Key Characteristics of a Toggle-SELEX Service: Alternating Rounds: The library is selected against Target A in one round, then against Target B in the next, and so on. The stringency can be adjusted in each path. Strategic Goal: The design is flexible. It can aim for aptamers that bind both A and B (by keeping sequences that bind each during its respective round) OR for aptamers that bind A but not B (by using B as a structured counter-selection). Applications: Ideal for developing diagnostics for variable pathogens (e.g., influenza, SARS-CoV-2 variants), targeting conserved regions in protein families, or creating sensors for a class of compounds (e.g., related antibiotics or toxins). Typical Service Workflow Outline: Design: Defining the two targets (A & B), the desired binding profile (broad or specific), and the toggling protocol. Library & Immobilization: Preparing a naive library, often with one target (e.g., Target A) immobilized. Toggling Selection Cycles: Iterative rounds where: Round A: Select for binders to immobilized Target A. Elute, recover, and amplify bound sequences. Round B: Use the enriched pool against immobilized Target B (either to capture shared binders or to discard cross-reactive ones). The process repeats, toggling between targets, with increasing stringency. Sequencing & Analysis: Identifying enriched sequence families and analyzing their binding patterns to both targets. Characterization: Testing candidate aptamers for affinity (Kd) against both Target A and Target…
