The role of branching glycan of human alpha1-acid glycoprotein in enantioselective binding to basic drugs as studied by capillary electrophoresis

Chiral interactions of the drug propranolol and α1-acid-glycoprotein at a micro liquid-liquid interface

The investigation of chiral interactions of drugs with plasma proteins is of fundamental importance for drug efficacy and toxicity studies. In this paper, we demonstrate a simple liquid-liquid interface procedure for investigating chiral interactions. Chiral discrimination of the enantiomers of a basic drug, propranolol, was achieved at a micro liquid-liquid interface, using α(1)-acid-glycoprotein (AGP) as a chiral acute phase plasma protein. When the protein is added to an aqueous phase containing the enantiomers of propranalol hydrochloride, the binding of (S)- and (R)-propranolol hydrochloride to the protein results in a decrease in the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) current responses corresponding to the decrease in transfer of propranolol at an aqueous-1,2-dichloroethane interface. This decrease is a consequence of the complexation of the drug and the protein. The complex drug-protein does not transfer across the interface nor changes the transfer potential of the uncomplexed form of propranolol enantiomers. The bound concentration of propranolol enantiomers in the presence of AGP was found to be greater for (S)-propranolol than (R)-propranolol for solutions containing constant concentrations of AGP (50 μM). Scatchard analysis yielded association constants of 2.7 and 1.3 × 10(5) M(-1) for (S)- and (R)-propranolol, respectively.

Binding of benzodiazepine drugs to bovine serum albumin: a second derivative spectrophotometric study

The binding constants (K values) of three benzodiazepine drugs to bovine serum albumin were determined by a second derivative spectrophotometric method. Despite the sample and reference samples were prepared in the same way to maintain the same albumin content in each sample and reference pair, the absorption spectra show that the baseline compensation was incomplete because of the strong background signals caused by bovine serum albumin. Accordingly, further quantitative spectral information could not be obtained from these absorption spectra. On the other hand, the calculated second derivative spectra clearly show isosbestic points indicating the complete removal of the residual background signal effects. Using the derivative intensity differences (ΔD values) of the studied benzodiazepine drugs before and after the addition of albumin, the binding constants were calculated and obtained with R.S.D. of less than 8%. The interactions of drugs with bovine serum albumin were investigated using Scatchard's plot. In addition, the consistency between the fractions of bound benzodiazepine calculated from the obtained K values and the experimental values were established. The results indicate that the second derivative method can be advantageously applicable to the determination of binding constants of drugs to serum albumin without prior separation. Moreover, the validity of the proposed method was confirmed.

Study on the Interaction between the chiral drug of propranolol and α1-acid glycoprotein by fluorescence spectrophotometry

The interaction between the chiral drug of propranolol (PPL) and alpha1-acid glycoprotein (AGP, orosomucoid) has been first studied by fluorescence spectrophotometry. The fluorescence intensity of PPL increased due to the addition of AGP into PPL. The equation of Scatchard was employed to calculate the association constant and binding site number of the two enantiomers with AGP. The association constant is 2.62 x 10(5)M-1 for R-PPL and 8.57 x 10(5)M-1 for S-PPL and the binding site number is 0.41 for R-PPL and 1.17 for S-PPL at 17 degrees C respectively. The method of thermodynamics was applied to determine the binding type of S-PPL with AGP. The results suggested that the binding type is mainly van der waals force or hydrogen bond. At last the effect of three metal cations on the association constant and the binding site number of S-PPL with AGP was examined.

Bioanalytical interaction studies executed by preincubation affinity capillary electrophoresis

The versatility of CE is beneficial for the study of many types of molecular interactions, because different experimental designs can be made to suit the characteristics of a particular interaction. A very versatile starting point is the preequilibration type of affinity CE that has been used extensively for characterizing biomolecular interactions in the last 15 years. We review this field here and include a comprehensive overview of the existing preincubation ACE modes including their advantages and limitations as well as the methodological developments and applications within the bioanalytical field.

Differential binding of disopyramide and warfarin enantiomers to human alpha(1)-acid glycoprotein variants

AIMS

The F1S and A genetic variants of alpha1-acid glycoprotein (AAG) change under various physiological and pathological conditions. They also vary in their drug binding abilities. We have studied the stereoselective binding ability of each of the AAG variants using enantiomers of disopyramide (DP) and warfarin (WR).

