title: Mass distribution, polydispersity and focusing properties of carrier ampholytes for IEF. III: pH 2.5-4 intervals.
abstract: To study the molecular mass distribution and number of species in narrow-range (2-pH-unit wide, in the nominal pI 2-4 or 3-5 interval) carrier ampholytes from four commercial sources (Bio-Lyte, Servalyt, Ampholine and Pharmalyte), a 2-D technique was adopted, consisting of a preparative focusing step in a Rotofor instrument, followed by analysis of every other collected fraction (10 out of 20) by CE-MS. It was found that Ampholine pH 3.5-5 contains 105 different molecular mass (M(r)) compounds, in the M(r) interval 205-965 Da, for a total of 446 isoforms. Bio-Lyte pH 3-5 consists of 84 different M(r) species, in the M(r) range 216-965 Da, for a total of 383 isoforms. Servalyt pH 2-4 is made of 227 different M(r) compounds, in the M(r) interval 204-929 Da, for a total of 1201 isoforms. Pharmalyte pH 2.5-5 comprises 245 amphoteres, in the M(r) range 203-857 Da, for a total of 857 isoforms. Pharmalyte appears to be the best brand, with the vast majority of species focusing sharply at their pI position and almost no 'poor' species, distributed along the entire pH gradient, denoting an extremely shallow pH/mobility curve across the pI value. Due to some overlap with the adjacent acidic pH 4-6 interval, the species in common have been evaluated: the most extended overlaps are found in Ampholine (55% of the species appearing in the two neighbouring intervals) and in Servalyt (47% coincidence). The lowest overlaps are found in Pharmalyte (23%) and in Bio-Lyte (20%).
authors.affiliation: Politecnico di Milano, Department of Chemistry, Materials and Engineering Chemistry Giulio Natta, Milano, Italy.
authors.forename: Carolina
authors.initials: C
authors.lastname: Simó
authors.forename: Martha Elena
authors.initials: ME
authors.lastname: Mendieta
authors.forename: Paolo
authors.initials: P
authors.lastname: Antonioli
authors.forename: Roberto
authors.initials: R
authors.lastname: Sebastiano
authors.forename: Attilio
authors.initials: A
authors.lastname: Citterio
authors.forename: Alejandro
authors.initials: A
authors.lastname: Cifuentes
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Righetti
mesh_terms: D000665:Ampholyte Mixtures / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing / Q000379:methods; D008970:Molecular Weight; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D000665:Ampholyte Mixtures