Protolytic and partition equilibria of indicator dyes in the model lipid systems have been analyzed. A methodological approach has been developed allowing the partition coefficients of the protonated and deprotonated dye forms to be derived from spectrophotometric measurements. The most effective ways of employing the indicator dyes for monitoring the changes in the lipid bilayer properties have been suggested.

Dispersions of carbon nanotubes (NT) in liquid crystals have been considered as a model system for studies of anisotropic intermolecular interactions in condensed organic media. Electric conductivity data were obtained for nematic liquid crystals (LC) with small (0,01 - 0,15 wt %) concentrations of multiwall NT dispersed therein. The electric conductivity increased noticeably with NT concentration in the LC matrix, suggesting a percolation-like behaviour at NT content in the LC matrix below ~ 0,01 wt %. A marked difference in the measured electric conductivity values for the LC matrices of different polarity (e.g., cyanobiphenyl and azoxy) was observed. Assuming that supramolecular arrangement of NT dispersed in the LC matrix can be treated in a manner similar to the conventional non-mesogenic dopants, the observed behaviour is explained using our recent theoretical description of intermolecular interactions in anisotropic organic media formed by particles of essentially different size and anisometry.

The structures of films received by evaporation from solutions of Na - DNA of calf thymus with concentration of 0,2 mg/ml, containing salts Li, K, Na, Cs, Mg, Zn, Ca are analyzed at various levels of relative humidity and temperatures. The solution of salt of Na - DNA in volume of 0,5 ml was poured into a glass quartz cell placed in a hermetic closed vessel with inputs for air pumping. The cell has an area of <$E 420~roman mm sup 2> and height of lateral walls of 1 mm. The error of stabilization of temperature in the thermostat came to 0,5 <$E symbol Р>C, the error of humidity is 2 %. The research was carried out at temperatures of 30 and 40 <$E symbol Р>C. The received films of Na - DNA were photographed in white polarized light. The volume of the formed liquid crystal phase depends on the type of ions in Na - DNA solutions and defines correlation between the area of structure on the film and the area of all the film and depends on the correlation of concentrations of salt of metal and DNA. The area occupied by liquid crystal structures was calculated as the area limited to a curve, connecting boundary elements of structures. The relative areas of structures received from solutions containing salt of NaCl with concentrations of 20 and 1,25 mM have values of 0,73 and 0,09 accordingly. The films containing salt of MgCl2 has spherulite structures collapsing under the conditions of room temperature and humidity.

The films received from the solutions containing salt LiCl, CsCl, CaCl2 or MgCl2 with the concentration of 10 mМ do not form structures with the allocated direction of growth of clusters. The films received from the solutions containing salt NaCl with the concentration of 10 mМ and salts ZnCl2, or CuCl2 with the concentration of 0,4 mМ and 0,2 mМ respectively do not form structures with the allocated direction of growth of clusters also. It is assumed, film can be characterised by a set of values of fractal dimensions; one of the signs of existence of DNA in native form is the presence of such fractal structures as percolation anisotropic cluster in the received film.

С помощью модельной системы лизоцим - липид оценена применимость тиофлавина T (ThT) для определения амилоидо-подобных агрегатов, образующихся в мембранном окружении. Установлено, что ThT способен встраиваться в липидный бислой, состоящий из цвитерионного 1-пальмитоил-2-олеил-sn-глицеро-3-фосфохолин (POPC) и анионного 1-пальмитоил-2-олеил-sn-глицеро-3-фосфоглицерол (POPG) фосфолипидов. Обнаружена способность ThT к неспецифической ассоциации с нативным лизоцимом. Эти свойства ThT могут расширить границы применения этого красителя для определения мембранно-индуцированных фибриллярных структур.

