Papers by Gerrard Marangoni
Frontiers in Neuroscience, May 12, 2023
Lactate, the redox-balanced end product of glycolysis, travels within and between cells to fulfil... more Lactate, the redox-balanced end product of glycolysis, travels within and between cells to fulfill an array of physiologic functions. While evidence for the centrality of this lactate shuttling in mammalian metabolism continues to mount, its application to physical bioenergetics remains underexplored. Lactate represents a metabolic "cul-de-sac," as it can only re-enter metabolism by first being converted back to pyruvate by lactate dehydrogenase (LDH). Given the differential distribution of lactate producing/consuming tissues during metabolic stresses (e.g., exercise), we hypothesize that lactate shuttling vis-à-vis the exchange of extracellular lactate between tissues serves a thermoregulatory function, i.e., an allostatic strategy to mitigate the consequences of elevated metabolic heat. To explore this idea, the rates of heat and respiratory oxygen consumption in saponinpermeabilized rat cortical brain samples fed lactate or pyruvate were measured. Heat and respiratory oxygen consumption rates, and calorespirometric ratios were lower during lactate vs. pyruvate-linked respiration. These results support the hypothesis of allostatic thermoregulation in the brain with lactate.
Canadian Journal of Chemistry, 1998
A family of two-headed surfactants, the disodium 4-alkyl-3-sulfonatosuccinates, has been synthesi... more A family of two-headed surfactants, the disodium 4-alkyl-3-sulfonatosuccinates, has been synthesized by the monoesterification of maleic anhydride and the addition of sodium bisulfite to the corresponding monoester. The properties the micelles formed by these compounds in aqueous solution, and the conformations of the chains comprising the micellar interior, have been investigated using a combination of 1-D nmr experiments and homonuclear and heteronuclear 2-D nmr techniques. The critical micelle concentrations (cmc's) and the aggregation numbers determined from the nmr experiments indicate that, in agreement with the earlier literature on other two-headed surfactant systems, these amphiphiles have high cmc's and low aggregation numbers when compared to single-headed surfactants of comparable chain length. All these results are interpreted in terms of the effect of adding a second headgroup to a single-headed, single-tailed surfactant.
Langmuir, Mar 1, 2004
The proton NMR spectra of unligated ferrous porphyrins, proposed to exist in the intermediate S =... more The proton NMR spectra of unligated ferrous porphyrins, proposed to exist in the intermediate S = 1 spin state, have been recorded and analyzed. The dominant dipolar shifts for the phenyl protons in tetraphenylporphinatoiron(I1) result in a quantitative measure of the axial magnetic anisotropy, which, together with the average moment, yield p l = 4.9 pcg and pi 1 = 3.2 peg. The resultant contact shifts for pyrrole substituents reflect extensive a spin transfer, which originates solely from porphyriniron change transfer. The contact shift pattern indicates that dxzyz is unoccupied, confirming the spin-triplet ground state. The large a contact shifts require unpaired spins in dxr,dyr, and strongly support the ground state configuration, (d,)2(dzz)2(dxz,dyz)2r which has been previously shown to be the one favored by the average moment and Massbauer data.
Solubilization in Surfactant Aggregates, 2020
Physical Chemistry Chemical Physics, 2023
Thermodynamics of partitioning of primary alcohols in solutions containing aggregates of symmetri... more Thermodynamics of partitioning of primary alcohols in solutions containing aggregates of symmetric gemini surfactants, determined from diffusion NMR, surprisingly shows little dependence on the spacer length of the gemini amphiphile.
The Journal of Physical Chemistry, 2018
Journal of Molecular Liquids, 2022
Journal of Surface Science and Technology, Apr 5, 2017
The interactions between the cationic surfactant Dodecyltrimethylammonium Bromide (DTAB) and anio... more The interactions between the cationic surfactant Dodecyltrimethylammonium Bromide (DTAB) and anionic polymer sodium carboxymethyl cellulose (Na-CMC) in aqueous medium were studied at 300K over different concentrations of Na-CMCbytensiometry,conductometry,viscometry,turbidimetryandfluorimetry.Aggregationofsurfactantwasattained intwosteps,thefirstbeingthemonomericadsorptionofsurfactantsonanionicsitesofthepolymersaturatingatlower concentrationsofsurfactantandthesecondonebeingtheformationofmicellesbysurfactantsathigherconcentrations. Mainly, two types of interactions prevailed throughout namely, electrostatic and hydrophobic interactions. Due to the variationoftheinteractionsdependingontheconcentrationsofpolymer,therehasbeenconsiderabledifferencesinthe behaviouralpatternoftheprofilesforthelowerconcentrationsofpolymercomparedtothatoftheupperones.
