Fts 6000 ftir spectrometer

In typical, 10 g of gelatin and a certain amount of ethylenediamine (EDA) were dissolved in 250 mL of phosphate buffer saline (PBS, pH = 5.0) and pH was adjusted to 5.0 with hydrochloric acid. Subsequently, 5.35 g of EDC·HCl was added, which was adjusted to 500 mL with PBS and stirred at 37 °C for 1 h. The solution was dialyzed against water for 3 days and AG was obtained after lyophilization. The degree of modification on gelatin was evaluated by measuring the content of amino groups in AG. Specifically, 1 mL of 0.5 mg mL⁻¹ AG in PBS (pH = 7.4) was mixed with 1 mL of 4% (w/v) sodium bicarbonate (NaHCO₃) and 1 mL of 0.1% 2,4,6-trinitrobenzenesulfonic acid (TNBS) solution. The mixture was incubated at 40 °C for 2 h in the dark and the absorbance was measured at 415 nm using a Bio-Tek Synergy HT microplate reader. The standard solutions were prepared from β-alanine [50 (link)]. The content of amino groups in AG can be calculated by comparison with standard results. As to the characterization of chemical structure of PAG and AG, ¹H NMR and Fourier transform infrared (FTIR) spectroscopy were applied. For ¹H NMR, about 20 mg of ALG, PG, and PAG were dissolved in 0.5 mL of D₂O, and spectra were acquired with an INOVA 500 MHz spectrometer (Varian Associates, Palo Alto, USA). The FTIR spectra of PG, PAG, free gelatin, and AG were recorded with a Bio-Rad FTS-6000 FTIR spectrometer.