The possible consequences of chlorpromazine (CP) effect at low concentrations after its incorporation into erythrocyte membranes were analysed. Erythrocyte distribution by spherical index and the rate of hemolysis in hypotonic medium were studied in 0,125 mM and 0,25 mM CP. The investigation showed the non-uniform response of erythrocytes from different donors to CP introduced into suspension. Samples were divided into two groups according tо their reaction to CP. In the first group of donors the CP introduction invoke full or partial shift of the distribution curves towards larger values of spherical index. In the second group CP introduction resulted in the rise of cell density in low spherical index interval. Thus the interaction of amphiphile substances with a membrane bilayer can evoke controversial effects. One of the possible effects of CP is intercalation of alkyl regions into the membrane bilayer. This can lead to an increase of membrane surface. On the other hand amphiphile incorporation into lipid bilayer can lead to the formation of inverted micelles. In this case the membrane surface diminishes comparing to the native one at the expense of transition of a part of membrane material to the described phase. Thus both the phenomena of stretching and constriction of membrane surface are equally probable in the studied CP concentration interval and depend on the population state of a donor.

Досліджено вплив кардіоліпіну на структурний стан модельних мембран за допомогою методу ексимеризації пірена. Відношення інтенсивності флуоресценції ексимерів до інтенсивності мономерів зменшилось на 11 % у разі підвищення концентрації кардіоліпіну від 0 до 10 %, що можна пояснити конденсацією ліпідного бішару. У разі збільшення концентрації кардіоліпіну до 20 і 40 % відношення інтенсивності ексимерів до інтенсивності мономерів зростало, що свідчить про зменшення щільності пакування ліпідних молекул. Обговорено біологічну роль кардіоліпіну.

The effect of cationic drug chlorpromazine (CPZ) on the structural state of model lipid membranes composed of zwitterionic phospholipid phosphatidylcholine (PC) and anionic phospholipid cardiolipin (CL) in molar ratios 8:2 and 3:2 has been investigated using the indicator dye Neutral Red (NR). CPZ incorporation into the PC/CL (8:2) liposomes led to the increase of NR partition coefficients. This effect was interpreted in terms of drug-induced membrane disordering. In contrast, CPZ association with PC/CL (3:2) lipid bilayers suppressed the dye partition which was assumed to be a result of lipid phase transition.

Хвильові феномени спостережено в численних експериментах з цілісними рослинами. Один з можливих механізмів дальньої високошвидкісної сигналізації у рослин пов'язаний з концентраційними хвилями, які розповсюджуються по провідних системах рослин. Розглянуто одновимірну вісесиметричну стаціонарну течію в'язкої рідини з осмотично активною компонентою, яка розчинена у рідині, як модель провідної судини рослини. Постійна концентрація компоненти на кінцях судини підтримується клітинками вегетативних органів рослини. Одержано нелінійний розподіл концентрацій увздовж трубки та параболічні профілі швидкості руху рідини. Досліджено розповсюдження малих збурень концентрації та швидкості вздовж трубки. Наведено вираз для швидкості U розповсюдження хвиль. Діапазон U = 20 - 60 м/с одержано шляхом числових розрахунків у разі варіації параметрів системи у фізіологічних межах значень. Теоретичні розрахунки затримки за часом у випадку передачі сигналу між кореневою системою та листками рослини відповідають експериментальним даним. Таким чином, концентраційні хвилі можуть опосередкувати високошвидкісну передачу інформації між органами рослини.

Lanthanide coordination complexes have found numerous applications in a number of areas, including laser techniques, fluorescent analysis, biomedical assays. Likewise, they exhibit antitumor properties. Eu(III) tris-<$E beta>-diketonato complexes (EC) are newly synthesized compounds with high anticancer activity. Despite extensive studies, the detailed mechanism of their biological effects is far from being resolved. Examining the interactions between EC and biological molecules in model systems is essential for deeper understanding of the mechanisms behind their biological activity. In the present work we employed fluorescent probe acridine orange (AO) to investigate EC-DNA interaction. AO-DNA binding was followed by the marked fluorescence increase detected at 530 nm. EC addition suppressed this fluorescent changes. EC were found to differ in their ability to modify AO-DNA interactions. EC4 and EC6 have demonstrated the most pronounced effect on AO-DNA binding. AO-DNA complexation occurs predominantly via intercalation mode. EC are large planar structures, whose DNA intercalating ability was reported to increase with the planarity of ligands. It seems likely that AO and EC can compete for the binding sites on DNA molecule.

