Unravelling structural heterogeneity in proteins using ultrafast conformation-specific VIPER spectroscopy

• Applicant: Dr.-Ing. Luuk van Wilderen
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 466145756

Proteins are small molecular machines in living systems. Depending on changes in their environment they can perform different tasks such as transmitting a biochemical signal. Often, multiple nearly identical protein substructures or conformers coexist naturally in cells or organisms, i.e. the proteins are said to be structurally heterogeneous. Even if the protein structures perceive the same input like a change in pH or a flash of light, and they look similar, such substructures may still produce a different signal or even no signal at all. Investigating these substructures using conventional biochemical separation methods usually fails, because the structural differences are often small. For example, they can consist of the presence or absence of a single hydrogen bond in a protein having thousands of bonds, and/or because the substructures are interconverting too quickly. In the presence of suitable vibronic couplings, it is possible to activate only one of the substructures by infrared light via the VIPER spectroscopic method, even if they coexist in presence of the other structures. The other substructures remain inactive. VIPER consists of a sequence of three ultrafast laser pulses that are all tunable in colour and relative timing. The structural sensitivity of this method is given by making use of infrared laser light, allowing for instance to discern individual conformations having different hydrogen bond properties. Because standard spectroscopic methods will also activate multiple structures at the same time, the resulting spectra will contain a complex superposition of spectral signals or features and timescales of either structure. With VIPER the resulting spectra are less complex and easier to interpret, because a single population is selected that follows less or possibly even a single biochemical pathway within a network of pathways. Besides investigating conformational heterogeneity in proteins and understanding in which way the structure determines which pathway to take, the gained insight may potentially lead to the development of more selective (molecular and cellular) imaging labels, novel bio-photonic devices, and enhanced control of cellular processes by light.

• DFG Programme: Research Grants