scholarly journals Site correlations, capacitance, and polarizability from protein protonisation fluctuations

2021 ◽  
Author(s):  
Anže Božič ◽  
Rudolf Podgornik
Keyword(s):  
Dipole Moment ◽  
Globular Protein ◽  
Bathing Solution ◽  
Total Charge ◽  
Total Dipole Moment ◽  
Solution Ph ◽  
Similar Dependence

We generalize the Kirkwood-Shumaker theory of protonisation fluctuation for an anisotropic distribution of dissociable charges on a globular protein. The fluctuations of the total charge and the total dipole moment, in contrast to their average values, depend on the same proton occupancy correlator, thus exhibiting a similar dependence also on the solution pH. This has important consequences for the Kirkwood-Shumaker interaction and its dependence on the bathing solution conditions.

Effect of pH on chloride absorption in the flounder intestine

1988 ◽  
Vol 255 (2) ◽  
pp. G247-G252 ◽  
Author(s):  
A. N. Charney ◽  
J. I. Scheide ◽  
P. M. Ingrassia ◽  
J. A. Zadunaisky
Keyword(s):  
Small Intestine ◽  
Short Circuit ◽  
Ph Effect ◽  
Short Circuit Current ◽  
Bathing Solution ◽  
Solution Ph ◽  
Transport Pathway ◽  
Ussing Chambers ◽  
Chloride Absorption ◽  
In Series

Chloride absorption in the small intestine of the winter flounder, Pseudopleuronectes americanus, is reported to be sensitive to ambient pH. We studied this sensitivity in isolated stripped intestinal mucosa mounted in modified Ussing chambers. Unidirectional 36Cl fluxes (JClm----s, JCls----m) were measured under short-circuited conditions in bathing solutions containing various combinations of HCO3- (0-20 mM), partial pressure of CO2 (0-36 mmHg), and pH (6.77-7.85). We found that JClm----s, net 36Cl flux (JClnet), and short-circuit current (Isc) increased and JCls----m decreased predominately in response to increases in bathing solution pH. There was a linear relationship between pH and both JClnet (r = 0.92, P less than 0.01) and Isc (r = 0.96, P less than 0.005) between pH 6.77 and 7.74. The pH effect was completely reversible, did not require either CO2 or HCO3-, and was not affected by the presence of mucosal barium at 1 mM. Mucosal bumetanide (0.1 mM) completely inhibited the pH effect. These data suggest that the process by which Cl- is absorbed in the flounder intestine is sensitive to pH. The data do not indicate whether pH affects Na+-K+-2Cl- cotransport or a Cl- transport pathway in series with this process. The direction of Cl- absorption in response to pH contrasts with inverse relation of pH and Cl- absorption in mammalian small intestine.

Glycine Binding Site of the Synaptic NMDA Receptor in Subpostremal NTS Neurons

2005 ◽  
Vol 94 (1) ◽  
pp. 147-152 ◽  
Author(s):  
Vander Baptista ◽  
Wamberto Antonio Varanda
Keyword(s):  
Nmda Receptor ◽  
Binding Site ◽  
Reversal Potential ◽  
Postsynaptic Membrane ◽  
Bathing Solution ◽  
Total Charge ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Autonomic Reflex ◽  
Transverse Slice

