Aggregation is a major cause of the misbehavior of proteins. A system for modifying a protein to create a more stable variant is provided. The method involves identifying non-conserved hydrophobic amino acid residues on the surface of a protein, suitable for mutating to more hydrophilic residues (e.g., charged amino acids). Any number of residues on the surface may be changed to create a variant that is more soluble, resistant to aggregation, has a greater ability to re-fold, and/or is more stable under a variety of conditions. The invention also provides GFP, streptavidin, and GST variants with an increased theoretical net charge created by the inventive technology. Kits are also provided for carrying out such modifications on any protein of interest.