What is a Metal Ion-Targeted Aptamer Screening Service? It is a contract research service where a specialized laboratory uses an in vitro selection process (most commonly SELEX - Systematic Evolution of Ligands by EXponential Enrichment) to identify single-stranded DNA or RNA oligonucleotides (aptamers) that bind with high affinity and specificity to a specific metal ion (e.g., Pb²⁺, Hg²⁺, UO₂²⁺, As³⁺, Cd²⁺). Unlike aptamers for proteins, metal ion aptamers often rely on the ion's unique coordination chemistry to induce a specific fold or structural switch in the oligonucleotide. Core Service Workflow (The Screening Process) A typical service provider would follow these steps: Design & Library Synthesis: Creation of a vast random-sequence oligonucleotide library (10¹⁴ - 10¹⁵ different sequences). Target Preparation: The target (e.g., Pb²⁺) is often presented in a specific buffer system that controls charge, pH, and the presence of competing ions to drive selection for the desired specificity. Selection Rounds (SELEX Cycle): Binding: Incubate the library with the target metal ion. Partition: Separate metal-bound sequences from unbound ones. This is the most critical and challenging step for small ions. Techniques include: Immobilization: Cheating the ion to a solid support (beads). Capture-SELEX: Using a complementary strand or an auxiliary molecule. Size-based separation: If binding induces a conformational change (e.g., dimerization). Amplification: PCR (for…
