Promicin is a fictional neurotransmitter in the USA Network science fiction television series The 4400.
It gives people an extra-normal/superhuman ability. Promicin's behavior and effect are unpredictable, potentially giving any ability.
It interacts with a person's natural brainwide neurotransmitters, neuroelectrical pulses and the neuronal wiring in their cerebellum to cause the brain to create a special electromagnetic field that exist as a semi-sentient energy-based lifeform. The lifeform takes form as an inconspicuous energy pattern linked to the natural electromagnetic field of a person's body. Because the EM field lifeform permeates a person's entire body, it innately possesses an intrinsic understanding of all aspects of that person's physiology (including DNA) to a degree that is beyond human comprehension.
The semi-sentience of the EM field is tied into a person's own consciousness and as a result, its actions are based on the person's subconscious will. Because of this connection, the EM field takes signals from a promicin-positive's psyche, as well as their individual genetic structure, stress hormones, and immune system messengers to alter the person's physiology in a way that imbues them with a superhuman ability that might be useful to that particular promicin-positive in their daily life. As a result, every person develops a relatively unique superhuman ability after taking promicin and that ability is actually connected to their personality along with their inherent physiology and environment (both natural and social).