Theory of polyelectrolytes in solutions and at surfaces

Dobrynin, Andrey V.; Rubinstein, Michael

doi:10.1016/j.progpolymsci.2005.07.006

Cited by 1,368 publications

(1,638 citation statements)

References 231 publications

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“…We attribute this peak to the dominancy of hydration forces over conformational entropy. 17,27,28 Rabin et al 18 explain this tensile stress peak by a model that considers that at low water vapor concentrations (below 2%) the adsorption of water is accompanied by enhanced expulsion of vacancies, and thus, compression of the monolayer. We must note that the tensile peak appears here (for initially coiled strands in air) in the dehydration curve and not in the hydration curve from 0% to higher relative humidity, as it is the case studied in the Rabin model and observed experimentally for high density monolayers in a standing up configuration (see Supplementary Materials).…”

Section: Resultsmentioning

confidence: 99%

Hydration Induced Stress on DNA Monolayers Grafted on Microcantilevers

et al. 2014

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Surface tethered single-stranded DNA films are relevant biorecognition layers for oligonucleotide sequence identification. Also, hydration induced effects on these films have proven useful for the nanomechanical detection of DNA hybridization. Here, we apply nanomechanical sensors and atomic force microscopy to characterize in air and upon varying relative humidity conditions the swelling and deswelling of grafted single stranded and double stranded DNA films. The combination of these techniques validates a two-step hybridization process, where complementary strands first bind to the surface tethered single stranded DNA probes and then slowly proceed to a fully zipped configuration. Our results also demonstrate that, despite the slow hybridization kinetics observed for grafted DNA onto microcantilever surfaces, ex-situ sequence identification does not require hybridization times typically longer than 1 hour, while quantification is a major challenge.. 2

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Section: Resultsmentioning

confidence: 99%

Hydration Induced Stress on DNA Monolayers Grafted on Microcantilevers

et al. 2014

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“…6,7 In understanding the conformation of polyions and their arrangement in solution, the counterion atmosphere enters as a source of screening for the charges of the polyion backbone. 8,9 As such the polyion backbone rigidity may be strongly enhanced due to a lack of screening. The way the polyion is modeled also depends on the way the atmosphere is described: mean-field approximation, Poisson−Boltzmann, within the Debye−Huckel approximation or a nonlinear PB, or a nonmean-field approximation taking charge correlations into account.…”

Section: ■ Introductionmentioning

confidence: 99%

Probing the Mesh Formed by the Semirigid Polyelectrolytes

et al. 2013

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ABSTRACT:We correlate conformation and dynamics of the semirigid polyelectrolytes deoxyribonucleic acid (DNA) and hyaluronic acid (HA) in the semidilute regime, across a broad concentration range (10 −3 − 10 2 g/L). Salt-free polyelectrolytes are distinct from uncharged polymers as they presumably form a rather rigid, isotropic mesh. The polyelectrolyte characteristic mesh size is known as de Gennes correlation length ξ. We directly probed the mesh formed by DNA and HA, by employing fluorescence correlation spectroscopy (FCS) to measure the diffusion coefficient of fluorescently labeled DNA fragments added in trace amounts. For the salt-free solutions we found that the DNA or HA mesh size has to be 2−3 times larger than the fragments for them to start to diffuse freely (as if in the dilute solution). For a tighter mesh (concentrations 0.1−1 g/L), the fragment diffusion coefficient is only half the free diffusion value. Conversely, fragments show the free diffusion coefficientas if there is no meshin DNA or HA in 10 mM buffer. This complies well with the fact that the ξ fades for polyelectrolytes with added salt. The diffusion coefficient falls off further when the mesh size gets smaller than the fragment size (above 1 g/L) and a similar value is reached in buffer as well as in pure water, respectively, at the highest measured concentrations (10 g/L). We also performed small-angle X-ray scattering (SAXS) on HA and DNA (range 3−130 g/L) to complement our previous dielectric spectroscopy (DS) studies (range 0.01−5 g/L). Combined, these methods provide reference values of the de Gennes length ξ across the range studied by FCS.

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“…[1a] These chemical and structural varieties combined with the ionic environment control their conformation. [3] The sequence motif of lambda-carrageenan has been suggested to prevent the formation of any secondary structure and thus gel formation, whereas iota-carrageenan has been reported to be capable of undergoing a coil-helix transition as a first event of gelation. [4] For their thermoreversible gelation in aqueous solution, a two-step process involving an initial ion-induced helix formation followed by association into networks is generally accepted.…”

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Unravelling Secondary Structure Changes on Individual Anionic Polysaccharide Chains by Atomic Force Microscopy

2014

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The structural conformations of the anionic carrageenan polysaccharides in the presence of monovalent salt close to physiological conditions are studied by atomic force microscopy. Iota-carrageenan undergoes a coil-helix transition at high ionic strength, whereas lambda-carrageenan remains in the coiled state. Polymer statistical analysis reveals an increase in persistence length from 22.6 AE 0.2 nm in the random coil, to 26.4 AE 0.2 nm in the ordered helical conformation, indicating an increased rigidity of the helical iota-carrageenan chains. The many decades-long debated issue on whether the ordered state can exist as single or double helix, is conclusively resolved by demonstrating the existence of a unimeric helix formed intramolecularly by a single polymer chain.Carrageenans are naturally occurring anionic polysaccharides extracted from red seaweed species and find application in food, cosmetic, and pharmaceutical product formulations where they serve as gelling agents, thickeners, stabilizers, and excipients. [1,2] Referring to a family of sulfated linear galactans, their principal disaccharide repeating unit consists of alternating b-(1!3)-and a-(1!4)-d-galactose or 3,6-anhydride residues. [1c] Following the traditional classification, iotaand lambda-carrageenan have two and three sulfate groups, respectively, with the former containing a 3,6-anhydridebridge. [1a] These chemical and structural varieties combined with the ionic environment control their conformation. [3] The sequence motif of lambda-carrageenan has been suggested to prevent the formation of any secondary structure and thus gel formation, whereas iota-carrageenan has been reported to be capable of undergoing a coil-helix transition as a first event of gelation. [4] For their thermoreversible gelation in aqueous solution, a two-step process involving an initial ion-induced helix formation followed by association into networks is generally accepted. Nonetheless, the mechanisms governing the conformational transition, ion-specificity effects, and the mode of molecular association into a percolating gel are still highly debated. [2] An ordered dimeric double helix with 1.3 nm diameter was initially proposed for iota-carrageenan based on fiber X-ray diffraction results, [5a] which was further supported by osmometry, [5b] stopped-flow polarimetry, [5c] sizeexclusion chromatography combined with light scattering, [5d, e] and differential scanning calorimetry.[5f] Strong indication for a single-stranded iota-carrageenan helix as the ordered conformation emerged, however, from other osmometry studies combined with measurements of optical rotation [4] and intrinsic viscosity, [6a] which were substantiated by light scattering data, [6b] leaving the nature of the ordered state a highly controversial issue.This study focuses on resolving the disorder-order conformational transition in molecular solutions of these anionic polysaccharides by atomic force microscopy (AFM) imaging. The conformational change from disordered carrageenans i...

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Theory of polyelectrolytes in solutions and at surfaces

Cited by 1,368 publications

References 231 publications

Hydration Induced Stress on DNA Monolayers Grafted on Microcantilevers

Hydration Induced Stress on DNA Monolayers Grafted on Microcantilevers

Probing the Mesh Formed by the Semirigid Polyelectrolytes

Unravelling Secondary Structure Changes on Individual Anionic Polysaccharide Chains by Atomic Force Microscopy

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