▁and ▁b - ion ▁series , ▁assign ▁the ▁am ino ▁acid ▁sequence ▁and ▁check ▁the ▁mass . ▁The ▁other ▁method ▁is ▁to ▁identify ▁b - ions ▁first ▁and ▁then ▁find ▁the ▁corresponding ▁y - ions . ▁ ▁Alg orithms ▁and ▁software ▁Man ual ▁de ▁nov o ▁sequ encing ▁is ▁labor - int ensive ▁and ▁time ▁cons uming . ▁Usually ▁algorithms ▁or ▁programs ▁come ▁with ▁the ▁mass ▁spect rom eter ▁instrument ▁are ▁applied ▁for ▁the ▁interpretation ▁of ▁spect ra . ▁ ▁Development ▁of ▁de ▁nov o ▁sequ encing ▁algorithms ▁An ▁old ▁method ▁is ▁to ▁list ▁all ▁possible ▁pe pt ides ▁for ▁the ▁prec ursor ▁ion ▁in ▁mass ▁spectrum , ▁and ▁match ▁the ▁mass ▁spectrum ▁for ▁each ▁candidate ▁to ▁the ▁experimental ▁spectrum . ▁The ▁possible ▁pe pt ide ▁that ▁has ▁the ▁most ▁similar ▁spectrum ▁will ▁have ▁the ▁highest ▁chance ▁to ▁be ▁the ▁right ▁sequence . ▁However , ▁the ▁number ▁of ▁possible ▁pe pt ides ▁may ▁be ▁large . ▁For ▁example , ▁a ▁prec ursor ▁pe pt ide ▁with ▁a ▁mole cular ▁weight ▁of ▁ 7 7 4 ▁has ▁ 2 1 , 9 0 9 , 0 4 6 ▁possible ▁pe pt ides . ▁Even ▁though ▁it ▁is ▁done ▁in ▁the ▁computer , ▁it ▁takes ▁a ▁long ▁time . ▁ ▁Another ▁method ▁is ▁called ▁“ sub sequ encing ”, ▁which ▁instead ▁of ▁listing ▁whole ▁sequence ▁of ▁possible ▁pe pt ides , ▁matches ▁short ▁sequences ▁of ▁pe pt ides ▁that ▁represent ▁only ▁a ▁part ▁of ▁the ▁complete ▁pe pt ide . ▁When ▁sequences ▁that ▁highly ▁match