superimposing molecules

[Gregory King]

Greetings,

I'm looking for software (or an explanation of an efficient algorithm) that
will superimpose molecule A onto molecule B with a combination of translations
and rotations, and using a minimal rms deviation as the convergence criterion.
There is a known one-to-one correspondence between the relevant atoms in both
molecules (I'll be comparing peptides, and using the backbone atoms as the
relevant ones).

Thanks in advance.

Greg King
gking at arserrc.gov