Synthesis Of PDMA-b-PEO-b-PDMA And Its Application For Separation Of Proteins By Ce

Capillary electrophoresis (CE), which offers high separation efficiency, less sample and reagent consumption and short analysis time, has emerged as a powerful analytical method for separation of biomacromolecules, such as peptides, proteins, DNA and nucleic acids. However, the separation of proteins is complicated for their tendency to adsorb onto the negatively charged surface of fused silica capillaries, and this is particularly true for the separation of basic proteins. The adsorption will seriously damage separation efficiency. Firstly, adsorption causes tailing of the sample peak, which leads to loss of resolution and sensitivity. Secondly it will change theζ-potential of the capillary which affects the electroosmotic flow (EOF) rate, giving improper migration times and poor repeatability. Also theζ-potential caused by local adsorption of proteins causes additional peak broadening.In order to minimize protein adsorption and stabilize EOF, numerous approaches have been explored, including the use of extreme pH, high ionic strength and zwitterionic additives. However, the most common approach has been to coat the capillary wall, and the major objective of capillary coating is to modify or mask the silanol groups on the capillary surface by presenting a more inert surface. Nowadays, polymer coatings for capillary become more popular, in which the capillary can be modified with polymers by covalent bond or physical adsorption. However, the procedures employed to prepare a covalent coating are laborious and time consuming. Physically adsorbed coating becomes more attractive due to its fast coating procedure and reproducibility. Several polymers such as poly (N, N-dimethylacrylamide) (PDMA), poly (vinyl alcohol) (PVA), polyethyleneimine (PEI), poly (ethylene oxide) (PEO) and poly (N-hydroxy- ethylacrylamide) (PHEA) performed as physical adsorbed coatings can reduce wall-protein interaction and effectively control the EOF.In this paper, a range of well-defined triblock copolymer, poly (N, N-dimethylacrylamide)-block-poly (ethylene oxide)-block-poly (N, N-dimethylacryl- amide) (PDMA-b-PEO-b-PDMA) was synthesized by atom transfer radical polymerization (ATRP), which was used as physical coating of capillaries for proteins separation. Work was on the following aspects:1. A series of copolymers of PDMA-b-PEO-b-PDMA was synthesized with different relative molecular mass of PDMA, and characterized by 1H NMR and GPC; 2. Copolymers of PDMA-b-PEO-b-PDMA were used as physical coating of CE for proteins separation. The effect of relative molecular mass of PDMA of copolymers, pH value and structure of copolymers on proteins separation was studied;3. The influence of pH value on the EOF of PDMA-b-PEO-b-PDMA coated capillary, PEO coated capillary and bare capillary were investigated. The variation of EOF can be used as a measure of the protein adsorption. By comparing the EOF of bare capillary with PDMA-b-PEO-b-PDMA coated capillary, the PDMA-b-PEO- b-PDMA coating showed good ability on minimizing protein adsorption and stabilizing EOF.