Carboxyfluorescein-PEG12-NHS | CAS 2246595-66-2

Carboxyfluorescein-PEG12-NHS is an activated NHS ester form of fluorescein conjugated through a PEG12 spacer, designed for efficient covalent attachment to primary amine groups on proteins, peptides, and other biomolecules. The fluorescein chromophore provides bright visible fluorescence for labeling and imaging workflows, while the PEG spacer helps improve conjugation accessibility and reduces steric constraints during bioconjugation. This reagent is widely used to generate fluorescent conjugates for microscopy, flow cytometry, and fluorescence-based assay development.

1. Protein And Peptide Labeling

Carboxyfluorescein-PEG12-NHS is routinely used by bioconjugation laboratories to fluorescently label antibodies, enzymes, serum proteins, and peptide reagents via NHS-ester coupling to lysine residues or N-terminal amines. The PEG12 linker supports more uniform labeling and can help preserve biomolecular performance by spacing the fluorophore away from the binding or catalytic surface. Labeled proteins prepared from this reagent are commonly used as imaging reagents, fluorescence standards, and traceable components in biochemical workflows where covalent attachment and stable signal are required.

2. Fluorescence Microscopy Staining

Carboxyfluorescein-PEG12-NHS is used to prepare fluorescent labeling reagents for microscopy studies, including tracking biomolecule localization on cell surfaces and visualizing labeled extracellular targets in fixed-sample workflows. In microscopy-oriented assay development, the fluorescein signal enables straightforward detection with standard fluorescein filter sets, while the PEG spacer can improve labeling consistency for conjugates that are subsequently used in imaging protocols. Researchers often incorporate the resulting fluorescein conjugates into staining panels to follow binding patterns, wash behavior, and spatial distribution of labeled biomolecules.

3. Flow Cytometry Conjugate Preparation

Carboxyfluorescein-PEG12-NHS supports fluorescent conjugate generation for flow cytometry workflows where amine-reactive coupling is needed to create stable, covalently labeled detection reagents. Antibody fragments, ligands, and other amine-containing binders labeled with this fluorescein PEG-NHS ester are used to quantify binding to target cells or to track reagent uptake in controlled experimental setups. The PEG12 spacer helps maintain accessibility of the recognition element while providing a bright fluorescein readout compatible with common cytometer configurations that include fluorescein excitation and emission channels.

4. Fluorescence Assay Reagent Development

Carboxyfluorescein-PEG12-NHS is frequently employed to build fluorescent assay reagents by covalently tagging assay components such as capture reagents, reporter proteins, or labeling substrates that contain accessible primary amines. In fluorescence-based bioassay development, fluorescein conjugates generated from this NHS ester are used as signal reporters for binding assays, reagent tracing, and platform qualification experiments where consistent labeling chemistry is important. The PEG12 spacer can be particularly helpful when the labeled reagent must remain functionally accessible in solution-phase or surface-associated assay formats.