REVIEW
Interaction of proteins with ionic liquid, alcohol and DMSO
and in situ generation of gold nano-clusters in a cell
Somen Nandi
1
&
Sridip Parui
1
&
Ritaban Halder
1
&
Biman Jana
1
&
Kankan Bhattacharyya
1,2
Received: 24 September 2017 /Accepted: 23 October 2017 /Published online: 16 November 2017
#
International Union for Pure and Applied Biophysics (IUPAB) and Springer-Verlag GmbH Germany 2017
Abstract In this review, we give a brief overview on how the
interaction of proteins with ionic liquids, alcohols and dimeth-
yl sulfoxide (DMSO) influences the stability, conformational
dynamics and function of proteins/enzymes. We present ex-
perimental results obtained from fluorescence correlation
spectroscopy on the effect of ionic liquid or alcohol or
DMSO on the size (more precisely, the diffusion constant)
and conformational dynamics of lysozyme, cytochrome c
and human serum albumin in aqueous solution. The interac-
tion of ionic liquid with biomolecules (e.g. protein, DNA etc.)
has emerged as a current frontier. We demonstrate that ionic
liquids are excellent stabilizers of protein and DNA and, in
some cases, cause refolding of a protein already denatured by
chemical denaturing agents. We show that in ethanol–water
binary mixture, proteins undergo non-monotonic changes in
size and dynamics with increasing ethanol content. We also
discuss the effect of water–DMSO mixture on the stability of
proteins. We demonstrate how large-scale molecular dynam-
ics simulations have revealed the molecular origin of this ob-
served phenomenon and provide a microscopic picture of the
immediate environment of the biomolecules. Finally, we de-
scribe how favorable interactions of ionic liquids may be
utilized for in situ generation of fluorescent gold nano-
clusters for imaging a live cell.
Keywords Binary mixture
.
Conformational dynamics
.
Folding/unfolding
.
Ionic liquid
.
MD simulation
Introduction
A room temperature ionic liquid (RTIL) consists of a bulky
organic ion (cation) and a small inorganic counter ion (anion).
Interactions of RTILs among each other and with other small
and large biomolecules are currently attracting great interest
because of the widespread applications of RTILs in green
chemistry and electrochemistry, as well as for their ability to
impart stability and long-term storage of proteins, enzymes
and nucleic acids (e.g. DNA) (Baker et al. 2004;Benedetto
and Ballone 2016; Chandran et al. 2012; Egorova et al. 2017;
Fujita et al. 2007;Sahaetal.2016; Watanabe et al. 2017). The
interaction of an ionic liquid with a biomolecule or a drug
involves both electrostatic (through the ionic part of RTILs)
and hydrophobic actions (with long-chain organic moieties of
RTILs). Ionic liquids have also been demonstrated to enhance
efficacy of traditional drugs and thereby has opened up new
avenue in drug research (Egorova et al. 2017).
The interaction of RTIL with biomolecules has been stud-
ied quite extensively by X-ray and neutron scattering tech-
niques. Neutron scattering experiments provide a microscopic
picture of the interactions of ionic liquids with phospholipids,
peptides/proteins and nucleic acids (e.g. DNA) (reviewed
recently by Benedetto and Ballone 2016). These studies and
the accompanying molecular dynamics (MD) simulations
have examined the relative contribution of columbic interac-
tion and other weak interactions such as dispersion, hydrogen
bonds, steric effects etc. Microscopic details, such as the
This article is part of a special issue on ‘Ionic Liquids and Biomolecules’
edited by Antonio Benedetto and Hans-Joachim Galla
* Biman Jana
pcbj@iacs.res.in
* Kankan Bhattacharyya
kankan.bhattacharyya@gmail.com
1
Department of Physical Chemistry, Indian Association for the
Cultivation of Science, Jadavpur, Kolkata 700 032, India
2
Department of Chemistry, Indian Institute of Science Education and
Research Bhopal, Bhopal, Madhya Pradesh 462 066, India
Biophys Rev (2018) 10:757–768
https://doi.org/10.1007/s12551-017-0331-1
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