Thermal degradation of biological DNA studied by dielectric spectroscopy

Dielectric spectroscopy was tested as an alternative tool to study degradation of deoxyribonucleic acid (DNA) in its solid form. The specimens, prepared from biological DNA, were periodically heated and cooled according to a programmed scheme. Simultaneously, their dielectric parameters (permittivity and dielectric loss) were monitored as function of frequency and temperature. The analysis of Bode plots allowed to determine the upper limit of thermal stability of solid DNA at 120 °C, because heating at higher temperatures resulted in irreversible changes. These changes were identified as denaturation by gel electrophoresis and UV–vis absorption methods

Properties of DNA-CTMA monolayers obtained by Langmuir-Blodgett technique

The complex consisting of DNA and cetyltrimethylammonium chloride (DNA-CTMA) is extensively exploited in organic electronics in form of thin films with submicron or nanometer thickness. In this work, using the Langmuir-Blodgett technique, the surface films were prepared from complexes based on different types of chromosomal and plasmid DNA. The research focused on changes in their continuity after they were transferred onto a solid substrate. It was found that only the monolayer of plasmid DNA-CTMA complex remained continuous after being transferred. The other complexes underwent a spontaneous self-assembling and created elongated linear patterns. AFM images of these patterns were analysed quantitatively with Fast Fourier Transform. It was confirmed that self-assembling occurred along one privileged direction

Hydration properties of selected DNA-lipid complexes

Zbadano dwa modelowe kompleksy lipidowe DNA z surfaktantami zawierającymi jeden (CTMA) lub dwa (DDCA) łańcuchy alifatyczne. Wyznaczono kinetykę ich hydratacji oraz izotermę sorpcyjną. Wykazano, że zastosowanie lipidowego surfaktantu z udziałem dwóch łańcuchów alifatycznych ogranicza liczbę cząsteczek wody trwale związanej z helisą DNA.Two model DNA-lipid complexes with the surfactants containing single (CTMA) or double (DDCA) aliphatic chains were investigated. Hydration kinetics and sorption isotherms were determined. The data were interpreted using BET and Dent sorption isotherm models. It was found that the use of lipid surfactant with double aliphatic chain reduce the number of water molecules tightly and permanently bound to DNA helix

Changes in Optical Parameters of SiO2:TiO2 Films Obtained by Sol-Gel Method Observed as a Result of Thermal Treatment

The research focused on materials having potential applications in technology of planar evanescent wave sensors. Four samples of binary SiO2:TiO2 thin films having different titania content were manufactured through the sol-gel method and dip-coating technique on polished silicon substrates. The samples were subjected to repeated heating/cooling protocols. Simultaneously, their optical parameters were monitored by spectroscopic ellipsometry as they evolved under varying temperature. Subsequent analysis confirmed linear dependence of refractive index on titania content, at least in vis-NIR wavelengths, as well as a low value of the thermal expansion coefficient. It was shown that the thickness of SiO2:TiO2 films decreased as a result of annealing processes, which may be a consequence of reduced porosity

Thermal stability of the solid DNA as a novel optical material

Deoxyribonucleic acid (DNA) has been extensively exploited for the past decade as the matrix material in organic electronics and nonlinear optics. In this work thermal stability of DNA in solid form was thoroughly studied, mainly by optical methods. Solid samples of low molecular mass DNA were subjected to heating according to different protocols and dissolved. The temperature effect was observed in the evolution of UV absorption and circular dichroism spectra. Thin films of DNA were deposited on polished silicon wafers. They were conditioned at consecutively raised temperature and simultaneously measured by spectroscopic ellipsometry. Changes in chemical composition of thermally treated films were studied by XPS. Below 100 $^{\circ}$C all thermal effects were reversible. Melting occurred at c.a.140 $^{\circ}$C. Irreversible chemical changes probably occurred at 170-180 $^{\circ}$C

Thermal annealing effect on physical properties of DNA–CTMA thin films

DNA–CTMA is a material of increasing interest in the domain of organic electronics and photonics. How- ever, its physical properties are not sufficiently understood. In this work DNA–CTMA thin films were sub- jected to thermal annealing. Annealing courses was monitored in situ by spectroscopic ellipsometry, infrared spectroscopy and dielectric spectroscopy. The results suggest existence of an irreversible struc- tural transition, occurring at a temperature adjacent to 150 ° C