N-(m-PEG4)-N'-(PEG3-Mal)-Cy5

N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 is a Cy5-based fluorescent labeling reagent featuring a maleimide handle for thiol-directed conjugation and PEG spacers that improve aqueous handling and reduce nonspecific interactions. Its far-red emission supports fluorescence microscopy and flow cytometry workflows where reduced background and convenient filter matching are important for tracking labeled biomolecules, surfaces, or nanoparticles.

1. Thiol-Directed Protein Labeling

N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 is frequently used by protein chemistry and chemical biology teams to generate Cy5-labeled antibodies, peptides, and affinity reagents through maleimide coupling to accessible cysteine thiols. The PEG spacers help maintain conjugate solubility and can reduce steric crowding near the dye, which is useful when preparing fluorescent probes for binding studies, imaging reagent development, and fluorescence-based binding assays. Researchers typically incorporate the resulting Cy5 conjugates into microscopy workflows to visualize target-associated signals and into assay development pipelines where far-red readouts help minimize spectral cross-talk with common green-channel fluorophores.

2. Biomolecule Conjugation For Imaging

N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 supports fluorescent labeling of biomolecules and biomolecule-derived constructs used in cellular imaging and molecular tracking experiments. The maleimide functionality enables straightforward attachment to thiol-containing ligands (including thiol-terminated polymers, reduced peptide tags, or engineered cysteine-containing proteins), while the Cy5 dye provides a bright far-red signal for localization studies in multi-color imaging panels. This reagent is commonly selected when investigators need a stable fluorescent conjugate for tracking conjugate distribution, comparing binding/uptake behavior across conditions, or preparing imaging standards for microscopy and imaging instrumentation.

3. Nanoparticle And Surface Functionalization

N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 is also used in materials and nanotechnology workflows to decorate thiol-functionalized nanoparticles, polymer carriers, and PEGylated surfaces with a fluorescent reporter. By coupling the maleimide group to thiol groups on pre-functionalized materials, researchers can build fluorescently traceable platforms for studying transport, adsorption, or assembly behavior in complex media. The far-red Cy5 emission is particularly useful for tracking labeled materials in the presence of autofluorescent samples, and the PEG spacers support compatibility with aqueous formulations used in surface modification and materials characterization experiments.

4. Flow Cytometry Fluorescent Tracing

N-(m-PEG4)-N'-(PEG3-Mal)-Cy5 is employed in flow cytometry development to generate far-red fluorescent labeling reagents for cell-associated or bead-based readouts. Maleimide coupling to thiol groups allows rapid preparation of Cy5-tagged targeting ligands or labeling components that can be used to track binding to cell-surface features, monitor labeling efficiency, or support multiplex staining panels where a Cy5 channel is advantageous. Researchers often choose this reagent when they want a PEG-spaced Cy5 conjugate that performs consistently in aqueous staining buffers and provides a strong signal for instrument-based quantification of fluorescently labeled populations.