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Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments. [ABSTRACT FROM AUTHOR]

Haptic feedback for micro- and nanomanipulation is a research area of growing importance with many potential applications in micro- and biotechnology. Past research often involves the coupling of atomic force microscopes to haptic devices, but the results are not satisfactory. We propose to adopt a different approach, which consists of contactless manipulation, in particular by using optical tweezers, coupled with a haptic feedback device. In this article, we describe the potential of such a tool and show with some first experiments of stable interactions between micro-particles. [ABSTRACT FROM AUTHOR]

Hemoproteins usually supply cells and tissue with oxygen. A new hemoprotein mainly present in nerve cells called Neuroglobin was recently discovered. Enhanced expression of the protein has been shown to reduce hypoxic neural injury but the mechanism behind this function remains unknown. Methods enabling investigation of the protein in single functional neurons need to be developed. Here, we have studied how the electrical signaling capacity of a neuron was affected by hypoxic environments. Preliminary results show a trend of higher noise-level when a neuron is exposed to hypoxic compared to normoxic surroundings, which implies increased ion-channel activity. The setup used today shows shortages such as reduced control over the oxygen content due to leakage. Therefore, a gas-tight, multifunctional microfluidic system is under development which enables us to study influences of Neuroglobin concentrations on neuronal activity during hypoxia and anoxia. For electrophysiological recordings a patch-clamp micro pipette will be molded into the walls of the microfluidic system. A single biological cell is steered towards the pipette and attached there by means of optical tweezers. The Neuroglobin oxygen binding state will be studied using optical spectroscopy and the neuron environment will be manipulated by applying flows of varying oxygen content through the microfluidic system. This system will constitute a powerful tool in the investigation of the Neuroglobin mechanism of action. [ABSTRACT FROM AUTHOR]

Dynamic microarrays have great flexibility and potential as tools for advancing research in diagnostics and biomedical fields. In contrast with static microarrays such as DNA-chip using micro-spots of the bio-molecules, dynamic microarrays use a mobile substrate, usually micro-beads coated with bio-molecules. To realize the dynamic microarray, micro-bead handling techniques are essential, allowing us to transport the selected bead, and immobilize them for signal detection. Laser manipulation, known as optical tweezers, is one of the most suitable techniques for arranging and handling micro-beads. We have developed a multi-arm laser manipulation system with an excellent user-interface and realtime image processing functions. In this paper, we report a new approach for fully-automated assembly of a versatile dynamic micro-bead array. The beads, dispersed in a pipetted liquid on a cover glass, can be simultaneously trapped and sorted into a desired order, using multiple optical tweezers to transport the beads along collision-less paths guided by both computer vision and knowledge database techniques. Two typical examples are demonstrated. One is the fully-automated assembly of a 3x3 micro-bead array and its handling in 3D space. The other is the collision-free sorting of an array΄s elements. We also describe the experimental apparatus used in these demonstrations. [ABSTRACT FROM AUTHOR]