The nucleus of the tractus solitarius (NTS) plays an important role in the control of several autonomic reflex functions and has glutamate and GABA as main neurotransmitters. In this work, we used patch-clamp recordings in transverse slice preparations from rats to study whether the glycine binding site of the N-methyl-d-aspartate (NMDA) receptor is saturated or not in neurons of the subpostremal NTS. Except at hyperpolarized voltages and close to the reversal potential, glycine potentiated the NMDA responses in a concentration-dependent manner. The total charge transferred by glutamatergic currents was enhanced by glycine (500 μM; from 28 ± 13 to 42 ± 18 pC at +50 mV, n = 7, P < 0.05). Glycine increased the conductance of the postsynaptic membrane, without altering its reversal potential, both in the presence (from 2.4 ± 0.06 to 3.4 ± 0.09 nS; n = 7) and absence (from 3.1 ± 0.06 to 4.4 ± 0.10 nS; n = 8) of Mg2+ in the bathing solution. d-serine, in the presence of strychnine, also increased the amplitude of the NMDA component (by 68 ± 19%, P < 0.05, n = 5). The membrane potential was hyperpolarized (16 ± 6 mV, n = 8) by glycine, suggesting the presence of inhibitory glycinergic receptors. Our results indicate that the glycine site of the NMDA receptor in neurons of the subpostremal NTS is not saturated and that glycine may act as a modulator of the NMDA transmission in this nucleus.

scholarly journals Determination of the covalent bond dipole moments with CLPO analysis

2018 ◽  
pp. 105-108
Author(s):  
T. Nikolaienko
Keyword(s):  
Dipole Moment ◽  
Particle Density ◽  
Dipole Moments ◽  
Covalent Bond ◽  
Frobenius Norm ◽  
Total Charge ◽  
Covalent Bonds ◽  
Moment Vector ◽  
Proposed Model ◽  
Nuclear Contribution

Basing on the orbitals localization method which provides the most accurate (in a Frobenius norm sense) approximation for the reduced one-particle density matrix of the molecule, the model is proposed for partitioning the dipole moment of the molecule into additive contributions, defined in CLPO basis. By augmenting the proposed model with the Ruedenberg scheme for partitioning the nuclear contribution to the dipole moment, the contributions to the dipole moment associated with particular covalent bonds and lone pairs of the atoms were determined. Using the datasets composed of 11410 12-atomic molecules with zero total charge and the set of 613 conformations of electroneutral 2'-deoxycytidine-5'-monophosphate molecule, it has been found that the error in approximating the total dipole moment of the molecule by the sum of localized contributions, determined in the framework of the proposed model, is close to 10%, and is noticeably below the similar error when only the NPA charges are used to compute the approximate dipole moment. The typical angle between the true dipole moment vector and the dipole moment vector approximated with the proposed model is 5.5 deg.

scholarly journals Modelling of electromagnetic properties of multicomponent material

2018 ◽  
Vol 84 (7) ◽  
pp. 38-41
Author(s):  
V. P. Krylov
Keyword(s):  
Magnetic Properties ◽  
Dipole Moment ◽  
Heterogeneous Media ◽  
Dielectric Permeability ◽  
Electromagnetic Properties ◽  
Heuristic Model ◽  
Total Dipole Moment ◽  
Electrodynamic Parameter ◽  
Multicomponent Material

Current theories of heterogeneous media consider non-uniform materials as natural and artificially synthesizable structures. Nowadays, synthesis of the non-uniform multicomponent materials with given electrodynamic properties and characterized by magnetic and dielectric permeability, is gaining increasing development. When modeling a multicomponent structure as a uniform material with effective dielectric permeability (ignoring the magnetic properties) using the developed models for the components with known dielectric permeability, the errors arise in calculation of the transmission coefficient of a plane wave through the antenna dome wall. We present a heuristic model based on the laws of optics which is intended for simultaneous determination of the effective magnetic and dielectric permeability of multicomponent material in contrast to known models describing statistically non-uniform media only for one electrodynamic parameter. The electrodynamic model developed for description of the effective magnetic and dielectric permeability of non-uniform material suggests a possibility of characterizing a polarized material with the total dipole moment arising in alternating field and expressing the Brewster angle as a the sum of the polarization angles proportional to volume content the mixture components.

scholarly journals Cytoplasmic pH and Goblet Cavity pH in the Posterior Midgut of the Tobacco Hornworm Manduca Sexta