METHODS

The AAG variants were separated by hydroxyapatite chromatography. Binding of drug enantiomers to the AAG variants was studied by the Hummel-Dreyer method. The characteristics of the binding activities were examined by Scatchard plot analysis. The first five amino-terminal amino acids (residues 112-116) of the cyanogen bromide (CNBr) fragment (residues 112-181) of each of the separated AAG fractions were elucidated by Edman degradation.

RESULTS

Commercial AAG was separated into two main fractions. Residues 112-116 of fraction 2 were identical to the amino acid sequences predicted from the AAG A gene, LAFDV, and encode the F1S variant. In fraction 3, the deduced amino acid sequence of the AAG B gene, FGSYL, was established, and encodes the A variant. The binding affinities of both DP enantiomers in fraction 3 were significantly higher than those in fraction 2. The differences between dissociation constants (Kd) in fractions 2 and 3 were 5.2-fold for (S)-DP (P < 0.05) and 3.7-fold for (R)-DP (P < 0.001). The dissociation constant of (S)-DP (0.39 +/- 0.08 micro m) was lower than that of (R)-DP (0.53 +/- 0.10 micro m) in fraction 3 [95% confidence interval (CI) - 0.282, - 0.010; P < 0.05], although the binding activities of the DP enantiomers were almost the same in fraction 2. By contrast WR enantiomers had a higher binding affinity in fraction 2 than in fraction 3, the differences in dissociation constants between fractions 2 and 3 being 12.6-fold for (S)-WR (P < 0.001) and 8.3-fold for (R)-WR (P < 0.001). The dissociation constant of (S)-WR (0.28 +/- 0.10 microm) was significantly lower than that of (R)-WR (0.48 +/- 0.08 microm) in fraction 2 (95% CI - 0.369, - 0.028; P < 0.05), but there were no significant differences between the binding activities of WR enantiomers in fraction 3.

CONCLUSIONS

DP and WR enantiomers bind preferentially to fraction 3 and fraction 2, respectively. Fractions 2 and 3 are encoded by the AAG A and the AAG B genes, respectively.

Capillary electrophoretic study on pH dependence of enantioselective disopyramide binding to genetic variants of human alpha1-acid glycoprotein

A high-performance frontal analysis-capillary electrophoresis (HPFA-CE) method was applied to investigate the effect of pH on the drug binding properties of genetic variants of human alpha1-acid glycoprotein (AGP), A variant and a mixture of F1S variants. The unbound concentrations of a model basic drug, disopyramide (DP), in A variant solutions and in F1S variant solutions were measured by HPFA-CE to evaluate binding constants at pH 4.0, 5.0, 6.0 and 7.4. The binding between DP and A variant was gradually weakened by acidification of background buffer (from pH 7.4 to 4.0), while the binding between DP and FIS variants decreased at first (from pH 7.4 to 6.0), and then gained (from pH 6.0 to 4.0). Consequently, DP was more strongly bound to A variant than to FIS variants at pH 7.4, while at pH 4.0 DP was more strongly bound to F1S variants. At any pH (S)-DP was bound more strongly than (R)-DP, and the enantioselectivity of A variant was significantly higher than that of F1S variants. Electrophoretic mobilities of the AGP genetic variants decreased along with a decrease in pH. Fluorescent emission of these genetic variants indicated a distinct conformational change between pH 5.0 and 4.0. However, there was no significant difference in the electrophoretic mobility and the fluorescent emission spectrum between these variants at any pH. On the other hand, circular dichroism analyses revealed that beta-sheet content in FIS variants diminished as pH decreased, while that in A variant increased. These results suggest that the conformational change induced by acidification of background buffer differs between these genetic variants, and this causes the difference in DP bindability.

Effect of dextran as a run buffer additive in drug-protein binding studies using capillary electrophoresis frontal analysis

The study of drug-protein interactions by capillary electrophoresis frontal analysis requires establishment of a sufficient mobility difference between the mobility of the ligand and protein. The potential utility of dextran as a run buffer additive to manipulate the electrophoretic mobilities of low molecular weight ligands and protein in capillary electrophoresis frontal analysis binding studies was assessed. It was demonstrated that dextran was effective in improving the separation between the ligands warfarin and flurbiprofen and human serum albumin. Separation of ligand and protein increased with the concentration of added dextran (0-7.5% (w/w)), while molecular weight of the additive (70,000-2,000,000) only had a minor effect. The effect of dextran addition on viscosity and electrophoretic and electroosmotic mobilites was systematically studied. Optimal frontal analysis settings were a compromise between achieving satisfactory separation and acceptable analysis times without loss of plateau peak conditions. No effect of dextran upon the drug-human serum albumin interactions could be detected for the model ligands. Introduction of dextran into the electrophoresis buffer expands the applicability of capillary electrophoresis frontal analysis in drug research to binding interactions between proteins and low molecular weight ligands possessing similar electrophoretic mobilities.

