T1 - 3D localized 1H-13C heteronuclear single-quantum coherence correlation spectroscopy in vivo The 3D localized 2D 1H-13C correlation spectra from a monkey brain in vivo were obtained after glucose injection, and amino acid metabolism was detected that is, glutamate appeared immediately after the injection, followed by the appearance of glutamate, glutamate, and glutamine. The localization capabilities of this method were confirmed in a phantom experiment. The preparation (echo) period 2τ can then be set substantially longer than 1/(2 1J(CH)), so that even in a whole-body system, slice-selective 90°(1H) pulses and gradient pulses can be applied in that period. The 180°(13C) and 180°(1H) pulses are separated in time, and the 180°(13C) pulse is applied at 1/(4 1J(CH)) before the 90°(1H) polarization transfer pulse. This method has the following special feature in the preparation period. (C) 2000 Wiley- Liss, Inc.Ībstract = "A method for spatially three-dimensional (3D) localized two-dimensional (2D) 1H-13C correlation spectroscopy, localized HSQC, is proposed. The 3D localized 2D 1H- 13C correlation spectra from a monkey brain in vivo were obtained after glucose injection, and amino acid metabolism was detected that is, glutamate appeared immediately after the injection, followed by the appearance of glutamate, glutamate, and glutamine. The preparation (echo) period 2τ can then be set substantially longer than 1/(2 1J(CH)), so that even in a whole-body system, slice-selective 90°( 1H) pulses and gradient pulses can be applied in that period. The 180°( 13C) and 180°( 1H) pulses are separated in time, and the 180°( 13C) pulse is applied at 1/(4 1J(CH)) before the 90°( 1H) polarization transfer pulse. In TONE D-HMQC-4, N is a constant that determines the total duration of the LG-SL and π pulses such that N* τ r > maximum t 1 time.A method for spatially three-dimensional (3D) localized two-dimensional (2D) 1H- 13C correlation spectroscopy, localized HSQC, is proposed. m and n are multiples of 2 and m usually equals 2 n, except for samples featuring very strong 1H–X dipolar coupling constants. m, n and p are integers denoting duration of the recoupling and LG-SL pulses. τ r denotes rotor period and π/2, π, 35° indicate tip angles of pulses. Recoupling (Rec.) and Lee-Goldberg spin-lock (LG-SL) are abbreviated. (A) Conventional D-HMQC, (B) TONE D-HMQC-1, (C) TONE D-HMQC-2, (D) TONE D-HMQC-3, (E) TONE D-HMQC-4. We demonstrate the application of these methods to acquire 1H detected 2D 1H D-HMQC pulse sequences. ![]() The 1H refocusing pulses also restore the orthogonality of in-phase and anti-phase magnetization for all crystallite orientations at the end of each recoupling block, enabling the use of 90° flip-back or LG spin-lock trim pulses to reduce the intensity of uncorrelated signals. The TONE D-HMQC sequence uses 1H π-pulses to refocus the evolution of 1H CSA across each SR4 2 1 recoupling block, improving the stability of the pulse sequence to random MAS frequency fluctuations. Monte-Carlo and numerical simulations confirm that t 1-noise in conventional D-HMQC primarily occurs because random MAS frequency fluctuations cause variations in the NMR signal amplitude from scan to scan, leading to imperfect cancellation of uncorrelated signals by phase cycling. In this contribution, we describe novel pulse sequences, termed t 1-noise eliminated (TONE) D-HMQC, that minimize t 1-noise and can provide higher sensitivity and resolution than conventional D-HMQC. A long-standing problem in 1H detected D-HMQC solid-state NMR experiments is the presence of t 1-noise which reduces sensitivity and impedes spectral interpretation. Dipolar heteronuclear multiple-quantum coherence (D-HMQC) is a powerful technique that can be potentially utilized to obtain 1H detected 2D HETCOR solid-state NMR spectra of any NMR active nucleus. Heteronuclear correlation (HETCOR) spectroscopy is one of the key tools in the arsenal of the solid-state NMR spectroscopist to probe chemical and spatial proximities between two different nuclei and enhance spectral resolution.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |