Single-chain variable fragments (scFv) can be displayed on the surface of the
bacteriophage M13 and still function in selectively binding their antigens. Even
though these antibody fragments are much smaller (25 vs. 150 kDa) than the intact
molecules, they can bind their antigens with exquisite sensitivity and specificity.
Libraries of scFv antibodies can be screened by affinity selection for binding
to any type of target, such as a protein or an organic molecule. The resulting
isolated antibodies can be used in a wide variety of applications (e.g., detectors,
crystallization agents, and modifiers of target activity). In addition, such antibodies
can be used as adapters that bridge inert materials in a defined manner, and thus
may be excellent tools for building nanostructures.