title: Analysis of the differentially expressed low molecular weight peptides in human serum via an N-terminal isotope labeling technique combining nano-liquid chromatography/matrix-assisted laser desorption/ionization mass spectrometry.
abstract: BACKGROUND
  Peptidomics analysis of human serum is challenging due to the low abundance of serum peptides and interference from the complex matrix. This study analyzed the differentially expressed (DE) low molecular weight peptides in human serum integrating a DMPITC-based N-terminal isotope labeling technique with nano-liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry (nano-LC/MALDI-MS).
  
  
  METHODS
  The workflow introduced a [d(6)]-4,6-dimethoxypyrimidine-2-isothiocyanate (DMPITC)-labeled mixture of aliquots from test samples as the internal standard. The spiked [d(0)]-DMPITC-labeled samples were separated by nano-LC then spotted on the MALDI target. Both quantitative and qualitative studies for serum peptides were achieved based on the isotope-labeled peaks.
  
  
  RESULTS
  The DMPITC labeling technique combined with nano-LC/MALDI-MS not only minimized the errors in peptide quantitation, but also allowed convenient recognition of the labeled peptides due to the 6 Da mass difference. The data showed that the entire research procedure as well as the subsequent data analysis method were effective, reproducible, and sensitive for the analysis of DE serum peptides.
  
  
  CONCLUSIONS
  This study successfully established a research model for DE serum peptides using DMPITC-based N-terminal isotope labeling and nano-LC/MALDI-MS. Application of the DMPITC-based N-terminal labeling technique is expected to provide a promising tool for the investigation of peptides in vivo, especially for the analysis of DE peptides under different biological conditions.
authors.affiliation: Shanghai Mass Spectrometry Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Jiapeng
authors.initials: J
authors.lastname: Leng
authors.forename: Dong
authors.initials: D
authors.lastname: Zhu
authors.forename: Duojiao
authors.initials: D
authors.lastname: Wu
authors.forename: Tongyu
authors.initials: T
authors.lastname: Zhu
authors.forename: Ningwei
authors.initials: N
authors.lastname: Zhao
authors.forename: Yinlong
authors.initials: Y
authors.lastname: Guo
mesh_terms: D000595:Amino Acid Sequence; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D017879:Isothiocyanates / Q000737:chemistry; D007553:Isotope Labeling / Q000379:methods*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D036103:Nanotechnology / Q000379:methods; D010455:Peptides / Q000097:blood*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D017879:Isothiocyanates; D010455:Peptides