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…
Toggle-SELEX is a sophisticated and powerful variant of the traditional SELEX process for aptamer development, specifically designed to generate aptamers that recognize multiple, closely related targets or a specific epitope common across different species/conditions. Let's break down what an Aptamer Screening Service using Toggle-SELEX entails, its applications, and what you should consider when selecting a service provider. What is Toggle-SELEX? The core idea of Toggle-SELEX is to "toggle" or alternate the selection pressure between two (or more) related target molecules during the SELEX rounds. Traditional SELEX: Uses a single target to evolve aptamers with high affinity for that specific target. It often negatively selects against related molecules (counter-selection) to ensure specificity. Toggle-SELEX: Actively uses two positive selection targets in an alternating pattern. For example: Round 1: Select against Target A (e.g., human protein). Round 2: Select against Target B (e.g., mouse ortholog of the same protein). Round 3: Back to Target A, and so on. Counter-selection against unrelated structures is still used to maintain general specificity. This process enriches for nucleic acid sequences that bind to a conserved structural epitope present on both targets, while sequences that bind to unique epitopes on only one target are filtered out. Key Applications of Toggle-SELEX This method is invaluable when you need cross-reactive or broad-spectrum recognition: Cross-Species Reactive Aptamers: Develop aptamers for preclinical research. For example, an…
