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Exchange of counterions in DNA condensation
Author(s) -
Murayama Yoshihiro,
Sano Masaki
Publication year - 2005
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20243
Subject(s) - chemistry , counterion , condensation , counterion condensation , dna , dna condensation , chemical physics , organic chemistry , thermodynamics , ion , biochemistry , transfection , physics , gene
We measured the fluorescence intensity of DNA‐bound fluorescent dyes YO‐PRO‐1 (oxazole yellow) and YOYO‐1 (dimer of oxazole yellow) at various spermidine concentrations to determine how counterions on DNA are exchanged in the process of DNA condensation. A decrease of fluorescence intensity was observed with an increase of spermidine. Considering the chemical equilibrium under the competition between the dye and spermidine for counterion condensation on DNA, the theoretical curve well describes the decrease of the fluorescence intensity. These results indicate that dyes are exchanged for spermidine at the binding site on DNA; that is, the exchange of counterions occurs. The parameters associated with the decrease of the fluorescence intensity show that the relative affinity of the dye and spermidine for DNA depends on the state of DNA. Moreover, YOYO‐1 prevents the DNA condensation, but the effect of YO‐PRO‐1 on the condensation is very slight, though both dyes intercalate for DNA; the high affinity of YOYO‐1 compared to YO‐PRO‐1 enables prevention of the condensation. © 2005 Wiley Periodicals, Inc. Biopolymers 77: 354–360, 2005