Aqueous DMSO Solution Research Articles

Magnetic, epr and SOD studies of some Cu II–Cu II, Cu II–Ni II and Cu II–Zn II imidazolate bridged complexes

Magnetic, spectroscopic and superoxide dismutase activity of imidazolate bridged [(Salala)Cu–Im–Cu(Salala)]Na, [(Salala)Cu–Im–Zn(Salala)]Na and [(Salala)Cu–Im–Ni(Salala)]Na (Salala=Salicyledenealiniate, Im=Imdiazolate) are described. The epr and electronic spectra of related mononuclear complexes, viz., [(Salala)Cu–OH 2] and [(Salala)Cu–ImH] also described. Appearance of a half-field signal in polycrystalline and decrease in μ eff per copper(II) ion indicate super exchange coupling between copper(II) ion in [(Salala)Cu–Im–Cu(Salala)]Na binuclear complex. A pH-dependent epr and UV–vis study of 50% aqueous DMSO solution of binuclear complexes suggest that the complexes are stable in narrow pH range.

Detection of water–polar solvent interaction using melting of a eutectic

We focused on the eutectics of water and a lower alcohol or polar solvent, and investigated the relationship between the change in the solution structure and the melting peak of the eutectic in aqueous solutions of ethanol, propanol or DMSO. We found that the melting temperature and melting enthalpy of 0.05 alcohol molar fraction solutions were almost constant regardless of ultrasonic treatment, while the melting enthalpy of 0.10 alcohol molar fraction solutions fell to 81% (ethanol) and 46% (1-propanol) of the pretreatment value. The melting enthalpy of the eutectic of a polar solvent and water may be reduced by ultrasonic treatment in the liquid state. These results agree with the data from 17 O NMR of water and the absorption peak at 1150 nm for free water. These results show that water–polar solvent interaction can be detected by examining the melting of a eutectic of a polar solvent and water using sensitive DSC.

Poly(ethylene oxide) Gel Based Dimexide Ointment

Dimexide (dimethyl sulfoxide, DMSO), approved for medical applications since 1971, is used for the treatment of contusions, strained muscles, edemas of various etiology, lymphostasis, burns, phlegmons, hemarthrosis, acute and chronic thrombophlebitis, erysepilatous inflammations, eczemas, diffuse streptoderma, and other disorders. The main medicinal form of dimexide administration are applications and compresses using 30 – 70% aqueous DMSO solutions (most frequently, 50% solution) [1 – 3]. However, this form is rather inconvenient since a patient has to prepare the solution at home. Another disadvantage is a pronounced specific odor sometimes complicating use of DMSO solutions. Despite the broad range of indications for administration and the wide experience gained on using DMSO in practice, optimum medicinal forms of dimexide have yet to be developed. Creation of an ointment containing 50% DMSO is a complicated task because a base with such a high content of this liquid is difficult to densify. Another problem is related to the fact that DMSO is a strong penetrant facilitating absorption of the base components through the skin. This property of DMSO excludes using hydrocarbon bases for preparation of DMSO ointments because the absorption of hydrocarbons and other lipophilic ointment-forming components detrimentally affects the gas exchange and water metabolism in the skin. Therefore, dimexide ointments should be developed using hydrophilic water-soluble polymer-based components. A promising modern medicinal form of dimexide is offered by analgesic and antiinflammatory gel preparations [4]. Such gels are prepared based on gelatin, poly(vinyl pyrrolidone) (PVP), or starch and additionally contain taurine. We have prepared a series of dimexide gels according to recommendations [4]. It was found that some characteristics of the preparations (appearance, colloidal stability, rheological properties) do not meet the pharmacopoeial requirements. The gels appear as viscous liquids, exhibit strong characteristic odor, and seem “greasy” to the touch. The ointments exhibit separation into layers on standing and cannot be strictly classified as gels due to unsatisfactory elastic-plastic behavior. In contrast, a gel prepared on carbopol base [5] possess valuable organoleptic properties, an attractive appearance, and good spreading capacity owing to the pronounced elastic-plastic properties. This gel is stable on storage, but still has a pronounced odor and was “greasy” to the touch. The purpose of this study was to create a ready-to-use medicinal form – a dimexide ointment – with a DMSO content in the range from 30.0 to 70.0% using bases not containing hydrocarbons (paraffin, vaseline, vaseline oil) and free of the aforementioned disadvantages (odor and “greasy” feel). The work was performed in cooperation with specialists of the Pyatigorsk Pharmaceutical Plant.

