title: The challenge to quantify proteins with charge trains due to isoforms or conformers.
abstract: Single proteins separated by 2-DE often show multiple spots spreading along the first dimension. In many cases, such charge trains are explained by isoform differences or by putative post-translational modifications including phosphorylation, glycosylation and others. We now report that individual spots of such charge trains on 2-D gels in fact often represent the same protein, but, apparently due to conformational changes, segregate to different isoelectric points. If MS analysis reveals protein identity, we therefore suggest integrating all individual spots within a charge train for quantification. Especially in quality control of pharmaceutical proteins, the integration of the spot groups of all active contents is preferable in order to obtain reproducible and reasonable quantitative results. However, most commercial software packages for gel analysis integrate the signals spot-wise. We provide an improved quantification tool for proteins with charge train groups. This calculation can be implemented using the MATLAB software and the self-developed "Correct Integration Software System" or the commercial software package Delta2D.
authors.affiliation: Institute of Pharmaceutical Chemistry, Technische Universität Braunschweig, Braunschweig, Germany.
authors.forename: Xi
authors.initials: X
authors.lastname: Deng
authors.forename: Thomas
authors.initials: T
authors.lastname: Hahne
authors.forename: Simone
authors.initials: S
authors.lastname: Schröder
authors.forename: Sabine
authors.initials: S
authors.lastname: Redweik
authors.forename: Dashnor
authors.initials: D
authors.lastname: Nebija
authors.forename: Hendrik
authors.initials: H
authors.lastname: Schmidt
authors.forename: Ottmar
authors.initials: O
authors.lastname: Janssen
authors.forename: Bodo
authors.initials: B
authors.lastname: Lachmann
authors.forename: Hermann
authors.initials: H
authors.lastname: Wätzig
mesh_terms: D000818:Animals; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods* / Q000592:standards; D006801:Humans; D020033:Protein Isoforms; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D040901:Proteomics / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012984:Software
chemical_list: D020033:Protein Isoforms; D011506:Proteins