title: Effect of barium tetraborate on the separation of tryptic digests of proteins by zone electrophoresis in uncoated capillaries.
abstract: A simple, fast, efficient and reproducible method for peptide separations in CZE is reported. It consists in running tryptic digests of peptides in an uncoated capillary, in a BGE composed of tetraborate as a buffering ion, in which the typical sodium counterion is substituted with barium. Efficient absorption of this divalent cation to ionized silanols and barium silicate precipitation seem to be able to shield effectively the silica surface from separands. This is demonstrated by the fact that, when tBa(2+) ions are present in solution (from pH 8.5 up to pH 11.0), the electroendoosmotic flow is reversed; such reversal being progressively higher at higher pH values, by up to a four-fold. Separations become progressively better at higher pH values, whereas at pH 11 in sodium tetraborate they are dramatically worsened. It is further hypothesized that the barium silicate layer further protects the silica surface against dissolution and corrosion which is quite substantial at pH 11.
authors.affiliation: Department of Chemistry, Materials and Engineering Chemistry, Politecnico di Milano, Milan, Italy.
authors.forename: Martha Elena
authors.initials: ME
authors.lastname: Mendieta
authors.forename: Paolo
authors.initials: P
authors.lastname: Antonioli
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Righetti
authors.forename: Attilio
authors.initials: A
authors.lastname: Citterio
authors.forename: Stephanie
authors.initials: S
authors.lastname: Descroix
authors.forename: Roberto
authors.initials: R
authors.lastname: Sebastiano
mesh_terms: D001464:Barium / Q000737:chemistry; D001881:Borates / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000737:chemistry; D002413:Cations, Divalent / Q000737:chemistry; D045304:Cytochromes c / Q000737:chemistry; D053841:Electroosmosis; D019075:Electrophoresis, Capillary / Q000379:methods*; D008956:Models, Chemical; D010446:Peptide Fragments / Q000302:isolation & purification*; D014357:Trypsin / Q000378:metabolism*
chemical_list: D001881:Borates; D002413:Cations, Divalent; D010446:Peptide Fragments; D001464:Barium; C021755:tetraborate; D045304:Cytochromes c; D014357:Trypsin; D002256:Carbonic Anhydrases