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Biomedical subjects

Ernö Pretsch

Publications and source records attributed to Ernö Pretsch.

7 recordsLinked to original sources
PubMed2003

Role of fulvic acid on lead bioaccumulation by Chlorella kesslerii.

To better understand the relationship between lead speciation and bioavailability in natural freshwaters, the interaction of lead with the freshwater alga Chlorella kesslerii was studied in the presence of the Suwannee River fulvic acid (SRFA). Special attention was paid to direct interactions of the fulvic acid on the algae, as well as potential physiological (membrane permeability and algal metabolism) influences. Lead-free ion concentration measurements were carried out using a novel ion-selective electrode. Pb uptake decreased in the presence of SRFA with respect to noncomplexed Pb, but uptake fluxes, cellular Pb, Pb bound to the transport sites, and total adsorbed Pb were all higher than predicted from Pb2+ activities, in accordance with the free ion activity model (FIAM). The discrepancies between the observed values and those predicted by the FIAM in the presence and absence of synthetic ligands increased with increasing concentration of SRFA. Several hypotheses were examined to explain the observed differences. No contributions of labile and/or hydrophobic Pb-SRFA complexes were found. Furthermore, direct biological effects, including variations in membrane permeability or algal metabolism, could not account for the observations. On the other hand, changes in the algal surface charge due to SRFA adsorption seemed to account, at least partially, for the observed increase in lead uptake in the presence of SRFA as compared to that corresponding to the same Pb2+ concentration in the presence of synthetic ligands.

Adsorption↗
PubMed2002

Rational design of potentiometric trace level ion sensors. A Ag+-selective electrode with a 100 ppt detection limit.

Submicromolar to picomolar lower detection limits have recently been obtained with various polymer membrane ion-selective electrodes by minimizing biases due to ion fluxes through the membrane. For the best performance, the compositions of the membrane and inner solution should be optimized for each application. Given the number of parameters to be adjusted, it has been difficult to find the best parameters for a target sample. In this paper, a much simplified and more practical steady-state model of zero-current ion fluxes is derived, which is based on measurable parameters. The model allows one to predict achievable lower detection limits for a membrane with given selectivities. It can also be used to predict the optimal composition of the inner filling solution for the measurement of samples with a known, typical ionic background. Selectivity coefficients of monovalent and divalent analyte ions required for desired detection limits in drinking water are calculated. As an application of the proposed general recipe, a silver-selective electrode is developed on the basis of the ionophore O,O''-bis[2-(methylthio)ethyl]-tert-butylcalix[4]arene. With the predicted optimal composition of the inner electrolyte, its lower detection limit is found to be 10(-9) M or 100 ppt Ag+ with an ionic background of 10(-5) M LiNO3, which is very close to the expected value.

Cations, Divalent↗
PubMedDate not supplied

Immobilization of biomolecules on polyurethane membrane surfaces.

Lipophilic polymer membranes incorporating binding sites are widely used in various potentiometric, amperometric, and optical sensors. Here, we report on the biofunctional modification of the surface of a Ca(2+)-selective membrane. A photoactivatable biotin derivative was synthesized and covalently immobilized on a soft polyurethane membrane. The modified polymer was characterized by X-ray photoelectron spectroscopy (XPS) as well as by potentiometric measurements. The selective binding of streptavidin by the photo-cross-linked biotin derivative was demonstrated. The surface coverage obtained with different experimental protocols was analyzed by autoradiography using [(35)S]-streptavidin. The new approach may significantly extend the scope of applicability of potentiometric sensors.

Autoradiography↗
PubMedDate not supplied

Automatic spectra interpretation, structure generation, and ranking.

A new rule-based spectra interpretation system is described. It directly processes spectral files generated by spectrometers. Its internal information representation and the simultaneous use of several spectroscopic methods allow for the achievement of both high reliability and good performance. For small and medium sized molecules, the new program is capable of automatically reducing the solution space to under 3%.

Journal Article↗