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PubMed1998

Molecular imprint polymers as highly selective stationary phases for open tubular liquid chromatography and capillary electrochromatography.

Chiral separations employing molecular imprint polymer (MIP) stationary phases in both open tubular liquid chromatography (OT-LC) and capillary electrochromatography (OT-CEC) are demonstrated. MIPs are highly crosslinked polymers containing spatial and functionality memory of template molecules which provide a higher degree of selectivity when used as stationary phases for chromatographic separations. Thin films of molecular imprinted polymers bonded to the inner walls of 25 microm ID fused-silica capillaries were prepared using an in situ polymerization technique developed in our laboratory that allows the use of conventional fused-silica capillaries with polyimide outer coatings. The success rate in preparing such open tubular columns was about 70%. Methacrylic acid and 2-vinyl pyridine were chosen as functional monomers, and either ethylene dimethacrylate or trimethylol propane trimethacrylate was used as the crosslinker. Toluene was employed as the porogen. Effects of polymerization conditions on column preparation and chromatographic performance were studied. Enantiomeric separations of D- and L-dansyl phenylalanines were achieved in both OT-LC and OT-CEC modes with good selectivity and efficiencies. Both types of separations may be performed on the same column using a single commercial instrument.

Capillary Action↗
PubMed2003

Fast enantiomeric separation with vancomycin as chiral additive by co-electroosmotic flow capillary electrophoresis: increase of the detection sensitivity by the partial filling technique.

A fast and sensitive method is described by using vancomycin as a chiral additive for enantiomeric separation by capillary electrophoresis (CE). In order to overcome disadvantages associated with use of vancomycin as chiral additive in CE, several strategies including the dynamic coating technique, the co-electroosmotic flow technique, and the partial filling technique were employed sequentially in this method. Using the polycationic polymer hexadimethrine bromide (HDB) as a buffer additive, the capillary wall was dynamically coated with a thin film formed by the adsorbed HDB. Consequently, the adsorption of vancomycin onto the capillary wall was minimized via electrostatic repulsion between the coating of the capillary wall and the vancomycin molecule. In addition, the reversed electroosmotic flow (from cathode to anode) produced by the positively charged capillary wall migrates in the same direction of negatively charged analytes (co-electroosmotic flow electrophoresis). Thereby the electrophoretic mobility of negatively charged analytes were drastically accelerated leading to a short separation time of less than 3.4 min. The separation time was further reduced by the use of a short-end-injection technique. For example, the analysis time was achieved by as short as 55 s for a baseline separation of dansyl-alpha-amino-n-butyric acid. Concurrently, the partial filling technique was used to avoid the loss of detection sensitivity caused by the presence of vancomycin in the running buffer. The effect of several parameters, such as HDB concentration, buffer pH, plug length of the chiral selector, concentration of the chiral selector and applied voltage, on enantioselectivity were investigated toward optimization. Besides the advantage of a very short separation time, the method is characterized by high detection sensitivity, high selectivity, and high efficiency.

Amino Acids↗
PubMed2003

Cyclodextrin-modified monolithic columns for resolving dansyl amino acid enantiomers and positional isomers by capillary electrochromatography.

We describe beta- and gamma-cyclodextrins (beta- and gamma-CD)-modified monolithic columns prepared by sol-gel process and chemical modifications. The monolithic silica column was fabricated inside a fused-silica capillary with 100 microm inner diameter by sol-gel process. The monolithic silica matrix was chemically modified chiral selectors of beta- or gamma-CDs with a spacer of 3-glycidoxypropyltrimethoxysilane by on-column reactions. Gamma-CD-modified monolithic column has successfully been applied for the separation of dansyl amino acid enantiomers. Beta-CD-modified monolithic column has been used for the separation of the positional isomers of o-, m-, and p-cresols and the enantioseparation of racemates of benzoin and several dansyl amino acids by capillary electrochromatography, respectively. For the separation of neutral positional isomers, a positive electric field was applied. However, for the separation of negatively charged analytes, a negative electric field was applied at the inlet of column. The separation efficiency of 5.0 x 10(4) theoretical plates/m for dansyl-L-threonine was obtained at electric field strength of -300 V/cm in the mobile phase of 50 mM 2-(N-morpholino)ethanesulfonic acid (MES)-Tris/methanol (70/30) buffer at pH 7.0. L-enantiomers were eluted as the first peak. Scanning electron micrograph showed that monolithic columns have the morphology of continuous skeleton and large through-pores.

Amino Acids↗
PubMed2004

Subsecond chiral separations on a microchip.

