Presence Of Low Salt Concentration Research Articles

Physiological and chemical characteristics of safflower (Carthamus tinctorius L.) grown in the presence of low salt concentrations

(Carthamus tinctorius L.) is highly regarded in the world as an aromatic, spicy, medicinal and oilseed crop, which can be used in all kinds of industries. It inhabits arid and semiarid areas of the world. The influence of the relatively low NaCl concentrations found in soils and irrigation waters on the growth and metabolism of saf?flower, grown under semi-controlled conditions, was examined in this work. It was found that increased concentrations of NaCl affected the number of leaves per plant and dry leaves mass/area ratio. The transpiration intensity was reduced in plants grown in the presence of NaCl and stomatal diffusive resistance increased following an increase in NaCl concentration.

Escherichia coli YqjA, a Member of the Conserved DedA/Tvp38 Membrane Protein Family, Is a Putative Osmosensing Transporter Required for Growth at Alkaline pH.

The ability to persist and grow under alkaline conditions is an important characteristic of many bacteria. In order to survive at alkaline pH, Escherichia coli must maintain a stable cytoplasmic pH of about 7.6. Membrane cation/proton antiporters play a major role in alkaline pH homeostasis by catalyzing active inward proton transport. The DedA/Tvp38 family is a highly conserved membrane protein family of unknown function present in most sequenced genomes. YqjA and YghB are members of the E. coli DedA family with 62% amino acid identity and partially redundant functions. We have shown that E. coli with ΔyqjA and ΔyghB mutations cannot properly maintain the proton motive force (PMF) and is compromised in PMF-dependent drug efflux and other PMF-dependent functions. Furthermore, the functions of YqjA and YghB are dependent upon membrane-embedded acidic amino acids, a hallmark of several families of proton-dependent transporters. Here, we show that the ΔyqjA mutant (but not ΔyghB) cannot grow under alkaline conditions (ranging from pH 8.5 to 9.5), unlike the parent E. coli. Overexpression of yqjA restores growth at alkaline pH, but only when more than ∼100 mM sodium or potassium is present in the growth medium. Increasing the osmotic pressure by the addition of sucrose enhances the ability of YqjA to support growth under alkaline conditions in the presence of low salt concentrations, consistent with YqjA functioning as an osmosensor. We suggest that YqjA possesses proton-dependent transport activity that is stimulated by osmolarity and that it plays a significant role in the survival of E. coli at alkaline pH. The ability to survive under alkaline conditions is important for many species of bacteria. Escherichia coli can grow at pH 5.5 to 9.5 while maintaining a constant cytoplasmic pH of about 7.6. Under alkaline conditions, bacteria rely upon proton-dependent transporters to maintain a constant cytoplasmic pH. The DedA/Tvp38 protein family is a highly conserved but poorly characterized family of membrane proteins. Here, we show that the DedA/Tvp38 protein YqjA is critical for E. coli to survive at pH 8.5 to 9.5. YqjA requires sodium and potassium for this function. At low cation concentrations, osmolytes, including sucrose, can facilitate rescue of E. coli growth by YqjA at high pH. These data are consistent with YqjA functioning as an osmosensing cation-dependent proton transporter.

Effect of rootstocks grafting and boron on the antioxidant systems and salinity tolerance of loquat plants ( Eriobotrya japonica Lindl.)

Salinity causes serious economic losses in loquat production, emphasising the needs to explore new ways to reduce the losses. Grafting of loquat plants on anger rootstock did not affect growth of loquat plants with 20 mM (moderate concentration) and 35 mM (high concentration) NaCl in the nutritive solution. However, when grafted on loquat rootstock, 20 mM NaCl produced a 44% decrease in plant growth, whereas the higher NaCl concentration used produced a 65% of plant growth inhibition. The addition of B did not produce significant changes in plant growth in any case. Leaf Na concentration increased in salt-treated loquat plants, the rise being higher when plants were grafted on loquat rather than anger rootstocks. In contrast, leaf Cl contents did not show changes in loquat plants, independent of the rootstock used. Only in loquat plants grafted on loquat rootstocks did B additions produce an accumulation of B in leaves, in the absence and in the presence of NaCl stress. Moderate salt-treatment produced an increase in APX and a decrease in PPO in plant grafted on loquat rootstock, whereas an increase in MDHAR, PPO as well as a decrease in SOD was observed in those plants subjected to the higher salt treatment. In the presence of low salt concentration (5 mM, control plants), B additions brought about an increase in APX and MDHAR and a fall in POX and PPO in plants grafted on anger rootstocks. However, a decrease in PPO was observed in plants grafted on loquat rootstocks. In plants grafted on loquat rootstocks and treated with 20 mM NaCl, 0.2 mM B additions produced a decrease in APX and a rise in POX, whereas in the presence of the higher NaCl concentration, B produced an increase in APX and DHAR and a decrease in POX and PPO activities. In contrast, in salt-treated plants grafted on anger rootstocks, both B levels produced an increase in SOD, whereas a decrease was produced in PPO activity by effect of 0.2 mM B in plants treated with 20 mM NaCl. However, in plants treated with the higher NaCl level, 0.2 mM B produced a strong increase in DHAR. In both cases, salinity produced an oxidative stress as shown by the increase in lipid peroxidation, the values being higher in plants grafted on loquat rootstocks. The presence of B produced a decrease in the lipid peroxidation values, suggesting that B additions afforded some protection to the membranes, mainly in plants grafted on anger stocks. This response was correlated with the higher SOD, MDHAR and DHAR activity values observed under these conditions. Overall, the data suggest that anger plants seem to be a better rootstock for loquat plants than their own loquat rootstock. Also, leaves from loquat plants grafted on anger rootstocks seem to have a higher antioxidant capacity, as deduced from the data on SOD, MDHAR and DHAR activities as well as lipid peroxidation data.

DNA condensation by high-affinity interaction with avidin.

Avidin, the basic biotin-binding glycoprotein from chicken egg white, is known to interact with DNA, whereas streptavidin, its neutral non-glycosylated bacterial analog, does not. In the present study we investigated the DNA-binding properties of avidin. Its affinity for DNA in the presence and absence of biotin was compared with that of other positively charged molecules, namely the protein lysozyme, the cationic polymers polylysine and polyarginine and an avidin derivative with higher isoelectric point (pI approximately 11) in which most of the lysine residues were converted to homoarginines. Gel-shift assays, transmission electron microscopy and dynamic light scattering experiments demonstrated an unexpectedly strong interaction between avidin and DNA. The most pronounced gel-shift retardation occurred with the avidin-biotin complex, followed by avidin alone and then guanidylated avidin. Furthermore, ultrastructural and light-scattering studies showed that avidin assembles on the DNA molecule in an organized manner. The assembly leads to the formation of nanoparticles that are about 50-100 nm in size (DNA approximately 5 kb) and have a rod-like or toroidal shape. In these particles the DNA is highly condensed and one avidin is bound to each 18 +/- 4 DNA base pairs. The complexes are very stable even at high dilution ([DNA] =10 pM) and are not disrupted in the presence of buffers or salt (up to 200 mM NaCl). The other positively charged molecules also condense DNA and form particles with a globular shape. However, in this case, these particles disassemble by dilution or in the presence of low salt concentration. The results indicate that the interaction of avidin with DNA may also occur under physiological conditions, further enhanced by the presence of biotin. This DNA-binding property of avidin may thus shed light on a potentially new physiological role for the protein in its natural environment.

Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

We report on the viscous behaviour of long and flexible wormlike micelles at volume fractions between Ø = 0.05–0.14 comprised of sodium laurylethersulfate (SLES) in 0.15–0.5 M NaCl equivalent of SLES concentrations between 20–50 mM at temperatures ranging from 25 °C to 45 °C by means of static and dynamic light scattering and rheology, which is an extension of previous experiments on dilute/semi-dilute solutions of SLES micelles at much lower surfactant concentrations in the presence of low salt concentrations (Clancy and Paradies, Z. Phys. Chem.

