Advanced

The hydration of a DNA-amphiphile complex

Leal, Cecilia LU ; Wadsö, Lars LU ; Olofsson, Gerd LU ; Miguel, Maria LU and Wennerström, Håkan LU (2004) In The Journal of Physical Chemistry Part B 108(9). p.3044-3050
Abstract
We present measurements of isothermal DNA-hexadecyltrimethylammonium (DNACTA) complex and pure DNA hydration at 25 degreesC using a sorption microcalorimeter. This calorimeter provides simultaneous measurement of (i) water activity (sorption isotherms) and (ii) the partial molar enthalpy of water as a function of water uptake. For pure DNA, hydration is exothermic over the studied concentration range and we find an approximately linear relation between the partial molar enthalpy and the partial molar free energy. A kink in the isotherm appears at 20.0 +/- 0.3 water molecules per base pair for a water activity of 0.80, consistent with A-B transition of the DNA. There is no detectable heat effect associated with this transition. At low water... (More)
We present measurements of isothermal DNA-hexadecyltrimethylammonium (DNACTA) complex and pure DNA hydration at 25 degreesC using a sorption microcalorimeter. This calorimeter provides simultaneous measurement of (i) water activity (sorption isotherms) and (ii) the partial molar enthalpy of water as a function of water uptake. For pure DNA, hydration is exothermic over the studied concentration range and we find an approximately linear relation between the partial molar enthalpy and the partial molar free energy. A kink in the isotherm appears at 20.0 +/- 0.3 water molecules per base pair for a water activity of 0.80, consistent with A-B transition of the DNA. There is no detectable heat effect associated with this transition. At low water contents, the hydration of the DNACTA (1: 1) complex is exothermic as for the pure DNA, but after incorporation of the first 7.0 +/- 0.1 water molecules, the enthalpy changes sign. At 22 water molecules per base pair, the enthalpy levels off to 2.7 +/- 0.2 kJ/mol. In a separate experiment, the swelling limit for the DNACTA complex was found to be 27 +/- 1 waters per base pair. The DNACTA complex is arranged in a hexagonal structure. We propose a model for the DNACTA complex based on the packing of the components in an electroneutral way consisting of six DNA helices, presumably in an A configuration, placed around a central CTA(+) cylinder. The hydration of the complex is seen as a balance between the attractive electrostatic interaction causing the formation of the complex and a repulsive component arising from a hexagonal deformation of CTA(+) cylinders. An important contribution to the partial molar enthalpy of water comes, in this interpretation, from the release of conformational constraints of the CTA ion alkyl chains. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
108
issue
9
pages
3044 - 3050
publisher
The American Chemical Society
external identifiers
  • wos:000220021600042
  • scopus:1542336670
ISSN
1520-5207
DOI
10.1021/jp030850b
language
English
LU publication?
yes
id
b499cf75-4fd4-4347-90c5-3f168e969d0e (old id 153948)
date added to LUP
2007-07-11 15:34:36
date last changed
2017-10-29 04:16:12
@article{b499cf75-4fd4-4347-90c5-3f168e969d0e,
  abstract     = {We present measurements of isothermal DNA-hexadecyltrimethylammonium (DNACTA) complex and pure DNA hydration at 25 degreesC using a sorption microcalorimeter. This calorimeter provides simultaneous measurement of (i) water activity (sorption isotherms) and (ii) the partial molar enthalpy of water as a function of water uptake. For pure DNA, hydration is exothermic over the studied concentration range and we find an approximately linear relation between the partial molar enthalpy and the partial molar free energy. A kink in the isotherm appears at 20.0 +/- 0.3 water molecules per base pair for a water activity of 0.80, consistent with A-B transition of the DNA. There is no detectable heat effect associated with this transition. At low water contents, the hydration of the DNACTA (1: 1) complex is exothermic as for the pure DNA, but after incorporation of the first 7.0 +/- 0.1 water molecules, the enthalpy changes sign. At 22 water molecules per base pair, the enthalpy levels off to 2.7 +/- 0.2 kJ/mol. In a separate experiment, the swelling limit for the DNACTA complex was found to be 27 +/- 1 waters per base pair. The DNACTA complex is arranged in a hexagonal structure. We propose a model for the DNACTA complex based on the packing of the components in an electroneutral way consisting of six DNA helices, presumably in an A configuration, placed around a central CTA(+) cylinder. The hydration of the complex is seen as a balance between the attractive electrostatic interaction causing the formation of the complex and a repulsive component arising from a hexagonal deformation of CTA(+) cylinders. An important contribution to the partial molar enthalpy of water comes, in this interpretation, from the release of conformational constraints of the CTA ion alkyl chains.},
  author       = {Leal, Cecilia and Wadsö, Lars and Olofsson, Gerd and Miguel, Maria and Wennerström, Håkan},
  issn         = {1520-5207},
  language     = {eng},
  number       = {9},
  pages        = {3044--3050},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {The hydration of a DNA-amphiphile complex},
  url          = {http://dx.doi.org/10.1021/jp030850b},
  volume       = {108},
  year         = {2004},
}