stimuius as the rate at which the stimulus is presented is increased: an adaptive phenomenon.
ENERGY‐REGULATED FUNCTIONAL TRANSITIONS OF CHLOROPLAST ATPASE
Authors: Schuurmans J. J. , Kraayenhof R.
Published: January 2008

The functional transitions of the membrane‐bound chloroplast ATPase (CF1) as influenced by low ADP and uncoupler concentrations are investigated by measurements of initial and steady‐state ATP hyrolysis and concomitant membrane energization. Following activation of latent ATP hydrolysis by light in the presence of dithioerythritol, the resulting steady‐state ATP hydrolysis depends on the dark‐period (td) bteween light activation and ATP addition. ADP, added during td, inhibits this activity (Ki about 2 μM) and induces a lag in the onset of ATP hydrolysis. The extent of membrane energization as monitored by an aminoacridine fluorescent probe is proportional to the ATPase activity.

An uncoupler amplifies the inhibitory effect of ADP if added during fd, whereas it induces the normal stimulation of ATP hydrolysis in the absence of ADP. The ADP effect, which is different from product inhibition, is interpreted as a conformational interaction with CF1 causing an increase of the energy threshold required for the inactive → active transition of the CF1 molecules. These results are in harmony with currently proposed models of CF1 regulation by adenine nucleotides based on binding studies.

The inactive → active transition of CF1 conformation is investigated by analysis of the lag in the onset of ATP hydrolysis at different ADP concentrations and by means of varied light pulses and single‐turnover flashes, using the electric potential indicating absorption change at 515 nm as a probe for the onset of ATP hydrolysis. The half‐time of the process leading to fully (re)activated ATP hydrolysis is about 0.25 s. The ATP‐dependent flash‐induced inactive → active transition occurs within a few turnovers of electron flow.
TIME RESOLVED STUDIES OF 1.27 μm LUMINESCENCE FROM SINGLET OXYGEN GENERATED IN HOMOGENEOUS and MICROHETEROGENEOUS FLUIDS
Authors: Rodgers Michael A. J.
Published: January 2008

‐The luminescence at 1.27 μm from the 3→→1δg transition of the oxygen molecule has been detected from a variety of liquid systems. A Q‐switched laser delivering pulses of 532 nm light was the excitation source, a germanium photodiode was the detector and substituted porphyrins were used as photosensitizers. Protio‐ and deutero‐ forms of several solvents were studied and the singlet oxygen lifetimes determined directly agreed well with published values. Tδ in D2O was found to be 55 μs and, by extrapolation from a series of H2O ‐ D2O mixtures, a value of 3.3 μs was obtained for Tδ in H2O. The technique was shown to be useful in measuring Tδ values in several microheterogeneous systems such as surfactant micelles, vesicles and human serum albumin.
QUENCHING AND PHOTOBLEACHING OF EXCITED POLYCYCLIC AROMATIC HYDROCARBONS BY CARBON TETRACHLORIDE AND CHLOROFORM IN MICELLAR SYSTEMS
Authors: Encinas María V. , Rubio María A. , Lissi Eduardo
Published: January 2008

—Aromatic hydrocarbons incorporated into cetyltrimethylammonium chloride (CTACl) or sodium dodecylsulphate (SDS) micelles are efficiently quenched and photobleached by carbon tetrachloride. Similar results were obtained employing chloroform, but the efficiency of this compound as a quencher is nearly 103 times smaller than that of carbon tetrachloride.

