MethodsDesign, data-processing and modelling: DNA sequences were designed using our own algorithms based on sequence symmetry minimization implemented in Matlab and C (available at http://www.dna.caltech.edu/DNAdesign/). Curve fits for persistence length data and models for lattice strain energies were calculated in Matlab.Molecular models were constructed and visualized using a combination of NAMOT, RasMol, and PyMol (scripts and coordinates at http://www.dna.caltech.edu/SupplementaryMaterial/).The molecular models are for visualization only and have not been subjected to molecular dynamics calculations.DNA sample preparation: Lyophilized HPLC-or PAGEpurified DNA oligonucleotides were purchased from Integrated DNA Technologies (Coralville, IA), resuspended in water, quantitated by UV absorbance at 260 nm, and stored at -20• C. All samples were prepared in a 1X Tris-Acetate-EDTA (TAE) buffer with 12.5 mM magnesium acetate (pH=8.3). An equimolar mixture of strands (5 strands if one tile, 10 strands if two) was annealed from 95• C to 25• C (fluorescence microscopy) steps in a PCR machine (Eppendorf Mastercycler). For AFM, each strand was present at 200 nM, for fluorescence microscopy the total concentration of tiles was kept at 400 nM. For fluorescence microscopy, a single fluorescein-labeled strand was incorporated into each tile; the position of the dye was varied from the 5 end of the #3 strand to the 5 end of the #5 strand with no apparent effect. AFM of REp+SEp(3:FAM) was similar to that of REp+SEp.Preparation of PVP coated glass: Adapted from.1 Microscope slides and coverslips were washed in 1M NaOH for 1 hour, rinsed thoroughly with de-ionized (DI) water and immersed in 1% v/v acetic acid solution for 2 hours. Then, they were rinsed again with DI water and silanized in a 1% v/v 3-(trimethoxysilyl)propylmethacrylate (Aldrich) in 1% v/v acetic acid for 36 hours. For polymer coating, 500 mL of a 4% w/v Mw = 360, 000 poly(vinylpyrrolidone) (PVP, USB Corp.) solution with 2.5 mL of 10% w/w ammonium persulfate solution and 250 µl of N,N,N ,N -tetramethylethylenediamine (TEMED, Acros) was prepared. Slides and coverslips were incubated in the PVP solution at 80• C for 18 hours. They were then rinsed and stored in DI water. Coating was stable for at least 2 weeks.Preparation for fluorescence microscopy: Samples were left overnight at room temperature after annealing. Immediately prior to use, a PVP-coated microscope slide and coverslip were rinsed with ethanol and dried. Then, 2.6 µl of solution containing DNA tubes and oxygen scavenging system (0.035 mg/ml catalase, 0.2 mg/ml glucose oxidase, 4.5 mg/ml glucose, 5% β-mercaptoethanol) was deposited onto the slide, covered with the coverslip and sealed with epoxy or parafin. The distance between slide and coverslip was ≈5 µm and the thickness of sample solution was typically narrowed to ≈3 µm by the PVP coating.Fluorescence microscopy: Samples were imaged on an inverted microscope (IX 70, Olympus) with 100X/1.40 NA oil immersion and 40X/0.75 NA air objectives. Blue lig...

Coronavirus belongs to the family of Coronaviridae, comprising single-stranded, positive-sense RNA genome (+ ssRNA) of around 26 to 32 kilobases, and has been known to cause infection to a myriad of mammalian hosts, such as humans, cats, bats, civets, dogs, and camels with varied consequences in terms of death and debilitation. Strikingly, novel coronavirus (2019-nCoV), later renamed as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), and found to be the causative agent of coronavirus disease-19 (COVID-19), shows 88% of sequence identity with bat-SL-CoVZC45 and bat-SL-CoVZXC21, 79% with SARS-CoV and 50% with MERS-CoV, respectively. Despite key amino acid residual variability, there is an incredible structural similarity between the receptor binding domain (RBD) of spike protein (S) of SARS-CoV-2 and SARS-CoV. During infection, spike protein of SARS-CoV-2 compared to SARS-CoV displays 10–20 times greater affinity for its cognate host cell receptor, angiotensin-converting enzyme 2 (ACE2), leading proteolytic cleavage of S protein by transmembrane protease serine 2 (TMPRSS2). Following cellular entry, the ORF-1a and ORF-1ab, located downstream to 5′ end of + ssRNA genome, undergo translation, thereby forming two large polyproteins, pp1a and pp1ab. These polyproteins, following protease-induced cleavage and molecular assembly, form functional viral RNA polymerase, also referred to as replicase. Thereafter, uninterrupted orchestrated replication-transcription molecular events lead to the synthesis of multiple nested sets of subgenomic mRNAs (sgRNAs), which are finally translated to several structural and accessory proteins participating in structure formation and various molecular functions of virus, respectively. These multiple structural proteins assemble and encapsulate genomic RNA (gRNA), resulting in numerous viral progenies, which eventually exit the host cell, and spread infection to rest of the body. In this review, we primarily focus on genomic organization, structural and non-structural protein components, and potential prospective molecular targets for development of therapeutic drugs, convalescent plasm therapy, and a myriad of potential vaccines to tackle SARS-CoV-2 infection.

Surgery, internal medicine, pediatrics, orthopedics, and ophthalmology were the most preferred specialty choices. Gender preference was observed to affect choices of few specialties such as orthopedics and obstetrics/gynecology. Perceptions which have an impact on specialty selection of male and female students may reflect a different tempo of growing up in men and women.

We present the first direct observations of tile-based DNA self-assembly in solution using fluorescent nanotubes composed of a single tile. The nanotubes reach tens of microns in length by end-to-end joining rather than by sequential addition of single tiles. Their exponential length distributions withstand dilution but decay via scission upon heating, with an energy barrier Esc approximately 180kBT. DNA nanotubes are thus uniquely accessible equilibrium polymers that enable new approaches to optimizing DNA-based programming and understanding the biologically programmed self-assembly of protein polymers.