# A Reliable Switched Angle Spinning (SAS) Probe with Gradients (PFG) for Proteins in Solid-State NMR

> **NIH NIH R44** · DOTY SCIENTIFIC, INC. · 2022 · $668,446

## Abstract

A Reliable Switched Angle Spinning (SAS) Probe with Gradients (PFG) for Proteins in Solid-State NMR
Abstract
 Solid-state NMR (ssNMR) biotechnology is emerging as a method of choice for high-resolution
structure determination for integral membrane proteins (IMPs). ssNMR provides a unique platform to
investigate protein dynamics and functional studies of a wide range of biomolecules in their supramolecular
assemblies. While there exists a suite of magic angle spinning (MAS) and oriented sample (OS) solid state
NMR experiments for structural characterization of small- and medium-sized proteins, these methods face
several challenges in larger systems. Central to the challenges are NMR sensitivity and resolution. Fast MAS
and 1H detected experiments improve sensitivity but are limited by sample volume and relatively poor
resolution over small isotropic chemical shift dispersion. Additionally, the efficiency of MAS experiments
depends largely on through-bond and through-space coupling constants, solvent suppression, and coherence
pathways selection during rotor synchronized multi-pulse applications. They also suffer from sensitivity loss
due to local and global motions in proteins. On the other hand, static OS NMR experiments in membrane
proteins improve resolution by measuring anisotropic shifts and heteronuclear dipolar couplings but are limited
to dilute spins and low gamma 15N detection only. It has long been realized that unification of MAS and OS has
the ability to widen the spectroscopic applications to large globular and membrane proteins.
 Switched angle spinning (SAS) probes unify MAS, dynamic angle spinning (DAS) and variable angle
spinning (VAS) techniques in ssNMR, and potentially correlate isotropic and anisotropic shifts/couplings in
more than one Fourier dimension. Such powerful techniques are still far from practical use, because SAS
probes in the past have suffered from the lack of reliability due to hardware failures such as the survival of
multi-channel rf-leads, rf coil performance including B1 field strength and homogeneity, spinning stability, and
lastly rapid reorientation and accurate angle reproducibility. Technical difficulties and engineering challenges
thus far have limited the probe technology to only two frequency channels.
 This proposal seeks Phase-II funding for the continued development of a reliable switched angle
spinning probe devoid of previously encountered hardware related issues and compatible with high power
pulsed-field gradients. The Phase-I probe demonstrated feasibility with fixed tuning frequencies for 1H, 13C, and
15N nuclei at 11.7 T for biological applications. The phase-II probe will advance the technology by extending
the tuning capabilities in two versions, an H/X/Y SAS-PFG probe with two broad-band low-frequency channels,
and a 1H/19F/X SAS-PFG probe. Additionally, these triple-channel probes will be compatible with a
commercially available three-axis gradient coil in order to enable gradient enha...

## Key facts

- **NIH application ID:** 10456218
- **Project number:** 5R44GM130201-03
- **Recipient organization:** DOTY SCIENTIFIC, INC.
- **Principal Investigator:** Francis DAVID Doty
- **Activity code:** R44 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $668,446
- **Award type:** 5
- **Project period:** 2018-09-01 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10456218

## Citation

> US National Institutes of Health, RePORTER application 10456218, A Reliable Switched Angle Spinning (SAS) Probe with Gradients (PFG) for Proteins in Solid-State NMR (5R44GM130201-03). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10456218. Licensed CC0.

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