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Biomedical subjects

M A Rounds

Publications and source records attributed to M A Rounds.

7 recordsLinked to original sources
PubMed1993

Anion-exchange high-performance liquid chromatography with post-column detection for the analysis of phytic acid and other inositol phosphates.

The use of gradient anion-exchange HPLC, with a simple post-column detection system, is described for the separation of myo-inositol phosphates, including "phytic acid" (myo-inositol hexaphosphate). Hexa-, penta-, tetra-, tri- and diphosphate members of this homologous series are clearly resolved within 30 min. This method should facilitate analysis and quantitation of "phytic acid" and other inositol phosphates in plant, food, and soil samples.

Chromatography, High Pressure Liquid↗
PubMed1991

Semipermeable-surface reversed-phase media for high-performance liquid chromatography.

Polyoxyethylene was both adsorbed hydrophobically (through the use of non-ionic surfactants) and covalently bonded to reversed-phase high-performance liquid chromatographic packings, thereby establishing a semipermeable hydrophilic layer over the alkylsilane surface. This layer restricts proteins from adsorbing to the alkylsilane phase while permitting penetration and chromatographic separation of small molecules. Biological fluids containing low-molecular-weight analytes may be injected directly, without sample pretreatment or the use of micellar eluents. In the case of adsorbed coatings, surfactant loading was determined primarily by the surface area (over the reversed phase) occupied by the polyoxyethylene head group. Semipermeability of the hydrophilic layer was demonstrated by observing changes in retention of both small molecules and proteins with increasing eluent ionic strength. Coated column stability was evaluated with regard to cumulative eluent volume and repeated serum injections.

Adsorption↗
PubMed1988

Synthesis of a non-porous, polystyrene-based strong anion-exchange packing material and its application to fast high-performance liquid chromatography of proteins.

Adsorbed coating technology has been used to produce a strong anion-exchange stationary phase on 3-micron non-porous poly(styrene-divinylbenzene) particles. In order to take full advantage of the excellent kinetic properties of the resultant packing material, small columns of 5 mm X 6 mm I.D. were used. These columns were pressure- and pH-stable and allowed protein separations to be made in less than 1 min at ambient temperature.

Chemical Phenomena↗
PubMed1987

Poly(styrene-divinylbenzene)-based strong anion-exchange packing material for high-performance liquid chromatography of proteins.

An adsorbed polyethyleneimine coating was applied to sulfonated macroporous, microparticulate poly(styrene-divinylbenzene). The chemical, physical and chromatographic properties of the resulting strong anion-exchange packing material were thoroughly characterized. The dynamic load capacity of the experimental packing was comparable to that of large-pore diameter silica. Good recoveries of protein mass and enzyme activity were achieved. The new column withstood a variety of cleaning procedures and prolonged exposure to aqueous base. The retention times on the polystyrene-based column were similar to those on a silica and a commercial, polymeric, strong anion-exchange column. Chromatographic resolution of the new packing material was equal or superior to that provided by the other two packings.

Animals↗
PubMed1986

Factors contributing to intrinsic loading capacity in silica-based packing materials for preparative anion-exchange protein chromatography.

Properties of the matrix and stationary phase which affect the intrinsic loading capacity of silica-based packing materials for preparative anion-exchange chromatography of proteins were investigated. Polyethyleneimine-coated controlled porosity glass beads ranging from 100 to 2000 A in pore diameter were used to evaluate the effects of pore diameter and surface area. Protein binding was found to depend on accessible, rather than total, support surface area. Consequently, wide-pore, high surface area media provide maximum intrinsic loading capacity. Increasing the number of positively charged sites on the stationary phase by increased coating or by quaternization of amines increases hemoglobin-binding capacity.

Amines↗
PubMed1985

Stationary phase contributions to retention in high-performance anion-exchange protein chromatography: ligand density and mixed mode effects.

Several anion-exchange stationary phases (based on polyethyleneimine-coated silica) were synthesized so as to vary in ligand density and hydrophobicity. These materials were first examined for hemoglobin-binding capacity and then evaluated chromatographically. Protein binding, retention and resolution increased concomitantly with ligand density. Ferritin (molecular weight 440,000) could not be eluted from the more highly-charged surfaces, but was desorbed from a low ligand density support. The above parameters also varied with the hydrophobic character of the stationary phase. Retention and resolution increased as more hydrophobic moieties were added. Data from a non-ionic hemoglobin-binding assay correlated reasonably well with anticipated matrix hydrophobicities. Possible explanations and applications of the observed phenomena are discussed.

Amines↗