Evalution of capillary electrophoresis-frontal analysis for the study of low molecular weight drug-human serum albumin interactions

Capillary electrophoresis frontal analysis was applied to 12 low molecular weight compounds including 8 drug substances displaying a range of different properties with respect to binding affinity, binding location, structure, lipophilicity, charge at physiological pH, and electrophoretic mobility. It was found that capillary electrophoresis frontal analysis can be used as a general method to study and quantify drug-human serum albumin interactions. The binding parameters obtained were consistent with literature values. Dextran was in some cases added to the run buffer to improve separation of the drug and human serum albumin plateau peaks. Results indicate that mobility differences between free and complexed human serum albumin give rise to only minor errors. Capillary electrophoresis frontal analysis was also found applicable to the study of human serum albumin drug displacement reactions. Low sensitivity of the UV-detection system was found to be the major limitation of capillary electrophoresis frontal analysis. The method is simple, and minimal effort has to be put into method development, which makes it well suited for screening in early drug development.

Plasma protein binding study of oxybutynin by high-performance frontal analysis

Plasma protein binding of oxybutynin (OXY) was investigated quantitatively and enantioselectively using high-performance frontal analysis (HPFA). An on-line HPLC system which consists of HPFA column, extraction column and analytical column was developed to determine the unbound concentrations of OXY enantiomers in human plasma, in human serum albumin (HSA) solutions, and in human alpha1-acid glycoprotein (AGP) solutions. OXY is bound in human plasma strongly and enantioselectively. The bound drug fraction in human plasma containing 2-10 microM (R)- or (S)-OXY was higher than 99%, and the unbound fraction of (R)-OXY was 1.56 times higher than that of (S)-isomer. AGP plays the dominant role in this strong and enantioselective plasma protein binding. The total binding affinities (nK) of (R)- and (S)-OXY to AGP were 6.86 x 10(6) and 1.53 x 10(7) M(-1), respectively, while the nK values of (R)- and (S)-OXY to HSA were 2.64 x 10(4) and 2.19 x 10(-4) M(-1), respectively. The binding affinity of OXY to AGP is much higher than that to HSA, and shows high enantioselectivity (SIR ratio of nK values is 2.2). It was found that both enantiomers are bound competitively at the same binding site on an AGP molecule. The binding property between OXY and low density lipoprotein (LDL) was investigated by using the frontal analysis method incorporated in high-performance capillary electrophoresis (HPCE/FA). It was found the binding is non-saturable and non-enantioselective.

Frontal analysis of drug-plasma lipoprotein binding using capillary electrophoresis

High performance frontal analysis coupled with capillary electrophoresis (HPFA/CE) was applied to the ultramicroanalysis of enantioselective binding of drug to plasma lipoproteins. A small volume (ca. 80 nl) of (R)- or (S)-propranolol (PRO, 25-150 microM) and human high-density lipoprotein (HDL, 2.63 g/l) or human low-density lipoprotein (LDL, 4.37 g/l) mixed solution, which was in the state of binding equilibrium, was introduced hydrodynamically into a non-coated fused silica capillary. Positively charged unbound PRO enantiomers migrated toward cathodic end much faster than negatively charged lipoproteins and the bound form. Once unbound PRO migrated apart from lipoprotein, the bound PRO was quickly released from the lipoprotein to maintain the binding equilibrium. Thus, PRO migrated as a zone in the capillary, giving a peak with a plateau region, where the concentration is the same as the unbound PRO concentration in the original sample solution. The unbound PRO concentration calculated form the plateau height agreed with that determined by a conventional ultrafiltration method used as a reference method. It was found that the bindings of PRO to HDL and PRO to LDL were not enantioselective, while the total binding affinity of PRO to LDL (4.01 x 10(5) per M) was 17 times higher than that of PRO-HDL binding (2.38 x 10(4) per M).

