Fragmentation stability and retention time-shift obtained by LC-MS/MS to distinguish sialylated N-glycan linkage isomers in therapeutic glycoproteins / 药物分析学报

Sialylated N-glycan isomers with α2-3 or 42-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cyto-toxic T lymphocyte-associated antigen-4-immunoglobulin(CTLA4-Ig),were produced in Chinese ham-ster ovary cell lines:however,their linkage isomers have not been reported.In this study,N-glycans of CTLA4-Igs were released,labeled with procainamide,and analyzed by liquid chromatography-tandem mass spectrometry(MS/MS)to identify and quantify sialylated N-glycan linkage isomers.The linkage isomers were distinguished by comparison of 1)intensity of the N-acetylglucosamine ion to the sialic acid ion(Ln/Nn)using different fragmentation stability in MS/MS spectra and 2)retention time-shift for a selective m/z value in the extracted ion chromatogram.Each isomer was distinctively identified,and each quantity(＞0.1％)was obtained relative to the total N-glycans(100％)for all observed ionization states.Twenty sialylated N-glycan isomers with only α2-3 linkage(s)in WT were identified,and each isomer's sum of quantities was 50.4％.Furthermore,39 sialylated N-glycan isomers(58.8％)in mono-(3 N-glycans;0.9％),bi-(18;48.3％),tri-(14;8.9％),and tetra-(4;0.7％)antennary structures of mutant were obtained,which comprised mono-(15 N-glycans;25.4％),di-(15;28.4％),tri-(8;4.8％),and tetra-(1;0.2％)sialy-lation,respectively,with only α2-3(10 N-glycans;4.8％),both α2-3 and α2-6(14;18.4％),and only α2-6(15;35.6％)linkage(s).These results are consistent with those for α2-3 neuraminidase-treated N-glycans.This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.

Discussion of E-leaning / 中华医学教育探索杂志

In this article,we analyzed E-leaning's characteristics and trend of development,and then we put forward an opinion that in such situation students should have a capacity of making use of network to have autonomous study without the limit of time and space,and at the same time teachers also should use the information technology to train students' capacity of evaluating and processing information,in order to be able to conduct the self-management learning through the network.