TY - JOUR

T1 - Simultaneous 15N polarization of several biocompatible substrates in ethanol–water mixtures by signal amplification by reversible exchange (SABRE) method

AU - Kiryutin, Alexey S.

AU - Yurkovskaya, Alexandra V.

AU - Petrov, Pavel A.

AU - Ivanov, Konstantin L.

N1 - Funding Information: This work has been supported by the Russian Science Foundation (Grant No. 20‐62‐47038). We acknowledge the Russian Ministry of Science and Higher Education for giving access to NMR facilities. Funding Information: This work has been supported by the Russian Science Foundation (Grant No. 20-62-47038). We acknowledge the Russian Ministry of Science and Higher Education for giving access to NMR facilities. Our valued colleague and good friend Konstantin (?Kostya?) L. Ivanov became one of the first victims of the COVID-19 pandemic in our community. He passed away on March 5, 2021, in a hospital in Novosibirsk. We will miss Kostya very much as an extraordinary person: he was a creative but extremely thorough scientist, a generous and attentive friend, and a considerate and eminently civilized colleague. He was a great citizen of the scientific community. In addition to his demanding work as director of the International Tomography Center (ITC) of the Siberian Branch of the Russian Academy of Sciences, he kept his research at a high level and organized a variety of meetings, seminars, and webinars. We shall also miss Kostya as one of the leading figures of the ?Intercontinental NMR Seminar Series? (ICONS, now appropriately named after him). Kostya developed the theory of coherent polarization transfer in SABRE based on level anticrossing concept, for which he was awarded Laukien Prize together with Simon Duckett and Warren Warren in 2020. Publisher Copyright: © 2021 John Wiley & Sons, Ltd.

PY - 2021/12

Y1 - 2021/12

N2 - Signal amplification by reversible exchange (SABRE) is a popular method for generating strong signal enhancements in nuclear magnetic resonance (NMR). In SABRE experiments, the source of polarization is provided by the nonthermal spin order of parahydrogen (pH2, the H2 molecule in its nuclear singlet spin state). Polarization formation requires that both pH2 and a substrate molecule bind to an Ir-based complex where polarization transfer occurs. Subsequently, the complex dissociates and free polarized substrate molecules are formed. In this work, we present approaches towards biocompatible SABRE, meaning that several small biomolecules are simultaneously polarized by using the SABRE method in water–ethanol solutions at room temperature. We are able to demonstrate significant 15N-NMR signal enhancements in water–ethanol solutions for biomolecules like nicotinamide, metronidazole, adenosine-5′-monophosphate, and 4-methylimidazole and found that the first three substrates are polarized at the same level as a well-known pyridine. We show that simultaneous polarization of several molecules is indeed feasible when the reactions are carried out at an ultralow field of about 400–500 nT. The achieved enhancements are between 100-fold and 15,000-fold. The resulting 15N polarization (maximal value about 4% achieved for metronidazole and pyridine at 45°C) strongly depends on the sample temperature, pH2 bubbling pressure, and pH2 flow. One more parameter, which is important for optimizing the enhancement, is the solvent pH. Hence, this study presents a step in developing biocompatible SABRE polarization and gives a clue on how such SABRE experiments should be optimized to achieve the highest NMR signal enhancement.

AB - Signal amplification by reversible exchange (SABRE) is a popular method for generating strong signal enhancements in nuclear magnetic resonance (NMR). In SABRE experiments, the source of polarization is provided by the nonthermal spin order of parahydrogen (pH2, the H2 molecule in its nuclear singlet spin state). Polarization formation requires that both pH2 and a substrate molecule bind to an Ir-based complex where polarization transfer occurs. Subsequently, the complex dissociates and free polarized substrate molecules are formed. In this work, we present approaches towards biocompatible SABRE, meaning that several small biomolecules are simultaneously polarized by using the SABRE method in water–ethanol solutions at room temperature. We are able to demonstrate significant 15N-NMR signal enhancements in water–ethanol solutions for biomolecules like nicotinamide, metronidazole, adenosine-5′-monophosphate, and 4-methylimidazole and found that the first three substrates are polarized at the same level as a well-known pyridine. We show that simultaneous polarization of several molecules is indeed feasible when the reactions are carried out at an ultralow field of about 400–500 nT. The achieved enhancements are between 100-fold and 15,000-fold. The resulting 15N polarization (maximal value about 4% achieved for metronidazole and pyridine at 45°C) strongly depends on the sample temperature, pH2 bubbling pressure, and pH2 flow. One more parameter, which is important for optimizing the enhancement, is the solvent pH. Hence, this study presents a step in developing biocompatible SABRE polarization and gives a clue on how such SABRE experiments should be optimized to achieve the highest NMR signal enhancement.

KW - biomolecules

KW - parahydrogen

KW - polarization transfer

KW - SABRE

KW - spin hyperpolarization

UR - http://www.scopus.com/inward/record.url?scp=85107727214&partnerID=8YFLogxK

U2 - 10.1002/mrc.5184

DO - 10.1002/mrc.5184

M3 - Article

C2 - 34085303

AN - SCOPUS:85107727214

VL - 59

SP - 1216

EP - 1224

JO - Magnetic Resonance in Chemistry

JF - Magnetic Resonance in Chemistry

SN - 0749-1581

IS - 12

ER -