Gene expression and metabolic activity of Streptococcus mutans during exposure to dietary carbohydrates glucose, sucrose, lactose, and xylitol

Recent RNA sequencing studies have given us a deeper insight into the cariogenic impact of carbohydrate sources in the bacterium Streptococcus mutans, the principal microbial agent in dental caries etiopathogenesis. The process of dental caries development is facilitated by the ability of this bacterium to ferment some carbohydrates into organic acids contributing to a pH decrease in the oral cavity and the demineralization of the hard tissues of the tooth. Furthermore, in dental caries progression, biofilm formation, which starts and ends with free planktonic cells, plays an important role and has several unique properties called virulence factors. The most cariogenic carbohydrate is sucrose, an easily metabolizable source of energy that induces the acidification and synthesis of glucans, forming typical bacterial cell clumps. We used multifaceted methodological approaches to compare the transcriptomic and metabolomic profiles of S. mutans growing in planktonic culture on preferred and nonpreferred carbohydrates and in fasting conditions. Streptococcus mutans in a planktonic culture with lactose produced the same pH drop as glucose and sucrose. By contrast, xylitol and lactose showed high effectiveness in regulating intracellular polysaccharide metabolism, cell wall structure, and overall virulence involved in the initial phase of biofilm formation and structure but with an opposite pattern compared with sucrose and glucose. Our results confirmed the recent findings that xylitol and lactose play a vital role in biofilm structure. However, they do not reduce its formation, which is related to the creation of a cariogenic environment.

Non-Invasive Human Embryo Metabolic Assessment as a Developmental Criterion

The selection of a highly-viable single embryo in assisted reproductive technology requires an acceptable predictive method in order to reduce the multiple pregnancy rate and increase the success rate. In this study, the metabolomic profiling of growing and impaired embryos was assessed on the fifth day of fertilization using capillary electrophoresis in order to find a relationship between the profiling and embryo development, and then to provide a mechanistic insight into the appearance/depletion of the metabolites. This unique qualitative technique exhibited the appearance of most non-essential amino acids and lactate, and depleting the serine, alanyl-glutamine and pyruvate in such a manner that the embryos impaired in their development secreted a considerably higher level of lactate and consumed a significantly higher amount of alanyl-glutamine. The different significant ratios of metabolomic depletion/appearance between the embryos confirm their potential for the improvement of the prospective selection of the developed single embryos, and also suggest the fact that pyruvate and alanyl-glutamine are the most critical ATP suppliers on the fifth day of blastocyst development.

Nonlinear regression models for determination of nicotinamide adenine dinucleotide content in human embryonic stem cells

Recent evidence suggests that energy metabolism contributes to molecular mechanisms controlling stem cell identity. For example, human embryonic stem cells (hESCs) receive their metabolic energy mostly via glycolysis rather than mitochondrial oxidative phosphorylation. This suggests a connection of metabolic homeostasis to stemness. Nicotinamide adenine dinucleotide (NAD) is an important cellular redox carrier and a cofactor for various metabolic pathways, including glycolysis. Therefore, accurate determination of NAD cellular levels and dynamics is of growing importance for understanding the physiology of stem cells. Conventional analytic methods for the determination of metabolite levels rely on linear calibration curves. However, in actual practice many two-enzyme cycling assays, such as the assay systems used in this work, display prominently nonlinear behavior. Here we present a diaphorase/lactate dehydrogenase NAD cycling assay optimized for hESCs, together with a mechanism-based, nonlinear regression models for the determination of NAD(+), NADH, and total NAD. We also present experimental data on metabolic homeostasis of hESC under various physiological conditions. We show that NAD(+)/NADH ratio varies considerably with time in culture after routine change of medium, while the total NAD content undergoes relatively minor changes. In addition, we show that the NAD(+)/NADH ratio, as well as the total NAD levels, vary between stem cells and their differentiated counterparts. Importantly, the NAD(+)/NADH ratio was found to be substantially higher in hESC-derived fibroblasts versus hESCs. Overall, our nonlinear mathematical model is applicable to other enzymatic amplification systems.

