APC belongs to the phycobiliprotein family of highly soluble and fluorescent proteins derived from cyanobacteria and eukaryotic algae. APC is an ultra-sensitive fluorescent tracer with high emission quantum yields, that emits in the near-infrared fluorescence range. It therefore avoids interference from the autofluorescence of cellular components and other biological materials. This product is supplied with 50% ammonium sulfate for longer-term storage. The ammonium sulfate is used to increase the fluorescent protein's quality and avoid protein degradation, however, this must be removed by buffer exchange before use.