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Gelation of a Model Globular Protein
Author(s) -
Yan Hui,
Saiani Alberto,
Miller Aline F.
Publication year - 2007
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200750515
Subject(s) - globular protein , dithiothreitol , environmental scanning electron microscope , denaturation (fissile materials) , lysozyme , microstructure , chemical engineering , transmission electron microscopy , scanning electron microscope , fibril , chemistry , viscoelasticity , viscosity , materials science , polymer chemistry , crystallography , nuclear chemistry , organic chemistry , composite material , biochemistry , enzyme , engineering
Hen egg white lysozyme (HEWL) was exposed to various physical and chemical denaturing environments to encourage protein denaturation and consequent gelation. Its phase behavior was examined as a function of pH, temperature and also in the presence of the reductant dithiothreitol (DTT). Transparent viscoelastic gels form at low pH values while opaque gels form under alkaline conditions. No increase in viscosity was observed for systems in pure water unless 20 mM of DTT was added, which is known to break the disulfide bridges present in HEWL. The microstructure of the gel was studied using transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM). Gels formed at low pH contain fibrils ∼10 nm in diameter with various lengths while at high pH the gels are dominated by particulate aggregates. Thinner fibrils that are 4–6 nm in diameter are observed in the gels formed in the presence of DTT. In this case the distinct feature of the gels is they are thermoreversible and can be melted and reformed easily by varying the temperature.