Journal of the Indian Chemical Society, May 1, 2023
Journal of Physical Chemistry B, Mar 7, 2018
Ibuprofen (IBF), 2-(4-isobutylphenyl) propionic acid, is a surface-active, common nonsteroidal an... more Ibuprofen (IBF), 2-(4-isobutylphenyl) propionic acid, is a surface-active, common nonsteroidal anti-inflammatory drug (NSAID), and it possesses a high critical micelle concentration (cmc) compared to that of conventional surfactants. The interactions of this common NSAID with an anionic surfactant, sodium octyl sulfosuccinate, were studied by tensiometric, fluorimetric, and calorimetric measurements to investigate this system as a possible model drug-delivery system for an NSAID like IBF, particularly in a high-dose regime for IBF. The interactions between the drug and the surfactant were modeled using a regular solution theory approach in the presence and absence of a model electrolyte (sodium iodide) and a novel nonaromatic, gemini hydrotrope, tetramethylene-1,4-bis( N, N-dimethyl- N-butylammonium)bromide (4-4-4). Both the simple and the hydrotropic electrolyte were shown to have an effect on the solution properties (aggregation parameters, interfacial properties, and thermodynamics of aggregate formation) of the drug-surfactant mixtures and on the interaction between the drug and the surfactant. Surface charges of all self-assembled systems were estimated from ζ-potential measurements, whereas density functional theory calculations showed the interaction energy comparison among all of the binary and ternary combinations. All of these results were interpreted in terms of how altering the subtle balance of hydrophobic and electrostatic forces can significantly improve the ability of these self-assembled systems to transport drug molecules.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
Presence of NaC decreases the size of long CTAT micelle whereas NaDC increases. Highlights The ... more Presence of NaC decreases the size of long CTAT micelle whereas NaDC increases. Highlights The microstructure of CTAT micelles gets altered by bile salts. NaC transforms worm-like CTAT micelles into small spherical mixed micelles. Presence of NaDC decrease CTAT micelle curvature and increases micelle size.
Journal of Colloid and Interface Science, Nov 1, 2007
Mixed micelle formation of binary cationic gemini (12-s-12, s=4, 6) and zwitterionic (N-dodecyl-N... more Mixed micelle formation of binary cationic gemini (12-s-12, s=4, 6) and zwitterionic (N-dodecyl-N,N-dimethylglycine, EBB) surfactants has been investigated by measuring the surface tension of aqueous solution as a function of total concentration at various pH values from acidic to basic, under conditions of 298.15 K and atmospheric pressure. The results were analyzed by applying regular solution theory (RST), and Motomura's theory, which allows for the calculation of the excess Gibbs energy of micellization purely on the basis of thermodynamic equations. The synergistic interactions of all the investigated cationic gemini + zwitterionic surfactants mixtures were found to be dependent upon the pH of the solution and the length of hydrophobic spacer of gemini surfactant. The evaluated excess Gibbs free energy is negative for all the systems.
Canadian Journal of Chemistry, 1999
The proton NMR spectra of unligated ferrous porphyrins, proposed to exist in the intermediate S =... more The proton NMR spectra of unligated ferrous porphyrins, proposed to exist in the intermediate S = 1 spin state, have been recorded and analyzed. The dominant dipolar shifts for the phenyl protons in tetraphenylporphinatoiron(I1) result in a quantitative measure of the axial magnetic anisotropy, which, together with the average moment, yield p l = 4.9 pcg and pi 1 = 3.2 peg. The resultant contact shifts for pyrrole substituents reflect extensive a spin transfer, which originates solely from porphyriniron change transfer. The contact shift pattern indicates that dxzyz is unoccupied, confirming the spin-triplet ground state. The large a contact shifts require unpaired spins in dxr,dyr, and strongly support the ground state configuration, (d,)2(dzz)2(dxz,dyz)2r which has been previously shown to be the one favored by the average moment and Massbauer data.
