PubMed HealthSearch

PubMed · 9352509

Basic laser tweezers.

Abstract

The basic information has been provided here for designing and building a laser tweezers system for force measurements. If force measurements are not required, then the considerations about the analysis system, a fine piezo stage, and stability are less important. For the initial alignment and characterization of the system, red blood cells provide an easily trapped sample. For a difficult test sample, the smaller latex beads (0.15-0.3 micron in diameter) are stable and easy to obtain. Anyone setting up laser tweezers is encouraged to see a working tweezers system and to compare samples with that system. Everyone has a different background, and there may be aspects critical for you that have not been discussed here. More sophisticated systems are described later in this book.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

R E Sterba, M P Sheetz. 1998. Basic laser tweezers.. https://pubmed.ncbi.nlm.nih.gov/9352509/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

RST: a connectionist architecture to deal with spatiotemporal relationships.

In the past decade, connectionism has proved its efficiency in the field of static pattern recognition. The next challenge is to deal with spatiotemporal problems. This article presents a new connectionist architecture, RST (réseau spatio temporel [spatio temporal network]), with such spatiotemporal capacities. It aims at taking into account at the architecture level both spatial relationships (e.g., as between neighboring pixels in an image) and temporal relationships (e.g., as between consecutive images in a video sequence). Concerning the spatial aspect, the network is embedded in actual space (two) or three-dimensional-, the metrics of which directly influence its structure through a connection distribution function. For the temporal aspect, we looked toward biology and used a leaky-integrator neuron model with a refractory period and postsynaptic potentials. The propagation of activity by spatiotemporal synchronized waves enables RST to perform motion detection and localization in sequences of video images.

Image Processing, Computer-Assisted

Ultra-fast velocity imaging in stenotically produced turbulent jets using RUFIS.

A method for rapidly producing velocity images is presented. This sequence combines a modified bipolar gradient pulse to magnitude encode the velocity with the rotating ultra-fast imaging sequence (RUFIS) to image the encoded spins. Velocity encoding is done in 3 msec, and RUFIS acquires 32 projections in 8 msec. The method is applied to turbulent jets associated with a 75% stenosis in a 15-mm inner diameter glass pipe. Data is acquired upstream and downstream from the stenosis for Reynolds numbers from 560 to 3750. In addition, a robust method of reconstructing the unobserved short time region of a free induction decay is presented and incorporated into the image processing.

Image Processing, Computer-Assisted

The first step: activation of the Semliki Forest virus spike protein precursor causes a localized conformational change in the trimeric spike.

The structure of the particle formed by the SFVmSQL mutant of Semliki Forest virus (SFV) has been defined by cryo-electron microscopy and image reconstruction to a resolution of 21 A. The SQL mutation blocks the cleavage of p62, the precursor of the spike proteins E2 and E3, which normally occurs in the trans-Golgi. The uncleaved spike protein is insensitive to the low pH treatment that triggers membrane fusion during entry of the wild-type virus. The conformation of the spike in the SFVmSQL particle should correspond to that of the inactive precursor found in the early stages of the secretory pathway. Comparison of this "precursor" structure with that of the mature, wild-type, virus allows visualization of the changes that lead to activation, the first step in the pathway toward fusion. We find that the conformational change in the spike is dramatic but localized. The projecting domains of the spikes are completely separated in the precursor and close to generate a cavity in the mature spike. E1, the fusion peptide-bearing protein, interacts only with the p62 in its own third of the trimer before cleavage and then collapses to form a trimer of heterotrimers (E1E2E3)3 surrounding the cavity, poised for the pH-induced conformational change that leads to fusion. The capsid, transmembrane regions and the spike skirts (thin layers of protein that link spikes above the membrane) remain unchanged by cleavage. Similarly, the interactions of the spikes with the nucleocapsid through the transmembrane domains remain constant. Hence, the interactions that lead to virus assembly are unaffected by the SFVmSQL mutation.

Image Processing, Computer-Assisted