title: Analysis of the interferences in quantitation of a site-specifically PEGylated exendin-4 analog by the Bradford method.
abstract: Protein modification has been found to affect the estimation of protein concentration in some of the traditional dye-based absorbance measurements. In this work, a distinct reduction in A595 was observed during the quantitation of a PEGylated exendin-4 analogue (Ex4C) by the Bradford method and the PEGylation process was found to interfere with the measurement. Lys(12), Arg(20), and Lys(27) were further proved to be the major amino acids that functioned as dye-binding sites. The shielding effect produced by the large polymer was demonstrated to depend on the length of PEG that was used for modification.
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Xiaowei
authors: X
authors: Qian
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Hongxia
authors: H
authors: Dong
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Xiaojing
authors: X
authors: Hu
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Hong
authors: H
authors: Tian
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Linfeng
authors: L
authors: Guo
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China.
authors: Qingliang
authors: Q
authors: Shen
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China. Electronic address: xdgao@cpu.edn.cn.
authors: Xiangdong
authors: X
authors: Gao
authors: Department of Biochemistry, China Pharmaceutical University, Nanjing 210009, China. Electronic address: wbyao@cpu.edu.cn.
authors: Wenbing
authors: W
authors: Yao
mesh_terms: D000077270:Exenatide; D006801:Humans; D010455:Peptides / Q000032:analysis* / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D014688:Venoms / Q000032:analysis* / Q000737:chemistry*
chemical_list: D010455:Peptides; D014688:Venoms; D011092:Polyethylene Glycols; D000077270:Exenatide
keywords: Bradford method; Exendin-4; Interference; PEGylation; Protein concentration; Shielding effect