la8b01974_si_001.pdf (1.24 MB)
Bilirubin Oxidase Adsorption onto Charged Self-Assembled Monolayers: Insights from Multiscale Simulations
journal contribution
posted on 2018-07-25, 00:00 authored by Shengjiang Yang, Jie Liu, Xuebo Quan, Jian ZhouThe
efficient immobilization and orientation of bilirubin oxidase
(BOx) on different solid substrates are essential for its application
in biotechnology. The T1 copper site within BOx is responsible for
the electron transfer. In order to obtain quick direct electron transfer
(DET), it is important to keep the distance between the T1 copper
site and electrode surface small and to maintain the natural structure
of BOx at the same time. In this work, the combined parallel tempering
Monte Carlo simulation with the all-atom molecular dynamics simulation
approach was adopted to reveal the adsorption mechanism, orientation,
and conformational changes of BOx from Myrothecium verrucaria (MvBOx) adsorbed on charged self-assembled monolayers (SAMs), including
COOH-SAM and NH2-SAM with different surface charge densities
(±0.05 and ±0.19 C·m–2). The results
show that MvBOx adsorbs on negatively charged surfaces with a “back-on”
orientation, whereas on positively charged surfaces, MvBOx binds with
a “lying-on” orientation. The locations of the T1 copper
site are closer to negatively charged surfaces. Furthermore, for negatively
charged surfaces, the T1 copper site prefers to orient closer to the
surface with lower surface charge density. Therefore, the negatively
charged surface with low surface charge density is more suitable for
the DET of MvBOx on electrodes. Besides, the structural changes primarily
take place on the relatively flexible turns, coils, and α-helix.
The native structure of MvBOx is well preserved when it adsorbs on
both charged surfaces. This work sheds light on the controlling orientation
and conformational information on MvBOx on charged surfaces at the
atomistic level. This understanding would certainly promote our understanding
of the mechanism of MvBOx immobilization and provide theoretical support
for BOx-based bioelectrode design.