α-Helical transmembrane proteins are a ubiquitous and important class of proteins, but present difficulties for crystallographic structure solution. Here, the effectiveness of the AMPLE molecular replacement pipeline in solving α-helical transmembrane-protein structures is assessed using a small library of eight ideal helices, as well as search models derived from ab initio models generated bot...

Structural transformations of superparamagnetic colloids confined within self-assembled microtubes are studied by systematically varying tube-colloid size ratios and external magnetic field directions. A magnetic field parallel to microtubes may stretch non-linear chains like zigzag chains into linear chains. Non-parallel fields induce new structures including repulsive chains of single colloid...

Biological molecules can form hydrogen bonds between nearby residues, leading to helical secondary structures. The associated reduction of configurational entropy leads to a temperature dependence of this effect: the helix-coil transition. Since the formation of helices implies a dramatic shortening of the polymer dimensions, an externally imposed end-to-end distance R affects the equilibrium h...

The relative noninvasive nature, easy accessibility, convenience and accuracy of helical CT in the rapid evaluation of not only the aorta and its branches, but the entire thorax/abdomen, makes it the best suited imaging modality for use in evaluation of aortic aneurysms and dissection. Excellent vascular opacification, the advantage of reconstructing overlapping scans without respiratory misreg...

In addition to conventional planar and helical flagellar waves, insect sperm flagella have also been observed to display a double-wave structure characterized by the presence of two superimposed helical waves. In this paper, we present a hydrodynamic investigation of the locomotion of insect spermatozoa exhibiting the double-wave structure, idealized here as superhelical waves. Resolving the hy...

The folding of a polypeptide is an example of the cooperative effects of the amino-acid residues. Of recent interest is how a secondary structure, such as a helix, spontaneously forms during the collapse of a peptide from an initial denatured state. The Monte Carlo implementation of a recent helix-forming model enables us to study the entire folding process dynamically. As shown by the computer...

The helical ribosome structures of Mycoplasma gallisepticum have been analyzed by optical diffraction and the rotational symmetry technique. The helix repeat (510 A) is composed of 10 ribosomes in 3 turns. The rotational studies show some ribosome fine structure.

Molecular hydrocarbons are well-known to polymerize under pressure to form covalently bonded frameworks. Here we predict by ab initio calculations two distinct three-dimensional hydrocarbon crystalline structures composed of 3-fold and 4-fold helical CH chains in rhombohedral (R3) and tetragonal (I4₁/a) symmetry, respectively. Both structures with 1:1 stoichiometry are found to be energetically...

Direct near field electrospinning is used to produce very long helical polystyrene microfibers in water. The pitch length of helices can be controlled by changing the applied voltage, allowing to produce both micro springs and microchannels. Using a novel high frequency variable voltage electrospinning method we found the helix formation speed and compared the experimental buckling frequency to...

The structures of free-standing zirconium nanowires with 0.6−2.8 nm in diameter are systematically studied by using genetic algorithm simulations with a tight-binding many body potential. Several multi-shell growth sequences with cylindrical structures are obtained. These multi-shell structures are composed of coaxial atomic shells with the threeand four-strands helical, centered pentagonal and...