[The new technologies for the analytical examination of the embryonic metabolome and its prospects]

OBJECTIVE

To review current technologies for the analytical examination of the embryonic metabolome and its perspectives.

DESIGN

Review article.

SETTING

Department of Gynecology and Obstetrics, Faculty of Medicine, Masaryk University, and University Hospital, Brno, Department of Biochemistry, Faculty of Science and CEITEC, Masaryk University, Brno.

METHODS AND RESULTS

Nowadays, very sensitive analytical technologies are available. They enable exact measurement of various molecules - products of embryo metabolism during first days of cultivation. The capillary electrophoresis is one of promising method. Recent studies analysed metabolic differences between embryos that result in a pregnancy and those that do not. Amino acid levels, glucose or pyruvate in the embryo culture media were analysed most frequently. However, results of these studies are ambiguous.

CONCLUSIONS

The capillary electrophoresis with contactless conductivity detection may provide a useful data of the embryonic metabolome. A comprehensive analysis of the used culture medium may represent a valuable adjunct to morphological criteria for enhanced rates of implantation and delivery.

Capillary zone electrophoresis with field enhanced sample stacking as a tool for targeted metabolome analysis of adenine nucleotides and coenzymes in Paracoccus denitrificans

The main aim of this work was to demonstrate the applicability of capillary zone electrophoresis in combination with field enhanced sample stacking in targeted metabolome analyses of adenine nucleotides--AMP, ADP, ATP, coenzymes NAD(+), NADP(+) and their reduced forms in Paracoccus denitrificans. Sodium carbonate/hydrogencarbonate buffer (100 mM, pH 9.6) with the addition of beta-CD at a concentration of 10 mM was found to be an effective BGE for their separation within 20 min. Besides this, special attention was paid to the development of the procedure for the extraction of specific metabolites from the bacterium P. denitrificans. This procedure was not only optimised to achieve the highest metabolite yields but also to obtain a sample that was fully compatible with the online preconcetration strategy used. The developed methodology was finally applied in a study of the bacterium P. denitrificans at various stages of the active respiratory chain.

Integration of short-end injection mode into electrophoretically mediated microanalysis

The possibility of integration of the short-end injection mode in the EMMA methodology is demonstrated in this work on the kinetic studies of haloalkane dehalogenase and rhodanese enzymatic reactions. The essential validations of the EMMA methods combined with the short-end and long-end injection modes were performed first to confirm their accuracy. The qualitative and quantitative parameters of both approaches such as repeatabilities of migration times and peak areas, limits of detection and correlation coefficients were in acceptable ranges. In addition, estimated Michaelis constants for the corresponding substrate(s) were comparable being in accordance with previous literature data. Moreover, the ping-pong reaction mechanism of rhodanese reaction was confirmed by means of both injection modes. This combination thus preserves the benefits of these instrumental approaches. Whereas the short-end injection procedure brought 5-6.5 times reduction of the analysis time and 2.5-4 times increase of the sensitivity, the EMMA methodology allowed full automatization of the assays while the whole kinetic studies needed only 20 microl of corresponding enzyme preparation.

HPLC determination of midazolam and its three hydroxy metabolites in perfusion medium and plasma from rats

A new, simple, rapid, sensitive, and repeatable isocratic reverse-phase HPLC method was developed and validated for simultaneous determination of midazolam and its main three hydroxylated metabolites, i.e. 1'-hydroxymidazolam, 4-hydroxymidazolam, and 1',4-dihydroxymidazolam in rat liver perfusate and also plasma. Diazepam was used as an internal standard to ensure precision and accuracy of this method. Analytes were extracted from alkalinized samples into diethyl ether using single-step liquid-liquid extraction. A C18 analytical column and a mobile phase composed of acetonitrile and sodium acetate buffer were used for the chromatographic separation with UV detection. Limits of detection varied between 7.9 and 19.6 microg/L for midazolam and its hydroxy metabolites. The overall recovery for the analytes exceeded 92%, for concentrations twice the limits of detection. The intra- and inter-day precision at three different concentrations never exceeded 8 and 11% variation, respectively. This method is applicable for modeling and description of possible pharmacological interactions on rat (CYP3A1/2) or human (CYP3A4/5) cytochrome P450 enzymes.

