bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF PROTONATION ON THE ISOMERIZATION PROPERTIES OF n‐BUTYLAMINE SCHIFF BASE OF ISOMERIC RETINAL AS REVEALED BY DIRECT HPLC ANALYSES: SELECTION OF ISOMERIZATION PATHWAYS BY RETINAL PROTEINS
Authors: Koyama Yasushi , Kubo Keishi , Komori Mika , Yasuda Haruo , Mukai Yumiko 
Published: January 2008

ReferencesAlumina adsorption chromatography and ion‐pair reversed‐phase chromatography were developed to analyze the isomers of unprotonated and protonated n‐butylamine Schiff base of retinal (RSB and PRSB), respectively. Photoisomerization starting from the &‐\\trans, l\‐cis and 13‐cw isomers was traced for RSB in n‐hexane, acetonitrile, methanol and 1‐butanol, and for PRSB in methanol, acetonitrile and 1‐butanol. The quantum yields of photoisomerization for the a\\‐trans, 9‐cis, 11‐cis and 13‐ris isomers were determined for RSB and PRSB in the above solvents except 1‐butanol. On the other hand, photoisomerization of isomeric retinal bound (through Schiff base linkage) to bovine serum albumin (RBSA) in aqueous solution (pH 3, 7 and 12) as well as thermal isomerization of RSB (in n‐hexane), PRSB (in methanol) and RBSA (in aqueous solution, pH 7) were traced starting from the a\l‐trans, 11‐cw, and 13‐cis isomers.Protonation of RSB drastically changes the pathway of photoisomerization and increases the quantum yields of isomeric RSB. The solvent polarity increases the quantum yields of RSB differently depending on the configuration. Protonation enhances thermal isomerization also. The results of the above model systems are compared with those of retinal proteins to rationalize their selection of the particular isomerization pathways.
PHOTOCHEMISTRY OF 1‐PYRENYLDIAZOMETHANE*
Authors: Silva Salom , Olea Andreas F. , Thomas J. K. 
Published: January 2008

ReferencesPhotoexcitation of 1‐pyrenyldiazomethane (1) leads to carbenes which attach to various molecules, e.g. surfactants, polymers, hydroxylated surfaces. This provides a convenient method of labelling these compounds with pyrene for probe studies of complex structures and surfaces. Photophysical and photochemical studies of the various events resulting from the photoexcitation of 1, show that the quantum yield for disappearance of 1 and of carbene formation is low (∼ 5%) and that other processes lead to relaxation of excited 1, in particular fluorescence and intersystem crossing. The mechanism involves a mixing of low lying π‐π* states of the pyrene chromaphore with diazo n‐π+ states, and is discussed in the light of other similar systems and the present studies.
PHOTOREACTIVATION OF ULTRAVIOLET RADIATION‐INDUCED RELEASE OF ARACHIDONIC ACID FROM MARSUPIAL CELLS
Authors: Kaleta Elzbieta W. , Applegate Lee A. , Ley Ronald D. 
Published: January 2008

AbstractExposure of an established marsupial cell line, PtK2(Potorous tridactylus), to ultraviolet radiation (UVR) from an FS‐40 sunlamp (280–400nm) resulted in a fiuence‐dependent release of radiolabeled arachidonic acid (AA) from cell membranes. Post‐UVR, but not pre‐UVR, exposure to photoreactivating light reversed UVR‐induced pyrimidine dimers in DNA and suppressed the UVR‐induced release of AA. These data indicate that DNA damage contributes to the release of AA from membrane phospholipids.
SOLAR ULTRAVIOLET RADIATION IN SOUTHEAST ENGLAND: THE CASE FOR SPECTRAL MEASUREMENTS
Authors: Webb Ann R. 
Published: January 2008

