Dynamic nuclear polarization study of UV-irradiated butanol for hyperpolarized liquid NMR

We have carried out a dynamic nuclear polarization (DNP) study of proton spins of UV-irradiated solid butanol containing phenol at 0.1-1%. By the aid of butyl free radicals produced by the photolysis, the butanol sample was dynamically polarized up to the polarization of 1.4+/-0.1% at 1.5 K and 1.2 T, which is about 4000 times larger than that at the thermal equilibrium at an ambient temperature. Unlike persistent free radicals such as nitroxy and trityl free radicals commonly used for DNP, the butyl free radicals immediately decay by melting. We propose that free radicals produced by UV-photolysis are applicable to the DNP-enhanced hyperpolarized liquid-state NMR (Ardenkjaer-Larsen et al. [6]). The hyperpolarization of the UV-irradiated samples should remain longer than that of the samples having persistent free radicals, because of the absence of the free radicals after the melting in the UV-irradiated samples.

Radiation-induced binding of methanol, ethanol and 1-butanol to haemoglobin

Aqueous solutions of haemoglobin were irradiated under N2 and under N2O in the presence of methanol, ethanol and 1-butanol, which were partly 14C-labelled. The amount of bound alcohol was measured after gel filtration on Sephadex G-100 and with sodium dodecyl sulphate on Sepharose 6B-CL. All alcohols became covalently linked to haemoglobin. After radiolysis under N2 the G values for the three different alcohols were very similar, but under N2O the yield of cross-linking of haemoglobin with 1-butanol is twice that of methanol or ethanol. The high degree of modification by butanol results in extensive dissociation to dimers. Possible mechanisms yielding covalent cross-links between alcohols and haemoglobin are discussed. The high G value for cross-linking with butanol suggests that butanol radicals can add very efficiently to double bonds.