Renaturation of condensed DNA studied through a decoupling scheme
✍ Scribed by Isabelle Chaperon; Jean-Louis Sikorav
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1998
- Tongue
- English
- Weight
- 73 KB
- Volume
- 46
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Rapid Communications
of charge 3/ or greater [such as the polyamines spermidine (3/) and spermine (4/), or the inorganic cation cobalthexamine (3/)]. DNA condensation can lead to the collapse (a coil to globule transition) of long chains at very low concentrations. Under most experimental conditions, however, a multimolecular aggregation is also observed. Aggregation is as a result a convenient way to monitor the condensation of double-stranded DNA. 9 According to Ref. 7, DNA renaturation under standard conditions (in the presence of 1M NaCl at 68ЊC, about 25ЊC below the melting temperature) occurs in good solvent conditions for both single-stranded and doublestranded DNA molecules (ᕄ r ᕃ ).
In contrast, DNA renaturation in the presence of condensing agents is thought to involve a coupling between two transitions, the condensation of single-stranded DNA molecules (ᕄ r ᕅ ) and the renaturation of condensed single-stranded DNA (ᕅ r ᕆ). These two transitions can be decoupled by using single-stranded DNA molecules in the absence of their complementary strands. A similar decoupling scheme has been used to study the DNA renaturation and the strand exchange reaction promoted by RecA protein, 10,11 but a more general applicability of this simple scheme has apparently gone unnoticed. This scheme allows (1) the study of the transition ᕄ r ᕅ alone, and (2) the study of the correlation between the condensation state of single-stranded DNA molecules and the renaturation rate determined in the same solvent conditions. We report here an experimental illustration of this approach using the tetravalent cation spermine as a single-stranded DNA condensing agent.