Visual Sensing of Saccharides Promoted by Resorcinol Condensation Products

[structure: see text] Heating aqueous DMSO solutions of five saccharides in the presence of 1-3 reveals that each receptor promotes solution colors characteristic for each sugar. New compound 3 allows the direct correlation of sugar concentration with visible region absorbance and/or fluorescence intensities.

Synthesis, structure and magnetic behavior of a di-μ-chloro-di-μ-imidazolato-tetracopper(II) complex with two dinucleating macrocycles

The synthesis, crystal structure and magnetic behavior of the di-μ-chloro-di-μ-imidazolato-tetracopper(II) complex [L 2Cu 4(Im) 2Cl 2](ClO 4) 4(CH 3OH), where Im is imidazole and L is 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1 11,13]triaconta-1(29),11(30),12,14,25(26),27-hexaene, have been studied. X-ray structure analysis shows that the compound crystallizes in monoclinic and space group P2(1)/ c, with a=13.716(3), b=11.165(2), c=27.340(6) Å, β=98.43(3)° and Z=2. The cation consists of two imidazolate bridged dicopper(II) centers encapsulated within two macrocycles, respectively, which are linked by a pair of chloride atoms. In each imidazolate bridged dicopper(II) center, both copper atoms are five-coordinated by four basal nitrogen atoms (three from the macrocycle and one from the imidazolate) and one axial chloride atom shared with another copper atom in the other imidazolate bridged dicopper(II) center in the molecule. pH-dependent ESR studies of the title complex in frozen 50% aqueous DMSO solution show that the bridged cation [LCu 2(Im)] 3+ exists as a major species in solution over the range 7.00≤pH≤11.5, and the μ-Im bridge is broken in the pH range of 7.00–5.20. The molar conductance of the title complex indicates that the μ-Cl bridge is almost entirely dissociated when dissolved in 1:1 DMSO aqueous solution. However, when Cl − ions were gradually added to the solution, a complex with a CuN 4Cl chromophore was successively formed. Magnetic measurement studies on the powder sample reveal that antiferromagnetic interactions are mediated through both μ-Im ( J 1=−26.78 cm −1) and μ-Cl ( J 2=−9.52 cm −1) bridges.

The synthesis, structure and SOD-like behaviors of a μ-imidazolato-dicopper(II) complex with a binucleating hexaazamacrocycle

The synthesis, crystal structure and magnetic properties of the imidazolate-bridged dinuclear copper(II) complex [LCu 2(Im)(DMSO) 2](ClO 4) 3(DMSO), where ImH is imidazole, and L is 3, 6, 9, 17, 20, 23-hexaazatricyclo[23.3.1.1 11,13]triaconta-1(29), 11(30), 12, 14, 25(26), 27-hexaene, have been studied. Single crystal X-ray diffraction determination reveals the distorted tetragonal pyramid geometries of the imidazolate bridged dicopper(II) center are incorporated within the binucleating macrocycle. Both copper atoms are five-coordinated by four basal nitrogen atoms (three from the macrocycle and one from the imidazolate) and one oxygen atom from the DMSO molecule. Two coordinated DMSO molecules are situated at the same side of the macrocycle. The Cu–Cu separation in the complex is 5.93 Å. Magnetic measurements and ESR spectroscopy studies exibit an antiferromagnetic exchange interaction with a coupling constant of J= − 26.94 cm −1. Investigations on the pH-dependent ESR of the title compound in frozen 50% aqueous DMSO solution confirm the existence of the bridged cation [LCu 2(Im)] 3+ as a major species in solution mainly in the range 5.2⩽pH⩽11.5. The imidazolate bridge is broken in the pH range of 5.2–3.3, which is close to that for the native enzyme.

