A high-throughput method for detection of protein self-association and second virial coefficient using size-exclusion chromatography through simultaneous measurement of concentration and scattered light intensity

Improved adsorption reactions, kinetics and stability for model and therapeutic proteins immobilised on affinity resins

Protein adsorption on solid state media is important for the industrial affinity chromatography of biotherapeutics and for preparing materials for self-interaction chromatography where fundamental protein solution thermodynamic properties are measured. The adsorption of three model proteins (lysozyme, catalase and BSA) and two antibodies (a monoclonal and a polyclonal antibody) have been investigated on commercial affinity chromatography media with different surface functionalities (Formyl, Tresyl and Amino). Both the extent of protein immobilised (mg protein/ml media) and the reaction kinetics are reported for a range of reaction conditions, including pH, differing buffers as well as the presence of secondary reactants (glutaraldehyde, sodium cyanoborohydride, EDC and NHS). Compared to the reaction conditions recommended by manufacturers as well as those reported in previous published work, significant increases in the extent of protein immobilisation and reaction kinetics are reported here. The addition of glutaraldehyde or sodium cyanoborohydride was found to be especially effective even when not directly needed for the adsorption to happen. For mAb and pIgG, immobilisation levels of 50 and 31 mg of protein/ml of resin respectively were achieved, which are 100% or more than previously reported. Enhanced levels were achieved for lysozyme of 120 mg/ml with very rapid reaction kinetics (< 1 h) with sodium cyanoborohydride. It can be concluded that specific chromatography resins with Tresyl activated support offered enhanced levels of protein immobilisation due to their ability to react to form amine or thio-ether linkages with proteins. Additionally, glutaraldehyde can result in higher immobilisation levels whilst it can also accelerate immobilisation reaction kinetics.

Hydrogen exchange mass spectrometry reveals protein interfaces and distant dynamic coupling effects during the reversible self-association of an IgG1 monoclonal antibody

There is a need for new analytical approaches to better characterize the nature of the concentration-dependent, reversible self-association (RSA) of monoclonal antibodies (mAbs) directly, and with high resolution, when these proteins are formulated as highly concentrated solutions. In the work reported here, hydrogen exchange mass spectrometry (HX-MS) was used to define the concentration-dependent RSA interface, and to characterize the effects of association on the backbone dynamics of an IgG1 mAb (mAb-C). Dynamic light scattering, chemical cross-linking, and solution viscosity measurements were used to determine conditions that caused the RSA of mAb-C. A novel HX-MS experimental approach was then applied to directly monitor differences in local flexibility of mAb-C due to RSA at different protein concentrations in deuterated buffers. First, a stable formulation containing lyoprotectants that permitted freeze-drying of mAb-C at both 5 and 60 mg/mL was identified. Upon reconstitution with RSA-promoting deuterated solutions, the low vs. high protein concentration samples displayed different levels of solution viscosity (i.e., approx. 1 to 75 mPa.s). The reconstituted mAb-C samples were then analyzed by HX-MS. Two specific sequences covering complementarity-determining regions CDR2H and CDR2L (in the variable heavy and light chains, respectively) showed significant protection against deuterium uptake (i.e., decreased hydrogen exchange). These results define the major protein-protein interfaces associated with the concentration-dependent RSA of mAb-C. Surprisingly, certain peptide segments in the V_H domain, the constant domain (C_H2), and the hinge region (C_H1-C_H2 interface) concomitantly showed significant increases in local flexibility at high vs. low protein concentrations. These results indicate the presence of longer-range, distant dynamic coupling effects within mAb-C occurring upon RSA.

Determination of the second virial coefficient of bovine serum albumin under varying pH and ionic strength by composition-gradient multi-angle static light scattering

Composition-gradient multi-angle static light scattering (CG-MALS) is an emerging technique for the determination of intermolecular interactions via the second virial coefficient B22. With CG-MALS, detailed studies of the second virial coefficient can be carried out more accurately and effectively than with traditional methods. In addition, automated mixing, delivery and measurement enable high speed, continuous, fluctuation-free sample delivery and accurate results. Using CG-MALS we measure the second virial coefficient of bovine serum albumin (BSA) in aqueous solutions at various values of pH and ionic strength of a univalent salt (NaCl). The systematic variation of the second virial coefficient as a function of pH and NaCl strength reveals the net charge change and the isoelectric point of BSA under different solution conditions. The magnitude of the second virial coefficient decreases to 1.13 x 10(-5) ml*mol/g(2) near the isoelectric point of pH 4.6 and 25 mM NaCl. These results illuminate the role of fundamental long-range electrostatic and van der Waals forces in protein-protein interactions, specifically their dependence on pH and ionic strength.

High-throughput biophysical analysis of protein therapeutics to examine interrelationships between aggregate formation and conformational stability

Stabilization and formulation of therapeutic proteins against physical instability, both structural alterations and aggregation, is particularly challenging not only due to each protein's unique physicochemical characteristics but also their susceptibility to the surrounding milieu (pH, ionic strength, excipients, etc.) as well as various environmental stresses (temperature, agitation, lyophilization, etc.). The use of high-throughput techniques can significantly aid in the evaluation of stabilizing solution conditions by permitting a more rapid evaluation of a large matrix of possible combinations. In this mini-review, we discuss both key physical degradation pathways observed for protein-based drugs and the utility of various high-throughput biophysical techniques to aid in protein formulation development to minimize their occurrence. We then focus on four illustrative case studies with therapeutic protein candidates of varying sizes, shapes and physicochemical properties to explore different analytical challenges in monitoring protein physical instability. These include an IgG2 monoclonal antibody, an albumin-fusion protein, a recombinant pentameric plasma glycoprotein, and an antibody fragment (Fab). Future challenges and opportunities to improve and apply high-throughput approaches to protein formulation development are also discussed.

