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C S Rupert

Publications and source records attributed to C S Rupert.

At least 37 records · Page 2Linked to original sources
PubMed1978

Identification of a biochemically unique DNA-membrane interaction involving the Escherichia coli origin of replication.

DNA-membrane complexes have been obtained from Escherichia coli by using a freeze-thaw lysis procedure that avoids lysozyme and detergents. Complexes made in this manner and containing DNA near the origin of replication are uniquely sensitive to ionic strength, Pronase, and trypsin. There is approximately one such complex per chromosomal origin. The sensitivities suggest that origin-specific binding is mediated by a protein. By using these unique characteristics to distinguish origin-specific complexes from the majority of DNA-membrane binding sites, it was found that the origin-specific binding persists after termination of chromosomal replication.

Cell Membrane↗
PubMed1978

The biologic effectiveness of ultraviolet light.

The biologic effects of visible and UV light result from photochemical changes in cell components. The amount of photochemical change induced in a small non-self-shadowing structure is proportional to the number of photons traversing it per unit area normal to the direction of propagation, summed over all component beam directions. Within an optically complex, absorbing, and scattering structure, this quantity is difficult to determine, but for skin it is approximately proportional to the total number of photons per unit area entering its outer surface. The magnitude of some photobiologic effects depends on the total amount of photochemical change induced, whereas others depend on the rate of photoproduct formation or on a more complex relation. The nature of the dependence must be determined before light measurements can be related to the magnitude. The effect of a polychromatic illumination depends on its wavelength distribution, weighted by the effectiveness of each wavelength (the action spectrum) under the conditions employed. Until the latter is known, no dosimetric characterization of the light is possible. The wavelength distribution can be determined by spectroradiometric measurement, with the weighting performed numerically, or (more conveniently, though less accurately) by the use of an analog reaction with an action spectrum like that of the photobiologic effect.

Animals↗
PubMed1977

Transitory germinative excision repair in Bacillus subtilis.

Bacillus subtilis strains UVSSP-42-1 (hcr42 ssp1) and UVSSP-1-1 (hcr1 ssp1) are ultraviolet (UV) radiation sensitive both as dormant spores and as vegetative cells. These strains are unable to excise cyclobutane-type dimers from the deoxyribonucleic acid (DNA) of irradiated vegetative cells and fail to remove spore photoproduct from the DNA of irradiated spores either by excision (controlled by gene hcr) or by spore repair (controlled by gene ssp1). When irradiated soon after spore germination, these strains excise dimers, but not spore photoproduct, from their DNA. This process, termed germinative excision repair, functions only transiently in the germination phase and is responsible for the high UV resistance of germinated spores and for their temporary capacity to host cell reactivate irradiated phages infecting them. The recA1 mutation confers higher UV sensitivity to the germinated spores, but does not interfere with dimer removal by germinative excision repair.

Bacillus subtilis↗
PubMed1976

Analaysis of photoenzymatic repair of UV lesions in DNA by single light flashes. XI. Light-induced activation of the yeast photoreactivating enzyme.

Photoreactivating enzyme (PRE) from yeast (as semi-crude extract, or in highly purified form) shows increased activity if it is illuminated with near UV or short wavelength visible light prior to its use for photoenzymatic repair of UV-induced pyrimidine dimers in transforming DNA in vitro. This effect results from an alternation in PRE molecules changing those with low activity in the light-dependent step of the reaction to a higher activity. Light-induced activation of PRE preparations is slowly lost by dark storage for several hours to 1 day (faster at 23 degrees C than at 5 degrees C), but can be recovered repeatedly by renewed preillumination. The action spectrum for these preillumination effects generally resembles that for the photoenzymatic repair reaction itself, having its maximum in the same 355-385 nm region as the latter, but light of somewhat longer wavelengths (546 nm) is still effective. Preilluminated PRE is also more stable to thermal inactivation (65 degrees C) than untreated enzyme.

DNA Repair↗
PubMed1975

Effects of DNA-polymerase-defective and recombination-deficient mutations on the ultraviolet sensitivity of Bacillus subtilis spores.

The DNA of UV-irradiated Bacillus subtilis spores, which contains 5-thyminyl-5,6-dihydrothymine (TDHT) as the major thymine photoproduct, is known to be repaired during germination by two complementary mechanisms: (I) the well-known excision repair, and (2) a special process, "spore repair", which destroys TDHT in situ without rendering it acid-soluble. In the absence of both mechanisms TDHT is not removed, and spores are highly UV-sensitive. When either of two mutations (pol-59 and pol-151) giving defective DNA polymerase, or one (rec-A1) giving a recombination deficiency are introduced into strains defective in one of these known TDHT removal processes, the chemically measured elimination of TDHT from spore DNA is unaltered, but spore UV-sensitivity is increased. The pol mutations produce their greatest sensitivity increase in spores of strains already deficient for the in situ destruction of TDHT, while the rec mutation gives its maximum sensitivity increase to spores of strains lacking excision. These facts argue that the pol mutations interfere mostly with excision repair (presumably its later resynthesis step), shile the rec mutation impairs "spore repair" in some step occurring subsequent to the TDHT destruction in situ. With either of these impairments of the later repair steps, DNA of UV-irradiated and germinated spores is considerably degraded, unless germination is carried out in the presence of chloramphenicol.

Bacillus subtilis↗
PubMed1972

Genetically controlled removal of "spore photoproduct" from deoxyribonucleic acid of ultraviolet-irradiated Bacillus subtilis spores.

Previous genetic analysis indicated that at least two genes determine the ultraviolet (UV) sensitivity of Bacillus subtilis spores. The present study shows that these genes independently control two distinguishable processes for removing UV-induced spore photoproduct (5-thyminyl-5,6-dihydrothymine, or TDHT) from spore deoxyribonucleic acid. The first, is a spore repair mechanism by which TDHT is removed rapidly without appearing in acid-soluble form. This mechanism, which is demonstrated in both UV-resistant and excision-deficient strains, operates to a certain extent during germination without requiring vegetative growth. The second, demonstrated in a mutant which lacks the first mechanism, removes TDHT relatively slowly and only if germinated spores are allowed to develop toward vegetative cells. The latter mechanism appears identical to excision-resynthesis repair, since the mutation abolishing it renders the irradiated vegetative cells incapable of removing cyclobutane-type pyrimidine dimers. Blocking either one of these mechanisms only slightly affects the UV sensitivity of spores, but blocking both prevents TDHT removal and gives high UV sensitivity.

Bacillus subtilis↗