NeuGc

[Chia-wei Lin]

Dear developer, 

Thanksf for developing this nice tool.

We are using GlyResoft for samples containing NeuGc. When I use the default Mammalian database, the software generates structures with NeuGc; however, the theoretical masses are not as expected. The calculated theoretical mass of permethylated glycans is consistently 14 Da lower. For example, the theoretical mass of Hex4HexNAc3NeuGc should be 1988 Da, but the software reports 1978 Da. I checked several structures, and only those containing NeuGc show this 14‑Da mass difference. I am not sure why this occurs for NeuGc-containing structures. Is there a specific reason for this behavior? Thanks. 

Best,

Chia-Wei

[Joshua Klein]

Thank you for your interest in my work. I suspect the problem is that when I developed the procedure for applying derivatization to substituent groups, I did not have an example with NeuGc, otherwise the process I came up with wouldn't have sufficed.

This is NeuAc. I know that when you permethylate it, the N-acetyl also carries an extra methyl group.

This is NeuGc:

Compared to N-acetyl, the N-glycolyl group has an extra hydroxyl group that would also pick up a second methyl group. Is that accurate?

If so, this is a deeper issue and I will probably need some time to verify my solution.

Thank you,

Joshua Klein

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Joshua Klein