RESUMEN
Spherical nanoparticles and fibres observable by cryo-electron microscopy are spontaneously formed by the Finland trityl radical at concentrations above 15 mM. These species represent a new class of paramagnetic, metal-free, nanoscale supramolecular materials. Self-association was observed under a variety of experimental conditions, including aqueous solution at room temperature, low temperature frozen glasses and the gas phase. Oligomers formed by at least 5 Finland radicals were detected by ion-mobility mass spectrometry. Magnetic susceptibility data as well as low temperature EPR spectra show coupling between electronic spins in the self-assembled species. Quantum chemical calculations show stacking along the C3 symmetry axis. Nanoparticle formation requires additional lateral packing that can be provided by hydrogen bonding involving the triangular array of carboxylic acid groups leading to the assembly of geodesic spheres.
RESUMEN
A new class of guest-induced, bi-radical self-assembled organic capsules is reported. They are formed by the inclusion of a tetramethylammonium (TMA) cation between two monomers of the stable trityl radical OX63. OX63 is extensively used in dissolution dynamic nuclear polarization (DNP) where it leads to NMR sensitivity enhancements of several orders of magnitude. The supramolecular properties of OX63 have a strong impact on its DNP properties. An especially relevant case is the polarization of choline-containing metabolites, where complex formation between choline and OX63 results in faster relaxation.
Asunto(s)
Cápsulas/química , Indenos/química , Compuestos de Tritilo/química , Dimerización , Espectroscopía de Resonancia por Spin del Electrón , Espectroscopía de Resonancia Magnética , Compuestos de Amonio Cuaternario/química , TemperaturaRESUMEN
Long-lived states (LLS) are relaxation-favored spin population distributions of J-coupled magnetic nuclei. LLS were measured, along with classical (1)H and (15)N relaxation rate constants, in amino acids of the N-terminal Unique domain of the c-Src kinase, which is disordered in vitro under physiological conditions. The relaxation rates of LLS can probe motions and interactions in biomolecules. LLS of the aliphatic protons of glycines, with lifetimes approximately four times longer than their spin-lattice relaxation times, are reported for the first time in an intrinsically disordered protein domain. LLS relaxation experiments were integrated with 2D spectroscopy methods, further adapting them for studies on proteins.
Asunto(s)
Glicina/química , Proteínas Intrínsecamente Desordenadas/química , Protones , Familia-src Quinasas/química , Proteína Tirosina Quinasa CSK , Humanos , Isótopos de Nitrógeno , Resonancia Magnética Nuclear Biomolecular , Estructura Terciaria de Proteína , Factores de TiempoRESUMEN
Herein, we report the synthesis and the study of a novel mixed biradical with BDPA and TEMPO radical units that are covalently bound by an ester group (BDPAesterTEMPO) as a polarizing agent for fast dissolution DNP. The biradical exhibits an extremely high DNP NMR enhancement of >50 000 times, which constitutes one of the largest signal enhancements observed so far, to the best of our knowledge.