Bimolecular quenching constants, with the quencher concentration given in moles per liter of micellar pseudophase, have been evaluated and compared with those obtained in homogeneous solutions. For slow processes, the values obtained would indicate that the polarity sensed by the probe depends both upon the probe and the surfactant. For diffusionally controlled processes (i.e. quenching of biphenyl), bimolecular quenching constants are considerably smaller in the micellar pseudophase. For these processes the pseudo‐first‐order quenching rate constants are larger in SDS than in CTACl micelles. This effect is partly due to the smaller size of the SDS micelle but also is a consequence of a lower “microviscosity” of these micelles.
FLUORESCENCE DECAY OF THE ACRIDINE ORANGE‐SODIUM DODECYL SULFATE SYSTEM: FORMATION OF DYE‐RICH INDUCED MICELLES IN THE PREMICELLAR REGION*
Authors: Ban Taketora , Kasatani Kazuo , Kawasaki Masahiro , Sato Hiroyasu
Published: January 2008

The fluorescence decay behavior was studied for the acridine orange (AO)‐sodium dodecyl sulfate (SDS) system in order to investigate the nature of the dye‐detergent interaction, especially in the premicellar region, i.e. below the critical micelle concentration (cmc). The fluorescence spectra and decay behavior were found to depend on [AO] and [SDS]. An exponential fluorescence decay with a lifetime of 3‐4 ns was found for large [SDS]s together with a fluorescence band at 545 nm and the monomer‐type absorption spectrum. This can be attributed to the monomer dye associated with micelles. For smaller [SDS]s where the fluorescence band at 640 nm appeared together with a dimer band in absorption spectra, slower fluorescence decays were observed when we probed the long‐wavelength region (λobs > 620 nm). These decays can be attributed to the dimer of the dye associated with micelles. The presence of this slower decay below the cmc directly proves the presence of dye‐rich induced micelles. The distribution of dye molecules among the dye‐rich induced micelles is discussed assuming that the same fluorescence behavior is the consequence of the same distribution of dye molecules among micelles (above the cmc) or among dye‐rich induced micelles (below the cmc).
SYNTHETIC MODELS RELATED TO DNA‐INTERCALATING MOLECULES. INTERACTIONS BETWEEN 8‐ALKOXYPSORALEN AND ADENINE*
Authors: Decout Jean Luc , Lhomme Jean
Published: January 2008

To investigate the interactions and the photoreactions between furocoumarins and adenine, we have synthesised compounds in which a psoralen molecule is linked by different polymethylene bridges to adenine. Ring‐ring intramolecular interactions are observed by UV spectroscopy. Thermodynamic parameters of these hydrophobic interactions are determined by the study of the variation of the hypochromic effect with temperature.
QUANTUM YIELD OF SINGLET OXYGEN PRODUCTION BY XANTHENE DERIVATIVES
Authors: Gandin E. , Lion Y. , Van de Vorst A.
Published: January 2008

The singlet oxygen quantum yield (ϕ1o2) of 11 purified fluorescein derivatives was determined by reaction with singlet oxygen acceptors in aqueous and ethanolic solutions; in both solvents ϕ1o2 was enhanced with increasing halogenation. Tryptophan and 2,2,6,6‐tetramethylpiperidone were found to be unadapted for the determination of ϕ1o2, in our systems; however, the use of 9.10‐dipropionic anthracene acid andp‐nitrosodimethylaniline in conjunction with imidazole derivatives was suitable for 1O2 detection in water. Both methods lead to results in excellent agreement. As in ethanol. ϕ1o2, was equal to the triplet state quantum yield (ϕT), the comparison between the two solvents showed that ϕT in water was greater than in ethanol. The comparison between our values obtained with polychromatic light with published data obtained with monochromatic light suggests that the triplet quantum yield of fluorescein derivatives is wavelength independent.
GROWTH DEPENDENT LUMINESCENCE FROM CULTURES OF NORMAL and RESPIRATORY DEFICIENT SACCHAROMYCES CEREVISIAE
Authors: Quickenden T. I. , Tilbury R. N.
Published: January 2008

