Compact form of DNA induced by spermidine

Gosule, Leonard C.; Schellman, John A.

doi:10.1038/259333a0

Cited by 559 publications

(394 citation statements)

References 13 publications

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“…However, the large extended size of plasmid DNA makes it difficult to pack into small liposomes. Polycations of charge +3 or higher, such as polylysine, 17 polyamines [18][19][20] and hexammine cobalt (III), 20,21 have been reported, in vitro, to condense plasmid DNA into much smaller toroid or rod-shaped structures through charge neutralization. 22 Polyamines, such as spermine, can dissociate from DNA at cytoplasmic salt concentrations, potentially releasing the DNA for transport into the nucleus.…”

Section: Introductionmentioning

confidence: 99%

A novel N-acyl phosphatidylethanolamine-containing delivery vehicle for spermine-condensed plasmid DNA

Shangguan¹,

Cabral-Lilly²,

Purandare³

et al. 2000

Gene Ther

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A unique method for formulation of plasmid DNA with phospholipids has been devised for the purpose of producing vehicles that can mediate gene delivery and transfection of living cells. The polycation, spermine, was used to condense plasmid DNA within a water-in-chloroform emulsion stabilized by phospholipids. After organic solvent removal, the particles formed could be extruded to a number average size of about 200 nm and retained DNA that was protected from nuclease digestion. This resulted in a relatively high protected DNA-to-lipid ratio of approximately 1 g DNA/ mol lipid. The size distribution of the preparation was relatively homogeneous as judged by light microscopy and quasi-elastic light scattering. Electron microscopic studies showed structural heterogeneity, but suggested that at least some of the plasmid DNA in this preparation was in the form of the previously observed spermine-condensed bent rods and toroids and was encapsulated within liposomal membranes.

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Section: Introductionmentioning

confidence: 99%

A novel N-acyl phosphatidylethanolamine-containing delivery vehicle for spermine-condensed plasmid DNA

Shangguan¹,

Cabral-Lilly²,

Purandare³

et al. 2000

Gene Ther

View full text Add to dashboard Cite

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“…1C-D). Salt concentration does not affect the extent to which bR protrudes from the membrane (~1.2 Å); its extracellular surface remains bound to the lipids through specific interactions that are not 50 electrostatic. 2,42 In contrast, monomers and trimers at the cytoplasmic surface are almost indiscernible at low salt concentration; bR inter-helical loops are visible (Fig.…”

Section: Sub-molecular Resolution Imaging Of Purple Membranementioning

confidence: 99%

“…This is valid in the limit where the coupling parameter Ξ → ∞ (Ξ = 2πq 3 l B σ s ), 50 The transition between the PB and SC regimes is then done with a sigmoid function (transition length Δ).and the function used for the fitting is We find counterion condensation for both monovalent and divalent cations, but theories predict this to occur with mainly multivalent counterions. Importantly, counterion condensation theories do not take into account the dynamic nature of biological function; as demonstrated here the cytoplasmic 90 side, despite being globally more negatively charged, avoids the formation of a correlated ionic layer using an enhanced flexibility and intercalation of positive charge at the surface to produce a dynamic electric field that avoids specific ion binding.…”

Section: Comparison With Theories: Electrostatic Correlation Of Ionsmentioning

confidence: 99%

“…Hofmeister noted in 1888 that some salts help to precipitate proteins from solution (salting-out) while other salts enhance their solubility (salting-in) 7 . These effects are traditionally explained by the influence of salt ions on the structure of water, these interpretations have introduced 50 a persistent oversimplification: the concept of "structure making" (kosmotrope) and "structure-breaking" (chaotrope) ions (Hofmesiter series). In this framework, large, low-charge ions disrupt water structure while small highly charged ions are structure-makers inducing order on the hydrogen bonded 55 water network.…”

