Increase In Osmotic Pressure Research Articles

Ion transport characteristics in nanofiltration membranes: measurements and mechanisms

Research Article| March 01 2010 Ion transport characteristics in nanofiltration membranes: measurements and mechanisms Noeon Park; Noeon Park 1R&D Budget Coordination Division, Korea Institute of Science and Technology Evaluation and Planning (KISTEP), 11F Dongwon Industry Bldg, 275, Yangjae-dong, Seocho-gu, Seoul 137-130, South Korea Search for other works by this author on: This Site PubMed Google Scholar Jaeweon Cho; Jaeweon Cho 2Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea Search for other works by this author on: This Site PubMed Google Scholar Seungkwan Hong; Seungkwan Hong 3Department of Civil, Environmental & Architectural Engineering, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-713, South Korea Search for other works by this author on: This Site PubMed Google Scholar Sangyoup Lee Sangyoup Lee 3Department of Civil, Environmental & Architectural Engineering, Korea University, 1, 5-ka, Anam-dong, Sungbuk-gu, Seoul 136-713, South Korea Tel.: +82-2-3290-3731 ; Fax: +82-2-928-7656; E-mail: sangyoup_lee@korea.ac.kr Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2010) 59 (2-3): 179–190. https://doi.org/10.2166/aqua.2010.034 Article history Received: April 30 2009 Accepted: November 13 2009 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Noeon Park, Jaeweon Cho, Seungkwan Hong, Sangyoup Lee; Ion transport characteristics in nanofiltration membranes: measurements and mechanisms. Journal of Water Supply: Research and Technology-Aqua 1 March 2010; 59 (2-3): 179–190. doi: https://doi.org/10.2166/aqua.2010.034 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Ion transport characteristics during nanofiltration (NF) were investigated by measuring effective osmotic pressure and diffusivity experimentally. Effective osmotic pressure and diffusivity were measured through lab-scale transport and diffusion tests. First, it was shown that the water flux across NF membranes decreased dramatically with increasing ionic strength because of the noticeable increase in effective osmotic pressure. Second, the results from transport experiments showed that the ion selectivity values, which were derived from the thermodynamic model, decreased with increasing ionic strength. Third, by analysing the data of measured osmotic pressure and diffusivity, it was demonstrated that the former and the latter increased and decreased, respectively, as ionic strength increased. The experimentally determined osmotic pressure across NF membranes was much lower than that calculated theoretically. At best, around 5% or less of the theoretical osmotic pressure was obtained under the experimental conditions investigated. The effective osmotic pressure and ion rejection decreased in the presence of nano-colloids. The influence of nano-colloids on ionic transport was found to be dependent on the concentration and size of the nano-colloids. Therefore, ion transport characteristics across NF membranes can be determined practically by measuring effective osmotic pressure and diffusivity as these reflect both feed water and membrane properties. effective diffusivity, effective osmotic pressure, ion transport characteristics, nano-colloids, nanofiltration This content is only available as a PDF. © IWA Publishing 2010 You do not currently have access to this content.

In vitro storage of some pear genotypes with the minimal growth technique

Shoot cultures of 9 pear genotypes collected from different areas of Azad Jammu and Kashmir (northern Pakistan) were maintained on MS medium supplemented with 30 g L^{-1} of sucrose + 7 g L^{-1} of agar + 1 mg L^{-1} of BAP. For in vitro preservation shoot tips were excised from these cultures and transferred onto different media, i.e. full strength, ¼ strength, ½ strength MS medium, and full strength MS medium containing 2.5% or 3.5% (w/v) mannitol. The cultures were assessed for their survival after storage periods of 3, 6, 9, and 12 months. To test the regenerability of the cultures they were transferred onto fresh culture medium. The genotypes differed significantly in their survival; however, they were statistically similar in terms of regenerability when transferred onto fresh medium. Shoots of the Khurolli and Bagugosha genotypes remained quite healthy, with relatively high survival rates (53.25% and 50.50%, respectively), whereas those of the Desi nakh genotype had the lowest survival rate (41.02%). Full strength MS medium containing 2.5% (w/v) mannitol gave the highest survival and regenerability rates (55.82% and 52.31%, respectively) in cultured shoots. Preservation for the shortest period (3 months) resulted in the highest survival (63.41%) and regeneration (58.81%). Genotypes and storage period interaction showed maximum shoot survival in Kashmiri nakh stored for 3 months, while Raj btung cultures stored for 12 months responded poorly, with the minimum survival rate. Addition of mannitol at the lower concentration of 2.5% (w/v) was an effective technique to lengthen subculture duration, possibly because of a gradual increase in osmotic pressure in the medium, which resulted in reduced availability of water to the growing cultures.

