A radio-based navigation system uses a small multi-mode direction-finding antenna and a direction-finding receiver to determine platform position, velocity, attitude and time while simultaneously providing protection against narrowband and broadband sources of interference. The electrical connector system further includes a heat sink disposed forward of the first electrical connector, the heat sink defining an engagement surface configured to contact the complementary electrical connector when the first electrical connector is mated with the complementary electrical connector. Polypeptides that comprise such motif sequences and have brain localizing activity were discovered as follows: DNAs encoding polypeptides comprising random amino acid sequences were synthesized, and incorporated into a phage library.