Numerical simulation of DNP
Dynamic Nuclear Polarization (DNP) is a technique to improve the sensitivity of NMR by transferring polarization of electron spin to nuclear spin. Since the polarizability of electrons in the equilibrium state is about 660 times the polarizability of 1H, theoretically it is expected that nuclear magnetization can be increased up to 660 times for 1H if it can all be transferred. It is possible to improve the analytical ability of NMR by greatly adding magnetization-increasing effect by DNP… However, in practice, it is necessary to increase the nuclear magnetization under than several dozen K temperature high magnetic field magic angle spinning condition, even if trying to increase such nuclear magnetization in such a way it does not go well. Why is that?
This is because small effects, which we ignore when thinking about the rough physical theory of DNP, interfere with the nuclear magnetization. The main magnetization improvement path generated when measuring a solid sample in a high magnetic field is called a cross effect which occurs between two unpaired electrons and one nuclear. Maybe you can easily predict that efficiency will be good if you use a substance that has two unpaired electrons in one molecule (biradical). However, actually using biradical experiments, the DNP efficiency varies considerably depending on the shape of the biradical molecule and the distance between the radicals in the molecule. It also varies considerably depending on the concentration of biradical. Since radicals interfere with NMR observations due to their strong magnetization while improving nuclear magnetization, if it is too much it is rather bad.
Numerical calculation of DNP efficiency is one means to solve this problem. In the past, to find better DNP conditions, we had to make various biradical molecules and measure with different concentration, temperature, MAS rotation speed, magnetic field intensity actually, but the numerical calculation of DNP efficiency can be obtained without actual measuring. Then, what was the reason why the measurement method so far did not work, and what can be done to solve the problem, are understood. In addition, what kind of biradical substances should be good to synthesize will be able to conjecture.
Because these studies is mainly performed using a super computer, research is mainly performed on a personal computer. Our center’s name is “Institute for Protein Research”, but there are also research fields that are rarely related to such organisms.