Structural 3D visualization of gp20 protein. Gp20 is a portal protein of the bacteriophage T4 and is part of the mechanism that introduces DNA (deoxyribonucleic acid) into the capsid. This model was visualized with Schrodinger Maestro software and shows electrostatic charges. Red are negative charges, blue are positive charges and gray are neutral charges. T4 is a bacteriophage that infects Escherichia coli bacteria. Phages such as T4 are a possible therapy against multi-drug-resistant bacteria.