AbstractSpectral measurements of the solar ultraviolet spectrum have been made at Reading, England, since July 1989. The data presented show the daily and annual changes in the ultraviolet‐B (UV‐B) part of the spectrum, and illustrate the dominance of the longer wavelengths in grouping the data into a single broadband measurement. The temporal changes (diurnal and annual) cover 2 orders of magnitude at 300 nm, and a factor of 5 at 320 nm. In a single statement of UV‐B levels the trend at longer wavelengths predominates, hiding the larger differences at the more biologically important wavelengths. However, the data also show that at mid‐high latitudes the UV irradiance at noon in winter is less than that received at any time during the middle 12 h of daylight in summer, and this should be acknowledged when assessing the consequences of ozone depletion. Atmospheric scattering of short wavelength radiation is compared to that of the entire solar spectrum from measurements of diffuse radiation: on a clear day70–100% of UV‐B was diffuse in Reading, with a slight wavelength dependency increasing diffuse radiation at short wavelengths. Under the same conditions scattering of total solar radiation was 21%. The effect of cloud cover is briefly discussed for two specific cases of complete, uniform cloud cover, when attenuation by clouds was approx. 40 and 68%, with little wavelength dependence in either case.
DOUBLET Stentor DO NOT DISPLAY PHOTODISPERSAL
Authors: WOOD DAVID C. , MARINELLI RICCARDO 
Published: January 2008

Abstract—Normal Stentor, called singlets since they have a single membranellar band and oral groove surrounding their frontal field, swim away from light sources and collect in the darker areas of an unevenly illuminated container (photodispersal). Phenotypic variants, called doublets since they have 2 membranellar bands and 2 oral grooves, do not exhibit this behavior. Doublets produce photophobic responses and contractions when illuminated at the same fluence rates which produce those responses in singlets, hence their sensitivity to light is normal. Illumination of the frontal field of doublets produces a photophobic response at lower fluence rates than does illumination of their side or posterior. This directional sensitivity is quantitatively similar to that observed in singlets. However, doublets do not reorient their swimming direction after a phobic response as extensively as do singlets. This failure in reorientation is the probable reason that doublets fail to show photodispersal. These results imply that the mechanism producing photodispersal in singlets depends on photophobic responses or some other, presently undescribed, response which requires an asymmetric frontal field.
A NEW FLUORESCENT CHOLESTEROL DERIVATIVE: STRUCTURE AND BLOOD PLASMA ANALYSIS
Authors: Abubaker M. Amin , Wandruszka Ray Von 
Published: January 2008

Abstract—A fluorescent cholesterol derivative produced by reaction with gaseous HCI and zinc chloride in ethyl acetate is shown to be a chlorine substituted B‐ring diene. The species forms relatively rapidly via an i‐steroid rearrangement, requiring a temperature around 70°C. A weak, possibly dimeric π‐allyl zinc complex exists in solution, leading to a red shift in the fluorescence emission. The application of the derivative to the determination of cholesterol in bovine plasma provides good sensitivity and precision and requires notably small sample volumes.
OXIDATION OF PHOSPHATIDYLCHOLINE MEMBRANES BY SINGLET OXYGEN GENERATED IN THE GAS PHASE
Authors: Eisenberg Walter C. , Anand Jasbir , Wang Shukun , Stevenson Robert J. 
Published: January 2008

Abstract—Singlet‐oxygen (1O2) was generated in the gas phase by heterogeneous photosensitization and bubbled into suspensions of phosphatidylcholine (PC) liposomes. Lipid peroxidation and membrane lysis were observed, and were dependent on the 1O2 concentration and the degree of unsaturation of the liposome. An analysis based on large target diffusion theory indicates that approximately 5000, 2800, and 1600 interactions were required for the lysis of large dioleoylPC, dilinoleoylPC and dilinolenoylPC liposomes, respectively.
PHYSIOLOGICAL RELATIONSHIPS BETWEEN PHYTOCHROME EFFECTS ON INTERNODE EXTENSION GROWTH AND DRY MATTER ACCUMULATION INLIGHT‐GROWN MUSTARD
Authors: Casal Jorge J. , Sanchez Rodolfo A. 
Published: January 2008