Separation and Concentration of Lactate from Cassava Fermentation Broth by Reverse Osmosis

A reverse osmosis experiment was performed to separate and concentrate lactate from cassava fermentation broth. Pure lactic acid and ammonium lactate solutions were also used as model solutions. The influence of operating con- ditions, including feed velocity, transmembrane pressure and feed concentration, on the filtration properties (perme- ate flux, rejection and osmotic pressure) were studied. The concentration factor of lactic acid during batch operation of reverse osmosis was also evaluated. In the laminar flow regime, permeate flux increased with increasing of feed velocity due to concentration polarization of the solute on the membrane surface. However, the permeate flux was not affected by feed velocity in the turbulent regime. Permeate flux and rejection increased with transmembrane pressure and decreased with feed concentration due to higher osmotic pressure. At a transmembrane pressure of 5.5 MPa and an initial feed velocity of 0.7 m/s, lactic acid in the model solutions could be concentrated from three to six times; however, the concentration factor in fermentation broth only reached two. The degree of concentration increase of lactic acid was affected by the presence of medium and residual sugar in the fermentation broth, as both may contribute to the increase of osmotic pressure and also polarize the concentration effect that occurs on the mem- brane surface.

Osmotic pressure and substrate resistance during the concentration of manure nutrients by reverse osmosis membranes

The objective of the membrane technology presented here is the production of nitrogen concentrates from pretreated swine manure. This paper reports on the effect of osmotic pressure and substrate resistance on transmembrane flux during the concentration of prefiltered swine (PFS) manure by reverse osmosis (RO) membranes. The PFS manure at various concentration levels was filtered by four highly selective polyamide RO membranes with maximum allowable pressures ranging from 41 to 83 bar. The osmotic pressure created by the PFS manure on the RO membranes fitted a second-order equation with respect to manure conductivity or total ammonia-nitrogen (TAN), indicating that the rate of increase in osmotic pressure accelerated as manure was being concentrated. Average osmotic pressure increased by a factor of 6.8, from 5.4 to 36.6 bar, as TAN was increased 5.6 times, from 1.6 g to 9.2 g/l. Substrate-related resistance, which has been attributed to specific membrane–solute interactions even in the absence of flow, tended to increase as PFS manure concentration increased. However, reduction in transmembrane flux during manure concentration was mainly due to increase in osmotic pressure. If the objective of the technology is to concentrate manure in small volumes with high nitrogen concentrations, RO systems have to be equipped with membranes that are able to sustain high applied pressures, because the decrease in flow due to increased osmotic pressure along membrane elements will be substantial.

Vesicle formation in the membrane of onion cells (Allium cepa) during rapid osmotic dehydration

Optimization of osmotic dehydration in different plant cells has been investigated through the variation of parameters such as the nature of the sugar used, the concentration of osmotic solutions and the processing time. In micro-organisms such as the yeast, Saccharomyces cerevisiae, the exposure of a cell to a slow increase in osmotic pressure preserves cell viability after rehydration, while sudden dehydration involves a lower rate of cell viability, which could be due to membrane vesiculation. The aim of this work is to study cytoplasmic vesicle formation in onion epidermal cells (Allium cepa) as a function of the kinetics of osmotic pressure variation in the external medium. Onion epidermal cells were submitted either to an osmotic shock or to a progressive osmotic shift from an osmotic pressure of 2 to 24 MPa to induce plasmolysis. After 30 min in the treatment solution, deplasmolysis was carried out. Cells were observed by microscopy during the whole cycle of dehydration-rehydration. The application of an osmotic shock to onion cells, from an initial osmotic pressure of 2 MPa to a final one of 24 MPa for <1 s, led to the formation of numerous exocytotic and osmocytic vesicles visualized through light and confocal microscopy. In contrast, after application of a progressive osmotic shift, from an initial osmotic pressure of 2 MPa to a final one of 24 MPa for 30 min, no vesicles were observed. Additionally, the absence of Hechtian strand connections led to the bursting of vesicles in the case of the osmotic shock. It is concluded that the kinetics of osmotic dehydration strongly influence vesicle formation in onion cells, and that Hechtian strand connections between protoplasts and exocytotic vesicles are a prerequisite for successful deplasmolysis. These results suggest that a decrease in the area-to-volume ratio of a cell could cause cell death following an osmotic shock.

