Soft perforation of cardiolipin-containing planar lipid bilayer membrane by cytochrome c and H(2)O(2).

The release of cytochrome c (cyt c) from mitochondria is responsible for initiation of cell apoptosis. Although extramitochondrial proteins are thought to initiate this release, the exact mechanism remains unclear. Cyt c binds to and penetrates lipid bilayer membranes of specific phospholipid cardiolipin (CL) contained in mitochondria. We present here the experimental results of monitoring planar BLM (pBLM) from mixtures of azolectin and of CL (4/1 by moles) by triangle voltage pulses of 100 mV in amplitude and frequency of 2 Hz. The BLM were modified by a successive addition of cyt c and of H(2)O(2) in water solution. It is shown that the addition of cyt c alone leads to a stepwise increase in the ionic conductance of the pBLM, indicating the appearance of transmembrane pores. Pore lifetimes then reached several seconds at an average pore diameter of ~2 nm. Current-voltage characteristics were then linear and passed through the origin which is characteristic for broad, nonselective ion pores. Subsequent addition of H(2)O(2) caused a dramatic increase in transmembrane current at retention of average pore size constant. Observed increase in membrane current is due to growth of a number of pores in an open state. We suggest that hydrogen peroxide in the presence of cyt c promotes a peroxidation of membrane phospholipids to form lysolipids, the embedding of which stabilizes the edge of the pore and the surface of lipid bilayer.

["Blocking" by polyethyleneglycol of single lipid pores arising in unmodified bilayer lipid membranes during phase transitions].

Changes in the ionic permeability of bilayer lipid membranes from dipalmitoyl phosphatidylcholine at temperatures of phase transition in LiCl (1 M) solution after the addition of polyethyleneglycols of different molecular masses have been studied. The transition of ionic membrane channels from the conducting state to a blocking nonconducting state using polymers makes it possible to calibrate lipid pores. It was shown that low-molecular-weight glycerol, polyethyleneglycols with molecular masses of 300 and 600 decrease the amplitude of fluctuations of the current through the membrane, the decrease being proportional to the size of the polymer molecule being incorporated. The addition of polyethyleneglycols with molecular masses of 1450, 2000, and 3350 decrease the current fluctuations to the basal noise level. This result is considered as a complete blockade of ion channel conductivity. In the presence of rather large polymers, such as polyethyleneglycols with molecular masses of 6000 and 20000, which are practically not incorporated into the pore, single current fluctuations occur again; however, their amplitudes are somewhat smaller than in the absence of polyethyleneglycol. It is assumed that the complete blockade of the conductivity of lipid ionic channels by polyethyleneglycols with molecular masses of 1450, 2000, and 3350 is due to the dehydration of the pore gap and the conversion of the hydrophilic pore to a hydrophobic pore.

[Use of fibrinocollagen complex in surgical treatment of patients with vascular tumors of the ear and external nose (a pilot report)].

A fibrinocollagen complex (TahoComb) has been used in surgical treatment of patients with vascular tumors of the ear and external nose (6 patients with hemangioma of the ear and 6 patients with hemangioma of the external nose). It is shown that TahoComb reduces significantly blood loss in removal of branchy arterial hemangiomas, need in ligation or embolization of afferent vessels, in tight tamponade of the tympanic cavity and external acoustic meatus.

[A soft poration of planar bilayer lipid membranes from dipalmitoylphosphatidylcholine at the temperature of the phase transition from the liquid crystalline to the gel state].

