title: Highly Concentrated Ethanol Solutions: Good Solvents for DNA as Revealed by Single-Molecule Observation.
abstract: We observed single DNA molecules at different ethanol concentrations by using fluorescence microscopy. Large single DNA molecules undergo reentrant conformational transitions from elongated coil into folded globule and then into elongated coil state, accompanied by the increase of the concentration of ethanol in a low-salt aqueous environment. The second transition from globule into the coil state occurs at around 70 % (v/v) ethanol. From circular dichroism (CD) measurements, it is confirmed that the reentrant transition of the higher order structure proceeds together with the transitions of the secondary structure from B to C and, then, from C to A in a cooperative manner. The determined mechanism of the reentrant transition is discussed in relation to the unique characteristics of solutions with higher ethanol content, for which clathrate-like nanostructures of alcohol molecules are generated in the surrounding water.
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Oda
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Sadakane
authors.affiliation: Research Organization of Science and Technology, Ritsumeikan University, Nogihigashi, Kusatsu, Shiga, 525-8577, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yoshikawa
authors.affiliation: Research Organization of Science and Technology, Ritsumeikan University, Nogihigashi, Kusatsu, Shiga, 525-8577, Japan.
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Imanaka
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cyo, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan.
authors.forename: Kingo
authors.initials: K
authors.lastname: Takiguchi
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cyo, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kenmotsu
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan. keyoshik@mail.doshisha.ac.jp.
authors.forename: Kenichi
authors.identifier: http://orcid.org/0000-0002-2751-7136
authors.initials: K
authors.lastname: Yoshikawa
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D009690:Nucleic Acid Conformation; D012997:Solvents / Q000737:chemistry*
chemical_list: D012997:Solvents; D000431:Ethanol; D004247:DNA
keywords: DNA structures; ethanol precipitation; phase transitions; single-molecule studies; water nanoclusters