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R A Evangelista

Publications and source records attributed to R A Evangelista.

At least 19 recordsLinked to original sources
PubMed2001

Characterization of highly sulfated cyclodextrins.

A class of highly sulfated cyclodextrins (HS-CDs) was developed for enantiomeric separation of chiral compounds by capillary electrophoresis (CE). The HS-CDs were produced by a facile single-step direct sulfation of cyclodextrin using sulfur trioxide-trimethylamine complex in dimethylformamide. Characterization of the HS-CDs by electrospray ionization mass spectrometry and by CE using a well-established indirect detection method indicated the species have very narrow heterogeneity in terms of degree of sulfation. Elemental analysis of the HS-alpha-, beta- and gamma-CDs showed that the average sulfate contents were 11, 12, and 13 per CD molecule, respectively. The 13C NMR of HS-CDs is consistent with the structural assignment of nearly complete sulfation at C-6 primary hydroxyl groups and partial sulfation at the C-2 secondary hydroxyls (>70%), while the C-3 hydroxyls remain unsubstituted. Enantiomeric separation by CE using the HS-CDs as chiral selectors showed that HS-alpha-, beta- and gamma-CDs complement each other by exhibiting different chiral selectivities, resulting in resolution of many chiral neutral, acidic and basic compounds of greatly varying structural features. The part of HS-CD that interacts with the guest molecule during complexation and, therefore, the receiving end of the cyclodextrin hydrophobic bucket was surrounded with largely regiospecifically substituted C-2 sulfates and intact C-3 hydroxyls, both at the equatorial positions. Such global regiospecific structural arrangement in HS-CDs provides differential diasteroisomeric complexation is proposed to be the principal contributing factor in the resolving racemates.

Cyclodextrins↗
PubMed1998

Profiling glycoprotein n-linked oligosaccharide by capillary electrophoresis.

A method for analysis of N-linked oligosaccharides derived from glycoproteins including sialic acid-containing species is presented. It is based on the combination of specific chemical and enzymatic conversions coupled with capillary electrophoretic (CE) separation and laser-induced fluorescence (LIF) detection. Glycoproteins were heat-denatured in the presence of a reducing agent and the N-linked oligosaccharides were released by peptide N-glycosidase (PNGase F; EC3.5.1.52)-catalyzed hydrolysis. The released N-linked oligosaccharides were derivatized with 8-aminopyrene-1,3,6-trisulfonate (APTS) under mild reductive amination conditions in which desialylation and loss of fucose residues are minimized. A model N-linked oligosaccharide, desialylated, galactosylated biantennary, core-substituted with fucose (A2F) was tested for APTS-based derivatization chemistry with excellent recovery of the adduct without losing fucose and neuraminic acid residues. The profiles of heavily sialylated N-linked oligosaccharides derived from fetuin, recombinant human erythropoietin and kallikrein are reported and the data show that the present method produces a high resolution of the N-linked oligosaccharide profile for fingerprinting glycans derived from glycoproteins.

Amidohydrolases↗
PubMed1998

Quantitative analysis of sugar constituents of glycoproteins by capillary electrophoresis.

A method for quantitative analysis of monosaccharides including N-acetylneuraminic acid derived from sialic acid-containing oligosaccharides and glycoproteins is presented. The analysis is based on the combination of chemical and enzymatic methods coupled with capillary electrophoretic (CE) separation and laser-induced fluorescence (LIF) detection. The present method utilizes a simplified acid hydrolysis procedure consisting of mild hydrolysis (0.1 M TFA) to release sialic acid and strong acid hydrolysis (2.0 N TFA) to produce amino and neutral sugars. Amino sugars released from strong acid hydrolysis of oligosaccharides and glycoproteins were reacetylated and derivatized with 8-aminopyrene-1,3,6-trisulfonate (APTS) along with neutral sugars in the presence of sodium cyanoborohydride to yield quantitatively the highly stable fluorescent APTS adducts. N-acetylneuraminic acid (Neu5Ac), a major component of most mammalian glycoproteins, was converted in a fast specific reaction by the action of neuraminic acid aldolase (N-acylneuraminate pyruvate-lyase EC 4.1.3.3) to N-acetylmannosamine (ManNAc) and pyruvate. ManNAc was then derivatized with APTS in the same manner as the other monosaccharides. This method was demonstrated for the quantitation of pure Neu5Ac and the species derived from mild acid hydrolysis of 6'-sialyl-N-acetyllactosamine and bovine fetuin glycan. Quantitative recovery of the N-acetylmannosamine was obtained from a known amount of Neu5Ac in a mixture of seven other monosaccharides or from the sialylated oligosaccharides occurring in glycoproteins. The sequence of procedures consists of acid hydrolysis, enzymatic conversion and APTS derivatization which produced quantitative recovery of APTS-monosaccharide adducts. The detection limits for sugars derivatized with APTS and detected by CE-LIF are 100 pmol for Neu5Ac and 50 pmol for the other sugars.

