I am looking for an R package preferably Bioconductor that will compute the theoretical isotope spectra given the amino acid sequence. For example

AYARATAYT

should return these details.

Most likely isotope combination: 12C44 1H66 14N12 16O14 Exact mass is 986.482 Probability of combination is 56.118%

• 986.48 1.000000000
• 987.48 0.552510687
• 988.48 0.177857196
• 989.48 0.042054957
• 990.48 0.008026484 etc

another example where the major isotope is [M+1]/Z

AYARATAYTRYTNNPPY

Most likely isotope combination: 12C89 13C1 1H129 14N25 16O27 Exact mass is 1992.952 Probability of combination is 31.025%

• 1991.95 0.884750727
• 1992.95 1.000000000
• 1993.95 0.607872385
• 1994.95 0.261239673
• 1995.95 0.088463730
• 1996.95 0.025004454 etc

It would also be great if we could return isotope distributions for label incoperation could also be supported such as 15N or 2H. I'm sure a good package must exist somewhere.

• In section Working with peptide sequences in the RforProteomics vignette, I used OrgMassSpecR to calculate the the isotope distributions for different 15N incorportations.
• Otherwise, the BRAIN package might be useful: Baffling Recursive Algorithm for Isotope distributioN calculations.
• Finally, the camera package has a vignette about Isotope pattern validation with CAMERA.

OrgMassSpecR seems to have the required code in IsotopicDistributionHDX.R, seems worth slightly rewriting to make it a little more general. Thanks Laurent