Cyanine5 carboxylic acid | CAS 1032678-07-1

Cyanine5 carboxylic acid is a red-emitting cyanine fluorophore designed for fluorescent labeling workflows where carboxylic acid functionality enables downstream conjugation to biomolecules, polymers, and imaging reagents. Its strong absorption in the far-red region and bright fluorescence make it a widely used component for building fluorescence imaging and labeling tools that are compatible with common laser and filter sets used for Cy5 detection.

1. Protein And Antibody Labeling

Cyanine5 carboxylic acid is frequently used to prepare fluorescently labeled proteins and antibodies for fluorescence microscopy, western blot-style readouts, and fluorescence-based binding assays. Researchers and assay developers typically convert the carboxylic acid into activated derivatives or use established coupling strategies to attach the dye to lysine-rich proteins, affinity reagents, or antibody formulations used in binding and localization studies. The far-red emission supports multiplexing with green and orange channels, while the dye's brightness helps generate robust signal in imaging and plate-based fluorescence measurements.

2. Fluorescence Microscopy Tracing

Cyanine5 carboxylic acid is commonly incorporated into fluorescent conjugates used for cellular and biomaterial tracing experiments where far-red contrast improves visualization against cellular autofluorescence. Imaging teams use Cy5-labeled probes to track biomolecule distribution, monitor uptake or association with labeled targets, and visualize fluorescent tags on engineered materials such as labeled polymers, nanoparticles, and surface-modified constructs. In microscopy workflows, the dye's excitation/emission profile aligns well with standard confocal and widefield filter configurations for Cy5, enabling straightforward integration into multicolor imaging panels.

3. Oligonucleotide And Nucleic Acid Labeling

Cyanine5 carboxylic acid is also used as a fluorescent label for nucleic acid-based research tools, including labeled primers, probes, and hybridization reagents where far-red readout is advantageous for background reduction. Molecular biology laboratories often attach Cy5 to oligonucleotides to generate fluorescent reporters for hybridization and nucleic acid analysis workflows, including imaging-based detection of labeled strands and fluorescence readouts in microplate formats. The carboxylic acid handle supports common conjugation routes used to incorporate Cy5 into oligonucleotide labeling schemes while maintaining compatibility with fluorescence instrumentation designed for Cy5 detection.

4. FRET Pair Construction

Cyanine5 carboxylic acid is frequently selected as an acceptor fluorophore in FRET-based assay development where far-red emission provides convenient spectral separation from common donor dyes. Bioconjugation and fluorescence assay teams use Cy5-containing conjugates to build donor-acceptor systems for monitoring proximity-dependent events in labeled biomolecules, binding interactions, or engineered molecular constructs. By choosing Cy5 as the acceptor, researchers can design FRET readouts that leverage spectral overlap and instrument filter availability for reliable fluorescence-based reporting in solution or imaging formats.