Answer
At a neutral pH i.e. pH 7, only five of the twenty common amino acids carry a net positive or a net negative charge. Aspartic acid and Glutamic acid are negatively charged (-1), at a neutral pH the carboxlic side chains lose a H+ ion Lysine, Arginine and Histidine are positively charged (+1), at a neutral pH the side chains accept a H+ ion. All other amino acids are generally uncharged (0). It is therefore easy to work out the net charge of any sequence. All sequences contain the one letter abbreviation for each amino acid. Here the sequence is "aggdrleeq" a-alanine (uncharged = 0) g-glycine (uncharged = 0) g-glycine (uncharged = 0) d=aspartic acid (negatively charged = -1) r-arginine (positively charged = +1) I=leucine (uncharged = 0) e-glutamic acid (charged = -1) e-glutamic acid (charged = -1) q=glutamine (uncharged = 0) Add up all the charges -3, +1 gives a total peptide charge of -2.
Work Step by Step
At a neutral pH i.e. pH 7, only five of the twenty common amino acids carry a net positive or a net negative charge. Aspartic acid and Glutamic acid are negatively charged (-1), at a neutral pH the carboxlic side chains lose a H+ ion Lysine, Arginine and Histidine are positively charged (+1), at a neutral pH the side chains accept a H+ ion. All other amino acids are generally uncharged (0). It is therefore easy to work out the net charge of any sequence. All sequences contain the one letter abbreviation for each amino acid. Here the sequence is "aggdrleeq" a-alanine (uncharged = 0) g-glycine (uncharged = 0) g-glycine (uncharged = 0) d=aspartic acid (negatively charged = -1) r-arginine (positively charged = +1) I=leucine (uncharged = 0) e-glutamic acid (charged = -1) e-glutamic acid (charged = -1) q=glutamine (uncharged = 0) Add up all the charges -3, +1 gives a total peptide charge of -2.
