Separation of enantiomers on a chiral stationary phase based on ovoglycoprotein. V. Influence of immobilization method on chiral resolution

Progress in Chiral Stationary Phases Based on Proteins and Glycoproteins

A lot of chiral stationary phases (CSPs) have been introduced for the purpose of analytical and preparative separations of enantiomers. CSPs based on proteins and glycoproteins have unique properties among those CSPs. This review article deals with the preparation of CSPs based on proteins and glycoproteins, their chiral recognition properties and mechanisms, focusing on the CSPs investigated in our group. The dealt proteins and glycoproteins are including bovine serum albumin, human serum albumin, lysozyme, pepsin, human α₁-acid glycoprotein (AGP), chicken ovomucoid and chicken ovoglycoprotein (named chicken AGP).

Separation of enantiomers on chiral stationary phase based on cellulase: Effect of preparation method and silica particle diameters on chiral recognition ability

Cellulase (Cel) was immobilized onto aminopropyl-silica gels via its amino and carboxy groups, respectively, using N,N'-disuccinimidyl carbonate, and 1-ethyl-3-(3'-dimethylaminopropyl)carbodimide and N-hydroxysulfosuccinimide. They were termed N-Cel and C-Cel, respectively. Despite their smaller retention factors on a C-Cel column, the enantioseparation factors and resolution of β-blockers, propranolol, alprenolol, oxprenolol and pindolol, were similar with N- and C-Cel columns. In addition, C-Cel was prepared using aminopropyl-silica gels, whose nominal particle diameters were 5 and 3, and 2.1μm, respectively. A C-Cel column prepared with 2.1-μm aminopropyl-silica gels gave the highest enantioselectivity and column efficiency among three C-Cel columns. Furthermore, the influence of N,N-dimethyl-n-octylamine (DMOA) or cellobiose concentrations on the retentivity and enantioselectivity for β-blockers on a C-Cel column was investigated. The results indicate that single-site competition of β-blockers with DMOA or cellobiose on the catalytic binding site of Cel and the further bindings at the secondary site in a non-competitive fashion could occur. Furthermore, the enantioselective bindings of β-blockers could occur at the catalytic biding cite of Cel and at the secondary binding site.

Enhanced protein immobilization efficiency on a TiO2 surface modified with a hydroxyl functional group

An antibody immobilization was investigated using a self-assembled monolayer (SAM) over the highly refractive coatings with a SiO2, TiO2, or Si3N4 substrate. The immobilization was characterized by analyzing the hydrophilic properties of hydroxyl (OH) groups on surface coatings with contact angle (CA) measurements to enhance protein immobilization. The hydroxyl (OH) group was formed in greater amounts as the oxygen plasma exposure time was increased, which resulted in a large enhancement in antibody immobilization. It indicated that hydroxyl (OH) group formation is critical for developing a label-free optical transducer with a high sensitivity.

Role of biological matrices during the analysis of chiral drugs by liquid chromatography

The review article covers advances of chiral drugs analysis by high-performance liquid chromatography (HPLC) methods achieved during last 10 years. Emphasis is given to various aspects of influence of biological matrix in pharmacodynamics, pharmacokinetics, HPLC analysis. Discussed is composition of main biological matrices from the point of view of potential interferences to above-mentioned fields of study. Beside typical analytical approaches to chiral recognition in HPLC, sample pretreatment and/or clean-up by conventional extraction procedures, column switching (CSW) techniques using restricted access materials (RAMs), microdialysis (MCD) is discussed. Measurement of unbound drug concentration and discussion of column maintenance and remedy is an additional source of information and field where knowledge on complex properties and interactions of biological matrix is usefully applicable.

Stereoselective chromatography of cardiovascular drugs: an update

This review reports the latest achievements in chromatographic enantioseparations of various classes of cardiovascular drugs and selected applications of these methods in pharmaceutical and clinical analysis. The use of these drugs as test compounds for new chiral stationary phases and different parameters of chromatographic processes is also presented.

Development of a validated capillary electrophoresis method for enantiomeric purity testing of dexchlorpheniramine maleate

A capillary zone electrophoresis method has been developed for the detection of 0.1% of (R)-levochlorpheniramine maleate in samples of (S)-dexchlorpheniramine maleate. Using 1.5 mM carboxymethyl-beta-cyclodextrin in an acidic background electrolyte, resolution values of more than 10 were obtained. Under these conditions the R-enantiomer is migrating in front of the bulk S-enantiomer. The assay was validated for linearity (2-10 microg/ml; R2 = 0.9992), selectivity [(RS)-pheniramine maleate and (RS)-brompheniramine maleate], limit of detection (0.25 microg/ml), limit of quantification (0.75 microg/ml), analytical precision (intra- and inter-day variability), repeatability of the method (RSD = 5.0%) and accuracy. In samples of dexchlorpheniramine maleate from two different manufacturers, concentrations of, respectively, 0.15% and 1.95% (m/m) of levochlorpheniramine maleate were detected. The method was compared to the HPLC method described in the European Pharmacopoeia III monograph.