—Luminescence was detected from oxygenated, liquid cultures of the yeast Saccharomyces cerevisiae with a photon counter sensitive between 200 and 600 nm. Four periods of emission were observed: (1) during the late exponential phase (137 ± 6 counts s−1); (2) during the early stationary phase (118 ± 24 counts s−1); (3) during the late stationary phase (ca. 1000 counts s−1); and (4) during the very late stationary phase (ca. 1000 counts s−1). Emissions (3) and (4) have not been previously reported. Experiments in which the yeast was temporarily separated from the nutrient medium suggested that all of the luminescences arose from within the yeast cell. Respiratory deficient (“petite”) mutants of S. cerevisiae gave similar emissions, except that the first and third emission peaks were more intense and an early shoulder appeared on the first peak. All of the emissions from normal and “petite” cultures disappeared when the yeast was grown anaerobically. It was concluded that the luminescences do not arise from any of the reactions in the fermentative and respiratory pathways and that O−2, may be involved in the processes leading to emission.
BEHAVIORAL RESPONSES IN Paramecium multimicronucleatum TO VISIBLE LIGHT
Authors: Iwatsuki Kenji , Naitoh Yutaka
Published: January 2008

Specimens of colorless Paramecium multimicronucleatum were found to respond to visible light. They accumulated in the shaded region (photodispersal) of a half‐shaded glass tube during 2 min exposure to visible light. The specimens showed avoiding reaction upon both spatial and temporal increase in light intensity (step‐up photophobic response). Steady‐state swimming velocity (orthokinesis) was higher, while steady‐state frequency of spontaneous change in swimming direction (klinokinesis) was lower when the light intensity was kept higher. In a light with wavelength of 440 nm the velocity was highest, while the frequency was lowest. The specimens did not show phototaxis (light direction‐oriented locomotion). Spectral sensitivity curves for both the photodispersal and the step‐up photophobic response showed a major peak at 520 nm and a minor peak at 680 nm. The photodispersal seems to be caused mainly by the step‐up photophobic response exhibited by the specimens at the dark‐light border. The photokinetic responses enhance the degree of the photodispersal.
STIMULATION OF BIOLUMINESCENCE IN DINOFLAGELLATES BY RED LIGHT*
Authors: Sweeney Beatrice M. , Fork David C. , Satoh Kazuhiko
Published: January 2008

In three species of dinoflagellate, Gonyaulax polyedra, Pyrocyslis fusiformis and Pyrocvstis lunula, bioluminescence can be stimulated by light. This phenomenon is observed if the cell suspension is rendered anaerobic by any of the following treatments: N2gas. metabolically active yeast. glucose plus glucose oxidase, dithionite or allowing a concentrated cell suspension to stand for several hours in darkness, conditions which remove oxygen from the cell suspension. An alternate pretreatment is inclusion of carbonylcyanide‐m‐chlorophenyl hydrazone or hydroxylamine in the cell suspension. The emission spectrum with a maximum at 478 nm identifies dinoflagellate luciferin as the emitter. The action spectrum (maximum at 675 nm in the red region of the spectrum) points to chlorophyll as the photoreceptor. Evidence for the participation of PS II of photosynthesis in the light‐stimulation of bioluminescence is the strong inhibition of light emission by 3‐(3.4‐dichlorophenyl)‐l.l‐dimethylurca (DCMU) and 2,5‐dibromo‐3‐isopropyl‐p‐benzoquinone and the failure of diaminodurol + ascorbate to reverse the inhibition by DCMU. The observation that, with short irradiations (5 μ.s). no bioluminescence is emitted until the third flash also suggests photosystem II (PS II) as the site of stimulation. The evolution of oxygen is not involved in the light‐stimulation of bioluminescence. since oxygen evolution is completely inhibited by NH2OH, while light emission is potentiated by the presence of NH2OH. A consideration of the action of inhibitors suggests that the stimulation of light emission is the result of a change in membrane potential produced upon irradiation of PS II. This membrane potential is not caused by the movement of protons.
HOST CELL REACTIVATION BY FIBROBLASTS FROM PATIENTS WITH PIGMENTARY DEGENERATION OF THE RETINA
Authors: DavidLytle C. , Tarone RobertE. , Barrett SusannaF. , Wirtschafter JonathanD. , Dupuy Jean‐Marie , Robbins JayH.
Published: January 2008

