Microscopy

High-speed super-resolution imaging

Methods for imaging fluorescent samples at resolutions much greater than possible with conventional imaging have only begun to be applied to living cells. Westphal et al. adapted one of the earliest super-resolution methods, stimulated emission depletion (STED) microscopy, for video-rate super-resolution imaging of fluorescently labeled synaptic vesicles in living cells. These structures were ideally suited for a first demonstration of this method but improvements should permit application to other systems.

Westphal, V. et al. Science, published online 21 February 2008.

Proteomics

Cracking the histone H4 code

The post-translational modifications on histone tails known as 'codes' guide DNA-chromatin interactions. Phanstiel et al. describe a method using nanoflow high-performance liquid chromatography to separate intact histone tails, combined with high-resolution mass spectrometry–based sequencing, and applied it to decipher the combinatorial histone H4 codes in human embryonic stem cells undergoing differentiation.

Phanstiel, D. et al. Proc. Natl. Acad. Sci. USA, published online 7 March 2008.

Imaging and visualization

Lighting up synapses

Assessing synaptic connectivity in the dense nerve bundles of the nervous system is very challenging. Feinberg et al. describe a method to label synapses in Caenorhabditis elegans by expressing complementary GFP fragments tethered to transmembrane proteins on different cells. With complementation of the GFP fragments, fluorescence is restored, and this signals the proximity of the presynaptic and postsynaptic plasma membranes.

Feinberg, E.H. et al. Neuron 57, 353–363 (2008).

Protein biochemistry

Counting disulfide bonds

Large-scale structural analysis of proteins containing multiple disulfide bonds has been difficult owing to the absence of methods for distinguishing their native forms from misfolded intermediates. Narayan et al. now describe a method that uses mild reduction to selectively reduce the less stable non-native disulfide bonds and chemical blocking of free cysteines, coupled with mass spectrometry to determine the number of disulfide bonds, thus allowing native forms of proteins in mixtures to be distinguished.

Narayan, M. et al. Nat. Biotechnol., published online 17 February 2008.

Biophysics

Molecular cutting and pasting

Kufer et al. describe a method for assembling biomolecular structures in defined geometric patterns using atomic force microscopy. By taking advantage of the natural ability of DNA to hybridize and by applying different unbinding forces that act on different DNA geometries, they show that target molecules coupled to DNA oligomers can be picked from one area on a surface with an AFM tip, moved and deposited in a new location.

Kufer, S.K. et al. Science 319, 594–596 (2008).