A number of so-called conformational diseases (Parkinson's, Alzheimer's and Huntington's diseases, type II diabetes, spongiform encephalopathies, systemic amyloidosis) are associated with the deposition in various tissues highly-ordered protein aggregates (amyloid fibrils) that kill cells or prevent them from functioning properly. Amyloid fibrils are organized in a cross <$E beta>-structure with a helical array of <$E beta>-sheets, in which the long axis of the fibril is parallel to the long axis of the helix and is perpendicular to the <$E beta>-strands Amyloid can be identified using a range of techniques: electron and atomic force microscopy, X-ray fibril diffraction, thioflavin T fluorescence, Congo Red (CR) birefringence or spectrophotometric assay. However, therapeutic detection of amyloid fibrils with CR test may be hampered by CR ability to form complexes with native proteins. In the present study we investigated CR binding to a series of native proteins - hemoglobin (Hb), cytochrome c (cyt c), ribonuclease A (RNase), human serum albumin (HSA). CR interaction with Hb and cyt c was followed by absorbance decrease and long wavelength shift of spectrum maximum in the case of Hb, indicating that native protein structure contains binding sites for CR. Association constant (<$EK sub b>) and binding stoichiometry (n) recovered from the data analysis within the framework

of Langmuir adsorption model were found to be: <$EK sub b~=~(2,1~symbol С~ 0,3)~times~10 sup 5~roman M sup -1>, <$E n~=~3,3~symbol С~0,5> for Hb and <$EK sub b~=~(6,0~symbol С~ 0,9)~times~10 sup 4~roman M sup -1>, <$E n~=~1,0 ~symbol С~0,3> for cyt c. The presence of lipid vesicles composed of phosphatidylcholine and cardiolipin did not exert influence on CR - Hb interactions. In contrast, association constant for CR - cyt c complexation markedly increased. This finding was interpreted in terms of cyt c unfolding at lipid-water interface coupled with exposure of additional CR binding sites on the protein surface. Formation of CR complexes with RNase and HSA was followed by the long-wavelength shift of absorption maxima. CR - HSA binding curves have Langmuir-like shape, whereas CR - RNase adsorption isotherms are slightly sigmoidal pointing to cooperative nature of the binding process. The binding parameters were estimated to be <$EK sub b~=~(1,3 ~symbol С~ 0,3)~times~10 sup 4~roman M sup -1>, <$E n~=~2,3 ~symbol С~ 0,5> for HSA and <$EK sub b~=~(3,4 ~symbol С~ 0,3)~times~10 sup 4~roman M sup -1>, <$E n~=~0,6~symbol С~ 0,1> and Hill parameter <$E alpha~=~1,1~symbol С~0,2> for RNase.

Для получения новой информации о каталитических свойствах фермента, адсорбированного на поверхности липидных везикул, проведен кинетический анализ процесса окисления глюкозы глюкозооксидазой. За ходом ферментативной реакции наблюдали спектрофотометрически, применив pH-индикатор - нейтральный красный. Нейтральные, положительно или отрицательно заряженные липосомы изготовлены из яичного фосфатидилхолина или его смесей с цетилтриметиламмония бромидом (5 мол %) или кардиолипином (5 мол %). Найдена кажущаяся константа диссоциации нейтрального красного в этих системах в присутствии глюкозооксидазы. Ассоциация фермента с липосомами не вызвала изменения кинетических параметров взаимодействия глюкозооксидазы с глюкозой и кислородом.

