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Entropic cost of folding and phase diagrams of polypeptides: Why are IDPs unfolded at room temperature?
Artem Badasyan, predavanje na tuji univerzi

Opis: In spin models, that are applied to describe the conformational transitions in polymers, the number of spin orientations, that correspond to the disordered conformation, can be estimated using fundamental definitions of Statistical Physics. For instance, when considering alpha-helix to coil transition in polypeptides, the role of generalized coordinates is played by pairs of torsional angle, and the repeating unit populates different regions of that 2D contour map, depending on conformation. By scanning over all possible torsional angles, that do not violate the obvious limitations due to the excluded volume, the so-called Ramachandran map can be plotted, which is actually the phase space visualization for the helix-coil transition problem. The region of phase space, corresponding to the ordered, helical conformations, is much more limited, than the one, corresponding to all other (allowed) conformations. We can calculate the areas of these regions as Γhelix and Γcoil , and construct the ratio Q = Γcoil . Naturally, it can be interpreted as log(Q) = Scoil − Shelix = ΔS, the entropic cost of helix with respect to coil. To illustrate the importance of the entropic price of ordered conformation we report our recent results, that allowed to explain the peculiarity of phase diagrams of Intrinsically Disordered Proteins (IDP) out of larger Q-values, as compared to globular counterparts. In particular, it has been shown, that due to larger Q, the phase diagram of IDP is shifted towards higher temperatures.
Najdeno v: ključnih besedah
Povzetek najdenega: ...IDP, protein folding, phase diagram...
Ključne besede: IDP, protein folding, phase diagram
Objavljeno: 23.06.2016; Ogledov: 1676; Prenosov: 0
.pdf Polno besedilo (2,96 MB)
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Physics behind the Conformational Transitions in Biopolymers. Demystification of DNA melting and Protein Folding
Artem V. Badasyan, predavanje na tuji univerzi

Opis: Biophysics is the area of research, devoted to the studies of physical problems related to living systems. Animal cell is the smallest unit of an organism and mainly contains water solutions of structurally inhomogeneous polymers of biological origin: polypeptides (proteins) and polynucleotides (DNA, RNA). Statistical physics of macromolecules allows to describe the conformations of both synthetic and bio-polymers and constitutes the basis of Biophysics. During the talk I will report on the biophysical problems I have solved with numerical simulations (Langevin-based Molecular Dynamics of Go-like protein folding model and Monte Carlo with Wang-Landau sampling) and analytical studies of spin models (formula evaluation by hand, enforced with computer algebra systems). The direct connections with the theory of phase transitions, algebra of non-commutative operators and decorated spin models will be elucidated.
Najdeno v: ključnih besedah
Ključne besede: Biophysics, protein folding, helix-coil transition, spin models
Objavljeno: 13.12.2016; Ogledov: 1527; Prenosov: 0
.pdf Polno besedilo (136,69 KB)

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