“…Some differences have been observed in CD spectra. In contrast to the spectrum of the original native DNA in TBE buffer characteristic for the B-form of the double helix, the spectrum of the DNA−DODA complex in chloroform apparently indicates a conformational transition of the B-form into the more compact C-form. , Similar CD spectra were observed for highly compacted two-spiral DNAs included in bacteriophages and earlier considered to be characteristic for a highly wound DNA double helix …”
The stoichiometric complexes of the DNA samples of rather different molecular masses: 300−500 b.p.
(DNA1) and 5000−10000 b.p. (DNA2) with dodecyldimethylammonium (DODA) chloride as a cationic
amphiphile were prepared. DNA1−DODA and DNA2−DODA complexes are soluble in low polar organic
solvents, in particular, in chloroform, as well as the complexes of ordinary linear polyelectrolytes with
micelle-forming ionic surfactants. The solution behavior of the DNA−DODA complexes was studied by
ultracentrifugation, viscometry, isothermal diffusion, and electrical birefringence techniques. It has been
found that the DNA−DODA complex species in their dilute solutions in chloroform and a chloroform−acetone mixture (2:1) are represented by individual complex macromolecules retaining a double spirality,
but strongly compacted. The latter is contrasting with other polyelectrolyte−surfactant complexes, which
behave in chloroform as in a good solvent, taking expanded random coil conformations. The possible reason
of such a basic difference is discussed and considered to be the result of an inherent tendency of the DNA
double helix to be compacted if not ionized. This tendency has been detected due to a unique compromise
between the thermodynamic solubility and complete electric neutrality of DNA−surfactant complex
macromolecules in low polar organic solvent.
“…Some differences have been observed in CD spectra. In contrast to the spectrum of the original native DNA in TBE buffer characteristic for the B-form of the double helix, the spectrum of the DNA−DODA complex in chloroform apparently indicates a conformational transition of the B-form into the more compact C-form. , Similar CD spectra were observed for highly compacted two-spiral DNAs included in bacteriophages and earlier considered to be characteristic for a highly wound DNA double helix …”
The stoichiometric complexes of the DNA samples of rather different molecular masses: 300−500 b.p.
(DNA1) and 5000−10000 b.p. (DNA2) with dodecyldimethylammonium (DODA) chloride as a cationic
amphiphile were prepared. DNA1−DODA and DNA2−DODA complexes are soluble in low polar organic
solvents, in particular, in chloroform, as well as the complexes of ordinary linear polyelectrolytes with
micelle-forming ionic surfactants. The solution behavior of the DNA−DODA complexes was studied by
ultracentrifugation, viscometry, isothermal diffusion, and electrical birefringence techniques. It has been
found that the DNA−DODA complex species in their dilute solutions in chloroform and a chloroform−acetone mixture (2:1) are represented by individual complex macromolecules retaining a double spirality,
but strongly compacted. The latter is contrasting with other polyelectrolyte−surfactant complexes, which
behave in chloroform as in a good solvent, taking expanded random coil conformations. The possible reason
of such a basic difference is discussed and considered to be the result of an inherent tendency of the DNA
double helix to be compacted if not ionized. This tendency has been detected due to a unique compromise
between the thermodynamic solubility and complete electric neutrality of DNA−surfactant complex
macromolecules in low polar organic solvent.
“…In contrast, the CD spectrum of DNA at 90% (v/v) 2-propanol (curve 3) differs from that of native DNA and displays an A-like structure, which is characterized by a positive band around 270 nm, a negative band around 240 nm, and a crossover at 252 nm . Similar CD spectra have been found for double-stranded DNAs in particles of medium-sized bacteriophage . The CD spectra of DNA−CTAB complexes at 40% (v/v) and 90% (v/v) are essentially the same in both ethanol and 2-propanol.…”
The single-chain observation of isolated giant DNAs complexed with a cationic surfactant, CTAB,
was performed using fluorescence microscopy. The DNA−CTAB complex exhibits a re-entrant transition,
collapsed globule → elongated coil → collapsed globule, with an increase in the alcohol concentration. The
existence of DNA in its coil state at an intermediate concentration of alcohol implies that this environment is
a good solvent for the DNA chains. On the other hand, the presence of the globule state at both low and high
alcohol concentrations indicates that this is a poor solvent for the complex. Regardless of this fact, the globule
generated at a high alcohol
concentration is unexpectedly soluble; i.e., this is a good solvent for
the complex
with respect to the solvability, but it is a bad solvent with
respect to the polymer conformation. This unique
property of the complex is attributable to the effect of micelle formation, where surfactant molecules cover
the entire globule and lower the surface energy of the collapsed state. This conclusion is supported by additional
experiments on the conformational change in DNA with alcohol in the absence of CTAB and on observations
with CD and UV spectroscopy for the complex with different alcohol concentrations.
“…Similar spectra were observed for soluble complexes of the DNA with and DAB-dendr-(NH 2 ) 64 . It is significant that the above peculiarities were earlier observed in CD spectra of native DNA incorporated in medium-sized bacteriophage particles and considered to be a characteristic of a highly wound DNA double helix. , Therefore, it is likely that such winding is also realized for the DNA molecules compacted within the soluble DNA−dendrimer complex species. 4 CD spectra of DNA (1) and DNA−DAB-dendr-(NH 2 ) 32 complex (2) in 0.01 M NaCl solution.…”
Investigations have been carried out to clarify the binding interactions between two kinds
of native DNA: one from salmon sperm (300−500 bp) and another from bacteriophage T4dC (166 kbp)
and amine-terminated, diaminobutane core, poly(propylene imine) dendrimers (Astramol) of five
generations (G1, G2, G3, G4, and G5). All dendrimers interacting with DNA at an equal concentration
of amine and phosphate groups form electroneutral water-insoluble interpolyelectrolyte complexes (IPECs).
However, G4 and G5 added to DNA solution in excess form positively charged water-soluble IPECs
representing perfect objects to investigate the state of DNA molecules incorporated into IPEC. Using UV
spectroscopy and CD spectroscopy combined with ultracentrifugation, it is shown that complexed DNA
compacts, revealing a wound double-helical structure. Using fluorescence microscopy, we observed
compaction of individual ultrahigh molecular mass DNA interacting with excess of G4 to form water-soluble positively charged IPECs “unimers”.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
