Cy5 dye (Sulfo-Cyanine5) is a widely used far-red fluorescent dye for protein and peptide labeling. It is water-soluble, bright, and optimized for 633/647 nm laser excitation. Cy5 conjugates are pH-insensitive (pH 4–10) and benefit from low biological autofluorescence in the far-red region.
Chemistry
- NHS ester (succinimidyl ester) reacts with primary amines (e.g., lysine residues, N-termini)
- Forms stable amide bonds
- Optimal labeling at pH 7.5–9.0
Key Properties
- Ex/Em: ~650/670 nm
- Water-soluble (sulfo form)
- Stable fluorescence across wide pH range
Applications
Antibody/protein labeling, flow cytometry, fluorescence microscopy, multiplex assays.
Notes
- Avoid high dye-to-protein ratios → self-quenching
- Best for moderate–high abundance targets
- For low-abundance targets, consider AF647-type or IR650-type dyes (less self-quenching at high labeling density)
Storage
−20 °C, desiccated, protect from light; minimize moisture exposure.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.
