David V. Svintradze

UV-vis and FT-IR spectra of ultraviolet irradiated collagen in the presence of antioxidant ascorbic acid.

The influence of deleterious UV radiation on collagen molecules in the absence and presence of ascorbic acid using UV-vis and FT-IR spectroscopy has been studied. Intensity of UV-vis absorption spectrum of collagen with a maximum at 275 m due to the aromatic residues (tyrosine and phenylalanine) increases with the increasing dose of UV radiation. This effect is significantly hindered in the presence of antioxidant ascorbic acid. Intensities of FT-IR bands (amide A, B, I and II) of collagen decrease with the increase of the UV radiation dosage. Intensities of bands are also decreased in the presence of ascorbic acid. Results suggest that increasing the concentration of ascorbic acid increases the photo-stability of collagen, and the collagen becomes less sensitive to UV radiation. It is possible that hydrogen bonds form between the groups N-H of collagen and C=O of ascorbic acid. It is believed that under UV radiation free radicals appear in acid soluble collagen and resulting in photodegradation of the macromolecule restore due to the ability of ascorbic acid donating one or two electrons. Increasing the dose of radiation causes more molecules of ascorbic acid to slow down, and their antioxidant effect is diminished accordingly.

Nanoscale measurements of the assembly of collagen to fibrils

Observing the self-assembly of collagen from single collagen monomers to higher order fibrils and fibers provides a bottom-up approach to engineering its ultrastructure in comparison to structural studies of already formed collagen fibers. This approach can be used for the fabrication of controlled collagen-based biomaterials with varying mechanical properties. Here, we investigate the time-dependent self-assembly of collagen into single fibrils in vitro through high resolution imaging of collagen type 1 prior to fibrillogenesis. This was confirmed by comparing persistence length and diameter in controlled experiments and studying the morphology and mechanical properties of nanoscale collagen fibrils through AFM nanoindentation measurements. The Youngs modulus of these collagen fibrils was estimated to be around 1GPa in the dehydrated state. The stability and mechanical characteristics of collagen obtained in these experiments indicate the hierarchical assembly occurs at both a structural and mechanical level.

A Theoretical Model for Metal Corrosion Degradation

Many aluminum and stainless steel alloys contain thin oxide layers on the metal surface which greatly reduce the corrosion rate. Pitting corrosion, a result of localized breakdown of such films, results in accelerated dissolution of the underlying metal through pits. Many researchers have studied pitting corrosion for several decades and the exact governing equation for corrosion pit degradation has not been obtained. In this study, the governing equation for corrosion degradation due to pitting corrosion behavior was derived from solid-state physics and some solutions and simulations are presented and discussed.

Optimization of hydrogen bonds for combined DNA/collagen complex

Many natural and biological systems including collagen and DNA polymers are formed by a process of molecular self-assembly. In this paper, we developed two novel structural models and built heterogeneous DNA/collagen complexes through a preferable arrangement of multiple hydrogen bonds (H-bonds) between DNA and collagen molecules. The simulation results based on three sets of criteria indicate that one of the models with five collagen molecules, which are positioned around each strand of DNA molecules emerged to form a suitable polymer complex with the maximum number of H-bonds. Our predictions quantitatively validated and agreed with the molecular structure reported by Mrevlishvili and Svintradze [2005. Int. J. Biol. Macromol. 36, 324-326].

Moving Manifolds in Electromagnetic Fields

We propose dynamic non-linear equations for moving surfaces in electromagnetic field. The field is induced by a material body with a boundary of the surface. Correspondingly the potential energy, set by the field at the boundary, can be written as an addition of four-potential times four-current to a contraction of electromagnetic tensor. Proper application of minimal action principle to the system Lagrangian yields dynamic non-linear equations for moving three dimensional manifolds in electromagnetic fields. The equations, in different conditions simplify to Maxwell equations for massless three surfaces, to Euler equations for dynamic fluid, to magneto-hydrodynamic equations and to Poisson-Boltzmann equation. To illustrate effectiveness of the equations of motion we apply the formalism to analyze dynamics of macro-molecules and membranes.

Topology of Gene Delivery Systems

Gene therapy is a promising future of the treatment of diseases, but it faces problem such is: DNA or RNA (gene vectors), after administration into a living body become deactivated due to immunological reaction or enzymatic attack. Solution is gene delivery systems or gene vector binding inactive materials. If the gene vector is embedded in inactive biomaterial then it is protected from immunological reaction, but, so far, it is not fully understand which bioinactive material is the most effective for designing self gene delivery systems (gene delivery systems with no side effects). The nature found solution to the problem in a simple manner: adenoviruses. But viruses have side effects, obviously because function of viruses is predetermined to be effective, careless of side effects, delivery machines. There are, commonly used three different types of gene delivery systems: cationic lipid based delivery, adenovirus based delivery and protein based delivery systems. We show that all the above mentioned delivery systems have similar topology which becomes visible only after proper application of geometric topology to macromolecules. The question to ask is whether the similar topology is occasional or it is the necessary topology for gene delivery systems. More precisely: is the host cell sensitive to the geometric structures of the delivery systems? The analyses of existing structural data about delivery systems allow us to answer the questions. The comparison of topology of gene delivery system to the possible topology of nuclear pore system shows that pore topology is similar to the topology of gene delivery system. The similarity between gene delivery systems is governed by topology of gene and is dictated by structure of DNA.