Amino Sugars↗
PubMed1996

Characterization of fluorescent nucleoside triphosphates by capillary electrophoresis with laser-induced fluorescence detection: action of alkaline phosphatase and DNA polymerase.

A method of analysis of fluor-labeled nucleoside triphosphates based on alkaline phosphatase-catalyzed sequential cleavage of phosphate groups with monitoring of all fluorescent species by capillary electrophoresis with laser-induced fluorescence detection is presented. The method allows determination of the purity of the triphosphate samples as well as the relative amounts of the lower phosphate contaminants. The ability of one of the fluor-labeled nucleoside triphosphates to serve as polymerase substrate was verified by labeling DNA restriction fragments by the method of filling recessed 3'-ends using DNA polymerase Klenow fragment.

Adenosine Triphosphate↗
PubMed1996

High-resolution capillary gel electrophoresis of reducing oligosaccharides labeled with 1-aminopyrene-3,6,8-trisulfonate.

High-resolution capillary gel electrophoresis was used for the separation of oligosaccharides labeled with a novel fluorophore 1-aminopyrene-3,6,8-trisulfonate (APTS) at the reducing termini by reductive amination. The APTS-saccharide adducts were detected by laser-induced fluorescence with excitation by the 488-nm Ar-ion laser and a 520-nm emission filter. The stoichiometry of labeling is such that only one molecule of fluorophore is attached to each molecule of oligosaccharide. Derivatization parameters, such as labeling reagent concentration, labeling temperature, and time as well as the influence of reaction solvent are thoroughly discussed. Desialylation of several sialylated oligosaccharides with different structures and linkages due to the effects of labeling temperature and time are also addressed. Employing the optimized conditions suggested in this paper, fluorophore labeling efficiency greater than 97% was achieved with no significant loss of sialic acid residues. The fluorescently labeled oligosaccharides are then separated and quantified by capillary gel electrophoresis. Practical examples of low-level derivatization and high-resolution capillary gel electrophoresis separation of N-linked glycans of ribonuclease-B and fetuin are also shown.

Acetylglucosamine↗
PubMed1996

Acid-catalyzed reductive amination of aldoses with 8-aminopyrene-1,3,6-trisulfonate.

The reductive amination of monosaccharides with 8-aminopyrene-1,3,6-trisulfonate (APTS) in seven different organic acids including the commonly used acetic acid was investigated by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. The correlation between the yields of the saccharide-APTS adducts and pKa of the organic acid catalyst is consistent with general acid catalysis of the rate-determining step of the reductive amination reaction. Derivatization in the presence of organic acids of higher strength than acetic acid produced substantially higher yields of APTS-sugar adducts, an effect which is more pronounced for N-acetylamino sugars. Optimum yields were obtained using citric acid as a catalyst. Conversion of a few nanomoles of neutral saccharides to the APTS derivatives is achieved at 75 degrees C in less than 60 min.

Acids↗
PubMed1996

Separation of 1-aminopyrene-3,6,8-trisulfonate-labeled asparagine-linked fetuin glycans by capillary gel electrophoresis.

Asparagine-linked glycans of bovine fetuin were separated by capillary gel electrophoresis after enzymatic release (peptide-N-glycosidase F) and labeling via reductive amination by a fluorescent dye, 1-aminopyrene-3,6-8-trisulfonate (APTS). At low separation pH (2.5) only two dominant peaks were observed. Increasing the separation buffer pH to 4.75 resulted in complete separation of two primary doublets and several minor peaks from the fetuin N-linked glycan pool. Two of the four major peaks were spiked with purified individual standards and were identified as trisialylated triantennary structures with different sialylation linkages. The other two larger peaks were postulated to be tetrasialylated triantennary structures, based on calculations considering their corresponding glucose unit (GU) values. Effects of the electrophoretic separation parameters, such as gel concentration, electric field strength and temperature on the migration behavior of the two major doublets of the fetuin glycan pool were also thoroughly examined. Our data suggest that the capillary gel electrophoresis separation of the multisialylated branched oligosaccharides with different linkage isomers, released from bovine fetuin, is fundamentally based on their degree of sialylation and hydrodynamic volumes.

Asparagine↗
PubMed1995

Analysis of mono- and oligosaccharide isomers derivatized with 9-aminopyrene-1,4,6-trisulfonate by capillary electrophoresis with laser-induced fluorescence.

A method of analysis of isomers of mono- and oligosaccharides derivatized with 9-aminopyrene-1,4,6-trisulfonate (APTS) by capillary electrophoresis (CE) in simple buffer systems is presented. The derivatization chemistry is performed at 75 degrees C for 1 h for most mono- and oligosaccharides. Sialyllactose was derivatized at 37 degrees C for 15 h without significant desialylation. Most of the APTS derivatized isomers of mono- and oligosaccharides are resolved in buffers such as acetate (pH 5.0), 3-(N-morpholino)-propanesulfonic acid (pH 7.0), and phosphate (pH 7.4). The mechanism of CE separation using the above buffers is based on the differences in hydrodynamic volume of the derivatized species and is different from that in borate or high pH buffer.

Electrophoresis, Capillary↗
PubMed1995

Detection of amplified Y chromosome-specific sequence by capillary electrophoresis with laser-induced fluorescence.

OBJECTIVE: To develop a sensitive method for genetic diagnosis using capillary electrophoresis with laser-induced fluorescence. DESIGN: Using male DNA diluted with female DNA as an example, ZFY gene from Y chromosome was amplified specifically by polymerase chain reaction (PCR) with fluorescence-labeled primers and detected by capillary electrophoresis with laser-induced fluorescence. SETTING: Laser operating laboratory. PARTICIPANTS: Human male and female DNA were extracted from healthy human male and female subjects. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The concentration of human DNA was determined by using a spectrophotometer at an absorbance of 260 nm. RESULT: Deoxyribonucleic acid fragments amplified from a single copy of ZFY gene were detected by capillary electrophoresis with laser-induced fluorescence after 35 cycles of PCR amplification. CONCLUSION: This method is potentially applicable for rapid and sensitive detection of fetal Y chromosome DNA sequence in maternal circulation and of single-cell DNA diagnosis.

Base Sequence↗
PubMed1995

Double-stranded DNA analysis by capillary electrophoresis with laser-induced fluorescence using ethidium bromide as an intercalator.

We have developed a rapid and sensitive method to analyze double-stranded DNA by capillary electrophoresis equipped with a laser-induced fluorescence detector. Using ethidium bromide as an intercalator in polyacrylamide gel-filled capillaries along with a green He/Ne laser source (excitation: 543 nm; emission: 600 nm), we found the detection sensitivity for a single DNA-ethidium bromide complex was in the picogram level with a resolution of one base pair separation between two DNA fragments. In the case of the separation of a phi X174 DNA-HaeIII digest, sizes from 72 to 1353 bp were well resolved within 12 min. For the analysis of PCR-amplified DNA, low levels of amplified DNA fragments could be detected that could not be visualized in agarose gel after standard ethidium bromide staining. Considering the high resolving power and sensitivity, we believe that this method can be a useful tool for the analysis of double-stranded DNA especially for PCR-amplified DNA fragments.

Base Sequence↗
PubMed1994

Analysis of structural specificity in antibody-antigen reactions by capillary electrophoresis with laser-induced fluorescence detection.

A rapid and simple procedure for screening antibodies for binding to an antigen is proposed. A fluorescent hapten-dye conjugate was prepared by labeling the amino moiety of the hapten with a commercially available reactive cyanine dye, Cy5 (excitation maximum: 650 nm, emission maximum: 670 nm). A fixed amount of the Cy5-hapten was titrated with serial dilution of the antibody. Each of the titration mixture was analyzed by capillary electrophoresis (25 cm x 20 microns column) monitored by laser-induced fluorescence (laser: 10 mW helium-neon, 632.8 nm). Free and antibody-bound Cy5-hapten were analyzed simultaneously on the electropherogram. Competitive immunoassay of hapten was demonstrated with low-end sensitivity of 5.10(-8) M, about 10x more sensitive than the present drug screening methods. Using morphine as an example, the screening of various antibodies (from different vendors) and cross-reactivity of morphine analogues using the present procedure will be discussed.

Antibodies↗
PubMed1994

Feasibility studies for simultaneous immunochemical multianalyte drug assay by capillary electrophoresis with laser-induced fluorescence.