Viscometric behaviour of polyelectrolytes in the presence of low salt concentration

The purpose of this paper is to draw a general picture for viscometric behaviour of polyelectrolytes. The polymers tested are hyaluronan ( λ=0.7) and sodium polystyrene sulfonate ( λ=2.8) with different molecular weights. The viscometric behaviour in isoionic dilution is examined and one demonstrates that k′[ η]∼ C s −3/2. Dilution in water or with solvent of low salt concentration causes the reduced viscosity to pass through a maximum for a given polymer concentration. The position of the maximum and the amplitude of this maximum is analyzed for the low molecular weight samples in the dilute regime. The electrostatic contribution dominates and the treatment adopted gives good agreement between calculated and experimental data.

Maintenance of Photophosphorylation Despite Inhibition of the Transthylakoid pH Gradient by Tetracaine

The inhibition of the transthylakoid pH gradient, ΔpH, and of photophosphorylation by the local anesthetic tetracaine was investigated with isolated chloroplasts from Spinacia oleracea L. Tetracaine strongly inhibited ΔpH in the presence of low salt concentrations. In the presence of high salt concentrations, the inhibition of ΔpH was much smaller. This effect of salt concentration was observed only when both, cation and anion were easily membrane permeable. It was concluded that the effect of salts on ΔpH inhibition was excerted on the inside of the thylakoid membrane. The rate of photophosphorylation, Vp, driven by the PS Idependent artificial proton carrier phenazine methosulfate decreased with ΔpH in the presence of both, high and low salt concentrations. In contrast, Vp driven by the endogenous proton pumps of PS II + I-dependent linear electron flow was largely independent of ΔpH changes in the presence of low salt concentration. It appeared that energy coupling during linear electron transport, in contrast to artificially produced PS I-dependent coupling, may be localized to membrane-bound proton domains which are not accessible to the employed indicators of ΔpH. The data were discussed with respect to recent hypotheses on localized energy coupling in chloroplasts.

Isolation and characterization of myosin from amoebae of Physarum polycephalum.

Myosin was isolated from amoebae of Physarum polycephalum and compared with myosin from plasmodia, another motile stage in the Physarum life cycle. Amoebal myosin contained heavy chains (Mr approximately 220,000), phosphorylatable light chains (Mr 18,000), and Ca2+-binding light chains (Mr 14,000) and possessed a two-headed long-tailed shape in electron micrographs after rotary shadow casting. In the presence of high salt concentrations, myosin ATPase activity increased in the following order: Mg-ATPase activity less than K-EDTA-ATPase activity less than Ca-ATPase activity. In the presence of low salt concentrations, Mg-ATPase activity was activated approximately 9-fold by skeletal muscle actin. This actin-activated ATPase activity was inhibited by micromolar levels of Ca2+. Amoebal myosin was indistinguishable from plasmodial myosin in ATPase activities and molecular shape. However, the heavy chain and phosphorylatable light chains of amoebal myosin could be distinguished from those of plasmodial myosin in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, peptide mapping, and immunological studies, suggesting that these are different gene products. Ca2+-binding light chains of amoebal and plasmodial myosins were found to be identical using similar criteria, supporting our hypothesis that the Ca2+-binding light chain plays a key role in the inhibition of actin-activated ATPase activity in Physarum myosins by micromolar levels of Ca2+.

