ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05894.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—This essay, written in honor of Alexander Hollaender's seventieth birthday, reviews the development of the concept of repair of premutational damage at both the biological and molecular levels. It stresses the important hut not exclusive role that repair processes play in determining the mutation yield, with emphasis on mutations induced by ultraviolet radiation. It points out that under special circumstances repair may be sufficiently efficient to almost completely eliminate premutational damag

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05895.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—A history of the photochemistry of the first known virus is presented. Hollaender and Duggar recognized that the virus contains nucleic acid because of the shape of their action spectrum for photoinactivation. An analysis of this spectrum in detail presents a challenge to photochemists because of the combined role of protein and nucleic acid in determining rates of inactivation. At present these rates can not be explained simply on the basis of the photochemistry of each of the constituents; that is, the photochemistry of free infectious nucleic acid differs in several respects from that exhibited by nucleic acid irradiated in intact virus. At present it is believed that pyrimidine hydrate and dimer formations are important, but an explicit solution to the problem is not in sigh

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05896.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Problems of determining action spectra are considered as well as various types of action spectra for U.V. action upon cell activities. U.V. is an effective mutagenic agent producing point mutations and chromosomal changes. U.V. is readily absorbed by superficial layers of cells in tissues; therefore, special experimental procedures are necessary for induction of mutations in animals or plants. U.V. is, however, suitable for mutagenesis in microorganisms because their cells are small, permitting the radiation to reach the nuclei. Action spectrum studies reveal that u.v. mutagenesis results from absorption of the radiation by nucleic acid. The most prominent alteration in DNA following absorption of u.v. is dimerization of pyrimidines, chiefly thymine. Such a change not only retards DNA replication but results in errors (mutations). U.V. mutagenesis therefore depends upon the conditions before, during and after irradiation. Thus immediate post‐treatment with visible and long u.v. light splits pyrimidine dimers, thereby reversing impending u.v. mutagenesis. For cells kept in the dark, conditions which prevent DNA replication by interfering with the metabolism of the cell provide time for dark repair of the DNA lesion and so for reversal of the impending mutat

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05897.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—A method of dosimetry which is useful in analyzing complex photochemical reactions involving more than one photoproduct is described. This involves determining a photochemical cross section for each of the products, σB, σc…., and an absorption cross section σ. for the reacting species. The ratio σB/σais the quantum yield for production of productB. Where a number of photoproducts are produced simultaneously, it is convenient to express ‘dose’ in terms of the average number of photons per cm2‘seen’ by each molecule in the vessel. This average can be calculated from the number of incident photons, the volume of the liquid, the absorbance and the path length. Experimental details of the irradiation facility which is convenient for such studies are presented. The method of dosimetry is illustrated using photochemical data for uracil and orotic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05898.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The design of a typical flash photolysis equipment is considered in detail and the factors limiting the time resolution and the sensitivity are analyzed. The characteristics of low pressure discharge lamps are compared with those of high pressure arcs, of exploding foils and of the electromagnetic ‘pinch’ discharge. For the analytical flash, operating at a much lower power level, many satisfactory designs exist which give a good continuum and short duration. Methods of improving the optical system are discussed, and the special advantages of using a microscope optical system for investigating substances with high extinction coefficients are illustrated by an account of recent work on chloro

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05899.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Lasers have not been applied as widely in chemistry as in physics. However the larger number of laser lines available now, which have higher power, and short pulse duration enhances their application in chemistry and related fields.This paper discusses some of the advantages of lasers over the normal or classical light sources. This description of the applications of lasers in chemistry is not claimed to be complete nor intended to include all of the reported work of laser application in chemistry, but to describe a few applications of lasers in several fields of chemistr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05900.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Techniques and instruments for measuring the luminescence, fluorescence. and phosphorescence of proteins and nucleic acids are described. Emphasis is placed on the principles of the instruments and the procedures which are necessary to measure quantitatively the luminescence from biological macromolecules at 77°K. Examples are given of the effect of denaturation on luminescence of both proteins and nucleic acids. on ways in which the luminescence can be associated with particular constituents, and finally on the influence that electronic energy transfer has on the excitation spectra of protein luminescences. These examples typify the relationship of luminescence spectra to the conformation and constitution of macromolecul

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05901.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—lntermolecular transfer of electronic energy is a powerful tool for obtaining information about excited molecules in solution. Proper application of excitation transfer requires giving careful attention to the spectroscopic properties of the donor and acceptor and accounting for all possible donor‐acceptor interactions of consequence. Water presents no particular difficulties so that electronic energy transfer methods can be applied to the photochemistry of biologically important molecules in aqueous solve

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05902.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY