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- Jonsson, Mats, 1939, et al.
(författare)
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Orientation of DNA during gel electrophoresis studied with linear dichroism spectroscopy
- 1988
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Ingår i: Biopolymers. - : Wiley. - 0006-3525 .- 1097-0282. ; 27:3, s. 381-414
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Tidskriftsartikel (refereegranskat)abstract
- A method for in situ study of orientation of DNA during gel electrophoresis has been developed. Linear dichroism spectra measured by this phase-modulation technique can sensitively and selectively detect orientation of DNA during electrophoretic migration in gel. [Measurement of “electrophoretic orientation” was first reported in 1985 by B. Åkerman, M. Jonsson, and B. Nordén (1985) (J. Chem. Soc. Chem. Commun. 422–423)]. Restriction fragments of duplex DNA of lengths in the ranges of 300–2319 base pairs (bp) and 4361–23130 bp have been studied in 5% polyacrylamide and 1% agarose gels, respectively. The fragments become preferentially oriented with the DNA helix axis parallel to the migration direction. In agarose the orientation is found to increase sigmoidally, and in polyacrylamide, linearly, with the electric field strength, within the field ranges accessible to measurement (0–40 and 5–40 V/cm, respectively). In both types of gels a considerable increase in orientation with length of DNA was observed. Compared to dipole orientation in electric fields, the electrophoretic orientation is high: orientation factor S = 0.027 in agarose for 23130 bp at 10 V/cm and S = 0.004 in polyacrylamide for 2319 bp at 10 V/cm. In addition to orientation of DNA, the electrophoresis also leads to orientation effects in the gel structure owing to Joule heating. In agarose there is also an effect that is associated with the migrating DNA zones and that produces different orientations of the gel at the front and rear parts of a zone. Evidence is presented that this effect is due to a DNA-induced electroosmotic flow causing a contraction of the gel in the front of the zone and an expansion in the rear. The experimental results on DNA orientation are compared with the reptation theories for gel electrophoresis. The theory of Lumpkin et al. [O. J. Lumpkin, P. Dejardin, and B. H. Zimm (1985) Biopolymers24, 1573–1593] predicts no orientation length dependence, but it does predict a shape of the field dependence that resembles the shape observed in agarose. The theory of Slater and Noolandi [G. W. Slater and J. Noolandi (1986) Biopolymers25, 431–454] predicts an orientational length dependence that is an order of magnitude less than the experimental one, and a field dependence that agrees neither with the sigmoidal shape observed in agarose nor with the linear dependence in polyacrylamide.
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- Kjellstrand, Per, et al.
(författare)
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Effects of organic solvents on motor activity in mice
- 1985
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Ingår i: Toxicology. - 0300-483X. ; 35:1, s. 35-46
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Tidskriftsartikel (refereegranskat)abstract
- Groups of male mice were exposed via inhalation to methylene chloride, perchloroethylene, toluene, trichloroethylene or 1,1,1-trichloroethane. The exposures were started at 2300 h. Generation of vapor was stopped after 1 h. Motor activity of the animals during the exposures was measured with a Doppler radar. Several concentrations of each solvent were tested. Concentrations could be found for all solvents at which they initially increased the motor activity. When the generation of vapor was terminated and the concentration started to decline, a new phase of changes in motor activity was induced. At this phase, motor activity was in most cases influence in the opposite direction to that at the beginning of the exposure. Trichloroethylene concentrations could be found which gave no increase in activity at the start of exposure but a prominent decrease at termination. The lowest concentration at which effects could be seen was different for the different solvents. Perchloroethylene was more and 1,1,1-trichloroethane less potent than the other solvents in inducing motor activity. The time pattern of the motor activity alterations was specific for each solvent. Both the concentration and the rate of the concentration increase were responsible for the effects on motor activity. The differences between the solvents probably reflect differences in their site of action, their distribution and their biotransformation.
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- Nordén, Bengt, 1945, et al.
(författare)
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New Techniques for Aligning Molecules
- 1988
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Ingår i: Polarized spectroscopy of ordered systems; edited by B. Samori' and E.W. Thulstrup (Proceedings of the NATO Advanced Study Institute on New Developments in Polarized Spectroscopy of Ordered Systems, Rimini, Italy, October 11-23, 1987). - 9027727848 ; , s. 197-209
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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