Chemical/biochemical pocket companion designed by the editors of Current Protocols. Type in or copy/paste any nucleic acid base sequence, any protein or peptide amino acid sequence (in one- or three-letter codes accessible from a convenient menu), or any standard chemical formula, and obtain the molecular weight. Allows estimates of the molecular weights of unknown nucleic acid or protein/peptide sequences on the basis of sequence length and average base/amino acid molecular weights. Also includes a list of 1200 of the most commonly encountered organic and inorganic compounds, which may be immediately selected in order to calculate their molecular weights, as well as an easy-to-access list of the chemical elements, which may be plugged into any chemical formula.