Site-directed spin labeling of 2′-amino groups in RNA with isoindoline nitroxides that are resistant to reduction

Post-print (lokagerð höfundar)Two aromatic isothiocyanates, derived from isoindoline nitroxides, were synthesized and selectively reacted with 2′-amino groups in RNA. The spin labels displayed limited mobility in RNA, making them promising candidates for distance measurements by pulsed EPR. After conjugation to RNA, a tetraethyl isoindoline derivative showed significant stability under reducing conditions.This work was supported by the Icelandic Research Fund (141062-051). S.S. and A.P.J. gratefully acknowledge doctoral fellowships provided by the University of Iceland. The authors thank Dr S. Jonsdottir for assistance with collecting analytical data for structural characterization of compounds prepared and members of the Sigurdsson research group for critical reading of the manuscript.Peer reviewe

bcTol: a highly water-soluble biradical for efficient dynamic nuclear polarization of biomolecules

Post-print (lokagerð höfundar)Dynamic nuclear polarization (DNP) is an efficient method to overcome the inherent low sensitivity of magic-angle spinning (MAS) solid-state NMR. We report a new polarizing agent (bcTol), designed for biological applications, that yielded an enhancement value of 244 in a microcrystalline SH3 domain sample at 110 K.This work was financially supported by the Icelandic Research Fund (141062051), the Deutsche Forschungsgemeinschaft (SFB 1078, 740 and 765) and by a doctoral fellowship to A. P. J. from the University of Icelandic Research Fund. We thank A. Diehl, K. Rehbein, N. Erdmann and D. Michl for the preparation of microcrystalline SH3 and channelrhodopsin samples, Dr S. Jonsdottir for assistance in collecting analytical data for structural characterization of the radicals, as well as P. Hegemann and K. Stehfest for helpful discussions concerning expression and purification of channelrhodopsin.Peer reviewe

Dynamic Real-Time Magnetic Resonance at Very Low Magnetic Fields

The phenomenon of nuclear magnetic resonance (NMR) is widely applied in biomedical and biological science to study structures and dynamics of proteins and their reactions. Despite its impact, NMR is an inherently insensitive phenomenon and has driven the field to construct spectrometers with increasingly higher magnetic fields leading to more detection sensitivity. Here, we are demonstrating that enzymatic reactions can be followed in real-time at millitesla fields, 1000-fold lower than state-of-the-art spectrometers. This requires signal-enhancing samples via hyperpolarization. Within seconds, we have enhanced the signals of 2- 13Cpyruvate, an important metabolite to probe cancer metabolism, in 22 mM concentrations (up to 10.1%±0.1% polarization) and show that such a large signal allows for the real-time detection of enzymatic conversion of pyruvate to lactate. This development paves the pathways for biological studies in portable and affordable NMR systems with a potential for medical diagnostics. <br /

Nuclear hyperpolarization of (1-¹³C)-pyruvate in aqueous solution by proton-relayed side-Arm hydrogenation

We employ Parahydrogen Induced Polarization with Side-Arm Hydrogenation (PHIP-SAH) to polarize (1-13C)-pyruvate. We introduce a new method called proton-relayed side-Arm hydrogenation (PR-SAH) in which an intermediate proton is used to transfer polarization from the side-Arm to the 13C-labelled site of the pyruvate before hydrolysis. This significantly reduces the cost and effort needed to prepare the precursor for radio-frequency transfer experiments while still maintaining acceptable polarization transfer efficiency. Experimentally we have attained on average 4.33% 13C polarization in an aqueous solution of (1-13C)-pyruvate after about 10 seconds of cleavage and extraction. PR-SAH is a promising pulsed NMR method for hyperpolarizing 13C-labelled metabolites in solution, conducted entirely in high magnetic field.</p

Characterization of V–Mo–W Mixed Oxide Catalyst Surface Species by ⁵¹V Solid-State Dynamic Nuclear Polarization NMR

The investigation of V–Mo–W mixed oxide catalysts by ⁵¹V DNP MAS NMR is reported. It is shown that the ⁵¹V NMR signal from surface near vanadium nuclei was enhanced by a factor of ≈50 by direct polarization transfer from unpaired electrons to ⁵¹V nuclei. The dependency of the DNP enhancement of the samples on different polarizing mixtures is investigated and complemented by EPR studies. V–Mo–W mixed oxide catalysts with different stoichiometry (V₂Mo₈W_0.5O_y, V₂Mo₈W₁O_<i>y</i>, and V₂Mo₈W_1.5O_<i>y</i>) are compared, and a suitable assignment of ⁵¹V signals to different phases that are present near to the catalysts surfaces is given. Finally, the applicability of DNP solid-state NMR for the characterization of V–Mo–W mixed oxide catalysts is discussed in terms of the synthesis conditions (i.e., pH-value)

Proceedings of National Conference on Relevance of Engineering and Science for Environment and Society

This conference proceedings contains articles on the various research ideas of the academic community and practitioners presented at the National Conference on Relevance of Engineering and Science for Environment and Society (R{ES}2 2021). R{ES}2 2021 was organized by Shri Pandurang Pratishthan’s, Karmayogi Engineering College, Shelve, Pandharpur, India on July 25th, 2021. Conference Title: National Conference on Relevance of Engineering and Science for Environment and SocietyConference Acronym: R{ES}2 2021Conference Date: 25 July 2021Conference Location: Online (Virtual Mode)Conference Organizers: Shri Pandurang Pratishthan’s, Karmayogi Engineering College, Shelve, Pandharpur, India