Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Primer
  • Published:

Where did the BLOSUM62 alignment score matrix come from?

Many sequence alignment programs use the BLOSUM62 score matrix to score pairs of aligned residues. Where did BLOSUM62 come from?

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

References

  1. Henikoff, J.G. Amino acid substitution matrices from protein blocks. Proc. Natl. Acad. Sci. USA 89, 10915–10919 (1992).

    Article  CAS  Google Scholar 

  2. Karlin, S. & Altschul, S.F. Methods for assessing the statistical significance of molecular sequence features by using general scoring schemes. Proc. Natl. Acad. Sci. USA 87, 2264–2268 (1990).

    Article  CAS  Google Scholar 

  3. Altschul, S.F. Amino acid substitution matrices from an information theoretic perspective. J. Mol. Biol. 219, 555–565 (1991).

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Supplementary information

Supplementary Notes

A program for taking a (possibly arbitrary) alignment score matrix and back-calculating the implied target frequencies pab. (DOC 81 kb)

Doing this requires solving for a nonzero lambda in: \sum_ab f_a f_b e{\lambda s_ab} = 1 and this is a good excuse to demo two methods of root-finding: bisection search and the Newton/Raphson method.

The program is ANSI C, and should compile on any machine with a C compiler: % cc -o lambda lambda.c -lm Any questions about this program should be addressed directly to the author.

Further study

Further study

You can download an ANSI C program for calculating the implicit target frequencies pab of a score matrix (see Supplementary Notes). The BLOSUM62 score matrix and its background frequencies are included as an example. The code also contains two basic methods of solving for roots of equations like the one for λ: the bisection method, and the Newton/Raphson method.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Eddy, S. Where did the BLOSUM62 alignment score matrix come from?. Nat Biotechnol 22, 1035–1036 (2004). https://doi.org/10.1038/nbt0804-1035

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1038/nbt0804-1035

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing