Structural modifications in the swelling of inhomogeneous microgels by light and neutron scattering

Fernández-Barbero, A.; Fernández‐Nieves, Alberto; Grillo, Isabelle; López-Cabarcos, Enrique

doi:10.1103/physreve.66.051803

Cited by 214 publications

(271 citation statements)

References 35 publications

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“…This behaviour goes along with a smoother particle surface and a decrease of pore sizes as it has been detected by SANS, DLS and confocal laser scanning microscopy. 29,52,58 Moreover, our results evidence that the diameter decrease above VPTT is mainly due to the core shrinking more than to the shell. Such details are accessible only to STXM analysis, in which the core and shell regions are directly distinguished.…”

Section: Resultssupporting

confidence: 53%

Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

et al. 2016

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High resolution scanning soft X-ray transmission microscopy (STXM) has been employed to investigate individual thermoresponsive microgel particles in aqueous environments. STXM generates 2-dimensional projections with spatial resolutions in the regime of a few 10 s of nm. In the present study we are able to regain a 3D representation of the investigated specimen and observe the deswelling of the microgel particles upon heating, thus offering insight into the thermoresponsive behaviour of individual differently sized particles. We employ a 2-shell model that is able to derive the radial concentration profile of individual microgels particles and thus serves as a complementary method to scattering experiments that average over all particles. Furthermore, we are able to detect the different deswelling behaviour of the particle interior and its interface to the water environment.

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Section: Resultssupporting

confidence: 53%

Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

et al. 2016

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“…While the dependence of the mixing parameter of microgel particles with temperature or salt has been previously described in the literature, 47,58,64 its dependence with hydrostatic pressure, P, has not been investigated so far. In order to obtain how χ depends on hydrostatic pressure, we measure the particle size as a function of P, at a temperature of T = 298 K. The application of external pressure induces a deswelling, which is closely comparable to that induced with temperature, as shown in Figure 3; the radius changes from ∼130 nm at P= 0.1 MPa, to ∼ 60 nm for P > 400 MPa.…”

Section: Resultsmentioning

confidence: 99%

Deswelling Microgel Particles Using Hydrostatic Pressure

et al. 2009

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We report on the use of hydrostatic pressure, P, to deswell thermosensitive poly-(N-isopropylacrylamide) (pNIPAM) microgels and show that it can affect the polymer-solvent mixing as much as temperature, which is the traditional variable used to deswell pNIPAM particles. Interestingly, the microgel volume changes more gradually with pressure than it does with temperature. By comparing the pressure and temperature induced deswelling, we obtain the pressure dependence of the Flory solvency parameter, χ; it increases with P, indicating that pressure decreases the polymer-solvent miscibility. We interpret this increase in terms of the entropy change, 4S, when a polymer-solvent contact is broken to form a solvent-solvent contact and find that |4S| also increases with P, consistent with previous experimental results with polymers and other gels. Hydrostatic pressure thus changes the entropic contribution of mixing, causing χ to increase and ultimately leading to particle deswelling.

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“…5B). Conversion to a two-step intensity correlation function suggests a transition to two distinct populations of DNA molecules with different diffusion coefficients (36,38), presumably swollen DNA condensates and completely decondensed DNA (37,39). The time constant for the decondensation of BP-DNA condensates was found to depend on the 2-mercaptoethanol concentration in the high salt/urea denaturing solution (Fig.…”

Section: Condensation Of Dna By Foldedmentioning

confidence: 99%

Formation of Native-like Mammalian Sperm Cell Chromatin with Folded Bull Protamine

Vilfan

Conwell

Hud

2004

Journal of Biological Chemistry

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The DNA of most vertebrate sperm cells is packaged by protamines. The primary structure of mammalian protamine I can be divided into three domains, a central DNA binding domain that is arginine-rich and aminoand carboxyl-terminal domains that are rich in cysteine residues. In native bull sperm chromatin, intramolecular disulfide bonds hold the terminal domains of bull protamine folded back onto the central DNA binding domain, whereas intermolecular disulfide bonds between DNA-bound protamines help stabilize the chromatin of mature mammalian sperm cells. Folded bull protamine was used to condense DNA in vitro under various solution conditions. Using transmission electron microscopy and light scattering, we show that bull protamine forms particles with DNA that are morphologically similar to the subunits of native bull sperm chromatin. In addition, the stability provided by intermolecular disulfide bonds formed between bull protamine molecules within in vitro DNA condensates is comparable with that observed for native bull sperm chromatin. The importance of the bull protamine terminal domains in controlling the bull sperm chromatin morphology is indicated by our observation that DNA condensates formed under identical conditions with a fish protamine, which lacks cysteine-rich terminal domains, do not produce as uniform structures as bull protamine. A model is also presented for the bull protamine⅐DNA complex in native sperm cell chromatin that provides an explanation for the positions of the cysteine residues in bull protamine that form intermolecular disulfide bonds.During vertebrate spermiogenesis, chromatin is dramatically reorganized in developing spermatids as histones and other nonhistone-chromosomal proteins are replaced by arginine-rich oligopeptides known as protamines (1, 2). DNA packaged by protamines in mature sperm cells is transcriptionally inactive and packed at a density that approaches that of a crystalline state (3, 4). The packing, or condensation, of DNA by protamines has been investigated extensively by chemical and physical studies of natural sperm chromatin as well as by the investigation of protamine-DNA condensates prepared in vitro by the mixing of isolated protamines with free DNA (3-17). In vivo, protamines condense the DNA of vertebrate sperm cells into thousands of particles that vary in diameter from 50 to 100 nm (3, 11, 18 -21). Each protamine-DNA particle is estimated to contain on the order of 50 kb of DNA (21). Few attempts have been made to reconstitute mammalian sperm cell chromatin using purified mammalian protamines, and reported efforts have not yielded protamine-DNA condensates with DNA as highly condensed as that found in mature sperm cell chromatin (8).Some mammalian sperm cells contain two different types of protamine, referred to as protamine I and protamine II. Protamine I is present in all mammalian sperm cells, and its amino acid sequence is relatively conserved among mammals. The protamines of other vertebrates, such as fish, are similar to protamine I of mammals. P...

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Structural modifications in the swelling of inhomogeneous microgels by light and neutron scattering

Cited by 214 publications

References 35 publications

Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

Deswelling Microgel Particles Using Hydrostatic Pressure

Formation of Native-like Mammalian Sperm Cell Chromatin with Folded Bull Protamine

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