Single molecule fluorescence spectroscopy: a tool for protein studies approaching cellular environmental conditions

Due to their high sensitivity and specificity fluorescence based single molecule techniques offer the possibility to study individual molecules (e.g., proteins or protein complexes) in situ in their cellular context. Recent progress in instrumentation and in sample preparation provides an increasingly better accessibility to more complex molecular assemblies. These assemblies mimic the natural cellular environmental conditions and at the same time allow sophisticated studies on proteins of interest. This review gives a brief introduction to single molecule fluorescence techniques and presents some selected applications on protein folding and on complex formation of membrane proteins.