Heteronuclear Triple Resonance Experiments

4 Heteronuclear Triple Resonance Experiments. - A very small number of new triple-resonance experiments was reported. A version of the 3D HNCA experiment was presented that suppresses coherence transfer through /(N,C ). The method is based on the scalar couplings of sequential and to the same which is not the case for the intraresidue and 

During to transfer the antiphase coherence relative to is created 

To overcome the problem of low dispersion of sugar resonances in nucleotides Hu et al. proposed to incorporate HCN transfer into HCCH-type sequences resulting in 3D MQ-HCN-CCH-TOCSY and 3D MQ-HCN-CCH-COSY experiments. The coherence transfer pathway starts with HT-CT transfer followed by an out-and-back transfer to N1/N9 for indirect detection and subsequent transfer through network. As a result the CCH spectra are additionally resolved with chemical shift. During the C -N1/N9 transfer MQ HT/CT coherence is active to reduce the relaxation losses due to relaxation. The experiments were successfully applied to a 23-mer RNA aptamer. 

Adiabatic pulses and isotropic mixing Use of adiabatic pulses for C,C and H,H TOCSY transfer, HCCH-TOCSY 

Analytical expression for amplitudes and phases of adiabatic decoupling sidebands 

Increased sensitivity in NMR spectra due to the use of cryogenic probes makes it possible to record triple-resonance experiments at natural abundance in the uniformly N-labelled samples. Such systems have an advantage of negU-gible effect of couplings, which was used by Kupce et to design a 

Selective protonation of side-chain methyl groups in otherwise perdeuterated 

New experiments for the assignment of quarternary carbons in the aromatic rings of nucleotides were described by Furtig et al. The 2D HNC6C5 experiment is derived from the HNCOCA sequence and utilises H1- N1- C6- C5 out-and-back transfer in guanine to correlate HI and C5 resonances. The 2D H8(H6)-C8(C6)-N9(N1)-C4(C2) and Hl -Cr-N9(Nl)-C4(C2) experiments are of HCNC type and correlate HI protons or the aromatic H8/H6 protons with C4 and C2 purines and pyrimidines, respectively. 

Fast multidimensional methods 2D Hadamar COSY, TOCSY and NOESY 3D Hadamard TOCSY-HSQC 

Time reduction in homonuclear spectra using Hadamard spectroscopy Time reduction in heteronuclear spectra using Hadamard spectroscopy GFT NMR experiments for resonance assignments 

---

In heteronuclear triple-resonance experiments (TCP Majumdar and Zuiderweg, 1995), the spin system corresponds to an effective PPP coupling topology if planar effective coupling tensors are created. In an ISQ system, triple-resonance Hartmann-Hahn transfer from a spin / to a spin Q is only efficient if I//5I J,q (Glaser, 1993c Majumdar and... 

Logan TM, Olejniczak ET, Xu RX, Fesik SW (1992) Side chain and backbone assignments in isotopically labeled proteins from two heteronuclear triple resonance experiments. FEES Lett 314 413 18... 

Exploitation of the TROSY effect is rather straightforward. In contrast to 15N-HSQC (Heteronuclear Single Quantum Coherence) or standard triple-resonance experiments based on 15N-HSQC, no radio frequency pulses or composite pulse decoupling should be applied on amide protons when HN spin is not in the transverse plane. Likewise the 15N decoupling should be... 

A heteronuclear (29Si—13C) INADEQUATE253 254 experiment falls into the category of triple resonance experiments that are treated in Section VI.B. 

W which have very low magnetogyric ratios. It is also possible to use triple resonance experiments to record heteronuclear INDOR spectra, as in the MINDOR and TINDOR experiments (109) (see p. 356), or to use a reasonably sensitive nucleus such as rather than the proton for detection. 

FIGURE 12.16 Pulse sequence for the triple resonance 3D NMR experiment HNCO. H and N denote H and 15N, C denotes 13C=0, and K denotes 13C . Pulses at times 1, 2, and 3 constitute an INEPT sequence that transfers coherence from H to. V, where it precesses during q. Pulses at times 6, 7, and 8 represent an HMQC sequence that creates multiple quantum coherence in C (where it precesses during and transfers coherence back to N. Pulses 10 and 11 are an inverse INEPT sequence that transfers coherence back to H for detection during f3.The other 180° pulses refocus heteronuclear spin couplings. Note that coherence is not transferred to spin K. 

In this section, aspects of Hartmann-Hahn experiments are discussed that are important for practical applications. There are obvious instrumental differences between heteronuclear and homonuclear Hartmann-Hahn experiments, such as the necessity for one or several heteronuclear rf channels and double- or triple-resonance probes. In addition, the rf amplitude of the channels must be matched, that is, the duration of the respective 90° pulses must be carefully adjusted such that the difference is not larger than a few percent. A detailed discussion of setup experiments for the calibration of hetero pulses has been given, for example, by Griesinger et al. (1994). 

ROESY-TOCSY experiment Selective inverse detection of C-H correlation Scalar heteronuclear recoupled interaction by multiple pulse Simulation program one Selectively inverted soft PICSY Singular value decomposition Tailored correlation spectroscopy Triple-resonance J cross-polarization Total correlation spectroscopy TOCSY-ROESY experiment TOCSY without NOESY... 

For non-deuterated complexes, NMR experiments were performed on either Vaiian Unity600 or Varian Unity+500 spectrometers. The 600 MHz instrument was equipped with a triple resonance probe and a PTS synthesizer as a pseudo fourth channel. The 500 MHz spectrometer was a four channel instrument with a triple resonance probe with an actively shielded pulsed field gradient coil. All experiments were performed at 37 C. The heteronuclear experiments shown in Figure 1 were performed as described in Zhang et al (11) and Revington et al (24). For all 3D ex riments 32 transients were required for sufficient signal to noise. This necessitated the use of fewer increments and the use of linear prediction (25)... 

---