Flexible filamentous viruses make up a large fraction of the known plant viruses, but in comparison with those of other viruses, very little is known about their structures. We have used fiber diffraction, cryo-electron microscopy, and scanning transmission electron microscopy to determine the symmetry of a potyvirus, soybean mosaic virus; to confirm the symmetry of a potexvirus, potato virus X...

The shape of the building blocks plays a crucial role in directing self-assembly towards desired architectures. Out of the many different shapes, the helix has a unique position. Helical structures are ubiquitous in nature and a helical shape is exhibited by the most important biopolymers like polynucleotides, polypeptides and polysaccharides as well as by cellular organelles like flagella. Hel...

Abstract De novo protein design is advancing rapidly. However, most designs are for single states. Here we report a de designed peptide that forms multiple ?-helical-bundle states accessible and interconvertible under the same conditions. Usually in such amphipathic ? helices associate to form compact structures with consolidated hydrophobic cores. recent rational computational have delivered o...

The decapeptides Boc-Aib-L-Val-Aib-Aib-(L-Val)3-Aib-L-Val-Aib-OMe and Boc-Aib-L-LeuAibAib-(L-Leu),-Aib-L-Leu-Aib-OMe have been studied in CDC1, and (CD,),SO solutions by 270-MHz' H-nmr. In CDCl,, the presence of eight intramolecularly hydrogen-bonded N H groups has been established, consistent with a 3,,,-helical conformation, for both decapeptides. In (CD,),SO, only seven solvent-shielded NH g...

Cryo-electron microscopy (cryo-EM) enables the imaging of macromolecular complexes in near-native environments at resolutions that often permit the visualization of secondary structure elements. For example, alpha helices frequently show consistent patterns in volumetric maps, exhibiting rod-like structures of high density. Here, we introduce VolTrac (Volume Tracer) - a novel technique for the ...

The ability of oligodeoxynucleotides to form specific triple helical structures with critical regulatory sequences in the human dihydrofolate reductase (DHFR) promoter was investigated. A battery of purine-rich oligonucleotides targeted to the two purine.pyrimidine strand biased regions near the DHFR transcription initiation site was developed. The stable triple helical structures formed by bin...

We elucidate the structural transitions in a helical off-lattice homopolymer induced by crowding agents, as a function of the number of monomers (N) and volume fraction (varphi c) of crowding particles. At varphic=0, the homopolymer undergoes transitions from a random coil to a helix, helical hairpin HH, and helix bundle HB structures depending on N, and temperature. Crowding induces chain comp...

We investigate the emergence of chiral meso-structures in one-dimensional fluids consisting of stacked discotic particles and demonstrate that helical undulations are generated spontaneously from internal elastic stresses. The stability of these helical conformations arises from an interplay between long-ranged soft repulsions and nanopore confinement which is naturally present in columnar liqu...