Scientists use superpolarization of water to greatly improve the performance and possibilities of biomolecular studies combined with nuclear magnetic resonance
Nuclear Magnetic Resonance (NMR) is an imaging and spectroscopy tool that allows scientists, among other things, to study the structure of molecules and their dynamics at atomic resolution. One of the difficulties that this tool poses to scientists is the weakness of its signals. Prof. Lucio Friedman and the members of his research group at the Weizmann Institute of Science, developed an NMR method for studying biological molecules with high sensitivity that makes it possible to identify and map changes in the organization of these molecules with a significantly higher sensitivity than is normally obtained. The researchers hope that this development, which relies among other things on a grant from the National Science Foundation, will promote research in various biological molecules, including RNA and proteins.
Magnetic resonance imaging (MRI), a tool found in every hospital, is actually a specific type of NMR. The very weak magnetic interactions that MRI exerts on the nuclei of the atoms in the sample, allow it to perform non-invasive tests based on the water in the tissues. But those properties require giving up the sensitivity required for imaging and characterization of biological molecules that are present in much lower concentrations.
Prof. Friedman says that it is possible to increase the sensitivity of the system, by means of super-polarization which significantly increases the number of spins of the atomic nuclei that line up under the influence of the magnetic fields in the sample being tested (spin is a spin attack that exists in the particles. There are two directions of spin, commonly called "up" and down". Super-polarization means a significant increase in the rate of one of these states compared to the other). However, nuclear superpolarization usually requires cooling to very low temperatures that are not suitable for working with biological molecules such as DNA, RNA or proteins. The situation becomes even more complex and difficult, when scientists seek to study these molecules under natural and physiological conditions.
Prof. Friedman and the members of his group tackled this problem by applying superpolarization of the hydrogen nuclei in water molecules at a temperature close to absolute zero - and then suddenly spraying these "superwater" molecules on biological molecules under physiological conditions. To do this, the polarized (and frozen) water must be melted at once and flowed, at a pressure of several atmospheres, to the studied molecules that are placed in the NMR system under physiological conditions.
At this stage, the hydrogen atoms in the water exchange (spontaneously) with their counterparts found in the biological molecules - while quickly jumping between the oxygen atoms of the water and the nitrogen atoms in the biological molecules being studied. Thus, when a biological molecule receives a polarized nucleus from water, it emits an amplified signal, the intensity of which is several hundreds, and sometimes thousands of times stronger than a normal NMR reaction.
Prof. Friedman, research student Mihalo Novkovic and post-doctoral researcher Dr. Gregory Olsen, "photographed" at a rate of about three pictures per second the dynamics of riboswitch molecules, which are a kind of messenger RNA pieces that quickly move from one state to another when they are activated What is the question? How is it possible to increase the sensitivity of nuclear magnetic resonance systems, and use them to study biological molecules under physiological conditions?
"The most important thing we learned is not to touch the water from the moment the sample was injected," says Prof. Friedman. "The water serves as a kind of bank of super-polarized nuclei for the biological molecules, and the cold shower allows us to study them with high sensitivity for a minute or two using NMR."
The researchers used two NMR systems, one, which was operated at extremely low temperatures and which was used to super-polarize the water, and the other - in which RNA molecules were kept under physiological conditions. The planning of the experiment and the preparation of the samples were carried out in collaboration with the research group of Prof. Harald Schwalbe at the Goethe University in Frankfurt.
In order to experimentally examine the exchange of hydrogen atoms between proteins and their aqueous environment, Prof. Friedman teamed up with Dr. Rina Rosenzweig and her staff at the Weizmann Institute. Dr. Rosenzweig studies protein folding, including auxiliary proteins that help other proteins to fold.
Dr. Or Skelly - who was previously a research student in Prof. Friedman's lab and then a post-doctoral researcher in Dr. Rosenzweig's lab - together with Mihalo Novkovic and Dr. Gregory Olsen, used this method in experiments on four proteins, each of which was characterized by a pattern Different folding. The first protein was well folded, while the second was completely unfolded. The other two proteins continuously switched between a folded and unfolded state, with the scientists controlling the rate of transition using the temperature in the sample. In one of these dynamic proteins, the transitions occurred relatively slowly, about once per second, while in the other protein, the fourth in number, the transitions occurred at a rate of 20 to 30 times per second.
The most important thing we learned is not to touch the water from the moment it is injected, for example the water serves as a kind of bank of superpolarized nuclei for the biological molecules
Prof. Lucio Friedman
In the first three proteins, the results were as expected: in NMR, more amplified signals were picked up from the unfolded proteins, compared to the folded proteins (or regions). But in the fourth protein, where the transitions occurred quickly, the signal increased - three times or more - precisely in the folded parts of the protein compared to the unfolded parts.
"We repeated the experiments over and over again for several months to make sure we weren't wrong," says Prof. Friedman, but the results remain unchanged. The scientists have proposed several theoretical explanations for the surprising findings, and they are planning further experiments to determine which of the explanations is correct.
Life itself:
Prof. Lucio Friedman immigrated to Israel with his family at the age of 35, and on weekends he enjoys participating in long-distance triathlons.
For the article on the Voice of Science website
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DOGMA RNA mutation makers in water just for money shame on you