Structure and properties of CY5.5-NHS Cyanine dye CY5.5-active ester

Cyanine5.5-NHS (Cy5.5-NHS) is a derivative of Cyanine5.5 that adds an N-hydroxysuccinimide (NHS) group to the structure of Cyanine5.5. This NHS group allows Cy5.5 to conveniently form covalent bonds with biomolecules (e.g., proteins, antibodies, etc.). Below are some descriptions of the structure and properties of Cy5.5-NHS:

1. Structure: The structure of Cy5.5-NHS is essentially the same as that of Cyanine5.5, containing an organic dipolar backbone consisting of two linked azacycles connected by a five-carbon chain. The ends of this backbone are usually connected with electron-attracting groups, such as indole rings. In Cy5.5-NHS, there is an additional NHS group that allows it to form covalent bonds with biomolecules.

2. Nature:

   - Fluorescence Properties: Cy5.5-NHS has a maximum absorption wavelength of approximately 675 nm and a maximum emission wavelength of approximately 694 nm. This fluorescent property in the near infrared region makes Cy5.5-NHS particularly useful in bioimaging, where the autofluorescence background of biological tissues is low in the wavelength region, and light penetration is good.

   - Chemical reactivity: The NHS group in Cy5.5-NHS can react with amino groups (e.g. lysine residues) in biomolecules to form stable amide bonds, thus enabling the labeling of biomolecules.

   - Stability: Cy5.5-NHS has good photostability and chemical stability and can maintain its fluorescent properties under prolonged exposure. However, Cy5.5-NHS is sensitive to oxygen and pH, so it needs to be used and stored in an oxygen-free and neutral pH environment.

   - Solubility: Cy5.5-NHS is soluble in organic solvents such as DMSO, with lower solubility in water or aqueous solvents.