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:

Matrix Metalloproteinase Inhibitors Based on the 3-Mercaptopyrrolidine Core.
New series of pyrrolidine mercaptosulfide, 2-mercaptocyclopentane arylsulfonamide, and 3-mercapto-4-arylsulfonamido pyrrolidine matrix metalloproteinase inhibitors (MMPIs) were designed, synthesized, and evaluated. Exhibiting unique properties over other MMPIs (e.g., hydroxamates), these newly reported compounds are capable of modulating activities of several MMPs in the low nanomolar range, including MMP-2 (~2 to 50 nM), MMP-13 (~2 to 50 nM), and MMP-14 (~4 to 60 nM). Additionally these compounds are selective to intermediate- and deep-pocket MMPs but not shallow-pocketed MMPs (e.g., MMP-1, ~850 to >50,000 nM; MMP-7, ~4,000 to >25,000 nM). Our previous work with the mercaptosulfide functionality attached to both cyclopentane and pyrrolidine frameworks demonstrated that the cis-(3S,4R)- stereochemistry was optimal for all of the MMPs tested. However, in our newest compounds an interesting shift of preference to the trans- form of the mercaptosulfonamides was observed with increased oxidative stability and biological compatibility. We also report several kinetic and biological characteristics showing that these compounds may be used to probe the mechanistic activities of MMPs in disease.
{"Chemical": ["hydroxamates", "3-Mercaptopyrrolidine", "mercaptosulfonamides", "pyrrolidine mercaptosulfide", "pyrrolidine", "2-mercaptocyclopentane arylsulfonamide", "cyclopentane", "3-mercapto-4-arylsulfonamido pyrrolidine", "mercaptosulfide"], "Protein": ["MMP-13", "MMP-2", "MMP-1", "MMP-7", "MMP-14", "Matrix Metalloproteinase", "MMPs", "matrix metalloproteinase"]}