Section: Introductionmentioning

confidence: 99%

“…Here we use the unique capability of amplitude modulation 45 atomic force microscopy (AM-AFM) operated at small amplitudes (< 2nm) to achive sub-nm resolution maps of the interaction forces between the AFM tip and PM. We characterize and quantify the local (down to single α-helix level) and global interactions that make possible the proton 50 uptake, release at the interface of bR with the solvent and study their deviation from DLVO. We exploit rapidly decaying, short-range forces 36 at the surface of bR so as to confine the image formation interaction to the front most atoms of the tip and enhace the resolution.…”

Section: Introductionmentioning

confidence: 99%

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Controlled ionic condensation at the surface of a native extremophilemembrane

2010

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entor nz gonter D F nd o¤ %t hovskyD uF nd y nD tF pF @PHIHA 9gontrolled ioni ondens tion t the surf e of n tive extremophile mem r neF9D x nos leFD P F ppF PPPEPPWF Further information on publisher's website:httpXGGdxFdoiForgGIHFIHQWGfWx HHPRVu Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. At the nanoscale level biological membranes present a complex interface with the solvent. The functional dynamics and relative flexibility of membrane components together with the presence of specific ionic effects can combine to create exciting new phenomena that challenge traditional 10 theories such as the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory or models interpreting the role of ions in terms of their ability to structure water (structure making/breaking).Here we investigate ionic effects at the surface of a highly charged extremophile membrane composed of a proton pump (bacteriorhodopsin) and archaeal lipids naturally assembled into a 2D crystal. Using amplitude-modulation atomic force microscopy (AM-AFM) in solution, we obtained 15 sub-molecular resolution images of ion-induced surface restructuring of the membrane. We demonstrate the presence of a stiff cationic layer condensed at its extracellular surface. This layer cannot be explained by traditional continuum theories. Dynamic force spectroscopy experiments suggest that it is produced by electrostatic correlation mediated by a Manning-type condensation of ions. In contrast, the cytoplasmic surface is dominated by short range repulsive hydration forces. 20These findings are relevant to archaeal bioenergetics and halophilic adaptation. Importantly, they present experimental evidence of a natural system that locally controls its interactions with the surrounding medium and challenges our current understanding of biological interfaces.

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DNA condensation by multivalent cations

1997

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In the presence of multivalent cations, high molecular weight DNA undergoes a dramatic condensation to a compact, usually highly ordered toroidal structure. This review begins with an overview of DNA condensation:condensing agents, morphology, kinetics and reversibility, and the minimum size required to form orderly condensates. It then summarizes the statistical mechanics of the collapse of stiff polymers, which shows why DNA condensation is abrupt and why toroids are favored structures. Various ways to estimate or measure intermolecular forces in DNA condensation are discussed, all of them agreeing that the free energy change per base pair is very small, on the order of 1% of thermal energy. Experimental evidence is surveyed showing that DNA condensation occurs when about 90% of its charge is neutralized by counterions. The various intermolecular forces whose interplay gives rise to DNA condensation are then reviewed. The entropy loss upon collapse of the expanded wormlike coil costs free energy, and stiffness sets limits on tight curvature. However, the dominant contributions seem to come from ions and water. Electrostatic repulsions must be overcome by high salt concentrations or by the correlated fluctuations of territorially bound multivalent cations. Hydration must be adjusted to allow a cooperative accommodation of the water structure surrounding surface groups on the DNA helices as they approach. Undulations of the DNA in its confined surroundings extend the range of the electrostatic forces. The condensing ions may also subtly modify the local structure of the double helix.

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Compact form of DNA induced by spermidine

Cited by 559 publications

References 13 publications

A novel N-acyl phosphatidylethanolamine-containing delivery vehicle for spermine-condensed plasmid DNA

A novel N-acyl phosphatidylethanolamine-containing delivery vehicle for spermine-condensed plasmid DNA

Controlled ionic condensation at the surface of a native extremophilemembrane

DNA condensation by multivalent cations

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