Viewing the dynamics of biomolecules through the eyes of reporter spin labels
Magnetic resonance (mostly familiar as MRI) is one the most powerful experimental techniques with which the motions of biological molecules can be probed in atomic detail. As the name suggests, magnetic resonance is based on the interaction of the tiny magnets present in electrons and atomic nuclei (known as the spin of these particles) with the magnetic field applied in the laboratory. Because the interaction of the electron spin with the magnetic field is almost one thousand times stronger than the interaction of nuclear spins, electron spin resonance (ESR) is a much more sensitive experimental technique than nuclear magnetic resonance (NMR). However, whereas biological molecules naturally contain nuclear spins ready to interact with us, they typically lack such electron spins. Therefore, in ESR one usually has to chemically attach a small spin label to the biomolecule of interest.
In this talk I will present some of the ways in which the information from spin label reporters can be used to understand the dynamics of biological molecules. In particular, I will discuss three different examples: a DNA fragment with a mismatch in one of its base pairs, a protein whose backbone flexibility helps it bind small hydrophobic molecules, and waters that should be in the hydrophobic interior of lipid bilayers. I will argue that in all the three cases atomistic molecular dynamics simulations are necessary to go beyond anecdotal interpretation of the processes reported by the magnetic resonance experiments.
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