Experimental: Substance P standard was obtained from Sigma-Aldrich. The 3-Gln sample was synthesized and then provided by Hayashi Kasei. Substance P, Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Leu-Met (Sigma-Aldrich) 3-Gln, Arg-Pro-Gln-Pro-Gln-Gln-Phe-Phe-Leu-Met (Hayashi Kasei) The peptide standard samples were dissolved in water containing 0.1% trifluoroacetic acid (TFA) at a concentration of 10 pmol/μL. α-Cyano-4-hydroxycinnamic acid (CHCA) was used as the matrix and was dissolved in 1:1 water/acetonitrile containing 0.1% TFA. Next, the peptide standard solution and CHCA solution were mixed together 1:1 by volume. Afterwards, 0.5 μL of this mixture was placed on the MALDI target plate (2.5 pmol/spot). Finally, the dried sample was measured using the SpiralTOF and TOF-TOF option available on the JMS-S3000 SpiralTOF MS system.