Biomedical subjects
Publications and source records attributed to K Heinze.
A solid-phase synthesis approach for a class of molybdenum carbonyl complexes has been developed. The system can be used to perform metal-complexation, ligand substitution reactions and oxidative eliminations on the solid phase and to cleave the final complexes under mild and selective conditions. Comparison is made to corresponding soluble complexes and liquid-phase reactions.
By using mass spectrometry as an analytical tool to characterise substituted, cross-linked polystyrene resins, it is possible to directly monitor the progress of the solid-phase reactions performed on these resins without prior cleavage of the resin-bound molecules. Therefore, this is a true on-resin analytical method. The mass-to-charge ratios observed in the mass spectra are readily assigned to fragments of the polymer that include the chemically bound substituents. This is the first time that the formation and breaking of bonds have been directly observed on the polymeric support. Furthermore, the relative intensities of the signals in the mass spectra provide a measure of the completeness of the reaction. Because these measurements are rapidly performed without further chemical transformations or cleavage procedures, and because only minimal amounts of material are needed, this technique could become the solid-phase equivalent of thin-layer chromatography used in classical liquid-phase chemistry.
Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1(n+) (n=0-2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C(4) chain-a prerequisite for electrical conductivity and NLO properties of oligo- or polymeric materials.
We model the effect of gonadotropin-releasing hormone (GnRH) on the production of luteinizing hormone (LH) by the ovine pituitary. GnRH, released by the hypothalamus, stimulates the secretion of LH from the pituitary. If stimulus pulses are regular, LH response will follow a similar pattern. However, during application of GnRH at high frequencies or concentrations or with continuous application, the pituitary delivers a decreased release of LH (termed desensitization). The proposed mathematical model consists of a system of nonlinear differential equations and incorporates two possible mechanisms to account for this observed behavior: desensitized receptor and limited, available LH. Desensitization was provoked experimentally in vitro by using ovine pituitary cells in a perifusion system. The model was fit to resulting experimental data by using maximum-likelihood estimation. Consideration of smaller models revealed that the desensitized receptor is significant. Limited, available LH was significant in three of four chambers. Throughout, the proposed model was in excellent agreement with experimental data.
To evaluate the role of lysosomes in the breakdown of the carbohydrate and the polypeptide moiety of plasma membrane glycoproteins, degradation of the plasma membrane glycoprotein gp120 was studied in the liver of rats treated with the lysosomotropic amine chloroquine. Half-lives of degradation of the terminal sugar L-fucose and of L-methionine of gp120 were measured in isolated plasma membranes after pulse-chase experiments in vivo. Chloroquine extended the plasma membrane half-life of the polypeptide moiety of gp120 from 51 h to 143 h. By contrast, L-fucose of gp120 in the plasma membrane was not affected by chloroquine, but decayed with the same short half-lives of 22 h and 23 h in both controls and chloroquine-treated rats. The data suggest that the protein portion of gp120 is degraded within the lysosomes. Conversely, the terminal sugar L-fucose is removed from the glycoprotein independent from proteolysis before segregation of the glycoprotein into the lysosomal compartment.