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At least 469 records · Page 26Linked to original sources
PubMed1991

Application of capillary zone electrophoresis to the characterization of multiple antigen peptides.

Capillary zone electrophoresis (CZE) was applied to the analysis of a recently described class of synthetic branched peptides, multiple antigen peptides (MAPs). In comparison with high-performance liquid chromatography (HPLC), CZE showed superior resolution of minor impurities in samples of MAPs obtained by preparative chromatography. MAPs that differed only in the substitution of uncharged residues (Ala-Ser) could be separated by the addition of organic solvents (acetonitrile, methanol, ethanol) to the aqueous background electrolyte.

Amino Acid Sequence↗
PubMed1991

Capillary electrophoresis-atmospheric pressure ionization mass spectrometry for the characterization of peptides. Instrumental considerations for mass spectrometric detection.

On-line capillary electrophoresis (CE) separations are shown for a synthetic peptide mixture and a tryptic digest of human hemoglobin in an uncoated fused-silica capillary with detection using atmospheric pressure ionization mass spectrometry (API-MS). The CE system utilized a 1-m capillary column of either 75- or 100-microns I.D. These somewhat larger inside diameters allow higher sample capacities for MS detection and the 1-m length facilitates connecting the CE column to the liquid junction-ion spray interface and MS system. Low volatile buffer concentrations (15-20 mM) of ammonium acetate or ammonium formate, and high organic modifier content (5-50%) of methanol or acetonitrile facilitates ionization under electrospray conditions. This study shows that peptides separated by CE may be transferred to the API-MS system through a liquid junction coupling to the pneumatically assisted electrospray (ion spray) interface at low buffer pH when the electroosmotic flow is low (0-0.04 microliter/min). CE-MS as described herein is facilitated by features in modern CE instrumentation including robotic cleaning and pressurization of the capillary inlet. The latter is particularly useful for repetitive rinsing and conditioning of the capillary column between analyses in addition to continuous 'infusion' of sample to the mass spectrometer for tuning purposes. In addition to facile molecular weight determination, amino acid sequence information for peptides may be obtained by utilizing on-line tandem MS. After the tryptic digest sample components enter the API-MS system, the molecular ion species of individual peptides may be focussed and transmitted into the collision cell of the tandem triple quadrupole mass spectrometer. Collision-induced dissociation of protonated peptide molecules yielded structural information for their characterization following injection of 10 pmol of a tryptic digest from human hemoglobin.

Acetonitriles↗
PubMed1991

Separation of carbohydrate-mediated microheterogeneity of recombinant human erythropoietin by free solution capillary electrophoresis. Effects of pH, buffer type and organic additives.

Free solution capillary electrophoresis has been investigated as an alternative to isoelectric focusing for the separation of the glycoforms of recombinant human erythropoietin (r-HuEPO), a primary regulator of erythropoiesis. A systematic approach was used to study the effect of pH, buffer type and organic modifiers on the resolution of the microheterogeneity of erythropoietin. The main factors for improving the resolution were the regulation of the electroosmotic flow of the running buffer and the reduction of solute-wall interaction. The best resolution of the glycoforms of r-HuEPO was obtained with a mixed buffer pH 4.0 (100 mM acetate-phosphate, 10 h preequilibration time).

Acetates↗
PubMed1991

Analysis of paralytic shellfish poisons by capillary electrophoresis.

A capillary electrophoresis (CE) method with UV detection is described for the separation and determination of underivatized toxins associated with paralytic shellfish poisoning (PSP). Confirmation of the electrophoretic peaks was facilitated by mass spectrometric (MS) detection using an ionspray CE-MS interface and by high-performance liquid chromatography with fluorescence detection. The determination of PSP toxins, such as saxitoxin and neosaxitoxin, in toxic dinoflagellates and scallops is demonstrated and comparisons are made with existing techniques.

Animals↗
PubMed1999

Open tubular capillary electrochromatography in etched, chemically modified 20 microns I.D. capillaries.

Fused silica capillaries with an I.D. of 20 microns are etched and then chemically modified by the silanization/hydrosilation method to attach an octadecyl moiety for use in electrokinetic chromatography. The etched capillaries after chemical modification are shown to have an anodic electroosmotic flow below pH 4.5. In comparison to bare 20 microns capillaries and unetched but chemically modified 20 microns capillaries, the etched C18 fused silica tubes show better separation of mixtures of lysozymes and cytochrome c's under identical conditions of buffer, pH and applied voltage. It was also demonstrated that this open tubular approach to capillary electrochromatography was amenable to a number of different types of basic compounds ranging in size from typical small amines to biomolecules. As expected, pH is an important variable that must be controlled in order to obtain an optimized separation. Reproducibility studies verify the stability of the silicon-carbon linkage produced in this modification method so that column lifetimes of at least 300 injections can be expected.

Capillary Action↗
PubMed1997

Lateral forces acting between particles in liquid films or lipid membranes.

To investigate the mechanism of formation of 2D arrays of protein macromolecules in liquid films we carried out model experiments with micron-sized latex particles. The direct observations revealed that the process of ordering is triggered by attractive lateral capillary forces due to the overlap of the menisci formed around the particles. Two types of lateral capillary forces, flotation and immersion, can be distinguished, and a theory of these interactions is developed. Similar forces are operative between inclusions (proteins) incorporated in lipid membranes. We develop an appropriate model of a lipid bilayer, which is described as an elastic layer (the hydrocarbon chain region) sandwiched between two Gibbs dividing surfaces (the two headgroup regions). The range of the interaction between two cylindrical inclusions turns out to be of the order of several inclusion radii. The results, which are in qualitative agreement with the experimental observations, can be applied to the interpretation of membrane processes and mechanisms such as protein aggregation in lipid membranes.

Capillary Action↗
PubMed1998

Surface characterization of biomedical materials by measurement of electroosmosis.

This paper reviews recent studies by the authors on the surface characterization of biomedically significant materials through electroosmosis determination. The surfaces studied include transparent and nontransparent materials such as quartz, ceramics, paper, and cast polymer capillaries, slides, and particles, in both native and surface modified form. The method is nondestructive, relatively fast, mechanistically simple, automatable to varying degrees, and can be used to analyze samples under physiologically compatible conditions. New experimental and mathematical modeling approaches allow estimates to be obtained with regard to the surface density and pK of various chemical groups, as well as the thickness of polymer or other surface coatings. Surface modifications which may be characterized include, covalent alteration via radiofrequency plasma discharge or organosilane grafting, noncovalent alteration via polymer adsorption, and covalent grafting of neutral polymers, such as poly(ethylene glycol) or dextran. Results complement those from other surface analysis techniques, and correlate with physiologically significant phenomena such as protein adsorption.

Biocompatible Materials↗