Abstract—The physiological relationships between the effects of phytochrome photoequilibrium (Pfr/P) on internode extension growth and dry matter accumulation were investigated in white light (WL)‐grownSinapis albaL. seedlings. After 11 days under continuous WL, the seedlings were exposed: (a) to pulses of light providing different Pfr/P, followed by 24 h darkness (D); (b) to pulses of light providing different Pfr/P, followed by 3 h D and 24 h continuous WL; (c) to continuous WL with or without supplementary far‐red light (to reduce Pfr/P); or (d) to pulses of light providing different Pfr/P followed by D, in factorial combination with either water or a saturating (0.2M) sucrose solution applied to one of the leaves. In D (“a” and “d”) low, compared to high Pfr/P increased both internode extension growth and dry weight to the same extent. Under WL (“b” and “c”) low PfrlP promoted internode extension growth but had no proportional effects on internode dry weight. Sucrose promoted internode extension growth with a lag of at least 8 h (compared to the rapid effect of low Pfr/P) and did not reduce the effect of low Pfr/P. These results indicate that Pfr/P effects on internode extension growth are not the consequence of changes in photoassimilate translocation from the leaves. Under WL, PfdP effects on internode length occur partially at the expense of internode dry matter per unit length.
DIRECT MEASUREMENT OF PHYTOCHROME PHOTOCONVERSION INTERMEDIATES AT HIGH PHOTON FLUENCE RATES
Authors: Smith Harry , Fork David C. 
Published: January 2008

Abstract—A custom‐built modulated split‐beam spectrophotometer has been used to measure the absorbance of tissue samples and purified phytochrome whilst exposing the sample to actinic 633 nm laser radiation at fluence rates approaching those of daylight. This approach has allowed the direct observation of the accumulation of phytochrome photoconversion intermediates at high fluence rates. Atca1250 μmol m−2s−1upwards of 35% of the total phytochrome was present in the form of photoconversion intermediates in tissues of maize, sunflower and tomato. In other tissues tested (wheat, bean andAmaranthus) and in purified oat phytochrome, rather smaller levels of intermediates accumulated. Upon “lights‐off” only a proportion of the accumulated intermediates decayed to far‐red absorbing phytochrome (Pfr), the remainder appearing as the red‐absorbing form (Pr). Difference spectra suggested that, at high light levels, Pr may be reformedviaa photochemical back‐conversion of an intermediate in the Pr—Pfr pathway, although the involvement of intermediates in the Pfr—Pr pathway cannot be excluded. The implications of the results for the ecological function of phytochrome are discussed.
THE DISTANCE BETWEEN THE PHYTOCHROME CHROMOPHORE AND THE N‐TERMINAL CHAIN DECREASES DURING PHOTOTRANSFORMATION. A NOVEL FLUORESCENCE ENERGY TRANSFER METHOD USING LABELED ANTIBODY FRAGMENTS
Authors: Farrens David L. , Cordonnier Marie‐Michèle , Pratt Lee H. , Song Pill‐Soon 
Published: January 2008

Abstract—A novel antibody‐fluorescence method has been developed to elucidate the chromophore topography in phytochrome as it undergoes a photochromic transformation. Förster energy transfer from N‐terminal bound, fluorescently labeled Oat‐25 Fab antibody fragments to the phytochrome chromophore was measured. The results suggest that the chromophore moves relative to the N‐terminus upon the Pr → Pfr phototransformation. This conclusion is consistent with previous models which have proposed a reorientation and an interaction of the Pfr chromophore with the N‐terminus. The method described appears to be the first study of a Forster energy transfer measurement using a donor‐label attached to a Fab fragment of a photosensor protein.
SPECTRAL MODIFICATIONS OF BACTERIAL ANTENNA COMPLEXES BY LIMITED PROTEOLYSIS
Authors: Brunisholz René A. , Zuber Herbert 
Published: January 2008

