Structural studies of agar–gelatin complex coacervates by small angle neutron scattering, rheology and differential scanning calorimetry

Singh, Shailja; Aswal, Vinod K.; Bohidar, H. B.

doi:10.1016/j.ijbiomac.2007.03.009

Cited by 71 publications

(36 citation statements)

References 41 publications

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“…The viscoelastic property of the GA-Ch complex at pH 4.5 was significantly higher than those of the coacervates formed at pH 3.0 and 6.0, showing the follow order: 4.5 > 6.0 > 3.0. A predominantly viscous behavior has been reported for other coacervates: agar-gelatin (Singh, Aswal, & Bohidar, 2007), bovine serum albumin (BSA)-poly-diallyldimethylammonium chloride (PDADMAC) (Bohidar, Dubin, Majhi, Tribet, & Jaeger, 2005;Kayitmazer, Strand, Tribet, Jaeger, & Dubin, 2007), and whey protein-gum Arabic coacervates (Weinbreck, Wientjes, Nieuwenhuijse, Robijn, & de Kruif, 2004). In the latter, the G 00 values were approximately ten times higher than the G 0 values at a pH of 4.0.…”

Section: Rheological Measurementsmentioning

confidence: 87%

Determination of the gum Arabic–chitosan interactions by Fourier Transform Infrared Spectroscopy and characterization of the microstructure and rheological features of their coacervates

Espinosa‐Andrews¹,

Sandoval-Castilla²,

Vázquez‐Torres³

et al. 2010

Carbohydrate Polymers

227

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Section: Rheological Measurementsmentioning

confidence: 87%

Determination of the gum Arabic–chitosan interactions by Fourier Transform Infrared Spectroscopy and characterization of the microstructure and rheological features of their coacervates

Espinosa‐Andrews¹,

Sandoval-Castilla²,

Vázquez‐Torres³

et al. 2010

Carbohydrate Polymers

227

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“…More recently, SANS was used for β-lactoglobulin/pectin coacervates, and showed two kinds of microstructures, either protein molecules dispersed in the coacervate network, or protein domains enclosed in the interpenetrated pectin chains 39 . Networks of polymer-rich zones were also found for agar-gelatin complex coacervates, but with a correlation length around 1.2 nm only 40 .…”

Section: Parameters Involved In the Electrostatic Complexesmentioning

confidence: 91%

Rodlike Complexes of a Polyelectrolyte (Hyaluronan) and a Protein (Lysozyme) Observed by SANS

et al. 2011

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We study by Small Angle Neutron Scattering (SANS) the structure of Hyaluronan -Lysozyme 2 2 complexes. Hyaluronan (HA) is a polysaccharide of 9 nm intrinsic persistence length that bears one negative charge per disaccharide monomer (M mol = 401.3 g/mol); two molecular weights, M w = 6000 and 500 000 Da were used. The pH was adjusted at 4.7 and 7.4 so that lysozyme has a global charge of +10 and + 8 respectively. The lysozyme concentration was varied from 3 to 40 g/L, at constant HA concentration (10 g/L). At low protein concentration, samples are monophasic and SANS experiments reveal only fluctuations of concentration although, at high protein concentration, clusters are observed by SANS in the dense phase of the diphasic samples. In between, close to the onset of the phase separation, a distinct original scattering is observed. It is characteristic of a rod-like shape, which could characterize "single" complexes involving one or a few polymer chains. For the large molecular weight (500 000) the rodlike rigid domains extend to much larger length scale than the persistence length of the HA chain alone in solution and the range of the SANS investigation. They can be described as a necklace of proteins attached along a backbone of diameter one or a few HA chains. For the short chains (M w ~ 6000), the rod length of the complexes is close to the chain contour length (~ 15 nm).