Artemisinin-type agents are well known as effective antimalarial medicines and recently their anticancer activity was reported, however there is lack of investigations on the molecular mechanisms of antitumor activity of artemisinin and its derivatives. This study is aimed at the examining of mechanisms of artemisinin-type agents anticancer activity. DNA as carrier of genetic information is one of the major targets for antitumor drugs effect and nucleic acids are also suggested as molecular targets of artemisinin action in cancer cells. Biologically significant intermolecular interactions of artemisinin and dihydroartemisinin with some purine and pyrimidine nucleobases were studied by means of testing the drug-nitrogen base mixtures by electrospray ionization mass spectrometry. The peaks of stable noncovalent complexes of the artemisinin-type drug with Ade, Cyt, and mThy were registered in the mass spectra. Comparison of the relative abundances of the peaks of the drug-nucleobase complexes for purine and pyrimidine nitrogen bases was performed. The spectra analysis allowed us to conclude that an effectiveness of the complexation process depends on the structural peculiarities of the drugs and nucleobases molecules. The experimental data and features of the molecular structure of the drugs and nucleobases testify to the suggestion that noncovalent complexes of the artemisinin-type agents and nitrogen bases are stabilized by van der Waals forces and hydrogen bonds between the functional groups of the interacting molecules. Formation of the

supramolecular complexes of the artemisinin-type drugs and nucleobases is considered as a possible molecular mechanism of anticancer activity of the studied antimalarial agents. The obtained results demonstrate the great potential of electrospray ionization mass spectrometry method in the study of the artemisinin-type agents and their intermolecular interactions related to the mechanisms of the drugs biological activity.

Показано, что литический пептид мелиттин (М), его аналог [Ala-14]мелиттин (P14A) и цельный пчелиный яд (ПЯ) действуют различным образом в отношении эритроцитов человека. Нормализированная скорость гемолиза линейно зависела от относительного количества P14A в смеси с М и ПЯ. Кривые зависимости доза-ответ для P14A продемонстрировали насыщение только тогда, когда мембранносвязанный М был ингибирован хлорпромазином. Это показывает, что М и P14A вызывают гемолиз, действуя независимо один от другого. В отличие от М, но аналогично ПЯ P14A также уменьшал объем лизированных клеток. Нелинейные эффекты при сжатии клеток, индуцированные смесями P14A с М и ПЯ предполагают, что в основе этого явления лежит синергетическое взаимодействие между пептидами. Полученные данные показывают, что М и P14A вызывают гемолиз посредством связывания с различными классами участков связывания на мембране эритроцитов. Таким образом, структура пептида является определяющим фактором, который в совокупности с конкретной последовательностью взаимодействия пептида с мембраной обеспечивает его литические свойства.

Despite considerable research efforts, the molecular mechanisms of anaesthetic action still remain the matter of extensive debates. According to one viewpoint, anaesthetics alter the properties of lipid bilayer which, in turn, affects the functions of embedded membrane proteins. In contrast, protein-based theories of anaesthetic action postulate that the drugs modulate the functions of membrane proteins through direct association. To develop a unique conception of anaesthesia further in-depth investigations of drug-membrane interactions are strongly required. In the present work a well-known fluorescent probe pyrene has been employed to gain molecular insights into the interactions between amphipathic phenothiazine derivative chlorpromazine (CPZ) and model membranes composed of cationic globular protein lysozyme (Lz), and lipid vesicles prepared from zwitterionic lipid phosphatidylcholine (PC) and its mixtures with anionic lipid cardiolipin (CL) in the molar ratios 19:1, 9:1 and 4:1. To give unambiguous interpretation of the drug effect on protein-lipid interactions, we first analyzed the changes in pyrene excimerization due to the formation of either CPZ-lipid or Lz-lipid complexes. Pyrene excimer-to-monomer intensity ratio (E/M), a parameter which reflects the alterations in membrane free volume, was found to decrease upon Lz or CPZ binding to the lipid vesicles. Apparently, embedment of the protein and drug molecules into the hydrophobic region of lipid bilayer gives rise to the increase in lipid packing, decrease in the rate of trans-gauche isomerization of the lipid acyl chains and, consequently, reduction of membrane

