In situ measurement of conformational changes in proteins at liquid interfaces by circular dichroism spectroscopy.
A new circular dichroism (CD) spectroscopy technique for studying conformational changes in proteins in situ at the air-water interface is described. By using this technique, conformations of four proteins, viz., beta-casein, bovine serum albumin (BSA), lysozyme, and fibrinogen in the adsorbed state at the air-water interface have been studied. beta-Casein, which is predominantly in a disordered state in solution, assumes a beta-sheet conformation at the air-water interface. On the other hand, lysozyme and fibrinogen, which are alpha+beta-type proteins in solution, become beta-type proteins by completely transforming their alpha-helix structure into beta-sheets. Bovine serum albumin, which is an alpha-type protein in solution, loses its alpha-helix and becomes a disordered protein at the air-water interface. The results indicated that during unfolding and film formation at the interface, structural changes in proteins, regardless of their initial native state, follow the course of increasing beta-sheet and disordered structure and decreasing alpha-helix content. Although this seems to be the general trend, the exceptional case of BSA suggests, however, that this is not universal.
Damodaran
Srinivasan
S
Department of Food Science, University of Wisconsin-Madison, 1605 Linden Drive, Madison, WI 53706, USA. sdamodar@facstaff.wisc.edu
D000818:Animals; D002364:Caseins / Q000737:chemistry; D002417:Cattle; D002942:Circular Dichroism / Q000295:instrumentation / Q000379:methods*; D004527:Egg Proteins / Q000737:chemistry; D005340:Fibrinogen / Q000737:chemistry; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012996:Solutions / Q000737:chemistry*
D002364:Caseins; D004527:Egg Proteins; D011506:Proteins; D012996:Solutions; D012710:Serum Albumin, Bovine; D005340:Fibrinogen; D009113:Muramidase