title: OFF/ON Red-Emitting Fluorescent Probes for Casein Recognition and Quantification Based on Indolium Derivatives.
abstract: Five derivatives of 2, 3, 3-trimethyl-3H-indolium containing different electron donor groups (H1 - H5) were synthesized for the determination of proteins. H3, a sensitive red-emitting fluorescent probe, was found for the discrimination of hydrophobic proteins from hydrophilic. The OFF - ON fluorescence switch of H3 was caused by the formation of twisted intramolecular charge-transfer (TICT) state when it combined with hydrophobic proteins in aqueous buffer. There was a good linear relationship between the emission intensity of H3 and the casein concentration (r = 0.9989). Based on this, a novel casein quantitative assay method was developed, and the method was applied to determinate casein in milk powder samples. Successfully, the results were in good agreement with Biuret method. In addition, a simple and sensitive method was established to differentiate and quantify three casein components (α-, β-, and κ-casein) due to their much different binding constants to H3 probe.
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China.
authors.forename: Chunlin
authors.initials: C
authors.lastname: Liu
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Gao
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China.
authors.forename: Jinya
authors.initials: J
authors.lastname: Du
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Shen
authors.affiliation: College of Biological and Pharmaceutical Science, China Three Gorges University, Yichang, 443002, People's Republic of China. changying.yang@ctgu.edu.cn.
authors.forename: Changying
authors.initials: C
authors.lastname: Yang
mesh_terms: D000818:Animals; D002364:Caseins / Q000032:analysis*; D005456:Fluorescent Dyes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D002364:Caseins; D005456:Fluorescent Dyes; D007211:Indoles
keywords: Casein; Discrimination; Fluorescent probes; Hydrophobic protein; Quantification; Red-emitting