The scientific name for the tobacco mosaic virus:
Acetyl_seryl_tyrosyl_seryl_isoleucyl_threonyl_seryl_prolyl_ser
 yl_glutaminyl_phenyl_alanyl_valyl_phenyl_alanyl_leucyl_seryl_s
 eryl_valyl_tryptophyl_alanyl_aspartyl_prolyl_isoleucyl_glutamy
 l_leucyl_leucyl_asparaginyl_valyl_cysteinyl_threonyl_seryl_ser
 yl_leucyl_glycyl_asparaginyl_glutaminyl_phenyl_alanyl_glutamin
 yl_threonyl_glutaminyl_glutaminyl_alanyl_arginyl_threonyl_thre
 onyl_glutaminyl_valyl_glutaminyl_glutaminyl_phenyl_alanyl_sery
 l_glutaminyl_valyl_tryptophyl_lysyl_prolyl_phenyl_alanyl_proly
 _lglutaminyl_seryl_threonyl_valyl_arginyl_phenyl_alanyl_prolyl
 _glycyl_aspartyl_valyl_tyrosyl_lysyl_valyl_tyrosyl_arginyl_tyr
 osyl_asparaginyl_alanyl_valyl_leucyl_aspartyl_prolyl_leucyl_is
 oleucyl_threonyl_alanyl_leucyl_leucyl_glycyl_threonyl_phenyl_a
 lanyl_aspartyl_threonyl_arginyl_asparaginyl_arginyl_isoleucyl_
 isoleucyl_glutamyl_valyl_glutamyl_asparaginyl_glutaminyl_gluta
 minyl_seryl_prolyl_threonyl_threonyl_alanyl_glutamyl_threonyl_
 leucyl_aspartyl_alanyl_threonyl_arginyl_arginyl_valyl_aspartyl
 _aspartyl_alanyl_threonyl_valyl_alanyl_isoleucyl_arginyl_seryl
 _alanyl_asparaginyl_isoleucyl_asparaginyl_leucyl_valyl_asparag
 inyl_glutamyl_leucyl_valyl_arginyl_glycyl_threonyl_glycyl_leuc
 yl_tyrosyl_asparaginyl_glutaminyl_asparaginyl_threonyl_phenyl_
 alanyl_glutamyl_seryl_methionyl_seryl_glycyl_leucyl_valyl_tryp
 tophyl_threonyl_seryl_alanyl_prolyl_alanyl_serine 
It has 1,909 letters and is probably impossible to say.
http://www.wikipedia.org/wiki/Acetylseryltyrosylserylisol...serineEdit: ****! Wrong forum!