Improvement of homonuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance utilising radiofrequency imperfections

Bosman, Leon; Madhu, P.K.; Vega, Shimon; Vinogradov, Elena

doi:10.1016/j.jmr.2004.04.001

Cited by 61 publications

(60 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 2D NMR experiment combines MELODI filter (24,25), LG-CP block with wPMLG3 þ decoupling (26)(27)(28) to yield medium-and long-range 1 H-13 C correlation spectra with 1 H-enhanced sensitivity. The wPMLG3 þ decoupling efficiency correlates to several experimental parameters, like rf field power (ν 1 ), unit pulse length (Δt), acquisition windows (τ w ), rotation frequency (ν r ), and 1 H rf offset frequency (Δν).…”

Section: Methodsmentioning

confidence: 99%

“…The MELODI filter effectively silences magnetization of protons directly bonded to the chromophore, while emphasizing its medium-and long-range 1 H contacts (24,25). The sensitivity enhancement of 1 H indirect dimension was achieved through the use of windowed phase-modulated Lee-Goldburg (wPMLG) homonuclear decoupling scheme (26)(27)(28) over the 1 H evolution period (t 1 ), in our case, wPMLG3 þ . Our previous 2D 13 C-13 C dipolar-assisted rotational resonance (DARR) NMR studies on various states of this protein provided full sets of 13 C chemical shifts of the chromophore (18) and hence the basis for the interpretation of the heteronuclear spectra presented in Fig.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Song

Psakis

Lang

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

162

299

View full text Add to dashboard Cite

Phytochrome photoreceptors mediate light responses in plants and in many microorganisms. Here we report studies using 1 H-13 C magic-angle spinning NMR spectroscopy of the sensor module of cyanobacterial phytochrome Cph1. Two isoforms of the red-light absorbing Pr ground state are identified. Conclusive evidence that photoisomerization occurs at the C15-methine bridge leading to a β-facial disposition of the ring D is presented. In the far-red-light absorbing Pfr state, strong hydrogen-bonding interactions of the D-ring carbonyl group to Tyr-263 and of N24 to Asp-207 hold the chromophore in a tensed conformation. Signaling is triggered when Asp-207 is released from its salt bridge to Arg-472, probably inducing conformational changes in the tongue region. A second signal route is initiated by partner swapping of the B-ring propionate between Arg-254 and Arg-222.chromophore-protein interaction | signal transduction | solid-state NMR | photomorphogenesis P hytochrome was first demonstrated in plants as a red-lightdependent photoreceptor regulating numerous photomorphogenic processes (1, 2). Phytochromes are, however, also now known in photosynthetic prokaryotes including cyanobacteria (3, 4), nonphotosynthetic bacteria (5), and fungi (6). Generally, the phytochrome apoprotein binds an open-chain tetrapyrrole as a chromophore (7,8) to form the red-light absorbing Pr ground state (λ max ≈ 658 nm in case of cyanobacterial phytchrome Cph1 from Synechocystis 6803). Red light absorption photoactivates the molecule to form the photoactivated far-red-light absorbing Pfr state (λ max ≈ 702 nm for Cph1) via a series of intermediates (8-10). Photoactivation is thought to be initiated by a double bond isomerization of the chromophore (10, 11). Early NMR spectroscopic studies on proteolytic phytochrome fragments (12, 13) indicated that this isomerization occurs at the C15═C16 double bond (for numbering, see Fig. 1A), a geometrical change in line with vibrational spectroscopic investigations (14-16) and results from recent 13 C solid-state NMR (17, 18) in which the most significant changes during the light-triggered conversions are confined to rings C and D. Exact geometries of the chromophore in the Pr state have been resolved as periplanar ZZZssa configurations in bacteriophytochromes from Deinococcus radiodurans (19) and Rhodopseudomonas palustris (20) as well as in the more plant-phytochrome-like Cph1 from the cyanobacterium Synechocystis 6803 (21). On the other hand, the crystal structure of the unusual bacteriophytochrome PaBphP Pseudomonas aeruginosa (22) whose ground state is Pfr shows a ZZEssa conformation, consistent with the expected primary photochemistry at the C15═C16 double bond (Fig. 1 B vs. C). Very recently, however, Ulijasz et al. presented structural simulations based on liquid NMR data of a 20-kDa GAF (cGMP phosphodiesterase/ adenylyl cyclase/FhlA) domain fragment of "SyB-Cph1" phytochrome from the thermotolerant cyanobacterium Synechococcus OSB′ (23). Surprisingly, they concluded that photoisomerization occ...

show abstract

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Song

Psakis

Lang

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

162

299

View full text Add to dashboard Cite

show abstract

“…The dashed green line corresponds to l CS = 0.43, while the shaded area extends from l CS = 0.41 to l CS = 0.45. effect of the windows on the dipolar and chemical-shift scaling factors but also through an increased sensitivity of the sequence to pulse imperfections such as the amplitude and phase transients associated with rapid changes in the amplitude and/or phase of an RF pulse. [35,[42][43][44] In a windowless decoupling sequence, the transients associated with the rise and fall of the decoupling pulses have a minimal effect on decoupling performance because these pulse imperfections represent a very small fraction of the full decoupling sequence. By contrast, in windowed decoupling where the RF is necessarily switched on and off repeatedly to allow for the insertion of detection windows, the errors associated with the pulse switching accumulate with each cycle of the sequence and so become significant.…”

