A Simple Mechanochemical Method for Studying Structure and Dynamics of Biopolymer Fibers in Various Media.

Rupprecht, A.; Piškur, Jure; Brobakke, Kristin; Carlberg, Georg E.; Sterner, Olov; Wickberg, Börje

doi:10.3891/acta.chem.scand.37b-0863

Cited by 9 publications

(9 citation statements)

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“…We recently found in the literature that variations of DNA fiber length, characteristic of form transitions of DNA, can also be observed in water-ethanol mixtures (Rupprecht and Piskur 1983). In the present approach, precise evaluation of the water content and its variation with the r.h. during conformational changes associated with the A-B and B-C transitions of natural DNA are presented.…”

Section: Introductionmentioning

confidence: 94%

Changes of hydration during conformational transitions of DNA

1990

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Fiber X-ray diffraction and measurement of fiber dimensions yields information about the hydration of DNA in fibers. The results obtained give us the fraction of nucleotides in the B form for the A-B transition or the rate of progression for the B-C transition as functions of the number of water molecules per nucleotide. The present experimental results confirm the importance of cooperativity in the A-B transition and the progressive change of the DNA double helix conformation during the C-B transition. At least twenty additional water molecules per nucleotide are necessary to stabilize the B form for DNA molecules in fibers following the A to B transition whereas only ten are sufficient when the B conformation is obtained starting from the C form.

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Section: Introductionmentioning

confidence: 94%

Changes of hydration during conformational transitions of DNA

1990

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“…This method was early modified for the preparation of a long fiber bundle of oriented DNA molecules from which a large number of reproducible samples could be taken for mechanochemical study [26]. Recently, a simple set-up was suggested for mechanochemical studies of conformational and helix-to-coil transitions in such DNA fiber samples [27,28,29,30]. A DNA fiber was held straight by a small weight in a measuring cylinder containing ethanol-water solution.…”

Section: Use Of Highly Oriented Fibersmentioning

confidence: 99%

Aggregated DNA in ethanol solution

Piškur

Rupprecht

1995

FEBS Letters

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A recently developed mecbanocbemical method has provided a new, efficient tool for studies on the thermal stability and structure of aggregated DNA in ethanol-water solutions. At low ethanol concentrations DNA is fully soluble and is in the B form. However, with increasing ethanol concentration the melting temperature of DNA, T,,,, decreases. At a critical ethanol concentration, dependent on the nature and concentration of the counterion, aggregation of the DNA molecules sets in. This is reflected in a marked increase in T,,, indicating that the aggregated DNA molecules are thermally more stable than the dissolved ones. However, they are still in the B form. In general, T,,, of aggregated DNA also decreases with further increasing ethanol concentration and is dependent on the nature of the counterion, but T,,, is not affected by the concentration of the counterion (excess salt) in the ethanol-water solution. When the ethanol concentration reaches the range of 7040% (v/v), the B-to-A conformational transition occurs in the case of Na-, K-and CsDNA. Above this transition point the A form is more stable than the B form due to the reduced water activity and to increased interhelical interactions. At very high ethanol concentrations, above 85% and dependent on the nature of the counterion, a drastic change in the thermal behaviour is observed. Apparently such a strong interhelical interaction is induced in the aggregated DNA that the DNA is stabilized and cannot adopt a random coil state even at very high temperatures. This stability of DNA in the P form is fully reversed if the ethanol concentration is lowered and the activity of water, thereby, is restored.

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“…This salt concentration was chosen in order to use the same salt concentration as in the mechanochemical study of DNA fibers with various alkali counterions (univalent) (Rupprecht et al, 1994 (Rupprecht and Piskur, 1983;Rupprecht et al, 1994).…”

Section: Methodsmentioning

confidence: 99%

“…This force was assumed to originate from the helix-coil transition of the DNA, thus reflecting the shorter average end-to-end distance in the coil state as compared to the double helical state. To enable measurements of the relative length of DNA fibers in ethanolwater solutions, a simple mechanochemical set-up was constructed (Rupprecht and Piskur, 1983). This set-up is used in the present investigation.…”

Section: Introductionmentioning

confidence: 99%

A mechanochemical study of MgDNA fibers in ethanol-water solutions

Schultz

Rupprecht

Song

et al. 1994

Biophysical Journal

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Highly oriented calf-thymus MgDNA fibers, prepared by a wet spinning method, were studied with a simple mechanochemical set-up. The relative fiber length, L/Lo, was measured with the fibers submerged in ethanol-water solutions. In one type of experiment L/Lo was measured as a function of ethanol concentration at room temperature. No substantial decrease in L/Lo with increasing ethanol concentration was observed, indicating that MgDNA fibers stay in the B form even when the water activity is very low. For low ethanol concentrations the fiber structure is stable and does not dissolve even at very high water activities. In a second type of experiment, the heat-induced helix-coil transition was manifested by a marked contraction of the fibers. The transition temperature decreases linearly with increasing ethanol concentration between 52 and 68% ethanol. At higher ethanol concentrations the helix-coil transition temperature increases due to strong aggregation within the DNA fibers, and above 77% ethanol the fibers do not contract at all, not even at the upper temperature limit of the experiments, approximately 80 degrees C. This behavior is discussed with reference to dried DNA and the P form of DNA. The helix-coil transition temperature of the MgDNA fibers in 70% ethanol does not show any dependence on the MgCl2 concentration. It is shown that the Poisson-Boltzmann cylindrical cell model can account qualitatively for this lack of salt dependence.

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A Simple Mechanochemical Method for Studying Structure and Dynamics of Biopolymer Fibers in Various Media.

Cited by 9 publications

References 0 publications

Changes of hydration during conformational transitions of DNA

Changes of hydration during conformational transitions of DNA

Aggregated DNA in ethanol solution

A mechanochemical study of MgDNA fibers in ethanol-water solutions

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