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Polyamines stabilise DNA folds (1975)

FLINK, IRWIN ; PETTIJOHN, DAVID E.

[s.l.] : Nature Publishing Group

Nature 253 (1975), S. 62-63

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] Fig. 1 Sedimentation of folded and unfolded DNA after various periods of storage. Membrane-free nucleoids labelled with 3H-thymidine were isolated on sucrose gradients containing 1.0 M NaCl and other components' as described in text; peak fractions were pooled and half of the pool was stored at 4 ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/253062a0

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Interactions stabilizing DNA tertiary structure in the Escherichia coli chromosome investigated with ionizing radiation (1977)

Lydersen, Bjorn K. ; Pettijohn, David E.

Springer

Chromosoma 62 (1977), S. 199-215

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ISSN: 1432-0886

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The structure of the bacterial chromosome was investigated after introducing breaks in the DNA with gamma irradiation. It is demonstrated that irradiation of the chromosome in the cell prior to isolation results in partial unfolding of the isolated condensed DNA, while irradiation of the chromosome after it is released from the cell has no demonstrable effect on DNA folding. The results indicate that RNA/DNA interactions which stabilize DNA folds are unstable when breaks are introduced in the DNA prior to isolation of the chromosome. It is suggested that the supercoiled state of the DNA is required for the initial stabilization of some of the critical RNA/DNA interaction in the isolated nucleoid. However, some of these interactions are not affected by irradiation of the cells. Remnant supercoiling in partially relaxed chromosomes containing a limited number of DNA breaks has the same superhelical density as the unirradiated chromosome. This suggests that restraints on rotation of the packaged DNA are formed prior to the physical unwinding which occurs at the sites of the radiation induced DNA breaks. — Analysis of the in vitro irradiated chromosomes shows that there are 100+-30 domains of supercoiling per genome equivalent of DNA. The introduction of up to 50 double-strand breaks per nucleoid does not influence rotor speed effects of the sedimentation coefficient of the chromosome.