Dpx ft nmr spectrometer

The SF-GMA was synthesized by GMA modification according to a previous method. Briefly, the cocoons were boiled in a 0.05 M Na₂CO₃ solution for 30 min to remove sericin, and then they were washed several times with distilled water. Subsequently, 30 g of degummed and dried silk fibroin was dissolved in 150 mL of 9.3 M LiBr solution at 60 °C for 1 h, after which 9 mL of GMA solution was added to the mixture and stirred at 300 rpm for 3 h. The resulting solution was then dialyzed against milli-Q water for 4 days. Finally, the obtained methacrylate SF solution was concentrated to 20% using a 3500 Da dialysis bag against a PEG solution with a molecular weight of 8000.
The synthesis of the SF-GMA macromer was confirmed using ¹H NMR. After lyophilization, 5 mg of the regenerated silk fibroin (RSF) and SF-GMA was dissolved in 700 μL of deuterium oxide. The ¹H NMR spectra were collected using a Bruker DPX FT-NMR spectrometer with a frequency of 400 MHz. The degree of methacrylate substitution was determined using the formula of 1-(lysine integration signal of SF-GMA/lysine integration signal of unsubstituted RSF).