A method of soft poration of lipid bilayer was suggested, which is based on the structural rearrangement of lipid bilayer formed from disaturated phospholipids on the phase transition from liquid crystalline state to the gel. As opposed to the widely used method of electropbration, this method allows one to obtain a lipid pore population without application of high electric field. In the case of soft poration, the electric field does not exceed the physiological level of 10-100 mV. It was shown that, in planar bilayer lipid membranes formed from dipalmitoylphosphatidylcholine in water solution of 1 M LiCl, there appear up to 10 lipid pores in 1 min per 1 mm of membrane surface with an average conductivity of a pore of 31 +/- 13 nS. The average pore radius estimated using soluble polyethylene glycols ranged between 1.05-1.63 nm. Monovalent cation conductivity of a single lipid pore on soft poration was shown to decrease in the order Li+ > or = Na+ > K+ = Rb+ > or = Cs+. This order coincides with that observed by Marra and Israilashvili for dipalmitoylphosphatidylcholine-water interbilayer where the repulsive hydration force contribution is significant.

[Electric capacitance of bilayer lipid membranes from hydrogenated egg lecithin during phase transition from liquid crystalline state to gel]. / Elektricheskaia emkost' bisloinykh lipidnykh membran iz gidrirovannogo iaichnogo letsitina pri fazovom perekhode iz zhidkokristallicheskogo sostoianiia v gel'.

The electrical capacity of planar bilayer lipid membranes (BLM) from natural hydrogenated egg lecithin (HEL) in n-decane at a temperature of phase transition was measured. The temperature of phase transition was determined calorimetrically to be 51 degrees C. The data obtained revealed a phase separation of HEL in BLM into two fractions, one freezing at 42-44 degrees C and one that is converted to a liquid-crystal state at 51-59 degrees C. It was assumed that the first fraction is rich in dipalmitoyl lecithin, and the second fraction is rich in distearoyl lecithin. Freezing and the transition to the liquid-crystal state were accompanied by an increase and decrease in membrane thickness, respectively, in part due to a displacement of the solvent from the torus to the planar part of the bilayer. The displacement of the solvent is explained by changes in the disjoining pressure in BLM, which arises across the lipid bilayer due to van der Waals forces of attraction between water layers on both sides of the BLM.

[Polymyxin B and Ca(2+) induce conductance fluctuations in the dipalmitoyl phosphatidic acid bilayer lipid membrane]. / Polimiksin B i Ca(2+) indutsiruiut fluktuatsii provodimosti v bisloinoi lipidnoi membrane iz dipal'mitoilfosfatidnoi kisloty.

Polymyxin B in micromolar concentrations induces current fluctuations in liquid crystalline bilayer lipid membranes from dipalmitoylphosphatidic acid identified as ion channels. The appearance of ion channels correlates with phase separation of the lipid in the presence of peptide polycations detected by differential scanning calorimetry. Ca2+ also induces the formation of ion channels in liquid crystalline bilayer lipid membranes from dipalmitoylphosphatidic acid followed by the phase transition of the phospholipid. The capacitive current, which indicates the possibility of structural transformations of bilayer-non-bilayer type (hexagonal phase II), precedes the formation of Ca(2+)-induced channels in bilayer lipid membranes from dipalmitoylphosphatidic acid.

[Kinetics of resealing of lipid pores]. / Kinetika zatekaniia lipidnykh por.

The resealing of lipid pores in BLM at the temperature of phase transition was studied. It is show that the size of a pore correlates with the time of its resealing. The correlated coefficient of pore diffusion is close to that of lipid molecules in the gel state.

[Sub-atrophic and atrophic pharyngitis as a manifestation of dystrophic pharyngeal mucosa in presenile, senile and long living persons]. / Subatroficheskii i atroficheskii faringit kak proiavlenie distrofii slizistoi obolochki glotki u lits pozhilogo, starcheskogo vozrasta i u dolgozhitelei.

The authors consider diagnostic, clinical and symptom characteristics of atrophic pharyngitis (AP) in presenile, senile and long-living persons and conclude that AP is age-specific dystrophic lesion of the pharynx. Diagnosis formulation by three degrees are suggested: pharyngeal dystrophy (PD) of degree I (only local symptoms cured after timely treatment), PD of degree II (local symptoms + neurotic condition which manifests with cancerophobia, persistent sensation of a foreign body), PD of degree III (persistent cancerophobia demanding psychotherapeutic treatment or psychiatric care).