Fast chiral separation of DNS-amino acids could be realized using microchip electrophoresis with fluorescence detection. For this purpose, highly sulfated cyclodextrins (HS-gamma-CD) were used as chiral selectors enabling high selectivity. Even subsecond separation of DNS-tryptophan, DNS-norleucine, DNS-phenylalanine, DNS-methionine, and DNS-aspartic acid could be achieved. Baseline separation could be accomplished within 720 ms, which is the fastest separation of enantiomers reported to date. A more complex mixture consisting of three chiral DNS-amino acids could be separated within 3.3 s utilizing a separation length of only 7 mm and an electrical field strength of 2012 V/cm.

Amino Acids↗
PubMed2005

Synthesis and application of single-isomer 6-mono(alkylimidazolium)-beta-cyclodextrins as chiral selectors in chiral capillary electrophoresis.

Novel single isomers of positively charged beta-CDs were prepared via nucleophilic substitution of 6-monotosyl-beta-CD with alkylimidazoles to afford 6-mono(alkylimidazolium)-beta-CD tosylates and then 6-mono(alkylimidazolium)-beta-CD chlorides by anion exchange. The chiral resolution abilities of these cationic CDs were studied by CE using dansyl (Dns)-amino acids as model analytes. From the experimental results, it was found that both resolution and selectivity of these cationic CDs were dependent on the following parameters: concentration of chiral selectors, pH of the running buffer, counteranions of the CDs, side chain length of the n-alkyl-imidazolium cation, temperature of the capillary column, and organic modifier used. The concentration of chiral selectors required for enantioseparation varied from 3 to 30 mM. The BGE pH played an important role in the resolution of Dns-amino acids. For acidic BGEs, chiral resolution increased with pH (4.0-6.0) and reached a local maximum at pH 6.0. However, better resolutions were obtained with basic phosphate buffer at pH 9.6. Methanol was found to be an effective organic modifier for the resolution of Dns-amino acids by CE.

Amino Acids↗
PubMed2006

Delta-cyclodextrin as novel chiral probe for enantiomeric separation by electromigration methods.

Native delta-CD has been employed as chiral selector in CE and MEKC. To investigate the potential of the enantiodiscriminating properties of delta-CD, negatively charged 5-dimethylamino-1-naphthalene-sulfonyl (dansyl)-, 2,4-dinitrophenyl (DNP)- and FMOC-derivatives of several amino acids, 1,1'-binaphthyl-2,2'-diylhydrogenphosphate, flavanones and three positively charged drugs have been selected as testing samples. Enantioresolution factors up to 4.82 have been observed. The results were compared with those achieved by the conventional running buffer additives alpha-, beta- and gamma-CDs. For several examples a steady increase of enantioresolution with increasing degree of oligomerization has been detected.

Amino Acids↗
PubMed1996

Decreased heterogeneity of CS histone variants after hydrolysis of the ADP-ribose moiety.

Sea urchin CS histone variants are electrophoretically heterogeneous when analyzed in two dimensional polyacrylamide gels (2D-PAGE). Previous results suggested that this heterogeneity is due to the poly (ADP-ribosylation) of these proteins. Consequently, native CS histone variants were subjected to different treatments to remove the ADP-ribose moiety. The incubation in 1 M hydroxylamine was not effective in eliminating the polymers of ADP-ribose from CS variants, and the treatment with sodium hydroxide was deleterious to the proteins. In contrast, the ADP-ribose moiety was successfully removed from the CS variants by incubation with phosphodiesterase (PDE). To eliminate contamination of CS histone variants with PDE extract, the enzyme was covalently bound to Sepharose 4B prior to its utilization. Treatment of native CS histone variants with this immobilized phosphodiesterase removed around 85% of the total ADP-ribose moiety from these proteins. After S-PDE treatment the complex electrophoretic pattern of CS histone variants in 2-D PAGE decreases to five major fractions. From these results we conclude that the electrophoretic heterogeneity of native CS histone variants is mainly due to the extent to which five main CS histone variants are poly(ADP)-ribosylated).

Adenosine Diphosphate Ribose↗
PubMed1990

Purification of tryptase from a human mast cell line.

