Sulfo-Cyanine5.5 maleimide | CAS 2183440-58-4

Sulfo-Cyanine5.5 maleimide is a water-soluble, maleimide-functionalized cyanine dye designed for thiol-selective fluorescent labeling of biomolecules and surfaces. Its near-infrared emission supports low-background fluorescence imaging workflows, while the maleimide handle enables conjugation to cysteine-containing peptides, proteins, and other thiol-bearing targets under bioconjugation conditions. Researchers commonly use this reagent to generate stable fluorescent conjugates for optical tracking, microscopy, and fluorescence-based assays.

1. Protein Thiol Labeling

Sulfo-Cyanine5.5 maleimide is widely used for fluorescent labeling of antibodies, enzymes, and other thiol-containing proteins to create imaging reagents for biochemical assays and optical readouts. The maleimide group reacts with accessible cysteine thiols, allowing researchers to prepare dye-protein conjugates for fluorescence microscopy and fluorescence-based quantification. Because the dye is sulfonated, conjugation workflows often emphasize improved aqueous handling for labeling protocols that require consistent dispersion and reduced nonspecific hydrophobic interactions.

2. Peptide And Biomolecule Conjugates

Sulfo-Cyanine5.5 maleimide supports construction of fluorescent peptide conjugates and other cysteine-bearing biomolecule probes used in molecular imaging and cellular binding studies. In typical workflows, the reagent is used to tag targeting peptides, receptor ligands, or functional biomolecules with a near-infrared fluorophore for visualization and tracking in optical imaging experiments. This labeling strategy is also used to prepare reference standards and fluorescent controls for assay development where the dye's emission region provides separation from common visible-channel fluorophores.

3. Surface And Nanomaterial Functionalization

Sulfo-Cyanine5.5 maleimide is used to functionalize thiol-reactive surfaces and to label nanoparticles, biomaterial scaffolds, and polymer coatings that present accessible thiol groups. Researchers incorporate the dye into surface-engineered materials to enable fluorescence mapping of coating uniformity, surface coverage, and material localization in microscopy and imaging experiments. The sulfonated cyanine format helps maintain labeling performance in aqueous media, supporting workflows where the final labeled material must remain dispersible for characterization and downstream experimental use.

4. In Vivo Imaging Research Probes

Sulfo-Cyanine5.5 maleimide is frequently selected for building near-infrared fluorescent imaging probes for preclinical optical tracking studies in research settings. Conjugates prepared from thiol-bearing targeting ligands or carrier proteins are used to monitor biodistribution-like signals and probe localization using fluorescence imaging instrumentation. The maleimide-based conjugation enables straightforward preparation of dye-biomolecule constructs that can be used as optical reporters in longitudinal imaging experiments, where emission in the far-red/near-infrared region helps reduce background from autofluorescence.