Effect of oxidation of low-density lipoprotein on drug binding affinity studied by high performance frontal analysis-capillary electrophoresis

The effect of oxidation of low-density lipoprotein (LDL) on the enantioselective drug binding affinity was investigated using high performance frontal analysis--capillary electrophoresis (HPFA-CE). Verapamil and nilvadipine enantiomers were used as the chiral model drugs. LDL was oxidized with copper sulfate for 0, 0.5, 1, 2, and 12 h at 37 degrees C. The HPFA-CE method enabled microdetermination of unbound drug concentrations in native and oxidized LDL solutions. It was found that the bindings between LDL and the model drugs were not enantioselective at any oxidation stage. The total binding affinity (nK) between LDL and verapamil enantiomers was increased by 3.3-, 4.6-, 7.0-, and 19-fold after 0.5, 1, 2, and 12 h oxidation, respectively, whereas the nK value between nilvadipine and LDLwas increased by 1.3-, 1.4-, 1.4-, and 1.7-fold in the same reaction times, respectively. These results indicate that the LDL oxidation enhances the drug binding affinity, and the affinity of verapamil is increased more sensitively than that of nilvadipine. The nK value of each model drug increased steeply after the first 2 h oxidation, followed by the gradual increase after the next 10 h oxidation. It is considered that the net increase in the negative charges and/or the formation of hydroperoxides in the first 2 h oxidation enhances the drug-LDL binding more significantly than the formation of aldehydes or Schiff bases in the following 10 h oxidation.

Recent developments in chiral capillary electrophoresis and applications of this technique to pharmaceutical and biomedical analysis

This paper provides an overview of the current status of chiral capillary electrophoresis (CE). The emphasis is placed on the application of CE in chiral separation of various racemic compounds. During the last two years about 280 papers, several review articles, and two entire issues, edited by S. Fanali (Electrophoresis 1999, 20, 2577-2798, and H. Nishi and S. Terabe (J. Chromatogr. A 2000, 879, 1-471.) have been devoted to chiral CE. Enantiomeric separations of various compounds, e.g., pharmaceuticals, drug candidates, drugs and related metabolites in biological fluids, amino acids, di- and tri peptides, pesticides and fungicides, have been performed using different chiral selectors. Native and derivatized cyclodextrins continue to be the most widely used chiral selectors. Other chiral selectors such as natural and synthetic chiral micelles, crown ethers, chiral ligands, proteins, oligo- and polysaccharides, and macrocyclic antibiotics have also been applied to chiral CE separations.

Chromium(III)-mediated structural modification of glycoprotein: impact of the ligand and the oxidants

The interaction of three types of chromium(III) complexes, [Cr(salen) (H2O2]+, [Cr(en)3]3+, and [Cr(EDTA) (H2O)]- with AGP has been investigated. [Cr(salen) (H2O2]+, [Cr(en)3]3+ and [Cr(EDTA) (H2O]- bind to Human alpha1-acid glycoprotein with a protein:metal ratio of 1:8, 1:6, and 1:4, respectively. The binding constant, K(b) was estimated to be 1.37 +/- 0.12 x 10(5) M(-1), 1.089 +/- 0.05 x 10(5) M(-1) and 5.3 +/- 0.05 x 10(4) M(-1) for [Cr(salen) (H2O2]+, [Cr(en)3]3+, and [Cr(EDTA) (H2O)]-, respectively. [Cr(en)3]3+ has been found to induce structural transition of AGP from the native twisted beta sheet to a more compact alpha-helix. The complexes, [Cr(salen) (H2O2]+ and [Cr(EDTA) (H2O]-, in the presence of H2O2, have been found to bring about nonspecific cleavage of AGP, whereas [Cr(en)3]3+ does not bring about any protein damage. Treatment of [Cr(salen) (H2O)2]+-protein adduct with iodosyl benzene on the other hand led to site specific cleavage of the protein. These results clearly demonstrate that protein damage brought about by chromium(III) complexes depends on the nature of the coordinated ligand, nature of the metal complex, and the nature of the oxidant.