Determination of subcellular concentrations of soluble carbohydrates in rose petals during opening by nonaqueous fractionation method combined with infiltration–centrifugation method

Petal growth associated with flower opening depends on cell expansion. To understand the role of soluble carbohydrates in petal cell expansion during flower opening, changes in soluble carbohydrate concentrations in vacuole, cytoplasm and apoplast of petal cells during flower opening in rose (Rosa hybrida L.) were investigated. We determined the subcellular distribution of soluble carbohydrates by combining nonaqueous fractionation method and infiltration-centrifugation method. During petal growth, fructose and glucose rapidly accumulated in the vacuole, reaching a maximum when petals almost reflected. Transmission electron microscopy showed that the volume of vacuole and air space drastically increased with petal growth. Carbohydrate concentration was calculated for each compartment of the petal cells and in petals that almost reflected, glucose and fructose concentrations increased to higher than 100 mM in the vacuole. Osmotic pressure increased in apoplast and symplast during flower opening, and this increase was mainly attributed to increases in fructose and glucose concentrations. No large difference in osmotic pressure due to soluble carbohydrates was observed between the apoplast and symplast before flower opening, but total osmotic pressure was much higher in the symplast than in the apoplast, a difference that was partially attributed to inorganic ions. An increase in osmotic pressure due to the continued accumulation of glucose and fructose in the symplast may facilitate water influx into cells, contributing to cell expansion associated with flower opening under conditions where osmotic pressure is higher in the symplast than in the apoplast.

Integration of H2-Based Membrane Biofilm Reactor with RO and NF Membranes for Removal of Chromate and Selenate

A new hybrid process has been proposed and evaluated the feasibility for complete removal of chromate and selenate at high level. The process consists of a H2-based membrane biofilm reactor (MBfR) and reverse osmosis (RO)/nanofiltration (NF) stages. The essential feature of the process is the recycling of the RO and NF concentrate into the membrane biofilm reactor. First, two different H2-based denitrifying MBfR initially reduced selenate (Se (VI)) or chromate (Cr (III)) stably to Se° or Cr (III) to limited levels (approximately 70–85% removal for selenate and approximately 40–65% removal for chromate). In order to achieve more stable and lower levels, two different membrane (NF and RO) filtration technologies as sequential process were combined. Two wastewaters produced from two MBfRs having similar amounts of target toxic ions (C o = 366 μg-Cr L−1 and C o = 326 μg-Se L−1), pH, and conductivity were tested to determine the solute rejection and the membrane flux for one RO and one NF membranes at varying recovery conditions (10–90%). The results show that the rejection of solutes decreases with increasing the recovery due to the increase in osmotic pressure. The rejections by the RO membrane were >99–98% for chromate and 99–94% for selenate, while slightly lower rejections (<20%) were observed for the NF membrane at the recovery conditions.

Neurotransmitter regulation of c- fos and vasopressin gene expression in the rat supraoptic nucleus

Acute increases in plasma osmotic pressure produced by intraperitoneal injection of hypertonic NaCl are sensed by osmoreceptors in the brain, which excite the magnocellular neurons (MCNs) in the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) in the hypothalamus inducing the secretion of vasopressin (VP) into the general circulation. Such systemic osmotic stimulation also causes rapid and transient increases in the gene expression of c- fos and VP in the MCNs. In this study we evaluated potential signals that might be responsible for initiating these gene expression changes during acute hyperosmotic stimulation. We use an in vivo paradigm in which we stereotaxically deliver putative agonists and antagonists over the SON unilaterally, and use the contralateral SON in the same rat, exposed only to vehicle solutions, as the control SON. Quantitative real time-PCR was used to compare the levels of c- fos mRNA, and VP mRNA and VP heteronuclear (hn)RNA in the SON. We found that the ionotropic glutamate agonists (NMDA plus AMPA) caused an approximately 6-fold increase of c- fos gene expression in the SON, and some, but not all, G-coupled protein receptor agonists (e.g., phenylephrine, senktide, a NK-3-receptor agonist, and α-MSH) increased the c- fos gene expression in the SON from between 1.5 to 2-fold of the control SONs. However, none of these agonists were effective in increasing VP hnRNA as is seen with acute salt-loading. This indicates that the stimulus-transcription coupling mechanisms that underlie the c- fos and VP transcription increases during acute osmotic stimulation differ significantly from one another.

