title: Characterizing changes in snow crab (Chionoecetes opilio) cryptocyanin protein during molting using matrix-assisted laser desorption/ionization mass spectrometry and tandem mass spectrometry.
abstract: BACKGROUND
  We report the matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) characterization of the cryptocyanin proteins of the juvenile Chionoecetes opilio crabs during their molting and non-molting phases. In order to assess the structural cryptocyanin protein differences between the molting and non-molting phases, the obtained peptides were sequenced by MALDI low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS).
  
  
  METHODS
  The cryptocyanin protein was isolated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed by MALDI-TOF/TOF-MS. The purified cryptocyanin protein was sequenced, using the 'bottom-up' approach. After tryptic digestion, the peptide mixture was analyzed by MALDI-QqTOF-MS/MS and the data obtained were used for the peptide mass fingerprinting (PMF) identification by means of the Mascot database.
  
  
  RESULTS
  It was demonstrated using MALDI-TOF/TOF-MS that the actual molecular weights of the non-molting and molting cryptocyanin proteins were different; these were, respectively, 67.6 kDa and 68.1 kDa. Using low-energy CID-MS/MS we have sequenced the trytic peptides to monitor the differences and similarities between the cryptocyanin molecular structures during the molting and non-molting stages.
  
  
  CONCLUSIONS
  We have demonstrated for the first time that the actual molecular masses of the cryptocyanin protein during the molting and non-molting phases were different. The MALDI-CID-MS/MS analyses allowed the sequencing of the cryptocyanins after tryptic digestion, during the molting and non-molting stages, and showed some similarities and staggering differences between the identified cryptocyanin peptides.
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, 232 Elizabeth Avenue, A1B 3X9, Canada.
authors.forename: Wael L L
authors.initials: WL
authors.lastname: Demian
authors.forename: Farid M
authors.initials: FM
authors.lastname: Jahouh
authors.forename: Don
authors.initials: D
authors.lastname: Stansbury
authors.forename: Edward
authors.initials: E
authors.lastname: Randell
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Brown
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Banoub
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003386:Brachyura / Q000737:chemistry* / Q000502:physiology; D002232:Carbocyanines / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018978:Molting; D010449:Peptide Mapping / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002232:Carbocyanines; C067343:kryptocyanine