What is SELEX? SELEX (Systematic Evolution of Ligands by EXponential enrichment) is an in vitro combinatorial chemistry technique used to isolate high-affinity, high-specificity nucleic acid ligands (aptamers) from a vast random-sequence library against a target molecule. Think of it as "molecular evolution in a test tube." Starting with a pool of ~10¹³-10¹⁵ random sequences, SELEX uses iterative cycles of selection and amplification to "evolve" the few molecules that bind best to the target, much like natural selection evolves organisms. Core Principle The principle is based on three repeating steps: Incubation: A vast library of random oligonucleotides is exposed to the target. Partitioning: The rare molecules that bind to the target are separated from the non-binders. Amplification: The bound sequences are amplified (usually by PCR for DNA or RT-PCR for RNA) to create an enriched pool for the next selection round. After 8-20 rounds, the pool becomes dominated by sequences with high binding affinity and specificity for the target. The Standard SELEX Process (Step-by-Step) 1. Library Synthesis: A synthetic library contains 10¹³ to 10¹⁵ different single-stranded DNA or RNA molecules. Each molecule has a central random region (20-80 nucleotides) flanked by constant primer regions for amplification. 2. Incubation & Binding: The library is incubated with the target molecule (e.g., a protein,…
Nucleic Acid Aptamer Libraries Screening: an Efficient Method for Discovering Specific Binding Molecules Aptamers are oligonucleotide sequences (DNA or RNA) consisting of 20-110 nucleotides. Aptamers have high molecular recognition capabilities for different types of targets such as nucleic acids, proteins, cells, and some small molecules, can distinguish subtle differences, and have high affinity and specificity, and are easy to chemically modify. Aptamers are usually oligonucleotide fragments obtained from nucleic acid molecule libraries using in vitro screening technology, namely systematic evolution of ligands by exponential enrichment (SELEX). The structure and function of aptamers are similar to antibodies, but they are smaller in size, have shorter production time, lower cost, and are easier to synthesize. Based on the characteristics of aptamers that can specifically bind to a variety of target molecules, they are widely used in food safety, environmental monitoring, biomedical research and other fields. Aptamers can be used in drug development to design drugs that target specific molecules; many aptamers are used to make biosensors that can diagnose some specific infectious diseases; aptamers can be used as carriers to deliver genes to specific cells or tissues, and have certain application prospects in gene therapy. Since nucleic acid aptamers can be prepared…
Aptamer Screening for Small Molecule Service Process
Categorization & Core Principle All these techniques share the common goal of SELEX (Systematic Evolution of Ligands by EXponential enrichment): isolating high-affinity aptamers from a vast random-sequence library (10^14 - 10^15 sequences) through iterative cycles of Binding → Separation → Amplification → Purification. Your listed techniques primarily differ in the separation method used to partition target-binding sequences from non-binders. Detailed Analysis & Context A. Classical SELEX (Solution-based) What it is: The foundational, versatile protocol. The target is often immobilized to facilitate separation. Separation Method: Filtration, affinity columns, or magnetic beads (if target is tagged/bound to a bead). Note: "SELEX technology" is the umbrella term. Techniques B, C, D, and E are all variants of SELEX that use different separation principles. B. Solid-Phase SELEX (A specific implementation of classical SELEX) Clarification: This is the most common practical implementation for small molecules. The "solid phase carrier" is typically streptavidin-coated beads if the target is biotinylated, or an activated resin if the target is chemically immobilized. Key Advantage: Excellent for counter-selection (to remove sequences that bind to the solid support or similar non-target molecules). C. Centrifugal Precipitation / Particle-Based SELEX Best For: As you noted, it's ideal for cells, bacteria, or large vesicles. For true small molecules, this method is less common unless the small molecule is…
Core Challenge with Small Molecules Small molecules (e.g., drugs, toxins, metabolites, <1000 Da) lack the large, multi-epitope surfaces of proteins. This makes traditional selection methods difficult because: Immobilization: Hard to attach to a solid phase without masking the target area. Limited Binding Interfaces: Offer fewer points for oligonucleotide interaction. Low Signal-to-Noise: Distinguishing specific binders from non-specific binders is tougher. Key Aptamer Screening Techniques Used for Small Molecules KMD Bioscience likely employs a combination of these advanced SELEX (Systematic Evolution of Ligands by EXponential Enrichment) variants: 1. Capture-SELEX (The most common for small molecules) Principle: Instead of immobilizing the small molecule, a DNA library with a fixed primer sequence is immobilized on beads. The small molecule is free in solution. Process: The small molecule is introduced. Sequences that bind to it undergo a conformational change, freeing them from the bead into the solution. These eluted sequences are then amplified. Advantage: The target remains in its native, unmodified state, preserving its structure and function. Ideal for targets that are difficult to tag or immobilize. 2. Graphene Oxide-SELEX (GO-SELEX) Principle: Utilizes graphene oxide's ability to adsorb single-stranded DNA (ssDNA) non-specifically via π-π stacking. Process: The ssDNA library is incubated with GO. Unbound sequences are discarded. The small molecule target is then added. Aptamers…