Study of substrate inhibition by electrophoretically mediated microanalysis in partially filled capillary

Substrate inhibition is a common phenomenon in enzyme kinetics. We report here for the first time its study by a combination of the electrophoretically mediated microanalysis (EMMA) methodology with a partial filling technique. In this setup, the part of capillary is filled with the buffer best for the enzymatic reaction whereas, the rest of the capillary is filled with the background electrolyte optimal for separation of substrates and products. In the case of haloalkane dehalogenase, a model enzyme selected for this study, the enzymatic reaction was performed in 20 mM glycine buffer (pH 8.6) whereas 20 mM beta-alanine-hydrochloric acid buffer (pH 3.5) was used as a background electrolyte in combination with direct detection at 200 nm. The whole study was performed on poorly soluble brominated substrate--1,2-dibromoethane. As a result it was first necessary to find the compromise between the concentrations of the enzyme and the substrate preserving both the adequate sensitivity of the assay and at the same time the attainable substrate solubility. By means of the developed EMMA methodology we were able to determine the Michaelis constant (K(M)) as well as the substrate inhibition constant (K(SI)). The value of K(M) and K(SI) obtained were 7.7+/-2.5 mM and 1.1+/-0.4 mM, respectively. Observation of the substrate inhibition of haloalkane dehalogenase by 1,2-dibromoethane is in accordance with previous literature data.

Study of recombinant cytochrome P450 2C9 activity with diclofenac by MEKC

Cytochrome P450 2C9 (CYP2C9) is one of the most important isoforms in human liver involved in the metabolism of a large number of therapeutic agents. The aim of this paper is to demonstrate the applicability of CE for the determination of the enzymatic activity of CYP2C9 with diclofenac as a probe substrate. MEKC with SDS as a pseudostationary phase was used for this purpose. Compared to other assays, the MEKC-based method is rapid, can be automated and requires only a small quantity of enzymes and substrate. Moreover, the enzymatic reaction can be monitored with high sensitivity and repeatability even when the reaction mixture is used for the analysis without any pretreatment. The kinetic study on the given enzymatic reaction was also performed since the basic characterization of drug biotransformation generally begins with the enzyme kinetic analysis of metabolite formation. As a result, the Michaelis constant and maximum reaction velocity were evaluated, the values 3.44 +/- 0.45 microM and 19.78 +/- 0.76 nmol min(-1) nmol(-1), respectively, were in agreement with the literature data. On the other hand, a slight deviation from typical Michaelis-Menten kinetics with a weak positive cooperativity was found at diclofenac concentrations below 2 microM. The same atypical kinetic behavior of CYP2C9 was also observed by other authors.

Separation of microcystins by capillary electrochromatography in monolithic columns

Contribution on microcystin variant analysis by capillary electrochromatography (CEC) with easily affordable spectrophotometric detection is presented. Two types of reversed-phase capillary columns formed by inorganic or organic polymer monoliths were prepared for this purpose. The analyses were performed isocratically by means of tris(hydroxymethyl) aminomethane (TRIS) buffers of mildly alkaline pH containing 30% (v/v) acetonitrile as the mobile phases. The samples were injected electrokinetically and the analyses were done at the same separation field strength of 500 V/cm. Microcystins were detected at 238 nm. Although both column types differ not only in monolith quality (inorganic versus organic) but also in the length of the aliphatic moiety (C8 versus C12) similar results were achieved. The on-column preconcentration as the encouraging prospect of electrochromatographic technique was also tested. Consequently 5% of column volume was injected in contrast with 0.5% at standard injection scheme resulting in the six times enrichment of the low concentrated cyanobacterial extract at the top of the separation column. From these preliminary results can be seen that the CEC method is fully applicable for rapid microcystin screening.

