An high-performance liquid chromatography matrix based on agarose cross-linked with divinyl sulphone

Manipulation of pore structure during manufacture of agarose microspheres for bioseparation

Agarose microspheres with a controllable pore structure were manufactured by varying agarose types and crosslinking degrees. Various agarose could tailor the gel formation of microspheres matrix and thus affect the final pore structures. Small pores in microspheres could be fabricated by agarose with a higher molecular weight, which was demonstrated by the packed column with lower distribution coefficient (Kav ) values measured by gel filtration chromatography. Further, higher Kav values also demonstrated that more and larger pores were formed with increasing the crosslinking degree of agarose microspheres. Either using agarose with a high molecular weight or increasing the crosslinking degree would finally lead to the enhancement of the flow rate during flow performance of packed column as necessary for improving separation efficiency. This provides a foundation for high-resolution chromatography with a controllable separation range as beneficial for downstream process.

Determination of nociceptin-orphanin FQ metabolites by capillary LC-MS

Nociceptin-orphanin FQ (OFQ/N) is a newly discovered peptide involved in pain transmission. The method is described to identify metabolic pathway of this neuropeptide in the spinal cord of rats using capillary size-exclusion liquid chromatography coupled to electrospray ionization mass spectrometry. The applied technique is rapid and selective, and allows for simultaneous measurement and quantitation of several fragments in the incubation mixture.

Size-exclusion chromatography performed in capillaries. Studies by liquid chromatography-mass spectrometry

Miniaturization of the chromatographic column led to increased sensitivity and shortened time of analysis. In our work we applied 300 microm I.D. capillaries packed with a novel stationary phase Superdex Peptide for the size-exclusion chromatography, capable of separating molecules within the mass range of 0.1-7 kDa. Here we proved that such capillary columns can operate effectively at high sensitivity. Several peptide mixtures were efficiently chromatographed and analyzed on line with electrospray ionization mass spectrometry as a detection technique. A CNBr peptide map, derived from human globin alpha subunit, was effectively separated using this method. These fragments are difficult to elute from the reversed-phase column at low pH, therefore, such approach can be considered as a complementary to other separation techniques, in particular for analyzing hydrophobic components and complex mixtures.

Chromatography in the downstream processing of biotechnological products

Chromatography techniques are essential for the isolation and purification of most of the high value products of modern biotechnology. The economically sensible and technically satisfactory downstream processing of a therapeutic protein, usually involves a number of chromatographic steps. Its development and optimization require considerable knowledge of the various physico-chemical and engineering aspects of biochemical chromatography. This review addresses the various modes of chromatography and the design of chromatographic separation processes from a biotechnologist's point of view. Strategies for optimizing the structure of the downstream process are outlined and scaling up consideration are discussed. The importance of the different chromatographic methods in research and development is estimated in an analysis of protein purification schemes recently published in the literature. Finally, examples of the application of chromatographic procedures for process scale product purification in the biotechnological industry are given.

Effect of bed compression on high-performance liquid chromatography columns with gigaporous polymeric packings

The behavior of chromatographic columns packed with gigaporous, highly cross-linked styrenic particles was investigated for use in protein separation by reversed-phase chromatography at high flow velocities. Stainless-steel columns which were 3.5 or 7.5 cm long and had an inner diameter of 0.46 mm were slurry packed with 8 or 20 mm diameter spherical particles of 4000 A mean pore size by using methanol as the packing fluid. It was found that the conditions employed during the packing process have a dramatic effect on the properties of such columns and that this can be attributed in part to the deformability of the particles. An increase in the packing pressure to approximately 6000 p.s.i. (41 MPa) resulted in a higher mass-transfer efficiency for the column with a concomitant decrease in permeability. This is ascribed to a decrease in the interstitial porosity with increasing packing pressure since the experimentally measured plate heights for these columns were found to agree quantitatively with theoretical predictions that relate changes in the interstitial porosity to intraparticle mass transfer. However, the theoretically derived relationship between porosity, permeability, and efficiency does not hold for columns packed at pressures higher than 6000 p.s.i., in which case the total column porosity was found to be high while the permeability and column efficiency were low. This behavior is explained by the formation of a low-porosity layer of highly compressed particles at the downstream end of the column during high pressure packing so that the assumption of axially uniform column properties used in the theoretical approach leads to very large errors.

New porous organic microspheres for high-performance liquid chromatography

A process for producing spherical porous organic microspheres, based on urea-formaldehyde (UF) polymer, has been developed. These microspheres exhibit exceptional mechanical strength and resiliency and have minimal tendency toward shrinking or swelling in aqueous, organic, or hydroorganic media. The geometric parameters of the microspheres are conveniently adjusted by process variables, which allow precise control of pore and particle dimensions. The surface of the UF microsphere contains organic functional groups suitable for chemical modification so that ligands of choice may be covalently attached for operation in the anion-exchange or hydrophobic interaction modes.

Quantitative determination of propranolol in plasma and pharmaceutical preparations by agar-based cation-exchange chromatography utilizing the native anion groups in the agaropectin moiety

A new cost-effective method for determining the amount of total propranolol (free and protein-bound) in plasma samples and the amount of the drug in tablets and injection solutions has been developed. The method is based on cation-exchange chromatography at pH 8.5 on an inexpensive column of agar, the native sulfate (and carboxylic) groups of which interact with the positively charged propranolol (this interaction is reinforced by the 'aromatic adsorption' characteristic of the agar matrix). The method can be used for quantitative analyses at both low (1 x 10(-2) mg/L) and high (5 x 10(3) mg/L) concentrations of the drug. For analyses of plasma and tablets--but not for injection solutions--extraction of the propranolol is required. The extraction time was 6 min. On a 6(ID) mm x 9 mm agar column the run time was less than 10 min.

Purification of membrane proteins in SDS and subsequent renaturation

A prerequisite for the purification of any protein to homogeneity is that the protein is not non-specifically associated with other proteins especially during the final stage(s) of the fractionation procedure. This requirement is not so often fulfilled when nonionic detergents (for instance Triton X-100) are used for solubilization of membrane proteins. The reason is that these detergents are not efficient enough to prevent the protein of interest from forming aggregates with other proteins upon contact with chromatographic or electrophoretic supporting media, which, due to their polymeric nature, have a tendency to induce aggregation of other polymers, for instance, hydrophobic proteins. The aggregation can be avoided if sodium dodecyl sulfate (SDS) is employed as detergent. We therefore suggest that membrane proteins should be purified by conventional methods in the presence of SDS and that the purified proteins, which are in a denatured state, are allowed to renature. There is good change to renature internal membrane proteins since they should not be so susceptible to denaturation by detergents as are water-soluble proteins because the natural milieu of the former proteins is lipids which in fact are detergents. In this paper we present a renaturation method based on the removal of SDS by addition of a large excess of G 3707, a nonionic detergent. By this technique we have renatured a 5'-nucleotidase from Acholeplasma laidlawii and a neuraminidase from influenza virus. The enzyme activities were higher (up to 6-fold) after the removal of SDS than prior to the addition of SDS.

Glycidol-modified gels for molecular-sieve chromatography. Surface hydrophilization and pore size reduction

Divinyl sulfone-crosslinked agarose gels were made hydrophilic by coupling glycidol to the agarose chains. The concentration of glycidol in the reaction mixture determines the pore size of the gels (the glycidol molecules probably form polymers, the degree of polymerization increasing with the glycidol concentration). Gels prepared with moderate glycidol concentrations are still porous enough to be used for separation of proteins and peptides. Gels with a high degree of glycidol polymerization are suited for desalting of low-molecular-weight compounds, for instance peptides.