A liquid crystalline phase in spermidine-condensed DNA

Sikorav, Jean‐Louis; Pelta, Juan; Livolant, Françoise

doi:10.1016/s0006-3495(94)80640-x

Cited by 98 publications

(81 citation statements)

References 38 publications

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“…The polyamines spermine or spermidine are ubiquitous compounds that stabilize the DNA double helix in vivo, and which, consequently, were intensively studied as a valuable model system for studying DNA organization in biological structures (25,32). Lx used in this report were partly composed of spermine-containing lipids and DNA and could constitute another model.…”

Section: Resultsmentioning

confidence: 99%

DNA packing in stable lipid complexes designed for gene transfer imitates DNA compaction in bacteriophage

Schmutz

Durand

Debin

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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The structure of complexes made from DNA and suitable lipids (lipoplex, Lx) was examined by cryo-electron microscopy (cryoEM). We observed a distinct concentric ring-like pattern with striated shells when using plasmid DNA. These spherical multilamellar particles have a mean diameter of 254 nm with repetitive spacing of 7.5 nm with striation of 5.3 nm width. Small angle x-ray scattering revealed repetitive ordering of 6.9 nm, suggesting a lamellar structure containing at least 12 layers. This concentric and lamellar structure with different packing regimes also was observed by cryoEM when using linear double-stranded DNA, singlestranded DNA, and oligodeoxynucleotides. DNA chains could be visualized in DNA͞lipid complexes. Such specific supramolecular organization is the result of thermodynamic forces, which cause compaction to occur through concentric winding of DNA in a liquid crystalline phase. CryoEM examination of T4 phage DNA packed either in T4 capsides or in lipidic particles showed similar patterns. Small angle x-ray scattering suggested an hexagonal phase in Lx-T4 DNA. Our results indicate that both lamellar and hexagonal phases may coexist in the same Lx preparation or particle and that transition between both phases may depend on equilibrium influenced by type and length of the DNA used.

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Section: Resultsmentioning

confidence: 99%

DNA packing in stable lipid complexes designed for gene transfer imitates DNA compaction in bacteriophage

Schmutz

Durand

Debin

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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“…8. The length of the fragments obtained ranged from 130 to 600 base pairs with 50% of 146 (Ϯ7) base pairs.…”

Section: Methodsmentioning

confidence: 99%

“…Based on these data, several types of crystalline and liquid crystalline structures have been suggested for these DNA aggregates (5, 7). We have recently undertaken a study of these DNA aggregates using short (about 150 base pairs long) DNA molecules (8). In the case of the trivalent cation spermidine, we have found that the aggregate is generally biphasic and contains a liquid crystalline phase.…”

