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Biomedical subjects

M Kempe

Publications and source records attributed to M Kempe.

9 recordsLinked to original sources
PubMed2002

New perfluorocarbon system for multilayer growth of anchorage-dependent mammalian cells.

A novel tissue culture system has been developed that supports the multilayer growth of Hep G2 cells. The system consists of growing cells on collagen-coated perfluorocarbon substrata in the wells of a multi-well plate designed so that, even at very high densities, the oxygen in the cultures is replenished as rapidly as it is consumed. Hep G2 cells, which are typically contact inhibited, grow to form more than 10 layers of cells that continue to secrete albumin. Both multilayer growth and high rates of albumin depend on using a very enriched nutrient medium, compared to media usually used for monolayer culture of Hep G2 cells. The role played by increased oxygenation, enriched media, and the unique properties of the perfluorocarbon substrata for the 3-D growth of anchorage-dependent cells is discussed.

Animals↗
PubMed1996

Antibody-mimicking polymers as chiral stationary phases in HPLC.

Antibody-mimicking synthetic polymers, selective for various optically active amino acid derivatives and peptides, were prepared by noncovalent molecular imprinting. A novel approach, in which the branched, trifunctional cross-linkers pentaerythritol triacrylate and 2,2-bis(hydroxymethyl)butanol trimethacrylate were copolymerized with methacrylic acid, is described. The polymers were subsequently applied as chiral stationary phases in high-performance liquid chromatography. They were superior to previously reported noncovalent molecularly imprinted polymers used for chiral separations in that they showed considerably higher load capacity, increased selectivity, and better resolving capability.

Amino Acid Sequence↗
PubMed1995

Separation of amino acids, peptides and proteins on molecularly imprinted stationary phases.

Stationary phases, to be used in high-performance liquid chromatography, were tailor-made for the separation of amino acids, peptides and proteins. The stationary phases were prepared by molecular imprinting, applying two different approaches. Low-molecular-mass compounds were imprinted in bulk polymers by copolymerization of functional monomers and cross-linkers in the presence of the compound of interest, the print molecule. These polymers were, after extraction of the print molecule, successfully applied as chiral stationary phases, showing high resolution and load capacity. The development of a surface-imprinting approach for the preparation of stationary phases selective for proteins is also discussed.

Amino Acid Sequence↗
PubMed1994

Chiral recognition of N alpha-protected amino acids and derivatives in non-covalently molecularly imprinted polymers.

Highly crosslinked synthetic polymers, selective for various N alpha-protected amino acids and derivatives, were prepared by non-covalent molecular imprinting. Methacrylic acid and ethylene glycol dimethacrylate were copolymerized in the presence of the print molecules, which were subsequently extracted from the polymers. The recognition of the polymers for the print molecules and molecules of similar structures was investigated by using the polymers as stationary phases in HPLC. The functional groups of the print molecules interact via hydrogen bonds with the positioned carboxyls of the polymer. It was shown that the N alpha-protecting group, the C alpha-protecting group and the amino acid side chain are also recognized by the binding sites in the polymer.

Amino Acids↗
PubMed1993

Chiral separation using molecularly imprinted heteroaromatic polymers.

Novel molecularly imprinted polymer systems utilizing 4-vinylpyridine and 1-vinylimidazole as functional monomers have been developed for enantioselective recognition of carboxylic and N-protected amino acids. Non-covalent interactions between the functional monomers and the template molecules were the source of the subsequent recognition sites in the resultant polymers. The capacity of the polymers for molecular recognition was investigated by using them as stationary phases in the HPLC mode. Polymers prepared with 4-vinylpyridine were found to be more efficient in racemic resolution than those prepared with 1-vinylimidazole. When applying a racemic mixture of the template molecule, the polymers showed highest affinity for the enantiomer used as template. Imprints of a racemic template molecule, as expected, did not exhibit enantioselectivity. The optimal molar ratio of 4-vinylpyridine to the template Cbz-L-Asp-OH in the polymerization mixture was determined to be 12:1. In addition to enantioselectivity, the investigated polymers demonstrated 'ligand selectivity', e.g., a Cbz-L-Asp-OH-imprinted polymer was able to separate Cbz-D,L-Asp-OH, but was unable to separate Cbz-D,L-Glu-OH.

Chromatography, High Pressure Liquid↗
PubMed1990

Enzymatic synthesis of dipeptide units of the D-D-configuration in aqueous media.

The enzymatic synthesis of dipeptide units of the D-D-configuration in aqueous media, catalysed by muramoyl-pentapeptide carboxypeptidase (E.C.3.4.17.8), is described. Ac-L-Lys(Ac)-D-Ala-D-Lac-OH and Ac-D-Ala-OMe were used as acyl-components. Neutral, basic, and hydrophobic amino acids acting as nucleophiles were incorporated. The enzyme is stereospecific in that only the D-enantiomers of amino acids or amino acid derivatives were incorporated. As nucleophiles, the unmodified amino acids resulted in higher product yields compared with using the corresponding amino acid derivatives. Product yields ranged from 40 to 87%.

Amino Acid Sequence↗
PubMedDate not supplied

An approach towards surface imprinting using the enzyme ribonuclease A.

An adsorbent showing enhanced selectivity for the enzyme RNase A was prepared by a surface imprinting procedure based on metal coordination. A metal chelating monomer, N-(4-vinyl)-benzyl iminodiacetic acid, was polymerized onto methacrylate-derivatized silica particles in the presence of RNase A and metal ions. Lysozyme and RNase A were separated on the adsorbent used as stationary phase in high-performance liquid chromatography.

Adsorption↗