Using surface plasmon resonance to directly determine binding affinities of combinatorially selected cyclopeptides and their linear analogs to a streptavidin chip.
In our recent report, several HPQ-containing streptavidin ligands were identified from a structurally constrained combinatorial library, and the relative affinities in IC(50) of these tight-binding ligands were revealed by a captured enzyme-linked immunosorbent assay. In the present work, surface plasmon resonance was employed to directly evaluate the binding affinities between immobilized streptavidin and combinatorially selected ligands. The equilibrium dissociation constants and kinetic on/off rates of a previously identified N-to-side chain and newly synthesized N-to-C cyclopeptides were readily deduced using Scatchard analysis and computational simulation. It was found that both cyclopeptides bound streptavidin far more tightly than its linear counterpart ( approximately 1000-fold), while the reversed (QPH) linear and cyclic peptidyl ligands were hardly recognized by streptavidin. Consequently, not only was the binding specificity of synthetic ligands distinguished qualitatively but also the entropic advantage of conformationally constrained cyclopeptides over their linear forms was demonstrated quantitatively by surface plasmon resonance.
Chang
Yi-Pin
YP
Department of Chemistry and Biochemistry, National Chung Cheng University, Chia-Yi, Taiwan 621, Republic of China.
Chu
Yen-Ho
YH
D000595:Amino Acid Sequence; D020650:Combinatorial Chemistry Techniques; D003198:Computer Simulation; D008024:Ligands; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000378:metabolism*; D040081:Protein Array Analysis; D011485:Protein Binding; D019809:Streptavidin / Q000378:metabolism*; D020349:Surface Plasmon Resonance / Q000379:methods*; D013816:Thermodynamics
D008024:Ligands; D010456:Peptides, Cyclic; D019809:Streptavidin