The neutral protease tryptase has been isolated from a human mast cell line, HMC-1. The HMC-1 line was established from the peripheral blood of a patient with mast cell leukemia and maintained as continuously proliferating clones in vitro and as solid mast cell tumors in nude mice. HMC-1-derived tryptase was purified by sequential chromatography on Dowex 1, DEAE 5 PW, and heparin-agarose. Purified tryptase has an apparent molecular weight of 150,000, as determined by molecular sieve HPLC, but migrates as a doublet of bands of 32/35,000 on SDS-PAGE gels. Maximal enzymatic activity was observed at pH 8.5. Cleavage of tosyl-L-arginine methyl ester by purified tryptase was inhibited by dansyl-L-glutamyl-glycyl-L-arginine chloromethyl ketone 2 HCl, HgCl2, tosyl-L-lysine chloromethyl ketone, leupeptin, and PMSF but not by benzamidine, aprotinin, tosyl-L-phenyl-alanine chloromethyl ketone, soybean trypsin inhibitor, human plasma, ovomucoid inhibitor, or lima bean trypsin inhibitor. Microsequencing of purified tryptase yielded an amino terminal sequence that was identical to that previously reported for human pituitary-derived tryptase.

Amino Acid Chloromethyl Ketones↗
PubMed1986

Double isotopic method using dansyl chloride for the determination of GABA in rat C6 astrocytoma cell cultures.

Methods are described for the quantitative measurement of GABA in culture. The method can be adapted to any amino acid or dansyl-chloride-reactive species. The sensitivity and selectivity of the procedure result from the double isotopic design in which (14C)-labeled internal standard was added to the samples before reaction with (3M)-labeled dansyl chloride. Values obtained by ion-exchange amino acid analysis of cultures agree closely with the values obtained by the double isotopic method. This method is sensitive enough to measure GABA intracellularly and the condition medium.

Animals↗
PubMed1988

The effects of some protein-modifying reagents on the interaction of colicins A, E2, E3, and K with their respective Escherichia coli cell receptors.

Colicins attach themselves--through specific protein-protein interactions--onto receptors in the outer membrane of sensitive bacterial cells. An attempt was made to analyze amino-acid groups and attractive forces involved in this interaction, following treatment of either colicins A, E2, E3 and K or sensitive bacteria with various physico-chemical factors and several protein-modifying reagents. The amounts of colicin bound were checked by a quantitative biological assay. Ionic conditions and specific spatial conformation of both colicin and its receptor molecules are crucial in their interaction and, hence, in the biological effect of colicin. Formaldehyde, naphthalene-diisocyanate and osmium tetroxide strongly inhibit the binding ability of all colicins tested. The results suggest that NH2 and SH groups are involved in their binding onto receptors; also, CH3S groups seem to be engaged in the attachment of colicins E2 and E3 and phenol-OH groups in that of colicin K. The possible involvement of further groups (NH, SH etc.) should be checked using more specific reagents. The attitude of colicins E2 and E3 to their common receptor Btu B protein is nearly, but not completely the same. Receptors for all colicins tested should be oxidized to achieve optimal interactions; obviously, carbonyl groups are produced and newly formed anions increase the negative load of bacterial surface. In agreement, reduction of at least colicins A and E3 enhances their receptor binding reactivity. The binding capacity of each receptor can be modulated by a set of amino acid reagents in a specific manner.

Ammonia↗
PubMed2004

The interaction of human serum albumin with a novel antidiabetic agent--SU-118.

SU-118 is a newly synthesized antidiabetic agent and shows the best hypoglycemic effect among a series of analogs. Its binding properties and binding sites located on human serum albumin (HSA) have been studied using UV absorption and fluorescence spectroscopy. The results of spectroscopic study and the thermodynamic parameters obtained suggest that SU-118 binds to the hydrophobic cavity of human serum albumin and the hydrophobic interaction is the predominant intermolecular force stabilizing the complex. Fluorescent probe displacement studies show that SU-118 can displace competitively both dansylamide and dansylsarcosine from HSA. It is suggested that SU-118 can bind to both site I and site II, but the primary interaction may take place at site I. A binding constant of 1.4 x 10(4) M(-1) and a binding site of 2.0 are obtained from absorbance titration data. The value of binding constant is of the same order of magnitude as that from fluorescence titration. This study provides a molecular basis for elucidating the mechanism of drug acting and predicting unfavorable drug interaction.

Binding Sites↗
PubMed1975

Determination of estrogens in dosage forms by fluorescence using dansyl chloride.

A sensitive, reproducible, fluorometric procedure for the determination of estrogens in pharmaceutical preparations is presented. The estrogens are determined fluorometrically following their reaction with dansyl chloride. The optimum conditions for the reaction such as pH, reaction solvent composition variations, and speed of reaction are discussed. In addition, a linearity study of the relationship between concentration and fluorescence intensity for estrone, estradiol, and ethinyl estradiol is reported. Solvent extraction procedures based on acid-base behavior or column chromatography are used when necessary to isolate the estrogen prior to reaction with dansyl chloride and fluorometric measurement. The recovery of estrogens from spiked samples indicated that the proposed method is efficient and reproducible. Comparison of the dansyl procedure with the official NF method in the analysis of estrone aqueous suspension showed the proposed method to be accurate and more precise than the NF assay. Estrone aqueous suspension, estradiol in sesame oil, estradiol valerate in castor oil and in sesame oil (in the latter case, in the presence of testosterone), estradiol benzoate in sesame oil, and ethinyl estradiol tablets (0.5 mg/tablet) from commercial sources were satisfactorily analyzed, with average results within compendial limits and no coefficient of variation greater than 2%.

