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Biomedical subjects

I Lundström

Publications and source records attributed to I Lundström.

At least 91 records · Page 5Linked to original sources
PubMed1984

Stereospecific binding capacity of proteins on surfaces--simple mathematical models.

The adsorption of and interaction between protein molecules on solid surfaces are phenomena involved in many situations of biochemical and physical interest. This communication is an attempt to relate stoichiometrically substances binding to each other on surfaces. One experimental observation, which we try to explain, is that the maximum antibody binding capacity of an antigen covered surface does not always occur at the largest coverage of antigens.

Adsorption↗
PubMed1984

Complement factor adsorption on solid surfaces--an ellipsometric method for investigation of quantitative aspects.

An optical method, ellipsometry, has been used for quantification of organic material adsorbed from complement sufficient sera on antibody coated solid surfaces. Maximal adsorption of organic material from complement sufficient human sera occurred at about 0.5 micrograms/cm2 of IgG. C3 but not C5, C8 or C9 was detected on the antibody surface incubated with complement sufficient sera. This may indicate that IgG adsorbed on methylized silicon surfaces lack binding sites for complement factors beyond C3. A modification of the method was also used for quantification of migration inhibition of human polymorphonuclear leucocytes (PMNL). Locomotion inhibition fell in a sharp interval from 0.2 to 0.5 micrograms/cm2 of IgG on the surface. We believe that the suggested type of measurements is important for understanding the quantitative relationships between humoral effects such as antibody dependent complement activation and cellular effects such as migration of PMNL.

Adsorption↗
PubMed1984

The interaction of proteins and cells with affinity ligands covalently coupled to silicon surfaces as monitored by ellipsometry.

Two methods for the chemical binding of biomolecules to silicon surfaces are described. The first method utilizes an alkyl silane and a nucleophilic reagent to join the biomolecule to the silicon surface; the second method involves crosslinking with glutaraldehyde in order to couple the biomolecule and albumin molecules, which have first been physically adsorbed. The course of binding to the silicon surface has been followed with the aid of ellipsometry. This optical measuring technique estimates the thicknesses of, e.g., organic layers, by measuring the polarization properties of a light beam before and after reflection at surfaces. The method by which the binding of a biomolecule to its corresponding affinity ligand on silicon wafers can be followed with this technique is reported. The systems studied are concanavalin A-Saccharomyces cerevisiae cells, immunoglobulin G-Staphylococcus aureus cells, and an NAD-analog-lactate dehydrogenase. With ellipsometry it was possible to assess how the incubation time and the concentration of the cells and the biomolecules added influenced the results. It was found that an increasing time of incubation and higher concentration resulted in a more complete coverage of the silicon wafer surfaces.

Bacteria↗
PubMed1984

Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRAS) of fibrinogen adsorbed on metal and metal oxide surfaces.

We have investigated the possibilities of using Infrared Reflection Absorption Spectroscopy in the study of the interaction of proteins with metal surfaces. Structural information can be obtained since the infrared radiation at the metal surface interacts only with dipole transition moments perpendicular to the metal surface. Fibrinogen spontaneously adsorbed from solution onto gold, titanium and aluminum was used as model systems. The infrared studies were carried out on dried protein films. The amide I bands of fibrinogen adsorbed on the metal surfaces shift towards higher frequencies (ca. 20 cm-1) relative to the same band in buffer solution. The magnitude of these shifts indicates that conformational change of the protein occurs upon adsorption on metal surfaces. The change in conformation of the fibrinogen also can partly be due to one week of drying at room temperature. The amide I and amide II bands show a slightly different behaviour in terms of frequency and intensity for each metal-protein system studied. The side chains appeared to be more substrate sensitive than the peptide group. Orientational effects were observed for a number of side-chain related groups.

Adsorption↗
PubMed1983

The electrode adsorption method for determination of enzyme activity: a study of substrate requirements.

The electrode adsorption method for the determination of enzyme activity requires substrates that, besides having good kinetics constants for the enzyme, also show good adsorption/desorption kinetics to the electrode surface and adsorb in such a way that they change the double-layer capacitance of the electrode. A series of peptide substrates containing one to three aromatic groups has been synthesized. Our results show that the aromatic groups are of crucial importance for the capacitance change caused by the adsorbing/desorbing substrate. Thus, the tripeptide substrate, Bz-Phe(NO2)-Val-Arg-pNA, with three aromatic groups is superior to the other synthesized substrates containing only one or two aromatic groups. Our desorption experiments show that several factors determine the rate of capacitance increase observed when thrombin is added to a substrate solution in equilibrium with a substrate-covered electrode. The kinetic constants of the substrate determine how the substrate concentration in the solution decreases and, consequently, determine the spontaneous desorption measured as capacitance increase. Thrombin does not seem to split adsorbed substrate molecules but it adsorbs to the substrate-covered surface and in that way causes a capacitance decrease counteracting the change caused by desorption of substrate.

Adsorption↗
PubMed1983

Electron microscopic analysis of the bone-titanium interface.

Ten cylindrical implants, made of polycarbonate and covered with a 120-250-nm-thick layer of pure titanium, were implanted into each tibial metaphysis of five rabbits. Observation time was 12 weeks. The implants were surrounded by mature, living bone. No soft tissue intervened between bone and implant at any point. With TEM microscopy the titanium was shown to be bordered by a 20-nm-thick layer of proteoglycans, showing the characteristics of ground substance, and separating the collagen from the implant surface. Cells at the interface were likewise separated from the titanium by such a layer. Hydroxyapatite crystals were observed within the ground substance layer, occasionally seemingly in direct contact with the titanium. Normal mineralization was present 100-500 nm from the implant surface. While this study aims at defining interface anatomy, it also shows that macroscopically smooth-surfaced titanium can readily heal into bone without a soft tissue envelope. This could be of help for materials' choice and design of permanently fixed implants.

Animals↗
PubMed1982

Ellipsometric studies of film formation on tooth enamel and hydrophilic silicon surfaces.

The uptake of salivary substances onto hydrophilic negatively charged surfaces of silicon or onto enamel surfaces was studied in vitro with ellipsometry. There was a rapid initial uptake of substances followed by a slow but continuous uptake probably of other substances, which could be removed from saliva by absorption with a S. mutans serotype c strain. the kinetics for the uptake onto enamel and silicon surfaces and the thicknesses of the layers were similar. The combination of ellipsometry and silicon surfaces is suggested as a model for obtaining increased information on dental pellicle formation.

Chemical Phenomena↗
PubMed1979

The isoelectric point of thrombin and its behaviour compared to prothrombin at some solid surfaces.

We have shown that the isoelectric point of thrombin is high and that thrombin is a cation at the pH of blood. On the other hand, prothrombin has a low isoelectric point, being more anionic at the pH of blood. It was also found that thrombin adsorbs readily to surfaces, especially negatively charged surfaces, like behenic acid surfaces at pH 8.2. Furthermore, thrombin adsorbed onto behenic acid was active in the sense that it coagulated fibrinogen. The significance of the electric charge of the thrombin molecule in the mechanism of atherosclerosis is discussed.

Adsorption↗