Determination of cyanide in microliter samples by capillary electrophoresis and in-capillary enzymatic reaction with rhodanese

This paper describes a method for the determination of cyanide using in-capillary enzymatic reaction with rhodanese. Poorly absorbing cyanide is in rhodanese reaction transformed into highly absorbing thiocyanate that is further separated by capillary electrophoresis (CE) and determined spectrophotometrically at 200 nm. Cyanide is thus estimated indirectly from the result of thiocyanate quantification and moreover, it can be easily determined with sufficient sensitivity by means of CE apparatus equipped with common UV detector. The linear detection range for concentration versus peak area for the assay is from 15 to 500 microM (correlation coefficient 0.997) with a detection limit of 3 microM and a limit of quantitation 9 microM. The inter-day reproducibility of the peak area was below 3.2% and the inter-day reproducibility of the migration time below 0.1%. The method is relatively rapid, simple and can be easily automated. Moreover, only limited amount of the sample is required.

Determination of enzymatic activity by capillary electrophoresis

Enzymes are biological catalysts that play an important role in biochemical reactions necessary for normal growth, maturation and reproduction through whole live world. Their accurate quantitation in biological samples is important in many fields of biochemistry, not only in routine biochemistry and in fundamental research, but also in clinical and pharmacological research and diagnosis. Since the direct measurement of enzymes by masses is impossible, they must be quantified by their catalytic activities. Many different methods have been applied for this purpose so far. Although photometric methods are undoubtedly the most frequently used, separation methods will further gain their position in this field. The article reviews different possibilities for the assay of enzymatic activity by means of capillary electrophoresis (CE). Both the off-line and on-line enzyme assays based on CE are discussed.

Electrophoretically mediated microanalysis with partial filling technique and indirect or direct detection as a tool for inhibition studies of enzymatic reaction

The inhibition of the model enzyme, haloalkane dehalogenase from Sphingomonas paucimobilis, was investigated by a combination of electrophoretically mediated microanalysis with a partial filling technique, followed by indirect or direct detection. In this setup, part of the capillary is filled with a buffer suitable for the enzymatic reaction (20 mM glycine buffer, pH 8.6) whereas the rest of the capillary is filled with the background electrolyte optimal for separation of substrates and products. Two different background electrolytes and corresponding detection approaches were used to show the versatility of the developed method. The inhibition effect of 1,2-dichloroethane on the dehalogenation of brominated substrate 1-bromobutane was studied by means of 10 mM chromate - 0.1 mM cetyltrimethylammonium bromide (pH 9.2) in combination with indirect detection or 20 mM beta-alanine - hydrochloric acid (pH 3.5) in combination with direct detection. The method was used to estimate the inhibition constant K(I) (0.44 mM by indirect detection and 0.63 mM by of direct detection) and to determine the inhibition type. Compared to spectrophotometric and other discontinuous assays, the method is rapid, can be automated, and requires only small amount of reagents that is especially important in the case of enzymes and inhibitors.

Study of enzyme kinetics of phenol sulfotransferase by electrophoretically mediated microanalysis

Electrophoretically mediated microanalysis (EMMA) was applied for the study of the kinetic parameters of the enzymatic reaction of phenol sulfotransferase SULT1A1 isoenzyme with 4-nitrophenol as a substrate. The SULT1A1 activity was determined by the quantitation of the product, 4-nitrophenyl sulfate, at 274 nm by using different injection and separation steps. This new approach solved the problem of the presence of the very strong inhibitor, adenosine 3',5'-bisphosphate (PAP), in the co-substrate solution (adenosine 3'-phosphate 5'-phosphosulfate, PAPS) which is unstable at room temperature. The inhibitor PAP was electrophoretically separated from the co-substrate PAPS before the injection of enzyme and substrate inside the capillary (and thus before their in-capillary encountering). With the developed in-capillary SULT1A1 activity assay an average Michaelis constant (Km) for 4-nitrophenol was calculated to be 0.84 microM, a value which is consistent with a previously reported value. Strong substrate inhibition (above a 4-nitrophenol concentration of 2.5 microM) was observed, and this is also in accordance with literature values.