Robust magnetic/polymer hybrid nanoparticles designed for crude oil entrapment and recovery in aqueous environments

Well-defined, magnetic shell cross-linked knedel-like nanoparticles (MSCKs) with hydrodynamic diameters ca. 70 nm were constructed through the co-assembly of amphiphilic block copolymers of PAA20-b-PS280 and oleic acid-stabilized magnetic iron oxide nanoparticles using tetrahydrofuran, N,N-dimethylformamide, and water, ultimately transitioning to a fully aqueous system. These hybrid nanomaterials were designed for application as sequestering agents for hydrocarbons present in crude oil, based upon their combination of amphiphilic organic domains, for aqueous solution dispersibility and capture of hydrophobic guest molecules, with inorganic core particles for magnetic responsivity. The employment of these MSCKs in a contaminated aqueous environment resulted in the successful removal of the hydrophobic contaminants at a ratio of 10 mg of oil per 1 mg of MSCK. Once loaded, the crude oil-sorbed nanoparticles were easily isolated via the introduction of an external magnetic field. The recovery and reusability of these MSCKs were also investigated. These results suggest that deployment of hybrid nanocomposites, such as these, could aid in environmental remediation efforts, including at oil spill sites, in particular, following the bulk recovery phase.

Light-scattering-based analysis of biomolecular interactions

While light scattering has long been applied to the analysis of biomolecular interactions, recent advances have extended the practical use of light scattering techniques to cover a rather broad range of phenomena. In this paper I review essential light scattering theory as applied to specific interactions under thermodynamically ideal conditions and present examples showing how light scattering elucidates the dynamic equilibrium and kinetic behavior of proteins and other biomacromolecules.

Advancements in high throughput biophysical technologies: applications for characterization and screening during early formulation development of monoclonal antibodies

The formulation development of monoclonal antibodies is extremely challenging, due to the diversity and complexity contained within this class of molecules. The physical and chemical properties of a monoclonal antibody dictate the behavior of the protein drug during manufacturing, storage and clinical administration. In the past few years, the use of high throughput technologies has been widely adapted to delineate unique properties of individual immunoglobulin G's (IgG's) important for their development. Numerous screening techniques have been designed to reveal physical and chemical characteristics of a protein relevant to stability under production, formulation and delivery conditions. In addition, protein stability under accelerated stresses has been utilized to predict long-term storage behavior for monoclonal antibodies in the formulation. In this review, we summarize the recent advancements in the field of biophysical technology, with a specific focus on the techniques that can be directly applied to the formulation development of monoclonal antibodies. Several case studies are also presented here to provide examples of combining existing biophysical methods with high throughput screening technology in the formulation development of monoclonal antibody drugs.

Static light scattering from concentrated protein solutions II: experimental test of theory for protein mixtures and weakly self-associating proteins

Using an experimental technique recently developed in this laboratory (Fernández C. and A. P. Minton. 2008. Anal. Biochem. 381:254-257), the Rayleigh light scattering of solutions of bovine serum albumin, hen egg white ovalbumin, hen egg white ovomucoid, and binary mixtures of these three proteins was measured as a function of concentration at concentrations up to 125 g/L. The measured concentration dependence of scattering of both pure proteins and binary mixtures is accounted for nearly quantitatively by an effective hard particle model (Minton A. P. 2007. Biophys. J. 93:1321-1328) in which each protein species is represented by an equivalent hard sphere, the size of which is determined by the nature of repulsive interactions between like molecules under a given set of experimental conditions. The light scattering of solutions of chymotrypsin A was measured as a function of concentration at concentrations up to 70 g/L at pH 4.1, 5.4, and 7.2. At each pH, the measured concentration dependence is accounted for quantitatively by an effective hard particle model, according to which monomeric protein may self-associate to form an equilibrium dimer and, depending upon pH, an equilibrium pentamer or hexamer.

Chromatography in industry

This review focuses on the chromatography research that has been carried out within industry or in close cooperation with industry and that has been reported in the scientific literature between 2006 and mid-2008. Companies in the health care sector, such as pharmaceutical and biotechnology companies, are the largest contributors. Industrial research seems to take place in an open environment in cooperation with academia, peer companies, and institutions. Industry appears ready to embrace new technologies as they emerge, but they focus strongly on making chromatography work robustly, reliably, rapidly, and automatically. "Hyphenated" systems that incorporate on-line sample-preparation techniques and mass-spectrometric detection are the rule rather than the exception. Various multidimensional separation methods are finding numerous applications. Strategies aimed at speeding up the development of new chromatographic methods remain the focus of attention. Also, there is a clear trend toward exploring chromatographic methods for parallel processing along with other strategies for high-throughput analysis.