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:

Exploring key orientations at protein-protein interfaces with small molecule probes. Small molecule probes that selectively perturb protein-protein interactions (PPIs) are pivotal to biomedical science, but their discovery is challenging. We hypothesized that conformational resemblance of semirigid scaffolds expressing amino acid side-chains to PPI-interface regions could guide this process. Consequently, a data mining algorithm was developed to sample huge numbers of PPIs to find ones that match preferred conformers of a selected semirigid scaffold. Conformations of one such chemotype (1aaa; all methyl side-chains) matched several biomedically significant PPIs, including the dimerization interface of HIV-1 protease. On the basis of these observations, four molecules 1 with side-chains corresponding to the matching HIV-1 dimerization interface regions were prepared; all four inhibited HIV-1 protease via perturbation of dimerization. These data indicate this approach may inspire design of small molecule interface probes to perturb PPIs.
{"Chemical": ["amino acid", "methyl"]}