Modulation depth enhancement of ESEEM experiments using pulse trains

Mitrikas, George; Prokopiou, Georgia

doi:10.1016/j.jmr.2015.03.002

Cited by 12 publications

(7 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This means that 13 C is approximately three times less sensitive than 2 H which results in lower signal intensity and poorer signal to noise. Since the sensitivity of ESEEM experiments is mainly dictated by the modulation depth of these experiments ( k ), for I=1/2, nuclei the FT peak amplitude is lowered significantly, resulting in a loss of sensitivity when using 13 C compared to 2 H [31–33]. Taking into account the nuclear spin and the gyromagnetic ratio of 13 C, the maximum distance detectable is a maximum of 7 Å, whereas for 2 H the detection limit is up to 8 Å.…”

Section: Resultsmentioning

confidence: 99%

Utilization of 13C-labeled amino acids to probe the α-helical local secondary structure of a membrane peptide using electron spin echo envelope modulation (ESEEM) spectroscopy

Bottorf

Sahu

McCarrick

et al. 2018

Biochimica et Biophysica Acta (BBA) - Biomembranes

View full text Add to dashboard Cite

Electron spin echo envelope modulation (ESEEM) spectroscopy in combination with site-directed spin labeling (SDSL) has been established as a valuable biophysical technique to provide site-specific local secondary structure of membrane proteins. This pulsed electron paramagnetic resonance (EPR) method can successfully distinguish between α-helices, β-sheets, and 3-helices by strategically using H-labeled amino acids and SDSL. In this study, we have explored the use ofC-labeled residues as the NMR active nuclei for this approach for the first time. C-labeled d-valine (Val) or C-labeled d-leucine (Leu) were substituted at a specific Val or Leu residue (i), and a nitroxide spin label was positioned 2 or 3 residues away (denoted i-2 and i-3) on the acetylcholine receptor M2δ (AChR M2δ) in a lipid bilayer. The C ESEEM peaks in the FT frequency domain data were observed for the i-3 samples, and noC peaks were observed in the i-2 samples. The resulting spectra were indicative of the α-helical local secondary structure of AChR M2δ in bicelles. This study provides more versatility and alternative options when using this ESEEM approach to study the more challenging recombinant membrane protein secondary structures.

show abstract

Section: Resultsmentioning

confidence: 99%

Utilization of 13C-labeled amino acids to probe the α-helical local secondary structure of a membrane peptide using electron spin echo envelope modulation (ESEEM) spectroscopy

Bottorf

Sahu

McCarrick

et al. 2018

Biochimica et Biophysica Acta (BBA) - Biomembranes

View full text Add to dashboard Cite

show abstract

“…One critical limitation when increasing the number of refocusing pulses 1105 may be encountered for systems that exhibit pronounced nuclear modulation effects due to forbidden transitions, which are also excited by chirp refocusing pulses 23,56,57 . In particular, the CP timing of the refocusing pulses could enhance such modulation effects 58 .…”

Section: Discussionmentioning

confidence: 99%

Double electron–electron resonance with multiple non-selective chirp refocusing

Doll

Jeschke

2017

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

A new approach to double electron-electron resonance (DEER) for distance determination involving nitroxide spin labels at dilute concentrations is presented. In general, DEER pulse sequences rely on double resonance between pump and observer spins excited by selective pulses at two distinct microwave frequencies. In the new approach abbreviated as nDEER, non-selective chirp pulses that refocus all relevant spin pairs are combined with DEER. This non-selective refocusing results in suppression of unmodulated contributions, such as the constant contribution as well as the background curvature due to inter-molecular spin partners in ordinary DEER data. Due to this dipolar attenuation effect, primary nDEER data are closer to the dipolar modulation of primary interest than ordinary DEER data. Restrictions of nDEER are that secondary information related to these unmodulated contributions becomes difficult to retrieve. Accordingly, incomplete deconvolution of the inter-molecular background prevents the application of nDEER to rigid spin pairs at high concentrations. A key advantage of nDEER is the high fidelity of the chirp refocusing pulses, which is important for nDEER schemes that incorporate dynamical decoupling to access longer distances. In this context, nDEER with Carr-Purcell (CP) pulse trains having N = 2 and N = 4 refocusing pulses are demonstrated. These CP nDEER sequences require a total of N + 2 pulses, which is less than the 2N + 1 pulses required for CP DEER schemes. The pump pulse position is incremented throughout the refocusing pulses, which restricts the minimum time increment to 96 ns on our spectrometer and therefore complicates application to distances below 3 nm. At Q-band frequencies, unwanted modulations related to pulse imperfections contribute only 3.5% relative to the principal nDEER modulation. Accordingly, there is no need for dedicated data reconstruction methods as in CP DEER methods.

show abstract

“…However, up to now a detailed analysis of the underlying mechanisms giving rise to these complications, their impact on the determination of the spin dephasing time and the ways of elimination of unwanted effects were not elaborated sufficiently. The phase cycling which we use in our work as well as other cycling protocols [44] are definitely helpful in improving the quality of a CPMG ESR experiment. A more detailed theoretical and experimental treatment of this very interesting problem will be published elsewhere.…”

Section: Discussionmentioning

confidence: 99%

Tuning the spin coherence time of Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes by advanced ESR pulse protocols

Zaripov¹,

Vavilova²,

Khairuzhdinov³

et al. 2017

Beilstein J. Nanotechnol.

View full text Add to dashboard Cite

We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins S = 1/2 in single crystals of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opba)] (1%) in the host lattice of [n-Bu4N]2[Ni(opba)] (99%, opba = o-phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opbon-Pr2)] (1%) in the host lattice of [n-Bu4N]2[Ni(opbon-Pr2)] (99%, opbon-Pr2 = o-phenylenebis(N(propyl)oxamidato)). For that we have measured the electron spin dephasing time T m at different temperatures with the two-pulse primary echo and with the special Carr–Purcell–Meiboom–Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results. It shows the efficiency of the suppression of the electron spin decoherence channel in the studied complexes arising due to spectral diffusion induced by a random modulation of the hyperfine interaction with the nuclear spins. We argue that this method can be used as a test for the relevance of the spectral diffusion for the electron spin decoherence. Our results have revealed a prominent role of the opba4– and opbon-Pr2 4– ligands for the dephasing of the Cu spins. The presence of additional 14N nuclei and protons in [Cu(opbon-Pr2)]2– as compared to [Cu(opba)]2– yields significantly shorter T m times. Such a detrimental effect of the opbon-Pr2 4− ligands has to be considered when discussing a potential application of the Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes as building blocks of more complex molecular structures in prototype spintronic devices. Furthermore, in our work we propose an improved CPMG pulse protocol that enables elimination of unwanted echoes that inevitably appear in the case of inhomogeneously broadened ESR spectra due to the selective excitation of electron spins.

show abstract

Modulation depth enhancement of ESEEM experiments using pulse trains

Cited by 12 publications

References 30 publications

Utilization of 13C-labeled amino acids to probe the α-helical local secondary structure of a membrane peptide using electron spin echo envelope modulation (ESEEM) spectroscopy

Utilization of 13C-labeled amino acids to probe the α-helical local secondary structure of a membrane peptide using electron spin echo envelope modulation (ESEEM) spectroscopy

Double electron–electron resonance with multiple non-selective chirp refocusing

Tuning the spin coherence time of Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes by advanced ESR pulse protocols

Contact Info

Product

Resources

About