3D trapping of microbubbles by the Marangoni force.

In this Letter, we show 3D steady-state trapping and manipulation of vapor bubbles in liquids employing a low-power continuous-wave laser using the Marangoni effect. Light absorption from photodeposited silver nanoparticles on the distal end of a multi-mode optical fiber is used to produce bubbles of different diameters. The thermal effects produced by either the nanoparticles on the fiber tip or the light bulk absorption modulate the surface tension of the bubble wall and creates both longitudinal and transversal forces just like optical forces, effectively creating a 3D potential well. Using numerical simulations, we obtain expressions for the temperature profiles and present analytical expressions for the Marangoni force. In addition, using an array of three fibers with photodeposited nanoparticles is used to demonstrate the transfer of bubbles from one fiber to another by sequentially switching on and off the lasers.

Stage-by-stage formation of superficial nanostructures in ITO films reduced by H2-GD at low temperature (100 °C) for applications on plastic substrates.

The formation of superficial nanostructures (SNs) in reduced indium tin oxide (ITO) thin films by H2-Glow discharge (GD) at a low reduction temperature (Tr = 100 °C) was investigated. Sputtered ITO films deposited at low (Td = 100 °C) and high (Td = 300 °C) temperatures were reduced using this low-temperature process. Scanning electron and atomic force microscopy were applied to study the evolution of the nanostructural features and three stages were identified: emerging/densification, coalescence, and depletion stages. The structural characteristics of the SNs were characterized by grazing incidence and conventional θ/2θ x-ray diffractions showing that at Tr = 100 °C, the reduction process was limited to the surface region in which the ion bombardment had influence. The mean diameter, , of the SNs in ITO deposited on the glass substrate was controlled from ∼10-90 nm and the SN densities, d, were obtained from ∼109-1011 SNs cm-2. Finally, the superficial nanostructures were successfully formed in ITO films deposited on flexible polyethylene naphthalate (PEN) substrates. It was demonstrated that, on these substrates, is possible to obtain a uniform distribution in the size and density of the SNs, with = 9.5-20.7 nm and d = 2.66 × 1011-4.20 × 1010 SNs cm-2.

Electro-optical processor for measuring displacement employing the Talbot and the nonsteady-state photo-electromotive force effects.

We present a device for measuring displacement based on the Talbot and the nonsteady photo-electromotive force effects. The proposed device does not require any numerical signal processing since its output signal is, in appropriate regions, linearly related to the measured displacement. The proposed system requires an illuminating field with a sinusoidal amplitude distribution and low fringe visibility. The dynamic range can be adjusted according to the illuminating field spatial period or wavelength. Displacements with an estimated resolution better than 10 µm in a dynamic range of 1.5 mm were detected using a sinusoidal amplitude grating with a period d=100 µm.

Non-steady-state photoelectromotive force effect under linear and periodical phase modulation: application to detection of Doppler frequency shift.

Non-steady-state photoelectromotive force effect in the presence of periodical and linear phase shift was investigated both theoretically and experimentally. It was shown that superposition of oscillating and linear movements of the interference pattern leads to the appearance of the sharp peak in the frequency dependence of the photoelectromotive force output current when the frequency of periodical modulation matches the frequency of the linear phase shift. We demonstrated experimentally that this effect can be used for determination of a Doppler frequency shift between signal and reference beam.

Thyroxine reversibly inhibits the uncoupling action of protonophores on energy production in rat thymus lymphocytes.

Earlier we reported that some thyroid and steroid hormones and also 6-ketocholestanol used in micromolar concentrations modulated the effects of protonophoric uncouplers on isolated mitochondria (Starkov et al. (1997) Biochim. Biophys. Acta, 1318, 173-183). In the present study we investigated the effects of a thyroid hormone, thyroxine, on energy coupling of intact rat thymus lymphocytes and mitochondria isolated from these cells. The resting (oligomycin-inhibited) respiration of the isolated intact lymphocytes was stimulated by the addition of protonophoric uncouplers 2,4-DNP, FCCP, or SF6847. Subsequent addition of micromolar concentrations of thyroxin decreased the rate of uncoupler-stimulated respiration and partially reversed uncoupler-induced decrease of membrane potential (DeltaPsi). In experiments with mitochondria isolated from thymus lymphocytes the re-coupling effect of thyroxine was not observed. In this case thyroxine did not influence mitochondrial respiration stimulated with 2,4-DNP, but did potentiate the stimulation of respiration and DeltaPsi decrease induced with another uncoupler, SF6847. The data are discussed in terms of a hypothesis that aromatic uncouplers are transported into the cell by the thyroxine carrier of the plasma membrane.

6-Ketocholestanol is a recoupler for mitochondria, chromatophores and cytochrome oxidase proteoliposomes.

