Protein-modified siloxanes

Cosolvents ana Surfactants Many nonvolatile polar substances cannot be dissolved at moderate temperatures in nonpolar fluids such as CO9. Cosolvents (also called entrainers, modifiers, moderators) such as alcohols and acetone have been added to fluids to raise the solvent strength. The addition of only 2 mol % of the complexing agent tri-/i-butyl phosphate (TBP) to CO9 increases the solubility ofnydro-quinone by a factor of 250 due to Lewis acid-base interactions. Veiy recently, surfac tants have been used to form reverse micelles, microemulsions, and polymeric latexes in SCFs including CO9. These organized molecular assemblies can dissolve hydrophilic solutes and ionic species such as amino acids and even proteins. Examples of surfactant tails which interact favorably with CO9 include fluoroethers, fluoroacrylates, fluoroalkanes, propylene oxides, and siloxanes. 

Palmore presented some recent examples of simple chemistry done on the surface of proteins that can have a tremendous effect on their overall stability. Jungbae Kim and Jay Grate of Pacific Northwest National Laboratory used simple chemistry to modify lysine residues on enzyme substrates and then tethered them to siloxane, allowing it to gel and harden. This example combines chemistry, nanotechnology, and biotechnology, and shows how chemists can affect how we look at catalysts. 

The high hydrophobicity of silicones can complicate their use in some applications. For example, proteins can undergo denaturation in contact with silicones [1]. In such cases, the siloxane can be modified to include a hydrophilic domain. This is typically accomplished by functionalizing the silicone with a hydrophilic polymer such as poly(ethylene oxide)(PEO). Silicone surfactants of this type have found widespread use as stabilizers for polyurethane foams, and have been investigated as a structurant to prepare siloxane elastomers for biomaterials... 

Inventory as siloxane and silicone, silsesquioxane, a protein (albumin, casein, gelatin, gluten, hemoglobin), an enzyme, a polysaccharide (starch, cellulose, gum), rubber, or lignin. This exclusion does not apply to a polymeric substance that has been hydrolyzed, depolymerized, or otherwise chemically modified, except in cases where the intended product of this reaction is totally polymeric in structure. ... 

The reaction is not limited to amino acids but can be extended to proteins in general [27,28]. For example, hydrolyzed wheat protein can be cross-linked with siloxane chains. These products are obtained by the reaction of epoxide or anhydride groups of organo-modified polysiloxanes with amino groups of the protein. 

---