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: ["Protein", "Chemical"].

Please return the output as a JSON object of the format: {"Chemical" : ["Dexamethasone", ...], "Protein" : ["BRCA-1", ...]}. 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:

From in situ to in vivo: an in situ click-chemistry-derived carbonic anhydrase II imaging agent for positron emission tomography.
CA II makes a good PET: Discovering positron emission tomography (PET) probes with high target affinities is challenging. PET probe discovery using in situ click chemistry uses (19) F-bearing fragments as (18) F surrogates. This ensures that the lead hits and PET probes have equivalent chemical or biological characteristics, making PET probe discovery predictable and reliable.
{"Chemical": ["(19) F", "(18) F"], "Protein": []}