Study of enzymatic reaction by electrophoretically mediated microanalysis in a partially filled capillary with indirect or direct detection

Electrophoretically mediated microanalysis (EMMA), in combination with a partial filling technique and indirect or direct detection, is described for the study of enzymes reacting with the high mobility inorganic or organic anions as substrates or products. Part of the capillary is filled with a buffer optimized for the enzymatic reaction, the rest of the capillary with the background electrolyte being optimal for the separation of substrates and products. With haloalkane dehalogenase, chosen as a model enzyme, the enzymatic reaction was performed in a 20 mM glycine buffer (pH 8.6). Because of the wide substrate specificity of this enzyme, utilizing chlorinated as well as brominated substrates and producing either nonabsorbing chloride or absorbing bromide ions, two different background electrolytes and detection approaches were adopted. A 10 mM chromate-0.1 mM cetyltrimethylammonium bromide background electrolyte (pH 9.2) was used in combination with indirect detection and 20 mM beta-alanine-hydrochloric acid (pH 3.5) in combination with direct detection. The Michaelis constant (K(m)) of haloalkane dehalogenase for 1-bromobutane was determined. The K(m) values 0.59 mM estimated by means of indirect detection method and 0.17 mM by means of direct detection method were comparable with the value 0.13 mM estimated previously by gas chromatography.

Purification and Some Properties of Isocitrate Dehydrogenase fromParacoccus denitrificans

NADP-dependent isocitrate dehydrogenase (ICDH) from the bacterium Paracoccus denitrificans was purified to homogeneity. The purification procedure involved ammonium sulphate fractionation, ion exchange chromatography, and gel permeation chromatography. The specific activity of purified ICDH was 801 nkat/mg, the yield of the enzyme 58%. The purity of the enzyme was checked by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. ICDH is a dimer composed of two probably identical subunits of relative molecular weight 90,000. The pH optimum of the enzyme reaction in the direction of substrate oxidation was found to be 5.6; the presence of Mn2+ is essential for enzyme activity. The absorption and fluorescence spectra of the homogeneous enzyme were measured as well.

Advances in capillary electrophoretically mediated microanalysis

Recent developments in the use of capillary electrophoretic techniques for the in-line study of enzyme reactions and derivatization protocols are reviewed. The article is divided into two parts: (i) in-line enzyme reactions and (ii) in-line derivatization. The first part introduces electrophoretically mediated microanalysis (EMMA) and discusses and illustrates the different modes of EMMA. A literature overview is provided, starting from 1996, and the investigated enzymes are classified into two tables based on the mode of engagement (i.e., continuous or transient) of the developed EMMA-based assay. The second part starts with an introduction of the procedures and the nomenclature used in the area of in-line derivatization protocols based on EMMA. Reported derivatization procedures are discussed and classified in tables, according to the functional group that is derivatized.

Inhibition study of rhodanese by means of electrophoretically mediated microanalysis

A combination of the electrophoretically mediated microanalysis methodology with a partial filling technique was applied for the inhibition study of bovine liver rhodanese by 2-oxoglutarate. In this set-up, part of the capillary is filled with the best buffer for the enzymatic reaction, while the rest of the capillary is filled with the optimal background electrolyte for separation of substrates and products. The estimated value of K1 for 2-oxoglutarate was 3.62 x 10(-4) +/- 1.43 x 10(-4) M with respect to cyanide and 1.40 x 10(-3) +/- 1.60 x 10(-4) M with respect to thiosulfate. In addition, the type of inhibition was also evaluated. The findings of 2-oxoglutarate as the competitive inhibitor with respect to cyanide and as the uncompetitive inhibitor with respect to thiosulfate are in accordance with previous literature data.

Determination of homocysteine in human plasma by micellar electrokinetic chromatography and in-capillary detection reaction with 2,2'-dipyridyl disulfide

We present a new method for homocysteine quantitation in human plasma based on in-capillary reaction of homocysteine with 2,2'-dipyridyl disulfide. Homocysteine is in this so-called thiol-exchange reaction quantitatively transformed in mixed disulfide concomitantly with formation of an equimolar amount of 2-thiopyridone that is further separated by micellar electrokinetic chromatography and determined specifically at 343 nm. The concentration of homocysteine is thus estimated indirectly from the result of 2-thiopyridone determination. The linear detection range for concentration versus peak area for the assay was from 0.03-3 mM (correlation coefficient 0.994) with a detection limit of 6 microM and a limit of quantitation 20 microM. The inter-day reproducibility of the peak area and the migration time were 1.37% and 0.05%, respectively. The method is simple, relatively rapid and can be easily automated. Moreover the common capillary electrophoresis apparatus with a UV detector can be used to distinguish between normal and pathological hyperhomocysteinemia plasma samples.

