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Document Type:Latin Dissertation
Language of Document:English
Record Number:55747
Doc. No:TL25701
Call number:‭NR23131‬
Main Entry:Mahmoud Mohammad Yassine
Title & Author:Protein separations in capillary zone electrophoresis using cationic surfactant coatingsMahmoud Mohammad Yassine
College:University of Alberta (Canada)
Date:2006
Degree:Ph.D.
student score:2006
Page No:202
Abstract:Capillary electrophoresis (CE) is a separation technique based on the differential migration of charged species in an electric field. The separation of proteins is not always possible since they tend to adsorb onto the capillary surface. Herein, cationic surfactants are employed to improve cationic protein separations in a simple and inexpensive way. Surfactants such as didodecyldimethylammonium bromide (DDAB) adsorb onto fused silica capillaries to form semi-permanent bilayer coatings. However, initially such coatings had to be regenerated between runs to maintain efficiency and reproducibility. My studies demonstrate that reducing the capillary diameter and the volume of buffer flushed through the capillary enhance the coating stability. Chemical factors such as ionic strength and nature of the buffer anion, which decrease the critical micelle concentration (cmc) of the surfactant, improve the coating stability. The stability of the surfactant coating can also be increased with increasing the hydrophobicity of the surfactant monomers (i.e., increasing chain length and decreasing cmc). Over 60 successive separations were performed on a dimethyldioctadecylammonium bromide (2C18DAB) coated capillary over a 12-day period, without any regeneration of the coating. The separation efficiencies for four model cationic proteins ranged from 1.2-1.4 million plates/m for the dimethylditetradecylammonium bromide (2C14DAB) coating to 0.3-0.4 million plates/m for the 2C18DAB coating. The enhanced stability of the surfactant coatings made possible their use to separate proteins at preparative scale levels using wide bore capillaries. At protein concentrations greater than 1 g/L, electromigration dispersion became the dominant source of band broadening, and the peak shape distorted to triangular fronting. Matching of the mobility of the buffer co-ion to that of the analyte resulted in dramatic improvements in the peak shapes at preparative scales. The maximum sample loading capacity of 160 picomoles of each protein was achieved in a single run with a 100 μm-2C14DAB coated capillary. Finally, off-line coupling of preparative CE with the microwave-assisted acid hydrolysis (MAAH) for protein characterization was described. The protein separations and characterization were performed within an hour. Furthermore, the amino acid sequence of the protein can be read directly from one spectrum. The peptide sequence coverage achieved by CE/MAAH was 95%.
Subject:Pure sciences; Capillary zone electrophoresis; Cationic; Coatings; Protein separations; Surfactants; Analytical chemistry; 0486:Analytical chemistry
Added Entry:University of Alberta (Canada)