Biomedical subjects

F Ohnesorge

Publications and source records attributed to F Ohnesorge.

4 recordsLinked to original sources

PubMed1992

In situ investigations of single living cells infected by viruses.

In this paper we report the direct observation of biological processes on living cells. The experiments were done in situ by scanning force microscopy on a scale inaccessible by other techniques under physiological conditions. Living monkey-kidney cultured cells were imaged under normal growth conditions and showed reproducible features on the 10 nm scale. Upon adding a suspension of pox viruses, characteristic changes of the cell membrane were repeatedly observed in different experiments on different cells. Almost immediately, a pronounced softening of the cell surface occurred which lasted only for a few minutes. More than two hours later very significant protrusions appeared to grow out of the cell membrane. These protrusions abruptly disappeared again. These events were only observed after infection and we interpret them as the exocytosis of proteins related to viral reproduction. After almost 20 h, a different type of event occurred which we interpret as the exocytosis of the progeny viruses themselves.

Animals↗

PubMed1992

Scanning force microscopy studies of the S-layers from Bacillus coagulans E38-66, Bacillus sphaericus CCM2177 and of an antibody binding process.

In many prokaryotic cells (eubacteria and archaebacteria) the outermost cell envelope component is composed of a regularly structured protein surface layer (S-layer). The two-dimensional S-layer from Bacillus coagulans E38-66 and Bacillus sphaericus CCM2177 has been investigated by SFM at molecular resolution under physiological conditions (i.e., in buffer solution). We find the E38-66 S-layer lattice to be oblique with lattice parameters of a = 9-10 nm, b = 7-8 nm and gamma = 80 degrees -90 degrees (E38-66). The CCM2177 lattice is square with a = 12-14 nm, in good agreement with TEM data. We have used the unique possibility of the SFM to study the kinematics of biological processes and have performed experiments on the adhesion of polyclonal antibodies to the recrystallized E38-66 protein layer on a time scale of about two to ten seconds per image frame. This represents a first step in directly visualizing molecular recognition reactions.

Antibodies, Bacterial↗

PubMed1992

Investigation of living cells in the nanometer regime with the scanning force microscope.

Membrane structures of different types of cells are imaged in the nanometer regime by scanning force microscopy (SFM). The images are compared to those obtained with a scanning electron microscope (SEM). The SFM imaging can be done on the outer cell membrane under conditions that keep the cells alive in aqueous solutions. This opens up the possibility of observing the kinematics of the structures that determine the interaction of a cell with its environment. Therefore, STM observations, together with information obtained with the electron microscope, open up new ways of studying the development of biological structures. With the currently possible resolution, the SFM gives access to processes such as antibody binding or endo- and exocytosis, including processes correlated to the infection of cells by viruses.

Animals↗

PubMed1990

Immobilized proteins in buffer imaged at molecular resolution by atomic force microscopy.

Samples of supported planar lipid-protein membranes and actin filaments on mica were imaged by atomic force microscopy (AFM). The samples were fully submerged in buffer at room temperature during imaging. Individual proteins bound to the reconstituted membrane were distinguishable; some structural details could be resolved. Also, surface-induced, self-assembling of actin filaments on mica could be observed. Monomeric subunits were imaged on individual actin filaments. The filaments could be manipulated on or removed from the surface by the tip of the AFM. The process of the decoupling of the filamentous network from the surface upon changing the ionic conditions was imaged in real time.

Actins↗