Novel antiviral active molecule 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro- phenyl)acetamide has been synthesised and characterized by FT-IR and FT-Raman spectra. The equilibrium geometry, natural bond orbital calculations and vibrational assignments have been carried out using density functional B3LYP method with the 6-311G++(d,p) basis set. The complete vibrational assignments for all the vibrational modes have been supported by normal coordinate analysis, force constants and potential energy distributions. A detailed analysis of the intermolecular interactions has been performed based on the Hirshfeld surfaces. Drug likeness has been carried out based on Lipinski's rule and the absorption, distribution, metabolism, excretion and toxicity of the title molecule has been calculated. Antiviral potency of 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro-phenyl) acetamide has been investigated by docking against SARS-CoV-2 protein. The optimized geometry shows near-planarity between the phenyl ring and the pyrimidine ring. Differences in the geometries due to the substitution of the most electronegative fluorine atom and intermolecular contacts due to amino pyrimidine were analyzed. NBO analysis reveals the formation of two strong stable hydrogen bonded N–H···N intermolecular interactions and weak intramolecular interactions C–H···O and N–H···O. The Hirshfeld surfaces and consequently the 2D-fingerprint confirm the nature of intermolecular interactions and their quantitative contributions towards the crystal packing. The red shift in N–H stretching frequency exposed from IR substantiate the formation of N–H···N intermolecular hydrogen bond. Drug likeness and absorption, distribution, metabolism, excretion and toxicity properties analysis gives an idea about the pharmacokinetic properties of the title molecule. The binding energy −8.7 kcal/mol of the nonbonding interaction present a clear view that 2- [(4,6-diaminopyrimidin-2-yl)sulfanyl]-N-(4-fluoro- phenyl) acetamide can irreversibly interact with SARS-CoV-2 protease.

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Agglutinins/lectins are conventionally defined as proteins/ glycoproteins of non-immune origin with a remarkable ability to specifically and reversibly interact with carbohydrate ligands. Lectins from different sources may essentially exhibit common biological activities. This study was therefore undertaken to survey naturally occurring agglutinins in two species of marine crabs by hemagglutination assay using mammalian erythrocytes. Hemagglutination assay results showed that the hemolymph of the marine crab Grapsus albolineatus showed the highest HA titer with rat erythrocytes. HA titer of the crab Leptodius sanguineus varied from 0 to 32 with all the tested erythrocytes. Among the various tissues of Grapsus albolineatus analyzed for the presence of agglutinins, hemagglutination activity was observed in the hemolymph and hepatopancreas with rat erythrocytes. HA was determined by both male and female crabs of Grapsus albolineatus. HA activity increased with an increase in animal size. Biochemical factors like water, protein and calcium content of the hemolymph did not have any influence on the HA titer.