Ionic Liquid Surfactant Mediated Structural Transitions and Self-Assembly of Bovine Serum Albumin in Aqueous Media: Effect of Functionalization of Ionic Liquid Surfactants

Abstract

The self-assembly of globular protein bovine serum albumin (BSA) has been investigated in aqueous solutions of ionic liquid surfactants (ILSs), 1-dodecyl-3-methyl imidazolium chloride, [C12mim][Cl], and its amide, [C12Amim][Cl], and ester, [C12Emim][Cl], functionalized counterparts. Dynamic light scattering (DLS) has provided insights into the alterations in hydrodynamic radii (D(h)) of BSA as a function of concentration of ILSs establishing the presence of different types of BSA-ILS complexes in different concentration regimes of ILSs. Isothermal titration calorimetry (ITC) has been exploited to quantify the ILSs interacting with BSA in dilute concentration regime of ILSs. The zeta-potential measurements shed light on changes in the charged state of BSA. The morphology of various self-assembled structures of BSA in different concentration regimes of ILSs have been explored using confocal laser scanning microscopy (CLSM) and scanning electron microscopy. The structural variations in ILSs have been found to produce remarkable effect on the nature and morphology of self-assembled structures of BSA. The presence of nonfunctionalized [C12mim][Cl] IL at all investigated concentrations has led to the formation of unordered large self-assembled structures of BSA. On the other hand, in specific concentration regimes, ordered self-assembled structures such as long rods and right-handedly twisted helical amyloid fibers have been observed in the presence of functionalized [C12Amim][Cl] and [C12Emim][Cl] ILSs, respectively. The nature of the formed helical fibers as amyloid ones has been confirmed using FTIR spectroscopy. Steady-state fluorescence and circular dichroism (CD) spectroscopy have provided insights into folding and unfolding of BSA as fashioned by interactions with ILSs in different concentration regimes supporting the observations made from other studies.

Aqueous colloidal systems of bovine serum albumin and functionalized surface active ionic liquids for material transport

“…The globular structure of BSA possess 56% a-helical and 11% b-sheet content. 7,8 BSA can reversibly adopt various spatial conformations at different pH values such as N-isoform at pH 7.4 (heartlike shape), F-isoform at pH 3.5 (cigar-like shape) and E-isoform at pH 2.7 (denatured form). 9,10 The exceptional stability among other proteins such as long shelf-life (about 19 days), stability towards high temperature (at 60 C up to 10 hours) and in a wide pH range (pH 4 to 9) along with reversible binding ability towards a variety of bioactive molecules and active pharmaceutical ingredients (APIs) make BSA a robust and imperative protein for physiological investigations.…”

“…8,[46][47][48][49][50][51][52][53][54][55][56][57] Different proteins such as BSA, Gelatin and blactoglobulin (b-LG) has been investigated for their complexation with SAILs, where the length of alkyl chain and nature of head group of SAIL has been found to exert signicant inuence on complexation behavior of BSA with SAILs. 8,[46][47][48][49]56,57 It is stressed that in most of the investigations, SAILs without any functionalization of ionic head group or alkyl chain have been employed with the exception of few studies. 8,46,48 A contrasting complexation behavior of functionalized SAILs as compared to non-functionalized ones towards BSA, 8 Gelatin 48 and b-lactoglobulin (b-LG) 46 has been observed.…”

“…8,[46][47][48][49]56,57 It is stressed that in most of the investigations, SAILs without any functionalization of ionic head group or alkyl chain have been employed with the exception of few studies. 8,46,48 A contrasting complexation behavior of functionalized SAILs as compared to non-functionalized ones towards BSA, 8 Gelatin 48 and b-lactoglobulin (b-LG) 46 has been observed. Different types of SAILprotein complexes varying in morphology, internal structure and hydrophobicity etc., governed by the nature and extent of varying set of interactions has been observed.…”

Polymerization of 1‐(2‐Propynyl)‐3‐methylimidazolium Bromide using Cyclometalated Pd(II) Catalysts and Study of the Interaction of Ensuing Oligomer with BSA

“…The secondary structure of BSA mainly consists of α‐helix, β‐sheet and random coiling. Two negative bands of BSA at 208 and 222 nm corresponding to its α‐helical structure gradually decreased with increasing amount of oligomer 2 as shown in Figure ,,. The α‐helix content decreased from 63.62 % to 30.77 %, whereas the corresponding β‐sheet content increased from 9.48 % to 17.32 % (Table , calculated using web interface of k2d3 program).…”

A comparative study on intrinsic fluorescence of BSA and lysozyme proteins in presence of different divalent ions from their solution and thin film conformations

“…emission from tryptophan modifies due to interactions between protein molecules and surfactant that change the microenvironment around tryptophan. [18,19] Fluorescence quenching from proteins is also possible in the presence of charged polymers, nanoparticles, etc. Hence, protein conformational changes can be indirectly monitored using tryptophan fluorescence emission spectra.…”