–Cockayne syndrome (CS) is an autosomal recessive disease characterized by numerous clinical abnormalities including acute sun sensitivity and primary pigmentary degeneration of the retina. Cultured fibroblasts from CS patients are hypersensitive to ultraviolet (UV) radiation. Since host cell reactivation of irradiated virus is a useful probe to evaluate repair in different host cells, we studied such host cell reactivation in CS and in other diseases with retinal degeneration. The survival of UV‐irradiated Herpes simplex virus type 1 was determined in fibroblast lines from four normal donors. two patients with CS, one with both xeroderma pigmentosum (XP) and CS, and from several other patients with (Usher syndrome, olivopontocerebellar atrophy, retinitis pigmentosa) and without (XP, ataxia telangiectasia) primary pigmentary degeneration of the retina. The viral survival curves (log survival vs linear fluence) in all cell lines showed two components: a very sensitive initial component (not quantitated in this study) followed by an exponential, less sensitive component. The exponential component had greater sensitivity than normal in the case of the CS patients, the patient with both XP and CS. and the XP patient. We propose that patients with CS have defective repair of DNA which may be the cause of their retinal degeneration.
HYDROGEN and OXYGEN PHOTOPRODUCTION BY MARINE ALGAE*
Authors: Greenbaum E. , Guillard R. R. L. , Sunda W. G.
Published: January 2008

Abstract The first measurements of the simultaneous photoproduction of hydrogen and oxygen in marine green algae are reported. Eight species in the genera Chlamydomonas, Chlorella and Halochlorocococcum were tested in CO2‐free seawater. Four of the five species of Chlamydomonas were able to produce hydrogen in the light after a period of 3 ‐ 4 h of dark anaerobic adaptation. Only one of the two Chlorella species tested was able to photoproduce hydrogen, in trace amounts. Halochlorocococcum fla–9 gave positive results and Chlamydomonas species (clone f‐9) had a steady‐state rate of hydrogen and oxygen production during irradiation with a stoichiometric ratio near 2:1. The integrated yields of hydrogen and oxygen produced by this species corresponds to about 450 turnovers of the photochemical reaction centers. This number exceeds (by about a factor of 20) the electron‐carrying capacity of the electron transport chain linking Photosystems I and II. These data suggest that Chlamydomonas f‐9 makes seawater a potential substrate for solar hydrogen and oxygen production.
TRANSMISSION OF UV‐RADIATION THROUGH HUMAN EPIDERMAL LAYERS AS A FACTOR INFLUENCING THE MINIMAL ERYTHEMA DOSE
Authors: BRULS WIEL A. G. , VAN WEELDEN HUIB , VAN DER LEUN JAN C.
Published: January 2008

Abstract— The extent to which transmission of human Caucasian epidermis and stratum corneum influences the Minimal Erythema Dose (MED) was examined for UV‐B and UV‐C.

Transmission correlated well with variations in MED for UV‐B and UV‐C that exist between individuals, as measured on the skin of the lower back and anterior upper leg.

Regional differences of the MED that occur within the same individual between different parts of the body, were related less well to differences in transmission. For UV‐B, the difference in transmission of stratum corneum and epidermis between upper leg and lower back was on the average too small to completely account for the difference in MED UV‐B. Other parameters, therefore, have to be involved in determining such regional variations in MED UV‐B. For UV‐C, on average, the difference in transmission of stratum corneum was smaller and of epidermis larger than the difference in MED UV‐C between upper leg and lower back, though the deviations were not significant.

