title: Investigation into the mechanism of (-)-epigallocatechin-3-gallate-induced precipitation of insulin.
abstract: The molecular interactions between EGCG and insulin were investigated to probe the mechanism of EGCG-induced insulin precipitation. The results indicated that 1-5mM EGCG induced insulin into reversible globular precipitates of 185-365 nm. The formation of precipitates was facilitated at high salt concentration and pH values close to insulin's isoelectric point, indicating that hydrophobic interaction was the main driving force. The precipitation was positively related to insulin concentration, but for EGCG, there was a suitable concentration (2 mM at 2 mg/mL of insulin) at which the precipitate content reached maximum. Mass spectroscopy analysis indicated that EGCG formed clusters in the aqueous solution and the clusters correlate with the insulin precipitation. Based on extensive investigation, a physical model was proposed to explain the molecular interactions between EGCG and insulin. Namely, EGCG monomers and clusters first bound to insulin dimers via hydrophobic interaction, leading to the reduction of the thickness of the hydration layer and the partial denaturation of insulin. Then, EGCG clusters acted as bridges to induce the aggregation and precipitation of insulin.
authors.affiliation: Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Shi-Hui
authors.initials: SH
authors.lastname: Wang
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Dong
authors.forename: Yan
authors.initials: Y
authors.lastname: Sun
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D011485:Protein Binding; D012492:Salts / Q000737:chemistry; D012995:Solubility; D012996:Solutions / Q000737:chemistry
chemical_list: D007328:Insulin; D012492:Salts; D012996:Solutions; D002392:Catechin; C045651:epigallocatechin gallate