Section: Windowed Homonuclear Dipolar Decouplingmentioning

confidence: 99%

“…[32,[42][43][44][45] The most significant effect of pulse imperfections on decoupling performance has been found to be a non-linear scaling of the chemical shift at offsets near the carrier frequency of the RF irradiation. The consequence of this variation in the chemical-shift scaling factor is that good quality spectra can only be acquired at large resonance offsets.…”

Section: Windowed Homonuclear Dipolar Decouplingmentioning

confidence: 99%

“…In addition, it has been observed that decoupling performance is typically better either at positive or negative offset frequencies, depending on the particulars of the decoupling sequence used and the spectrometer hardware. [43,44] One solution to the problem of offset-dependent chemical-shift scaling factors, proposed by Vega and coworkers, is the super-cycled PMLG sequence. [32] This sequence combines two PMLG sequences where one is phase shifted relative to the other by p. In the LG4 nomenclature introduced above, this is a four-step LG sequence AĀ BB with a = 908.…”

Section: Windowed Homonuclear Dipolar Decouplingmentioning

confidence: 99%

See 1 more Smart Citation

High‐Resolution ¹H Solid‐State NMR Spectroscopy Using Windowed LG4 Homonuclear Dipolar Decoupling

Halse¹,

Schlagnitweit²,

Emsley³

2014

Israel Journal of Chemistry

View full text Add to dashboard Cite

We investigate the optimal implementation of windowed LG4 decoupling for the direct acquisition of high‐resolution 1H solid‐state NMR spectra in the moderate magic‐angle spinning regime (ωr<2π × 35 kHz). We determine how the optimal value of the azimuth of the LG rotation axis, α, is affected by the choice of windowing parameters. We find that for both the windowless and windowed implementation of LG4, the optimal value of α is that for which the chemical‐shift scaling factor is approximately 0.43. We then provide an analytical expression for estimating the chemical‐shift scaling factor as a function of both α and the windowed decoupling parameters, which allows the optimal value of α to be easily determined for any implementation of LG4. We also introduce a simple and general method for improving the performance of any phase‐modulated homonuclear dipolar decoupling sequence by compensating for pulse imperfection errors that accumulate in windowed spectra due to the repeated switching of the RF irradiation. This method involves the introduction of short (<0.5 µs) compensation pulses at the start and end of each decoupling pulse, the duration and phase of which are chosen to cancel the effects of the amplitude and phase transients that arise as a result of the RF switching. We demonstrate how this method can be implemented for homonuclear dipolar decoupling sequences such as wPMLG and wLG4 to reduce the chemical‐shift scaling factor distortions generated by phase transients such that high‐quality, high‐resolution 1H NMR spectra can be acquired at arbitrary RF offsets.

show abstract

Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid‐State NMR Spectroscopy

Frantsuzov

Vasa²,

Ernst

et al. 2017

ChemPhysChem

View full text Add to dashboard Cite

Factors affecting the performance of 1H heteronuclear decoupling sequences for magic‐angle spinning (MAS) NMR spectroscopy of organic solids are explored, as observed by time constants for the decay of nuclear magnetisation under a spin‐echo (T2' ). By using a common protocol over a wide range of experimental conditions, including very high magnetic fields and very high radio‐frequency (RF) nutation rates, decoupling performance is observed to degrade consistently with increasing magnetic field. Inhomogeneity of the RF field is found to have a significant impact on T2' values, with differences of about 20 % observed between probes with different coil geometries. Increasing RF nutation rates dramatically improve robustness with respect to RF offset, but the performance of phase‐modulated sequences degrades at the very high nutation rates achievable in microcoils as a result of RF transients. The insights gained provide better understanding of the factors limiting decoupling performance under different conditions, and the high values of T2' observed (which generally exceed previous literature values) provide reference points for experiments involving spin magnetisation refocussing, such as 2D correlation spectra and measuring small spin couplings.

show abstract

Improvement of homonuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance utilising radiofrequency imperfections

Cited by 61 publications

References 25 publications

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

High‐Resolution ¹H Solid‐State NMR Spectroscopy Using Windowed LG4 Homonuclear Dipolar Decoupling

Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid‐State NMR Spectroscopy

Contact Info

Product

Resources

About

Improvement of homonuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance utilising radiofrequency imperfections

Cited by 61 publications

References 25 publications

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

High‐Resolution 1H Solid‐State NMR Spectroscopy Using Windowed LG4 Homonuclear Dipolar Decoupling

Rationalising Heteronuclear Decoupling in Refocussing Applications of Solid‐State NMR Spectroscopy

Contact Info

Product

Resources

About

High‐Resolution ¹H Solid‐State NMR Spectroscopy Using Windowed LG4 Homonuclear Dipolar Decoupling