Copy or type amino acid sequence of a protein, choose necessary items in "options" and push button "Calculate!". Brutto formula and length of the protein are calculated always (independently of items you have chosen). For calculation of molecular weight of isotop content protein it is nessesary to mark isotopes in "isotop composition" (one or more). Three-letter code may be converted in one-letter by program "Three- / one-letter code for amino acids". For translation of nucleic acid sequence you can use program "6 Frame Translation".