ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02618.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The nematicidal compounds, 5‐methyl‐2,2′dithienyl, 5‐phenyl‐2,2′‐dithienyl and 5,5′‐dichloro‐2,2′‐dithienyl, generate singlet oxygen upon photoactivation with near‐UV light. Two chloro‐substituted dithienylethenes have similar properties that are farless efficient. The nematodeAphelenchus avenaewas rapidly killed by the photoactivated dithienyls under aerobic but not under anaerobic conditions,indicating that nematicidal activity of these compounds is related to their sensitizing properties. Furthermore,these nematodes did not expire in the presence of these compounds maintained in the dark. Sensitizing properties were studied by following the inhibition ofglucose–6‐phosphate dehydrogenase by the photoactivated compounds and protection of enzyme activity by various additions. Only singlet oxygen quenchers were effective. The enzyme was inactivated 3 to 4 times faster in D20 compared to H20.Bleaching of p‐nitrosodimethylaniline in the presence of imidazole and the dithiophenes and a specific reaction with the olefin adamantylideneadamantane were additional evidence of generation of singlet oxy

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02619.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Emission spectra of poly[2‐(4‐N,N‐dimethylaminobenzyl)‐2‐(l‐pyrenylmethyl)ethyl methacryl‐ate] (I) and the copolymers with vinyl‐benzyltriethylammonium chloride (II) or sodium p‐styrenesulfo‐nate (III) were studied in extremely polar media such as dimethylformamide (DMF) and water. While the emission by the monomer model compound (2‐(4‐N,N‐dimethylaminobenzyl)‐2‐(l‐pyrenylmethyl)‐ethyl isobutyrate(IV)) scarcely showed exciplex emission in DMF or aqueous DMF, exciplex by I was clearly observed in the same solvents. Furthermore, the ratio of exciplex intensity (Fe) to monomer intensity (Fm) increased by the addition of water to the DMF solution up to 60 vol%. This abnormal spectral behavior of increasing exciplex emission intensity with solvent polarity was interpreted as being due to shrinking of polymer chain. The peaking wavelength of exciplex shifted towards blue in the presence of water, indicating that the solvation of exciplex was hindered and/or the hydrophobic domain was organized. This interpretation was supported by the exciplex emission of II in water. No exciplex was detected from III in water. This is the first example of exciplex emission in homogeneous aqueous solution. In comparison with the published results of micellar systems, the exciplex emission of the polycation indicated that the hydrophobic domain in the polycation was so strong that the solvation of exciplex was considerably hindered. The peaking wavelength of exciplex at 480 nm also lends support to the prese

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02620.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The mechanism of photodecomposition of nucleic acid bases in a neutral aqueous solution upon two‐step excitation of high‐lying electronic states by a powerful laser UV radiation is discussed. Experimental dependences of photodecomposition efficiency versus UV radiation intensity are measured both under picosecond and nanosecond laser UV irradiations. By comparison of experimental dependences with a theoretical model, we obtain some characteristics of excited states, such as lifetime t1of the first electronic excited state S1intersystem crossing yield φ, photosensitivity from an intermediate excited state and others for all five nucleic acid

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02621.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The spectra have been measured of the transient species formed in the nanosecond flash photolysis of aqueous solutions of sulphacetamide under a variety of conditions. In addition to the excited triplet state, the cation radical and the solvated electron were observed. The ionisation of aqueous sulphacetamide was found to occur by a biphotonic process. The extinction coefficient of the cation radical of sulphacetamide was determined by both laser flash photolysis and pulse radiolysis techniques, a value of 1.9 times 103dm3mol‐1cm‐1being obtained. The rate of electron reaction with sulphacetamide and the anion radical spectrum were also determined by the two techniques, good agreement being obtained. The spectrum of the product of the reaction of the superoxide anion radical and the corresponding rate constant have also been determined. A possible mechanism of photosensitized skin reaction due to sulphacetamide is disc

