摘要:

Abstract.Various S‐RNA's fromE. colishow wide differences in sensitivity to ultraviolet (u.v.) radiation as measured by their amino acid acceptor capacities. S‐RNA for valine is least sensitive and phenylalanine and lysine are most sensitive. S‐RNA's for valine, isoleucine, glycine, aspartic acid, serine, and arginine give exponential type dose‐effect curves. Those for alanine, glutamic acid, lysine, and phenylalanine are rapidly inactivated at low doses and only at higher doses give exponential type inactivation curves having lower slopes than seen at low doses. Penylalanine and glutamic acid S‐RNA inactivated by 2650 or 2804 Å radiations are not reactivated by 2380 Å radiation, indicating that uracil dimers are not involved in the inactivation process. Heating of irradiated S‐RNA to bring about rehydration of uracil residues is not effective in restoring acceptor activity of phenylalanine and leucine S‐RNA. Melting curve experiments suggest that photochemical products other than uracil diniers and hydrated uracil residues are formed and result in changes in the secondary str

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07857.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract.The paper reviews some of the difficulties associated with intercomparing the performances of different types of radiation detector, and discusses the best form of figure of merit to apply to a wide variety of detector types. A table gives current data on the best performance achieved by twenty‐five basic types of radiation detector. in terms of spectral response, usable frequency range, spatial resolution (where appropriate) and sensitivity. Sensitivity is listed under two headings: the minimum detectable signal, expressed in fundamental units (watts, watt cm‐3, joules or joules cm‐2); and the output sensitivity, which indicates the kind and magnitude of output, and which is accordingly expressed in practical units. Source references are given to cover all detector types l

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07858.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—Flash photoreduction of FMN, in aqueous solutions (pH 5–9) leads to the semiquinone (FMNH or FMN). The yield of semiquinone was determined by measuring the amount of leuco‐FMN (FMNH2or FMNH‐) formed in the subsequent disproportionation. The absorption spectrum of the semiquinone, previously known in relative units, has been converted to an absolute basis. Revised values are given for the protolysis constant for FMNH, for the disproportionation rate, and for the formation constantKF. It is found thatKFis much lower for the anionic than for the neutral form of the semi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07859.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—Ultraviolet irradiation converts bovine serum albumin (BSA) and rabbit serum albumin (RS A) into forms much more rapidly hydrolysed by trypsin than the original proteins. The radiation energy (at 2537Å) required to be absorbed by each mg of a protein to convert half of it into a form susceptible to trypsin (E50%) is about 0.32 J for BSA and 0.62 J for RSA. The averageE50% for inactivation of enzymes and antibodies is 0.7 J so the two processes may depend on similar alterations in irradiated protein molecules. The alteration can be considered as denaturation, with protein molecules becoming at least partially unfolded and making the sites susceptible to the attack by trypsin more easily accessible to the enzy

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07860.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract.Flash photolytic experiments with suspensions of rod particles isolated from cattle eyes reveal that at low temperatures a transient is formed following irradiation which preceeds lumirhodopsin in the bleaching process. Kinetic studies, in the range ‐75°C to ‐50°C, suggest that the transient is composed of three intermediate species, having similar absorption spectra but changing to lumirhodopsin at different rates. The energies of activation of the decay reactions appear to be identical and equal 12.5°3 kcal/mole. Spectrophotometric experiments have demonstrated that the low temperature transient is stable at liquid nitrogen temperatures and suggest that it can be reversibly converted to a mixture of rhodopsin and isorhodopsin at ‐195°C.A detailed comparison of light initiated reactions of rhodopsin in rod particle suspensions and in solutions reveals striking similarity in the tw

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07861.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07862.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract.The lethal response of six strains of protozoa to both ionizing radiation and u.v. light has been established. Values have been determined by observation of isolated animals and death was considered to be failure of irradiated individuals to produce unlimited progeny regardless of the actual time of death following irradiation. The strains were selected to give a large variety of size. Lethal doses of u.v. radiation have been determined in the same units used for ionizing radiation (the rad). The results reported here have been supplimented by values from the literature and plotted in the form of a graph of LD‐50 value versus individual organism siz

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07863.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract.ESR measurements on 9, 10‐diphenylanthrace in solution show that the molecule is non‐planar, the two phenyl rings being twisted by about 66° relative to the anthracene nucleus. This agrees with previous predictions made on the basis of scale models.Evidence from absorption and fluorescence spectra for a change of angle between ground and excited state is examined, and a decrease of about 6° is found for the excited state. On the basis of the large angle of twist possible reasons are suggested for the difference between anthracene and 9, 10‐diphenylanthracne with regard to dimer formation and quantum yield of fluorescence in s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07864.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07865.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb07866.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY