Abstract: Fluorescent stains are described, which enable imaging of cellular structures without the need for genetic manipulation. Unique diaminobenzopyrylium dyes are disclosed, together with their use as live-cell mitochondrial stains.

Abstract: A generic biosensor strategy was developed for the construction of switchable antibody reporter enzymes that allow direct detection of antibodies in solution including serum. The biosensor principle is based on the antibody-induced disruption of the intramolecular interaction between a reporter enzyme and its inhibitor and takes advantage of a unique structural property shared by all antibody classes, the presence of two identical antigen binding sites separated by a distance of approximately 100 ?. Unlike previous strategies, this biosensor design is intrinsically modular, allowing the construction of e.g. ?-lactamase reporter enzymes for in principle any target antibody without cumbersome optimization/screening procedures. General guidelines are provided for the construction of reporter enzymes using enzyme-inhibitor pairs.