Application of capillary zone electrophoresis to study the properties of rhodanese from Acidithiobacillus ferrooxidans

A new capillary zone electrophoretic method was applied to the assay of enzymic activity of rhodanese from Acidithiobacillus ferroxidans. The enzyme activity determined by capillary zone electrophoresis was compared with that determined by discontinuous spectrophotometry, the values obtained being in good agreement. The method was also used to evaluate Michaelis constants of cyanide and thiocyanate as substrates; a new approach was developed to solve the problem with variable ionic strength of the samples. The pH and temperature optima for the enzyme were also determined.

Monitoring of dithiothreitol clearance by means of micellar electrokinetic chromatography

A new method for specific determination of dithiothreitol (DTT) using micellar electrokinetic chromatography and on-column reaction with reactive disulfide-2,2'-dipyridyldisulfide is described. DTT in this reaction is quantitatively transformed into a mixed disulfide concomitantly with formation of equimolar amount of the 2-thiopyridone that is further separated by micellar electrokinetic chromatography and determined spectrophotometrically at 343 nm. The concentration of DTT is thus estimated indirectly from the result of 2-thiopyridone determination. The linear detection range for concentration versus peak area for the assay is from 0.05 to 2.5 mM (correlation coefficient 0.993) with a detection limit of 2.5 microM. The inter-day reproducibility of the peak area was 1.35% and the inter-day reproducibility of the migration time 0.56%. The method can be applied for DTT monitoring both in chemical and biological systems.

Determination of the kinetic parameters of rhodanese by electrophoretically mediated microanalysis in a partially filled capillary

Electrophoretically mediated microanalysis (EMMA) was applied for the study of kinetic parameters of the bisubstrate enzymatic reaction of rhodanese. The Michaelis constants (K(m)) for both substrates and the effect of temperature on rhodanese reaction were evaluated by means of the combination of the EMMA methodology with a partial filling technique. In this setup, the part of the capillary is filled with the buffer best for the enzymatic reaction whereas, the rest of the capillary is filled with the background electrolyte optimal for separation of substrates and products. The enzymatic reaction was performed in 25 mM N-(2-hydroxymethyl)piperazine-2'-(2-ethanesulfonic acid) (HEPES) buffer (pH 8.5) while the low pH background electrolyte 100 mM beta-alanine-HCl (pH 3.5) was used for separation of substrates and products that are the inorganic anions. The estimated value of K(m) for thiosulfate of 1.30 x 10(-2) M was consistent with previously published values; the K(m) for cyanide of 7.6 x 10(-3) M was determined for the first time. In addition, the type of kinetic mechanism of enzymatic reaction was also elucidated. The finding of the double displacement (ping-pong) mechanism is in accordance with previous literature data. Also, the experimentally determined temperature optimum of the rhodanese-catalyzed reaction around 20-25 degrees C agreed with literature values.

Determination of lignans in Schisandra chinensis using micellar electrokinetic capillary chromatography

Micellar electrokinetic capillary chromatography (MEKC) has been developed as a promising method for the determination of lignans in plant samples. The separation conditions have been optimized with respect to the different parameters including sodium dodecyl sulfate (SDS) and acetonitrile concentration, pH of the background electrolyte, separation voltage, and capillary temperature. The background electrolyte consisting of 40 mM SDS and 35% acetonitrile in 10 mM tetraborate buffer (pH 9.3) was found to be the most suitable electrolyte for this analysis. The applied voltage of 28 kV (positive polarity) and the capillary temperature 25 degrees C gave the best separation of lignans. The interday reproducibility of the peak areas and the migration times was below 2.0%. The results of MEKC analyses were compared with those obtained by capillary electrochromatography (CEC) and reversed-phase high-performance liquid chromatography (RP-HPLC). The possibilities of using this method for the determination of lignans in drug and in serum samples were also tested.

