Structure and properties of CY3-NHS Cyanine3-active ester

Cyanine3 reactive ester (Cyanine3 NHS ester, also known as CY3-NHS) is a fluorescent dye that has a functional group of an N-hydroxysuccinimide (NHS) ester, which allows it to react with biomolecules containing amino groups.

1. Structure: Cyanine 3-NHS usually contains a tricyclic fluorescent backbone with an alkyl or alkenyl bridge between two nitrogen atoms. The active NHS ester functional group is attached to this backbone, and the NHS ester reacts readily with the amino group to form a stable amide bond.

2. Nature:

   - Fluorescence Properties: Cyanine3-NHS has a maximum absorption wavelength in the red part of visible light (550 nm) and an emission wavelength around 570 nm. This property allows it to be observed under a conventional fluorescence microscope.

   - Chemical reactivity: NHS esters can react with amino groups (side chains of lysine residues, N-terminal amino groups) to form stable amide bonds. This reaction takes place under neutral or slightly alkaline conditions and is rapid.

   - STABILITY: Cyanine 3-NHS is stable when stored in a dry, cold, dark place. However, the NHS ester hydrolyzes rapidly in water or water-containing solvents and therefore needs to be used under anhydrous conditions.

   - Solubility: Cyanine3-NHS is soluble in organic solvents (e.g., dimethylformamide, DMSO) but insoluble in water.

Cyanine3-NHS has many applications in biology and medical research, including biomarkers, cell imaging, flow cytometry, immunofluorescence techniques, FRET studies, and more.