Problem solving with NMR

Oeiras, 27.05.10

Most protein biochemistry, biophysical and structural studies rely on a supply of pure protein. Routine laboratory methods give a comparative estimate of protein purity but fail to reveal contamination from small organic molecules or carbohydrates. In contrast, even modest concentrations of these molecules are observable with the simplest Nuclear Magnetic Resonance (NMR) experiments. ITQB researchers have developed a useful tool for protein quality control: a diffusion NMR based method that reveals the presence of low concentrations of small molecule contamination hidden below the more abundant protein signals. The work, published in Analytical Biochemistry, involves the researchers and collaborators of the Laboratories of Bacterial Membrane Proteomics and Molecular Interactions and NMR at ITQB.

Diffusion NMR protocols are being used by the Molecular Interactions and NMR to solve other problems in biology. While the two-stranded DNA structure published by Watson and Crick provides one of sciences best emblematic images, other DNA structures are relatively unknown and poorly understood. Four-stranded DNA was regarded as a curiosity for many years until it was shown to occur inside our cells, where it can play an important role in genetic events involving cancer. Unraveling the structure and fold of a piece of DNA is not easy but a diffusion NMR protocol helped to solve this problem (published in Chemistry – a European Journal). Next, researchers will use this method to look for small molecule inhibitors or stabilizers of quadruplex DNA structures in what may be thought of as an initial screen for potential drugs against the cancer processes involving these structures.

Noteworthy, although the research work was carried out at CERMAX (ITQB), which hosts the strongest magnetic field in the Portuguese NMR network, the diffusion NMR methods used in the studies are suitable for smaller NMR instruments and therefore available for other researchers in the network.

Original Articles

Anal. Biochem. 2010, 396, 117-123

Diffusion nuclear magnetic resonance spectroscopy detects substoichiometric concentrations of small molecules in protein samples

J.P. Ribeiro, M. Palczewska, S. André, F.J. Cañada, H-J. Gabius, J. Jiménez-Barbero, B. Mellström, J.R. Naranjo, D.J. Scheffers, P. Groves

Chem. Eur. J. 2010, ahead of press

Rapid Stoichiometric Analysis of G-Quadruplexes in Solution

P. Groves, M. Webba da Silva