The adsorbed conformation of globular proteins at the air/water interface

Abstract

External reflection FTIR spectroscopy and surface pressure measurements were used to compare conformational changes in the adsorbed structures of three globular proteins at the air/water interface. Of the three proteins studied, lysozyme, bovine serum albumin and beta-lactoglobulin, lysozyme was unique in its behaviour. Lysozyme adsorption was slow, taking approximately 2.5 h to reach a surface pressure plateau (from a 0.07 mM solution), and led to significant structural change. The FTIR spectra revealed that lysozyme formed a highly networked adsorbed layer of unfolded protein with high antiparallel beta-sheet content and that these changes occurred rapidly (within 10 min). This non-native secondary structure is analogous to that of a 3D heat-set protein gel, suggesting that the adsorbed protein formed a highly networked interfacial layer. Albumin and beta-lactoglobulin adsorbed rapidly (reaching a plateau within 10 min) and with little change to their native secondary structure.

Effect of sodium dodecyl sulfate on dynamic surface properties of lysozyme solutions

“…2). This finding agrees with the conclusion [3] that the insufficient reproducibility of nonequilibrium surface properties of lysozyme solutions is due to the peculiarities of macromolecule transfer from bulk phases to surfaces rather than the processes taking place in surface layers. The addition of even small amounts of SDS (up to 0.0005 mM) to lysozyme substantially improved the reproducibility of the kinetic dependences for the surface properties, and, in this case, the reproducibility was governed by the measurement error.…”

“…The degree of the breakage of the globular structure of proteins upon their adsorption on a liquid surface is still intensely discussed [1][2][3][4][5][6][7][8][9][10][11]. Although the main stages of many processes in living organisms occur at interfaces and protein adsorption layers stabilize vari ous natural and industrial disperse systems, informa tion on variations in the tertiary and secondary struc tures of proteins during adsorption is extremely scarce.…”

“…Although the main stages of many processes in living organisms occur at interfaces and protein adsorption layers stabilize vari ous natural and industrial disperse systems, informa tion on variations in the tertiary and secondary struc tures of proteins during adsorption is extremely scarce. While the mechanisms of unfolding protein globules in bulk phases have been studied in detail [12], in the case of surface layers, different authors give directly opposite answers even to the main question concern ing breaking or retaining the tertiary structure of pro teins upon adsorption [1][2][3][4][5][6][7].…”

Unexpected differences in the behavior of ovotransferrin at the air–water interface at pH 6.5 and 8.0

“…Numerous data are available about the kinetics and thermodynamics of protein adsorption, as provided by surface tension measurements, ellipsometry and radiolabelling techniques [16][17][18][19][20][21]. The interfacial behavior of globular proteins (lysozyme, b-lactoglobulin, bovine serum albumin, ovalbumin) has been extensively studied at the air-water interface [17,[21][22][23][24][25][26]. However the kinetics of ovotransferrin adsorption at the air-water interface and the influence of bulk protein concentration on the kinetics have not been investigated in a specific way.…”

Current Issues in Measurement and Reporting of Urinary Albumin Excretion

“…Binding to surfaces also results in some denaturation, and both adsorption and denaturation can be reduced when a suitable hydrophilic surface is used or nonionic detergent added (39,40 ). Albumin appears to be relatively stable at the air-liquid interface when foaming is generated by rapid mixing (41 ).…”