AbstractThe spectral effects of a number of endo‐ and exoproteases to the detergent‐solubilized antenna complexes B802–858(sphaeroides like) of strain Rhodopseudomonas acidophila 10050 and B802–824of strain 7050 were analyzed. Upon protease digestion the time course of spectral modification between 250 and 900 nm was recorded. In addition, circular dichroism (CD) signals were measured between 450 and 950 nm. The endoprotease elastase as well as the exoprotease carboxypeptidase A (CP A) altered the B802–858antenna complex, by changing the 858 nm band hypochromically (30‐50%) with an additional small hypsochromic shift (3–6nm). A combined carboxypeptidase digestion, e.g. CP A and CP B, yielded a further modification to a complex with absorption bands at 800 nm and ˜840 nm (ε˜ 50% of the 800 nm band). By exposing the isolated B803–824antenna complex to the different proteases no significant spectral change was observed. The B802–858antenna complex, modified by CP A, exhibits a60–70% decrease of the biphasic CD signal in the near infrared. The limited proteolysis experiments provide conclusive experimental evidence that the C‐terminal domains of the antenna polypeptides α and β contribute to the formation of (dimeric) bacteriochlorophyll (BChl) a molecules absorbing at around 850 nm. This agrees with the hypothesis, based on comparative amino acid sequence analysis, that in purple bacterial antenna complexes the structural requirements (specific amino acids in the vicinity of the BChl molecules, e.g. aromatic amino acids) for batho‐ and hyperchromicity of BChl molecules apparently reside to a considerable extent in the C‐terminal portions of their antenna apoproteins.
THEORY OF POLARIZED FLUORESCENCE FROM MOLECULAR PAIRS: FÖRSTER TRANSFER AT LARGE ELECTRONIC COUPLING
Authors: Knox Robert S. , Gülen Demet 
Published: January 2008

AbstractPolarization properties of the fluorescence from a pair of identical molecules coupled electronically are examined on the basis of a stochastic Liouville equation formalism developed in 1979 by Rahman, Knox and Kenkre. The time development of polarization is calculated for random ensembles of rigid molecule pairs under initial conditions that represent either selective excitation or broad‐band coherent excitation. We hold that the applicability of the Forster mechanism is not limited to cases of weak coupling, and we indicate the rationale and a method for observing it in cases involving large interaction between transition dipoles.
CONCENTRATION DEPENDENCE OF TRANSMISSION LOSSES IN UV‐LASER IRRADIATED BOVINE α‐, βH‐,βL‐AND γ‐CRYSTALLIM SOLUTIONS
Authors: Borkman J. L. Hott and F. 
Published: January 2008

AbstractExperiments with calf lens protein fractions in aqeous buffer solutions at room temperature showed that βH ‐ and βL ‐ and γ‐crystallin fractions became opaque following ultraviolet exposure at 308 nm, while the α‐crystallin fraction remained transparent. Transmission loss, due to UV‐irradiation, for all of the crystallin samples was studied in the concentration range of 0.1 mg/mL to 1.0 mg/mL, and for α‐ and γ‐crystallin, in the range up to 5 mg/mL. With increased concnetrations of βH‐,βL‐and γ‐crystallin, the rate of opacification increased. However, with α‐crystallin, the loss of transmission was negligble for all of the concentrations and irradiation times studied. Opacification of the crystallins was accompanied by formation of higher molecular weight insoluble proteins as detected by SDS‐PAGE.
REGULATION OF UV‐PROTECTIVE PIGMENT SYNTHESIS IN THE EIPERMAL LAYER OF RYE SEEDLINGS (Secale cereale L. cv. KUSTRO)
Authors: Braun J. , Tevini M. 
Published: January 2008