Section: Multivalent Cations With a Charge Of 3ϩ Or Greater Induce Thmentioning

confidence: 99%

DNA Aggregation Induced by Polyamines and Cobalthexamine

Pelta

Livolant

Sikorav

1996

Journal of Biological Chemistry

353

385

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We have studied the precipitation of short DNA molecules by the polycations spermidine, spermine, and cobalthexamine. The addition of these cations to a DNA solution leads first to the precipitation of the DNA; further addition resolubilizes the DNA pellet. The multivalent salt concentration required for resolubilization is essentially independent of the DNA concentration (between 1 g/ml and 1 mg/ml) and of the monovalent cation concentration present in the DNA solution (up to 100 mM). The DNA aggregates are anisotropic; those obtained in the presence of the polyamines spermidine and spermine generally contain a cholesteric liquid crystalline phase that flows spontaneously. In contrast this phase is never seen in the presence of cobalthexamine. We propose that the ability of polyamines to condense DNA in fluid structures is an essential feature of their biological functions.Multivalent cations with a charge of 3ϩ or greater induce the condensation of DNA in aqueous solution (reviewed in Ref. 1). In extremely dilute DNA solutions, one can observe the monomolecular collapse of long chains; with more concentrated DNA solutions (of short or long chains), aggregation sets in. Electrostatic forces appear to be predominant in DNA condensation. For highly charged polyelectrolytes there is a strong electrostatic repulsion between the chains. One expects the addition of multivalent cations to decrease this repulsion. DNA condensation by multivalent cations has been analyzed within the framework of the counterion condensation theory developed by Manning (2). This theory predicts the fraction of the DNA charges neutralized by a given cation: a saturating trivalent cation for instance should neutralize 92% of the DNA charges. It has been shown experimentally that approximately 90% of the DNA charges must be neutralized before DNA condensation can occur (3, 4). In addition, mono-and divalent cations compete with multivalent cations in the condensation process, in agreement with the proposal that the interactions are predominantly electrostatic. It is known, however, that a purely electrostatic model is insufficient to account for the experimental data; cobalthexamine is for instance five times more efficient as a condensing agent than spermidine, although these compounds have the same charge (3ϩ) (4).DNA condensation has been studied with the naturally occurring polyamines spermidine (3ϩ) and spermine (4ϩ), as well as with the inorganic cation cobalthexamine (3ϩ). Experimental data indicate that condensation is usually coupled with an isotropic to an anisotropic transition. In particular, high molecular weight DNA aggregates formed by spermidine, spermine, or cobalthexamine give a strong equatorial reflection when analyzed by x-ray diffraction (5, 6). Based on these data, several types of crystalline and liquid crystalline structures have been suggested for these DNA aggregates (5, 7). We have recently undertaken a study of these DNA aggregates using short (about 150 base pairs long) DNA molecules (8). In the case of the triv...

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“…The enhanced alignment of the polymer chains in the nematic state is the basis for several material properties and processes such as high strength fibers 1 and flow induced crystallization. [2][3][4][5][6] Solutions of DNA form lyotropic liquid crystalline phases under several biologically relevant conditions including molecular crowding, 7 large molecular weight, 8 polycationic agents ͑synthetic 9 and natural 10 ͒, and supercoiling in plasmid DNA. 11 Thus the nematic state of main-chain liquid crystalline polymers is a subject of importance in both materials science and biology.…”

Section: Introductionmentioning

confidence: 99%

Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

Spakowitz

Wang

2003

The Journal of Chemical Physics

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We study the thermodynamics and single-chain statistics of wormlike polymer solutions with Maier-Saupe-type interactions using self-consistent-field ͑SCF͒ theory. The SCF equations are derived using a systematic field-theoretical approach which yields the SCF equations as the lowest order approximation, but permits fluctuation corrections to be incorporated. We solve the SCF equations using the spheroidal functions, which provides a nonperturbative description of the thermodynamics and single-chain statistics in the nematic state for arbitrary degrees of nematic order. Several types of phase diagrams are predicted, with an emphasis on the limit of metastability ͑spinodal͒ associated with each phase. The shape and location of these spinodals suggest interesting scenarios for the phase transition kinetics. A large but finite persistence length is shown to significantly decrease the isotropic-nematic transition temperature relative to that for rigid rods. In the nematic state, the mean-square end-to-end distance in the parallel and perpendicular directions are governed by two separate correlation lengths. An exact relationship between these correlation lengths and the eigenvalues of the spheroidal functions is provided, which reproduces the analytical expressions predicted from earlier studies in the limit of large nematic strength. The dominant contribution to the single-chain thermodynamics is shown to arise from small amplitude undulations in the directions perpendicular to the nematic direction; the presence of hairpins, though crucial for determining the dimensions of the polymer, has insignificant consequences on the single-chain thermodynamics.

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A liquid crystalline phase in spermidine-condensed DNA

Cited by 98 publications

References 38 publications

DNA packing in stable lipid complexes designed for gene transfer imitates DNA compaction in bacteriophage

DNA packing in stable lipid complexes designed for gene transfer imitates DNA compaction in bacteriophage

DNA Aggregation Induced by Polyamines and Cobalthexamine

Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

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