Room Temperature Ionic Liquids Meet Biomolecules: A Microscopic View of Structure and Dynamics

Abstract

Room temperature ionic liquids (RTILs) and biomolecules are both paradigmatic classes of organic molecules, each consisting of a prodigious number of distinct chemical species, organized into large families of homologous compounds. Their combination is set to open new avenues for discoveries and for applications in biochemistry, biomedicine and pharmacology, food science, and nanotechnology. We provide a survey of past and current investigations of the chemical physics properties of systems made of RTILs and biomolecules, focusing on the most microscopic scales of their structure and dynamics. The primary goal of our discussion is to identify the basic principles able to organize and rationalize the vast variety of properties and phenomena displayed by these systems. We consider in turn RTILs combinations with phospholipids, with proteins and peptides, with nucleic acids (mainly DNA) and with carbohydrates from simple sugars to large polysaccharides. These basic components have a clear electrostatic signature, and Coulomb interactions represent the first ordering principle. However, because of size and complexity of both RTILs and biomolecules, dispersion interactions, steric effects, and hydrogen bonding play a secondary but certainly nonnegligible role that is reflected in the sensitive dependence of RTIL/biomolecule properties on the RTIL choice. Our overview of the available results highlights both the need and the difficulty of devising general approaches able to predict properties of at least extended families of RTIL/biomolecules combinations, without having to consider them one by one in turn.

Interaction studies of cholinium-based ionic liquids with calf thymus DNA: Spectrophotometric and computational methods

“…Since ILs have both organic/inorganic nature and high polarity, it has strong tendency to permeate through the cellular and other membranes and interact with biomolecules [19,20]. This is quite a serious concern and may cause long-term causalities to the animals and human beings.…”

“…This is quite a serious concern and may cause long-term causalities to the animals and human beings. To predict toxicity and possible fate of an IL inside a human body, several studies have been undertaken using different biomolecules [19,20]. In majority of the studies, researcher used DNA because it is a primary target of many carcinogens and a slight change in its function may lead to deadly diseases like cancer.…”

Temperature‐dependent molecular dynamics study reveals an ionic liquid induced 310‐ to α‐helical switch in a neurotoxin

“…Especially, the IL anions having high H‐bond basicity often significantly interfere with the native protein structure, by tempering the existing H‐bond networks . In a recent report, Benedetto et al comprehensively reviewed the current status of bio‐molecular solvation by ILs . The consequence of solvating a given protein in a specific IL is quite difficult to envisage, owing to the innumerable possible combinations of IL cations and anions and their specific/general interactions with the protein molecule.…”

“…Franz Hofmeister, in his seminal work showed that ions have differential abilities to salt‐in or salt‐out proteins from solutions and can be ordered into a series called “Hofmeister series.” Remarkably, the same Hofmeister trend of ions tends to affect disparate phenomena related to the structural stability, function and solubility of biomolecules and thermal degradation. The salting‐out phenomenon, in fact, is a measure of the tendency of proteins to correct folding and relative ordering, while enhanced solubilization with salting‐in effect might be an indication of unfolding leading to subsequent aggregation and fibril formation . Initially, it was believed that the salts have either kosmotropic or chaotropic abilities, which could alter the structure of the essential water around the biomolecules, thereby affecting its solubility .…”

“…In fact, for ILs, both the cation and anion are important in regulating the final effect on the protein. The neutral and flexible hydrocarbon tails of the substituted imidazolium cations have strong hydrophobic character, which particularly interferes with protein stability and correct folding . In the present report, we have studied the IL, [Im 41 ][Cl], where the large organic cation (1‐butyl‐3‐methylimidazolium) is efficient in salting‐in of proteins, that is, have denaturing ability.…”