Gelation of aqueous gelatin solutions. I. Structural investigation

Djabourov, Madeleine; Leblond, Jean-Baptiste; Papon, Pierre

doi:10.1051/jphys:01988004902031900

Cited by 389 publications

(344 citation statements)

References 21 publications

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“…The optical rotation measurement is mainly sensitive to the left-handed helical conformation of individual chains. Triple helix association marginally distorts the chains and has little effect on their rotatory properties (12). This is, in fact, expected because of the different length scale of this tertiary winding and its weaker interaction with light.…”

Section: Methodsmentioning

confidence: 81%

Induced helicity in biopolymer networks under stress

Courty

Gornall

Terentjev

2005

Proc. Natl. Acad. Sci. U.S.A.

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By combining dynamic mechanical and optical measurements in probing the internal structure of a biopolymer network (gelatin gel), we studied the quasi-equilibrium evolution of helical content as a function of the applied stress. Assuming that the net optical activity is proportional to the concentration of secondary helices of collagen chains, and assuming that affine mechanical deformation, we find a nonmonotonic relationship between the helical domains and an imposed deformation. The results are in qualitative agreement with theoretical predictions of ␣-helices induced by chain end-to-end stretching, and give a consistent picture of mechanically stimulated helix-coil transition in networks of denatured polypeptides.collagen ͉ helix ͉ optical rotation ͉ gelatin ͉ chirality I n recent years, a new field has emerged at the interface of physics and biology, aiming to explore structure and responses at molecular-length scales. Many single-molecule experiments have been performed to measure forces generated by biopolymers and their response to applied extension forces. The now classical work on DNA stretching (1) is just one of a number of significant recent advances in this field. By monitoring the response of a single molecule to pulling and twisting its ends [using atomic force microscopy (AFM), and magnetic trap and optical tweezer methods (2, 3)], one can probe the question of how chiral biopolymers are held in their native state, and their pathways of folding and unfolding. However, although the current techniques used in single-molecule force experiments reveal spectacular force-extension curves, they give little direct information about the structural transitions that occur on extension of these chains. Theoretical modeling of the behavior of single biopolymer molecules on extension has been hampered by this lack of information concerning structural changes. Using a new macroscopic approach of combining mechanical and optical methods in probing the internal structure of the biopolymer network, we found a direct relationship between helical domains and an externally imposed end-to-end distance of chains.Certain homopolypeptides form regular ␣-helices under appropriate conditions. In this case, the molecular configurations are well understood and are described according to the ZimmBragg model (4) [and its many modifications (5)], which assumes that each chain segment has access to only two conformational states, the random-coil state and the helical state. The average helical fraction of the chain can then be calculated for any number of model interactions between these two states. Although the two-state model of polypeptides has a lot of support, especially revealed in the Ramachandran plots, showing that peptide backbone has two well separated states corresponding to the ␣-helix and the ␤-sheet (the high-temperature denatured coil being the random mixing between the two), from the fieldtheoretical point of view, it is desirable to have a continuum model of chain conformation, as a function of interaction pot...

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Section: Methodsmentioning

confidence: 81%

Induced helicity in biopolymer networks under stress

Courty

Gornall

Terentjev

2005

Proc. Natl. Acad. Sci. U.S.A.

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“…This implies that the water contribution is dominated by intermolecular dipole couplings, which could be the case if the internal water molecules undergo large-amplitude internal motions that reduce S intra more than S inter (35). The internal water molecules responsible for the high-frequency 1 H and 2 H dispersions are presumably associated with structural defects and branch points in the gel network (21,22).…”

Section: Model Parameters Describing 1 H Mrd Profiles From Gelatin Gelsmentioning

confidence: 99%

“…Aqueous solutions of gelatin, produced by partial hydrolysis of collagen, undergo a sol-gel transition at ϳ25°C (21). Gelatin gels are built from collagen-like triple-helical junction zones, 100 -200 residues in length, connected by flexible single chains (22).…”

