摘要:

AbstractVisible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n‐CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short‐circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar ene

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08420.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLaser photolysis techniques have been used to measure the reactivity of benzophenone triplet (BZP) toward various fatty acids and two glycerides in benzene solution. Eight compounds varying both in number and in the configuration of olefinic bonds have been examined. It has been found that the rate constant for hydrogen abstraction from these compounds by3BZP may be related to the number of secondary, allylic and doubly allylic hydrogens in each molecule by the equation:kH={0.023[Hsec+ 0.112[Hallylic] + 1.78[Hddoubly allylic]}× 107M‐1

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08421.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA molecule with three stacked zinc‐porphyrin cycles and two basket‐handles has been synthesized and incorporated into a bilayer lipid membrane. Under light excitation and in the presence of redox compounds in the aqueous phases bathing the membrane, this molecule induces a net electron flux across the membrane. The experimental variations of the flux with some external physicochemical parameters are accounted for by a tentative mechanism which relies on the ability of the porphyrin to act as an electron w

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08422.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe nature of the binding of several ruthenium polypyridyl complexes containing 2, 2`‐bipyridine (bipy), 4, 4`‐dimethyl‐2, 2`‐bipyridine (DMB), 1,10‐phenanthroline (phen), 4,7‐diphenyl‐1,10‐phenanthroline(DPP), 2, 2`, 2`‐terpyridine (terpy), 2, 2`‐biquinoline (biq), 1,4,5,8‐tetraazaphen‐anthrene (TAP) and 1,4,5,8,9,12‐hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A‐T)] and poly[d(G‐C)]were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+and Ru(phen)32+, which bind by partial intercalation, also show a strong preference for poly[d(A‐T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)32+which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G‐C)] or CT‐DNA, due to photoredox interaction with guanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)32+is the most efficient sensitiser while uncharged complexes and complexes with very short‐l

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08423.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe quenching of the benzophenone triplet by lysozyme and its constituent amino acids in aqueous solutions have been studied. Native lysozyme quenches the benzophenone triplet with a high rate constant, 4 × 109M‐1s‐1. The quenching process takes place with production of significant amounts of free ketyl radicals, φketyl=0.56, but with a very low benzophenone consumption yield (0.022). The consumption yield is considerably smaller than that observed for the free amino acids. This difference can be explained in terms of a dominant back hydrogen transfer to the protein in the disproportionation of the free radicals produced. Reduced and carboxymethylated lysozyme shows a higher quenching rate (7.8 × 109M‐1s‐1) and a larger benzophenone consumption yield (0.07).The deactivation of the benzophenone triplet by the native protein leads to its inactivation, with a quantum yield of 0.01. Tryptophan and arginine residues are destroyed with a quantum yield of 0.01. In the modified enzyme tryosine and methionine groups are als

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08424.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA photochemically induced dynamic nuclear polarisation (photo‐CIDNP) study is presented of the amino acids that are polarisable with a flavin dye. These include derivatives of tryptophan, tyrosine, histidine, methylated lysines and methionine. The influence of pH, concentration and chemical modification on the magnitude of the CIDNP effect has been studied to obtain mechanistic information about the radical pair formation.The pH and concentration dependence of tyrosine and tryptophan polarisation could be accounted for quantitatively. The CIDNP evidence indicates that hydrogen‐atom abstraction is important in generating radical pairs in the case of histidine and tyrosine, while electron transfer prevails in the case of tryptophan, the methylated lysines and methion

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08425.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractBiophysical and photobiological properties of two benzoporphyrin derivatives were examined. These dyes exhibit substantial absorbance in the red, and are potent photosensitizersin vitro.After brief (0.5 h) incubations, phototoxicity was more closely correlated with membrane than with mitochondrial photodamage. Affinity of these dyes toward plasma lipoproteins are consistent with a mode of localization via the LDL‐mediated mechanism utilized by the hematoporphyrin‐derived product,

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08426.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe fluorescence emission spectra from human bronchial mucosa and tumors, before and after injection of dihematoporphyrin ether/ester, have been measured with an optical multichannel analyzer from 500 to 750 nm. Fluorescence was excited with a violet krypton ion laser (average wavelength 410 nm). The autofluorescence spectra decrease monotonically with increasing wavelength except for a small broad peak near 600 nm. The spectra from tumor sites, after injection of the fluorescent porphyrin, exhibit the characteristic fluorescence emission at 630 and 690 nm, added to the autofluorescence spectrum. The spectra from control or nontumor sites are similar but the magnitude of the component due to the injected porphyrin is smaller than at a tumor site. The magnitude ratio of tumor to control site fluorescence depends on concentration of the porphyrin, tumor thickness, and time after injection. Autofluorescence degrades contrast and thus makes very thin tumors difficult to image. Subtraction of the autofluorescence background is desirable.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08427.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe cellular photosensitivity caused by aluminum phthalocyanines sulfonated to different degrees (AlPcSn) has been investigated. The phototoxic effect increased with decreasing number of sulfonate groups on the macrocycle, with the exception of AlPcS, which was less phototoxic than AlPcS2but more phototoxic than AlPcS, and AlPcS4. The tendency of the AlPcSns to aggregate in our cellular system increased with increasing lipophilicity of the sensitizers. The aggregates had little or no photosensitizing activity. The low efficiency of cell inactivation caused by AlPcS1can be explained by the highly aggregated state of this sensitizer in the cells. AlPcS2and AlPcS3induced a lower degree of cell inactivation per fluorescing quantum and per quantum absorbed by monomeric species than did AlPcS, and AlPcS,. AlPcS4and AlPcS3are therefore suggested to be in different intracellular locations than AlPcS2and AlPcS1.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08428.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe efficiency of RNA‐protein crosslink and RNA chain break formation under nanosecond or picosecond UV‐laser pulse irradiation of tobacco mosaic virus was determined. It was found that on high‐intensity UV‐laser irradiation the quantum yields of both reactions increase considerably as compared to the usual (low‐intensity) UV‐irradiation. The RNA‐protein crosslink quantum yield was found to be 1.8 × 10‐5and 1.2 × 10‐4and that of RNA chain breaks 1.7 × 10‐4and 8.9 × 10‐4for nanosecond and picosecond

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1989.tb08429.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY