The behavior of the model proteins, lysozyme, myoglobin, and that proteins with only weak forces maintaining the tertiary b-casein, pretreated in urea and/or dithiothreitol, at air/solution structure have a higher probability of unfolding. Krebs et interfaces was studied by surface pressure-area techniques. The al. (10) found that the steady state surface activity depends data suggested that in the absence of pretreatments the globular on the content of nonpolar residues, without regard for the proteins are only partially unfolded at the interfaces. The interfadetails of the secondary and tertiary structures. Norde et al.
cial activity was enhanced by the pretreatment (lysozyme in 8 M (11) discussed the structural rearrangements of a protein at urea with 0.2 M dithiothreitol and myoglobin in 8 M urea). The the interfaces in terms of its structural stability in solution, interfacial activity of casein, a random-coil type protein, was not its ''softness'' or ''hardness''; a soft protein rearranges or influenced by the pretreatment (8 M urea), as it readily and completely unfolds at the interfaces. The unfolding of globular proteins denatures more easily than a hard protein. Andrade et al. (5) at the interfaces is apparently restricted by both disulfide and also examined various parameters correlating the behavior of noncovalent bonds. Pretreatment can relax those restrictions, reproteins at interfaces and in solution, including denaturation sulting in more complete interfacial unfolding.