[1] Roche Biosci, Dept Genet & Genome, Palo Alto, CA 94303 USA
[2] Roche Mol Syst, Alameda, CA 94501 USA
[3] Stanford Univ, Dept Chem, Stanford, CA 94305 USA
[4] Oregon Hlth Sci Univ, Portland, OR 97201 USA
[5] Portland Vet Affairs Med Ctr, Portland, OR 97201 USA