Effect of column dimensions and flow rates on size-exclusion refolding of beta-lactamase

State-of-the-art glycosaminoglycan characterization

Glycosaminoglycans (GAGs) are heterogeneous acidic polysaccharides involved in a range of biological functions. They have a significant influence on the regulation of cellular processes and the development of various diseases and infections. To fully understand the functional roles that GAGs play in mammalian systems, including disease processes, it is essential to understand their structural features. Despite having a linear structure and a repetitive disaccharide backbone, their structural analysis is challenging and requires elaborate preparative and analytical techniques. In particular, the extent to which GAGs are sulfated, as well as variation in sulfate position across the entire oligosaccharide or on individual monosaccharides, represents a major obstacle. Here, we summarize the current state-of-the-art methodologies used for GAG sample preparation and analysis, discussing in detail liquid chromatograpy and mass spectrometry-based approaches, including advanced ion activation methods, ion mobility separations and infrared action spectroscopy of mass-selected species.

Refolding of denatured/reduced lysozyme at high concentrations by artificial molecular chaperone-ion exchange chromatography

Development of high efficiency and low cost protein refolding methods is a highlighted research focus in biotechnology. Artificial molecular chaperone (AMC) and protein folding liquid chromatography (PFLC) are two attractive refolding methods developed in recent years. In the present work, AMC and one branch of PFLC, ion exchange chromatography (IEC), are integrated to form a new refolding method, artificial molecular chaperone-ion exchange chromatography (AMC-IEC). This new method is applied to the refolding of a widely used model protein, urea-denatured/dithiothreitol-reduced lysozyme. Many factors influencing the refolding of lysozyme, such as urea concentration, beta-cyclodextrin concentration, molar ratio of detergent to protein, mobile phase flow rate, and type of detergent, were investigated, respectively, to optimize the conditions for lysozyme refolding by AMC-IEC. Compared with normal IEC refolding method, the activity recoveries of lysozyme obtained by AMC-IEC were much higher in the investigated range of initial protein concentrations. Moreover, the activity recoveries obtained by using this newly developed refolding method were still quite high for denatured/reduced lysozyme at high initial concentrations. When the initial protein concentration was 200 mg mL(-1), the activity recovery was over 60%. In addition, the lifetime of the chromatographic column during AMC-IEC was much longer than that during protein refolding by normal IEC. Therefore, AMC-IEC is a high efficient and low cost protein refolding method.

Expression, refolding, and purification of a truncated human Delta-like1, a ligand of Notch receptors

The Notch signaling pathway plays a pivotal role in proliferation, apoptosis, and cell fate specification in both embryonic and postnatal development, and is a potential therapeutic target for human diseases such as cancer. To express in Escherichia coli and purify soluble fragment of human Delta-like1 (hDll1), we cloned two extracellular fragments of hDll1 [hDll1 (127-225) and hDll1 (26-225)]. The hDll1 (127-225) fragment was successfully expressed in E. coli as a GST fusion protein (GST-hDll1). The GST-hDll1 protein, which was expressed as inclusion bodies after induction by IPTG, was refolded and purified simultaneously using affinity chromatography and size exclusion chromatography. The purified GST-hDll1 was of more than 95% purity, and had a molecular weight of 39kDa. Reporter assay showed that GST-hDll1 could activate a reporter gene that is dependent on Notch activation. Therefore, using the E. coli expression system and different chromatography systems, we successfully expressed, refolded, and purified a biologically active GST-hDll1, which might be potentially useful for therapy and studying the Notch pathway.

Protein folding liquid chromatography and its recent developments

The ultimate goal of proteomics is to identify biologically active proteins and to produce them using biotechnology tools such as bacterial hosts. However, proteins produced by Escherichia coli must be refolded to their native state. Protein folding liquid chromatography (PFLC) is a new method developed in recent years, and it is widely used in molecular biology and biotechnology. In this paper, the new method, PFLC is introduced and its recent development is reviewed. In addition the paper includes definitions, advantages, principles, applications for both laboratory and large scales, apparatus, and effecting factors of PFLC. In addition, the role of this method in the future is examined.

Chromatographic media for bioseparation

Bioseparation processes are dominated by chromatographic steps. Even primary recovery is sometimes accomplished by chromatographic separation, using a fluidized bed instead of a fixed bed. In this review, the action principles, features of chromatography media regarding physical and chemical properties will be described. An attempt will be made to establish categories of different media. Characteristics for bioseparation are the large pores and particle sizes. To achieve sufficient capacity for ultralarge molecules, such as plasmids or nanoparticles, such as viruses monoliths are the media of choice. In these media, the mass transport is accomplished by convection, and thus, the low diffusivity can be overcome. Common to all modern chromatography media is the fast operation. There are examples where a residence time of less then 3 min, is sufficient to reach the full potential of the adsorbent.

Folding and refolding of proteins in chromatographic beds

The correct folding of solubilized recombinant proteins is of key importance for their production in industry. On-column refolding of proteins is mainly achieved by three methods: size-exclusion chromatography, ion exchange chromatography and affinity chromatography using immobilized metal chelates. The principles of these methods were first laid down in the 1990s, but many recent improvements have been made to these processes including sophisticated changes to the mobile phase composition and the recycling of aggregates to improve yield. Advances have also been made in the use of immobilized metal affinity chromatography and by mimicking the natural folding process with artificial chaperones.

Protein expression and refolding--a practical guide to getting the most out of inclusion bodies

The release of sequence data, particularly from a number of medically and biotechnologically important genomes, is increasing in an exponential fashion. In light of this, elucidating the structure and function of proteins, particularly in a "high throughput" manner, is an important quest. The production of recombinant proteins however is not always straightforward, with a number of proteins falling prey to low expression problems, a high susceptibility to proteolysis and the often despised production of inclusion bodies. Whilst expression as inclusion bodies can often be advantageous, their solubilization and renaturation is often a time consuming and empirical process. In this review, we aim to outline some of the more common approaches that have been applied to a variety of proteins and address issues associated with their handling.