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:

FRET-capture: a sensitive method for the detection of dynamic protein interactions. Caught in the act: The FRET-Capture approach exploits a bound solvatochromic fluorophore, 4-N,N-dimethylamino-1,8-naphthalimide, as a FRET donor in both inter- and intramolecular energy transfer. A unique feature of this method is the additional level of signal selectivity as the FRET signal is only turned on when the donor is specifically bound to the protein of interest, eliminating high background and false positive signals.
{"Chemical": ["4-N,N-dimethylamino-1,8-naphthalimide"]}