Protein biochemistry

Experimental generation of electrostatic potential maps

Red, white and blue electrostatic potential maps are often computationally generated for protein structures to assess the roles of electrostatics in various protein functions. Suydam et al. now demonstrate that these maps can be experimentally generated for the active site of human aldose reductase, by mapping the effects of the local electrical field on a nitrile-based inhibitor using vibrational spectroscopy.

Suydam, I.T. et al. Science 313, 200–204 (2006).

Molecular libraries

Improving the display of proteins on phage

Phage display is a powerful tool for the high-throughput screening of proteins for desired properties. Unfortunately, many proteins display poorly on phage despite attempts to address the problem. Steiner et al. have vastly improved the range of proteins amenable to phage display by using signal sequences that harness the signal-recognition particle translocation pathway rather than the traditional Sec-dependent translocation pathway.

Steiner, D. et al. Nat. Biotec. 24, 823–831 (2006).

Gene transfer

On-target gene delivery with lentiviral vectors

Lentiviral vectors have shown great potential as in vivo gene delivery vehicles, but assuring on-target delivery is very difficult. Yang et al. now show that efficient delivery of the vector to specific cell types is possible by separating the functions of target recognition and membrane fusion into two unique moieties on the lentiviral surface—an antibody and a pH-responsive fusogenic envelope glycoprotein.

Yang, L. et al. Proc. Natl. Acad. Sci. USA 103, 11479–11484 (2006).

Chemical tools

Fluorescent dyes for live-cell imaging of RNA

By using combinatorial organic synthesis to generate a large fluorescent styryl dye library, Li et al. discovered three RNA-selective probes that can be used for the live-cell imaging of RNA distribution within the nucleus. These three dyes exhibited higher selectivity, photostability and lower cytotoxicity compared with a commercially available alternative.

Li, Q. et al. Chem. Biol. 13, 615–623 (2006)

Spectroscopy

Probing membrane protein orientation with EPR spectroscopy

Inbaraj et al. report a new technique for determining integral membrane protein topology in bicelles by electron paramagnetic resonance (EPR) spectroscopy. Using the nicotinic acetylcholine receptor as an example, they show that the incorporation of a nitroxide spin probe facilitates measurement of hyperfine splittings, which are used to accurately calculate the helical tilt of the transmembrane domain.

Inbaraj, J.J. et al. J. Am. Chem. Soc. 128, 9549–9554 (2006).