Cyanine

Cyanine is the non-systematic name of a synthetic dye family belonging to polymethine group. The word cyanin is from the English word 'cyan', which conventionally means a shade of blue-green (close to 'aqua') and is derived from the Greek κυάνεος/κυανοῦς kyaneos/kyanous which means a somewhat different color: 'dark blue'. Cyanine is the non-systematic name of a synthetic dye family belonging to polymethine group. The word cyanin is from the English word 'cyan', which conventionally means a shade of blue-green (close to 'aqua') and is derived from the Greek κυάνεος/κυανοῦς kyaneos/kyanous which means a somewhat different color: 'dark blue'. Cyanines were and are still used in industry, and more recently in biotechnology (labeling, analysis). Cyanines have many uses as fluorescent dyes, particularly in biomedical imaging. Depending on the structure, they cover the electromagnetic spectrum from near IR to UV. There are a large number reported in the literature. There are three types of cyanines: where two quaternary nitrogens are joined by a polymethine chain. Both nitrogens may each be independently part of a heteroaromatic moiety, such as pyrrole, imidazole, thiazole, pyridine, quinoline, indole, benzothiazole, etc. Cyanines were first synthesized over a century ago.They were originally used, and still are, to increase the sensitivity range of photographic emulsions, i.e., to increase the range of wavelengths which will form an image on the film, making the film panchromatic. Cyanines are also used in CD-R and DVD-R media. The ones used are mostly green or light blue in color, and are chemically unstable. This makes unstabilized cyanine discs unsuitable for archival CD and DVD use, as they can fade and become unreadable in a few years, however, recent cyanine discs contain stabilizers that slow down the deterioration significantly. These discs are often rated with an archival life of 75 years or more. The other dyes used in CD-Rs are phthalocyanine and azo. Cyanines dyes are usually synthesized from 2, 3, 5 or 7-methine structures with reactive groups on either one or both of the nitrogen ends so that they can be chemically linked to either nucleic acids or protein molecules. Labeling is done for visualization and quantification purposes. Biological applications include comparative genomic hybridization and gene chips, which are used in transcriptomics, and various studies in proteomics such as RNA localization, molecular interaction studies by fluorescence energy transfer (FRET) and fluorescent immunoassays. Alan S. Waggoner et al. of Carnegie-Mellon University filed a key patent application in this field in 1986, which later resulted in the grant of a number of patents relating to the use of Cyanine dyes including US6225050 (B1) in 2001 and US6956032 (B1) in 2005. This intellectual property was licensed to GE Healthcare.