You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Cholinesterase confabs and cousins: Approaching forty years. In the past four decades of cholinesterase (ChE) research, we have seen substantive evolution of the field from one centered around substrate and inhibitor kinetic profiles and compound characterizations to the analysis of ChE structure, first through the gene families and then by X-ray crystallographic determinations of the free enzymes and their complexes and conjugates. Indeed, these endeavors have been facilitated by recombinant DNA technologies, structure determinations and parallel studies in related proteins in the α/β-hydrolase fold family. This approach has not only contributed to a fundamental understanding of structure and function of a large family of hydrolase-like proteins possessing functions other than catalysis, but also has been used to develop new practical strategies for scavenging and antidotal activity in cases of organophosphate insecticide or nerve agent exposure.
{"Chemical": ["organophosphate"]}