Analysis of artichoke (Cynara cardunculus L.) extract by means of micellar electrokinetic capillary chromatography

The main constituents of artichoke extract were separated by micellar electrokinetic chromatography (MEKC), using a buffer consisting of 100 mM sodium dodecyl sulfate (SDS) in 20 mM sodium dihydrogen phosphate, 20 mM disodium tetraborate (pH 8.6) as background electrolyte. Optimum separation voltage of 28 kV (positive polarity) and a capillary temperature of 25 degrees C gave the best analysis. The UV detection was performed at 200 nm. The method was successfully used to analyze plant and drug samples as well as for the study of artichoke antioxidant activity. The quantitative MEKC results were in good agreement to those obtained previously by reversed-phase high-performance liquid chromatography (RP-HPLC).

Application of capillary electrochromatography using macroporous polyacrylamide columns for the analysis of lignans from seeds of Schisandra chinensis

Capillary electrochromatography (CEC) using polymer-based monolithic stationary phase has been developed as a promising method for the determination of lignans of Schisandra chinensis. The columns were prepared by in situ copolymerisation of acrylamide, N,N'-methylenebisacrylamide, vinylsulfonic acid and lauryl acrylate in presence of poly(ethylene glycol) as a porogenic agent. The columns [33 cm (24.5 cm effective length) x 75 microm I.D.] were successfully used to analyse and quantify the major lignans in extract of the seeds of Schisandra chinensis. Good separations were achieved in less than 35 min. The calibration graphs were linear in the range 0.025-1.0 mg/ml of given lignan with correlation coefficients between 0.9951 and 0.9996. The inter-day reproducibility of the peak area were below 3.9% and the inter-day reproducibility of the migration time were below 4.2%. The results of quantitative CEC analyses were compared with those obtained by reversed-phase HPLC, the levels of schizandrin, gomisin A, gomisin N and wuweizisu C determined by CEC were in a good agreement with those determined by HPLC.

Analysis of thiocyanate in biological fluids by capillary zone electrophoresis

A new sensitive and simple method has been developed for the determination of thiocyanate in human serum, urine and saliva. The determinations were performed in a fused-silica capillary [64.5 cm (56 cm effective length) x 75 microm] using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity), temperature of capillary 25 degrees C and direct detection at 200 nm. Serum samples were 10-times diluted with deionised water and deproteinised with acetonitrile in the ratio 1:2. Urine and saliva samples need only 20-fold dilution with deionised water. The proposed method was successfully applied to the determination of thiocyanate in various human serum, saliva and urine samples.

Specific thiol determination by micellar electrokinetic chromatography and on-column detection reaction with 2,2'-dipyridyldisulfide

A new method for specific determination of glutathione using micellar electrokinetic chromatography and on-column reaction with 2,2'-dipyridyldisulfide is described. 2,2'-Dipyridyldisulfide and a sample of glutathione are injected consecutively into the capillary as two discrete plugs separated with a short plug of background electrolyte. Due to the differences in the mobilities of the 2,2'-dipyridyldisulfide and glutathione, on-column mixing and reaction occur. Glutathione is in this reaction quantitatively transformed into a mixed disulfide concomitantly with formation of an equimolar amount of the 2-thiopyridone which is further separated by micellar electrokinetic chromatography and determined spectrophotometrically at 343 nm. The concentration of glutathione is thus estimated indirectly from the result of 2-thiopyridone determination.

Determination of haloalkane dehalogenase activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of haloalkane dehalogenase activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of product - bromide or chloride ions - was monitored by sequential capillary zone electrophoresis runs. The determinations were performed in a 75 microm fused-silica capillary using 5 mM chromate, 0.5 mM tetradecyltrimethylammonium bromide (pH 8.4) as a background electrolyte, separation voltage 15 kV (negative polarity) and indirect detection at sample wavelength 315 nm, reference wavelength 375 nm for brominated and chlorinated substrates, respectively 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity) and direct detection at 200 nm for brominated substrates. The temperature of capillary was in both cases 25 degrees C. The method is rapid, can be automated, and requires only small amount of enzyme preparation and substrate.

