Annemieke Madder, from Ghent University, and colleagues are one step closer to a new measles vaccine, which they say may be suitable for very young infants among the most at risk from the disease. Their paper reports the design, synthesis and biochemical evaluation of a cyclic bile acid-peptide conjugate as a mimic of the loop-like structure of the measles virus haemagglutinin noose epitope. The work is illustrated on the outside front cover. 

Martin Lear, at the National University of Singapore, and colleagues have developed a convenient way to sort cells and label proteins by reducing disulfides within antibodies and cysteine-based fluorescent tagging with a readily made, water-soluble maleimide reagent. Their work is illustrated on the inside front cover. 

Site specific protein labeling plays a key role in elucidating the function of the proteins at the molecular level by revealing their locations in the cell, their interaction networks with other cellular components and the dynamic mechanisms of their bio-generation, trafficking and degradation in response to regulatory signals in a biological system. Murat Sunbul and Jun Yin at the University of Chicago, US, survey a number of protein labeling methods based on the application of protein posttranslational modification enzymes in this issue's Perspective.