Question

T/F (TRUE/FALSE) ASAP PLEASEE ANSWER ALL

1.The enzymes in Covid-19 are translated as two related megaproteins and then released by proteolysis.

2.In matrix-assisted laser desorption ionization (MALDI), the laser irradiates aromatic residues in peptides and the matrix supplies protons to promote ionization

Answer 1

1. True

The viral replicase is produced by translation of the partly overlapping open reading frames (ORF) 1a and 1ab. Expression of ORF 1ab needs a -1 ribosomal frameshift near the end of ORF1a. SARS-CoV genome translation yields the large replicase polyproteins pp1a (4,382 aa) and pp1ab (7,073 aa). Extensive autoproteolytic processing, mediated by two ORF1a-encoded protease domains generates 16 viral non-structural proteins.

Reference:

a. PUBMED PMID: 18451981

2. True

Primary ionization in MALDI remains controversial. Two main approaches are the cluster and pooling/photoionization models. The analyte molecules are ionized by being protonated or deprotonated in the hot plume of ablated gases, and then they can be accelerated into whichever mass spectrometer is used to analyse them. Suitable matrix compounds are determined based on some specific molecular design considerations. They are often acidic, therefore act as a proton source to encourage ionization of the analyte. Basic matrices have also been reported.

References:

a. Knochenmuss, R. (2006). Ion formation mechanisms in UV-MALDI. The Analyst, 131(9), 966. doi:10.1039/b605646f

b. Fitzgerald, M. C., Parr, G. R., & Smith, L. M. (1993). Basic matrixes for the matrix-assisted laser desorption/ionization mass spectrometry of proteins and oligonucleotides. Analytical Chemistry, 65(22), 3204–3211. doi:10.1021/ac00070a007

c. https://en.wikipedia.org/wiki/Matrix-assisted_laser_desorption/ionization