FAST-HSQC

O., van Zijl P. C. (1995) Improved sensitivity of HSQC spectra of exchanging protons at short interscan delays using a new fast HSQC (FHSQC) detection scheme that avoids water saturation. J Magn Reson 108(1), 94-8. 

F1SQC and F1MQC essentially provide similar information. F1SQC theoretically provides higher sensitivity than HSQC. However, HMQC is less prone to instrumental miscalibrations and, due to the shorter pulse sequence, is often more effective in samples with fast relaxation. 

A comparatively long N- -H hydrogen bond length in the benzoxazine dimer (see below), measured using an advanced solid state NMR technique (DIP-HSQC),has been reported [52]. This technique employs REDOR-type recoupling under fast MAS to recouple the heteronuclear - N dipolar interaction, such that rotor-encoded spinning sideband patterns are obtained. 

Heteronuclear NOEs (e.g., H - N or H - C hetNOEs) are obtained by measuring HSQC-type spectra (see the section entitled Two-dimensional heteronuclear correlation experiments ) with and without proton saturation. The hetNOE is extracted from the difference in the signal amplitude of these measurements and reports on the fast dynamics of the heteronuclear bonds (ps to ns timescale). Maximal hetNOE values are observed when the bond vector tumbles at the same frequency as the entire protein, whereas faster motion with respect to overall tumbling leads to smaller hetNOEs. 

Fig. 20. A fast flip-back WATERGATE HSQC (FHSQC) that avoids water saturation and radiation damping. The WATERGATE subunit uses a 3-9-19 pulse. Details of the phase cycling, delays and gradient strengths can be found elsewhere. ...

The name TROSY [5.226, 5.227] has now became an pseudonym for relaxation optimized pulse sequences and as such, nearly all triple resonance experiments are now available with a TROSY variant allowing the selection of the slowest relaxing component in a multiplet. Consequently, large bio-molecules can now be studied using triple resonance experiments. Check it 5.9.2.2 simulates a 2D [l N, IH] TROSY-HSQC experiment, the original experiment used to illustrate spin-state selection for fast relaxing spin systems. 

Sun ZY, Fmeh DP, Selenko P, Hoch JC, Wagner G (2005) Fast assignment of N-HSQC peaks using high-resolution 3D HNcocaNH experiments with non-uniform sampling. J Biomol NMR 33 43-50... 

Further investigations with boar seminal fluid performed by Kalic et al. [54] using a 600-MHz NMR instrument revealed the identification of the amino acids hypotaurine and carnitine. Semiselective HSQC 2D experiments on an 800-MHz speedometer [55] enable one to differentiate between the structurally similar polyamines, spermidine, spermine and their metabolic precursor putrescine, all attracting interest for tumor therapy, in seminal fluid. Recently, Tomlins et al. [56] studied dynamic biochemical processes in incubated human seminal fluid samples The enzymatic hydrolysis of phosphoiylcholine to choline and the conversion of uridine-5 -monophosphate to uridine were found to be very fast, whereas the slow polypeptide hydrolysis to amino acids can be inhibited by the addition of EDTA. It remains to be seen which role the biochemical changes play in the reproductive function. 

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

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