I use a Maldi-Tof spectrometer. Yes N means the expected molecular mass of
the fragment. The cleavage is not specific; I want to define the specificity
of the enzyme by using synthetic peptide as substrate. The peptide was
dissolved in DMSO and dilute in buffer for the digest. I found some peaks
corresponding to oxidation of Methionine amino acids. However, I can
understand the mass difference of -60.7 Da. could this difference explain by
a remaining protection group used during peptide synthes?
Luc
> Hiyas,
>
> What MS method did you use ? Does N correspond to the expected molecular
> mass of any kind of a fragment ? What cleavage methods did you use ?
> (Your fragments may very well be all chemically modified, and then the
> N-60.7 would be a small fraction of the unmodified peptide fragment).
> List all the chemicals that have come in contact with your peptide.
>
> If you provide more details, we might be able to help you better.
>
> A.
>> Hi
>>
>> I have a synthetic peptide of 28 AA's. I run different cleavage and then
>> separation of the resulting fragments on reverse phase HPLC in H2O/CH3CN
>> gradient including 0.1%TFA. Then the fractions were lyophilized.
>> When I run the mass spect, I found some fragments showing a doublet at mass N
>> for the major peaks and N -60.7 for the minor peaks. What could this -60.7
>> be?
>>
>> Does anyone have any explanation about this -60.7?
>>
>>
>> Thanks in advance
>>
>> Luc CAMOIN
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