Capillary electrophoresis of sialic acid-containing glycoprotein. Effect of the heterogeneity of carbohydrate chains on glycoform separation using an alpha1-acid glycoprotein as a model

alpha1-Acid glycoprotein (AGP) showed multiple peaks on separation using capillary electrophoresis in a chemically modified capillary with dimethylpolysiloxane at slightly acidic conditions. We analyzed glycoforms of AGP species after separation by ion-exchange chromatography, Con A affinity chromatography, and Cu(II)-chelating affinity chromatography. The AGP species thus obtained were digested with N-glycosidase F, and the released carbohydrate chains were analyzed by high-performance liquid chromatography after labeling with 3-aminobenzoic acid. The results afforded basic information on the contribution of carbohydrate chains to the separation mechanism of glycoforms of AGP by capillary electrophoresis. In addition, we describe an easy method for AGP analysis in serum samples using the electrokinetic injection.

Methods for the determination of binding constants by capillary electrophoresis

Apparent equilibrium constants for molecular association (e.g., association constants, binding constants, dissociation constants, partition coefficients) can be determined with a variety of different capillary electrophoresis (CE) approaches. In many cases, the investigated association behavior is between a smaller molecule or ion (i.e., the solute, drug, or analyte of interest) and a larger entity (e.g., proteins, micelles, polymers, chiral selectors such as cyclodextrins, etc.). Each experimental approach has advantages and disadvantages. Frequently, it is the nature of the system being evaluated that determines the optimal experimental approach. Six different CE-based techniques for evaluating binding constants are reviewed. Examples of each method, and recent references on its use are given.

Role of biantennary glycans and genetic variants of human alpha1-acid glycoprotein in enantioselective binding of basic drugs as studied by high performance frontal analysis/capillary electrophoresis

PURPOSE

To establish a clear understanding of the role of biantennary branching glycans and genetic variants of alpha1-acid glycoprotein (AGP) in enantioselective bindings of basic drug.

METHODS

Human native AGP was separated using concanavalin A affinity chromatography into two subfractions, the unretained fraction (UR-AGP, defect of biantennary glycan) and the retained fraction (R-AGP, possessing biantennary glycan(s)). Imminodiacetate-copper (II) affinity chromatography was used to separate human native AGP into A variant and a mixture of F1 and S variants (F1*S variants). The mixed solutions of the (R)- or (S)-isomer of the model drugs (15 microM disopyramide (DP) or 30 microM verapamil (VER)) and 40 microM of respective AGP species were subjected to high-performance frontal analysis/capillary electrophoresis (HPFA/CE) to determine the unbound drug concentrations.

RESULTS

The unbound concentrations (Cu) of DP in UR-AGP solutions were lower than those in R-AGP solutions, whereas there was no significant difference in the enantiomeric ratios (Cu(R)/Cu(S)) of DP between UR- and R-AGP solutions. In case of genetic variant, the Cu(R)/Cu(S) values of DP in F1*S and A solutions were 1.07 and 2.37, respectively. On the other hand, the enantiomeric ratio of VER in F1*S and A variant solutions were 0.900 and 0.871, respectively.

CONCLUSIONS

The biantennary glycan structures are related to binding affinity of DP to AGP, but not responsible for the enantioselectivity. Genetic variants give significant effect on the enantioselectivity in DP binding, but not in VER binding.

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.

Cleavage of human orosomucoid by a chromium(V) species: relevance in biotoxicity of chromium

A chromium(V) complex, CrO(salen)+, was generated in situ and its interaction with human orosomucoid (alpha1-acid glycoprotein) has been evaluated. The chromium(V) species has been found to oxidize the protein rapidly. A second order rate constant of 5 +/- 0.4 x 10(4) M(-1) s(-1) has been obtained for the redox process. Gel electrophoresis pattern of AGP in the presence of metal ion clearly reveals the decrease in the intensity of the AGP band with the subsequent formation of protein fragments of lower molecular weight. At higher metal ion concentration a continuous smear is observed which indicates the nonselective cleavage of the glycoprotein. Cleavage of AGP is through the direct pathway of oxidation by a highly reactive chromium(V) species.

Enantioselective binding of propranolol, disopyramide, and verapamil to human alpha(1)-acid glycoprotein

We investigated the binding of propranolol (PL), disopyramide (DP), and verapamil (VP) enantiomers by human alpha(1)-acid glycoprotein (AGP; also called orosomucoid) and the relationships between the extent of drug binding and lipophilicity, desialylation, and genetic variants of AGP. Desialylation had little effect on the affinity of AGP for the drugs tested. The percentage binding correlated significantly with the partition coefficients for the drugs tested. Each enantiomer was competitively displaced from AGP by another enantiomer of the same drug, suggesting that they bind to the same site. However, the enantiomers bound to AGP with stereospecific affinities; the (-)-isomers of DP and VP had higher Kd values (4.27 and 4.97 microM, respectively) than the (+)-isomers (1.51 and 2.48 microM, respectively). When enantiomers of the different drugs were used in competitive binding experiments, VP binding was only partially inhibited by DP. This result suggested that drug binding is specific to different variants of AGP (A, F1, S). DP was found to specifically bind to variant A, whereas PL and VP bind to both A and F1/S variants.

Enantioselective binding analysis of verapamil to plasma lipoproteins by capillary electrophoresis-frontal analysis

Capillary electrophoresis coupled with frontal analysis was applied to the study of enantioselective binding of verapamil (VER) to plasma lipoproteins. The drug-lipoprotein mixed solution, which had been in the binding equilibrium, was hydrodynamically introduced into a non-coated fused-silica capillary. Since VER is positively charged in the neutral run buffer (pH 7.4), the unbound VER enantiomers migrated toward the cathodic end much faster than negatively charged lipoproteins and their bound forms. Once unbound VER migrated apart from lipoprotein, the bound VER was quickly released from the protein to maintain the binding equilibrium. Thus, VER migrated as a zone through the capillary and gave a trapezoidal peak with a plateau region on the electropherogram. The VER concentration in this plateau region was equal to the unbound VER concentration in the initial sample solution. It was found that the bindings of VER to high-density lipoprotein (HDL), low-density lipoprotein (LDL) and oxidized LDL were not site-specific and not enantioselective. Partition-like binding to lipid part of these lipoproteins seemed to be dominant. The total binding affinities of LDL to VER were about seven-times stronger than those of HDL, and the oxidation of LDL by copper ion enhanced the binding affinities significantly.

Binding analysis of nilvadipine to plasma lipoproteins by capillary electrophoresis-frontal analysis

Capillary electrophoresis coupled with frontal analysis (HPCE/FA) was applied to the ultramicro analysis of enantioselective binding of nilvadipine (NV), a calcium channel blocker, to plasma lipoproteins. The drug lipoprotein mixed solution was hydrodynamically introduced into a non-coated fused silica capillary for capillary electrophoresis. Since NV has no electric charge in the run buffer (pH 7.4), the unbound NV moved towards the cathodic end by electroosmotic flow, which was faster than the electrophoretic migrations of negatively charged lipoproteins and the bound NV. Once unbound NV migrated apart from lipoprotein, and bound NV was quickly released from the protein to maintain the binding equilibrium. Thus, NV migrated as a zone with a plateau region. The concentration of NV in this plateau region appearing on the electrophorogram was the same as the unbound NV concentration in the initial sample solution. It was found that the binding of NV to high-density lipoprotein (HDL), low-density lipoprotein (LDL) and oxidized LDL was non-specific and not enantioselective. Partition-like binding to the lipid part of these lipoproteins seemed to occur dominantly. The total binding affinities of NV to LDL were about seven times stronger than those to HDL, and the oxidation of LDL enhanced the binding affinity significantly.

Capillary electrophoresis of drugs: current status in the analysis of pharmaceuticals

The current status of capillary electrophoresis (CE) in pharmaceutical analyses is reviewed with about 300 references, mainly from 1996 until 1999. This article covers the use of CE for assay and purity determination of the main component, analysis of natural medicines, antisense DNA, peptides, and proteins. Analysis of hydrophobic and/or electrically neutral drugs by electrokinetic chromatography, capillary electrochromatography and nonaqueous CE is critically evaluated. Detailed techniques for the separation of enantiomers are given in the text with some actual applications. Furthermore, this review includes sensitivity and regulatory aspects for the actual use of CE in new drug applications (NDA). The analytical validation required for CE in NDA is also treated.

Recent developments in capillary zone electrophoresis of proteins

This review article with 125 references describes recent developments in capillary zone electrophoresis of proteins. It encompasses approximately the last two years, from the previous review (V. Dolník, Electrophoresis 1997, 18, 2353-2361) through Spring 1999. Topics covered include modeling of the electrophoretic properties of proteins, sample preconcentration and derivatization, wall coatings, improving selectivity, special detection techniques, and applications.