title: Characterization of a 19 kDa alpha-zein of high purity.
abstract: A highly pure alpha-zein was extracted from corn flour using ethanol (95%). Subsequently, ion-exchange chromatography was performed, using SP-Sepharose that yielded a highly homogeneous protein. This protein migrated as a single band in 20% SDS-PAGE and in pH gradient gels, showing an isoelectric point of 6.8. Mass spectrometry (MALDI-TOF-MS) showed a single peak with a molecular mass of 24 535 Da. It was identified as Z19, when comparing the sequence obtained in an automatic Edman sequencer with the Swissprot database using BLAST. The molar extinction coefficient, determined by dry weight in 70% methanol, was 12 415.49 M(-1) cm(-1) at 280 nm. Light scattering showed its presence in a monodispersed state of 44-66 kDa aggregates in methanol (70%). Circular dichroism spectra allowed the estimation of an alpha-helix content that was lower than the one found for a mixture of two alpha-zeins but with a higher content of beta sheets.
authors.affiliation: Departamento de Alimentos y Biotecnología, Facultad de Química, Instituto de Química, Universidad Nacional Autónoma de México, 04510 México D. F.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Cabra
authors.forename: Roberto
authors.initials: R
authors.lastname: Arreguin
authors.forename: Amanda
authors.initials: A
authors.lastname: Galvez
authors.forename: Maricarmen
authors.initials: M
authors.lastname: Quirasco
authors.forename: Rafael
authors.initials: R
authors.lastname: Vazquez-Duhalt
authors.forename: Amelia
authors.initials: A
authors.lastname: Farres
mesh_terms: D000595:Amino Acid Sequence; D002852:Chromatography, Ion Exchange; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D005433:Flour / Q000032:analysis; D008027:Light; D008969:Molecular Sequence Data; D012542:Scattering, Radiation; D020539:Sequence Analysis, Protein; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D003313:Zea mays / Q000737:chemistry*; D015028:Zein / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D015028:Zein