The effect of 6-ketocholestanol (kCh) on various natural and reconstituted membrane systems has been studied. 6-ketocholestanol (5 alpha-Cholestan-3 beta-ol-6-one), a compound increasing the membrane dipole potential, completely prevents or reverses the uncoupling action of low concentrations of the most potent artificial protonophore SF6847. This effect can be shown in the rat liver and heart muscle mitochondria, in the intact lymphocytes, in the Rhodobacter sphaeroides chromatophores, and in proteoliposomes with the heart muscle or Rh. sphaeroides cytochrome oxidase. The recoupling effect of kCh disappears within a few minutes after the kCh addition and cannot be observed at all at high SF6847 concentrations. Almost complete recoupling is also shown with FCCP, CCCP, CCP and platanetin. With 2,4-dinitrophenol, fatty acids and gramicidin, kCh is ineffective. With TTFB, PCP, dicoumarol, and zearalenone, low kCh concentrations are ineffective, whereas its high concentrations recouple but partially. The kCh recoupling is more pronounced in mitochondria, lymphocytes and proteoliposomes than in chromatophores. On the other hand, mitochondria, lymphocytes and proteoliposomes are much more sensitive to SF6847 than chromatophores. A measurable lowering of the electric resistance of a planar bilayer phospholipid membrane (BLM) are shown to occur at SF6847 concentrations which are even higher than in chromatophores. In BLMs, kCh not only fails to reverse the effect of SF6847, but even enhances the conductivity increase caused by this uncoupler. It is assumed that action of low concentrations of the SF6847-like uncouplers on coupling membranes involves cytochrome oxidase and perhaps some other membrane protein(s) as well. This involvement is inhibited by the asymmetric increase in the membrane dipole potential, caused by incorporation of kCh to the outer leaflet of the membrane.

Regulation of the energy coupling in mitochondria by some steroid and thyroid hormones.

Male sex hormones [dihydrotestosterone (DTS), and testosterone] and progesterone, when added to the isolated rat liver mitochondria before or after some protonophores, lower the respiration rate and increase the delta psi level, i.e., reverse the protonophore-induced uncoupling. Such a recoupling ability shows specific structural requirements correlating with hormonal activity of steroids studied. For instance, epiandrosterone, a DTS isomer of very low hormonal activity, and deoxycorticosterone, differing from progesterone by additional OH-group and possessing quite different hormonal activity, as well as female sex hormones (estron and estradiol) show no recoupling effect. Like 6-ketocholestanol (kCh), male sex hormones and progesterone recouple mitochondria uncoupled by low concentrations of SF6847, FCCP and CCCP, but not by high concentration of these uncouplers or by any concentration of DNP, palmitate and gramicidin. In contrast to recoupling by kCh, hormonal recoupling requires addition of serum albumin and is inhibited by low concentrations of palmitate. Recoupling can also be shown on the heart and skeletal muscle mitochondria, being absent from the heart muscle submitochondrial particles, the bacterial chromatophores and the cytochrome oxidase proteoliposomes. In mitochondria it does not depend upon the oxidation substrate used (succinate or PMS + ascorbate were tested). Pronounced seasonal effect upon the DTS recoupling degree was revealed. The recoupling is maximal in January, February and from June to November, being minimal in the spring months and in December. In spring, the in vivo administration of thyroxine, di- or triiodothyronine improves the recoupling ability of DTS. 2 x 10 - 6 M. Thyroxine, when added in vitro, does not affect energy coupling if SF6847 was absent. In the presence of small amounts of SF6847, thyroxine stimulates the uncoupling in a DTS-sensitive fashion, di- and triiodothyronines being less effective. Addition of thyroxine to azide-inhibited mitochondria (oligomycin is present) stimulates respiration and normalizes the delta psi level. In this system, triiodothyronine is much less effective, whereas diiodothyronine is not effective at all. In the intact cells (thymocytes and the Krebs-II cells were tested), DTS lowers the respiration rate stimulated by low concentrations of SF6846 or FCCP. In this case, serum albumin is not required. It is suggested that recoupling effects of male sex hormones and progesterone are involved in their anabolic action just as uncoupling takes part in the catabolic activity of thyroid hormones.

[Mitochondrial proteolipids]. / Proteolipidy mitokhondrii.

A convenient procedure is proposed for extracting mitochondrial proteolipids using a single phase mixture chloroform-methanol-water (1:2:0.8 v/v) with subsequent separation of the phases. The proteolipids were concentrated at the interface between the phases and thus purified from the bulk of the phospholipids. It was found that the mitochondrial proteolipids represent stable complexes of phospholipids with some low molecular weight proteins (M(r) = 7-18 kDa). The latter are destroyed at acid pH values. The phospholipid/protein ratio was found to be equal to 6 (assuming the molecular masses of the proteins and phospholipids to be equal to 10 and 0.8 kDa, respectively). The phospholipid composition of the tightly bound proteolipids thus obtained did not differ from that of the mitochondrial phospholipids. Using 31P-NMR, nonbilayer structures were found to arise from proteolipid reconstitution into multibilayer liposomes.

A simple colorimetric assay method for pyrophosphate in the presence of a 1000-fold excess of orthophosphate: application of the method to the study of pyrophosphate metabolism in mitochondria.

A sensitive colorimetric method for the assay of inorganic pyrophosphate with excess of orthophosphate is described. The principle of this method lies in the formation of phosphomolybdate and PPi-molybdate complexes with subsequent extraction of the phosphomolybdate complex by organic solvents and reduction of the PPi-molybdate complex by dithiothreitol and Eikonogen. The sensitivity of the method was from 5 to 120 nmol of PPi in a 2.0-ml sample.

