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Recently, Santos et al. published an article titled “Chirality-Induced Electron Spin Polarization and Enantiospecific Response in Solid-State Cross-Polarization Nuclear Magnetic Resonance” in ACS Nano. In this article it was claimed that crystalline amino acid enantiomers can give rise to 1H-15N and 1H-13C cross-polarization magic angle spinning (CPMAS) solid-state NMR spectra with different relative signal intensities. The authors attributed such differences to transient changes in T1 relaxation times resulting from an interaction between the electron spins and the radiofrequency contact pulses used in the CPMAS experiment, and discussed this proposed phenomenon in terms of the chirality-induced spin selectivity (CISS) effect. We disagree with the authors conclusion that the CISS effect plays a role in the different signal intensities observed in the CPMAS solid-state NMR spectra of crystalline enantiomers. Quantitative 13C CPMAS experiments on aspartic acid enantiomers demonstrate that CPMAS signal variations can likely be attributed to sample dependent differences in T1 relaxation times rather than any chirality effects.
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Incorporating the BEST methodology in experiments for measuring paramagnetic relaxation enhancements
Band-selective excitation short-transient (BEST) sequences are widely used for protein NMR experiments that start with amide proton magnetization, such as 1H-15N HSQC, 1H-15N TROSY, and multidimensional backbone assignment experi- ments, because the optimization of amide proton longitudinal relaxation afforded by the BEST methodology allows for much greater sensitivity when using short scan times. Here we show that the BEST methodology can be easily incorpo- rated in sequences for measuring proton transverse relaxation rates (1H R2), which are typically used to determine para- magnetic relaxation enhancements (PREs). The resulting BEST-HSQC-PRE and BEST-TROSY-PRE experiments afford similar or better sensitivity for measuring PREs compared to previous methods, provide equally accurate measurements of transverse relaxation rates (and therefore PREs), and allow shorter scan times to be used.
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- PAR ID:
- 10666099
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Journal of Biomolecular NMR
- Volume:
- 80
- Issue:
- 1
- ISSN:
- 0925-2738
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1007/s10858-025-00485-8
