Zinc ion-binding activity of an anti-ZnO VHH antibody, 4F2

The interaction between biomolecules and inorganic materials has gained much interest for the development of sensors and highly controlled materials in scale and composition. For this purpose, 4F2, a VHH antibody with high affinity and specificity toward zinc oxide (ZnO) surfaces has been constructed. Here, we report that 4F2 also has an affinity toward zinc ion (Zn²⁺). The stability of 4F2 and its Zn²⁺ complexes was determined using differential scanning calorimetry. We then determined the binding affinity between 4F2 and Zn²⁺ by using isothermal calorimetry. To further elucidate the molecular binding mechanism of 4F2 toward Zn²⁺, we applied the 1H15N heteronuclear single quantum coherence NMR technique. We found that 4F2 recognized Zn²⁺ near the complementarity determining region 3 (CDR3). Our results provide the basis for the recognition mechanism of ZnO by 4F2.