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Biomedical subjects

N A Sommerdijk

Publications and source records attributed to N A Sommerdijk.

3 recordsLinked to original sources

beta -Helical polymers from isocyanopeptides.

Polymerization of isocyanopeptides results in the formation of high molecular mass polymers that fold in a proteinlike fashion to give helical strands in which the peptide chains are arranged in beta-sheets. The beta-helical polymers retain their structure in water and unfold in a cooperative process at elevated temperatures. The peptide architecture in these polymers is a different form of the beta-helix motif found in proteins. Unlike their natural counterparts, which contain arrays of large beta-sheets stacked in a helical fashion, the isocyanopeptide polymers have a central helical core that acts as a director for the beta-sheet-like arrangement of the peptide side arms. The helical structure of these isocyanopeptide polymers has the potential to be controlled through tailoring of the side branches and the hydrogen-bonding network present in the beta-sheets.

Alanine↗

Influence of inflammatory cells and serum on the performance of implantable glucose sensors.

The objective of this investigation was to evaluate the influence of polymorphonuclear granulocytes on the performance of uncoated and cellulose acetate/Nafion coated amperometric glucose sensors in vitro. The response of these sensors was also investigated in serum. Uncoated and coated sensors showed lower sensitivities to glucose, with a significant drift in sensor output upon exposure to serum or leukocytes. Although the use of a coating resulted in higher sensitivity, the progressive loss of output was not completely prevented. Stimulated granulocytes were shown to excrete components, probably catalase and myeloperoxidase, which consumed the hydrogen peroxide formed by the oxidation of glucose. In addition, adsorbed serum proteins formed a diffusional barrier for glucose. Furthermore, serum was found to contain low-molecular weight components that alone inhibited glucose oxidase activity. Based on preliminary electrochemical results, we postulate that rabbit serum contains oxidizing substrates that compete with molecular oxygen for the acceptance of electrons from the oxidized enzyme. Consequently, future efforts should be aimed at elucidating the mechanisms involved in the interference of unknown serum components with electron transfer. In addition, further investigations have to be performed to develop an outer membrane that minimizes protein adsorption as well as the actions of inflammatory cells.

Animals↗