The effect of phospholipids on the activity of mitochondrial pyrophosphatases. Lipidized soluble mitochondrial pyrophosphatase: the coupling factor for oxidation and phosphorylation.

The effect of temperature on the hydrolase activity of mitochondrial pyrophosphatases, i.e. soluble (PPase I) and membrane (PPase II), has been studied. In contrast to the soluble species, the membrane form has inflexions in the Arrhenius curves. However, after lipidization of PPase I by various phospholipids, the curves also acquire inflexion points, which prove similar or identical with the phase separation points of the lipids used. The closeness of the inflexion points of PPase II, containing phosphatidylcholine, and PPase I lipidized by mitochondria phosphatidylcholine, to the phase separation points of this lipid indicates that the inflexions on the PPase II curves should be ascribed to this phospholipid. It has been shown that the hydrolysis of PPi by SMP is affected by the cooperative rearrangements of the entire lipid component of the membrane rather than by the change of the phase state of PPase II phosphatidylcholine. Reconstitution experiments on the PPi synthesis system have shown that after lipidization PPase I is able to incorporate into SMP and become a coupling factor for respiration and PPi synthesis, like PPase II.

[The role of lipids in the regulation of ATP and PPi synthesis in mitochondria]. / Rol' lipidov v reguliatsii sinteza ATP i PPi v mitokhondriiakh.

It was demonstrated previously that mitochondria of higher and lower eukaryotes can synthesize, in the course of oxidative phosphorylation, not only ATP but also inorganic pyrophosphate (PPi). Two PPases were isolated from bovine heart mitochondria (soluble--PPase I and membrane--PPase II). Coupling PPase II, in contrast to PPase I, contains phosphatidyl choline, but PPase I is lipidized readily in the presence of different phospholipids. Reconstitution experiments of the PPi synthesis system have shown that after lipidization PPase I is able to incorporate into submitochondrial particles (SMP) and becomes a coupling factor for oxidation and PPi synthesis. It seems that phospholipid is indispensible for incorporation into the membrane and the manifestation of the coupling activity of the enzyme. The effect of lipids on the activity of soluble and membrane-bound pyrophosphatase was studied. It is shown that PPase II phospholipid is involved in the regulation of the hydrolase activity of the isolated enzyme. However, hydrolysis of PPi by SMP and its synthesis by mitochondria are affected by cooperative rearrangements of the entire lipid component of the membrane rather than by changes in the phase state of phosphatidyl choline contained in PPase II. An opposite response of ATP and PPi synthesis to changes in viscosity makes it likely that the viscosity of the mitochondrial inner membrane may control the levelling of these two processes in mitochondria.

[Effects of lipids on the activity of soluble mitochondrial pyrophosphatase and its conversion to the membrane-bound form]. / Vliianie lipidov na akativnost' rastvorimoi pirofosfatazy mitokhondrii i ee prevrashchenie v membrannosviazannuiu formu.

The effects of lipids on the activity of soluble and membrane-bound pyrophosphatase from beef heart mitochondria were studied. An addition of total mitochondrial lipid, phosphatidyl choline, phosphatidyl ethanolamine or cardiolipin resulted in stimulation of the enzymatic activity and an increase in thermal stability of the soluble enzyme. The maximal activating effect was exerted by the total mitochondrial lipid and phosphatidyl choline. The electrophoretic data suggest that phosphatidyl choline is a component of membrane pyrophosphatase. Preincubation of the soluble enzyme with phosphatidyl choline converted the enzyme into a membrane form, which is capable to carry out the energy-dependent synthesis of PPi in submitochondrial particles.

Accumulation of pyrophosphate and other energy-rich phosphorous compounds under various conditions of yeast growth.

In the cells of hybrid yeast strain Saccharomyces N.C.Y.C. 644 SU3 (Karlsberg collection), a large amount of pyrophosphate (30-300 micro mol per g of dry weight) accumulates whatever the aeration conditions and the contest of glucose in the medium. The content of pyrophosphate is 10-100 times higher than that of ATP. At the early and mid-exponential growth phases two maxima of pyrophosphate accumulation are observable. The periods of maximal pyrophosphate accumulation in yeast coincide with those of the minimal contest of polymeric acid-soluble polyphosphates and intense budding. In the light of the data obtained, the question is discussed as to the relationship between the metabolism of pyrophosphates and acid-soluble polyphosphates in yeats.

[Inhibitory analysis as an approach to investigation of regulation of ATP and pyrophosphate biosynthesis in mitochondria]. / Ingibitornyi analiz kak podkhod k izucheniiu reguliatsii biosinteza ATP i pirofosfata v mitokhondriiakh.

The effect of respiration rate on the content and accumulation of ATP and PPi in rat liver mitochondria was studied. It was found that the syntheses of ATP and PPi occur at different respiration rates. It was assumed that the respiration rate can determined the formation of ATP or PPi via oxidative phosphorylation. A possible mechanism of this effect is discussed.