Biochemistry

An RNA crystallization chaperone

The crystallization of RNA molecules for structural analysis is even more challenging than protein crystallization owing to the low chemical diversity, flexibility and conformational heterogeneity of RNA. Koldobskaya et al. introduce a chaperone system that stabilizes RNA structure and promotes crystallization. The chaperone is an antigen-binding fragment (Fab) that recognizes an epitope tag that can be installed on any RNA of interest.

Koldobskaya, Y. et al. Nat. Struct. Mol. Biol. 18, 100–106 (2011).

Biophysics

Video force microscopy

Brodland et al. introduce a technique called video force microscopy, which is used to noninvasively generate detailed force maps of tissues from time-lapse multiphoton images. The method involves discretizing tissue into polygonal regions and tracking the corners of these regions to quantify deformations, allowing the user to determine whether the deformations are a result of active or passive forces. Brodland et al. used the method to measure the driving forces responsible for ventral furrow formation in Drosophila melanogaster embryos.

Brodland, G.W. et al. Proc. Natl. Acad. Sci. USA 107, 22111–22116 (2010).

Epigenetics

Distribution of 5-hydroxymethylcytosine in the genome

As 5-hydroxymethylcytosine (5-hmC) is a recently discovered epigenetic modification, little is currently known about its distribution and functional roles. Song et al. have now developed a method for mapping the genome-wide distribution of 5-hmC. The method involves using a β-glucosyltransferase to transfer a glucose containing an azide handle onto 5-hmC; the azide can then be tagged with biotin for enrichment and sequencing of the captured DNA fragments containing 5-hmC.

Song, C.-X. et al. Nat. Biotechnol. 29, 68–72 (2011).

Proteomics

Protein-lipid interactions

Besides building cellular membranes, lipids operate as important signaling molecules via their interactions with proteins, but knowledge of these interactions is incomplete. Gallego et al. report a systematic, unbiased screening approach to identify protein-lipid interactions in the yeast Saccharomyces cerevisiae by detecting protein binding to miniature lipid arrays. Gallego et al. identified 530 protein-lipid interactions, most of which were previously unknown.

Gallego, O. et al. Mol. Syst. Biol. advance online publication, 30 November 2010.

Cell biology

Carbon nanotube endoscopes

Glass pipettes are useful tools for making electrophysiological measurements and injecting substances into cells, but because of their large size they can damage the cell. Singhal et al. introduce a carbon nanotube–based 'endoscope', 10 times smaller than a typical glass pipette, which can be used to probe cells with 100-nanometer spatial resolution, including intracellular organelles. The endoscope can also be used to deliver fluids to the cell, something previous carbon nanotube–based probes could not do.

Singhal, R. et al. Nat. Nanotechnol. 6, 57–54 (2011).