Journal of Physical Chemistry B, Jan 28, 2019
Critical micelle concentration (cmc) values have been determined for the mixed zwitterionic/catio... more Critical micelle concentration (cmc) values have been determined for the mixed zwitterionic/cationic gemini systems of N-dodecyl-N,N-dimethyl-3-ammonio-1propanesulfonate (ZW3-12)/N,N'bis(dimethyldodecyl)-,-alkanediammonium dibromide (12s-12) systems. The cmcs for the mixed systems were determined through conductivity measurements. The degree of nonideality of the interaction in the mixed micelle ( m), for each system, was determined according to Rubingh's nonideal solution theory. In most cases, the systems exhibited negative deviations (- m values) at high surfactant mole fractions of zwittergent ( ZW3-12). Specifically, the ZW3-12/12-4-12 system displayed- m values at ZW3-12 0.5, while both the ZW3-12/12-5-12 and the ZW3-12/12-6-12 system displayed- m values over the entire mole fraction range. Except for the low mole fraction range in the 12-4-12 system, these mixed surfactant systems demonstrated almost identical behaviour to the DTAB/12-2-12 system studied by Bakshi et al. providing further evidence that ZW3-12 tends to behave as a cationic surfactant in mixed surfactant systems. The manner in which the cosurfactants aggregate in the micelles was determined via 2D-NOESY spectroscopy. In the case of both the ZW3-12/12-5-12 and the ZW3-12/12-6-12 systems, the 2-D NOESY spectra exhibited strong cross peaks between the gemini and zwitterionic surfactants over the entire micellar composition range in the case of the ZW3-12/12-5-12 system. In the case of the ZW3-12/12-4-12 system, little cross peak intensity was observed between the gemini and the zwitterionic surfactant at low micellar compositions of the zwittergent. The results suggest some micelle demixing is occurring between the gemini and the zwittergent certain micellar composition ranges, a phenomenon rarely associated with hydrocarbon surfactants.
Journal of Surfactants and Detergents, 2020
The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been... more The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/ glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via 13 C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two-dimensional diffusion-oriented spectroscopy (2D-DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self-assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
Presence of NaC decreases the size of long CTAT micelle whereas NaDC increases. Highlights The ... more Presence of NaC decreases the size of long CTAT micelle whereas NaDC increases. Highlights The microstructure of CTAT micelles gets altered by bile salts. NaC transforms worm-like CTAT micelles into small spherical mixed micelles. Presence of NaDC decrease CTAT micelle curvature and increases micelle size.
Journal of Solution Chemistry, 1994
Solution properties of aqueous mixtures of the homologous series of polyoxyethene glycol mono-n-b... more Solution properties of aqueous mixtures of the homologous series of polyoxyethene glycol mono-n-butyl ethers C4H9O(CH2CH2O)m H (where m=1 to 3) have been investigated using surface tension, density, viscosity and13C NMR techniques. From the experimental data, excess volume and deviation of viscosity and free energy of activation of flow were evaluated and discussed in terms of the molecular interactions between the components. Surface activity of polyoxyethene glycol mono ethers in aqueous dilute solutions was evident from surface tension measurements. Thermodynamic properties of adsorption and apparent micellization or critical aggregation concentration (CAC) in these systems were evaluated and discussed. The CAC values and the aggregation numbers obtained from13C NMR chemical shift data indicate an increase in hydrophobicity with an increase in the value of m, in the polyoxyethene glycol mono-n-butyl ethers, and also agrees with the results obtained from surface tension measurements.
RSC Advances, 2020
Micelle formation enthalpies (D mic H values) have been calorimetrically determined at 298 K for ... more Micelle formation enthalpies (D mic H values) have been calorimetrically determined at 298 K for three sets of mixed zwitterionic/cationic gemini systems consisting of N-dodecyl-N,N-dimethyl-3-ammonio-1propanesulfonate (ZW3-12) and a series of structurally related gemini surfactants, the N,N'bis(dimethyldodecyl)-a,u-alkanediammonium dibromide (12-s-12) systems. From the experimental and the estimated ideal micelle formation enthalpies, the excess enthalpies were obtained. The degrees of nonideality of the interaction in the mixed micelle (b m) from our previous work was used along with the excess enthalpy values to determine excess thermodynamic quantities of the surfactants in the mixed system according to Regular Solution Theory (RST) and Motomura's theory. The excess enthalpies for the ZW3-12/12-4-12 were positive in magnitude and rose sharply when small amounts of the zwittergent were distributed into the gemini micelles. The excess enthalpies for the ZW3-12/12-5-12 and the ZW3-12/12-6-12 systems were also >0 kJ mol À1 , and as a function of zwittergent composition, were quite different to those of the ZW3-12/12-4-12 mixed micelles. These results indicate that the heat of mixed micelle formation is strongly dependent on electrostatic interactions and the structure of the surfactants involved, specifically, the length of the tether group for the 12-s-12 gemini surfactants. From the calorimetric data and the application of RST and Motomura's theory, we have obtained estimates of the excess Gibbs energy and entropy of mixing. An analysis of the three thermodynamic properties suggests that the relative contributions of enthalpic and entropic effects to nonideal behavior for mixed micelles involving gemini surfactants are strongly dependent on the gemini structure.
La presente invention concerne une composition tensioactive, ses applications et une methode de f... more La presente invention concerne une composition tensioactive, ses applications et une methode de fabrication de ladite composition. La composition tensioactive comprend au moins deux tensioactifs anioniques et au moins un tensioactif cationique. La composition tensioactive peut par exemple etre employee dans des produits de nettoyage et/ou des produits de soins personnels.
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Papers by Gerrard Marangoni