Alkalinity and high total solids affecting H2 production from organic solid waste by anaerobic consortia

Abstract The optimization of total solids in the feed (%TS) and alkalinity ratio ( γ ) for H 2 production from organic solid wastes under thermophilic regime was carried out using response surface methodology based on a central composite design. The total solids levels were 20.9, 23.0, 28.0, 33.0 and 35.1% whereas the levels of alkalinity ratio (defined as g phosphate alkalinity/g dry substrate) were 0.15, 0.20, 0.30, 0.41 and 0.45. High levels of TS and γ affected in a negative way the H 2 productivity and yield; both response variables significantly increased upon decreasing the TS content and alkalinity ratio. The highest H 2 productivity and yield were 463.7 N mL/kg-d and 54.8 N mL/g VS rem , respectively, predicted at 20.9% TS and alkalinity ratio 0.25 (0.11 g CaCO 3 /g dry substrate). The alkalinity requirements for hydrogenogenic processes were lower than those reported for methanogenic processes (0.11 vs. 0.30 g CaCO 3 /g COD). Adequate alkalinity ratio was necessary to maintain optimal biological activity for hydrogen production; however, excessive alkalinity negatively affected process performance probably due to an increase of osmotic pressure. Interestingly, reactor pH depended only on the alkalinity ratio, thus the buffer capacity was able to maintain a constant pH independently of TS levels. At γ = 0.15–0.30 the pHs were in the range 5.56–5.95, which corresponded to the highest hydrogen productivities and yields. Finally, the highest metabolite accumulation corresponded with the highest removal efficiencies but not with high H 2 productivities and yields. Therefore, it seems that organic matter removal was channeled toward solvent generation instead of hydrogen production at high TS and γ levels. This is the first study that shows the requirements of alkalinity in solid substrate fermentation conditions for H 2 production processes and their interaction with the content of total solids in the feed.

Synapse‐to‐synapse variation in mean synaptic vesicle size and its relationship with synaptic morphology and function

Synaptic vesicle (SV) size is one parameter that controls the amount of neurotransmitter released from individual SVs and, therefore, is fundamental to our understanding of synaptic function. The recently discovered variability of mean SV size among excitatory hippocampal synapses -- if actively regulated -- is a potential mechanism for the regulation of transmitter release. Here, we investigated which parameters influence mean SV size. First, we revealed that synapse-to-synapse variability of SV size is a general phenomenon in several species and brain regions. In addition, we determined the relationship between mean SV size and synaptic morphology. In three-dimensional reconstructions from serial ultrathin sections, we found that SV size did not correlate with the area of the postsynaptic density (a measure for synaptic size and synaptic cleft volume) nor with the total number of SVs within a bouton or bouton volume. We tested the long-held hypothesis that a change in osmotic pressure (potentially caused by a change in neurotransmitter concentration) affects SV size. When we reduced the osmotic pressure, SVs became significantly smaller; however, an increase in osmotic pressure had no effect on SV size. Furthermore, we found that SV size does not adapt to chronic changes in activity and that the SV cycle is capable of providing constant SV size during long-lasting, high-frequency stimulation.

Outward‐rectifying K+ channel activities regulate cell elongation and cell division of tobacco BY‐2 cells

Potassium ions (K+) are required for plant growth and development, including cell division and cell elongation/expansion, which are mediated by the K+ transport system. In this study, we investigated the role of K+ in cell division using tobacco BY-2 protoplast cultures. Gene expression analysis revealed induction of the Shaker-like outward K+ channel gene, NTORK1, under cell-division conditions, whereas the inward K+ channel genes NKT1 and NtKC1 were induced under both cell-elongation and cell-division conditions. Repression of NTORK1 gene expression by expression of its antisense construct repressed cell division but accelerated cell elongation even under conditions promoting cell division. A decrease in the K+ content of cells and cellular osmotic pressure in dividing cells suggested that an increase in cell osmotic pressure by K+ uptake is not required for cell division. In contrast, K+ depletion, which reduced cell-division activity, decreased cytoplasmic pH as monitored using a fluorescent pH indicator, SNARF-1. Application of K+ or the cytoplasmic alkalizing reagent (NH(4))(2)SO(4) increased cytoplasmic pH and suppressed the reduction in cell-division activity. These results suggest that the K+ taken up into cells is used to regulate cytoplasmic pH during cell division.

