Cover Picture: Quantum Dots Protected with Tiopronin: A New Fluorescence System for Cell-Biology Studies (ChemBioChem 6/2005)

The cover picture shows the synthesis scheme for water‐soluble CdS nanocrystals that are protected with tiopronin, by using a straightforward and economical methodology. The chemical functionality of this capping agent provides a very high stability for the nanocrystals and has allowed us to functionalize quantum dots (QDs) with a HIV‐1 Tat protein‐derived peptide sequence. These nanocrystals are biocompatible with hTERT‐BJ1 human fibroblasts. Also shown is an overlay of the fluorescence (green; bottom left) and phase contrast images of hTERT‐BJ1 human fibroblasts incubated with CdS@tiopronin‐Tat. The functionalization of QDs with the translocation peptide permits them to penetrate the cell membrane and target the nucleus. Detailed information about the synthesis, functionalization and biocompatibility of these nanomaterials is reported by J. M. de la Fuente et al. on p. 989 ff.