Protein substitution affects glass transition temperature and thermal stability.
When proteins are removed from their native state they suffer from two deficiencies: (1) glassy behavior with glass transition temperatures (Tg) well above room temperature and (2) thermal instability. The glassy behavior originates in multiple hydrogen bonds between amino acids on adjacent protein molecules. Proteins, like most biopolymers, are thermally unstable. Substituting ovalbumin with linear and cyclic substituents using a facile nucleophilic addition reaction can affect Tg and thermal stability. More hydrophobic linear substituents lowered Tg by interrupting intermolecular interactions and increasing free volume. More hydrophilic and cyclic substituents increased thermal stability by increasing intermolecular interactions. In some cases, substituents instituted cross-linking between protein chains that enhanced thermal stability. Internal plasticization using covalent substitution and external plasticization using low molecular weight polar liquids show the same protein structural changes and a signature of plasticization is identified.
Budhavaram
Naresh K
NK
Biological Systems Engineering Department, Virginia Tech, Blacksburg, Virginia 24061, USA.
Miller
Jonathan A
JA
Shen
Ying
Y
Barone
Justin R
JR
D005898:Glass; D006860:Hydrogen Bonding; D011506:Proteins / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014961:X-Ray Diffraction
D011506:Proteins