[Exponential distribution of interimpulse current intervals in lipid bilayer membrane at phase transition temperature]. / Eksponentsial'noe raspredelenie mezhimpul'snykh intervalov toka v bisloinykh lipidnykh membranakh pri temperature fazovogo perekhoda.

The statistical analysis of current fluctuations in unmodified bilayer lipid membranes at the phase transition temperature was made. An exponential distribution of current fluctuations was revealed.

[Lipid pores and life time of lipid bilayer membranes in gel and liquid crystal states]. / Lipidnye pory i vremena zhizni bisloinykh lipidnykh membran v gel'- i zhidkokristallicheskom sostoianiiakh.

The lifetime of lipid bilayer membranes formed from hydrogenated egg lecithin has been studied at the phase transition from liquid crystalline state to the gel. It was shown the lowering of the membrane stability at the phase transition temperature of hydrogenated egg lecithin. Using lifetime values and measured surface tension of bilayer the critical radius of transmembrane pore has been evaluated in comparison with experimental data, obtained by transmembrane current fluctuation registration. It was shown that lifetimes of bilayer lipid membrane in gel state conform data, derived from Deryagin-Gutop-Prokhorov's theory. The radii of pores corresponded to maximal transmembrane current fluctuations are close to critical values of pores in the gel state.

[Lipid pores and stability of cell membranes]. / Lipidnye pory i stabil'nost' kletochnykh membran.

Electric studies have ascertained that transmembrane pores appear during the gel-liquid crystalline transition phase in the bilayer lipid membrane. The longevity of the pore depends on the phase state of lipids: in gel, the pores demonstrate long-term fluctuations, which can be eliminated by heating. The molecular model of a lipid pore has been proposed. The model predicts the formation of pores whose appearance is energetically favourable. The size of a cooperative unit and the area per lipid molecule head have been shown to be responsible for membrane stability. Proceeding from the model, a hypothesis has been forwarded that phase transition may be induced in the lipid bilayer at physiological temperatures. Electric techniques and differential scanning calorimetry have established that bivalent ions of Ca2+, Cd2+, Mg2+, Sr2+, and Ba2+ are able to induce phase transition of bilayer membranes from acid lipids at physiological temperatures to give rise to through pores. An analysis of the experimental findings indicates that pores having a less critical radius themselves adhere with time.

[Formation of stabile cupola-like lipid bilayer membranes with a mobile plateau Gibbs boundary]. / Formirovanie stabil'nykh kupoloobraznykh bisloinykh lipidnykh membran s podvizhnoi granitsei plato-Gibbsa.

Stable bilayer lipid membrane with mobile Platear-Gibbs border have been formed. The predominant condition of the formation is the presence of lipid coverage on the teflon surface near the hole. The formation process includes transformation of the initial planar lipid bilayer into cupola-shaped one by bowing of the lipid bilayer due to hydrostatic pressure, movement of the PGb along the teflon surface. The bilayer area estimated by electric capacitance increases from 0.1 x 10(-8) F to 21 x 10(-8) F. Electric conductance of the lipid bilayer has not changed except for the phase transition and membrane collapse. The electric capacitance of the BLM formed from hydrogenated egg lecithin was changed by cooling between 60 degrees and 40 degrees C with the maximum at about phase transition range. The individual membrane sustains several scannings of the temperature without disruption which is an evidence of the stability of the cupola-shaped membranes.

Stable cupola-shaped bilayer lipid membranes with mobile Plateau-Gibbs border: expansion-shrinkage of membrane due to thermal transitions.

