Intrachain Segregation in Single Giant DNA Molecules Induced by Poly(2-vinylpyrrolidone)

Microsegregation in individual single chains of T4 DNA in solutions of poly(2-vinylpyrrolidone) (PVP) was observed by fluorescent microscopy. After mixing solutions of DNA with PVP, single DNA chains exhibited intrachain segregation with multiple mini-globules connected by narrow flexible chains. The microsegregated form of DNA was observed only in solutions of high-molecular-weight PVP (Mw ∼ 220 000), while in solutions of short chain PVP (Mw ∼ 10 000), only the randomly coiled conformation was found. The average lifetime of microsegregated DNA chains was more than several days while some of the microsegregated DNA molecules changed into a completely collapsed state.