Table 2.
Summary of interactions between ionic liquids and sites of proteins and DNA.
| Functional group on ionic liquids | Interaction with protein/DNA | References |
|---|---|---|
| Alkyl chain on cation | Hydrophobic sites on the proteins [human serum albumin (HSA), bovine serum albumin (BSA), and lipase A] and major grooves of DNA | Chandran et al., 2012; Singh et al., 2012; Nordwald et al., 2014 |
| Electron-donor substituents on cation | Disulphide linkages on protein | Liu et al., 2015 |
| Nucleophilicity of anion | Disulphide linkages, positively charged surface on protein [Candida antarctica lipase B (CAL-B)], cytochrome c (Cyt. C), DNA bases (adenine, guanine, and cytosine), and G-quadruplexes | Fujita et al., 2005; Cardoso and Micaelo, 2011; Klähn et al., 2011a; Fujita and Ohno, 2012; Liu et al., 2015 |
| Electrophilicity of cation | Phosphate groups on DNA strands and negatively charged surfaces on protein | Klähn et al., 2011a; Sarkar et al., 2020; |
| Hydroxyl group (-OH) on choline cation | Hydrogen bonding with carbonyl (C=O), imine (-N-H) and hydroxyl (OH) group on protein (e.g., collagen protein) | Tarannum et al., 2018 |
| Anionic aggregates (e.g., octylsulphate, [OS]) | Acidic sites on protein [e.g., lysozyme (tryptophan, arginine, etc.)] and hydrophobic sites on BSA | Mandal et al., 2015 |
| Cationic aggregates (e.g., 1-methyl-3-octylimidazolium cation, [Omim]+) | Hydrophobic and electrostatic interactions with carboxyl and amine functionality on BSA | Singh et al., 2012 |
| Hydrophobic cation (e.g., cyclic alkylmethylguanidinium cation [RR'GUA]+) | Hydrophobic core of protein [e.g., CAL-B, Ribonuclease A (RNase A), and α-helical protein (Im7)] | Constantinescu et al., 2007; Klähn et al., 2011b; Figueiredo et al., 2013 |
| Highly polar ionic liquid (e.g., [bmim][NO3] and [OHemim][BF4]) | Polar surfaces of protein CAL-B | Klähn et al., 2011b |
| Hydrophobic anion (e.g., [N(CN)2]−, [NTf2]−) | Hydrophobic core of RNase A | Constantinescu et al., 2007 |
| Acidic proton on cation | Negatively charged residues on protein and base-pair of DNA | Sarkar et al., 2020 |
| π-electrons on cation | NH—π interactions with DNA bases | Cardoso and Micaelo, 2011 |