Aptamer Selection Small molecule aptamer screening techniques generally include the following steps: A. Initial library design: Build a DNA, RNA or peptide library containing a large number of random sequences that have the potential to bind to small target molecules. B. Screening process: The main steps include target binding to the library, isolation and purification of the binding target molecule aptamer PCR amplification, iterative screening and so on. After each round of screening, the screening results can be verified and analyzed through technologies such as sequencing. C. Optimization and validation: The selected aptamers were optimized to improve their affinity, specificity and stability. Subsequently, a series of experiments were carried out to verify its binding ability and application effect. KMD Bioscience Aptamer Screening Service: A Comprehensive Workflow Your description accurately captures the three universal pillars of in vitro selection (SELEX). KMD Bioscience would operationalize these into a robust, client-tailored service. A. Initial Library Design & Preparation Library Diversity: Construction of high-complexity synthetic libraries (typically 10^14 - 10^15 unique sequences) containing a central random region (e.g., 30-60 nucleotides) flanked by constant primer regions. Format Flexibility: Offering DNA, RNA, or modified nucleotide (e.g., 2'-F, 2'-O-Me) libraries to balance stability, cost, and affinity requirements. Target Immobilization: A critical initial step where the small molecule target is…
KMD Bioscience Aptamer Screening Service: Aptamer Types Aptamers are oligonucleotide or peptide sequences obtained through in vitro selection techniques (such as SELEX) that exhibit high specificity and affinity for target molecules. Based on molecular composition, aptamers are primarily categorized into two main types: Nucleic Acid Aptamers and Peptide Aptamers. Both types demonstrate strong target recognition and binding capabilities. Main Types and Characteristics Type Composition Structure and Properties DNA Aptamers Composed of short single-stranded DNA molecules. Can fold into specific three-dimensional structures to recognize and bind targets. Generally more stable than RNA aptamers, and easier to synthesize and modify. RNA Aptamers Composed of short single-stranded RNA molecules. Can also fold into complex three-dimensional structures for high-specificity target binding. Often exhibit greater structural diversity, but natural RNA is susceptible to degradation and often requires chemical modifications for enhanced stability. Peptide Aptamers Consist of short peptide sequences made of amino acids. Typically presented on a stable protein scaffold (e.g., thioredoxin). This design enhances binding affinity and stability towards the target while maintaining peptide flexibility and specificity. Service Value KMD Bioscience's aptamer screening service covers all the above types. Depending on your target characteristics and research objectives (e.g., diagnostics, therapeutics, assay development), we provide end-to-end solutions—from library design and in…
Small molecule aptamers refer to DNA or RNA single strand oligonucleotide sequences with high affinity and high specificity to specific small molecule targets that are screened from random sequence libraries by SELEX technology, and can also be peptides. After years of development, KMD Bioscience has great technical advantages in aptamer selection. With the continuous development and improvement of aptamer technology, the application prospect of small molecule aptamer in the field of biomedicine and medicine research and development will be broader. Small molecule aptamers have important application value in medicine research and development. By obtaining highly specific aptamers for specific small molecules, it can provide important basis for medicine design and optimization, and accelerate the development process of new medicines. In the targeted therapy of diseases such as cancer, aptamers can bind specifically to specific antigens or receptors on the surface of tumor cells, thus achieving precise treatment. KMD Bioscience can provide customized peptide aptamer screening services according to the different experimental and application needs of customers. Aptamer Type According to the type of molecule, aptamers can be divided into two main categories: nucleic acid aptamers and peptide aptamers. Nucleic acid aptamers can be divided into DNA aptamers and RNA aptamers. Both nucleic acid aptamers and peptide aptamers…
Kmdbioscience Aptamer Screening Service We offer comprehensive in vitro aptamer screening services, enabling rapid and accurate identification of aptamers with high affinity and specificity to help clients reduce experimental costs. Our one-stop aptamer screening platform utilizes the natural evolution of ligand systems through the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) method in a flexible and efficient manner. By partnering with us, you will achieve optimal results tailored to your research and development needs.
Aptamer Screening Service: Key Features Broad Target Compatibility: Our screening services are effective for both purified proteins and small chemical molecules. Target Sourcing Flexibility: We can either provide the target or procure it commercially, eliminating the need for clients to supply physical samples. High-Precision Affinity Measurement: The binding affinity (Kd) of selected aptamers is accurately determined using Capillary Electrophoresis (CE). Multiple Candidate Delivery: Depending on screening outcomes, we typically provide several aptamer sequences for further evaluation. Transparent Process: A detailed selection protocol is included, offering full insight into how the aptamers are developed. Efficient Timeline: The standard project duration is approximately three months. Note: Our current screening success rate stands at approximately 80%. Please be aware that developing aptamers for small-sized proteins or small chemical molecules remains particularly challenging. We are continuously refining our methods to enhance screening performance and success rates.