Chiral separation by chromatographic and electromigration techniques. A review

This review gives a survey of different chiral separation principles and their use in high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography (TLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) highlighting new developments and innovative techniques. The mechanisms of the different separation principles are briefly discussed and some selected applications are shown.

Immobilized penicillin G acylase as reactor and chiral selector in liquid chromatography

In this paper, the use of penicillin G acylase (PGA) as a biocatalyst and as a chiral selector is described. Penicillin G-acylase is an interesting enzyme used in the manufacture of semisynthetic antibiotics and, in particular, in the production of 6-APA by hydrolysis of penicillin G. Five PGA-based HPLC columns have been prepared by using two different silica supports by employing two immobilization methods, namely "in situ" and "in batch". The effects of the immobilization techniques and of different silica pore size on the catalytic properties of the enzyme as well as the applicability of the PGA-bonded stationary phases as chiral selectors for a number of chiral drugs have been investigated. The HPLC columns based on immobilized PGA combine the hydrolytic activity and the chiral recognition properties of PGA, therefore they have been used for the development of a combined reaction-separation system for chiral and achiral substrates.

Properties of a stationary phase based on immobilised chicken liver basic fatty acid-binding protein

The fatty acid-binding proteins (FABPs) are a class of low-molecular-mass proteins that bind fatty acids and are thought to be involved in their intracellular transport. FABPs have been isolated and studied from several tissues, but their precise function and mechanism of action are still not clear. Chicken liver (basic) fatty acid-binding protein (bFABP) was immobilised on aminopropyl silica and the developed stationary phase was used to examine the enantioselective properties of this protein and to study the binding of drugs to bFABP. The retention and enantioselectivity of the new column for a large number of chiral drugs was investigated. The enantiomers of basic and neutral compounds were poorly retained and not resolved by the bFABP column. On the contrary the resolution of the enantiomers of some acidic compounds was obtained. Therefore the influence of the mobile phase pH and organic modifier on the chromatographic performance of acidic compounds was studied. In order to clarify the retention mechanism, competitive displacement studies were also carried out by adding short-chain fatty acids to the mobile phase as displacing agents and preliminary quantitative structure-retention relationship correlations were developed to describe the nature of the interactions between the chemical structures of the analytes and the observed chromatographic results.

Protein-based chiral stationary phases for high-performance liquid chromatography enantioseparations

The enantioseparations of various compounds using proteins as the chiral selectors in high-performance liquid chromatography (HPLC) are considered in this review. The proteins used include albumins such as bovine serum albumin and human serum albumin, glycoproteins such as alpha1-acid glycoprotein, ovomucoid, ovoglycoprotein, avidin and riboflavin binding protein, enzymes such as trypsin, alpha-chymotrypsin, cellobiohydrolase I, lysozyme, pepsin and amyloglucosidase, and other proteins such as ovotransferrin and beta-lactoglobulin. This review deals with the properties of HPLC chiral stationary phases based on proteins, and the enantioselective properties and chiral recognition mechanisms of these stationary phases.

Separation of enantiomers on a chiral stationary phase based on ovoglycoprotein. VII. Comparison of chiral recognition ability of ovoglycoprotein from chicken and Japanese quail egg whites

Ovoglycoproteins from chicken and Japanese quail egg whites (OGCHI and OGJPQ, respectively) were isolated, and characterized by isoelectric focusing, high-performance capillary electrophoresis, reversed-phase HPLC and matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) MS. The isoelectric point (pI) of natural OGCHI was 4.37-4.51 by isoelectric focusing, while natural OGJPQ showed two discrete bands at pI 4.68 and 4.77. The average molecular masses of natural OGCHI and OGJPQ were estimated to be about 30000 and 27400 by MALDI-TOF-MS. Both natural OGCHI and OGJPQ were either fully or partially glycosylated with a ratio of ca. 3:1. Next, natural OGCHI and OGJPQ were bound to aminopropyl-silica gels activated with N,N'-disuccinimidylcarbonate to compare retentive and enantioselective properties of the two columns. The OGCHI column is suitable for chiral resolution of basic compounds, while the OGJPQ column is suitable for that of acidic compounds. With regard to chiral resolution of neutral compounds, it is dependent on a compound resolved which column could be suitable. Differences in the retentivity and enantioselectivity between OGCHI and OGJPQ columns are due to differences in the enantioselective binding properties. The results obtained reveal that chiral recognition of various solutes could be efficiently attained by using both columns complementarily.