Determination of pyrroloquinoline quinone by capillary zone electrophoresis

A new method for the determination of pyrroloquinoline quinone by capillary zone electrophoresis has been developed. Separation conditions have been optimised with the respect to different parameters including pH and ionic strength of the background electrolyte, separation voltage and temperature of the capillary. A buffer consisting of 50 mM beta-alanine-HCl pH 3.0 was found to be the most suitable electrolyte for this separation. An applied voltage of 25 kV (negative polarity) and a temperature of 25 degrees C gave the best analysis of pyrroloquinoline quinone. The linear detection range for concentration versus peak area for the assay is from 5 to 500 microM (correlation coefficient 0.9998) with a detection limit of 0.1-0.2 microM. The inter-day reproducibility of the peak area was 2.5% and the inter-day reproducibility of the migration time was below 0.18%.

Determination of rhodanese enzyme activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of rhodanese activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of SCN- was monitored by sequential capillary zone electrophoretic runs. The determinations were performed in a 75-micron fused-silica capillary using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, a separation voltage of 18 kV (negative polarity), a capillary temperature of 25 degrees C and direct detection at 200 nm. Short-end injection or long-end injection procedures were used for sample application. The method is rapid, able to be automated and requires only small amounts of sample and substrates, which is especially important in the case of highly toxic cyanide. The developed capillary electrophoretic method also has great potential for thiocyanate determinations in other applications.

Use of thiopropyl sepharose for the synthesis of an adsorbent for the affinity chromatography of glutathione S-transferase

Thiopropyl Sepharose 6B in the 2-thiopyridyl-activated form was used for the reversible immobilisation of reduced glutathione (GSH). The resulting affinity matrix was successfully tested as a sorbent for the partial purification of glutathione S-transferase (GST) from pig kidney. The specific elution of the enzyme was performed with 10 mM GSH in Tris-HCl buffer (pH 7.8), non-specific elution with 20 mM dithiotreitol (DTT) in the same buffer.

Detection of quinoproteins after electrophoresis in the presence of urea or SDS

A method for the direct detection of quinoproteins in gels after electrophoresis in the presence of urea or SDS has been developed. The conditions of sample preparation and detection were optimized to achieve maximum sensitivity. The method is suitable for the detection of quinoproteins in complex protein mixtures as well as for the characterization of certain enzyme preparations.

Improved chromatographic purification of pea seedlings diamine oxidase

An improved and simplified purification procedure has been developed for the isolation of diamine oxidase from pea seedlings (DAO EC 1.4.3.6). It involves ammonium sulphate precipitation, hydrophobic interaction chromatography, ion-exchange chromatography and size-exclusion chromatography. The homogeneity of the final enzyme preparations and molecular weight were determined by size-exclusion chromatography and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS PAGE). The isoelectric point of 7.35 +/- 0.05 was determined by chromatofocusing and by polyacrylamide gel isoelectric focusing.

Purification and properties of malate dehydrogenase from Paracoccus denitrificans

Affinity chromatography on immobilized Cibacron Blue (Matrex Gel Blue A) gel permeation chromatography on UltroPac TSK G 3000 SWG column and ion-exchange chromatography on "Mono Q" column were used to purify the malate dehydrogenase (MDH) from P. denitrificans to electrophoretic homogeneity. The last two purification steps were performed in FPLC system. The enzyme having a specific activity of about 2300 nkat/mg protein was obtained with an approximate 70% yield. MDH is a dimer with a molecular mass of 80,000 +/- 10,000 and an isoelectric point of 4.85 +/- 0.05. Absorption, fluorescence and CD-spectra were also measured and basic kinetic parameters were obtained for the homogeneous enzyme. The present paper also suggests the possibility of using the prepared enzyme for the determination of aspartate transferase (AST) in blood serum.

Pea (Pisum sativum) diamine oxidase contains pyrroloquinoline quinone as a cofactor

Diamine oxidase was prepared from pea (Pisum sativum) seedlings by a new purification procedure involving two h.p.l.c. steps. We studied the optical and electrochemical properties of the homogeneous enzyme and also analysed the hydrolysed protein by several methods. The data presented here suggest that the carbonyl cofactor of diamine oxidase is firmly bound pyrroloquinoline quinone.