free volume. At the next of the stude, we analysed the changes in the rate of pyrene excimerization upon Lz addition to drug-lipid mixtures. In CL-containing liposomes the presence of CPZ does not modify the magnitude and sign of protein effect on membrane free volume. This implies that CPZ is incapable of perturbing Lz structure and exerted no influence on the protein interactions with this kind of liposomes. In contrast, in PC vesicles E/M ratio appeared to increase upon lysozyme binding to CPZ-modified model membranes. This finding may be explained in terms of two possibilities: CPZ induces the formation of the new Lz conformer whose interactions with lipid bilayers are accompanied by the increase in membrane free volume; CPZ imparts the positive charge to the lipid bilayer thereby preventing Lz penetration into hydrophobic membrane region. Interfacially-located protein molecules are likely to generate structural defects coupled with the increased bilayer free volume. The results presented here clearly demonstrate that membrane composition can modulate the drug action on lipid-protein interactions. The recovered difference between CPZ effect on Lz-lipid binding in PC and CL-containing bilayers provide support to the idea that membrane environment can stabilize certain protein conformations differing in their responsiveness to drug action.

Fluorescence spectroscopy is one of the most powerful tools providing new insights into the structural, dynamic and functional behavior of biological macromolecules, being particularly useful in investigating the molecular details of protein-lipid association. Complete and accurate information about the conformational dynamics of protein molecules can be obtained using tryptophan (Trp) residues as intrinsic fluorescence probes. The fluorescence of indole chromophore is extremely sensitive to environment making it an ideal choice for reporting protein conformational transitions upon membrane interactions. Hen egg white lysozyme (Lz) is a multi-tryptophan protein which is extensively used in elucidating fundamental aspects of protein-lipid interactions. The main emitters responsible for 80 % of lysozyme fluorescence are Trp62 and Trp108. The present study was undertaken to ascertain the alterations in lysozyme structural state upon association with model membranes composed of zwitterionic lipid 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and anionic lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol. Fluorescence lifetime measurements showed that intensity-averaged lifetime (<$E<< tau >> >) of Trp residues in lysozyme decreased upon the protein binding to model membranes. Furthermore, <$E<< tau >> > reduction from 1,94 to 1,74 ns was observed at decreasing lipid-to-protein molar ratio (L:P) from 1130 to 120. It was suggested that Trp specific interactions with certain amino acid residues in its surroundings is the main factor responsible for the recovered decrease in

tryptophan lifetime and the observed contradictions between lifetime, quenching and steady-state experiments. Since Lz is a stable protein whose conformation is reported to change insignificantly upon the formation of protein-lipid contacts, it can be assumed that the processes behind the drop in <$E<< tau >> > involve Lz self-association in membrane-bound state. Trp62 and Trp108 are located in the protein active site which reportedly participates in Lz aggregation. Moreover, Cys76-Cys94 disulfide bridge capable of efficient quenching of Trp fluorescence and reducing the lifetime of protein fluorophores, also resides in the active site cleft. Thus, it may be supposed that interactions between Trp62 and Trp108 of one Lz monomeric molecule with disulfide bridge of another monomeric molecule during the protein aggregation result in reduction of <$E<< tau >> > values. The <$E<< tau >> > dependence on L:P can be explained by the fact that lysozyme self-association is apparently coverage-dependent process controlled by both electrostatic and hydrophobic protein-lipid interactions. Additional arguments in favor of the assumption on Lz aggregation come from the time-resolved anisotropy measurements. Lysozyme rotational correlation time which reflects the motion of the whole protein molecule, was found to exhibit twofold increase at increasing L:P values. The recovered membrane ability to modulate Lz aggregation behavior may largely determine the bactericidal and amyloidogenic propensities of this protein.

