Coumarin 343 X NHS ester | CAS 946123-12-2

Coumarin 343 X NHS ester is a reactive coumarin-based fluorescent dye designed for NHS-ester bioconjugation workflows. Its activated N-hydroxysuccinimide ester enables efficient labeling of primary amines on proteins, peptides, and other amine-containing biomolecules, producing stable amide-linked fluorescent conjugates for optical readouts. The coumarin emission is commonly leveraged in fluorescence microscopy and fluorescence-based assay development where UV/near-UV excitation and bright, compact dye performance are advantageous.

1. Protein And Antibody Labeling

Coumarin 343 X NHS ester is used to generate fluorescent protein conjugates for imaging and assay development, especially when researchers need an amine-reactive dye for consistent site-agnostic labeling. Laboratories in chemical biology and fluorescence reagent development routinely label antibodies, enzymes, and carrier proteins to track binding, localization, and reagent distribution in solution or on surfaces. The NHS-ester handle supports straightforward conjugate preparation for downstream use in fluorescence microscopy, plate-based fluorescence assays, and labeling controls where a coumarin fluorophore provides a distinct spectral signature.

2. Fluorescence Microscopy Tracing

Coumarin 343 X NHS ester supports cellular and biomolecular fluorescence microscopy applications where amine-containing targets are labeled prior to imaging. Researchers use the resulting fluorescent conjugates to visualize protein trafficking, track labeled biomolecules in fixed samples, and map reagent localization in microscopy experiments that rely on coumarin emission under near-UV excitation. This labeling format is also frequently adopted for constructing fluorescent standards and reference conjugates used to optimize imaging settings, exposure times, and dye-to-target labeling stoichiometry in microscopy workflows.

3. Flow Cytometry Dye Conjugates

Coumarin 343 X NHS ester is employed to prepare fluorescent antibody or protein conjugates for flow cytometry panels that require coumarin-compatible excitation and emission. Immunology and cell biology laboratories often use NHS-ester labeling to generate reagent-grade fluorescent conjugates for staining cell-associated proteins, enabling quantitative population readouts based on fluorescence intensity. In multiplexed studies, the dye's coumarin spectral window helps researchers select channels that minimize overlap with other fluorophores while maintaining robust signal from amine-labeled targets.

4. Fluorescent Bioassay Reagents

Coumarin 343 X NHS ester is widely used in fluorescence assay development to create labeled reagents for binding assays, reporter conjugates, and fluorescence readouts in microplate formats. Assay developers label amine-containing components such as proteins, affinity reagents, or assay substrates to convert biochemical interactions into measurable fluorescence signals. This approach is particularly useful when a stable amide-linked fluorescent tag is required to track reagent performance across incubation and wash steps in fluorescence-based screening and method development workflows.