Standard pulse sequence

The ¹H NMR spectrum of a 110 µM sample of IM30_H3b-7 in 20 mM HEPES pH 7.6, 100 mM NaCl supplemented with 10% D₂O was recorded on an 800 MHz Bruker Avance III HD NMR spectrometer equipped with a triple resonance HCN-cryogenic probe head at 298 K. Suppression of the water signal was achieved by excitation sculpting, using a Bruker standard pulse sequence. The spectrum was processed with Topspin (Bruker, Karlsruhe, Germany).

First, the cefotaxime sodium, its dimer and trimer were separately dissolved in DMSO-d6 to a concentration of approximately 20, 20 and 15 mg/ml respectively, and tetramethylsilane (TMS) was added as the internal standard peak (δ_H 0.00 and δ_C 0.00). The operating frequencies of the ¹H and ¹³C NMR were 600.13 and 150.90 MHz, respectively, the experimental temperature was 24.5°C, and the spectral widths were 11,904.76 and 35,714.29 Hz, respectively. The operating frequency of the attached proton test (APT) spectrum was 150.90 MHz, and the spectral width was 35,714.29 Hz. Bruker standard pulse sequence was used for the ¹H–¹H correlated spectroscopy (COSY), ¹H-¹³C heteronuclear single quantum (HSQC), and ¹H-¹³C heteronuclear multiple bond correlation (HMBC) experiments. The spectral widths of F2 (¹H) and F1 (¹H) of ¹H–¹H COSY were both 7,812.50 Hz, the sampling data array was t2 × t1 = 2048 × 128, and the number of transients averaged was 4. The F2 (¹H) and F1 (¹³C) spectral widths of HSQC and HMBC were 7,812.50 and 33,201.94 Hz, respectively, the sampling data array was t2 × t1 = 4,096 × 128, and the number of transients averaged was 8. The NMR spectra were processed using the Mestrenova 14.0.0 software.