2.2. Free Amino Acid and Peptide Analysis
dryness
HEAT
The high-performance liquid chromatography (HPLC) was used to determine free amino acid analysis of CV. Weigh 1 g of powder, add 10 times the amount of distilled water, and heat to solidify, and the solution is filtered to obtain an aqueous layer. The residue obtained by concentrating the aqueous layer to dryness under reduced pressure was dissolved in 0.2 N sodium citrate buffer (pH 2.2) and used as a sample for HPLC. Agilent LC system (Agilent Technologies, Santa Clara, CA, USA) and Capcellpak UG120 with properties of (250 mm × 4.6 mm × 5 μm) was used. The mobile phases were: A, 40 mM NaH2PO4 (pH 7.8) and B ACN:MeOH:DW (45:45:10 Peptide molecular weights of CVs were measured in linear mode using a RapifleX MALDI-TOF mass spectrometer (Bruker, Billerica, MA, USA). Sample preparation and peptide analysis were performed by modifying method Lu et al. [