Abstract Trans‐cinnamic acid is the product of the L‐phenylalanine ammonia lyase (PAL, EC 4.3.1.5) enzyme reaction and might regulate the subsequent phenylpropanoid synthesis by feedback inhibition of PAL activity. The partial conversion of trans‐cinnamic acids (e.g. trans‐p‐coumaric acid) and of trans‐p‐coumaryl‐glucoside (chemically synthesized model substance for cinnamic acid derivatives) to the cis isomers upon UV irradiation leads to reduced inhibition of PAL activity within minutes. In rye leaves this rapid enhancement of PAL activity (within minutes) causes a rapid increase in phenylpropanoids, which are predominantly located in the epidermal layer. Because phenylpropanoid derivatives are precursors of flavonoid biosynthesis, the observed rapid increase in flavonoid content after short‐term UV irradiation can be explained by this UV‐induced regulation mechanism. Consequently, transphenylpropanoids can be regarded as photoreceptors and regulators of the phenylpropanoid pathway during UV‐B (280–320nm) irradiation. In rye leaves an additional slower UV response, obviously by induction of genetic transcription as described for other plant systems, leads to a much greater flavonoid accumulation compared to the rapid induction.
MEMBRANE DAMAGE INDUCED IN CULTURED HUMAN SKIN FIBROBLASTS BY UVA IRRADIATION
Authors: Gaboriau F. , Morlière P. , Marquis I. , Moysan A. , Goegze M. , Dubertret L. 
Published: January 2008

AbstractIrradiation of cultured human skin fibroblasts with ultraviolet light from 320 to 400 nm (UVA) leads to a decrease in the membrane fluidity exemplified by an enhanced fluorescence anisotropy of the lipophilic fluorescent probe 1‐[4‐trimethylamino)‐phenyl]‐6‐phenylhexa‐1,3,5‐triene. This UVA‐induced decrease in fluidity is associated with lactate dehydrogenase leakage in the supernatant. Vitamin E, an inhibitor of lipid peroxidation, exerts a protective effect on both phenomena. Therefore, this UVA‐induced damage in membrane properties may be related to lipid peroxidation processes. Moreover, exponentially growing cells are more sensitive to these UVA‐induced alterations than confluent cells.
OPTIMIZATION OF MULTIFIBER LIGHT DELIVERY FOR THE PHOTODYNAMIC THERAPY OF LOCALIZED PROSTATE CANCER
Authors: Whitehurst C. , Pantelides M. L. , Moore J. V. , Blacklock N. J. 
Published: January 2008

AbstractThe understanding of light distribution within the target organ is essential in ensuring efficacy and safety in photodynamic therapy (PDT). A computer simulator of light distribution in prostatic tissue was employed for optimizing dosimetry for PDT in localized prostatic cancer. The program was based on empirically determined light distributions and optical constants and an assumed Ruence rate differential from fiber source to necrosis periphery. The diffusion theory approximation to the Boltzmann transport equation was the applicable formulation relevant to prostatic tissue, which has a high albedo with forward‐scattering characteristics. Solving this equation of diffusive transfer for the appropriate fiber geometry yielded the energy fluence distributions for cleaved fiber and cylindrical diffuser light delivery. These distributions, confirmed by our measurements, show a l/r and l/r dependency (r = distance from light source) of the fluence ø(r) for the cleaved fiber and diffuser, respectively. This manifests itself by the tighter spacing of energy fluence isodoses in the case of the cleaved fiber. It was predicted that for a typical PDT regime a single interstitially placed cleaved fiber would treat 0.05–0.72 cm3, Four parallel fibers improve the uniformity of light distribution and treatment volume, and an interfiber separation of 12 mm would be necessary to provide optimal overlap of PDT necrosis, treating 0.26–3.6 cm3. The cylindrical diffuser, however, could treat larger volumes, and it was predicted that four 3 cm long diffusers at an optimal separation of 25 mm would treat 25–88 cm3 of prostatic tissue.
BIOPHYSICAL AND BIOCHEMICAL ASPECTS OF PHENGODID (RAILROAD‐WORM) BIOLUMINESCENCE
Authors: Viviani Vadim R. , Becham Etelvino J. H. 
Published: January 2008