1991 ◽  
Vol 155 (1) ◽  
pp. 403-414 ◽  
Author(s):  
ANTHONY C. CHAO ◽  
DAVID F. MOFFETT ◽  
ALAN KOCH
Keyword(s):  
Goblet Cell ◽  
Apical Membrane ◽  
Electrical Potential ◽  
Basal Membrane ◽  
Bathing Solution ◽  
Cytoplasmic Ph ◽  
Active Process ◽  
Solution Ph ◽  
Posterior Midgut ◽  
K Secretion

In the larval lepidopteran midgut, the major energy-requiring step of transepithelial K+ secretion occurs across the goblet cell apical membrane. Studies of vesicles of goblet cell apical membrane suggest that K+ secretion across this membrane is a secondary active process in which electroneutral K+/H+ antiport is driven by primary electrogenic H+ secretion. Transbasal K+ movement is thermodynamically passive under standard conditions, but the presence of an active process is revealed in hypoxic solutions or at low extracellular K+ concentration. We measured the pH of cytoplasm and goblet cell cavities, together with the corresponding transmembrane voltages, using double-barreled pH and voltagesensing microelectrodes. For short-circuited midguts in standard bathing solution (pH 8.0) the weighted mean of cytoplasmic pH was 7.14±0.06 (mean±S.E.M.), an average of 0.34 units more acid than expected for electrochemical equilibrium with the hemolymphal solution. The mean pH of goblet cavities was 7.23±0.11, 1.62 units more acid than expected for equilibrium with the luminal solution. The pH gradient across the goblet cell apical membrane is thus of the wrong polarity to drive K+ secretion by electroneutral K+/H+ antiport; however, if the exchange ratio were two or more H+ per K+, the cavity-positive electrical potential could drive H+ back to the goblet cell cytoplasm coupled to K+ secretion from cytoplasm to the goblet cavity. Insensitivity of the goblet cavity pH to the change in the transvalve voltage caused by open-circuiting suggests either that the goblet cavity pH is well regulated or that the valve connecting the cavity to the gut lumen poses a significant barrier to protons. Transbasal potential and cytoplasmic pH were insensitive to a decrease of hemolymphal pH to 6.8, suggesting that the basal membrane is relatively nonconductive to H+. Intracellular pH was unaffected by a decrease of hemolymphal K+ to 5 mmol l−1, suggesting that K+/H+ exchange is not important for transbasal K+ uptake.

Dipole moments of hydroxamic acids and N,O-diacylhydroxylamines

1981 ◽  
Vol 46 (3) ◽  
pp. 729-739 ◽  
Author(s):  
Aleksandr I. Artemenko ◽  
Inga V. Tikunova ◽  
Evgenii K. Anufriev ◽  
Václav Jehlička ◽  
Otto Exner
Keyword(s):  
Hydrogen Bond ◽  
Dipole Moment ◽  
Intramolecular Hydrogen Bond ◽  
Dipole Moments ◽  
Hydroxamic Acids ◽  
The Other ◽  
Total Dipole Moment ◽  
Statistical Population ◽  
Intramolecular Hydrogen ◽  
Peroxy Acids

Dipole moments of nine aromatic hydroxamic acids Ia-Ii and of nine N,O-diacylhydroxylamines IIa-IIi were measured in dioxan solution. The results for hydroxamic acids are interpreted in terms of the Zsp conformation (A) with an intramolecular hydrogen bond contributing considerably to the total dipole moment; the conformation is similar to that of peroxy acids but the hydrogen bond is weaker. A similar interpretation is possible for N-phenylbenzhydroxamic acids using the dipole moment data from the literature. New data for N,O-diacylhydroxylamine agree with the previously established nonplanar conformation (L). If axially unsymetrical aryl groups are present, they take one of the two coplanar positions independently of the other moiety; hence the effective dipole moments do not differ too much from the assumption of a statistical population of all conformations.