Release of cationic polymer-DNA complexes from the endosome: A theoretical investigation of the proton sponge hypothesis

Polyplexes are complexes composed of DNA and cationic polymers; they are promising transport vehicles for nonviral gene delivery. Cationic polymers that contain protonatable groups, such as polyethylenimine, have been suggested to trigger endosomal escape of polyplexes according to the "proton sponge hypothesis." Here, osmotic swelling is induced by a decrease in the endosomal pH value, leading to an accumulation of polymer charge accompanied by the influx of Cl(-) ions to maintain overall electroneutrality. We study a theoretical model of the proton sponge mechanism. The model is based on the familiar Poisson-Boltzmann approach, modified so as to account for the presence of ionizable polyelectrolytes within self-consistent field theory with assumed ground state dominance. We consider polyplexes, composed of fixed amounts of DNA and cationic polymer, to coexist with uncomplexed cationic polymer in an enclosing vesicle of fixed volume. For such a system, we calculate the increase in osmotic pressure upon moderately decreasing the pH value and relate that pressure to the rupture tension of the enclosing membrane. Our model predicts membrane rupture upon pH decrease only within a certain range of free polymer content in the vesicle. That range narrows with increasing amount of DNA. Consequently, there exists a maximal amount of DNA that can be incorporated into a vesicle while maintaining the ability of content release through the proton sponge mechanism.

Changes in Ca, Fe, Mg, Mo, Na, and S content in a Mediterranean shrubland under warming and drought

In an evergreen Mediterranean shrubland we conducted a 6‐year field experiment simulating the warming and drought projected by general circulation models and ecophysiological models for the next decades: 20% reduction of soil moisture and 1°C of temperature increase. We tested whether warming and drought have effects on Ca, Fe, Mg, Mo, Na and S availability, concentrations and accumulation patterns in the three dominant plant species and in soil. Warming increased concentrations of Ca and Mo in leaves in Erica multiflora (42% and 65%, respectively) and in Dorycnium pentaphyllum (38% and 60%, respectively). Warming increased Mo accumulation in leaves and aboveground biomass in Globularia alypum (0.07 and 0.40 g ha−1) and in E. multiflora (0.12 and 0.4 g ha−1), and increased Fe accumulation in stem biomass of G. alypum (600 g ha−1), increasing the capacity to retain these nutrients in the ecosystem. The increase of Fe and Mo capture capacity under warming conditions was greater in G. alypum than in E. multiflora coinciding with its greater increases in photosynthetic capacity. Warming decreased soil total‐Fe concentration by 24% and increased Mg accumulation in soil exchange complex by 19%. Drought increased Na leaf and stem concentrations (93% and 50%, respectively) and accumulation in leaf and aboveground biomass (780 and 800 g ha−1, respectively) in G. alypum, allowing an increase of osmotic pressure which helps to prevent water losses and is related to its capacity to resist drought. Drought reduced S leaf and Mg leaf‐litter concentrations of G. alypum and increased them in leaves of E. multiflora and also increased Mo and Na concentrations in leaves of D. pentaphyllum. Drought increased Fe soil solubility by 65%. The results indicate different effects of climate change on nutrient status in the ecosystem depending on whether the main change is warming or drought. The changes in concentration and biomass accumulation were different depending on the nutrient and the species, changing the stoichiometry among these nutrients and modifying the nutritional quality of plant tissues.

Fission of membrane nanotube induced by osmotic pressure

The final stage of endocytosis is fission of a thin membrane neck, or nanotube (NT), connecting cell membrane with a forming vesicle. We studied this process using a model system consisting of NT pulled out from a flat bilayer lipid membrane. Fission of NT was induced by an increase of osmotic pressure created by local application of a concentrated salt solution in the vicinity of NT. Superfusion of NT with distilled water instead of the concentrated salt solution led to the NT expansion. This observation demonstrates the reversibility of the NT expansion-compression process under the osmotic pressure. The overall picture of fission is similar to that described earlier for the NT fission with participation of dynamin GTPase. In both cases, in order for fission to occur, it is necessary to compress the NT to a critical radius. The critical radius estimated for the osmotic pressure-induced fission exceeds the value obtained for the fission occurring in the presence of the protein. Fission under osmotic pressure, akin the dynamin-promoted fission, proceeds without leaky defects.

Prolonged gene silencing in hepatoma cells and primary hepatocytes after small interfering RNA delivery with biodegradable poly(β‐amino esters)

Small interfering (si)RNA mediated inhibition of oncogenes or viral genes may offer great opportunities for the treatment of several diseases such as hepatocellular carcinoma and viral hepatitis. However, the development of siRNAs as therapeutic agents strongly depends on the availability of safe and effective intracellular delivery systems. Poly(beta-amino esters) (PbAEs) are, in contrast to many other cationic polymers evaluated in siRNA delivery, biodegradable into smaller, nontoxic molecules. We show for the first time that PbAE : siRNA complexes, containing 1,4-butanediol (PbAE1) or 1,6-hexanediol (PbAE2) diacrylate-based polymers, induced efficient gene silencing in both hepatoma cells and primary hepatocytes without causing significant cytotoxicity. Furthermore, carriers that slowly release the siRNA into the cytoplasm and hence induce a prolonged gene silencing are of major clinical interest, especially in fast dividing tumour cells. Therefore, we also studied the duration of gene silencing in the hepatoma cells and found that it was maintained for at least 5 days after siRNA delivery with PbAE2, the polymer with the slowest degradation kinetics. From the time-dependent cellular distribution of these PbAE : siRNA complexes, we suggest that the slowly degrading PbAE2 causes a sustained endosomal release of siRNA during a much longer period than PbAE1. This may support the hypothesis that the endosomal release mechanism of PbAE : siRNA complexes is based on an increase of osmotic pressure in the endosomal vesicles after polymer hydrolysis. In conclusion, our results show that both PbAEs, and especially PbAE2, open up new perspectives for the development of efficient biodegradable siRNA carriers suitable for clinical applications.

PH and monovalent cations regulate cytosolic free Ca 2+ in E. coli

Abstract The results here show for the first time that pH and monovalent cations can regulate cytosolic free Ca 2+ in E. coli through Ca 2+ influx and efflux, monitored using aequorin. At pH 7.5 the resting cytosolic free Ca 2+ was 0.2–0.5 µM. In the presence of external Ca 2+ (1 mM) at alkaline pH this rose to 4 µM, being reduced to 0.9 µM at acid pH. Removal of external Ca 2+ caused an immediate decrease in cytosolic free Ca 2+ at 50–100nM s − 1 . Efflux rates were the same at pH 5.5, 7.5 and 9.5. Thus, ChaA, a putative Ca 2+/H +exchanger, appeared not to be a major Ca 2+-efflux pathway. In the absence of added Na +, but with 1 mM external Ca 2+, cytosolic free Ca 2+ rose to approximately 10 µM. The addition of Na +(half maximum 60 mM) largely blocked this increase and immediately stimulated Ca 2+ efflux. However, this effect was not specific, since K + also stimulated efflux. In contrast, an increase in osmotic pressure by addition of sucrose did not significantly stimulate Ca 2+ efflux. The results were consistent with H + and monovalent cations competing with Ca 2+ for a non-selective ion influx channel. Ca 2+ entry and efflux in chaA and yrbG knockouts were not significantly different from wild type, confirming that neither ChaA nor YrbG appear to play a major role in regulating cytosolic Ca 2+ in Escherichia coli. The number of Ca 2+ ions calculated to move per cell per second ranged from < 1 to 100, depending on conditions. Yet a single eukaryote Ca 2+ channel, conductance 100 pS, should conduct > 6 million ions per second. This raises fundamental questions about the nature and regulation of Ca 2+ transport in bacteria, and other small living systems such as mitochondria, requiring a new mathematical approach to describe such ion movements. The results have important significance in the adaptation of E. coli to different ionic environments such as the gut, fresh water and in sea water near sewage effluents.