Thermodynamic factors controlling the interaction of quinoline antimalarial drugs with ferriprotoporphyrin IX

The interaction of a variety of quinoline antimalarial drugs as well as other quinoline derivatives with strictly monomeric ferriprotoporphyrin IX [Fe(III)PPIX] has been investigated in 40% aqueous DMSO solution. At an apparent pH of 7.5 and 25°C, log K values for bonding are 5.52 ± 0.03 (chloroquine), 5.39 ± 0.04 (amodiaquine), 4.10 ± 0.02 (quinine), 4.04 ± 0.03 (9-epiquinine), and 3.90 ± 0.08 (mefloquine). Primaquine, 8-hydroxyquinoline, 5-aminoquinoline, 6-aminoquinoline, 8-aminoquinoline, and quinoline exhibit no evidence of interaction with Fe(III)PPIX. The enthalpy and entropy changes for the interaction of quinolines with Fe(III)PPIX, as determined from the temperature dependence of the log K values, exhibit a compensation phenomenon that is suggestive of hydrophobic interaction. This is supported by the finding that the interactions of chloroquine and quinine with Fe(III)PPIX are weakened by increasing concentrations of acetonitrile. Interactions of chloroquine, quinine, and 9-epiquinine with Fe(III)PPIX are shown to remain strong at pH 5.6, the approximate pH of the food vacuole of the malaria parasite which is believed to be the locus of drug activity. Implications for the design of antimalarial drugs are briefly discussed.

`Intermolecular interactions' in aqueous solutions of three components including lysozyme

Excess partial molar enthalpies were measured in ternary aqueous solutions, tert-butyl alcohol (TBA)-DMSO-H 2O, and lysozyme (L)–alcohols (A)–H 2O. The solute–solute interactions were evaluated as the derivatives of these data with respect to the mole fraction of a solute. In the water-rich region, where the so-called mixing scheme I is operating in binary aqueous solutions of TBA, DMSO or alcohols, two solutes in TBA–DMSO–H 2O seem to modify the hydrogen bond network of H 2O in an additive manner. Here, mixing scheme I refers to the way in which a solute (hydrophobic) modifies the molecular organization of H 2O. Specifically, a solute enhances the hydrogen bond strength of H 2O in its immediate vicinity. On the other hand, the probability of hydrogen bond in the bulk away from a solute is reduced, and it is still high enough, however, to keep the hydrogen bond network connected throughout the entire macroscopic system. As the composition of solute increases, the hydrogen bond probability in the bulk decreases to the point at which the macroscopic bond connectivity is no longer possible. At this point, a new mixing scheme, II, sets in. For L–A–H 2O mixtures at infinite dilution of L, the L–A interaction changes drastically from repulsive to attractive at the boundary between I and II for binary aqueous alcohols. Moreover, a denatured lysozyme interacts with alcohols more strongly than the native form, and is more repulsive in mixing scheme I and more attractive in II. This behaviour is shown to be consistent with the alcohol-dependent enthalpy of denaturation of lysozyme found by Velicelebi and Sturtevant [Velicelebi and Sturtevant, Biochem. 18 (1979) 1180–86].

Molecular characterization of starch by SEC: dependance of the performances on the amylopectin content

The solubility of starch samples with different amylose/amylopectin ratios was investigated in NaOH and aqueous DMSO solutions. The decrease in solubility when the amylopectin content increases was clearly demonstrated. SEC experiments were performed using KOH 0.001 n as it was found to be better than the other aqueous solvents investigated. Even when the sample solubility was found to be high, SEC experiments showed the occurrence of some aggregation as a result of the retrogradation process. This phenomenon is undesirable for quantitative use of SEC and could not be diminished by the use of various additives. This paper demonstrates that no aqueous solvent tested is suitable for characterizing starch amylopectin and that the use of this technique has to be limited to the characterization of the amylose component of starch.

Thermochemistry of copper(II) ion solvation in aqueous organic solvents

Abstract The integral heat effects of CuCl2 dissolution in aqueous DMSO, aqueous ethanol and aqueous acetone solutions at 298. 15 K in the electrolyte concentration range 0.001–0.01M were measured by means of calorimetry. ΔH sol 0 values were obtained by extrapolation to zero electrolyte concentration. Literature data were used to determine the thermodynamic characteristics of Cu2+ transfer from water to aqueous organic solvents.

