Influence of supercoiling on DNA structure: Laser Raman spectroscopy of the plasmid pBR322

✍ Scribed by Henk Vasmel

• Publisher: Wiley (John Wiley & Sons)
• Year: 1985
• Tongue: English
• Weight: 435 KB
• Volume: 24
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360240607

✦ Synopsis

We report high-resolution Raman spectra obtained from the circularly closed doublestranded DNA (Form I) of the plasmid pBR322 and from its corresponding linear form (Form 111). Comparison of the Raman spectra of the two forms demonstrates that, at a superhelical density (cr) of -0.069, which is of the same order as those found for most naturally occurring circularly closed DNAs, no major structural transitions occur under the influence of supercoiling. It is shown that at least 98% of all bases are fully basepaired, and that the conformation of the sugar-phosphate backbone is essentially identical to that of linear DNA. Thus, the structural influence of supercoiling, under these conditions, is confined to minor stretches of the plasmid DNA.