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. 2018 Apr 12;29(6):1273–1283. doi: 10.1007/s13361-018-1931-0

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© This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2018

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Modification of carboxylic acid on D (aspartic acid) and E (glutamic acid). Acidic amino acids, together with protein C-terminal, are derivatized by ethyl esterification. D or E are also modified by ethylenediamine (EDA) amidation