Solvent and substituent effects on the redox properties of free-base tetraphenylporphyrins in DMSO and aqueous DMSO

Oxidation and reduction potentials have been measured by voltammetry for a series of substituted tetraphenylporphyrins in DMSO and aqueous DMSO solutions. Hammett substitutent effect correlations effectively describe the positions of the first and second reduction waves; more electron-withdrawing substituents shift the reduction waves to more positive potentials with reaction constants ([rho][prime]) of +60 and +57 mV, respectively. The oxidation potentials show a similar trend ([rho][prime] = +63 mV); however, a sharp break is observed for highly electron-donating substituents such as alkoxy and amino ([rho][prime] = +390 mV). We propose that these latter porphyrins undergo oxidation at the benzene ring rather than the porphyrin ring. Sovent effects are correlated by the E[sub T](30) solvent parameter, with the more highly polar solvent (more aqueous DMSO) shifting the reduction potentials to more positive values. 25 refs., 6 figs., 1 tab.

Detection of Organic Compounds by Dual Fluorescence of Bis(1-pyrenecarbonyl)-γ-cyclodextrins

Abstract The regioisomers of 6A,6X-bis(1-pyrenecarbonyl)-γ-cyclodextrins (1-4) showed dual fluorescence composed of normal and excimer emissions in 30% aqueous DMSO solution. The fluorescence spectra of 1-4 were different from one another and varied upon guest addition in different manners depending on both host and guest. The guest-induced increases or decreases in the excimer emission intensity were used for detecting various organic compounds.

Studies of the thermokinetics of second-order reactions

A dimensionless parameter method used for studies of the thermokinetics of second-order reactions, with which the rate constant of reaction can be calculated from the thermogram's data without using the apparatus constants of the calorimeter, is proposed in this paper. The saponification of ethyl benzoate in aqueous alcohol and the nucleophilic substitution of benzyl chloride in aqueous DMSO solution have been studied. The rate constants calculated with this method are in fair agreement with that given in the literature.

ChemInform Abstract: The Effect of Environmental Rigidity on Nonradiative Decay in Chromium(III) Amines.

Abstract The lifetimes of Cr(NH 3 ) 6 3+ and the Cr(cyclam)(NH 3 ) 2 + complexes, both protiated and deuterated, have been recorded in aqueous polyalcoholic and DMSO solutions in the temperature range that includes the change from a rigid glass to a fluid. A small but distinct lifetime reduction is associated with increased solvent mobility in the protiated species but not in the deuterated complex. This is interpreted to indicate that increasing anharmonicity in accepting modes enhances the nonradiative rates.

The effect of environmental rigidity on nonradiative decay in chromium(III) amines

The lifetimes of Cr(NH 3) 6 3+ and the Cr(cyclam)(NH 3) 2 + complexes, both protiated and deuterated, have been recorded in aqueous polyalcoholic and DMSO solutions in the temperature range that includes the change from a rigid glass to a fluid. A small but distinct lifetime reduction is associated with increased solvent mobility in the protiated species but not in the deuterated complex. This is interpreted to indicate that increasing anharmonicity in accepting modes enhances the nonradiative rates.

Conformational behaviors of N-substituted N-lauroylglycinates in aqueous micellar and DMSO solutions and their Krafft points

The 13C and 1H NMR spectra of N-lauroylglycines and/or their sodium salts substituted at the peptide nitrogen atom, CH 3(CH 2) 10CON( X)CH 2COOH/or Na; X =H, CH 3, CH 2CH 3, (CH 2) 2CH 3, (CH 2) 3CH 3, (CH 2) 2OH, and (CH 2) 3OH, were measured in DMSO- d 6 and D 2O solutions. The existence of both cis and trans isomeric forms of peptide groups was observed for all the surfactant samples except N-lauroylglycine ( X =H) and its sodium salt, which were present only in the trans conformation. The population of the trans isomer in DMSO- d 6 solutions decreases monotonously as the alkyl chain length of N-substituent becomes longer. It is interesting to note that the population of the trans isomer in aqueous micellar solutions decreases with the increasing chain length of N-hydroxyalkyl groups but unexpectedly increases with the size of N-substituent in the case of N-alkyl groups. The conformational behaviors of these surfactant molecules in the micellar aggregates may be explained in terms of the steric and hydrophobic interactions between the N-substituted groups and the long N-acyl chain. The Krafft points of the calcium salts of surfactants were found to be markedly depressed with increasing chain length in N-substituted groups. Sodium N-hydroxypropyl- N-lauroylglycinate especially shows the Krafft point to be lower than 0°C even in hard water and is useful as a surfactant, being applicable in hard and/or cold water.