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“…One of these was close to agar gel melting temperature [83] (≈ 85°C). In gelatin A-agar complex coacervate, there were also two melting temperatures, one being near to the melting temperature of gelatin gel [63] and the other at 75°C. However, in our present system, we recovered only one melting temperature near 75°C, which was different from the melting temperatures of its constituent polymer gels [82,83].…”

Section: Resultsmentioning

confidence: 99%

“…The rheology studies on the gelatin simple coacervates [30,62] gelatin-chitosan complex coacervate [11] and gelatin-A-Agar complex coacervate [63] reported in literature reveals that they are viscous in nature, while the gelatin A-gelatin-B complex coacervate [14] and gelatin-B-agar complex coacervate are viscoelastic in nature. The correlation lengths measured in gelatin simple coacervates was same as that recorded in gelatin-chitosan and gelatin-A-agar complex coacervates (≈1.2 nm) while the size of inhomogeneities ranged between 20-26 nm.…”

Section: Resultsmentioning

confidence: 99%

“…Little is known about the affect of ionic strength on such binding mechanisms which is the main focus of this work. In order to get a better feeling of the system, the results are compared with the salient features reported in gelatin simple coacervates [25,62], and gelatin A-gelatin B [14], gelatin-chitosan [11] and gelatin A-agar [63] complex coacervates. The surface selective binding process has been explained through potential energy calculations following a simple model.…”

Section: Surface Patch Bindingmentioning

confidence: 99%

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Coacervation in Biopolymers

Rawat¹

2014

J Phys Chem Biophys

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Polyelectrolyte charge; Ionic strength; Surface patch binding; Viscoelastic behavior and internal structure IntroductionCoacervation: Coacervation is a thermodynamic transition which allows a homogeneous solution of charged macroions to undergo liquidliquid phase separation, giving rise to a polymer-rich dense phase coexisting with its supernatant. These two liquid phases are immiscible but are thermodynamically compatible. The polymer-rich dense phase is often called the coacervate. Structurally it lies between the crystalline and liquid phases. Thus, it can bear intermediate range structural order and can be referred to as a mesophase. Coacervation has been mostly studied in aqueous solutions of charged synthetic or biological macromolecules in the past. In particular, protein-polysaccharide and protein-protein coacervates have attracted much attention because of their inherent potential in generating new biomaterials. In addition, such studies provide basic understanding of specific and non-specific interactions operating between complementary polyelectrolytes [1-6] or polyelectrolyte-polyampholyte [7][8][9][10][11][12][13][14][15] pairs. Normally, polysaccharides are strong polyelectrolytes whereas proteins, in addition, can be polyampholytes. Hence, the association problem reduces to that of the general study of interaction between polyelectrolyte (PE) and polyampholyte (PA) molecules [6,16]. A recent review encapsulates many of the anomalous as well as the salient features of protein-polyelectrolyte interactions [1] The phenomenon of protein based coacervates, formed of strong electrostatic interactions, has been reported for β-lactoglobulin-gum Arabic [7,8] [17]. The diversity of material properties associated with coacervates can be gauged from the fact that β-lactoglobulin-gum arabic coacervates were found to be associated with vescicular to sponge-like internal structure whereas whey protein-gum arabic coacervate was observed to be a highly concentrated (melt-like) phase. In contrast, *Corresponding author: Kamla Rawat, Special Center for Nanosciences, Jawaharlal Nehru University, New Delhi 110067, India, Tel: +91 11 2670 4699; Fax: +91 11 2674 1837; E-mail: kamla.jnu@gmail.com β-lactoglobulin-pectin coacervates were found to be a heterogeneous phase comprising of pectin networks with protein domains forming the junction points [17]. It has been shown that a polyelectrolyte, DNA and a polyampholyte, gelatin can undergo associative interaction and form complex coacervates with interesting thermal properties [15]. Further, it has been realized that in a class of systems coacervation transition is governed by surface selective patch binding even though both the polyions carry similar net charge [11,18,19]. In particular, in SPB interactions complementary polyions (normally a PA-PE pair) seek oppositely charged patches to bind overcoming the repulsion occurring between similarly charged surface patches. This is often referred to as binding on the wrong side of pH.The following provides a brief structural i...

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Structural studies of agar–gelatin complex coacervates by small angle neutron scattering, rheology and differential scanning calorimetry

Cited by 71 publications

References 41 publications

Determination of the gum Arabic–chitosan interactions by Fourier Transform Infrared Spectroscopy and characterization of the microstructure and rheological features of their coacervates

Determination of the gum Arabic–chitosan interactions by Fourier Transform Infrared Spectroscopy and characterization of the microstructure and rheological features of their coacervates

Rodlike Complexes of a Polyelectrolyte (Hyaluronan) and a Protein (Lysozyme) Observed by SANS

Coacervation in Biopolymers

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