title: Proton-detected solid-state NMR spectroscopy of fully protonated proteins at slow to moderate magic-angle spinning frequencies.
abstract: (1)H-detection offers a substitute to the sensitivity-starved experiments often used to characterize biomolecular samples using magic-angle spinning solid-state NMR spectroscopy (MAS-ssNMR). To mitigate the effects of the strong (1)H-(1)H dipolar coupled network that would otherwise severely broaden resonances, high MAS frequencies (>40kHz) are often employed. Here, we have explored the alternative of stroboscopic (1)H-detection at moderate MAS frequencies of 5-30kHz using windowed version of supercycled-phase-modulated Lee-Goldburg homonuclear decoupling. We show that improved resolution in the (1)H dimension, comparable to that obtainable at high spinning frequencies of 40-60kHz without homonuclear decoupling, can be obtained in these experiments for fully protonated proteins. Along with detailed analysis of the performance of the method on the standard tri-peptide f-MLF, experiments on micro-crystalline GB1 and amyloid-β aggregates are used to demonstrate the applicability of these pulse-sequences to challenging biomolecular systems. With only two parameters to optimize, broadbanded performance of the homonuclear decoupling sequence, linear dependence of the chemical-shift scaling factor on resonance offset and a straightforward implementation under experimental conditions currently used for many biomolecular studies (viz. spinning frequencies and radio-frequency amplitudes), we expect these experiments to complement the current (13)C-detection based methods in assignments and characterization through chemical-shift mapping.
authors.affiliation: TIFR Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research Hyderabad, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India. Electronic address: kaustuberm@tifrh.res.in.
authors.forename: Kaustubh R
authors.initials: KR
authors.lastname: Mote
authors.affiliation: TIFR Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research Hyderabad, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India; Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India. Electronic address: madhu@tifr.res.in.
authors.forename: Perunthiruthy K
authors.initials: PK
authors.lastname: Madhu
mesh_terms: D000465:Algorithms; D016229:Amyloid beta-Peptides / Q000737:chemistry; D002247:Carbon Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D011846:Radio Waves; D018080:Receptors, GABA-B / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D002247:Carbon Isotopes; D011506:Proteins; D011522:Protons; D018080:Receptors, GABA-B
keywords: Homonuclear decoupling; Phase-modulated Lee Goldburg; Proton-detection; Solid-state magic-angle-spinning NMR; Windowed-detection