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6. Physics behind the Conformational Transitions in Biopolymers. Demystification of DNA melting and Protein FoldingArtem Badasyan, invited lecture at foreign university Abstract: 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.
Found in: osebi
Keywords: Biophysics, protein folding, helix-coil transition, spin models
Published: 13.12.2016; Views: 4923; Downloads: 0
 Fulltext (136,69 KB) |
7. Growth mechanism and structure of electrochemically synthesized dendritic polymethylsilane moleculesMatjaž Valant, Gregor Mali, Artem Badasyan, Andraž Mavrič, 2017, original scientific article Abstract: The study of an electrochemical synthesis of polymethylsilane from trifunctional trichloro-
methylsilane monomers identified a single polymerization pathway involving reduction of the
monomer to silyl anions and their addition to the growing polymer. The sizes of the synthesized
macromolecules, measured with dynamic light scattering, are much larger than the theoretical
size estimated for an ideal dendrimer. The reason for this, found by NMR analysis, is in a large
number of branching irregularities (defects) contained in the molecular structure, which can be
described as a hyperbranched dendritic polymer. Theoretical estimates of sizes for an ideal
dendrimer were corrected assuming a branching defect is a cavity with the volume of one
monomer. Appropriateness of the theoretical and experimental models was confirmed with a
good quantitative agreement between the experimental densities and the theoretically calculated
values.
Found in: osebi
Keywords: Polymethylsilane
Dendritic polymer
Electropolymerization
Published: 20.03.2017; Views: 3733; Downloads: 9
Fulltext (705,04 KB) |
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10. FROM SPINODAL DECOMPOSITION AND MOLECULAR DISPERSION OF POLYSILANES TO SUPER-HARD NANOCOATINGArtem Badasyan, Boštjan Mavrič, Matjaž Valant, published scientific conference contribution abstract Abstract: Conformations of polymer molecules in solution crucially depend on the sign of the
effective potential energy of interaction between the monomers, also known as the
quality of solvent. Therefore in “poor” solvent regime, when effective attraction
overwhelms, the experimental measurements of polymer sizes are complicated by the
agglomeration of macromolecules, followed by precipitation. This phenomenon, also
known as spinodal decomposition, causes serious problems when the goal is to
determine properties of individual macromolecules. Interestingly, while in the case of
carbon-based polymers the precipitation-related problems can be easily avoided with
dilution, this is not the case for polysilanes, i.e. polymeric chains on basis of silicon.
Although the linear polysilanes were first synthesized in early 1920’s, the aggregationrelated
problems have hampered their studies and applicability until recently.
In the Materials Research Laboratory of University of Nova Gorica we have developed
a technology to strengthen the scratch-resistance nanocoating for glass on the basis of
polysilane dendritic polymers we synthesized. Through the prism of the Flory-Huggins
theory, that provides a miscibility phase diagram in temperature-volume fraction
variables, the quality of polymer solution can be manipulated by changing the
temperature. Using Dynamic Light Scattering (DLS) and Differential Scanning
Calorimetry (DSC) we have managed to show, that at temperatures in the range of 40-
50 C the deagglomeration of the dendritic polysilane takes place in tetrahydrofuran
(THF) [1], and the system becomes a true molecular dispersion with particles 20 nm in
size [2]. Introducing such molecular dispersion into the alumina precursor solution
yields an amorphous nanocomposite stabilized by a high level of strain. This resulted in
an extraordinary increase of hardness and scratch resistance of the alumina – polymer
nanocomposite coating that can be used for glass protection [3].
Found in: osebi
Keywords: Polysilane, dendrimer, solubility
Published: 12.09.2017; Views: 3675; Downloads: 0
Fulltext (53,55 KB) |
