[M+4] and higher carbon isotopes

[M+4] and higher carbon isotopes Tobi  2019-03-22

Dear Skyline Team,

in the target list, the number of natural carbon isotopes [M+X] for each charge of a peptide can be nicely set via Settings/Transition Settings/Full-Scan/Peaks.

While changing the value between 1 and 4 (Precursor to M+3) the isotopes in the target list follow exactly, but any input value higher than 4 will result at maximum in [M+3]. Am I doing something wrong or is it limited?

Just in case it is limited, could you think of increasing the limit since this feature is automatic and fast and easy to control?

Looking forward to get a short comment for your side, and thanks for the great software.


Brendan MacLean responded:  2019-03-24

Hi Tobi,
It is limited to including only isotopes expected to have at least 1% of the total distribution. If you are limited to M+3, then that means that M+4 is expected to have <1% of the total distribution. To go beyond this, you would need to be working with larger molecules, as in the MS1 filtering tutorial on page 30 where M+7 is shown:


Hope this helps.


Tobi responded:  2019-03-24

Thank you very much for the fast explanation, it works as you say.

Best regards,