Molecular Weight Calculator for Proteins

klaus_frommerr at my-deja.com klaus_frommerr at my-deja.com
Sat Jun 19 10:27:07 EST 1999


I'm looking for a software tool that is able to calculate the molecular
weight of a protein based on its amino acid sequence. I know about the
rough rule assuming 110 g/mol per amino acid, but knowing the AA
sequence it IS possible to calculate the exact molecular weight, it's
just a laborious thing if you have a large protein with many amino
acids. I have a freeware tool called "Molecular Weight Calculator" by
Matthew Monroe (http://unc.edu/~monroem)/), which is able to calculate
the MW (molecular weight) of amino acids by entering them in their
three-letter code. For example you can type GlyPheAspHis... and it will
calculate the MW of the sum of these amino acids. It does not take
peptide bonds into account, so in case of a protein you will manually
have to subtract the MW of (n-1) H2O molecules (with n as the number of
amino acids).
That's not a lot of work but the problem is something else: I usually
have the amino acid sequence in its one-letter code. And changing all
the one-letter code to the three-letter code is a lot of work in case of
a large protein.
I can well imagine that it would be easy to create a program calculating
the MW of a protein based on its AA sequence in one-letter code. Just
tell the program what numerical values the different letters stand for
and tell it to subtract the MW of (n-1) H2O molecules from the sum of
these values. But since I don't know any programming language this is no
option for me.
Does anybody know about such a program? Is it available from the

Klaus Frommer

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