[BiO BB] A question about BLOSUM matrices

[J Kalita]

Hello,

I have a question about BLOSUM matrices such as the one you see
on the Web page at
http://eta.embl-heidelberg.de:8000/misc/mat/blosum80.html.
Can anyone please explain to me what the last four columns and last four
rows labeled "B", "Z", "X" and "*" are?

Thank you!

Jugal Kalita
Computer Science Department
University of Colorado at Colorado Springs