Role of macromolecular crowding and salt ions on the structural-fluctuation of a highly compact configuration of carbonmonoxycytochrome c

Analysis of the effect of 1-Allyl-3-Methylimidazolium chloride on thermodynamic stability, folding kinetics, and motional dynamics of horse cytochrome c

1-allyl-3-methylimidazolium chloride (AMIMCl) acts as a potential green solvent for proteins. The present work provides a possible pathway by which the structural, kinetic, thermodynamic, and folding properties of horse cytochrome c (cyt c) are affected in green aqueous-AMIMCl systems. Analysis of the effect of AMIMCl on thermodynamic stability, refolding/unfolding kinetics, and motional dynamics of cyt c provided important information, (i) AMIMCl decreases the thermodynamic stability of reduced cyt c and also strengthens the guanidinium chloride (GdmCl)-mediated decrease in thermodynamic stability of protein, (ii) AMIMCl reduces the thermal-fluctuation of Met80-containing omega-loop of natively-folded compact state of carbonmonoxycytochrome c (MCO-state) due to polyfunctional interactions between the AMIM⁺ and different groups of protein, (iii) AMIMCl shifts the kinetic chevron plot, ln k_obs[GdmCl] to the lower concentration of GdmCl, (iv) AMIMCl shifts the refolding and unfolding limps to vertically downwards and upwards, respectively, and (v) AMIMCl reducing the unfolding free energy estimated by both thermodynamic and kinetic analysis.

It is time to crowd your cell culture media - Physicochemical considerations with biological consequences

In vivo, the interior and exterior of cells is populated by various macromolecules that create an extremely crowded milieu. Yet again, in vitro eukaryotic cell culture is conducted in dilute culture media that hardly imitate the native tissue density. Herein, the concept of macromolecular crowding is discussed in both intracellular and extracellular context. Particular emphasis is given on how the physicochemical properties of the crowding molecules govern and determine kinetics, equilibria and mechanism of action of biochemical and biological reactions, processes and functions. It is evidenced that we are still at the beginning of appreciating, let alone effectively implementing, the potential of macromolecular crowding in permanently differentiated and stem cell culture systems.

Bioinspired in vitro microenvironments to control cell fate: focus on macromolecular crowding

The development of therapeutic regenerative medicine and accurate drug discovery cell-based products requires effective, with respect to obtaining sufficient numbers of viable, proliferative, and functional cell populations, cell expansion ex vivo. Unfortunately, traditional cell culture systems fail to recapitulate the multifaceted tissue milieu in vitro, resulting in cell phenotypic drift, loss of functionality, senescence, and apoptosis. Substrate-, environment-, and media-induced approaches are under intense investigation as a means to maintain cell phenotype and function while in culture. In this context, herein, the potential of macromolecular crowding, a biophysical phenomenon with considerable biological consequences, is discussed.

Effect of imidazolium based ionic liquids on CO-association dynamics and thermodynamic stability of Ferrocytochrome c

Analysis of kinetic and thermodynamic parameters measured for CO-association reaction of Ferrocytochrome c (Ferrocyt c) under variable concentrations of 1-butyl-3-methylimidazolium with varying anion ([Bmim]X) (X = Cl^-, I^-, Br^-, HSO₄^-) at pH 7 revealed that the low concentration of [Bmim]X (≤0.5 M) constrains the CO-association dynamics of Ferrocyt c and typically follows the order: [Bmim]HSO₄ > [Bmim]Cl > [Bmim]Br > [Bmim]I. At relatively higher concentrations (>0.5), the chaotropic action of [Bmim]⁺ dominates which consequently increases the thermal-fluctuations responsible to denature the protein and thus accelerates the speed of CO-association reaction. Analysis of thermal denaturation curves of Ferrocyt c measured at different concentrations of [Bmim]X revealed that the [Bmim]X decreases the thermodynamic stability of protein and typically follows the order: [Bmim]I > [Bmim]Br > [Bmim]Cl > [Bmim]CH₃COO > [Bmim]HSO₄, demonstrating that the effect of [Bmim]X on thermodynamic stability of protein is not in accordance to Hofmeister series effect of anions because instead of increasing the kosmotropic anion carrying [Bmim]X ([Bmim]CH₃COO and [Bmim]HSO₄) also decreases the thermodynamic stability of protein.

Role of Macromolecular Crowding on Stability and Iron Release Kinetics of Serum Transferrin

The macromolecular crowding influences the structural stability and functional properties of transferrin (Tf). The equilibrium as well as kinetic studies of Tf at different concentrations of crowding agents (dextran 40, dextran 70, and ficoll 70) and at a fixed concentration of dextran 40 under different concentrations of NaCl at pH 7.4 and 5.6 (±1) revealed that (i) the crowder environment increases the diferric-Tf (Fe₂Tf) stability against iron loss and overall denaturation of the protein, (ii) both in the absence and presence of crowder, the presence of salt promotes the loss of iron and overall denaturation of Fe₂Tf which is due to ionic screening of electrostatic interactions, (iii) the crowder environment retards iron release from monoferric N-lobe of Tf (Fe_NTf) by increasing enthalpic barrier, (iv) the retardation of iron release by crowding is enthalpically dominated than the entropic one, (v) both in the absence and presence of crowder, the presence of salt accelerates the iron release from Fe_NTf due to ionic screening of electrostatic interactions and anion binding to KISAB sites, and (vi) the crowders environment is unable to diminish (a) the salt-induced destabilization of Fe₂Tf against the loss of iron and overall denaturation and (b) the anion effect and ionic screening of diffusive counterions responsible to promote iron release from Fe_NTf.