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02622.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Solutions of human serum albumin(HSA) monomer were irradiated with UV light(360 nm) in the presence of [14C]‐3,3.4′S‐tetrachlorosalicylanilide([14C]‐T4CS).The [14C]‐T4CS‐labeiled HSA was cleaved by cyanogen bromide and separated into two fractions. These fractions were reduced carboxymethylated and separated into their seven characteristic peptides and monitored for radioactivity. Tetrachlorosalicylanilide was found to bind mainly to one region of the sequence of HSA and this covalent binding site was located in residues 124 (Cys) to 298 (Met) of the molecule. The binding of 3,5‐dichlorosalicylamido‐4‐(2,2,6.6‐tetramethylpiperidine‐l‐oxyl (DCS‐TEMPO),a spin‐label analogue of T4CS, to HSA was studied by electron spin resonance spectroscopy. In the absence of UV light. DCS‐TEMPO bound non‐covalently(k =6.1 times 106M1) to one major binding site on HSA. These results are evidence for the existence of a major strong binding site for the pho

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02623.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—At low fluence rates it is possible to observe a photoequilibrium between Z,Z‐bilirubin(BR) and itsEisomers(collectively called PBR) bound to human serum albumin(HSA).For excitation centered at 465 nm, the fraction of PBR/HSA in the photoequilibrium mixture was observed to be 0.22 + 0.02. The quantum yield for conversion of BR/HSA to PBR/HSA was found to be 0.20 0.02. The equality of the quantum yield value and the fraction of PBR/HSA in the photoequilibrium mixture is consistent with a simple mechanism for the photoisomerization in which optically excited singlet states of BR and PBR convert rapidly and with virtually total efficiency to a common excited intermediate with twisted geometry that subsequently decays to BR and PBR in the ratio 4:1, respectively. Quantum yields for other photoprocesses of BR bound to HSA are much lower than that for configur‐ational isomerization. The central role suggested for configurational isomerization in the phototherapy for neonatal hyperbilirubinemia is supported by these observa

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02624.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—We have been developing a solar cell using the photochemistry of photosystem 1 particles and flavin mononucleotide. We have studied the effect of changing various parameters including the nature of the electron donor, its redox poise, the pH of the medium and the salt concentration. When we put all of the improvements together, we obtain 1900 μW of power (2.4 W/m2),15 mA short circuit current,and an open circuit potential of 640 mV. The maximum power conversion efficiency was 1%. Several light‐dark cycles could be observed. One of the important properties of this cell is that it can store energy in the form of chemical poten

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02625.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—In order to study energy transfer to zinc tetraphenylporphyrin (ZnTPP) in micellar solution, a series of surface active agents of sodium N‐alkyl carbazole sulfonate, were synthesized. The energy transfer efficiency from the carbazole group near the surface to ZnTPP located in the core of sodium lauryl sulfate (NaLS) micelles was found to be 30%, as observed through the fluorescence of ZnTPP. The critical micelle concentrations (CMC) of the sodium N‐alkyl carbazole sulfonate surfactants, determined by scattering, were 2 times 10‐4M, 3 times 10‐5Mand 3 times 10‐6M, respectively, for alkyl: octyl, dodecyl and hexadecyl. The sensitivity of the CMC of NaLS to the presence of foreign surfactants and solubilizates was also i

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02626.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Exposure of stationary‐phase human breast carcinoma(T–47D) cells to far‐UV light (254 nm) inhibited the appearance of induced ornithine decarboxylase (ODC) activity. The fluence response curve had a shoulder (D4= 2 J m‐2) followed by an exponential decline (D0= 4.2 Jm‐2). The cells could recover from this inhibition when the stimulus of induction of ODC was delayed for20–24 h after irradiation. Hydroxyurea (HU) when present at 3 mM during the recovery period eliminated completely the ability of the cells to recover. This effect of HU on ODC induction was partially reversed by 50nMof the four deoxyribonucleosides required for DNA synthesis. Neither HU nor the deoxyribonucleosides by themselves affected ODC induction in unirradiated cells. Since HU inhibited the recovery from potentially lethal UV damage and is a known inhibitor of excision repair, we interpret the above results to mean that recovery from UV‐induced inhibition of ODC induction depends on excision‐repair of DNA damage. This interpretation is strongly supported by the finding that specific photolysis of 5‐bromodeoxyuridine, incorporated into DNA during the recovery period, inhibited recovery of ODC induction from inh

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02627.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY