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.

Human coronavirus HKU1 (HCoV-HKU1) belongs to coronavirus group II and encodes 16 nonstructural proteins (nsps) which mediate genome replication and transcription. Among these nsps, nsp9 has been shown to possess singlestranded DNA/RNA-binding properties. The gene that encodes HCoV-HKU1 nsp9 was cloned and expressed in Escherichia coli and the protein was subjected to crystallization trials. The crystals diffracted to 2.7 Å resolution and belonged to space group P2 1 2 1 2, with unit-cell parameters a = 83.5, b = 88.4, c = 31.2 Å , = = = 90 and two molecules per asymmetric unit.
1 - background, 2 - background, 3 - method, 4 - finding, 5 - finding, 6 - finding, 7 - finding

In an effort to rapidly discover lead compounds targeting M pro , two compounds (11a and 11b) were designed and synthesized, both of which exhibited excellent inhibitory activity with an IC 50 value of 0.05 μ M and 0.04 μ M respectively. Significantly, both compounds exhibited potent anti-SARS-CoV-2 infection activity in a cell-based assay with an EC 50 value of 0.42 μ M and 0.33 μ M, respectively. The X-ray crystal structures of SARS-CoV-2 M pro in complex with 11a and 11b were determined at 1.5 Å resolution, respectively. The crystal structures showed that 11a and 11b are covalent inhibitors, the aldehyde groups of which are bound covalently to Cys145 of M pro . Both compounds showed good PK properties in vivo, and 11a also exhibited low toxicity which is promising drug leads with clinical potential that merits further studies.
1 - purpose, 2 - method, 3 - finding, 4 - finding, 5 - finding, 6 - finding, 7 - finding, 8 - finding, 9 - finding

Repurposing antimalarials as dengue antivirals Chloroquine Primaquine Stable replicon cell lines for dengue and West Nile viruses Inhibition of dengue virus replication and infectivity Amodiaquine therapeutic index a b s t r a c t Dengue virus serotypes 1-4 (DENV1-4) are transmitted by mosquitoes which cause most frequent arboviral infections in the world resulting in $390 million cases with $25,000 deaths annually. There is no vaccine or antiviral drug currently available for human use. Compounds containing quinoline scaffold were shown to inhibit flavivirus NS2B-NS3 protease (NS2B-NS3pro) with good potencies. In this study, we screened quinoline derivatives, which are known antimalarial drugs for inhibition of DENV2 and West Nile virus (WNV) replication using the corresponding replicon expressing cell-based assays. Amodiaquine (AQ), one of the 4-aminoquinoline drugs, inhibited DENV2 infectivity measured by plaque assays, with EC 50 and EC 90 values of 1.08 ± 0.09 lM and 2.69 ± 0.47 lM, respectively, and DENV2 RNA replication measured by Renilla luciferase reporter assay, with EC 50 value of 7.41 ± 1.09 lM in the replicon expressing cells. Cytotoxic concentration (CC 50 ) in BHK-21 cells was 52.09 ± 4.25 lM. The replication inhibition was confirmed by plaque assay of the extracellular virions as well as by qRT-PCR of the intracellular and extracellular viral RNA levels. AQ was stable for at least 96 h and had minor inhibitory effect on entry, translation, and post-replication stages in the viral life cycle. DENV protease, 5 0 -methyltransferase, and RNA-dependent RNA polymerase do not seem to be targets of AQ. Both p-hydroxyanilino and diethylaminomethyl moieties are important for AQ to inhibit DENV2 replication and infectivity. Our results support AQ as a promising candidate for anti-flaviviral therapy.

1 - background, 2 - background, 3 - background, 4 - purpose, 5 - method, 6 - finding, 7 - finding, 8 - finding, 9 - finding, 10 - finding, 11 - finding, 12 - finding, 13 - finding, 14 - finding, 15 - finding, 16 - finding, 17 - finding, 18 - finding

