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.

Q: 2H phosphoesterases catalyze reactions on nucleotide substrates and contain two conserved histidine residues in the active site. Very limited information is currently available on the details of the active site and substrate/product binding during the catalytic cycle of these enzymes. We performed a comprehensive X-ray crystallographic study of mouse 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), a membraneassociated enzyme present at high levels in the tetrapod myelin sheath. We determined crystal structures of the CNPase phosphodiesterase domain complexed with substrate, product, and phosphorothioate analogues. The data provide detailed information on the CNPase reaction mechanism, including substrate binding mode and coordination of the nucleophilic water molecule. Linked to the reaction, an open/close motion of the β5-α7 loop is observed. The role of the N terminus of helix α7-unique for CNPase in the 2H family-during the reaction indicates that 2H phosphoesterases differ in their respective reaction mechanisms despite the conserved catalytic residues. Furthermore, based on small-angle X-ray scattering, we present a model for the full-length enzyme, indicating that the two domains of CNPase form an elongated molecule. Finally, based on our structural data and a comprehensive bioinformatics study, we discuss the conservation of CNPase in various organisms.

A: Crystallographic Analysis of the Reaction Cycle of 2′,3′-Cyclic Nucleotide 3′-Phosphodiesterase, a Unique Member of the 2H Phosphoesterase Family
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Q: The emerging novel human betacoronavirus 2c EMC/2012 (HCoV-EMC) was recently isolated from patients with severe pneumonia and renal failure and was associated with an unexplained high crude fatality rate of 56%. We performed a cell line susceptibility study with 28 cell lines. HCoV-EMC was found to infect the human respiratory tract ( polarized airway epithelium cell line Calu-3, embryonic fibroblast cell line HFL, and lung adenocarcinoma cell line A549), kidney (embryonic kidney cell line HEK), intestinal tract (colorectal adenocarcinoma cell line Caco-2), liver cells (hepatocellular carcinoma cell line Huh-7), and histiocytes (malignant histiocytoma cell line His-1), as evident by detection of high or increasing viral load in culture supernatants, detection of viral nucleoprotein expression by immunostaining, and/or detection of cytopathic effects. Although an infected human neuronal cell line (NT2) and infected monocyte and T lymphocyte cell lines (THP-1, U937, and H9) had increased viral loads, their relatively lower viral production corroborated with absent nucleoprotein expression and cytopathic effects. This range of human tissue tropism is broader than that for all other HCoVs, including SARS coronavirus, HCoV-OC43, HCoV-HKU1, HCoV-229E, and HCoV-NL63, which may explain the high mortality associated with this disease. A recent cell line susceptibility study showed that HCoV-EMC can infect primate, porcine, and bat cells and therefore may jump interspecies barriers. We found that HCoV-EMC can also infect civet lung fibroblast and rabbit kidney cell lines. These findings have important implications for the diagnosis, pathogenesis, and transmission of HCoV-EMC.

A: Differential Cell Line Susceptibility to the Emerging Novel Human Betacoronavirus 2c EMC/2012: Implications for Disease Pathogenesis and Clinical Manifestation
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Q: Due to its excessively high capacity for human-to-human transmission, the 2019 novel coronavirus disease , first reported in Wuhan in China, spread rapidly to the entire nation and beyond, and has now been declared a global public health emergency. Understanding the transmission pattern of the virus and the efficacy of transmission control measures is crucial to ensuring regional and global disease control. Here we propose a simple model based on exponential infectious growth, but with a timevarying, largely damping, transmission rate. This model provides an excellent fit to the existing data from the 102 countries and regions which have reported cases for more than 6 days, and, we think, has largely captured the transmission patterns of the COVID-19 outbreak under a variety of intervention and control measures. We found that the damping rate, defined as the rate of the exponential decline in transmission rate, ranged from -0.125 to 0.513 d -1 globally (a negative damping rate represents acceleration in spread). The estimated peak time (when the fastest spread occurs) and the final number of infections were found to be greatly affected by the damping rate. Successful control measures, such as those implemented in China and South Korea, have resulted in a clear pattern of exponential damping in the viral spread (also shown during the 2003 outbreak of Severe Acute Respiratory Syndrome, SARS). The damping rate, therefore, could be used as an indicator for the efficacy of implemented control measures. Our model suggests that the COVID-19 outbreak is currently accelerating worldwide, especially rapidly in certain countries (e.g. USA and Australia) where exponential damping is yet to emerge. Consistent with the message from the World Health Organisation (WHO), we thus strongly suggest all countries to take active measures to contain this global pandemic. Slight increments in the damping rate from additional control efforts, especially in countries showing weak or no exponential damping in COVID-19 transmission, could lead to a radically more positive outcome in the fight to contain the pandemic.

A:
Exponential damping: The key to successful containment of COVID-19
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