Development of new formulations of antineoplastic drugs currently represents extensively growing research area. Efficiency of existing anti-tumor drugs is frequently limited by their high general toxicity, metabolic instability in an organism and bad penetration into a cancer cell. Besides, insignificant direct influence on tumoral growth also limits the application of antineoplastic drugs in a free form. One efficient way of drug delivery is based on the use of lipid vesicles (liposomes). Liposomes are spherical, self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside and between the lipid bilayers. The lipid bilayer favors solubilization of hydrophobic compounds, whereas internal aqueous phase of lipid vesicles is suitable for encapsulation of hydrophilic drugs. Design of liposomal carriers is heavily based on the evaluation of bilayer-modifying properties of the drug. This is important not only for achieving maximum payload without compromising liposome stability, but also for prediction of therapeutic and toxic effects of a certain compound, because membrane interactions may prove critical for drug absorption, distribution, metabolism and elimination in an organism. In the present work the effect of the two potential antineoplastic drugs - europium coordination complexes (LC) - on the physicochemical properties of phosphatidylcholine (PC) model membranes has been investigated using the environmentally-sensitive pH indicator dye bromothymol blue (BTB). This dye responds to the changes in environmental conditions by the shifts of its protolytic and partition equlibria. Incorporation

of LC into the lipid vesicles was found to exert no influence on the effective electrostatic potential of model membranes, i.e. the mean potential at location of the dye prototropic moiety in the interfacial region. In contrast, BTB membrane partitioning markedly enhanced in the presence of drugs, indicating that europium coordination complexes can affect molecular organization of a lipid bilayer, presumably through generation of structural defects and altering the conformation of PC headgroups. High lipophilicity of Eu(III) coordination complexes together with their relatively weak membrane-modifying propensities create prerequisites for the development of liposomal formulations of these compounds.

Among a wide variety of drug nanocarriers developed to date, liposome-based delivery systems are particularly attractive due to their advantageous features such as biocompatibility, complete biodegradability, low toxicity, ability to carry both hydrophilic and lipophilic payloads and protect them from chemical degradation and transformation, increased therapeutic index of a drug, improved pharmacokinetic and pharmacodynamic profiles compared to free drugs, reduced side effects, etc. The efficiency of drug encapsulation is largely determined by its membrane-partitioning properties as well as physicochemical characteristics of the lipid vesicles. In the present study we concentrated our efforts on the pre-formulation studies of the two synthesized Eu(III) coordination complexes, V3 and V4, the potential anticancer drugs. More specifically, our goal was twofold: to characterize the membrane partition properties of these complexes, and to assess how the lipid-associating ability of V3 and V4 depends on membrane structural state being varied by introducing the different amounts of cholesterol

(Chol) into phosphatidylcholine (PC) lipid vesicles. To achieve this goal, several fluorescent probes including pyrene, 1,6-diphenyl-1,3,5-hexatriene (DPH), and 4-p-(dimethylaminostyryl)-1-dodecylpyridinium (DSP-12) have been employed. Partition coefficients of lanthanides determined using the equilibrium dialysis technique proved to depend on the amount of Chol content. Formation of drug-lipid complexes was found to affect pyrene excimerization and DSP-12 spectral properties but exerted no influence on pyrene vibronic structure and DPH anisotropy. Membrane composition was shown to have an impact on the spectral responses of the probes in drug-lipid systems. This finding was interpreted as arising from the sterol condensing effect on the structural state of the lipid bilayer.

