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Dec. 18, 2009

Optical Tweezer Experiments

Optical trapping techniques have evolved to the point where quantitative force measurements on biological systems can be performed down into the femtonewton range. As resolution is constantly improving, the pinpointing and elimination of noise sources become increasingly important. Allan-variance analysis is ideally suited for this task; adjacent time series are recorded and the variations between observation intervals are calculated. more
Dec. 17, 2009

Gradient Optical Traps

The powerful results in the molecular and cellular domain that are currently obtained using optical tweezers are leading to an increasing interest in this biophysical tool. Once calibrated, laser traps can be used to accurately measure the forces and displacements involved in many different molecular processes. Unfortunately, standard force detection techniques are not suitable for experiments inside living cells. more
Dec. 17, 2009

Protrusion Force Measurements with the SFM on Motile Cells

A fundamental step in cell migration is the advancement of the cell's leading edge. It is generally accepted that this motion is driven by actin polymerization against the plasma membrane but this has not been directly measured. more
Dec. 16, 2009

The “Walking” Mechanism of Kinesin-1 in 3D

Kinesin-1 is a molecular motor essential for cellular function. It transports components such as membrane-bound organelles and molecular complexes around a cell by travelling along microtubule filaments, which make up part of the cytoskeleton, while hydrolysing ATP. This motion is processive, in one direction only and is known to involve both of kinesin's two heads. Although extensively studied by a variety of techniques over many years, the mechanism these single-molecule motors use for this efficient motion on the nanoscale is not fully understood. more
FRET and Translocation in Cell-based Imaging
Dec. 14, 2009

FRET and Translocation in Cell-based Imaging

Microscopy in combination with fluorescence labeling techniques has enabled us to look at diverse biological processes. By tagging a protein of interest, we learn about its intracellular localization and dynamics. Fluorescence resonance energy transfer (FRET) sensors, which carry two fluorescent tags instead of one, a donor and an acceptor, are generated to obtain information about protein function. While the use of multiple labels is straightforward and common in high content imaging and screening, the use of multiple FRET sensors is more difficult. more
Dec. 14, 2009

Holographic Optical Tweezers

The actin cortex, a quasi two-dimensional network of actin, plays an important role in cell stability, motility and viscoelasticity. In vivo, its characteristic properties are controlled by various actinbinding proteins (ABPs), such as crosslinkers or ions. To investigate the influence of specific crosslinkers on the network's behaviour exclusively, we create and probe biomimetic models of the actin cortex. This is realized using microbeads trapped by holographic optical tweezers (HOTs) as scaffold for the actin filaments. more
Bioactive Surfaces Based on PEG Brushes
Dec. 07, 2009

Bioactive Surfaces Based on PEG Brushes

The control over cell-surface interactions is a highly important issue for biomedical and biotechnology applications. Novel thermoresponsive PEG (Poly(ethylene glycol) surface coatings allow convenient control over the cell adhesion and do not interfere with membrane proteins. Here we benchmark the ability of the surfaces to control cell adhesion and quantify the interfacial interactions via colloidal probe atomic force microscopy (AFM). more
Making Light Sound
Nov. 30, 2009

Making Light Sound

Optical interrogation of biological tissues offers great variety of intrinsic probing mechanisms as well as highly specific contrast approaches based on tissue-specific expression of fluorescent proteins and extrinsically administered molecular biomarkers. Yet, most of the important living organisms and tissues remain inaccessible by the current optical imaging techniques due to complications arising from intense light scattering in tissues. more
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