A series of UV‐B irradiations of the lower back resulted in an increase in MED UV‐B and MED UV‐C, which was paralleled by a decrease in transmission of stratum corneum and epidermis. The average decrease in UV‐B transmission of stratum corneum was too small and that of epidermis somewhat too large to account for the average increase in MED UV‐B. The average decrease in UV‐C transmission of stratum corneum was about as large as the average increase in MED UV‐C. Consequences of these observations for the location of the primary reactions leading to erythema are discussed.

The relationship between log MED UV‐C and log MED UV‐B was confirmed to be approximately linear.
PHOTOCHEMICAL ADDITION OF AMINO ACIDS AND PEPTIDES TO HOMOPOLYRIBONUCLEOTIDES OF THE MAJOR DNA BASES
Authors: SHETLAR MARTIN D. , HOM KELLIE , CARBONE JOHN , MOY DAVID , STEADY ELAINE , WATANABE MARK
Published: January 2008

Abstract— The photochemical quantum yields for addition of glycine and the L‐amino acids commonly occurring in proteins (excluding proline) to polyadenylic acid, polycytidylic acid, polyguanylic acid and polyribothymidylic acid have been determined in deoxygenated phosphate buffer at Λ 254 nm and pH 7, using a fluorescamine assay technique. Polyadenylic acid was reactive with eleven of the twenty amino acids tested, with phenylalanine, tyrosine, glutamine, lysine and asparagine having the highest quantum yields. Polyguanylic acid reacted with sixteen amino acids; phenylalanine, arginine, cysteine, tyrosine, and lysine displayed the largest quantum yields. Polycytidylic acid showed reactivity with fifteen amino acids with lysine, phenylalanine, cysteine, tyrosine and arginine having the greatest quantum yields. Polyribothymidylic acid, reactive with fifteen of nineteen amino acids surveyed, showed the highest quantum yields for cysteine, phenylalanine, tyrosine, lysine and asparagine. None of the polynucleotides were reactive with aspartic acid or glutamic acid.

The quantum yields for photoaddition of eighteen dipeptides of the form glycyl X (X being one of the amino acids commonly occurring in proteins, including proline), and of L‐alanyl‐L‐tryptophan, L‐seryl‐L‐seryl‐L‐serine, L‐threonyl‐L‐threonyl‐L‐threonine, L‐cystine‐bis‐glycine, and Nα‐acetyllysine to polyadenylic acid, polycytidylic acid and polyguanylic acid were measured. All of these were found to add photochemically to each of these polymers. Polyribothymidylic acid, tested with eleven of these peptides and with Nα‐acetyllysine, was found to be reactive with all.
EXCITATION ENERGY TRANSFER IN THE LIGHT HARVESTING ANTENNA SYSTEM OF THE RED ALGAPorphyridium cruentumAND THE BLUE‐GREEN ALGAAnacystis nidulans: ANALYSIS OF TIME‐RESOLVED FLUORESCENCE SPECTRA
Authors: YAMAZAKI I. , MIMURO M. , MURAO T. , YAMAZAKI T. , YOSHIHARA K. , FUJITA Y.
Published: January 2008

Abstract—Time‐resolved fluorescence spectra of intact cells of red and blue‐green algaePorphyridium cruentumandAnacystis nidulanswere measured by means of a ps laser and a time‐correlated photon counting system. Fluorescence spectra were observed successively from various pigments in the light harvesting system in the order of phycoerythrin (PE), phycocyanin (PC), allophycocyanin (APC) and chlorophylla(Chla). The spectrum changes with time in the range of0–400 ps inP. cruentumand of0–1000 ps inA. nidulans. The time‐resolved spectra were analyzed into components to obtain the rise and decay curve of each fluorescence component. Overall time behaviors of the sequential fluorescence emissions from various pigments can be interpreted with a decay kinetics ofexp(–2kt½). The rate constants of the energy transfer show that the energy transfer takes place much faster in the red algaP. cruentumthan in the blue‐green algaA. nidulans, particularly in the step PCAPC. Results also indicated that a special form of APC, far‐emitting APC, exists in the pigment system ofA. nidulans, but it does not mediate a main energy transfer from phycobilisome to Chla.
DIALKYLAMINOBENZONITRILES AS FLUORESCENCE POLARITY PROBES FOR AQUEOUS SOLUTIONS OF CYCLODEXTRINS
Authors: Cox G. Sidney , Hauptman Paul J. , Turro Nicholas J.
Published: January 2008