AbstractIn studies of the bioluminescence of 11 species of phengodid collected in central and southeast Brazil, we have found that: (1) their lateral lanterns emit light in the yellow‐green region (λmax= 540–580 nm) and the head lantern color is shifted to the red region (λmax= 565–620 nm), (2) the luciferins of both types of lanterns are identical to that of lampyrids and elaterids and (3) the luciferase physicochemical properties are also similar to those of lampyrids and elaterids (optimum pH ca 8.1; Km(ATP) = 260–370 μM, Kμ(luciferin) = 170–400 μM; molecular weight ca 60 kDa; apparent activation energy of in vitro bioluminescence ca 58 kJ/mol). Thus the bioluminescence system of phengodids appears to be essentially the same as that of lampyrids and elaterids. The different bioluminescence colors of the lanterns of Phrixothrix species (λhead= 600–620 nm; λlateral= 535–565 nm) and other phengodid species are probably elicited by the presence of luciferase isoenzymes, as occurs in the case of elaterid prothoracic and abdominal lanterns.
A MULTITHERAPY RESISTANCE FACTOR FROM MELANOMA REVEALS THAT KILLING BY NEAR UV IS DIFFERENT FROM GENOTOXIC AGENTS
Authors: Hill Helene Z. , Hill George J. , Cieszka Krystyna , Azure Michael , Chowdhary Indu , Sayre Robert M. 
Published: January 2008

AbstractA diffusible multitherapy resistance factor (MTRF) is produced by Cloudman S91 melanoma cells in vitro. The MTRF decreases sensitivity of the target cell line, S91/amel, to γ‐irradiation, UVC (200–280nm) and mitomycin C (MMC). In the present study, we demonstrate that MTRF also increases the survival of S91/amel after exposure to actinomycin D (AMD) and vinblastine (VBL). The MTRF is thus effective when target cells have been exposed to five genotoxic agents that act by different mechanisms. It does not alter the response to the same five agents of the S91/13 producer cells, which are presumably saturated with the factor. The factor has no effect on the survival of S91/amel cells that have been exposed to lethal doses of near monochromatic UVB (280–320nm) or UVA (320–400nm) or to polychromatic FS20 lamps. The lack of effectiveness of MTRF after cells have been exposed to near (300–400nm) UV radiation indicates that in this wavelength range, S91 melanoma cells are killed by mechanisms that are different from the lethal effects of the five genotoxic agents (γ‐irradiation, UVC, MMC, AMD and VBL) to which the target cells demonstrate a response.
QUENCHING OF METHYLCYCLOHEXANE FLUORESCENCE BY METHANOL*
Authors: Gryczynski Ignacy , Lakowicz Joseph R. 
Published: January 2008

Abstract—We measured the fluorescence emission spectrum and intensity decays of methylcyclohexane (MCH) when excited by simultaneous absorption of two photons at 298 nm. The steady‐state intensities and lifetimes were both decreased by methanol, which was found to be an efficient quencher of MCH fluorescence. Methanol quenching of MCH is clearly dynamic, but the exact mechanism of quenching is unclear. Dynamic quenching of MCH was also observed by water and n‐propanol. These results suggest that alkane fluorescence from biopolymers, if observable, will only occur from regions of the macromolecules that are not exposed to water.
Phospholipases Induce Melanogenesis in Organ‐Cultured Skin
Authors: Maeda* Kazuhisa , Tomita Yasushi , Naganuma Masako , Tagaml Hachiro 
Published: January 2008

AbstractGuinea pig skin becomes more pigmented following exposure to UV rays. This melanization was accompanied by enhanced intensity of tyrosinase‐staining and increased number of tyrosinase‐positive melanocytes (MELty+), with resultant enhancement of melanin synthesis. To clarify the regulatory mechanism for melanization following UV irradiation, organ‐cultured guinea pig skins have been used to examine their melanogenic responses to exogenous stimulation. This organ culture system responded well to UV irradiation, by increasing melanogenic activity. Also, in this system, phospholipases (PL), arachidonic acid, interleukin‐1α and melanocytestimulating hormone, but not endothelin‐1 or phosphatidylinositol‐specific PLC (PI‐PLC), stimulated melanogenesis to various extents as indicated by the number of MELty+ and morphological changes. Among them, the PLA2 and PLD were found to have a potent stimulatory property for melanocytes. They might affect melanocytes directly or indirectly through an effect on keratinocytes. These results suggest that PLA2 and PLD play a key role in epidermal hyperpigmentation after UV irradiation or inflammation.