Size-exclusion liquid chromatography and capillary electrophoresis of pollen allergens

Profiling recombinant major birch pollen allergen Bet v 1a and carbamylated variants with CZE and CIEF

A preparation of recombinant birch pollen allergen of Betula verrucosa isoform 1a (Bet v 1a) containing chemically modified (carbamylated) variants has been analyzed by CZE and CIEF. In CZE, employing a 100 mmol/L MES buffer at pH 6.50, with 0.4 mmol/L tetraethylenepentamine (TEPA) added, allowed for the resolution of 17 protein fractions. The CIEF profiling of the allergen preparation required a combination of a wide-pH-range carrier ampholyte (CA) of pH 3-10 with two narrow-range CAs of pH 5-6 and 5-7. For CIEF, 91 mmol/L of glycine at pH 2.12 and 20 mmol/L of CHES at pH 10.00 were applied as anolyte and catholyte, respectively. The generated pH gradient was nonlinear with a flat slope for pH 4-6, thus providing an improved resolution. In CIEF, up to 18 protein fractions were distinguished as well. The pI of the target allergen Bet v 1a was 4.9 as determined by means of two pI marker compounds flanking the allergen. Relative purity of the target allergen within the preparation containing carbamylated variants was in accordance for both separation systems and varied between 40.7 and 42.8%.

Profiling preparations of recombinant birch pollen allergen Bet v 1a with capillary zone electrophoresis in pentamine modified fused-silica capillaries

Three preparation batches of the recombinant birch pollen allergen Bet v 1a have been analyzed by capillary zone electrophoresis (CZE) using a separation electrolyte consisting of 100 mmol L(-1) phosphate at pH 6.50 with 2.0 mmol L(-1) tetraethylenepentamine (TEPA) added. TEPA improved the resolution by wall shielding and selective attachment to allergens, but reduced migration repeatability at concentrations >2.0 mmol L(-1). Heterogeneity of preparations determined by CZE and electrospray ionization-quadrupole-time-of flight-MS were in accordance and revealed chemically modified (carbamylated) allergens in one of the preparations. The method was validated according to the ICH-guidelines. Repeatability of effective electrophoretic mobility (mu(eff)) was <0.55% R.S.D. (n = 5). Migration time corrected peak areas were used for quantification. Limit of quantification (LOQ) was 25 microg mL(-1) for the major isoform Bet v 1a, based on a signal-to-noise ratio of 10, and detector response was linear between LOQ and 0.90 mg mL(-1). Purity of the different rBet v 1a preparations was determined to be between 40 and 92% depending on the manufacturing protocol.

Analysis of liquid extracts from tree and grass pollens by capillary electromigration methods

Capillary electromigration methods, zone electrophoresis (CZE), micellar electrokinetic chromatography (CMEKC) and isotachophoresis (CITP), have been used for analysis of water and water-buffer extracts from tree-common birch (Betula verrucosa) and grass-orchardgrass (Dactylis glomerata) pollen samples. Water extracts were analyzed by CZE using acetic acid as background electrolyte (BGE), by CMEKC in tris-phosphate BGE with anionic detergent sodium dodecyl sulfate (SDS) micellar pseudophase (TP-SDS) and by CITP in cationic mode with leading/terminating cations K+/BALA+ (beta-alanine (BALA)) and in anionic mode with leading/terminating anions Cl-/MES- (2-(N-morpholino)ethanesulphonic acid (MES)). Moreover, acetic acid extracts were analyzed by CZE using acetic acid as BGE, and alkaline water-SDS-buffer extracts were analyzed by CMEKC using TP-SDS as BGE. Extracted amounts of pollen allergens and other UV-absorbing compounds and the number of resolved components were evaluated from CZE, CMEKC and CITP analyses of the liquid extracts. Larger amounts of UV-absorbing material were found in the water-buffer pollen extracts than in the water extracts. More UV-absorbing material was found in all extracts from D. glomerata pollen than in relevant extracts from B. verrucosa pollen. It was found by CITP that the extracted amounts of anionic components and their number were much higher than those of cationic components. Concentrations of some inorganic ions (e.g. Cl-, K+, Na+, Ca2+) in pollen samples were also determined by CITP.

Some potentialities and drawbacks of contemporary size-exclusion chromatography

The present state of the chromatographic techniques based on differentiation of solutes according to their molecular sizes is briefly surveyed. Attention is centred on high-performance techniques applied to purification and characterization of natural macromolecules, and on discussion of the chromatographic approaches to the determination of the molecular masses and molecular mass distributions of both natural and synthetic polymers. The basic requirements on the selection of the separation system and the experimental conditions are summarized, demonstrated on a few examples and critically evaluated.

Modification of capillary electrophoresis capillaries by poly(hydroxyethyl methacrylate), poly(diethylene glycol monomethacrylate) and poly(triethylene glycol monomethacrylate)

Modification of capillary electrophoresis (CE) capillaries by poly(hydroxyethyl methacrylate) (poly(HEMA), poly(diethylene glycol monomethacrylate) (poly(DEGMA) and poly(triethylene glycol monomethacrylate) (poly(TEGMA), was studied. Methods based on physical adsorption of the modifier and on its chemical binding were compared on the basis of the electroosmotic flow (EOF) reproducibility, the EOF dependence on the pH, the symmetry of the peak of positively charged tyramine, the stability of the coating and the separation of standard and milk proteins in the modified capillaries. Reproducible coatings were obtained by chemical binding of the polymers to the capillary walls and by coating with a solution of a polymer, as also demonstrated by the atomic force microscopy.

High-performance separations in isolation and characterization of allergens

The present state of the use of separation techniques in the identification and characterization of allergens and in the monitoring of the quality of allergenic preparations is critically surveyed. After a brief summary of the range of problems encountered in obtaining and in the application of allergenic preparations and of the principal physico-chemical properties of allergens, chromatographic and electromigration methods of separation of components of these systems and their combinations with immunochemical procedures are discussed, with selected examples of application to real materials. Emphasis is placed on evaluation of the most important analytical parameters, such as reliability of the results, separation efficiency and resolution, and on the most recent results in the field.