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Neuraminidase (NA) is an important protein for the replication cycle of influenza A viruses. NA is an enzyme that cleaves the sialic acid receptors; this process plays a significant role in viral life cycle. Blocking NA with a specific inhibitor is an effective way to treat the flu. However, some strains show resistance to current drugs. Therefore, NA is the focus for the intense research for new antiviral drugs and also for the explanation of the functions of new mutations. This research focuses on determining the profile of variability and phylogenetic analysis and finding the correlated mutations within a set of 149 sequences of NA belonging to various strains of influenza A virus. In this study, we have used the original programs (Corm, Consensus Constructor, and SSSSg) and also other bioinformatics software. NA proteins are characterized by various levels of variability in different regions, which was presented in detail with the aid of ConSurf. The use of four independent methods to create the phylogenetic trees gave some new data on the evolutionary relationship within the NA family proteins. The search for correlated mutations shows several potentially important correlated positions that were not reported previously to be significant. The use of such an approach can be potentially important and gives new information regarding NA proteins of influenza A virus.
Hemagglutinin (HA) is a surface glycoprotein found in influenza viruses. This particle plays two crucial functions in the viral life cycle: it allows for the attachment of the virus into the host cell and participates in the fusion of the virus and host membranes. There are 18 different subtypes of HA. Recently, the H17 and H18 strains have been discovered whose hosts were bats. The evolution of these two strains had most likely occurred in isolation for a long period of time. This work presents the phylogenetic analysis and study on mutational variability based on sequences from all 18 currently known HA strains belonging to influenza virus type A. The results have been presented regarding the current knowledge about influenza. The classical software (Clustal, PHYLIP, and ConSurf) as well as original applications (SSSSg and Consensus Constructor) have been used in this research.
A point and a straight line are fundamental objects of Euclidean geometry which is taught at basic and secondary schools. Philosophers meditated on the nature of a point and a straight line long before Euclid (from the 6th century BC). But it was Euclid (about 325-265 BC) who delimited the concept of a point and a straight line (and others) in the First book of his Elements (Stocheia) by means of a definition. The phylogenesis of a point and its relation to a straight line is marked out by names such as Viéte, Kepler, Leibniz, Newton, Bolzano and Cantor. Students meet the concept of a point before they start to create their geometrical structures. Our analysis will try to show that there is a strong parallel between the ontogenetic and phylogenetic aspects of the conception of a point and its relation to a straight line, a ray and/or a segment.
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