Cy5-PEG4-acid

Cy5-PEG4-acid is a Cy5-based fluorescent labeling reagent featuring a PEG4 linker terminating in a carboxylic acid, enabling convenient conjugation to amine-containing biomolecules and surfaces while improving handling and reducing nonspecific interactions relative to shorter linkers. Its far-red emission profile is commonly leveraged in fluorescence imaging workflows where spectral separation from visible dyes is advantageous, including multicolor labeling experiments and low-background visualization in complex biological samples.

1. Protein And Peptide Labeling

Cy5-PEG4-acid is frequently used by protein and peptide researchers to generate fluorescent conjugates for fluorescence microscopy and fluorescence-based binding assays. The PEG4 spacer helps maintain labeling flexibility, which can be important when attaching Cy5 to antibodies, enzymes, or affinity reagents that require preserved binding or catalytic behavior. The terminal carboxylic acid supports downstream coupling strategies to introduce the Cy5 label into amine-rich targets, enabling far-red tracking of biomolecule localization, distribution, and interaction in assay formats that benefit from reduced autofluorescence.

2. Antibody Conjugate Imaging

Cy5-PEG4-acid is a practical choice for building far-red antibody conjugates used in immunofluorescence and cellular imaging studies. Researchers commonly incorporate this dye-linker into labeling workflows to visualize antigen expression patterns with a spectral window that is distinct from common green and orange fluorophores. The PEG4 linker supports more uniform presentation of the dye away from the antibody surface, which can be helpful for consistent staining and imaging across different sample types such as cultured cells and fixed specimen preparations used in microscopy.

3. Surface and Biomaterial Functionalization

Cy5-PEG4-acid is also applied in biomaterials and surface engineering projects where fluorescent tagging of materials is needed for imaging, coating verification, or studying biomolecule-material interactions. The carboxylic acid functionality allows integration of Cy5 into surface-modified polymers, hydrogels, and other functional coatings through established coupling approaches to reactive surface chemistries. Far-red Cy5 labeling is particularly useful when monitoring material distribution in heterogeneous environments, such as porous scaffolds or layered coatings, where background fluorescence from the bulk can otherwise obscure signal.

4. Fluorescence Tracing In Assays

Cy5-PEG4-acid is used as a labeling component for fluorescence tracing experiments in bioassay development, including workflows that track labeled reagents, binding partners, or uptake processes using plate readers or fluorescence microscopes. Researchers often select Cy5-PEG4-acid when they want a far-red reporter that can be measured alongside other fluorophores with minimal spectral overlap. In these applications, the PEG4 linker contributes to more reproducible conjugate behavior, supporting consistent readouts across experimental replicates.