<b>Hydration of Deoxyribonucleic Acid. I. a Gravimetric Study</b>

Falk, Michael; Hartman, K.A.; Lord, R. C.

doi:10.1021/ja00879a012

Cited by 268 publications

(172 citation statements)

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“…In Figure 1 is also shown the early results by Falk et al 14 measured gravimetrically. There is a full agreement between the two methods within the experimental accuracy.…”

Section: Dna Hydration Sorption Isothermmentioning

confidence: 55%

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The Hydration of a DNA−Amphiphile Complex

et al. 2004

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We present measurements of isothermal DNA-hexadecyltrimethylammonium (DNACTA) complex and pure DNA hydration at 25°C 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.

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“…In Figure 1 is also shown the early results by Falk et al 14 measured gravimetrically. There is a full agreement between the two methods within the experimental accuracy.…”

Section: Dna Hydration Sorption Isothermmentioning

confidence: 55%

“…DNA hydration has been extensively studied by several gravimetric, spectroscopic, osmotic stress, calorimetric, and scattering methods. [14][15][16][17][18][19][20][21][22][23][24] However, to our knowledge, simultaneous free energy and enthalpy data have not been reported previously.…”

Section: Discussionmentioning

confidence: 99%

The Hydration of a DNA−Amphiphile Complex

et al. 2004

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“…The collection stress does not seem t o support this theory. An alternative explanation is possible in terms of the formation of hydrates of key biological molecules (Falk, Hartman & Lord, 1962, 1963a, b ; Falk, 1964) with some hydrates being formed in a semi-reversible manner, while another is that enzyme activation may occur at certain RH values. This type of behaviour has been demonstrated (Couper, Eley & Hayward, 1955).…”

Section: The Action Of Protecting Agentsmentioning

confidence: 99%

The Survival of Escherichia coli sprayed into Air and into Nitrogen from Distilled Water and from Solutions of Protecting Agents, as a Function of Relative Humidity

Cox

1966

Journal of General Microbiology

103

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SUMMARYThe survival in air as a function of relative humidity (RH) and aerosol age is reported for Escherichia coli (strains B and Jepp) and for Serratia marcescens (strain U K 8 ) sprayed from suspensions in distilled water and in solutions of dextran and of raffinose. The survival in nitrogen ( > 99.9 yo) of E . coli (strains B, Jepp and commune) is given as a function of RH, when sprayed from suspension in distilled water and in raffinose solution. The results show that E . coli in the aerosol was subject to at least three stresses, an air stress, an RH stress, and a collection stress. The air stress accounted for loss of viability at low RH and the RH stress occured a t high RH and is expressed as RH ranges in which E . coli rapidly lost viability. The survival, especially a t high RH, depended upon the composition of the collecting fluid. At high RH a range of RH was found in which the bacteria were unstable when collected in phosphate buffer. Addition of raffinose (chosen as a typical protecting agent) to the spray fluid and the addition of M-sucrose to the collecting fluid eliminated the instability for E . coli (commune) and decreased it for the other two strains.

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“…one monolayer of water). This latter condition corresponds to equilibration against RH=80% [10] and about 20 water molecules per base pairs [11]. A second sample was then prepared using D 2 O in order to subtract out the incoherent signal from the DNA hydrogen atoms.…”

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confidence: 99%

Experimental evidence of fragile-to-strong dynamic crossover in DNA hydration water

Chen¹,

Liu²,

Chu³

et al. 2006

The Journal of Chemical Physics

116

125

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We used high-resolution quasielastic neutron scattering spectroscopy to study the single-particle dynamics of water molecules on the surface of hydrated DNA samples. Both H2O and D2O hydrated samples were measured. The contribution of scattering from DNA is subtracted out by taking the difference of the signals between the two samples. The measurement was made at a series of temperatures from 270 K down to 185 K. The Relaxing -Cage Model was used to analyze the quasielastic spectra. This allowed us to extract a Q-independent average translational relaxation time τT of water molecules as a function of temperature. We observe clear evidence of a fragileto-strong dynamic crossover (FSC) at TL = 222 ± 2 K by plotting log τT vs. T. The coincidence of the dynamic transition temperature Tc of DNA, signaling the onset of anharmonic molecular motion, and the FSC temperature TL of the hydration water suggests that the change of mobility of the hydration water molecules across TL drives the dynamic transition in DNA. . It was also found, from neutron and Xray scattering, or from Mössbauer spectroscopy, that the measured mean-squared atomic displacement x 2 of the bio-molecules exhibits a sharp rise in the same temperature range [1,2,3,4,5]. This sharp increase in x 2 was taken as a sign for a dynamic transition (or sometimes called glass-transition) in the bio-molecules occurring within this temperature range. In most of these papers, the authors suggest that the transition is due to a strong rise of anharmonicity of the molecular motions above this transition temperature [1]. Later on, it was demonstrated that the dynamic transition can be suppressed in dry bio-molecules [2], or in bio-molecules dissolved in trehalose [5]. Moreover, it can be shifted to a higher temperature for proteins dissolved in glycerol [4]. Thus the dynamic transition can be controlled by changing the surrounding solvent of the bio-molecules. On the other hand, it was found some time ago from Raman scattering that supercooled bulk water has a dynamic crossover transition at 220 K [6], similar to that predicted by Mode-Coupling theory [7]. Approximate coincidence of these two characteristic temperatures, one for the slowing down of bio-chemical activities and the sharp rise in x 2 in bio-molecules and the other for the dynamic crossover in water, suggests a relation between the dynamic transition of bio-molecules and that of their * Author to whom correspondence should be addressed. Electronic mail: sowhsin@mit.edu hydration water [8].Another striking experimental fact is that this dynamic transition temperature, as revealed by change of slope in x 2 vs. temperature plot, occurs at a universal temperature range from 250 to 200 K in all bio-molecules examined so far. This list includes globular proteins, DNAs, and t-RNAs. This feature points to the plausibility that the dynamical transitions are not the intrinsic properties of the bio-molecules themselves but are imposed by the hydration water on their surfaces.However, x 2 (mostly coming from hydroge...

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Hydration of Deoxyribonucleic Acid. I. a Gravimetric Study

Cited by 268 publications

References 1 publication

The Hydration of a DNA−Amphiphile Complex

The Hydration of a DNA−Amphiphile Complex

The Survival of Escherichia coli sprayed into Air and into Nitrogen from Distilled Water and from Solutions of Protecting Agents, as a Function of Relative Humidity

Experimental evidence of fragile-to-strong dynamic crossover in DNA hydration water

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