Our current focus is the development of improved recognition elements for biothreat detection. We work on the development of single domain antibodies (sdAb) derived from llamas as well as conventional antibody fragments (scFv), and a variety of fusion constructs with an eye towards developing improved recognition and signal transduction elements. The sdAb are derived from the unique heavy-chain antibodies found in camelids, and consist of only a variable heavy domain (Figure 1). Although half the size of an scFv, the sdAb bind target with high affinity and specificity; the majority of sdAb refold and are able to bind antigen after heat denaturation (Figure 2). In contrast, scFv and conventional antibodies aggregate irreversibly after identical heat treatment. We continue to develop sdAb towards a wide range of targets and to work towards a better understanding of their unique properties. In addition we aim to develop methods to engineer scFv to have higher affinities and thermal stabilities. Starting with a given scFv, our goal is to improve its affinity constant by an order of magnitude, and to raise its melting temperature to over 70 degrees C. Ideally we will develop methods that can be applied to improve scFv specific for any target.