Role of Extension Arm in PEG-Hb Conjugates on the Stability of the Tetramer: Non-conservative EAF Maleimide Thio-PEG Mediated PEGylation

PEGylation induced increase in colloidal osmotic pressure (COP) of Hb, one of the unique molecular properties of PEG-Hb conjugates, facilitates the neutralization of the vasoconstrictive activity of acellular Hb is a function of chemistry of conjugation of PEG-chains. The dependence of COP with the chemistry is a consequence of PEGylation induced weakening of interdimeric interactions. The conservative Extension Arm Facilitated (EAF) PEGylation exerts least influence on lowering the tetramer stability as compared to direct PEGylation. We have now designed a new, non-conservative EAF PEGylation that uses acylation chemistry to introduce the extension arm onto proteins to delineate the role of the extension arm and of the charge at the site of attachment in PEG-Hb conjugate on tetramer stability. The non-conservative EAF PEGylation does not lower the tetramer stability just as the non-conservative direct PEGylation of Hb. The impact of the extension arm in PEGylated Hb in terms of their structure and potential significance of higher tetramer stability of PEG-Hb conjugates generated by EAF-PEGylation in the in vivo toxicity and in the design of oxygen carrying plasma expander has been discussed.

Protein osmotic pressure modulates actin filament length distribution

1. The changes of the macromolecular osmotic pressure associated with F-actin solutions are related to the changes of the free energy of the free actin monomers. 2. By making use of the model of Biron et al. [2006. Inter-filament attractions narrow the length distribution of actin filaments. Europhys. Lett. 73, 464–470], the changes of the free energy of the free actin monomers are related to the changes of the length distribution of the actin filaments. On these bases, we propose that the length distribution of the actin filaments is regulated by (a) the free energy of hydrolysis of ATP and (b) the macromolecular osmotic pressure. a. While the free energy of hydrolysis of ATP tends to zero, the length distribution of the actin filaments shifts from an exponential curve to a straight line parallel to the abscissa axis (i.e. the concentration of the actin filaments becomes independent of their length). In the mean time, the total energy of the actin filaments reaches a minimum. b. With the increase of the macromolecular osmotic pressure the free energy of the actin monomers increases and a break is introduced in the curve that describes the length distribution of the actin filaments; the break is located at the mean length of the filaments.

Improved salt tolerance in tobacco plants by co-transformation of a betaine synthesis gene BADH and a vacuolar Na+/H+ antiporter gene SeNHX1

Three types of transgenic tobacco plants were acquired by separate transformation or co-transformation of a vacuolar Na(+)/H(+) antiporter gene, SeNHX1, and a betaine synthesis gene, BADH. When exposed to 200 mM NaCl, the dual gene-transformed plants displayed greater accumulation of betaine and Na(+) than their wild-type counterparts. Photosynthetic rate and photosystem II activity in the transgenic plants were less affected by salt stress than wild-type plants. Transgenic plants exhibited a greater increase in osmotic pressure than wild-type plants when exposed to NaCl. More importantly, the dual gene transformed plants accumulated higher biomass than either of the single transgenic plants under salt stress. Taken together, these findings indicate that simultaneous transformation of BADH and SeNHX1 genes into tobacco plants can enable plants to accumulate betaine and Na(+), thus conferring them more tolerance to salinity than either of the single gene transformed plants or wild-type tobacco plants.

Ultraweak emissions of developing Xenopus laevis eggs and embryos

We measured ultraweak emissions of the Xenopus laevis eggs and embryos during normal development and under the influence of stress factors in a spectral range of 250 to 800 nm using a photomultiplier. The registered emissions were analyzed by several basic characteristics: mean intensity, histograms, kurtosis, linear trends, and Fourier spectra. We followed relationships between these parameters and developmental stage, as well as the number of individuals in optic contact with each other. The ultraweak emissions did not differ from the background at all developmental stages according to the mean intensity. But Fourier analysis revealed the reliable presence of a number of spectral lines of ultraweak emission, predominantly in the ranges of 10-20 and 30-40 Hz, in the embryos at developmental stages 2 to 11. The intensity of ultraweak emissions reliably decreased within the first 10 min after egg activation and fertilization, as well as in the case of optic interaction between groups of embryos. Sharp cooling, increase in osmotic medium pressure, and transfer in a Ca(2+)- and Mg(2+)-free medium induced a short term (approximately 1-5 min) increase in the mean intensity of ultraweak emission. We studied specific features of ultraweak emissions from different parts of the embryo. The intensity of emission from the animal part of early blastula exceeded those from the vegetal area and entire embryo. Separated fragments of the lateral ectoderm at the neurula stage had higher mean intensities of ultraweak emission than intact embryos at the same developmental stages.