caa a22 4500 475744195 CHVBK 20180406123508.0 cr unu---uuuuu 170329e20000401xx s 000 0 eng 10.1023/A:1007064021743 doi (NATIONALLICENCE)springer-10.1023/A:1007064021743 Use of the pH Memory Effect in Lyophilized Proteins to Achieve Preferential Methylation of α-Amino Groups [Elektronische Daten] [Helen Vakos, Harvey Kaplan, Bruce Black, Brian Dawson, Mary Hefford] It is demonstrated that the pH memory effect can be used to control the ionization state of amino groups in lyophilized proteins and hence their chemical reactivity toward modifying reagents. When proteins were lyophilized from aqueous solutions at pH values between 6 and 7 and reacted in vacuo with iodomethane, the α-amino groups were found to be either preferentially or selectively trimethylated. Reaction with 13C-labeled iodomethane permitted detection and identification of individual trimethylated α-amino groups by 13C-NMR spectroscopy as distinct peaks in the spectral region between 52 and 57 ppm. There was adequate sensitivity to detect minor resonances of free α-amino groups arising from proteolysis of the major protein or from protein impurities. The resonances of the trimethylated α-amino groups in standard amino acids and peptides are sufficiently close to those in the derivatized protein to make a tentative identification of the N-terminal amino acid. It is also demonstrated that advantage can be taken of the pH memory effect to use the preferential 13C-methylation of amino groups to verify whether a protein has a free or blocked amino terminus. Plenum Publishing Corporation, 2000 α-Amino groups nationallicence methylation of amino groups nationallicence protein methylation nationallicence pH memory nationallicence criteria of protein homogeneity nationallicence 13C-nuclear magnetic resonance spectroscopy of proteins nationallicence Vakos Helen Department of Chemistry, University of Ottawa, K1N 6N5, Ottawa, Ontario, Canada aut Kaplan Harvey Department of Chemistry, University of Ottawa, K1N 6N5, Ottawa, Ontario, Canada aut Black Bruce Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut Dawson Brian Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut Hefford Mary Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut Journal of Protein Chemistry Kluwer Academic Publishers-Plenum Publishers 19/3(2000-04-01), 231-237 0277-8033 19:3<231 2000 19 10930 https://doi.org/10.1023/A:1007064021743 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1007064021743 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Vakos Helen Department of Chemistry, University of Ottawa, K1N 6N5, Ottawa, Ontario, Canada aut NATIONALLICENCE 700 1- Kaplan Harvey Department of Chemistry, University of Ottawa, K1N 6N5, Ottawa, Ontario, Canada aut NATIONALLICENCE 700 1- Black Bruce Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut NATIONALLICENCE 700 1- Dawson Brian Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut NATIONALLICENCE 700 1- Hefford Mary Therapeutic Products Programme, Bureau of Biologics and Radiopharmaceuticals, Research Services Division, Health Canada, K1A 0L2, Ottawa, Ontario, Canada aut NATIONALLICENCE 773 0- Journal of Protein Chemistry Kluwer Academic Publishers-Plenum Publishers 19/3(2000-04-01), 231-237 0277-8033 19:3<231 2000 19 10930 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer