Alpha factor mating pheromone is a peptide of 13 amino acids secreted by Saccharomyces cerevisiae α cells.

5-CFDA(5-Carboxyfluorescein diacetate) is membrane-permeant. It can be loaded into cells via incubation and hydrolyzed by intracellular esterases to 5-carboxyfluorescein that is used for labeling human intervertebral disk cells in vitro for fluorescence microscopy.

C-Peptide, dog is a component of proinsulin, released from pancreatic beta cells into blood together with insulin. The C-peptide of proinsulin is important for the biosynthesis of insulin but has for a long time been considered to be biologically inert.