The properties of biopolymer DNA - acridine orange films were studied by optical methods. Relaxation kinetics of
holographic diffraction gratings through triplet states of the dye bound to DNA has been examined. The kinetic curves
are readily approximated by biexponential function that can be attributed to presence of two types of dye - biopolymer
binding sites. The electron and infrared spectra show that under room humidity DNA exists in denatured form in the film
and a part of dye molecules are bound to polymer as dimers.
The present work is devoted to investigation of holographic recording features in medium composed of bipolymer film of DNA, sensitized by organic dyes to He-Ne and YAG-Nd lasers radiation. Two types of holograms formed in the system of dye-DNA by two different modes of recording were studied: (1) transmission holograms recorded by a stationary He-Ne-laser with diffraction efficiency of order 0.02%. (2) Relief-phase holograms (RPH) recorded by a pulse YAG-Nd laser with a diffraction efficiency of order 5%. Despite distinction in efficiency and recording mechanisms the explored holograms are combined by one general property -- they disappear spontaneously during the few hours. The results of the work allow to make conclusions about mechanisms of recording and erasure of holograms, as well as to determine diffusion coefficients in dry film of DNA at a room temperature.
The thionine photoreduction kinetics in film of polyvinyl-alcohol is proposed to describe as the consecutive reaction with one equilibrium stage: (formula given in paper). To given scheme the values of k2 = (3,60 ± 0,26)•10-3 s-1 and k3=(2,93 ± 0,56)•10-3 s-1 are determined. The values of k1 constant demonstrate the linear dependence on laser intensity.
Various ways of photomodification of nucleic acids by laser radiation of a visible range are considered in the work The molecules of xhantene dyes participate in all cases of modification. Dye acts as a mediator between laser radiation and macromolecule.
In the work the various types of holographic recording in the media based on organic dye methylene blue (MB) in polymer matrices are investigated. An interest to this subject is due to the employment of MB as the basic element or the sensitizer for many recording materials and as effective generator of singlet oxygen too. Three forms of holograms are observed and investigated: relief-phase holograms with diffraction efficiency more than 20% recorded in pulse regime; photochemical amplitude holograms based on MB photobleaching; dynamic triplet holograms. The mechanisms of recording and the scope for erasing of holograms are analyzed.
In the present paper we investigate two different holographic record modes realized in dye-polymer media. Both methods - dynamic and stationary - are applicable to the same sample and are reversible. Dynamic recording is caused by triplet photochromism of dyes and it may be used to receive versatile information about photophysical properties of substances. Stationary relief-phase holograms are recorded through heat generation under laser radiation is absorbing and are noted for high diffraction efficiencies. Scanning probe microscope was used to instigate the relief- phase holographic grating.