pH sensitivity of the basolateral membrane of the rabbit proximal tubule

1986 ◽  
Vol 250 (2) ◽  
pp. F261-F266 ◽  
Author(s):  
B. A. Biagi ◽  
M. Sohtell
Keyword(s):  
Potassium Concentration ◽  
Ph Dependence ◽  
Basolateral Membrane ◽  
Rabbit Kidney ◽  
Bathing Solution ◽  
Solution Ph ◽  
Absolute Value ◽  
Ph Dependent ◽  
Basolateral Membrane Potential

Conventional microelectrodes were used to study the effects of bath pH and bicarbonate concentrations on the basolateral membrane potential (Vbl) of cells from the superficial proximal convoluted (PCT) and proximal straight (PST) tubules of the rabbit kidney perfused in vitro. Bathing solution pH was varied over the range of 5.9-7.4 using either control (22-25 mM) or low bicarbonate (5.0-6.6 mM) Ringer solutions and the appropriate CO2 tensions. The results show a strong pH dependence of the steady-state values of Vbl in both the convoluted and straight tubule segments. The pH-dependent depolarization was approximately 35 mV/pH unit change of the bathing solution in the acid direction and could be demonstrated in CO2-free HEPES-buffered solutions. A depolarizing response to increased bath potassium concentration (HK) was observed that was linearly related to the absolute value of the Vbl under control conditions. Under acidotic conditions, reduced HK depolarizations indicate that a decrease in the relative potassium permeability of the basolateral membrane is the principle mechanism underlying the effects of bath pH on Vbl.

Rotational Isomerism and the Orientation of the Total Dipole Moment

1980 ◽  
Vol 35 (7) ◽  
pp. 748-756 ◽  
Author(s):  
Ivan Botskor
Keyword(s):  
Experimental Data ◽  
Dipole Moment ◽  
Gas Phase ◽  
Dipole Moments ◽  
Microwave Spectroscopy ◽  
Rotational Isomerism ◽  
Total Dipole Moment

A method for determining the orientation of the total dipole moments of distinct rotamers of the same molecule is discussed. Utilizing solely the experimental dipole moments obtained with microwave spectroscopy (gas phase) and an approximate structure, the orientation of the dipole moment can often be determined without use of bond moment considerations. Experimental data from nine rotamer pairs are analyzed to illustrate the method.

Acid-base effects on ileal sodium chloride absorption in vitro

1988 ◽  
Vol 254 (3) ◽  
pp. G329-G333 ◽  
Author(s):  
S. G. Vaccarezza ◽  
A. N. Charney
Keyword(s):  
Sodium Chloride ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Acid Base Balance ◽  
Acid Base ◽  
Solution Ph ◽  
Ussing Chambers ◽  
Hepes Buffer ◽  
Chloride Absorption

Previous work from this laboratory has shown that in the intact animal, ileal sodium chloride absorption is responsive to alterations in systemic acid-base balance. In vitro studies were undertaken to determine the nature of the active transport process affected. Paired, unstripped ileal tissues from Sprague-Dawley rats were mounted in modified Ussing chambers, and unidirectional 22Na and 36Cl fluxes were measured under short-circuited conditions (Isc). Acid-base effects were examined by changing either bathing solution partial pressure of CO2 (PCO2) or HCO3 concentration or by the addition of HCl or NaOH to a non-HCO3 N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer. When pH was decreased from 7.6 to 7.1, net sodium absorption increased twofold regardless of the means by which pH was changed. This increase was primarily accounted for by an increase in mucosal-to-serosal flux. Net chloride absorption was affected in a similar way, but the increase in absorption was primarily accounted for by an increase in mucosal-to-serosal flux only in the HEPES buffer. These changes were accompanied by reductions in Isc and residual flux. When all groups were considered, mucosal-to-serosal Na (JNam----s) and net Na (JNanet) fluxes correlated strongly with bathing solution pH (r = 0.84 and 0.94, respectively, P less than 0.01). These data indicate that an active ileal sodium chloride absorptive process is specifically responsive to changes in bathing solution pH. In addition, pH may affect ileal electrogenic chloride, HCO3, and/or H secretion.

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