Aqueous Agarose Research Articles

Anion-specific salt effects in aqueous agarose systems. 1. Effects on the coil-helix transition and gelation of agarose

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnion-specific salt effects in aqueous agarose systems. 1. Effects on the coil-helix transition and gelation of agaroseLennart Piculell and Svante NilssonCite this: J. Phys. Chem. 1989, 93, 14, 5596–5601Publication Date (Print):July 1, 1989Publication History Published online1 May 2002Published inissue 1 July 1989https://doi.org/10.1021/j100351a053RIGHTS & PERMISSIONSArticle Views476Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (871 KB) Get e-Alerts

Radiation chemical and magnetic resonance studies of aqueous agarose gels containing ferrous ions

Aqueous agarose gels containing ferrous ions sustain a radiolytic chain reaction, producing Fe 3+. G(Fe 3+)-values up to 156 have been observed, independent of dose rate between 0.434 and 3.74 Gy min -1. Dissolved oxygen is needed to maintain the chain reaction, and initial ferric yields are increased if the gel is oxygen saturated, or if the Fe 2+ concentration is decreased. Longitudinal proton magnetic relaxation rates are increased in proportion to ferric production, permitting visualizing of dose levels in these gels by magnetic resonance imaging techniques. There is a potential for application to radiation therapy treatment planning.

Determination of the apolar component of the surface tension of water by contact angle measurements on gels

The interior of a gel, especially when made at a low concentration of the gel-forming matrix, retains to a large degree the major physico-chemical attributes of the continuous liquid phase. Thus when an aqueous agarose gel, consisting of x% agarose, is cut open, the cut surface may be considered as a flat surface of (100 − x) % solid water, at room temperature. By measuring contact angles with hexadecane on such hydrous surfaces, formed with 2.0, 1.75, 1.50, 1.25 and 1.O% (w/v) agarose gellified with pure water, one finds by extrapolation to 0% agarose, a value of 21.4±1.2 mJ m −2 for the apolar component of the surface tension of water. This value agrees well with the value of 21.8± 0.7 mJ m −2 reported by Fowkes, from interfacial tensions between water and various hydrocarbons.

Sol–sol structural transition of aqueous agarose systems

AbstractA structural transition is reported to occur in aqueous sols of agarose, an electrically uncharged biostructural polysaccharide. The transition has no measurable effect on size dispersity on the shape of the solute polysaccharide as observed by precision photon correlation spectroscopy. It originates a low‐angle pattern of scattered light similar to that which monitors phase separations in polymer blends. Thus, it must be due to some extent to spatially modulated polymer clustering, typical of spinodal decomposition. In the interval of temperatures studied, it precedes very distinctly in time the thermoreversible sol–gel transition, which is known to be promoted at higher concentrations. It also anticipates to an appreciable extent the spatial density modulation observed in the gel. Although reported here for the first time, a spinodal decomposition of the sol that precedes and possibly triggers the processes leading to gelation does not come unexpectedly in terms of site‐bond correlated‐percolation theory. In general, this occurrence raises the question as to whether the spontaneous onset of regions of higher and lower polymer concentration (spinodal separation) may be regarded as a novel path for biomolecular interactions and the self‐assembly of order in biomolecular systems.

Dielectric studies on emulsion of aqueous agarose gel in hydrophobic colloidal silica-oil gel.

In order to characterize the state of aggregation, dielectric relaxation due to interfacial polarization of a system of aqueous agarose gel particles dispersed in a squalane medium jellified by hydrophobic colloidal silica (denoted below as G/(S·O) emulsion) was investigated over a frequency range from 10kHz to 3MHz. The value of the parameter α, a measure of the distribution of relaxation frequency determined from complex plane plots, was zero when there was no aggregation. It was positive while aggregation was progressing and fell toward zero as the aggregation approached the steady state during storage. When the dependence of α on the uniformity of particle size was taken into account, the transient characteristics of dielectric relaxation represented by the positive value of α seemed to indicate that the mode of ion diffusion through the interface layer between particles in contact changed depending on the magnitude and particle size variation of particle clusters. Microscopic observation during aggregation supported the hypothesis that positive α appeared during the progressive stage of aggregation as a result of a transient deviation from uniformity of aggregation. The influence of aggregation on other dielectric parameters is also discussed.

