TASK DEFINITION: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
PROBLEM: Chemical denaturant sensitivity of the dimeric main protease from severe acute respiratory syndrome (SARS) coronavirus to guanidinium chloride was examined in terms of fluorescence spectroscopy, circular dichroism, analytical ultracentrifuge, and enzyme activity change. The dimeric enzyme dissociated at guanidinium chloride concentration of ,0.4 M, at which the enzymatic activity loss showed close correlation with the subunit dissociation. Further increase in guanidinium chloride induced a reversible biphasic unfolding of the enzyme. The unfolding of the C-terminal domain-truncated enzyme, on the other hand, followed a monophasic unfolding curve. Different mutants of the full-length protease (W31 and W207/W218), with tryptophanyl residue(s) mutated to phenylalanine at the C-terminal or N-terminal domain, respectively, were constructed. Unfolding curves of these mutants were monophasic but corresponded to the first and second phases of the protease, respectively. The unfolding intermediate of the protease thus represented a folded C-terminal domain but an unfolded N-terminal domain, which is enzymatically inactive due to loss of regulatory properties. The various enzyme forms were characterized in terms of hydrophobicity and size-and-shape distributions. We provide direct evidence for the functional role of C-terminal domain in stabilization of the catalytic N-terminal domain of SARS coronavirus main protease.

SOLUTION: Reversible Unfolding of the Severe Acute Respiratory Syndrome Coronavirus Main Protease in Guanidinium Chloride

PROBLEM: Influenza infection is a major cause of morbidity and mortality worldwide, especially during pandemics outbreaks. Emerging data indicate that phase II antioxidant enzyme pathways could play a role in virusassociated inflammation and immune clearance. While Nrf2-dependent gene expression is known to modify inflammation, a mechanistic role in viral susceptibility and clearance has yet to be elucidated. Therefore, we utilized differentiated human nasal epithelial cells (NEC) and an enzymatic virus-like particle entry assay, to examine the role Nrf2-dependent gene expression has on viral entry and replication. Herein, lentiviral vectors that express Nrf2-specific short hairpin (sh)-RNA effectively decreased both Nrf2 mRNA and Nrf2 protein expression in transduced human NEC from healthy volunteers. Nrf2 knockdown correlated with a significant increase in influenza virus entry and replication. Conversely, supplementation with the potent Nrf2 activators sulforaphane (SFN) and epigallocatechin gallate (EGCG) significantly decreased viral entry and replication. The suppressive effects of EGCG on viral replication were abolished in cells with knocked-down Nrf2 expression, suggesting a causal relationship between the EGCG-induced activation of Nrf2 and the ability to protect against viral infection. Interestingly, the induction of Nrf2 via nutritional supplements SFN and EGCG increased antiviral mediators/responses: RIG-I, IFN-, and MxA at baseline in the absence of infection. Our data indicate that there is an inverse relationship between the levels of Nrf2 expression and the viral entry/ replication. We also demonstrate that supplementation with Nrf2-activating antioxidants inhibits viral replication in human NEC, which may prove to be an attractive therapeutic intervention. Taken together, these data indicate potential mechanisms by which Nrf2-dependent gene expression regulates susceptibility to influenza in human epithelial cells.

SOLUTION: Nrf2 expression modifies influenza A entry and replication in nasal epithelial cells

PROBLEM: A new virus isolated from the lungs of rats is prevalent in colony reared and wild rats and induces a fatal pneumonitis in newborn rats. The virus, designated as rat coronavirus (RCV), exhibits properties representative of the coronavirus group: characteristic surface structure, particles somewhat variable in size averaging approximately 90 m~z, apparent R2ffA content, essential lipid, heat sensitivity, and a close serologic relationship with the mouse hepatitis virus complex. I~CV grows well in primary rat kidney cell cultures, exhibits a pathognomonic type CPE, and produces a complement fixing antigen which is sensitive for detection of antibody and useful in sero-epidemiologie studies.

SOLUTION:
Rat Coronavirus (RCV): A Prevalent, Naturally Occurring Pneumotropie Virus of Rats 1