title: A multiway approach for classification and characterization of rabbit liver apothioneins by CE-ESI-MS.
abstract: We applied a multiway approach to extract information from the analysis of protein isoforms by CE-ESI-MS. Metallothioneins (MT) are low-molecular-weight proteins (6-7 kDa) with a strong affinity for heavy-metal ions. Rabbit liver MT-I and MT-II fractions are purified from MT samples. At low pH, the bound metal ions were released from the amino acid structures, giving rise to apothioneins. MT-I, MT-II and MT apothioneins, which are complex mixtures of protein isoforms, were analyzed by CE-ESI-MS. After data pre-processing, parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least squares (MCR-ALS) were applied to the data sets. In both cases, the models enabled classification of the protein samples and identification of their characteristic sub-isoforms using a set of three components. MCR-ALS required an initial estimate of the pure mass spectra of the three components. Thus, PARAFAC loadings were used to initialize the MCR-ALS optimization. The classifications obtained with MCR-ALS were slightly better than those obtained with PARAFAC, probably because MCR-ALS was less affected by the small migration time shifts of the pre-processed electropherograms. However, no differences were found between the pure mass spectra of the three components in either model. Finally, MCR-ALS allowed us to obtain an individual electrophoretic profile of each of the three components for each of the samples analyzed, which proved valuable for characterization and quantification purposes.
authors.affiliation: Departamento de Química Analítica, Universidad de Barcelona, Barcelona, España. fbenavente@ub.edu
authors.forename: Fernando
authors.initials: F
authors.lastname: Benavente
authors.forename: Balbina
authors.initials: B
authors.lastname: Andón
authors.forename: Estela
authors.initials: E
authors.lastname: Giménez
authors.forename: Alejandro C
authors.initials: AC
authors.lastname: Olivieri
authors.forename: José
authors.initials: J
authors.lastname: Barbosa
authors.forename: Victoria
authors.initials: V
authors.lastname: Sanz-Nebot
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000032:analysis* / Q000145:classification*; D019075:Electrophoresis, Capillary; D016018:Least-Squares Analysis; D008099:Liver / Q000737:chemistry*; D008668:Metallothionein / Q000032:analysis* / Q000145:classification*; D015999:Multivariate Analysis; D020033:Protein Isoforms / Q000032:analysis / Q000145:classification; D011817:Rabbits; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001059:Apoproteins; D020033:Protein Isoforms; C031834:apothionein; D008668:Metallothionein