Ivar Giaever

Adsorption of ferritin

Abstract The adsorption of ferritin molecules onto both Lexan polycarbonate and carbon surfaces has been studied with the help of an electron microscope. The amount of ferritin adsorbed is a sensitive function of both the pH and the salinity of the ferritin solution. Complete coverage of a surface could be obtained only under very special conditions. Complete coverage is defined by a model calculation that places disks onto a surface at random and only those disks that do not overlap previous disks are adsorbed.

A simple model of electron emission through adsorbed molecules

Abstract When electron emission from a field emitter is visually observed on a phospor screen, images of two fold or four fold symmetry can be made to appear by depositing certain organic molecules onto the emitter tip. It is argued in this paper that under certain conditions the visually observed patterns are due to field emission from single molecules, and that the observed images reflect the symmetry of the local electric field around the molecules. A simple model calculation is carried out which explains most of the observed experimental features except the exact shape of the patterns of the experimental images.

PROTEIN DEPOSITION ON FIELD-EMITTER TIPS AND ITS REMOVAL BY UV RADIATION *

Abstract Protein deposition on field-emitter tips has been examined using Transmission Electron Microscopy to view the protein coated tip profile. A single layer of adsorbed protein is barely if at all detectable, but double and triple layers produced by the immunologic reaction can be directly observed. As a result, the thickness and morphology of antigen-antibody layers has been directly observed for the first time. Tips exposed first to Bovine Serum Albumin (BSA) and then to anti-BSA rabbit serum are covered with a reasonably uniform, double protein layer ≈130 A thick. This layer can be built-up to a triple layer ≈275 A thick by additional exposure to anti-rabbit IgG goat serum. Surface tension forces during the drying process which follows protein deposition appear to affect the thickness and morphology of the protein layers. The oxidation and subsequent change in the morphology of a protein layer exposed to ultraviolet radiation has also been observed using TEM. The destruction of a triple protein layer at a rate of ≈0.5 A/s is observed for tungsten tips exposed to ≈6 W of UV radiation from a high-pressure mercury arc in laboratory ambient. These results are compared to those obtained from a simple, visual test for protein layer adsorption in which submonolayer coverages of protein can be detected with the unaided eye.

An agglutination assay using emulsified oils

Dispersed fluorocarbon oil droplets were used as the antigen-carrier particle in an immunological agglutination assay. The extent of agglutination was found to vary with the percentage of antigen to that of inert protein used in the solution to coat and stabilize the oil droplets. Maximum sensitivity was observed when 6.25% of the protein adsorbed on the oil droplets was specific antigen. At this percentage, antibodies were detected at concentrations as low as 0.10 micrograms/ml. Results were obtained by visual examination of the reacted samples as well as with quantitative computer analysis using the Zeiss IBAS image analysis system.

A simple visual surface immunology test.

A new general immunology test is described which is capable of detecting protein in the 1 microgram/ml range. First an antigen is adsorbed in a small area of a glass surface. The glass is exposed to an antibody solution and the antibody will attach specifically to the antigen. Next the slide is washed, dried and sprayed lightly with plastic particles that stick to the protein layers on the glass. Now when the glass slide is exposed to an acid the antigen--antibody bonds are broken, the antibodies will leave the surface removing some of the plastic particles and leaving an easily visible spot behind.

Electric Cell-Substrate Impedance Sensing Concept to Commercialization

A personal account of the invention, growth and commercialization of Electric Cell-substrate Impedance Sensing (ECIS) by the inventors of the technology. From the first experiments at the General Electric Research and Development Center in the early 1980s to the outgrowth of applications and finally the incorporation of Applied BioPhysics, Inc., the chapter provides an historical and often amusing account of the evolution of ECIS.

Attachment and Spreading of Mammalian Cells in Vitro

When mammalian cells are seeded out in tissue culture they will drift down to the surface and firmly attach. The cells attach to a preadsorbed protein layers and not to the naked surface. Normally the protein layer will be a mixture of protein obtained from serum added to the tissue culture medium, but it is also possible to preadsorb pure protein layers onto the surface. This talk will discuss the many factors that affect the interaction of cells with surfaces including the time course of attachment and spreading and the forces that bind the cells to the protein layers.

The concept of inheritance takes shape: The road to understanding genetic engineering is paved with DNA

Everything we are is determined by the genetic information we carry. Forays into conquering disease and birth defects depend on understanding genes first. Through the millenia man has known that certain characteristics can be inherited. However, just what and where these genes were remained a mystery until the experiments of Avery, MacLeod, and McCarty (1944) revealed that a polymer called deoxyribonucleic acid (DNA) was in fact the genetic material responsible.

Measurement of antigen concentrations with a one-step inhibition assay

A device is described which is used to measure the concentration of antigen in solution. A wedge-shaped gap containing the antigen to be detected is bounded on one side by a reservoir containing specific antiserum and on the opposite side by a detection slide which has been previously coated with a layer of adsorbed antigen. As the antibodies diffuse through the gap, they complex with the soluble antigen in the wedge until these become saturated leaving additional antibody free to complex with antigen on the detection slide. By allowing diffusion to continue for an appropriate time, it is possible to relate the distance along the gap where this has occurred to the concentration of antigen within the gap. Using human IgG as a model antigen, we have been able to measure concentrations down to approximately 10 micrograms/ml with this test.

A Variation of the Radioimmune Assay

A novel method of radioimmune assay is described. It departs from conventional assays in that the radioiodine is reacted with protein following, rather than before, the antigen-antibody reaction. Using a BSA/anti-BSA system, the assay can detect antigen concentrations down to approximately 100 ng/ml.