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Chemphyschem. 2016 Feb 16;17(4):471-3. doi: 10.1002/cphc.201500988. Epub 2016 Jan 13.

Highly Concentrated Ethanol Solutions: Good Solvents for DNA as Revealed by Single-Molecule Observation.

Author information

1
Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan.
2
Research Organization of Science and Technology, Ritsumeikan University, Nogihigashi, Kusatsu, Shiga, 525-8577, Japan.
3
Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cyo, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan.
4
Faculty of Life and Medical Sciences, Doshisha University, Tatara, Miyakotani, Kyotanabe, Kyoto, 610-0321, Japan. keyoshik@mail.doshisha.ac.jp.

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.

KEYWORDS:

DNA structures; ethanol precipitation; phase transitions; single-molecule studies; water nanoclusters

PMID:
26891092
PMCID:
PMC4770436
DOI:
10.1002/cphc.201500988
[Indexed for MEDLINE]
Free PMC Article

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