The titratable joint phenomenon in ΦW-14 DNA

✍ Scribed by Jess Wilcoxon; J. Michael Schurr; R. A. J. Warren

• Publisher: Wiley (John Wiley & Sons)
• Year: 1984
• Tongue: English
• Weight: 427 KB
• Volume: 23
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360230415

✦ Synopsis

Dynamic light scattering (DLS) studies are carried out on native @W-14 DNA, which has putrescines covalently attached at the methyl groups of half its thymines, and on a chemically modified form of the same DNA in which the ammonium groups of' its putrescines are almost completely acetylated. From neutrality to pH 9.6, both forms of @W-14 DNA exhibit the same curve of Dapp vs K 2 over the range K 2 = 0.5 X 10'" to K 2 = 20 X 1O1O cm-*, and this coincides with curves that we have ohserved for other DNAs. (D,,,, apparent diffusion coefficient; K , scattering vector). However, when the pH is raised to pH 10.0-10.2, native @W-14 exhibits a spectacular decrease in D,,, at large wave vector. whereas the acetylated form shows no sign of such behavior. It is inferred that bound ammonium groups make an essential contribution to the stabilization of titratable joints. Comparing the pH profiles of the absorbance (A260) for these two DNAs gives some evidence that base unstacking may be involved in titratable joint formation.