Gelation and Its Related Changes in Amylose Solution

The phase change for an amylose solution in the binary solvent system of dimethylsulfoxide (DMSO) with water was investigated under various conditions from sol to gel. The phase change was determined with measurements of the fluorescent depolarization and other methods by varying the solvent constitution at 25°C, and then varying the temperature at 10% of DMSO concentration.The phase diagrams obtained with both variables were substantially similar and were also similar to those for an aqueous agarose solution. This similarity in phase diagram suggests a similar gel formation mechanism of amylose to agarose.It was found that the phase separation point for the amylose solution agreed with the gel formation point and also with the starting point of retrogradation.

Gelation and its related changes in amylose solution.

The phase change for an amylose solution in the binary solvent system of dimethylsulfoxide (DMSO) with water was investigated under various conditions from sol to gel. The phase change was determined with measurements of the fluorescent depolarization and other methods by varying the solvent constitution at 25°C, and then varying the temperature at 10%ofDMSOconcentration. The phase diagrams obtained with both variables were substantially similar and were also similar to those for an aqueous agarose solution. This similarity in phase diagram suggests a similar gel formation mechanismof amylose to agarose. It was found that the phase separation point for the amylose solution agreed with the gel formation point and also with the starting point of retrogradation.

13C NMR Spectra at 67.9 MHz of Aqueous Agarose Solutions and Gels.

13C NMR Spectra at 67.9 MHz of Aqueous Agarose Solutions and Gels.

Modified hemolytic plaque technique for the detection of bluetongue virus antibody-forming cells

A hemolytic plaque assay was developed for the detection of antibody-forming cells to bluetongue virus (BTV). Sheep erythrocytes (SRBC), onto which BTV had been absorbed, served as the indicator of lysis due to the presence of BTV antibody-forming cells. The ratio of BTV to SRBC was found to be critical for optimum hemolytic plaque formation. For routine use, 50 mul of 12% BTV SRBC, 0.1 ml of a spleen cell suspension, and 0.5 ml of 0.5% agarose in a balanced salt solution were mixed and plated on a microscope slide precoated with 0.1% aqueous agarose. Slides were incubated for 1 h at 37 C in a humidified incubator and subsequently flooded with 0.4 ml of a 1:15 dilution of complement. Incubation was continued for a further 2 h before the hemolytic plaques were scored. It was not possible to establish BTV serotype specificity by this technique.

Laser light scattering by polymer gels

The frequency-integrated, absolute Rayleigh–Debye scattering measured as a function of scattering angle down to 1°, contains information about the supramolecular structural order exhibited by gels. For covalently crosslinked, swollen polymer networks this provides a measure for the degree of spatial non-randomness in crosslinking. The non-randomness index for a series of poly(2-hydroxyethyl methacrylate)(PHEMA) networks is found to vary systematically by a factor of over a hundred depending on the history of the network formation. Intensity-fluctuation spectroscopy at any given scattering angle provides a probe for the local viscoelasticity of a gel without applying an external driving force. Swollen PHEMA networks are found to exhibit a spectrum of long (10–3 s) relaxation times. In dilute aqueous agarose systems both above and below the sol→gel transition a similar spectrum of relaxation times is found. During the transition, the autocorrelation function exhibits oscillatory behaviour for several hours. This is attributed to the mass flow taking place during the microphase separation. Upon inducing the sol→gel transition in agarose solutions by quenching to various temperatures below the phase boundary, the frequency-integrated Rayleigh–Debye scattering is found to vary systematically a thousand fold. A Bragg maximum appears, caused by the regularly spaced spontaneous concentration fluctuations which occur in a nucleation-free, spinodal phase decomposition.

Steady‐state and pulsed NMR studies of gelation in aqueous agarose

AbstractSteady‐state and pulsed NMR techniques have been used to investigate molecular motion in sols and gels of agarose. In passing through the sol–gel transition, the molecular mobility of water molecules is reduced only by a small amount, whereas motion of the polymer chains is greatly attenuated. The results are discused in terms of the network theory of gelation, with references to the role of water in the process and the nature of the “junction zones” between polymer chains. T2 and line‐width measurements are dominated by exchange broadening. The effects of exchange rate and differences in relaxation time between the exchanging sites are discussed. The temperature hysteresis behavior of agarose gels has been investigated and the effects of “ageing” correlated with changes in nuclear relaxation times. The synergistic increase in gel strength obtained on adding locust bean gum (LBG) to agarose has been investigated. The results indicate that LBG does not form double‐helix junctions and may decrease rates of gelation by steric effects. At high agarose concentration, the LBG remains mainly in solution in interstitial water, but at low agarose concentration, it is suggested that the LBG can link gel aggregates together into a self‐supporting structure, producing a synergistic increase in gel strength. Comparisons have been made between the nature of the agarose–LBG interaction and agarose–cellulose interactions in biological systems.