Quantitative studies on the interaction of azure a with deoxyribonucleic acid and deoxyribonucleoprotein

The interaction of the cationic dye azure A with DNA or deoxyribonucleoprotein can result in two interdependent phenomena: at relatively low concentrations of the dye (< 2·10 −5 M) or with excess of the polyanion, a metachromatic complex appears in the solution, whereas at higher dye concentrations and with excess of dye the polyanion-dye complex precipitates. In the latter case, the amount of dye bound in the precipitate can be calculated from measuring the absorbancy of the supernatant free dye left in the dye bath. Utilizing this principle, the dyebinding of DNA and DNPr has been determined quantitatively and various conditions which influence the extent of the binding, such as pH, the presence of salts and the effect of dye concentration, have been investigated for both substances. The results indicate a quantitative, stoichiometric binding of azure A by DNA, corresponding to a 1:1 molar ratio between DNA phosphate and the dye bound. In the case of DNPr, the corresponding ratio is about 1:2, indicating that only about half of the binding sites is available for the dye. Whereas the binding ratio in the case of DNA is independent of the dye concentration —provided excess dye is present—and the binding is not influenced by the presence of low salt concentrations (< 0.3 M NaCl), the binding of azure A by DNPr can be increased considerably in the presence of salts, especially when higher concentrations of the dye are used. The possible implications of these results for the nature of the DNA-histone bond and for the use of cationic dyes for studies of nucleic acids at the tissue level are discussed.

Quantitative studies on the interaction of azure a with deoxyribonucleic acid and deoxyribonucleoprotein

The interaction of the cationic dye azure A with DNA or deoxyribonucleoprotein can result in two interdependent phenomena: at relatively low concentrations of the dye (< 2·10−5M) or with excess of the polyanion, a metachromatic complex appears in the solution, whereas at higher dye concentrations and with excess of dye the polyanion-dye complex precipitates. In the latter case, the amount of dye bound in the precipitate can be calculated from measuring the absorbancy of the supernatant free dye left in the dye bath. Utilizing this principle, the dyebinding of DNA and DNPr has been determined quantitatively and various conditions which influence the extent of the binding, such as pH, the presence of salts and the effect of dye concentration, have been investigated for both substances. The results indicate a quantitative, stoichiometric binding of azure A by DNA, corresponding to a 1:1 molar ratio between DNA phosphate and the dye bound. In the case of DNPr, the corresponding ratio is about 1:2, indicating that only about half of the binding sites is available for the dye. Whereas the binding ratio in the case of DNA is independent of the dye concentration —provided excess dye is present—and the binding is not influenced by the presence of low salt concentrations (< 0.3 M NaCl), the binding of azure A by DNPr can be increased considerably in the presence of salts, especially when higher concentrations of the dye are used. The possible implications of these results for the nature of the DNA-histone bond and for the use of cationic dyes for studies of nucleic acids at the tissue level are discussed.

Quantitative studies on the interaction of azure a with deoxyribonucleic acid and deoxyribonucleoprotein

The interaction of the cationic dye azure A with DNA or deoxyribonucleoprotein can result in two interdependent phenomena: at relatively low concentrations of the dye (< 2·10−5M) or with excess of the polyanion, a metachromatic complex appears in the solution, whereas at higher dye concentrations and with excess of dye the polyanion-dye complex precipitates. In the latter case, the amount of dye bound in the precipitate can be calculated from measuring the absorbancy of the supernatant free dye left in the dye bath. Utilizing this principle, the dyebinding of DNA and DNPr has been determined quantitatively and various conditions which influence the extent of the binding, such as pH, the presence of salts and the effect of dye concentration, have been investigated for both substances. The results indicate a quantitative, stoichiometric binding of azure A by DNA, corresponding to a 1:1 molar ratio between DNA phosphate and the dye bound. In the case of DNPr, the corresponding ratio is about 1:2, indicating that only about half of the binding sites is available for the dye. Whereas the binding ratio in the case of DNA is independent of the dye concentration —provided excess dye is present—and the binding is not influenced by the presence of low salt concentrations (< 0.3 M NaCl), the binding of azure A by DNPr can be increased considerably in the presence of salts, especially when higher concentrations of the dye are used. The possible implications of these results for the nature of the DNA-histone bond and for the use of cationic dyes for studies of nucleic acids at the tissue level are discussed.