Molecular weight of DNA from coliphage T7 by electron microscopy

Misra, D.N.; Sinha, Rangana; Gupta, Nandini

doi:10.1016/0042-6822(69)90038-5

Cited by 13 publications

(4 citation statements)

References 21 publications

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“…optics (Beckman Model E). The sedimentation constant, S°~0,w was 32.0, in good agreement with previous measurements (Misra et al 1969).…”

Section: Preparation Of Specimenssupporting

confidence: 81%

“…Freifelder (1966 b) has pointed out the advantages of working with DNA of initially homogeneous molecular size, when simple sedimentation analysis provides all the information required. DNA of bacteriophage T7 with a molecular weight of about 25 × 106 Daltons (Misra, Sinha andDas Gupta 1969, Leighton andRubenstein 1969) was used; for DNA molecules of this comparatively small size, problems of mechanical degradation in handling the material are largely eliminated. However, some preliminary work was done with calfthymus DNA at track-segment LET's of 22 and 55 keV//,, using light scattering and sedimentation analysis.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Radiation Quality and Oxygen on Strand Breakage in Dry DNA

Neary¹,

Simpson‐Gildemeister

Peacocke³

1970

International Journal of Radiation Biology and Related Studies

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DNA isolated from T7 phage or deposits of this phage were irradiated with various qualities of radiation, including track-segment irradiations by charged heavy particles. The amount of single-and double-strand breakage was determined by analysis of the sedimentation boundary in an analytical ultracentrifuge. The results show that(1) a single-strand break is produced on average for each energy-loss event in the DNA molecule (2) an energy-loss event has a chance of about 1 in 20 of producing a doublestrand break, with little dependence on LET in the range up to 100 keV//zm (3) there is no significant effect of oxygen on the production of either singleor double-strand breaks.

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“…optics (Beckman Model E). The sedimentation constant, S°~0,w was 32.0, in good agreement with previous measurements (Misra et al 1969).…”

Section: Preparation Of Specimenssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

The Influence of Radiation Quality and Oxygen on Strand Breakage in Dry DNA

Neary¹,

Simpson‐Gildemeister

Peacocke³

1970

International Journal of Radiation Biology and Related Studies

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“…Similar discrepancies have been observed by using these two methods for determining the molecular weight of coliphage T7 DNA (21) and for other adenovirus DNA species (12). This discrepancy may be associated with the use of ammonium acetate in concentrations of 0.1 M or greater as the hypophase for electron microscopy (21).…”

Section: Discussionsupporting

confidence: 61%

Studies of Nondefective Adenovirus 2-Simian Virus 40 Hybrid Viruses III. Base Composition, Molecular Weight, and Conformation of the Ad2 ⁺ ND ₁ Genome

Crumpacker

Henry

Kakefuda

et al. 1971

J Virol

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The nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2+ND,, differs from the defective Ad-SV40 hybrid populations previously described, in that this hybrid virus can replicate without the aid of nonhybrid adenovirus helper. Consequently, the deoxyribonucleic acid (DNA) from this virus, which can be obtained free of nonhybrid adenovirus DNA, is well suited for biophysical studies on Ad-SV40 hybrid DNA. Such studies have been performed and demonstrate Ad2+ND1 DNA to have a buoyant density (1.715 g/cm3) and thermal denaturation profile (T,,, = 75.1 C) almost identical with nonhybrid Ad2 DNA. Furthermore, its molecular weight, as determined by analytical zone sedimentation and electron microscopy, was 22 X 106 to 25 X 106 daltons, which is also very similar to that determined for Ad2. Electron micrographs showed all of the hybrid molecules to be double-stranded and linear. By using this determination of the molecular weight of Ad2+ND1 DNA and assuming that 1 of this molecule consists of covalently linked SV40 DNA (see companion paper), we calculate that the hybrid DNA molecule contains 220 x 103 to 250 x 103 daltons of SV40 DNA, or the equivalent of one-tenth of the SV40 genome.

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“…Contamination of phages either by foreign proteins or by DNA may easily be detected by determining their absorbance ratios at 260/280 nm. Pure phage give ratios of approximately 1.30, whereas pure DNA or phages disrupted by osmotic shock have an absorbance ratio of approximately 1.8 (4,7,17). Phages purified by differential centrifugation gave absorbance ratios of approximately 1.30 (Table 3).…”

Section: Efficiency Of the Various Methods A Compari-mentioning

confidence: 99%