Castor Oil↗
PubMed1977

High-pressure liquid chromatographic analysis of drugs in biological fluids II: determination of an antiarrhythmic drug, tocainide, as its dansyl derivative using a fluorescence detector.

A sensitive and specific method is described for the determination of a new primary aliphatic amine antiarrhythmic drug, tocainide. Tocainide, together with an internal standard, is selectively extracted from plasma or blood and reacted with dansyl chloride. The highly fluorescent dansyl derivatives are separated using high-pressure liquid chromatography and measured using a fluorescence detector. The method can measure therapeutic and subtherapeutic concentrations of the drug (0.1-5.0 microng/ml of plasma) with a standard deviation of less than 2%.

Anilides↗
PubMed1977

Polyamine metabolism II: N-(Monoaminoalkyl)- and N-(polyaminoalkyl)acetamides in human urine.

TLC and high-pressure liquid chromatographic examination of the dansyl derivatives obtained from human urine indicated the presence of N-[3-[4-aminobutyl)amino]propyl]acetamide (N1-acetylspermidine), N-[4-](3-aminopropyl)amino]buryl]acetamide (N8-acetylspermidine), N-(4-aminobutyl)acetamide (N-acetylputrescine), and N-(5-aminopentyl)acetamide (N-acetylcadaverine). The ratio of N1- to N8-acetylspermidine ranged from 10.3 in the urine of a patient with hepatoma to 1.1 in the urine of a normal subject. The three cancer patients had a considerably higher ratio of N1- to N8-acetylspermidine than did the three normal subjects. These findings indicate the ratio of N1- to N8-acetylspermidine in the 24-hr urine may serve as a biochemical marker for cancer.

Acetamides↗
PubMed1978

Pharmacokinetics of morphine and its surrogates I: comparisons of sensitive assays of morphine in biological fluids and application to morphine pharmacokinetics in the dog.

A sensitive isotope derivatization assay was developed to quantify morphine in biological fluids in the nanogram per milliliter range. Morphine, derivatized with 3H-dansyl chloride, was separated from the reaction products by TLC. The spots were scraped from the plate, and the eluted radioactivity was determined by liquid scintillation. The standard deviations of this morphine assay were +/- 18.6 ng/ml in 100 microliter of plasma and +/- 1.86 ng/ml in 1 ml of plasma. The GLC analysis of pentafluoropropionated morphine in the range of 0--5 ng of morphine/ml of plasma had a standard deviation of +/- 0.46 ng/ml when 1 ml of plasma was taken. Liquid scintillation spectrometric analysis of 14C-morphine had a sensitivity of 1.5 ng/ml of plasma at double the background. There were no significant differences among the liquid scintillation, electron-capture GLC, and radioisotpoe derivatization methods for morphine obtained from the plasma of a dog given 14.00 mg iv of morphine. Morphine conjugates were assayed as morphine after the acid hydrolysis of plasma and urine preextracted to remove unconjugated morphine, and the equivalence of various methods was demonstrated to monitor plasma and urine pharmacokinetics in a dog.

Animals↗
PubMed1978

High-pressure liquid chromatographic analysis of estrogens in pharmaceuticals by measurement of their dansyl derivatives.

A high-pressure liquid chromatographic method is described for the analysis of estrogens in pharmaceutical tablet and injectable dosage forms. In general, the estrogens are isolated, an internal standard is added, the dansyl derivatives are formed, and the dansyl estrogen solution is injected into a liquid chromatograph. Linear response is experienced between the mass of estrogen and the ratio of the estrogen peak height to the internal standard peak height, using a microparticle silica column and chloroform--n-heptane mobile phases. With fluorometric measurement, limits of detectability for ethinyl estradiol and estradiol were 0.04 and 0.05 ng, respectively. Methyltestosterone, an androgen in combination with ethinyl estradiol, was analyzed simultaneously. Commercial pharmaceutical preparations containing estrone, ethinyl estradiol, and estradiol were analyzed by the proposed method. The results indicate the method to be sensitive, reasonably precise (less than 2%), and accurate in the analysis of estrogen in dosage forms.

Chromatography, High Pressure Liquid↗