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Updated: May 3, 2026

Thermodynamics of Membrane Protein Folding Measured by Fluorescence Spectroscopy
Published on: April 28, 2011
Free energy diagrams for protein function
Ruth Nussinov1, Chung-Jung Tsai2
1Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
Abstract:
Simplified representations can be powerful. Two common examples are sequence logos and ribbon diagrams. Both have been extraordinarily successful in capturing complex static features of sequences and structures. Capturing function is challenging, since activation involves triggered dynamic shifts between ON and OFF states. Here, we show that simple funnel drawings can capture and usefully portray proteins by their cellular triggering mechanism. The funnel shape around the proteins' native states can describe mechanisms of upstream signal integration and downstream response. "Function diagrams" are important: they can combine diverse biochemical data to visually distinguish among activation (or recruitment) mechanisms and tag proteins in cellular networks, clarifying their mechanism at a glance. We create templates for function classification and suggest that they can extend signaling pathway maps. Of note, the diagrams describe free energy landscapes; thus, they can be quantified. We name our dynamic free-energy diagrams dFEDs.
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