Zaza Jaliashvili

Photoplethysmography (PPG) is a photometric technique which is widely used in the detection of time-dependent blood volume changes in the peripheral tissues of the body. Despite the long history of research, the detailed mechanism of this phenomenon is still a matter of debates. This applies to such important body locations as the projection of the radial artery on the wrist. Based on the above, our goal is to determine the mechanism of the PPG-signal formation at this particular location. In this paper, we analyze a series of observations obtained using reflection-mode PPG. In our experiments, photoplethysmograms were recorded in the wavelength range of 400 – 1000 nm (with a step of 1 nm). Recordings were made for 10 s and the time step was 16.5 ms. Measurements were carried out in vivo on the projection of the radial artery of the wrist. The observed photoplethysmograms are described by modification of the physiological model of the interaction of light with living tissue proposed several years ago. This model provides a reasonable explanation for all observations. According to this model, it is the pulsating transmural pressure of the radial artery that increases/decreases the density of capillaries in the dermis, thereby modulating the volume of blood in the capillary bed. The photoplethysmogram observed in the green/blue range of the optical spectrum was due to modulation of the blood volume in the capillary bed. In the yellow-red and near infrared ranges, the PPG signal was a modulated blood volume in the capillary bed and artery. For these ranges, differences in the PPG signal shapes are not observed. Differences are observed only in intensities, which is proportional to the amount of blood in the area of interaction. The PPG signal is also modulated by the respiratory rate.

The goal of present research is the absorption-spectroscopic studies of resonance interaction of silver atoms in different conditions: 1. In silver nanoparticle; 2. Bound to double helix of DNA; 3. In complex with oligodeoxynucleotides (dodecamer d(CGCGAATTCGCG)); 4. Incapsulated in polyamidoamine (PAMAM) of fourth generation G4 (~4 nm); 5. Absorbed by cellophane membrane. It is shown that AgNPs represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs - DNA complex DNA dependant conformational transition takes place due to fast and intensive heating. It is shown also that in the interaction of atoms of silver reduced by ascorbic acid and in photo - desorption of AgNPs DNA double helix serves as a matrix, namely together with the silver atoms forms the rigid one-dimensional periodic structure.

1) The aim of the present work is spectroscopic and thermodynamic study of DNA catalytic properties in the following processes: a) redox; b) formation of inter-strand cross-links; c) performing of photodynamic effects; d) nanoscale resonance radiationless electron excitation energy transfer. The most attention is paid to the latter, as truly nanoscale method in its origin. The nanoscale method of laser induced fluorescence resonance energy transfer (FRET) to donor (acridine orange) – acceptor (ethidium bromide) intercalator pair for quantitative and qualitative study of stability quality DNA double helix in solution in real time is offered. FRET method allows to estimate the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjected to stress effect. It gives the opportunity to compare various types of DNAs with 1) different origin; 2) various damage degrees; 3) being in various functional states. Alternative model and mechanisms of photodynamic effect on DNA in solutions are proposed. They are based on photoenergy degradation in solutions. The energy activates electrolytic dissociation of water molecules on H3O+ and OH–f and acts as a catalyst for hydrolysis reactions of phosphordiester and glycoside linkages. 2) Soft ions, in particular Cu+, Ag+, Pt++, and Hg++ ions, are able to form the so-called inter-strand crosslinks in DNA. Let’s consider the process in case of Ag+. First, silver ions are adsorbed on DNA major groove (N7G or chelate complex N7G and O6G). At small silver ion concentration on DNA does not cause ejection of AO and EB. On the other hand, silver ions at interaction with DNA induce double proton transfer in GC pair [1]. Chelate complex with silver ions makes it easy to unfold DNA double helix with wrong Watson–Crick GC pair. The work presents electron configuration of GC atom pairs taking part in H-bonds before and after DPT. In the last process Guanine’s atom O6 is in enol form, nitrogen atom N1G is in pyridine state and N3C in pyrole state. After unfolding of double helix in neutral water solution N3C atom cannot keep enol state in a long time and it should transfer into its usual pyridine state. At the same time silver ions can with definite possibility attack nitrogen atoms N1G still existing in pyridine state.

Multi-purpose, compact, precessional, mobile, low-power (most measurements can be made with a car battery) optical device are presented. Building this tool does not require large financial outlays.

By spectroscopic and microcalorimetric methods we have studied the interaction of AgNPs with DNA macromolecules in various environment conditions (ionic strength, dielectrical penetrability, temperature and photo-irradiation). Toxicity of AgNPs in chemo- and photo-chemo-therapy is discussed based on the example of DNA macromolecule. It is sown that photo-irradiation, heating (100 grad C), interaction with denaturized DNA and ethanol leads to the decomposition of nanoparticles to atoms and even ions.The strong toxicity means cell distruction and can serve as a potetial medical treatment for healing cancer.

1) By spectroscopic and microcalorimetric methods we have studied the interaction of AgNPs with DNA macromolecules in various environment conditions (ionic strength, dielectrical penetrability, temperature and photo-irradiation). Toxicity of AgNPs in chemo- and photo-chemo-therapy is discussed based on the example of DNA macromolecule. It is sown that photo-irradiation, heating (100 grad C), interaction with denaturized DNA and ethanol leads to the decomposition of nanoparticles to atoms and even ions.The strong toxicity means cell distruction and can serve as a potetial medical treatment for healing cancer; 2) წარმოდგენილია მღვრიე, ფლუორესცირებად გარემოში - ბიოლოგიურ ქსოვილში ფლუორესცენციის სპექტრების დაყვანილი ფორმ-ფაქტრორების ანალიზზე დაფუძნებული სამედიცინო დიაგნოსტირების განხორციელების ეფექტური მეთოდი, რომლის მგრძნობელობა და სპეციფიურობა აღემატება 90%. აღწერილია შესაბამისი დანადგარი - ლაბორატორიული ოპტიკურ/ლაზერული ბიოსპექტრომეტრი. 

We present another point of view to the problem of randomness and chirality of the packed DNA. Our consideration related to the algorithms that generate the random distribution of equivalent polygons with zero volume and confined to spherical volumes, as well as Alexander polynomials, which does not distinguish completely among some kntted chains and so are not a good invariants. We present the new invariants based on Vassiliev polynomials, which are free of above mentioned constraints.

We present the homemade laser spectrometer. An important part of this spectroscopic system is ultraviolet coherent and non-coherent radiation. It is obtained by converting the fundamental mode of the YAG: Nd3 + laser radiation to the third (by mixing the basic and second harmonics) and the fourth (by doubling the 2nd harmonic) harmonics and the nitrogen laser, while the non-coherent source is YLiF4: Tm3 + system. This range of optical radiation allows to realize the laser-induced and / or non-coherent-source fluorescence of biological objects, which is the most informative method for studying electromagnetic interactions along with other methods of laser / optical spectroscopy. Therefore our UV system is very effective for medical diagnosis.

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Scientific editor of monographs in foreign languages

Scientific editor of a monograph in Georgian

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Research articles in high impact factor and local Scientific Journals

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