3.2.1. 1D 1H NMR Spectra Collection and Processing

The 1D ¹H NMR spectra shown in Figure 1 and Figure 2A were collected using an 850 MHz spectrometer. The pulse program p3919gp was applied. The ¹H carrier was placed on the water resonance at 4.8 ppm. The spectral width was 14 ppm and a total of 23,808 complex points were collected. The acquisition time was 1 s and recycle delay was 2 s. The number of scans were 1024 for calcitonin-salmon and rituximab DPs, 256 for exenatide DP and 128 for liraglutide, teriparatide and insulin glargine DPs. Each free induction decay (FID) was apodized with a 90° shifted sine-square window function, scaled half for the first point, zero-order phase corrected and zero filled to a spectral size of 32k points before Fourier transform (FT). A baseline correction method of splines was applied for the calcitonin-salmon and teriparatide spectra and no correction was applied for the liraglutide, exenatide, insulin glargine and rituximab spectra. All the 1D NMR data were processed and analyzed using MestReNova 14.1 software (Mestrelab Research S.L.).

The 1D ¹H NMR spectra shown in Figure 2B were collected using a 600 MHz spectrometer. The pulse program of modified 1D NOESY noe-p3919.kc was applied [20]. The ¹H carrier was placed on the water resonance at 4.8 ppm. The spectral width was 13 ppm and a total of 16,384 complex points were collected. The acquisition time was 1 s and the recycle delay was 2 s. The NOE mixing time was 0.1 s. The number of scans was 1024. The NMR samples and data processing were identical to that used for the 850 MHz spectra.