Qxi probe

Deuterium oxide (D₂O, 99.9% D) and 3-trimethylsilyl-²H₄-propionic acid sodium salt (TSP) were purchased from Cambridge Isotope Laboratories, Inc. (Miami, U.S.A.) and from Sigma-Aldrich (St. Louis, MO). Spectra were obtained from solutions in D₂O (580 µL plus 20 µL of TSP 1 mg/mL at 30 °C, using TSP as reference (δ = 0.00 ppm), using a Bruker AVANCE III NMR spectrometer operating at 14.1 Tesla (600.13 MHz for ¹H) equipped with a QXI probe with gradient on the z-axis (Bruker Biospin, Germany). 2D ¹³C/¹H multiplicity-edited HSQC NMR experiments were carried out using heteronuclear correlation via double inept transfer with decoupling during acquisition, using trim pulses in inept transfer with multiplicity editing during the selection step (hsqcedetgpsisp2.2). The 2D HSQC experiments were recorded for quadrature detection in the indirect dimension, using 8 scans per series of 2 K × 256 W data points with zero filling in F1 (4 K) prior to Fourier transformation^{42 (link)}. Data processing and integration were performed using the software Topspin version 3.1 (Bruker Biospin, Rheinstetten, Germany). ¹³C/¹H correlations were assigned according to Nascimento et al.^{11 (link)}.