Biomedical subjects

Detlev Drenckhahn

Publications and source records attributed to Detlev Drenckhahn.

22 records · Page 2Linked to original sources

PubMed2002

An expectation-maximisation algorithm for the deconvolution of the intrinsic distribution of single molecule's parameters.

Values obtained from single molecule techniques exhibit distinct distributions comprising an uncertainty due to random noise convoluted with the intrinsic distribution of the molecule's properties. In the fields of single molecule light microscopy and spectroscopy, force microscopy and spectroscopy as well as other techniques like electrophysiology, sophisticated data analysis algorithms are available which extract the interesting parameters and their uncertainties from the noisy data set. The intrinsic distributions of these parameters contain valuable information about the molecules' physical and chemical properties, that need to be deconvoluted from the data. Here, we present an expectation-maximisation (EM-) algorithm that estimates the intrinsic distribution in single molecule experiments. The performance is tested by using computer simulations and the application of the method is demonstrated for data from single molecule force spectroscopy.

Algorithms↗

PubMed2002

Transmembrane cooperative linkage in cellular adhesion.

Various dynamic cellular activities require precise regulation of extracellular adhesion. Here we propose a simple thermodynamic model that does not depend on affinity regulation of transmembrane adhesion molecules but, rather, is based on the principles of collision-limited reactions. We show that the number of transmembrane adhesion molecules forming extracellular bonds depends on the degree of cytoskeletal damping of their lateral mobility (translational entropy) within the plane of the plasma membrane. This type of transmembrane cooperativity between cytoskeletal linkage and the number of extracellular bonds does not require high affinities to the cytoskeleton (micromolar range) and will be particularly effective at low extracellular affinities of adhesion molecules (millimolar range).

Cell Adhesion↗

PubMed1999

Chemosensory Perception in the Gut.

The ability of the gut mucosa to sense the chemical composition of chyme is important for gastrointestinal functions. The demonstration of gustducin and transducin, two alpha-subunits of GTP-binding proteins involved in gustatory signal transduction, in gastrointestinal epithelial cells provides first clues to the molecular basis of enteric chemosensitivity. Nitric oxide may play a role as a secondary messenger.

Journal Article↗

PubMedDate not supplied

Dynamic force microscopy imaging of native membranes.

We employed magnetic ACmode atomic force microscopy (MACmode AFM) as a novel dynamic force microscopy method to image surfaces of biological membranes in their native environments. The lateral resolution achieved under optimized imaging conditions was in the nanometer range, even when the sample was only weakly attached to the support. Purple membranes (PM) from Halobacterium salinarum were used as a test standard for topographical imaging. The hexagonal arrangement of the bacteriorhodopsin trimers on the cytoplasmic side of PM was resolved with 1.5nm lateral accuracy, a resolution similar to images obtained in contact and tapping-mode AFM. Human rhinovirus 2 (HRV2) particles were attached to mica surfaces via nonspecific interactions. The capsid structure and 2nm sized protein loops of HRV2 were routinely obtained without any displacement of the virus. Globular and filamentous structures on living and fixed endothelial cells were observed with a resolution of 5-20nm. These examples show that MACmode AFM is a favorable method in studying the topography of soft and weakly attached biological samples with high resolution under physiological conditions.

Capsid↗