Currently there is a growing interest in screening of new drugs, capable of destroying cancer cells effectively, without damaging health tissues. In this context the potential of liposomes as a drug carrier system is extensively investigated [1-3]. Liposomes are nanosize particles in which lipid bilayer encloses an aqueous internal compartment. Size, charge and surface properties of liposomes can be easily changed simply by adding new ingredients to the lipid mixture before liposome preparation or by variation of preparation techniques. Another important feature is that lipid vesicles can entrap both hydrophilic and hydrophobic pharmaceutical agents. Liposome delivery systems can enhance drug solubility, reduce toxicity associated with free anticancer drugs and improve stability of the drug by protecting the compound from chemical degradation or transformation. However, the therapeutic and toxic effects of drug are strongly determined by the degree or efficiency of its loading into the liposomes. For this reason, while using liposomes as delivery systems for hydrophobic drugs, it is necessary to know the character of a drug effect on the structure and physicochemical properties of a lipid bilayer. The aim of this work was to investigate the effect of lipid composition on membrane interactions of europium coordination complexes, V3 and V4, the potential antineoplastic drugs. Liposomes were formed by egg yolk phosphatidylcholine (PC) and its mixture with cardiolipin (CL) and cetyltrimethylammonium bromide (CTAB). The membrane-partitioning properties of the investigated drugs were

evaluated using the equilibrium dialysis technique in combination with absorption spectroscopy. To gain insight into the drug influence on physical parameters and molecular organization of lipid bilayer, two fluorescent probes have been employed, viz. pyrene and 1,6-diphenyl-1,3,5-hexatriene (DPH). It was found that inclusion of anionic lipid cardiolipin and cationic detergent CTAB into PC bilayer gives rise to decrease of the drugs partition coefficients. The drug incorporation into liposomal membrane is accompanied by the alterations of pyrene spectral parameters and DPH anisotropy. The observed effects suggest that the influence of europium compounds on bilayer structural state can be modulated by CL and CTAB.

A number of so-called conformational diseases including neurological disorders (Parkinson's, Alzheimer's and Huntington's diseases), type II diabetes, spongiform encephalopathies, systemic amyloidosis, etc., are associated with the deposition in tissue of highly ordered aggregates of specific proteins. Amyloid fibrils are usually detected by several techniques including Thioflavin T fluorescence, Congo Red (CR) birefringence of spectrophotometric assay, electron microscopy, etc. However, application of amyloid-specific agents such as CR to amyloid detection may be hampered by the dye ability to associate not only with fibrillar structures but also with monomeric protein species. In view of this reasoning the present study was directed toward the examination of the interactions between CR and hemoglobin (Hb), the protein with well-characterized structure and physicochemical properties. The binding of CR to native and denaturated Hb was studied using absorption spectroscopy technique. Differential absorption spectrum of CR associated with denaturated protein was found to exhibit maximum close to that characteristic of fibrillar structures (545 nm), thereby providing arguments in favor of Hb fibrillization. Formation of CR complexes with native Hb was followed by the long-wavelength shift (~ 10 nm) of absorption maxima being indicative of the probe transfer to the environment of lower polarity. Based on analysis of Hb crystal structure the tentative location of CR in the protein molecule has been identified. The most probable dye binding site was

assumed to involve the hydrophobic cavity between Lys16 and Lys60 serving as anchors for two negatively charged CR sulfonic groups. Quantitative parameters of CR complexation with native Hb - association constant (Kb) and number of binding sites (n) - were determined by analyzing the dependencies of dye absorbance changes upon varying protein concentration. Approximation of experimental dependencies by Langmuir binding model yielded the values of Kb and n ca. <$E 2,6~times~10 sup 5~roman M sup -1> and 1,4, respectively. For thermally denaturated Hb, the shape of CR binding curve was revealed to change from Langmuir-like to sigmoidal. Simulation results showed that such a behavior of binding curve is characteristic of preferential dye association with aggregated protein species.

Із використанням флуоресцентних зондів 4-(n-диметиаміностирил)-1-метилпіридинію (ДСМ) і 3-метоксибензантрону (МБА) досліджено вплив негативно зарядженого фосфоліпіду кардіоліпіну (КЛ) на структурний стан модельних мембран (ММ) з фосфатилихоліну. Проведена оцінка електростатичного та не електростатичного вкладів у стабілізацію комплексів ДСМ з ліпідами. Виявлено зміни в розподілі МБА у ліпідному бішарі у разі підвищення концентрації КЛ від 5 до 10 молярних %. Одержані дані свідчать про модифікуючий вплив КЛ на структурний стан ММ.