title: Effect of mechanical denaturation on surface free energy of protein powders.
abstract: Globular proteins are important both as therapeutic agents and excipients. However, their fragile native conformations can be denatured during pharmaceutical processing, which leads to modification of the surface energy of their powders and hence their performance. Lyophilized powders of hen egg-white lysozyme and β-galactosidase from Aspergillus oryzae were used as models to study the effects of mechanical denaturation on the surface energies of basic and acidic protein powders, respectively. Their mechanical denaturation upon milling was confirmed by the absence of their thermal unfolding transition phases and by the changes in their secondary and tertiary structures. Inverse gas chromatography detected differences between both unprocessed protein powders and the changes induced by their mechanical denaturation. The surfaces of the acidic and basic protein powders were relatively basic, however the surface acidity of β-galactosidase was higher than that of lysozyme. Also, the surface of β-galactosidase powder had a higher dispersive energy compared to lysozyme. The mechanical denaturation decreased the dispersive energy and the basicity of the surfaces of both protein powders. The amino acid composition and molecular conformation of the proteins explained the surface energy data measured by inverse gas chromatography. The biological activity of mechanically denatured protein powders can either be reversible (lysozyme) or irreversible (β-galactosidase) upon hydration. Our surface data can be exploited to understand and predict the performance of protein powders within pharmaceutical dosage forms.
authors.affiliation: School of Pharmacy, University of Bradford, Bradford, BD7 1DP, UK; Faculty of Pharmacy, University of Damascus, Damascus, Syria. Electronic address: m.a.mohammad7@bradford.ac.uk.
authors.forename: Mohammad Amin
authors.initials: MA
authors.lastname: Mohammad
authors.affiliation: School of Pharmacy, University of Bradford, Bradford, BD7 1DP, UK. Electronic address: i.m.grimsey@bradford.ac.uk.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Grimsey
authors.affiliation: School of Pharmacy, University of Bradford, Bradford, BD7 1DP, UK; School of Pharmacy and Biological Sciences, University of Central Lancashire, PR1 2HE, UK. Electronic address: r.t.forbes@bradford.ac.uk.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Forbes
authors.affiliation: Department of Pharmacy and Pharmacology, University of Bath, Bath BA2 7AY, UK. Electronic address: prsisb@bath.ac.uk.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Blagbrough
authors.affiliation: Department of Pharmacy, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK. Electronic address: b.r.conway@hud.ac.uk.
authors.forename: Barbara R
authors.initials: BR
authors.lastname: Conway
mesh_terms: D000818:Animals; D002645:Chickens; D002849:Chromatography, Gas; D009113:Muramidase / Q000737:chemistry; D011489:Protein Denaturation; D013499:Surface Properties; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: C421864:hen egg lysozyme; D009113:Muramidase; D001616:beta-Galactosidase
keywords: Conformational change; Inverse gas chromatography; Lysozyme; Protein denaturation; Surface free energy; β-Galactosidase