A straightforward and reliable evaluation of Ag(I) binding affinity mediated by a peptide ligand for constructing an efficient sensing platform.

The reliable determination of the Ag(I) affinity for biomolecules is an essential issue in the fields of structural analysis and sensor design. However, the urgent problem confronting researchers is lack of a direct and accurate Ag(I) affinity evaluation as a reference standard for ligand analysis. We communicated here a straightforward and high-efficiency method of measuring Ag(I) affinity exactly on the basis of the unique calculation algorithm and the design of a special peptide RFPRDD (P) as Ag(I) binding motif. According to UV-vis competition between the corresponding complexes (AgP) and biomolecules (peptides, amino acids and ssDNA), the decrease of the signature at 300 nm characteristic of AgP was obtained for quantitative analysis. The primary advantages of this strategy were the widespread application, high accuracy and reference significance, which were corroborated by theoretical calculations. To identify its potential in biosensing, two kinds of testing models for Ag(I) were proposed by AgBP2-decorated and Ag4-decorated gold nanoparticles, the detection limits of which were 2 nM and 75 nM respectively. By contrast of the sensing property of the functional peptides (AgBP2, Ag4), we afforded evidence that this conception could be regarded as an evaluation criterion for the selection and performance optimization of sensitive elements, thereby holding a dominant position in the biosensors.