mentioning

confidence: 99%

Molecular basis of water proton relaxation in gels and tissue

Chávez

Halle

2006

Magnetic Resonance in Med

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An extensive set of water-1 H magnetic relaxation dispersion (MRD) data are presented for aqueous agarose and gelatin gels. It is demonstrated that the EMOR model, which was developed in a companion paper to this study (see Halle, this issue), accounts for the dependence of the water-1 H spin-lattice relaxation rate on resonance frequency over more than four decades and on pH. The parameter values deduced from analysis of the 1 H MRD data are consistent with values derived from 2 H MRD profiles from the same gels and with small-molecule reference data. This agreement indicates that the water-1 H relaxation dispersion in aqueous biopolymer gels is produced directly by exchange-mediated orientational randomization of internal water molecules or labile biopolymer protons, with little or no role played by collective biopolymer vibrations or coherent spin diffusion. This ubiquitous mechanism is proposed to be the principal source of water-1 H spin-lattice relaxation at low magnetic fields in all aqueous systems with rotationally immobile biopolymers, including biological tissue. The same mechanism also contributes to transverse and rotating-frame relaxation and magnetization transfer at high fields. Intrinsic contrast in magnetic resonance images of soft tissue is generated largely by spatial variations in spin relaxation rates. Whereas the phenomenology of water-1 H relaxation in tissue is well documented (1-3), the underlying molecular mechanism remains controversial (4 -9). The task of elucidating the relaxation mechanism is complicated by incomplete knowledge about the chemical composition and supramolecular structure of most tissues. In addition, it is usually not possible to vary biopolymer composition, pH, or temperature in a controlled way while maintaining the integrity of the tissue. For these reasons, most mechanistic studies have been carried out on model systems, such as aqueous biopolymer gels, with relaxation characteristics similar to those of tissue. Here we report an extensive set of water-1 H relaxation data from two widely used tissue models: aqueous gels of agarose and gelatin.Detailed information about relaxation mechanisms in complex systems can be obtained from the magnetic relaxation dispersion (MRD) profile, that is, the field/frequency dependence of the spin-lattice relaxation rate, R 1 ϭ 1/T 1 . Ideally, the dispersion profile should be recorded from typical MRI frequencies of order 100 MHz down to the kHz range. The water-1 H MRD profiles reported here cover more than four frequency decades. The strong frequency dependence of R 1 at low fields, which is the focus of the present study, can be used to enhance image contrast in prepolarized MRI experiments (10). The low-field R 1 dispersion also yields information about the zero-frequency dipolar contributions to transverse relaxation and steadystate magnetization transfer and to the low-frequency dipolar contribution to rotating-frame spin-lattice relaxation.Agarose is a linear polysaccharide with a disaccharide repeat (agarobiose) composed...

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“…Gelatin is a highly versatile biopolymer which can be obtained at a range of isoelectric points, molecular weights and gel strengths 29 and has been used in a plethora of biomedical devices, pharmaceuticals and tissue engineering applications for over fifty years [30][31][32][33][34][35][36][37][38][39][40][41][42] . Without cross-linking, gelatin hydrogels are very weak and readily dissolve at temperatures above 29˚C which would prohibit their use in tissue engineering 43,44 . However, covalent cross-linking with genipin significantly improves the mechanical performance and stability of gelatin hydrogels 47,48 .…”

Section: Introductionmentioning

confidence: 99%

Robust biopolymer based ionic–covalent entanglement hydrogels with reversible mechanical behaviour

Kirchmajer

Panhuis

2014

J. Mater. Chem. B

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Robust biopolymer based ionic-covalent entanglement hydrogels with reversible mechanical behaviour AbstractEmerging applications of hydrogels such as soft robotics and cartilage tissue scaffolds require hydrogels with enhanced mechanical performance. We report the development of a robust biopolymer based ionic-covalent entanglement network hydrogel made from calcium cross-linked gellan gum and genipin cross-linked gelatin. The ratio of the two polymers and the cross-linker concentrations significantly affected the mechanical characteristics of the hydrogels. Hydrogels with optimized composition exhibited compressive fracture stress and work of extension values of up to 1.1 ± 0.2 MPa and 230 ± 40 kJ m−3 for swelling ratios of 37.4 ± 0.6 and 19 ± 1, respectively. The compressive and tensile mechanical properties, swelling behavior (including leachage), pH sensitivity and homogeneity are discussed in detail. Fully swollen hydrogels (swelling ratio of 37.4 ± 0.6) were able to recover 95 ± 2% and 82 ± 7% of their energy dissipation (hysteresis) at 37 °C after reloading to either constant stress (150 kPa) or constant strain (50%), respectively. Emerging applications of hydrogels such as soft robotics and cartilage tissue scaffolds require hydrogels with enhanced mechanical performance. We report the development of a robust biopolymer based ionic-covalent entanglement network hydrogel made from calcium cross-linked gellan gum and genipin cross-linked gelatin. The ratio of the two polymers and the cross-linker concentrations significantly affected the mechanical characteristics of the hydrogels. Hydrogels with optimized composition exhibited compressive fracture stress and work of extension values of up to 1.1 ± 0.2 MPa and 230 ± 40 kJ.m -3 for swelling ratios of 37.4 ± 0.6 and 19 ± 1, respectively. The compressive and tensile mechanical properties, swelling behavior (including leachage), pH sensitivity and homogeneity are discussed in detail. Fully swollen hydrogels (swelling ratio of 37.4 ± 0.6) were able to recover 95 ± 2% and 82 ± 7% of their energy dissipation (hysteresis) at 37 °C after reloading to either constant stress (150 kPa) or constant strain (50%), respectively.

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Gelation of aqueous gelatin solutions. I. Structural investigation

Cited by 389 publications

References 21 publications

Induced helicity in biopolymer networks under stress

Induced helicity in biopolymer networks under stress

Molecular basis of water proton relaxation in gels and tissue

Robust biopolymer based ionic–covalent entanglement hydrogels with reversible mechanical behaviour

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