Morphology and phase separation of hydrophobic clusters of soy globular protein polymers.
Protein hydrophobic interaction has been considered the most important factor dominating protein folding, aggregation, gelling, self-assembly, adhesion, and cohesion properties. In this paper, morphology and phase separation of hydrophobic clusters, networks, and aggregates of soy globular protein polymers, induced by using a reducing agent (NaHSO3), are studied using microscopic instruments. The morphology and phase separation of these hydrophobic clusters are sensitive to protein structure and composition, pH, and ionic-strength (I(m)). Most of the clusters are in spherical-shape architecture and mainly consist of hydrophobic polypeptides. Rod-shape clusters were also observed at higher ionic strength, and mainly consist of hydrophilic polypeptides. The ratio of hydrophobic/hydrophilic (HB/HL) polypeptides is important to facilitate the formation of clusters in an environment with a certain pH value and ionic strength. At HB/HL 0.8, uniform spherical clusters were observed and diameters ranged from 30 to 70 nm. At HB/HL <0.8, large spherical clusters were formed with diameters ranging from 100 to 1,000 nm, and at HB/HL >or=1.8, large hydrophobic aggregates formed, and size of aggregates can be up to 2 500 nm. When solid content increased from 3% to 38%, at I(m) <or= 0.058 mol x L(-1), pH = 4.8, HB/HL ratio <0.8, the networks turned into a continuous substance that has strong adhesion to various surfaces; at I(m) >or= 0.115 mol x L(-1), HB/HL ratio >or=1.8, the large aggregates became very cohesive and viscoelastic. Clear phase separation was observed during curing between hydrophobic and hydrophilic protein polymers. Phase-separation degree increased as HB/HL ratio increased.
Sun
Xiuzhi Susan
XS
Bio-Materials and Technology Laboratory, Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506, USA. xss@ksu.edu
Wang
Donghai
D
Zhang
Lu
L
Mo
Xiaoqun
X
Zhu
Li
L
Bolye
Dan
D
D001709:Biotechnology / Q000379:methods*; D004220:Disulfides; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D017510:Protein Folding; D030262:Soybean Proteins / Q000737:chemistry*; D013025:Glycine max; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D004220:Disulfides; D007477:Ions; D010455:Peptides; D011108:Polymers; D030262:Soybean Proteins; D014867:Water