Fluorescein-PEG5-acid | CAS 2183440-40-4

Fluorescein-PEG5-acid is a fluorescein-based dye conjugated to a short PEG5 spacer and terminated with a carboxylic acid, enabling convenient coupling to amines and other functional handles while improving aqueous compatibility and reducing nonspecific surface adsorption. Its fluorescein emission is widely used for visible-range fluorescence readouts in labeling, imaging, and assay development workflows where a reactive, hydrophilic dye is required.

1. Protein And Peptide Labeling

Fluorescein-PEG5-acid is routinely used by protein and peptide labeling teams to prepare fluorescent conjugates for fluorescence microscopy, gel-based analysis, and fluorescence readouts in biochemical assays. The PEG5 spacer helps maintain dye accessibility on bulky biomolecules, while the terminal carboxylic acid supports downstream bioconjugation strategies to introduce fluorescein into antibodies, enzymes, affinity reagents, and peptide probes. Researchers often incorporate this dye into labeling workflows where water-soluble fluorescein conjugates are needed to track biomolecule distribution, binding, or processing in solution and on surfaces.

2. Fluorescence Microscopy Tracing

Fluorescein-PEG5-acid is frequently selected for cellular and biomaterials imaging experiments that require a bright, well-characterized fluorescein signal for tracking labeled components. In microscopy workflows, the PEG5 linker supports more uniform staining of target constructs compared with directly attached dye motifs, which can reduce aggregation and improve reproducibility across samples. Typical use cases include labeling of biomolecule carriers, fluorescent tagging of affinity reagents used in imaging studies, and preparation of fluorescent standards for method development and instrument alignment in visible-channel microscopy.

3. Surface and Biomaterial Functionalization

Fluorescein-PEG5-acid is well suited for creating fluorescently labeled surfaces and biomaterial coatings where a hydrophilic dye with a reactive carboxyl handle is advantageous. Materials scientists use the carboxylic acid functionality to incorporate fluorescein into polymer films, hydrogel networks, and functionalized surfaces that are compatible with fluorescence microscopy and optical detection. The PEG5 spacer can help improve dye dispersion within hydrophilic matrices and supports robust visualization of immobilized biomolecule layers, enabling studies of surface-bound interactions, coating uniformity, and spatial mapping of functional components.

4. Fluorescence-Based Bioassay Reagents

Fluorescein-PEG5-acid is commonly used in fluorescence assay development as a labeling dye for constructing reporter conjugates and assay reagents that report on binding events or biomolecule localization in multiwell formats. Assay developers leverage the carboxylic acid for conjugate preparation to generate fluorescent probes for monitoring biomolecular interactions, reagent tracking in wash steps, and assay workflow validation. Because fluorescein is broadly supported by standard fluorescence plate readers and common imaging channels, this dye is often integrated into research assays where consistent visible fluorescence readout is required for routine method development and troubleshooting.