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- Carlsson, Christina, 1968, et al.
(författare)
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OPTICAL AND PHOTOPHYSICAL PROPERTIES OF THE OXAZOLE YELLOW DNA PROBES YO AND YOYO
- 1994
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Ingår i: Journal of Physical Chemistry. - : American Chemical Society (ACS). - 0022-3654 .- 1541-5740. ; 98:40, s. 10313-10321
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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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| 2. |
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| 3. |
- Jonsson, Mats, 1939, et al.
(författare)
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ORIENTATION OF LARGE DNA DURING FREE SOLUTION ELECTROPHORESIS STUDIED BY LINEAR DICHROISM
- 1993
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Ingår i: Journal of the Chemical Society - Faraday Transactions. - : Royal Society of Chemistry (RSC). - 0956-5000. ; 89:15, s. 2791-2798
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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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| 4. |
- Nordén, Bengt, 1945, et al.
(författare)
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ELECTROPHORETIC ORIENTATION OF DNA
- 1991
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Ingår i: FIRST INTERNATIONAL CONFERENCE ON ELECTROPHORESIS, SUPERCOMPUTING AND THE HUMAN GENOME. - 9810202733 ; , s. 173-198
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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