Detailed Instructions: In this task, you are given a paragraph (from a research paper) and your task is to classify each sentence of the paragraph (assume n sentence) into the following categories: Background, Purpose, Method, Finding/Contribution, or Other. Return the output in this format: 1 - category of sentence 1, 2 - category of sentence 2, ..., n - category of sentence n; where each number indicates the order of the sentence. The categories can be identified using the following questions: 
 Background: - Why is this problem important? - What relevant works have been done before? - What did the previous works miss? - What are the high-level research questions? - How might this help other researchers?
 Purpose: - What specific things do the researchers want to do? - What specific knowledge do the researchers want to know? - What specific hypothesis do the researchers want to test?
 Method: - How did the researchers do it or find it out? - What are the procedures and steps of this research?
 Finding/Contribution: - What did the researchers find out? Did the proposed methods work? - Did things behave as the researchers expected?
Other: put every text fragment that does not fit into any of the categories above here. Put a sentence here if its not in English, is not part of the article, contains numbers and dates, is a caption of a figure or a table, is a formatting error, or you are not sure about it.
Q: Cooperative interactions play a central role in the regulation of protein functions. Here we show that in multi-site systems like ion channels the application of the Hill formalism could require a combination of different experiments, even involving site-directed mutagenesis, to identify the different sources of cooperativity and to discriminate between genuine and apparent cooperativity. We discuss the implications for the channel function in the bacterial porins PorA (N. meningitidis) and OmpF (E. coli ) and the viroporin SARS-CoV E.
A:
1 - background, 2 - finding, 3 - finding, 4 - finding