摘要:

Abstract—Ubiquinone Q‐8 inEscherichia coliB was labeled by growing the bacteria in a synthetic growth medium containingp‐hydroxybenzoic acid‐14C(U). The cells were then irradiated with light of wavelengths 313, 334, 366, and 405 nm, and Q‐8‐14C was extracted and assayed. Q‐8‐14C was also isolated from unirradiated bacteria, partially purified, and then irradiated similarly in hexane and assayed. Ubiquinone in the cells was four to eight times as resistant to radiation as ubiquinone in hexane. From 313 to 366 nm, thein vivoandin vitroaction spectra were similar to each other and to the absorption spectra of synthetic Q‐8 dissolved in hexane or ethanol, but at 405 nm the action spectra deviated from the absorption spectra. Quantum yields for the modification (loss) of ubiquinone in hexane decreased from 0·021. at 313 nm to 0·005 at 405 nm.The chromenol of Q‐8 was not detected in labeled cells irradiated at 334 nm, but several more‐polar photoproducts were separated by th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06519.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Problems of absolute measurement of the dose rate of ultraviolet radiation of germicidal lamps in energetic units were studied. Irradiance at 254 nm generated by three different Pen Ray SC‐1 low‐pressure mercury lamps was measured independently in different laboratories using different instruments: (a) Westinghouse SM‐600 Meter, (b) General Electric Germicidal Meter, and (c) large‐surface thermopile with a Bäckström filter. These lamps were then used as secondary standards of absolute irradiance at wavelength 254 nm and compared with the Latarjet dosimeter and the International Light IL‐254 Germicidal Photometer. Mutual agreement of calibration coefficients of three calibrated Pen Ray SC‐1 lamps was roughly within ±5 per cent error. This calibration uncertainty indicates limits of the usefulness of Pen Ray lamps as standards. A direct radiometric calibration using an FT‐16 Schwarz‐Hilger vacuum thermopile, with interference filter NB‐254 or UVR‐250, was in agreement with the above comparison. On the basis of above radiometric calibration absolute D37lethal doses were determined equaling 2·7. J/m2for the bacteriophage T2 and 11·0 J/m2for the bacteriophage φX‐174, the values being read fro

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06520.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Binding of cardiolipin to ferrocytochromec, to form a 4:1 molar complex, results in an approximately sixfold increase of the tryptophan fluorescence emission. Furthermore, appreciable perturbations of the circular dichroism spectrum occur in the Soret and in the far‐ultraviolet regions. The irradiation of the ferrocytochrome–cardiolipin complex at pH 8·8 with visible light leads to the photooxidative modification of histidine‐18, tyrosine‐48 and methionine‐80. Comparison of the above findings with those concerning unbound ferrocytochromecsuggests that the interaction between cardiolipin and ferrocytochromecprovokes a perturbation of the protein conformation, which possibly involves the disruption of the hydrogen bonds linking the aromatic rings of tryptophan‐59 and tyrosine‐48 with one propionic side c

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06521.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—A Stark effect is observed in the rotational fine structure of the 0–0 band of the lowest π*π state of indole. This yields a dipole moment change |ΔμA| = 0·14±0·05.D.Evidence is presented which indicates that the sign of ΔμAis positive. An increase of dipole moment on excitation is in agreement with the value (+ 0·06D) corresponding to the previously calculated orbitals of Song and Kurtin. The direction of the transition moment, calculated from the results of rotational analysis published by Mani and Lombardi, is found to be 26° from the m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06522.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Fluorescence lifetimes, quantum yields and polarization spectra were measured for indole, 3‐methylindole and 2,3‐dimethylindole in non‐polar solvents. The results indicate simultaneous emission from thermally equilibrated1Laand1Lblevels, with1La→1Adominating the 2,3‐dimethylindole emission, and1Lb→1Adominating the indole emission. These results are consistent with previous assignments of the 0‐0 transitions in absorption for these compounds. Radiative rates are:1La→1A, 2·0 × 108S‐1and1Lb→1A. 0·62 → 108S‐1. In addition, the temperature dependence of the excitation and emission spectra are presented, which show that aggregation occurs with these indoles in hydrocarbons below approximately ‐ 110°C. Possible applications to tryptophyl emission in the hydrophobic interiors of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06523.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—N‘‐methylnicotinamide chloride has been investigated as a quencher of the intrinsic fluorescence of tryptophyl residues in proteins. Quenching of the tryptophyl fluorescence (excitation at 305 nm) of model compounds and a select group of proteins provide evidence for a mechanism that follows the classical Stern‐Volmer relation. The apparent number of exposed tryptophyl residues was obtained in 6Mguanidine hydrochloride and aqueous solution at constant pH. Evidence that quenching occurs predominantly by a collisional mechanism was obtained by comparing the equilibrium constant of the non‐fluorescent static state with the much larger quenching constant of the exci

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06524.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Much of the experimental data in the phytochrome literature has been obtained using a small‐molecular‐weight protein fragment. Hence, several properties of phototransformation were re‐examined using large‐molecular‐weight rye phytochrome. The kinetics of phototransformation are first‐order, both for the conversion of Pr to Pfr and for the reverse reaction. The quantum yield of phototransformation was found to be 0·28 mol Einstein‐1for the conversion of Pr to Pfr and 0·20 mol Einstein‐1for the conversion of Pfr to Pr. Intermediates in phototransformation were measured by cycling the pigment with high‐intensity mixed red and far–red light. The difference spectrum of these intermediates between 367 and 575 nm was found to be similar to that previously reported for oat and pea phytochrome. Analysis of intermediate decay indicated complex kinetics and not a single first‐order species. Transient absorbancy changes in the blue region of the spectrum upon actinic illumination could be attributed to differential rates of initial bleaching of the two forms of the pigment and a consequent alteration in the proportion of the two forms in the mixture until photostationary equi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06525.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06526.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06527.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06528.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY