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Biomedical subjects

B L Karger

Publications and source records attributed to B L Karger.

At least 55 records · Page 3Linked to original sources
PubMed1996

Quantitative competitive polymerase chain reaction: analysis of amplified products of the HIV-1 gag gene by capillary electrophoresis with laser-induced fluorescence detection.

A quantitative competitive polymerase chain reaction (PCR) assay for the detection and quantification of HIV-1 has been developed using capillary electrophoresis. Separation of the PCR products is carried out in coated capillaries filled with replaceable linear polyacrylamide, and detection is performed using laser-induced fluorescence. The quantitative capabilities of this assay are described. We show results from analysis of a noninfectious plasmid encoding the HIV genome and integrated proviral DNA. Potential applications of this assay are discussed.

Cell Line↗
PubMed1996

Liquid chromatographic and capillary electrophoretic examination of intact and degraded fusion protein CTLA4Ig and kinetics of conformational transition.

Methods have been developed for the CE and HPLC analysis of CTLA4Ig, an immunoglobulin fusion protein. Two different LC approaches, size-exclusion (SEC) and "mixed-mode" ion-exchange (ABx), were developed along with a CE method that uses a micellar electrokinetic chromatographic buffer consisting of borate ions, sodium dodecyl sulfate and acetonitrile. These assays measure the presence of several CTLA4Ig-related species, and the observed changes resulting from multiple modes of degradation. In an attempt to identify possible degradation products, collections were taken from the ABx and SEC liquid chromatographic systems and further analyzed by matrix-assisted laser desorption time-of-flight (MALDI TOF) mass spectrometry. Multiple species were detected covering a wide molecular mass range. In addition, the CE method was used to study conformational kinetics between two forms of CTLA4Ig and to estimate the activation energy of the conformer-conformer transition. Pseudo-first-order reaction kinetics were demonstrated for CTLA4Ig samples stressed with papain, H2O2, and sodium dodecyl sulfate/heat.

Abatacept↗
PubMed1996

Electrospray interface for capillary electrophoresis-mass spectrometry with fiber-optic UV detection close to the electrospray tip.

A miniaturized, integrated capillary electrophoresis-ultraviolet detection-electrospray ionization-mass spectrometry (CE-UV-ESI-MS) interface has been constructed and evaluated. The device incorporates a fiber optic detection cell close to the electrospray tip to allow UV monitoring of separated zones just prior to their admittance into the mass spectrometer. This configuration provides precise information about the time when UV-active zones enter the electrospray and allows easy location of analyte mass information in the ion current profile. The miniaturized dimensions of the interface allow the use of short capillaries for fast separations.

Amino Acid Sequence↗
PubMed1996

The use of elevated column temperature to extend DNA sequencing read lengths in capillary electrophoresis with replaceable polymer matrices.

Capillary electrophoresis with a replaceable linear polyacrylamide matrix operated at elevated column temperatures of 55 degrees and 60 degrees C was used to extend the separation of DNA sequencing fragments to lengths greater than 800 bases. A solid-state heater was employed to provide stable, uniform temperature control over a significant portion of the capillary. The polymer matrix, 3% w/v linear polyacrylamide in a denaturing buffer, was replaced in the capillary after each run. Using dye-labeled primers and Sequenase chemistry on an M13mp18 single-stranded template, four-color separations for the sequencing products were obtained, with read lengths in excess of 800 bases. This paper also briefly discusses the effects of buffer denaturants and capillary temperature on separation speed, resolution, and gel compression.

Acrylic Resins↗
PubMed1996

Fast capillary electrophoresis-laser induced fluorescence analysis of ligase chain reaction products: human mitochondrial DNA point mutations causing Leber's hereditary optic neuropathy.

High speed capillary electrophoresis-laser-induced fluorescence (CE-LIF) has been used to separate and detect point mutations using the ligase chain reaction (LCR). The method utilizes short capillary columns (7.5 cm effective length) and fields of 400 V/cm to analyze DNA-ethidium bromide complexes using an He/Ne laser. The method was first demonstrated with a commercially available kit for LCR based on a lacI gene fragment inserted in a Bluescript II phagemid. LCR-CE-LIF was then applied to detect point mutations in human mitochondrial DNA, resulting in Leber's hereditary optic neuropathy (LHON). Three severe mutations were analyzed in which the original base is substituted by a thymidine base at positions 3460, 11778 and 14459. Appropriate primers were designed with polyT tails for length discrimination of pooled samples. Successful detection of mutated samples was achieved, with appropriate correction for small amounts of nonspecific ligated product. The method is rapid, easy to implement, and automatable.

Base Sequence↗
PubMed1996

Sequence and transcription of Qa-2-encoding genes in mouse lymphocytes and blastocysts.

The protein product of the mouse preimplantation embryo development (Ped) gene, which controls the rate of preimplantation embryonic cleavage division and subsequent embryo survival, is the Qa-2 antigen. This major histocompatibility complex (MHC) class I b protein is encoded by four genes, Q6, Q7, Q8, and Q9. The present study was undertaken to begin to elucidate which of the four Qa-2-encoding genes are responsible for the Ped gene phenotype in the C57BL/6 mouse (H2(b)). First, restriction maps of the four genes, using 25 restriction enzymes, were created. The RE maps confirmed that Q6 is similar to Q8 and Q7 is similar to Q9, but that the Q6/Q8 gene pair differs from the Q7/Q9 gene pair. The genomic DNA sequences of Q6 and Q8 were determined, as well as the DNA sequences of exons 4 - 8 of Q9, and the 5' regulatory regions of Q6, Q8, and Q9. This DNA sequence information, combined with the published DNA sequence information for the entire Q7 gene and exons 1 - 3 of Q9, allowed us to design primers for reverse transcription-polymerase chain reaction that could distinguish which of the four genes were transcribed in mouse lymphocytes and embryos. It was found that all four genes are transcribed in lymphocytes, but only Q7 and Q9 are transcribed in mouse embryos. Thus, both Q7 and Q9 are candidates for the genes responsible for the Ped gene phenotype.

Amino Acid Sequence↗
PubMed1996

Nonradioactive monitoring of organic and inorganic solute transport into single Xenopus oocytes by capillary zone electrophoresis.

Transport of organic and inorganic solutes into and out of cells requires specialized transport proteins. Given a sufficiently sensitive analytical method for measuring cellular solute concentrations, it should be possible to monitor solute transport across the plasma membrane at the level of single cells. We report a capillary zone electrophoresis approach that is generally applicable to monitor solute transport into Xenopus laevis oocytes, requires only nanoliters of sample, and involves no radioactive materials. The sensitivity of capillary electrophoresis with UV detection is typically on the order of 10(-5)-10(-6) M, resulting in the mass detection limits in the low femtomole range. We show that capillary zone electrophoresis serves as a simple technique to measure solute transport into oocytes. Studies of the mammalian oligopeptide transporter PepT1 and the Na(+)- and K(+)-coupled epithelial and neuronal glutamate transporter EAAC1 expressed in oocytes demonstrate that transport of the dipeptide Trp-Gly via PepT1 and transport of Na+ and K+ via EAAC1 across the oocyte plasma membrane can be monitored by measuring intracellular tryptophan absorption and by indirect UV detection of inorganic ions, respectively. The CZE method allowed the simultaneous detection of changes of intracellular Na+ and K+ concentrations in response to EAAC1-mediated Na+ cotransport and K+ countertransport. This is the first report of a capillary zone electrophoresis-based quantitative analysis of intracellular components of a single cell in response to transport activity.

Amino Acid Transport System X-AG↗
PubMed1996

DNA sequencing by capillary electrophoresis using short oligonucleotide primer libraries.

Two strategies for DNA sequencing by primer walking using short oligonucleotide primer libraries have been successfully employed along with capillary electrophoresis using replaceable polymer solutions of linear polyacrylamide and fluorescence detection. A 3.5-kb stretch of the single-stranded M13mp18 template was sequenced with T7 PRISM dye-terminator/Sequenase chemistry. An in-house base-calling program offered read lengths of roughly 450 bases with an average of 97.8% accuracy.

Base Sequence↗
PubMed1995

Analysis of protein fractions by micropreparative capillary isoelectric focusing and matrix-assisted laser desorption time-of-flight mass spectrometry.

In this study, the use of capillary isoelectric focusing (cIEF) as a micropreparative tool for protein analysis by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrated. A newly designed, automated, collection interface equipped with a fiber-optic UV detector and a sheath flow connection was employed for collection of protein fractions. Multiple fractions were collected during a single cIEF run and further analyzed by MALDI-TOF-MS for mass assignment. The feasibility of the method was tested with a mixture of model proteins with different isoelectric points and molecular masses, and with variants of human hemoglobins differing in pI, but with negligible difference in M(r). Some practical considerations of the collection procedure and subsequent TOF analysis are presented.

Autoanalysis↗
PubMed1995

Design of a high-precision fraction collector for capillary electrophoresis.

A high-precision fraction collector for capillary electrophoresis has been developed. The device utilizes detection close to the end of the capillary and a sheath liquid at the exit of the capillary, allowing continuous collection (i.e., uninterrupted applied electrical field) of multiple species. The role of the sheath liquid flow rate and position of detection in the column on the collection precision was assessed. Fiber-optic detection at approximately 1 cm before the exit end of the capillary was found effective for precise timing of the collection. Up to 60 fractions of microliter or smaller volumes could be automatically collected into capillaries used as collection vials. The collection capillaries were placed on a cylinder, and a computer-controlled stepping motor aligned the appropriate capillary with the column exit. The effectiveness of the fraction collector was demonstrated in the collection of all 11 fragments of the HaeIII restriction digest of phi X-174 plasmid DNA. Polymerase chain reaction amplification of the 271 and 281 bp fragments revealed an inversion of the size-dependent migration order.

Bacteriophage phi X 174↗
PubMed1995

Single strand conformational polymorphism using capillary electrophoresis with two-dye laser-induced fluorescence detection.

Capillary electrophoresis (CE), using a replaceable polymer matrix and two-dye laser-induced fluorescence has been applied to single strand conformational polymorphism (SSCP). Two-dye laser-induced fluorescence has been used for improved strand identification over a single-dye approach. Conditions suitable in the capillary format for rapid separation and high resolution have been explored. The influence of separation parameters such as temperature and matrix composition on separation in SSCP was first determined. Short analysis times allowed for fast screening of optimal separation conditions of the sample. Based on these results, the two strands of a standard 255 bp fragment of the lacI gene were resolved within 25 min with replaceable linear polyacrylamide as a separation matrix. The method was then applied to the detection of different mutations, in the presence of wild type, of a 276 bp fragment of the insulin-like growth factor 1-binding protein 1 (IGF1-BP3) gene.

Amino Acid Sequence↗
PubMed1995

Sequence dependent migration behavior of double-stranded DNA in capillary electrophoresis.

Capillary electrophoresis (CE) with a replaceable linear polyacrylamide (LPA) sieving matrix was used to examine sequence-dependent migration of double-stranded DNA fragments. It has been found that DNA conformational effects were significant under high electric field separations, especially using high resolution matrices. Compared to linear DNA-ladder standards, both anomalously slow and rapid DNA fragments were observed, with the degree of anomalous migration depending on the electric field strength, polymer concentration, column temperature, and background electrolyte (denaturants, sodium and magnesium ions, DNA-intercalating dyes). By selecting a combination of electrophoretic conditions (e.g. 3% T LPA, elevated capillary temperature, lower electric field strength and addition of DNA intercalating dyes), molecular weight dependent separations were closely restored.

Bacteriophage phi X 174↗
PubMed1995

Capillary electrophoresis of proteins and nucleic acids.

During the past 30 years, slab gel electrophoresis has been one of the most important tools available to modern biochemistry, biology, and clinical research. However, despite substantial progress in methodology, slab gel techniques typically suffer from laborious, time-consuming and difficult-to-automate procedures. Capillary electrophoresis (CE), first introduced a decade ago, emerges now as an alternative to slab gel techniques with all the advantages of modern automated technology. Although the first target of CE was analysis of small molecules (it is a highly efficient alternative to HPLC), now a main focus is on biopolymers. Currently, CE can be viewed as a fully automated tool for rapid, highly sensitive, and quantitative analysis of minute (nanoliter) amounts of complex samples. This chapter reviews the most important CE techniques and their use for the analysis and characterization of proteins and DNA.

DNA, Single-Stranded↗
PubMed1994

Conformational changes in the reversed phase liquid chromatography of recombinant human growth hormone as a function of organic solvent: the molten globule state.

As a continuation of a previous paper on the retention behavior of recombinant human growth hormone (rhGH) in reversed phase chromatography at pH 6.5 (Oroszlan, P., et al. Anal. Chem. 1992, 64, 1623-1631) the effect of 1-propanol (1-PrOH) and acetonitrile on the conformation of rhGH at this pH has been investigated by circular dichroism (CD), second-derivative UV spectroscopy, fluorescence anisotropy, fluorescence quenching, and fluorescence lifetime measurements. Addition of 1-PrOH up to a concentration of 10% (v/v) does not cause any significant changes in protein structure. However, above this concentration, a transition from the native to a new state is observed; the transition is completed above 30% (v/v) of 1-PrOH, the composition for completion being dependent on temperature. This change in structure correlates with retention changes observed in reversed phase chromatography. The new rhGH conformation retains much of the alpha-helicity and possesses a slightly expanded hydrodynamic radius relative to native rhGH. Second-derivative UV spectroscopy suggests that the hydrogen bond between Trp 86 and Asp 169, spanning two alpha-helices, remains intact. On the other hand, the near-UV CD intensity changes from positive to negative in the Trp region of the spectrum, signaling an alteration in the Trp environment. In addition, fluorescence quenching measurements with trichloroethanol reveal greater accessibility to solvent of the Trp residue after the conformational transition has occurred. From the results, it is concluded that a molten globule state (compact state retaining much of the secondary structure of the native state but with a disrupted tertiary structure) is produced with the addition of > 30% (v/v) 1-PrOH.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗
PubMed1994

Use of zwitterionic detergents for the separation of closely related peptides by capillary electrophoresis.

Capillary electrophoresis incorporating hydrophobic selectivity is shown to be a powerful technique for separating closely related peptide species. In this work, hydrophobic interaction was induced through the addition of suitable amounts of a zwitterionic detergent (N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and further modified with organic solvents. A neutral, hydrophilic-coated capillary was used to minimize electroosmotic flow. Two test solutes, Met15- and Leu15-gastrin, were employed to probe hydrophobic selectivity with various electrophoretic conditions. The nature and concentration of the detergent and the organic modifier were varied to adjust the selectivity. Operation near the critical micelle concentration of the zwitterionic detergent in the presence of acetonitrile or various alcohols produced the highest hydrophobic selectivity among the conditions studied. The zwitterionic detergent approach was also briefly compared to the use of non-ionic detergents for hydrophobic selectivity.

Amino Acid Sequence↗
PubMed1994

Incorporation of hydrophobic selectivity in capillary electrophoresis: analysis of recombinant insulin-like growth factor I variants.

A highly selective electrophoretic system employing differential hydrophobic interaction was evaluated for the quantitative determination of recombinant insulin-like growth factor I (IGF-I) variants. The system consisted of mixed aqueous-organic buffers containing suitable amounts of a zwitterionic detergent. In addition, a neutral hydrophilic coating was attached to the wall of the capillary to minimize analyte adsorption and electroosmotic flow. The zwitterionic detergent acted as a hydrophobic selector, allowing independent optimization of the electrophoretic and hydrophobic selectivities in the separation system. The extent of hydrophobic interaction was conveniently adjusted by varying the type and amount of organic modifier. Complete resolution of a mixture of IGF-I variants with closely related mass-to-charge ratios was achieved. Quantitative analysis of IGF-I process samples agreed well with HPLC results. Finally, the approach was found to be compatible with on-line capillary electrophoresis-mass spectrometry.

Amino Acid Sequence↗