Multilayers of a globular protein and a weak polyacid: role of polyacid ionization in growth and decomposition in salt solutions.
Thin films obtained from a layer-by-layer deposition of a weak polycarboxylic acid and a positively charged globular protein were studied by in situ ATR-FTIR. The system was chicken egg lysozyme (Lys), bovine pancrease ribonuclease A (RNase), or bovine gamma-globulin (IgG) self-assembled with polycarboxylic acids. When the pH value was lowered below a critical point, the growth of films and their tolerance to decomposition by added sodium chloride improved dramatically. Stabilization of protein/polyacid films in salt solutions at lower pH values occurred due to the onset of nonelectrostatic interactions to intermolecular binding within protein/polyacid multilayers and was controlled by polyacid ionization within the film rather than the pH of the external solution. A fractional ionization of polyacid in the pH-stabilization region was lower with protein-containing films than for polyacid/linear polycation films, reflecting hindrance of the inter-association of protonated carboxylic groups by protein globules. Practical ramifications of the pH-stabilization effect might extend to areas of biotechnology and biomaterials.
Izumrudov
Vladimir A
VA
Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
Kharlampieva
Eugenia
E
Sukhishvili
Svetlana A
SA
D000143:Acids; D000818:Animals; D002264:Carboxylic Acids / Q000737:chemistry*; D002417:Cattle; D002645:Chickens; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D012492:Salts; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions
D000143:Acids; D002264:Carboxylic Acids; D011506:Proteins; D012492:Salts; D012996:Solutions; D012965:Sodium Chloride