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1.
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2.
  • Carlsson, Christina, 1968-, et al. (författare)
  • OPTICAL AND PHOTOPHYSICAL PROPERTIES OF THE OXAZOLE YELLOW DNA PROBES YO AND YOYO
  • 1994
  • Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 98:40, s. 10313-10321
  • Tidskriftsartikel (refereegranskat)abstract
    • The photophysical properties of the optical DNA probe YOYO (homodimeric derivative of oxazole yellow) have been characterized in terms of the monomeric part, the YO chromophore. In aqueous solutions YO is virtually nonfluorescent but upon binding to DNA its fluorescence quantum yield is strongly increased. A similar enhancement of the fluorescence is observed for YO in the viscous solvent glycerol. The high fluorescence quantum yield of YO, when bound to DNA or in a viscous solution, is proposed to be a result of decreased rotational mobility around the internuclear bridge between the two aromatic ring systems. This hypothesis is based on similar values of the activation energies for the temperature-dependent nonradiative decay processes (E(A) = 53 kJ/mol) and viscous flow (E(A) = 63 kJ/mol), suggesting related rate-limiting mechanisms. A single electronic transition is found to be responsible for the intense visible absorption band. This conclusion is based on the observation of an essentially wavelength-independent reduced linear dichroism and similarly wavelength independent fluorescence anisotropy, and the fact that the emission spectrum is very nearly a mirror image of the absorption spectrum. The conclusion is further supported by quantum mechanical calculations (CNDO/S). By combination of measurements of fluorescence anisotropy of YO in glycerol and linear dichroism of YO in a stretched poly(vinyl alcohol) film, the transition moment of the strong visible absorption band was found to be nearly long axis polarized, in agreement with the CNDO/S calculations. The low-energy electronic transition and its polarization direction in the YO chromophore remain essentially unperturbed in the YOYO dye, suggesting that the results obtained for the excited state of the YO chromophore are applicable also to YOYO. One difference, though, is that in aqueous solutions the two YO chromophores of YOYO interact with each other, forming an internal dimer, resulting in a distorted absorption spectrum.
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3.
  • Carlsson, Christina, 1968-, et al. (författare)
  • Screening for genetic mutations
  • 1996
  • Ingår i: Nature. - 0028-0836. ; 380:6571
  • Tidskriftsartikel (övrigt vetenskapligt)
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4.
  • Gisselfält, Katrin, 1969-, et al. (författare)
  • Interactions of tris(phenanthroline)ruthenium(II) enantiomers with DNA: Effects on helix flexibility studied by the electrophoretic behavior of reptating DNA in agarose gel
  • 2000
  • Ingår i: Journal of Physical Chemistry B. - 1089-5647. ; 104:15, s. 3651-3659
  • Tidskriftsartikel (refereegranskat)abstract
    • A combination of measurement of mobility and orientational dynamics of long reptating DNA in agarose gel has been used to reveal how the binding of Delta and Lambda enantiomers of the tris(phenanthroline)ruthenium(II) ion affects the flexibility of the DNA helix. The mobility data, and data over the step length and period time of the reptation cycle, obtained in the presence of the respective enantiomer, are compared with those of free DNA and with data obtained earlier on DNAs with known variations in helix flexibility. The results suggest that the Delta form induces kinks in the DNA helix while the Lambda form gives rise to a local stiffening of the helix.
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5.
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6.
  • Jonsson, Mats, 1939-, et al. (författare)
  • Orientation of DNA during gel electrophoresis studied with linear dichroism spectroscopy
  • 1988
  • Ingår i: Biopolymers. - 0006-3525. ; 27:3, s. 381-414
  • 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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7.
  • Jonsson, Mats, 1939-, et al. (författare)
  • ORIENTATION OF LARGE DNA DURING FREE SOLUTION ELECTROPHORESIS STUDIED BY LINEAR DICHROISM
  • 1993
  • Ingår i: Journal of the Chemical Society-Faraday Transactions. - 0956-5000. ; 89:15, s. 2791-2798
  • Tidskriftsartikel (refereegranskat)abstract
    • DNA T7 (40 kbp(double dagger)), T5 (120 kbp) and T2 (170 kbp) have been studied under electrophoretic conditions in free solution (25 mmol dm-3 ionic strength) regarding chain orientation and field-free decay using phase-modulation detected linear dichroism. The steady-state orientation does not show Kerr-law behaviour for the larger T5 and T2 DNAs but increases roughly linearly with field strength, the orientation factor being around 3 x 10(-3) at 100 V cm-1. When subjected to the electric field DNA displays within 0.1-5 s an orientation overshoot which increases strongly with DNA size and comes faster the higher the field strength. When the field is switched off a major portion of the DNA orientation has relaxed within 10 ms while a smaller portion decays more slowly: 0.3 s for T2, comparable with the slowest relaxation of a Zimm-Rouse chain. The observed orientation phenomena could be important in free-solution capillary electrophoresis of DNA. The question of the mechanism by which the DNA is aligned (dipole or electrophoretic orientation?) cannot be addressed adequately within existing theories for chain-like macromolecules. Awaiting results from simulations it is speculated that the overshoot phenomenon and the slow decay component of large DNA may represent reptative deformations of the DNA coil similar to those recently observed for large DNA during gel electrophoresis. Rapid field reversal did not lead to any dip in steady-state orientation for the pure DNA; however, in a complex with the recombinase protein RecA which stacks outside DNA, apparently in a polar way to form a large permanent dipole, a pronounced dip suggests that there is a 180-degrees rotation of the particle upon field reversal. The electro-optical cell was designed to give minimal influence from electro-osmosis and convection. The experiments on T2 and T7 DNA (on the ground) were replicated under microgravity conditions during a sounding-rocket flight without any noticeable differences in orientation dynamics.
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8.
  • Nordén, Bengt, 1945-, et al. (författare)
  • ELECTROPHORETIC ORIENTATION OF DNA
  • 1991
  • Ingår i: FIRST INTERNATIONAL CONFERENCE ON ELECTROPHORESIS, SUPERCOMPUTING AND THE HUMAN GENOME. - 981-02-0273-3 ; s. 173-198
  • Bokkapitel (övrigt vetenskapligt)
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9.
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10.
  • Nordén, Bengt, 1945-, et al. (författare)
  • New Techniques for Aligning Molecules
  • 1988
  • 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
  • Konferensbidrag (övrigt vetenskapligt)
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