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dc.contributor.authorNovoa Carballal, Ramón
dc.contributor.authorMartin-Pastor, Manuel
dc.contributor.authorFernandez-Megia, Eduardo
dc.identifier.citationACS Macro Lett. 2021, 10, 1474−1479.
dc.description.abstractThe observation of signals in solution NMR requires nuclei with sufficiently large transverse relaxation times (T2). Otherwise, broad signals embedded in the baseline afford an invisible fraction of nuclei (IF). Based on the STD (saturation transfer difference) sequence, IF-STD is presented as a quick tool to unveil IF in the 1H NMR spectra of polymers. The saturation of a polymer in a region of the NMR spectrum with IF (very short 1H T2) results in an efficient propagation of the magnetization by spin diffusion through the network of protons to a visible–invisible interphase with larger 1H T2 (STDon). Subtracting this spectrum from one recorded without saturation (STDoff) produces a difference spectrum (STDoff-on), with the nuclei at the visible–invisible interphase, that confirms the presence of an IF. Analysis of a wide collection of polymers by IF-STD reveals IF more common than previously thought, with relevant IF figures when STD > 0.4% at 750 MHz. A fundamental property of the IF-STD experiment is that the signal is generated within a single state comprising polymer domains with different dynamics, as opposed to several states in exchange with different degrees of aggregation. Contrary to a reductionist visible–invisible dichotomy, our results confirm a continuous distribution of nuclei with diverse dynamics. Since nuclei observed (edited) by IF-STD at the visible–invisible interphase are in close spatial proximity to the IF (tunable with the saturation time), they emerge as a privileged platform from which gaining an insight into the IF itself
dc.description.sponsorshipThis work was supported by the Spanish Ministry of Science and Innovation (RTI2018-102212-B-I00), the Xunta de Galicia (ED431C 2018/30, and Centro singular de investigación de Galicia accreditation 2019–2022, ED431G2019/03), Axencia Galega de Innovación (IN845D 2020/09), and the European Union (European Regional Development Fund-ERDF)
dc.publisherACS Publications
dc.relationinfo:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/RTI2018-102212-B-I00/ES/ENSAMBLAJE JERARQUICO DE COMPLEJOS POLIIONICOS DENDRITICOS COMO PROTOCELULAS Y BIOREACTORES
dc.rights© 2021 American Chemical Society. This work is licenced under a Creative Commons Attribution 4.0 International licence (
dc.subjectMagnetic properties
dc.subjectQuantum mechanics
dc.titleUnveiling an NMR-invisible fraction of polymers in solution by saturation transfer difference
dc.contributor.affiliationUniversidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares
dc.contributor.affiliationUniversidade de Santiago de Compostela. Departamento de Química Orgánica

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© 2021 American Chemical Society. This work is licenced under a Creative Commons Attribution 4.0 International licence (
Except where otherwise noted, this item's license is described as  © 2021 American Chemical Society. This work is licenced under a Creative Commons Attribution 4.0 International licence (

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