Methylation of RNA Cap in SARS-CoV-2 captured by serial crystallography

ABSTRACTThe genome of the SARS-CoV-2 coronavirus contains 29 proteins, of which 15 are nonstructural. Nsp10 and Nsp16 form a complex responsible for the capping of mRNA at the 5′ terminus. In the methylation reaction the S-adenosyl-L-methionine serves as the donor of the methyl group that is transferred to Cap-0 at the first transcribed nucleotide to create Cap-1. The presence of Cap-1 makes viral RNAs mimic the host transcripts and prevents their degradation. To investigate the 2′-O methyltransferase activity of SARS-CoV-2 Nsp10/16, we applied fixed-target serial synchrotron crystallography (SSX) which allows for physiological temperature data collection from thousands of crystals, significantly reducing the x-ray dose while maintaining a biologically relevant temperature. We determined crystal structures of Nsp10/16 that revealed the states before and after the methylation reaction, for the first time illustrating coronavirus Nsp10/16 complexes with the m7GpppAm2′-O Cap-1, where 2′OH of ribose is methylated. We compare these structures with structures of Nsp10/16 at 297 K and 100 K collected from a single crystal. This data provide important mechanistic insight and can be used to design small molecules that inhibit viral RNA maturation making SARS-CoV-2 sensitive to host innate response.

Selective utilization of methoxy groups in lignin for N-methylation reaction of anilines

Methoxy groups in lignin were selectively valorised as a methyl source for the N-methylation reaction of amines.

Synthesis Isoflavones Derivate: 7-Hydroxy-3',4’-Dimethoxyisoflavone, 7,3’,4’-Trimethoxyisoflavone and 7-O-Acetyl-3’,4’-Dimethoxyisoflavone

Some Isoflavones 7-hydroxy-3',4'-dimethoxyisoflavone (2), 7,3',4'-trimethoxyisoflavone (3) and 7-O-acetyl-3',4'-dimethoxyisoflavone (4) have been synthesized through cyclization reaction of deoxybenzoine using a reagent mixture BF3.Et2O , DMF and POCl3. The DMF reagent was added aiming to add one carbon to form isoflavone 1. The deoxybenzoine (3,4-dimethoxybenzyl-2', 4'-dihydroxyphenylketone, (1) was synthesized by reacting 3,4-dimethoxy benzyl carboxylic acid and resorcinol through Friedel Craft acylation using a Lewis acid (BF3) as a catalyst. The isoflavones 1 was converted into isoflavone 2 via methylation reaction using dimethylsulfate (DMS) and K2CO3 and conversions into isoflavone3 through acetylation reaction using acetylchloride. The results were analyzed using FTIR, GC-MS and 1H NMR spectrometers. Deoxybenzoine derivatives of 3,4-dimethoxybenzyl-2',4'-dihydroxy phenylketone was yielded in 57% with m.p 171-172 °C. The isoflavone 1, 2 and 3 was produced in 58, 52 and 53 % yield, respectively.