Liquid Crystalline Gelation of Aqueous Solutions of Structure Proteins

Structure formation in biopolymer gels induced by diffusion of gelling factors

“…(2) Chemical crosslinkers [32]: covalent bonds created by the reaction between the crosslinker molecules and the polymer chains act as junction zones of gel network. (3) pH conditioners [20,[32][33][34][35][36][37][38][39][40][41][42][43][44]: solubility of weak polyelectrolytes depends strongly on pH of the solution. When acidic or alkaline solutions of weak polyelectrolytes are neutralized by pH conditioners, the polymer chains are insolubilized and form aggregates, resulting in the gel formation.…”

“…Collagen, gelatin, and other proteins / polypeptides [32,[40][41][42][43][44] Collagen is the principal protein consisting of fibrous connective tissues such as skin and tendon [58]. Collagen is soluble in aqueous acidic solution; the neutralization of the collagen acidic solution induces the formation of collagen fibrils, resulting in gelation [58].…”

“…Collagen is soluble in aqueous acidic solution; the neutralization of the collagen acidic solution induces the formation of collagen fibrils, resulting in gelation [58]. When the collagen acidic solution was neutralized by the contact of the collagen solution with a neutral buffer solution, optically anisotropic collagen gels were obtained [32,40,41]. The molecular orientation in the anisotropic gel was confirmed to be perpendicular to the gelation direction by birefringence, small-angle light scattering, and confocal laser scanning microscopy (CLSM) experiments [40].…”

“…Aqueous gelation solutions form thermo-reversible gels; gelatin is water soluble and assumes a random-coil conformation at high temperatures, typically above 40°C, but in decreasing temperature, gelatin is assembled with each other to form junction zones with a collagen-like helical conformation, which eventually results in the gel network formation [60]. When gelatin solutions at temperatures ranging from 40°C to 10°C were chemically crosslinked under the diffusion of a chemical-crosslinker glutaraldehyde by the sandwich method, optically anisotropic gels were obtained [32].…”

“…There were some other protein or polypeptide systems which also form optically anisotropic gels in the gelation induced by the diffusion of gelling factors. In this review, for brevity, only the sets of the protein or polypeptide and the gelling factor are listed as follows: myosin and glutaraldehyde [32]; silk fibroin and ethanol [32]; polyglutamate and Al 3+ [61].…”