jp6b00536_si_001.pdf (487.41 kB)
Adsorption and Unfolding of Lysozyme at a Polarized Aqueous–Organic Liquid Interface
journal contribution
posted on 2016-03-07, 00:00 authored by Mahreen Arooj, Neha S. Gandhi, Cara A. Kreck, Damien
W. M. Arrigan, Ricardo L. ManceraThe adsorption of proteins at the
interface between two immiscible
electrolyte solutions has been found to be key to their bioelectroactivity
at such interfaces. Combined with interfacial complexation of organic
phase anions by cationic proteins, this adsorption process may be
exploited to achieve nanomolar protein detection. In this study, replica
exchange molecular dynamics simulations have been performed to elucidate
for the first time the molecular mechanism of adsorption and subsequent
unfolding of hen egg white lysozyme at low pH at a polarized 1,2-dichloroethane/water
interface. The unfolding of lysozyme was observed to occur as soon
as it reaches the organic–aqueous interface, which resulted
in a number of distinct orientations at the interface. In all cases,
lysozyme interacted with the organic phase through regions rich in
nonpolar amino acids, such that the side chains are directed toward
the organic phase, whereas charged and polar residues were oriented
toward the aqueous phase. By contrast, as expected, lysozyme in neat
water at low pH does not exhibit significant structural changes. These
findings demonstrate the key influence of the organic phase upon adsorption
of lysozyme under the influence of an electric field, which results
in the unfolding of its structure.