Ovalbumin monolayers

Many macromolecules (such as proteins) form stable monolayers at the water surface if the hydrophilic-lipohilic balance (HLB) is of the right quantity. Especially, almost all proteins (hemoglobin, ovalbumin, bovine serum albumin, lactoglobulin, etc.) are reported to form stable monolayers at the water surface. 

Figure 3.48. Dilational modulus of bovine serum albumin and ovalbumin monolayers. (Courtesy of J. Benjamins).

Crosslinking of protein monolayers by mercuric ion (MacRitchie, 1970) and silicic acid (Minones et al., 1973) has been reported. These studies are relevant to poisoning by heavy-metal ions and to silicosis, effects that seem likely to result from attack on the cell membrane proteins. Crosslinking by mercuric ion was detected by a spectacular increase in surface viscosity and a decrease in compressibility when a number of proteins (BSA, insulin, ovalbumin, and hemoglobin) were spread on 0.001 M mercuric chloride solution. Poly-DL-alanine was unaffected whereas poly-L-lysine and poly-L-glutamic acid were affected in a similar manner to the proteins, indicating that mercuric ion interacts with the ionizable carboxyl and amino groups on the protein side—chains. Silicic acid similarly caused protein monolayers... 

Biological cell membranes are mainly made up of lipids and proteins. It is therefore obvious that such mixed model systems should be investigated. Mixed monolayers of hemoglobin, ovalbumin, xanthan, and virus with Mg-(stearate)2 collapsed films have been studied as LB titms on graphite. This provides a means of investigating biopolymers as found in their biological environment in the cell lipid-bilayer medium. 

In a recent study (18) on the effects of cations on the apparent yield stress of ovalbumin monolayers, we found that Zn2+ and Co2+ ions resulted in the formation of a two-dimensional network that had a lower apparent yield than that formed by Mg2+, Ca2+, Ba2+, Cu2+, Pb2+, and La3+, which are strong inactivators, formed networks that were less fluid. If it is possible to generalize from these measurements on a protein monolayer... 

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