Making Sharper Peaks for Reverse-Phase Liquid Chromatography of Proteins

Protein separations have gained increasing interest over the past two decades owing to the dramatic growth of proteins as therapeutics and the completion of the Human Genome Project. About every decade, the field of protein high-performance liquid chromatography (HPLC) seems to mature, having reached what appears to be a theoretical limit. But then scientists well versed in the basic principles of HPLC invented a way around the limit, generating another decade of exciting progress. There is still the need for higher resolution and better compatibility with mass spectrometry because it is an essential tool for identification of proteins and their modifications. To make advances, the fundamental principles need to be understood. This review covers recent advances and current needs in the context of the principles that underlie the many contributions to peak broadening.

A mechanistic examination of salting out in protein–polymer membrane interactions

Developing a mechanistic understanding of protein dynamics and conformational changes at polymer interfaces is critical for a range of processes including industrial protein separations. Salting out is one example of a procedure that is ubiquitous in protein separations yet is optimized empirically because there is no mechanistic description of the underlying interactions that would allow predictive modeling. Here, we investigate peak narrowing in a model transferrin–nylon system under salting out conditions using a combination of single-molecule tracking and ensemble separations. Distinct surface transport modes and protein conformational changes at the negatively charged nylon interface are quantified as a function of salt concentration. Single-molecule kinetics relate macroscale improvements in chromatographic peak broadening with microscale distributions of surface interaction mechanisms such as continuous-time random walks and simple adsorption–desorption. Monte Carlo simulations underpinned by the stochastic theory of chromatography are performed using kinetic data extracted from single-molecule observations. Simulations agree with experiment, revealing a decrease in peak broadening as the salt concentration increases. The results suggest that chemical modifications to membranes that decrease the probability of surface random walks could reduce peak broadening in full-scale protein separations. More broadly, this work represents a proof of concept for combining single-molecule experiments and a mechanistic theory to improve costly and time-consuming empirical methods of optimization.

Iron Oxide Nanoparticles: An Efficient Nano-catalyst

Magnetic iron oxide nanoparticles have attracted attention because of their idiosyncratic physicochemical characteristics and vast range of applications such as protein separations, catalysis, magnetic resonance imaging (MRI), magnetic sensors, drug delivery, and magnetic refrigeration. The activity of the catalyst depends on the chemical composition, particle size, morphology and also on the atomic arrangements at the surface. The catalytic properties of iron oxide nanoparticles can be easily altered by controlling the shape, size, morphology and surface modification of nanomaterials. This review is focused on the use of iron oxide as a catalyst in various organic reactions viz. oxidation, hydrogenation, C-C coupling, dihydroxylation reactions and its reusability/recoverability.