Structure and properties of CY5

Cyanine5 (Cy5) is a commonly used fluorescent dye for a wide range of applications including biomarkers, biosensors and imaging studies.

1. Structure: The structure of Cyanine5 contains a dipolar organic 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. This specialized structure gives Cy5 the ability to absorb and emit light in the visible and near-infrared regions.

2. Nature:

   - Fluorescence Properties: Cy5 has a maximum absorption wavelength of approximately 650 nm and a maximum emission wavelength of approximately 670 nm. This fluorescent property in the near infrared region makes Cy5 particularly useful in biological imaging, where the autofluorescent background of biological tissues is low in this wavelength region and light penetration is good.

   - Chemical reactivity: Cy5 can form covalent bonds with biomolecules (e.g., proteins, antibodies, nucleic acids, etc.) via its NHS ester, maleimide, or other reactive esters.

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

   - Solubility: Cy5 is soluble in organic solvents such as DMSO and less soluble in water or aqueous solvents.