Abstract— The dual fluorescence of 4‐(N, N‐dimethylamino)benzonitrile and 4‐(N, N‐diethylamino)‐benzonitrile (DMABN and DEABN, respectively), has been studied in aqueous solutions of cyclodextrins. Fluorescence parameters (peak maximum, lifetime, and relative intensity) have been measured and are found to be consistent with the formation of complexes of probe and cyclodextrin. Enhanced emission of the twisted internal charge transfer state (TICT) fluorescence is observed in cyclodextrin, with the greatest effect for the DMABN/α‐cyclodextrin system. Our results promote further understanding of both the photophysical behavior of DMABN and the complexation of probe with cyclodextrin. The use of dialkylaminobenzonitriles as polarity probes is discussed.
A PHOTOACOUSTIC DEPTH PROFILE OF β‐CAROTENE IN SKIN
Authors: Anjo Dennis M. , Moore Thomas A.
Published: January 2008

Abstract— Photoacoustic spectroscopy has been used to observe a qualitative depth profile in vitro in mouse skin. Because the photoacoustic response is a vector quantity, it can be used to qualitatively determine the depth of a chromophore in skin. The spectrum of an induced layer of β‐carotene in albino mouse skin was separated from the spectrum of hemoglobin. Dyes were then used to determine more precisely the position of the β‐carotene in the epidermis. The spectrum of melanin was also separated from that of the underlying hemoglobin in pigmented mouse skin.
STUDIES ON THE PHOTOPROTECTIVE MECHANISM OF BUTYLATED HYDROXYTOLUENE
Authors: Black Homer S. , Lenger Wanda , Gerguis Janette , McCann Virginia
Published: January 2008

AbstractIt has been suggested that butylated hydroxytoluene (BHT)‡, a phenolic antioxidant that conveys photoprotective properties to skin, may act by altering epidermal parameters that influence the level of ultraviolet light (UV) reaching critical target sites. The potential diminution of effective UV dose could account for the observed inhibition of UV‐induced ornithine decarboxylase (ODC). Thus studies were conducted to examine the possibility that BHT was capable of promoting epidermal proliferation, just as others have shown with lung epithelial cells. UV‐induction of ODC, in unrestrained Skh‐Hr‐I mice irradiated with Westinghouse FS–20 lamps, was shown to be linearly responsive from 0.3 to 0.6, J/cm2/dose. The degree of inhibition afforded by dietary BHT was approximately constant over this dose range. In addition, intraperitoneal administration of BHT (400 mg/kg) inhibited UV‐induced ODC as greatly as when provided dietarily. Greatest inhibition occurred when BHT was administered at least 46 h prior to UV exposure, with the inhibitory event(s) requiring over 20 h to become effective. However, BHT had no effect, during this time interval, upon the incorporation of [3H]thymidine or leucine into DNA and protein, respectively. Nor were BHT effects reflected in the epidermal labeling index. These data suggest that BHT does not induce epidermal proliferation. An alternate explanation, in which the antioxidant properties of BHT play a major role, is proposed.
TRIPLET ENERGY TRANSFER TO CHLOROPLASTS FROM PEROXIDASE‐GENERATED EXCITED ALIPHATIC ALDEHYDES
Authors: Campa Ana , Nassi Lilian , Cilento Giuseppe
Published: January 2008

AbstractLinear aldehydes trigger red emission from chloroplasts. If horseradish peroxidase is present, the aldehyde is oxidized to the next lower homologue in the triplet state, which in turn sensitizes chlorophyll fluorescence. Only certain chlorophylls are activated.