Dear Juri,
Guanidine function of Arg and pentamethylguanidine were reported to have
pKa values 12.6 and 13.8 respectively. Therefore, dimethylation should
slightly increase basicity of Arg side chain and pI value of the related
protein. But you will be able to differentiate the dimethylated protein
only at pH above 12 or so, which is not very useful. In the normal pH
range both forms of Arg side-chains will be totally protonated.
Dimethylation could be easily detected by MS, but I'm not an expert in
this field.
Regards,
Igor
------------------------------------------------
Igor L. Rodionov
Laboratory of Peptide Chemistry
Branch of Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry
Pushchino, Moscow Region
142292, Russian Federation
E-mail: <rodionov@fibkh.serpukhov.su
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