We present a method for the simultaneous quantification of multiple drug analytes in urine, based on combining immunochemical binding with capillary electrophoretic separation. Two fluorescent drug-cyanine (Cy) dye conjugates were prepared as competing species for the immunoassay. Morphine was derivatized with Cy5 (lambda max = 652 nm, epsilon = 215,000 mol-1cm-1 L), phencyclidine (PCP) with Cy5.5 (lambda max = 675 nm, epsilon = 200,000 mol-1cm-1L). The high-efficiency resolving power of the capillary electrophoresis system (20 microns x 27 cm column) separated the individual labeled drugs, and the antigen-antibody complexes were detected by laser-induced fluorescence (laser: 10 mW He-Ne at 632.8 nm) with Cy5 diacid as internal standard. Simultaneous competitive immunoassay of morphine and PCP in urine showed that the free labeled-drug peak areas were proportional to the concentrations of the drug species present in the urine sample. This immunoassay can be performed routinely and reproducibly in < 5 min with analytical detection limits of 4 nmol/L for PCP and 40 nmol/L for morphine.

Antigen-Antibody Reactions↗
PubMed1992

Alkyl- and aryl-substituted salicyl phosphates as detection reagents in enzyme-amplified fluorescence DNA hybridization assays on solid support.

Nine salicyl phosphate esters with hydrophobic substituents (5-phenyl, 5-(2,4-difluorophenyl), 5-tert-octyl, 5-cumyl, 5-(4-tert-butylphenyl, 5-(1-adamantyl), 5-(n-dodecyl), 5-(1,1-diphenylethyl, and 5-trityl) were synthesized and found to be good substrates for calf intestinal alkaline phosphatase. The enzymatic hydrolysis produced the corresponding salicylates, which were strongly fluorescent when excited by ultraviolet light around 300 nm with maximum emission at 420-435 nm. The salicylates were less soluble and/or more adhesive than the nonfluorescent salicyl phosphate substrates, resulting in localization of fluorescence signal, which is a requirement for membrane-based assays. The salicyl phosphates bearing 8-14 carbon substitutents were found to be suitable detection reagents for dot-blot DNA hybridization assays on nylon membrane using a biotinylated probe, allowing the detection of 125 pg of target pBR322 plasmid DNA using a simple apparatus consisting of a transilluminator, a camera. and a 455-nm cutoff optical filter.

Alkaline Phosphatase↗
PubMed1991

Enzyme-amplified lanthanide luminescence for enzyme detection in bioanalytical assays.

Enzyme-amplified lanthanide luminescence (EALL) is a new method which has been developed for enzymatically amplified signal detection in ultrasensitive bioanalytical assays where an enzyme is used as label or is itself the analyte of interest. Signal generation is performed by enzymatically transforming a substrate into a product which forms a luminescent lanthanide chelate; the product chelate can then be detected using time-resolved or normal fluorescence methods. Alkaline phosphatase substrates have been developed and demonstrated in a model immunoassay in microwell format. The method has also been demonstrated for detection of a variety of other hydrolytic and oxidative enzymes. Thus the EALL method shows promise for use in a wide variety of bioanalytical applications.

Alkaline Phosphatase↗
PubMed1991

Time-resolved fluorescence detection of enzyme-amplified lanthanide luminescence for nucleic acid hybridization assays.

A new nonisotopic detection method based on time-resolved fluorescence for nucleic acid hybridization assays with alkaline phosphatase labels has been developed: enzyme-amplified lanthanide luminescence (EALL). EALL combines the amplification of an enzyme label with the sensitivity and background elimination of time-resolved fluorescence detection of lanthanide ion luminescence. The detection system for alkaline phosphatase makes use of a phosphorylated salicylic acid derivative that, upon dephosphorylation, gives a product capable of forming a luminescent terbium chelate. We demonstrate DNA hybridization assays by using two substrates, one for membrane and one for solution-based formats. Using the substrate that produces a more adhesive product allows performance of dot-blot and Southern blot assays on nylon membranes; results can be recorded with a time-resolved photographic camera system, or with an ultraviolet transilluminator-based system. Less than 4 pg of target sequence can be detected in a dot-blot assay after incubation with substrate for 2-4 h. DNA microwell-plate hybridization assays with the more soluble substrate/product pair can be quantified with time-resolved fluorescence plate readers, giving a similar detection sensitivity. EALL is thus a practical time-resolved fluorescence-based alternative to other detection systems for DNA hybridization assays.

Alkaline Phosphatase↗
PubMed1988

A new europium chelate for protein labelling and time-resolved fluorometric applications.

Synthetic procedures are presented for a new chelator that forms stable and highly fluorescent complexes with Eu3+. This chelator, 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA) is synthesized in a high-yield three-step procedure. BCPDA can be covalently incorporated into proteins under relatively mild conditions, and when complexed with Eu3+ forms a fluorescent product that has a lifetime in the range of 0.4 to 0.7 ms. Thus, it is useful for time-resolved fluorescence immunoassay applications.

Animals↗