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:

QM/MM simulations of vibrational spectra of bacteriorhodopsin and channelrhodopsin-2.
Channelrhodopsin-2 is a light-gated ion channel, which has been studied intensively over the last decade. Vibrational spectroscopic experiments started to shed light on the structural changes, that occur during the photocycle, especially in the hydrogen-bonded network surrounding the protonated D156 and C128 - the DC gate. However, the interpretation of these experiments was only based on homology models. Since then, an X-ray structure and better computational models became available. In this article, we show that in combination with a recent reparametrization, the approximate DFT method, DFTB, is able to describe the effects of hydrogen bonding on the C[double bond, length as m-dash]O stretch vibration in carboxylic acids reliably and agrees well with full DFT results. We apply DFTB in a QM/MM framework to perform vibrational analysis of buried aspartic acids in bacteriorhodopsin and channelrhodopsin-2. Using this approach, we can simulate the FTIR spectral difference between D115 in the dark-adapted and K states of bacteriorhodopsin. The FTIR experiments on the DC gate in channelrhodopsin-2 are well described using an indirect model, where D156 and C128 are bridged via a water molecule.
{"Chemical": ["O", "carboxylic acids", "hydrogen", "C", "aspartic acids"], "Protein": ["bacteriorhodopsin", "light-gated ion channel", "channelrhodopsin-2", "Channelrhodopsin-2"]}