There is a significant need for antibodies that can bind targets with greater affinity. Here we describe a. novel strategy employing chemical semisynthesis to produce symmetroadhesins: antibody-like molecules having nonprotein hinge regions that are more flexible and extendible and are capable of two-handed binding. Native chemical ligation was carried out under mild, non-denaturing conditions to join a ligand binding domain (A beta peptide) to an IgG1 Fe dimer via discrete oxyethylene oligomers of various lengths. Two-handed A beta-Fe fusion proteins were obtained in quantitative yield and shown by surface plasmon resonance to bind an anti-A beta antibody with a K-D at least two orders of magnitude greater than the cognate A beta peptide. MALDI-TOF MS analysis confirmed the protein/nonprotein/protein structure of the two-handed molecules, demonstrating its power to characterize complex protein-nonprotein hybrids by virtue of desorption/ionization mediated by peptide sequences contained therein. We anticipate many applications for symmetroadhesins that combine the target specificity of antibodies with the novel physical, chemical and biological properties of nonprotein hinges.