Imaging and visualization

Signal amplification in molecular imaging by pretargeting a multivalent, bispecific antibody

Radiolabeled antibodies are a useful tool for in vivo imaging of tumors. Sharkey et al. show that by injecting mice first with bispecific antibodies that target a particular tumor antigen, then with radioisotope conjugated to a hapten recognized by the same antibodies, one can target and image tumors more rapidly and with greater specificity than with directly radiolabeled antibodies.

Sharkey, R.M. et al. Nat. Med. 11, 1250–1255 (2005).

Stem cells

Isolating gene-corrected stem cells without drug selection

Positive-negative drug selection is the preferred strategy for isolating gene-targeted stem cells. This method, however, can take too long for the maintenance of some stem cell types. Using fluorescent protein genes instead of drug resistance markers for their targeting construct, Hatada et al. demonstrate a more rapid, fluorescence-activated cell sorting (FACS)-based positive-negative strategy to isolate targeted cells.

Hatada, S. et al. Proc. Natl. Acad. Sci. USA 102, 16357–16361 (2005).

Molecular libraries

Cell-specific targeting of nanoparticles by multivalent attachment of small molecules

Designing molecules that specifically target only certain cell types is a delicate craft; Weissleder et al. present a high-throughput, nanoparticle-based assay for characterizing the interactions of a wide variety of functional groups with cells of different types or activation states. The resulting data can be used to dramatically improve the design of highly specialized, targeted compounds.

Weissleder, R. et al. Nat. Biotechnol. 23, 1418–1423 (2005).

Proteomics

Metalloproteomics: high-throughput structural and functional annotation of proteins in structural genomics

An estimated 15–25% of the proteins in the protein data bank are coordinated with at least one metal atom. Chance et al., working in conjunction with the New York Structural GenomiX Research Consortium, have developed a high-throughput, X-ray absorption spectroscopy–based approach for identifying and characterizing such metalloproteins with ∼95% accuracy.

Shi, W. et al. Structure (Camb.) 13, 1473–1486 (2005).

Cell biology

Marker-specific sorting of rare cells using dielectrophoresis

Fluorescence-activated cell sorting (FACS) is widely recognized as a useful tool for sorting even very rare populations of cells from a heterogeneous mixture. The throughput of FACS, however, is relatively low, and so Hu et al. demonstrate 'DACS', a higher-throughput alternative wherein cells tagged with antibody-conjugated polymeric beads are sorted by dielectrophoresis.

Hu, X. et al. Proc. Natl. Acad. Sci. USA 102, 15757–15761 (2005).