Protein sequence and structure: Is one more fundamental than the other?

We argue that protein native state structures reside in a novel "phase" of matter which confers on proteins their many amazing characteristics. This phase arises from the common features of all globular proteins and is characterized by a sequence-independent free energy landscape with relatively few low energy minima with funnel-like character. The choice of a sequence that fits well into one of these predetermined structures facilitates rapid and cooperative folding. Our model calculations show that this novel phase facilitates the formation of an efficient route for sequence design starting from random peptides.Comment: 7 pages, 4 figures, to appear in J. Stat. Phy

Non-vacuum Solutions of Bianchi Type VI_0 Universe in f(R) Gravity

In this paper, we solve the field equations in metric f(R) gravity for Bianchi type VI_0 spacetime and discuss evolution of the expanding universe. We find two types of non-vacuum solutions by taking isotropic and anisotropic fluids as the source of matter and dark energy. The physical behavior of these solutions is analyzed and compared in the future evolution with the help of some physical and geometrical parameters. It is concluded that in the presence of isotropic fluid, the model has singularity at $\tilde{t}=0$ and represents continuously expanding shearing universe currently entering into phantom phase. In anisotropic fluid, the model has no initial singularity and exhibits the uniform accelerating expansion. However, the spacetime does not achieve isotropy as $t\rightarrow\infty$ in both of these solutions.Comment: 20 pages, 5 figures, accepted for publication in Astrophys. Space Sc

A study of the morphologies and growth kinetics of three monodisperse n-alkanes: C122H246, C162H326 and C246H494

An optical and electron microscopic study has been made of three monodisperse n-alkanes crystallising as extended-chain lamellae. All showed similar morphologies at the same supercooling and the same progressive changes of texture with crystallization temperature. This is, with increasing supercooling, from a morphology composed essentially of individual lamellae arranged in parallel stacks and radiating from common nuclei through coarse, somewhat branched microstructures whose parallel stacks diverge, to finer, more-branched pseudo-spherulitic textures. Quenched, once-folded, C-246 shows a random spherulitic texture with a dominant/subsidiary microstructure as for polymeric systems. The kinetics of extended-chain growth increase linearly with supercooling, as predicted by Hoffman, except for a local dip at the onset of lamellar branching. This new phenomenon occurs within one quantized state of lamellar thickness in contrast to 'self-poisoning' when once-folded forms give way to extended-chain crystallization. When dominant lamellae are no longer parallel but diverge, their mutual splaying angles increase with supercooling for all the three n-alkanes studied. The values are less, for the same supercooling, for the longer homologues with their thicker lamellae. This behaviour is as expected of transient ciliation due to the excess of molecular length over that of the secondary nucleus and thereby reinforces previous evidence demonstrating the responsibility of ciliation for spherulitic development in polymers