Affinity tagging & purification of the fucose binding LecB protein

The fucose binding LecB protein is one of two identified lectins produced by the opportunistic pathogen Pseudomonas aeruginosa (PA01) and is implicated in contributing to its virulence. A large number of homologous proteins have been identified in other bacterial species that exhibit extremely high sequence identity and similarity to LecB. However, key amino acid residues known to participate in fucose binding in LecB are altered in many of these proteins. Some of these proteins have been shown to exhibit altered sugar specificities while others are as yet uncharacterised. The existence of such homologues suggests the sugar binding specificity of the LecB protein could potentially be further diversified through mutagenesis to generate novel biomolecular recognition molecules for glycoprotein characterisation and purification applications

Some Early Bronze Age stone moulds from Scotland

This paper presents details of a number of previously unpublished or relatively inaccessibly published Early Bronze Age stone moulds from Scotland. Viewed in the wider context of Early Bronze Age metalworking in Britain, they are important additions to the inventory of finds, for as well as augmenting the concentration of discoveries long known from northeast Scotland, they expand the distribution southwards into eastern and central Scotland and into the Scottish Borders and therefore go some way to filling the gap that previously existed between Aberdeenshire and Northumberland

Hydrophobic interaction chromatography

Most proteins and large polypeptides have hydrophobic regions at their surface. These hydrophobic ‘patches’ are due to the presence of the side chains of hydrophobic or non-polar amino acids such as phenylalanine, tryptophan, alanine and methionine. These surface hydrophobic regions are interspersed between more hydrophilic or polar regions and the number, size and distribution of them is a specific characteristic of each protein. Hydrophobic Interaction Chromatography (HIC) is a commonly used technique that exploits these hydrophobic features of proteins as a basis for their separation even in complex biological mixtures (1) (2). In general the conditions under which hydrophobic interaction chromatography is used are relatively mild and ‘protein friendly’ resulting in good biological recoveries. Hydrophobic binding is relatively strong and is maintained even in the presence of chaotrophic agents, organic solvents and detergents. For these reasons this technique has a widespread use for the purification of proteins and large polypeptides

Cloning of hemagglutinin (HA) protein of influenza A virus - Potential for sialic acid linkage discrimination

The initial step in infection of a cell by influenza A virus is the attachment of a virus particle to the target cell. This is accomplished by interaction of a glycoprotein, hemagglutinin (HA), found on the surface of the viral lipid membrane with cell-surface oligosaccharides containing sialic acids. All influenza virus attachment requires terminal sialic acid residues and two major linkages between sialic acid (Neu5Ac) and the penultimate galactose (Gal) residues of carbohydrate side chains are found in nature, Neu5Ac(α2,3)-Gal and Neu5Ac(α2,6)-Gal. The HA’s of different subtypes of influenza A virus exhibit different recognition specificities for these linkages and these linkage specificities have been correlated with host range specificity. The ability of the HA protein to differentiate sialic acid linkages makes it an interesting candidate for use in the characterization of glycoprotein's potentially facilitating the discrimination of alternate glycoforms of biopharmaceutical therapeutics and their subsequent purification

The use of chitin binding proteins for glycoprotein analysis

The focus of the pharmaceutical industry has dramatically shifted in the past number of years. Traditional drugs were synthesised using chemical reactions have been replaced by recombinant glycoprotein molecules. These potential recombinant glycoprotein therapeutics display oligosaccharide structures on their surfaces that are recognised by their target host. The specific glycan moieties on the surface of the molecules vary dramatically and have a large impact on the efficacy of the drug. The development of bioanalytical tools to identify and separate the species of glyco-forms present in a preparation of the glycoprotein therapeutic will significantly help to advance the quality and effectiveness of recombinant glycoprotein molecules. Traditionally lectins, isolated from plants, had been used to profile sugar species displayed on glycoproteins. I have explored the use of prokaryotic chitin binding proteins (CBPs) to investigate structures on glycoproteins

Ion exchange chromatography – basic principles and application

Ion-Exchange Chromatography (IEC) allows for the separation of ionizable molecules on the basis of differences in charge properties. Its large sample-handling capacity, broad applicability (particularly to proteins and enzymes), moderate cost, powerful resolving ability, and ease of scale-up and automation have led to it becoming one of the most versatile and widely used of all liquid chromatography (LC) techniques. In this chapter, we review the basic principles of IEC, as well as the broader criteria for selecting IEC conditions. By way of further illustration, we outline protocols necessary to partially purify a serine peptidase from bovine whole brain cytosolic fraction, covering crude tissue extract preparation through to partial purification of the target enzyme using anion-exchange chromatography. Protocols for assaying total protein and enzyme activity in both pre- and post-IEC fractions are also described. The target serine peptidase, prolyl oligopeptidase (POP, EC3.4.21.26), is an 80 kDa enzyme with endopeptidase activity towards peptide substrates of ≤30 amino acids. POP is a ubiquitous post-proline cleaving enzyme with particularly high expression levels in the mammalian brain, where it participates in the metabolism of neuroactive peptides and peptide-like hormones (e.g. thyroliberin, gonadotropin-releasing hormone)