Biocurious is a weblog about biology, quantified.

Hot off the Press: Lots

by PhilipJ on 3 August 2006

There have been a bunch of neat biophysics papers this week (and a few from last that are worth mentioning), so I’ll note them all here! Unfortunately, all but one are open access.

From this week’s PNAS:

Macromolecular-scale resolution in biological fluorescence microscopy (open access!)
Stefan Hell’s lab has been working on breaking the diffraction limit for fluorescence imaging for years, and in this paper demonstrate focal plane resolution of ~20 nanometres! Normal diffraction limited measurements are approximately an order of magnitude larger, smearing out the signal from single molecules. Using their new approach, individual single molecules can be visualised, and no longer look like simply huge blobs of light.

Tension-dependent DNA cleavage by restriction endonucleases: Two-site enzymes are `switched off’ at low force
Many restriction endonucleases loop up their template DNA and bind to two distinct sections before carrying out their enzymatic activity, and it has been long suspected that this activity could be inhibited by applying some force (and therefore making it less likely for the DNA to loop). Using optical tweezers, the Smith lab did just so, and found that for known looping enzymes the activity was almost entirely inhibited with the application of as little as 0.7 pN, while known single-site cutters were essentially unaffected by the applied forces.

Cellular asymmetry and individuality in directional sensing
Quoted verbatim: “It is generally assumed that single cells in an isogenic population, when exposed to identical environments, exhibit the same behavior. However, it is becoming increasingly clear that, even in a genetically identical population, cellular behavior can vary significantly among cells. Here we explore this variability in the gradient-sensing response of Dictyostelium cells when exposed to repeated spatiotemporal pulses of chemoattractant. Our experiments show the response of a single cell to be highly reproducible from pulse to pulse. In contrast, a large variability in the response direction and magnitude is observed from cell to cell, even when different cells are exposed to the same pulse.”

From this week’s Nature:

Adaptive liquid microlenses activated by stimuli-responsive hydrogels
We seem to be “into microlenses” here at BioCurious. In this article, “we demonstrate a liquid lens system that allows for autonomous focusing. The central component is a stimuli-responsive hydrogel13 integrated into a microfluidic system and serving as the container for a liquid droplet, with the hydrogel simultaneously sensing the presence of stimuli and actuating adjustments to the shape—and hence focal length—of the droplet.”

The gender debate: science promises an honest investigation of the world
Steven Pinker weighs in with a brief comment on the Barres article (Does gender matter?) that caused such a stir around the blogosphere.

Finally, in last week’s Nature, there was a special on microfluidics that was very enjoyable to read. Some choice articles: George Whitesides on the past and future of microfluidics, Stephen Quake and others on merging optics and microfluidics, and Harold Craighead on microfluidics applied to single molecule studies. Good stuff.

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