Step-by-step explanation:
The fact that the protein molecule has a negative charge indicates that it has gained one or more electrons, which gives it an overall negative charge. The statement that it has "30 excess electrons" suggests that the protein molecule has taken on 30 more electrons than it would have in a neutral state. The exact charge of the protein molecule will depend on the pH of the solution, since the pH can affect the ionization state of amino acid residues in the protein and hence its overall charge. However, regardless of the pH, the fact that the protein molecule has a net negative charge means that it will be attracted to a positively charged electrode in an electrophoresis gel and will migrate towards it under an electric field.