Molecular dynamics simulation of the effect of ligand homogeneity on protein behavior in hydrophobic charge induction chromatography
Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.Journal of molecular graphics & modelling (Impact Factor: 1.72). 03/2010; 28(8):863-9. DOI: 10.1016/j.jmgm.2010.03.006
Hydrophobic charge induction chromatography (HCIC) is an adsorption chromatography combining hydrophobic interaction in adsorption with electrostatic repulsion in elution. Ligand density has significant effects on protein adsorption behavior, but little is understood about the effect of ligand homogeneity on surface morphology of ligands, protein conformational transition and dynamics within adsorbent pore due to the lack of microscopic experimental techniques. In the present study, a coarse-grained adsorbent pore model established in an earlier work is used to represent the actual porous adsorbent composed of matrix and immobilized HCIC ligands. Two adsorbent pores with different ligand distributions are constructed by adjusting the coupling sites, denoted as L1 and L2. In L1 the ligands are bonded uniformly while in L2 the ligands are arranged in lines in the axial direction and thus exhibit a heterogeneous distribution. Protein adsorption, desorption, and conformational transition in both L1 and L2 are shown by molecular dynamics simulations of a 46-bead beta-barrel coarse-grained model protein within the adsorbent pore models. The simulations indicate that ligand homogeneity has significant effect on both the irreversibility and the dynamics of adsorption while no obvious effect on protein conformation distribution. In comparison with L1, L2 leads to irreversible and slow adsorption, indicating the strict requirement of a suitable protein orientation to reach stable adsorption. The simulations have provided new insight into the microscopic behavior of HCIC, which would be beneficial to the rational design of adsorbents and parameter optimization for high-performance HCIC.
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ABSTRACT: Dramatic improvements in cell culture titers, product quality constraints, new regulatory directives, and the emergence of biosimilars have necessitated the development of more efficient downstream bioprocesses for biopharmaceuticals. This has resulted in significant improvements in traditional separation processes as well as the emergence of entirely new approaches. In this review, we highlight some of these recent advances. This includes chromatographic phases with elevated capacities and unique selectivities, new classes of monoliths and membrane adsorbers for the recovery of large bioproducts, high resolution membrane systems for polishing operations, continuous downstream processes for multicomponent separations, affinity tags with self-cleaving inteins, responsive biopolymers for single step separations, the implementation of high throughput process development, and designing proteins for biomanufacturability.Current Opinion in Chemical Engineering 10/2011; 1(1):27–37. DOI:10.1016/j.coche.2011.08.008
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ABSTRACT: Hydrophobic charge-induction chromatography (HCIC) with 4-mercaptoethyl-pyridine (MEP) as the ligand is a novel technology for antibody purification. In the present work, the molecular simulation methods were used to investigate the interactions between MEP ligand and Fc fragment of IgG (Fc-A). Six ligands with different structures of spacer arm were studied with molecular docking and dynamics simulation at neutral and acidic pH. The binding modes and the interaction energies were analyzed. The results indicated that all ligands tested could bind into the selected pocket on the C(H2) domain of Fc-A at neutral pH. The pyridine ring on the top of MEP ligands acts as a major role to provide the hydrophobic association and hydrogen bond for the ligand-IgG binding; meanwhile, the sulfone group on the spacer arm might form the additional hydrogen bond and enhance the binding of ligand onto the surface of IgG. The replacements of thioether sulfur atom on the spacer arm with either nitrogen or oxygen atom seem to have little influence on the binding. The influences of pH on the ligand-IgG interactions were also studied with the molecular dynamics simulation. It was found that MEP ligands would departed from the surface of Fc-A at low pH due to the electrostatic repulsion. The ligands with a sulfone group on the spacer arm would weaken the electrostatic repulsion and need more acidic conditions for the departing of ligand. The molecular simulation results were in agreement with some experimental observations, which would be useful to elucidate the molecular mechanism of HCIC and design a novel ligand to improve the efficiency of antibody separation.The Journal of Physical Chemistry B 01/2012; 116(4):1393-400. DOI:10.1021/jp206817b · 3.30 Impact Factor
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ABSTRACT: Aggregate level is a key factor when assessing quality attributes of antibody product, since the aggregation might impact the biological activity of biopharmaceutical. Effective separation methods are usually essential in manufacturing processes. In this study, three mixed-mode resins, i.e. Capto adhere and two home-made resins with benzylamine and butylamine as the functional ligands (named BA and AB), were used to investigate the separation performances of antibody aggregate removal processes. In addition, two traditional resins (Q Sepharose FF and Phenyl Sepharose 6 FF) were also investigated to explore the role of molecular interaction in the aggregate removal. The results indicated that the removal efficiency was highly dependent on the mass loading. With the sample load of 50mg/ml resin both Capto adhere and BA resins can significantly reduce the aggregate level from 20.5% to 2.6% and 2.4%, respectively, while a relatively low degree of aggregate reduction was found with the traditional resins. The research indicates that both hydrophobic interaction and electrostatic interaction are critical for the aggregate removal and the cooperativity of different molecular interactions is important for the effective aggregates removal with mixed-mode resins.Journal of Chromatography A 04/2013; 1294. DOI:10.1016/j.chroma.2013.04.018 · 4.17 Impact Factor
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