纳升电喷雾串联质谱“序列对接法”确定多肽的加钠位点

Determination of Sodium Ion Addition Sites by Nanoelectrospray Mass Spectrometry/Mass Spectrometry Sequence Docking

用QuattroM icro三级四极串联质谱分析常见的20种氨基酸的加钠效果。结果表明,绝大多数氨基酸与钠离子的非共价键结合力很弱甚至没有,但脯氨酸和苯丙氨酸很容易形成加钠离子峰。采用“序列对接法”测出重组人酸性纤维细胞生长因子(rh-a FGF)C-端肽段的全序列,并确定钠离子的加成位点为该肽段的第6位脯氨酸(6Pro)。通过酸化样品溶液获得无加钠、无序列间隙的该肽全序列,与加钠肽段的序列一致。

Sodium ion addition of 20 natural occurring amino acids was investigated by triple quadruple tandem mass spectrometry. Results showed that most amino acids had extraordinary weak non-covalent binding to sodium ion, whilst proline and phenylalanine easily captured sodium ion from solvents. By tandem mass spectrometry ＂sequence docking＂ method on Q-TOF2 （Waters, USA）, full amino acid sequence of C-terminal peptide of acidic fibroblast growth factor was analyzed and the adding site of sodium ion was proline （6pro）. Sodium-addition peaks in peptide mass fingerprinting （PMF） apparently decreased after adding 1% formic acid, the peptide sequence without sodium-addition and sequence gap was determined using de novo technology,which was the same as the sequence of sodium-addition peptide.