A model of an ideal associated solution, containing self-associates of different sizes and shapes, was considered. Calculations
of the thermodynamic properties of mixing of Na-K liquid alloys and of liquidus line positions were carried out. Possible
modifications of the model are discussed.
Authors:MM Khalisov, AV Ankudinov, VA Penniyaynen, D Dobrota, and Boris V. Krylov
, Rogachevsky IV , Butkevich IP , Mikhailenko VA , Kipenko AV , Krylov BV : Modulation of signal-transducing function of neuronal membrane Na + , K + -ATPase by endogenous ouabain and low-power infrared radiation leads to pain relief . Med. Chem. 8 , 33
DSC studies are carried out to characterize Na+,K+-ATPase isolated from pig kidney in its natural membrane environment as well as in its purified state upon detergent treatment. The transition temperatures of the investigated thermal protein unfolding process, observed between 43 and 64.5° C, depend on the local membrane environment as well as onpH. In addition, the transition temperature is significantly increased upon binding of different cations and ligands which are known to interact with the enzyme. Evidence for a lipid phase transition around 23 °C in the original biological membrane is reported.
The liquid-solid phase diagram of the binary systems AlPO4−M3PO4(M=Li, Na, K) have been established. The additional compounds Na3Al(PO4)2, Na3Al2(PO4)3 and K3Al2(PO4)3 have been found again. A new compound K3Al(PO4)2 is observed. The melting point of Na3PO4 is 1545°C and K3PO4 does not melt up to 1700°C.
Seasonal changes of nitrogen metabolites and Na
ratio were detected in some wild species inhabiting the western desert of Egypt. Seasons, species and their interactions were important factors affecting the total free amino acids and soluble proteins at Dakhla oasis; however, species diversity is more effective variable in regulating such metabolites at Kharga region. Such plants may respond to their environment either by increasing their water binding molecules or by preventing the formation of amino acids into proteins. Some halophytes and xerophytes may adjust osmotically to stress by the contribution of nitrogen metabolites. On the other hand,
, the succulent plant, may adapt to environmental conditions through the accumulation of free amino acids. The correlation analysis between Na
ratio with free amino acids, soluble proteins and water content in
Balanites aegyptiaca, Salsola imbericata, Tamarix aphylla, Trichodesma africanum
(Kharga) indicated such changes in ionic fraction or accumulating soluble organic compounds that presumably were osmotically active and contribute to osmotic adjustment. Positive correlation was also found between chlorophyll content with ionic and nitrogen metabolites. It is likely to suggest that
Acacia nilotica, Suaeda monoica
at Dakhla may have changed their soluble proteins or ionic ratio as a consequence of chlorophyll response to stress, while
may control cellular protein contents. On the other hand, the interaction of both nitrogen metabolites and ionic fraction may play an important role of osmoregulation in
S. imbericata, Citrullus colocynthis
at Kharga region.
Thermodynamic calculations predict the formation of hydrochloric acid gas and alkali tungstates during hydrogen reduction
of WO3 doped with alkali chlorides MCl (M=Li, Na, K). The formation of HCl was proved experimentally by simultaneously coupled TG-MS
measurements from RT to 1200C. The formation of HCl is the result of the reaction between MCl, WO3 and water. Ubiquitous traces of moisture in the gas are sufficient for reaction according to WO3+(2+2n)MCl +(1+n)H2O→M2+2nWO4+n+(2+2n)HCl (n=0, 1, 2). Laboratory reduction tests showed that the formed tungstates differ. NaCl and KCl form monotungstates (n=0), while LiCl produces more lithium-rich compounds (n=1, 2). Temperature and humidity, among other process factors, control subsequent reduction of the tungstates to metals.
Authors:E. Grell, E. Lewitzki, A. Schacht, and M. Stolz
Microcalorimetric titrations allow to recognize and investigate high-affinity ligand binding to Na,K-ATPase. Titrations with
the cardiac glycoside Ouabain, which acts as a specific inhibitor of the enzyme, have provided not only the thermodynamic
parameters of high-affinity binding with a stoichiometric coefficient of about 0.6 but also evidence for low-affinity binding
to the lipid. The marked enthalpic contribution of -95 kJ mol-1 at 298.2 K is partially compensated by a large negative entropy change, attributed to an increased interaction between water
and the protein. The calorimetric ADP and ATP titrations at 298.2 K are indicative of high-affinity nucleotide binding either
in 3 mM NaCl, 3 mM MgCl2 or at high ionic strength such as 120 mM choline chloride. However, no binding is detected in the buffer solution alone at
low ionic strength. The affinities for ADP and ATP are similar, around 106 M-1 and the stoichiometric coefficients are close to that of Ouabain binding. The exothermic binding of ADP is characterized
by a ΔH and ΔS value of -65 kJ mol-1 and -100 J mol-1 K-1, respectively. TheΔH value for ATP binding is larger than for ADP and is compensated by a larger, unfavorable ΔS value. This
leads to an enthalpy/entropy compensation, which could express that H-bond formation represents the major type of interaction.
As for Ouabain, the negative ΔS values that are also characteristic of nucleotide binding can indicate an increase of solvate
interaction with the protein due to a conformational transition occurring subsequent to the binding process. The resulting
binding constants are discussed with regard to the results of other studies employing different techniques. A molecular interaction
model for nucleotide binding is suggested.
The transport of metal ions (Ca2+, Sr2+, Ba2+, Na+, K+, Cs+) through hollow fiber supported dichlorobenzene liquid membrane has been studied. The transport of cations using 8-crown-6 ether as a carrier and picrate as co-counter ion as well as a pertraction device and capillary isotachophoresis (ITP) measurement of the cation concentration is described.
Increases in extracellular potassium (K
) concentration (up to 20 mM) cause dilation in some blood vessels. This may be particularly important in myocardial ischemia because in this condition K
is released from ischemic cells. In this study, we investigated mechanisms of effect of increased K
concentration on the tone of isolated bovine coronary artery. Bovine coronary arteries were isolated and mounted in organ baths for isometric tension recording. After an equilibration period, arteries were contracted with serotonin (1 μM). When serotonin contraction reached a steady-state, K
concentration of organ baths was increased from physiological levels to 10 mM, 14 mM, 18 mM or 22 mM in four groups of the arteries. After a washout period, this procedure was repeated in presence of ouabain, a blocker of Na
ATPase or a K
channel blocker (tetraethylammonium, 4-aminopyridine, glibenclamide or barium). Increasing K
concentration of the organ baths to 10 mM, 14 mM and 18 mM caused dilation in the arteries. Ouabain abolished the dilation and barium (a blocker of inward rectifier K
channels) inhibited the dilation significantly.According to our results there is K
-induced dilation in bovine coronary artery and it involves activation of both Na
ATPase and inward rectifier K