Stable bilayer lipid membranes (BLM) with mobile Plateau-Gibbs border (PGB) have been formed. The precondition of the formation was the presence of a lipid coverage on the teflon surface near the hole, where the membrane has been formed. This allowed the movement of the PGB along the teflon surface after transformation of the planar bilayer into a cupola-shaped by bowing of the bilayer due to excess hydrostatic pressure. As a result the giant bilayers were obtained with an area up to two orders larger in magnitude compared with the initial area. Changes in lipid bilayer area depend on the temperature at the phase transition of the lipid. Cooling of the expanded bilayer was followed by a significant shrinkage of the bilayer at temperatures below the main phase transition.

Electric field increases the phase transition temperature in the bilayer membrane of phosphatidic acid.

The effect of the electric field on the phase transition temperature (Tc) of acidic 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA) and 1,2-dipalmitoyl-sn-glycero-3-thionphosphate (thion-DPPA) and zwitterion, i.e. 1,2-dipalmitoyl-rac-3-phosphocholine and 1,2-distearoyl-rac-glycero-3-phosphocholine (DPPC and DSPC), lipids has been investigated. The phase transition was detected using the jump-like increase effect in the conductance of the planar bilayer membrane. A voltage increase to 150 mV has been shown to increase the phase transition temperature in a bilayer lipid membrane (BLM) of phosphatidic acids (DPPA and thion-DPPA) by 8-12 degrees C while the transition temperature in the bilayer of zwitterion lipids (DPPC and DSPC) increases insignificantly. The increasing of Tt in BLM of acidic lipids is attributed to the voltage-induced changes in the molecule packing density.

Permeability of bilayer lipid membranes in phase transition. The significance of intermolecular phosphate-phosphate hydrogen bonding.

The effect of pH on the phase transition temperature of 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA) and 1,2-dipalmitoyl-sn-glycero-3-thionphosphate (thion-DPPA) has been investigated. The phase transition was detected using the jump like increase effect in the conductance of the planar bilayer membrane. It is shown that the steepness of pH-dependence of the phase transition temperature differs for these two kinds of lipids in the pH range of 3.5-8. This result is explained in terms of decreased intermolecular hydrogen bonding between the head groups of thion-DPPA. Calculations taking into account the ability of DPPA molecules to intermolecular phosphate-phosphate hydrogen bonding were made. The results of calculations are in good agreement with the experimental data obtained in this study.

Capacitive and ionic currents in BLM from phosphatidic acid in Ca2+-induced phase transition.

The development of electric current with time in a bilayer lipid membrane (BLM) formed from dipalmitoylphosphatidic acid on introducing Ca2+ ions into the medium was studied at constant temperature and pH. The phase transition in the Ca2+-induced BLM is accompanied by the initial capacitive current followed by the occurrence of single ionic channels. The amount of transported charges in the capacitive current is 5 C/ microF. The conductivity of the single ionic channels ranges from 50 to 100 pSm.

[Ca2+ ions induce successive capacity and ion currents in BLM from phosphatidic acid as a result of phase transition]. / Iony Ca2+ indutsiruiut posledovatel'noe poiavlenie emkostnogo i ionnogo tokov v BLM iz fosfatidnoi kisloty v rezul'tate fazovogo perekhoda.

Time dependence of Ca2+-induced electric current in BLM formed from DPPA was studied at constant temperature and pH. The phase transition in BLM is accompanied by capacity current and following appearance of single ionic channels. It was shown that transferred charge was 5 nC/F, conductivity of single ionic channels--500-100 pSm.

[Evaluation of ion activity in determining time of death]. / Kompleksnaia otsenka aktivnosti ionov pri ustanovlenii davnosti nastupleniia smerti.

Activity of potassium ions was examined in 3 liquid media of 54 rabbit cadavers by potentiometry with the use of a potassium-selective valinomycin electrode. The reported and obtained data were used for the development of the diagnostic regression equations and the curves to define the time of death from the activity of a complex of 3 ions (potassium, sodium and hydrogen) in the blood serum, CSF and vitreous body fluid. The method is offered for appropriate trials in human cadavers.