By incorporating on-chip multiplication gain, the electron multiplying CCD achieves, in an all solid-state sensor, the single-photon detection sensitivity typical of intensified or electron-bombarded CCDs at much lower cost and without compromising the quantum efficiency and resolution characteristics of the conventional CCD structure.
The group of proteins known as histones were discovered in the 1880s by Albrecht Kossel, a German doctor who later won the Nobel Prize in physiology for his work in cell biology. For many years after they were initially identified, histones were widely believed to primarily play a supportive role, acting as a type of packing material around which DNA was wound. In the 1990s, however, a more complex picture of histone activity began to materialize, and today the proteins are generally thought to serve an important regulatory function within cells. The digital video sequences presented in this section feature HeLa cells labeled for H2B histones with the fluorescent probe mCherry and for C-Src with mEmerald.