Influence of dimethyl sulfoxide on freezing resistance of lettuce seeds

DTA of lettuce seeds was used to study the cryoprotective mode of action of DMSO. Lettuce seeds were imbibed for 16 hr in 5, 10, 15 or 20% aqueous solutions of DMSO either with or without a 6 hr preimbibition in water. Seeds were frozen to postsecondary exotherm temperatures; exotherms were recorded; and germination was tested after freezing. DMSO had at least a twofold effect on the lettuce seeds: it increased the degree of supercooling, and it imparted a capacity to survive following freezing beyond secondary exotherm levels.

Studies related to antitumor antibiotics. Part XXIV. High field 1H nmr analysis and conformations of saframycins A and C

A detailed analysis of the high field (400 MHz) 1H nmr spectra of the basic antitumor antibiotics saframycin A and C in CDCl3, C6D6, and in aqueous DMSO solutions has been carried out. Selective double irradiation experiments permitted the unambiguous assignment of all the proton chemical shifts and coupling constants. Consideration of the magnitudes of the latter together with specific nOe experiments permits assignment of molecular geometry and average conformations in solution. Selective shifts occurring in DMSO–D2O solutions upon addition of CF3COOD identified the 12-N atom as the site of protonation which result bears directly on the acid promoted binding of these antibiotics to DNA templates as part of their cytotoxic action.

Studies on formaldehyde resins, 18. Kinetics of acid‐catalyzed hydrolysis of bis(hydroxymethyl)melamine

AbstractKinetics and mechanism of the acid‐catalyzed hydrolysis of N,N′‐bis(hydroxymethyl)melamine [6‐amino‐2,4‐bis(hydroxymethylamino)‐1,3,5‐triazine] (M2F) were studied in the pH region of 0,5 − 7,6 at 30°C, where 30 vol.‐% DMSO aqueous solution was used as a solvent. The main results are as follows. The hydrolysis of M2F was of ca. 1,5th order in [M2F]0 at constant pH of 2,7 − 7,6, and was of ca. 1st order in the strongly acidic region of pH 0,5 − 1,0. Moreover, the hydrolysis rate of M2F attained a maximum at pH 4,0 corresponding to [HCl]0/[M2F]0 = 0,5 and a minimum at pH 1,9. On the basis of these results and kinetic investigations, the main reaction of the hydrolysis of M2F is plausible to be a reaction of the conjugate acid of M2F with a M2F molecule in the acidic range of pH > 2,7.

Studies on protein semisynthesis. I. Formation of esters, hydrazides, and substituted hydrazides of peptides by the reverse reaction of trypsin.

An enzymatic method for converting tryptic peptides into their intermediates for the azide method of peptide synthesis was investigated by using model substrates, Bz-Arg, Bz-Gly-Arg, and Bz-Gly-Lys. The conditions favorite for the formation of the esters, hydrazides, and substituted hydrazides were deduced from the theoretical analysis on the pH and pKa dependence of the synthetic reactions and the pKa values of the substrates in various solvents. The theory based on the empirical relationship between the pKa of amines and the formation constant of the amides (Fersht, A.R. & Requena, Y. (1971) J. Am. Chem. Soc. 93, 3499-3504) indicates that the most favorite amine in the formation of amides is the one with a pKa value equal to the pKa of the carboxyl group and with such amines the amide formation takes place almost quantitatively even in aqueous solutions. Boc- and Cbz-hydrazine were found to satisfy the above condition approximately. The methyl esters of the substrates were formed in 30-35% yields in 50% aqueous methanol at pH near 4.5 by the reverse reaction of trypsin [EC 3.4.4.4]. Bz-Gly-Arg-NHNH2 was formed in a 34% yield in 2 M aqueous hydrazine and in 70-80% yields in 50% aqueous solutions of dioxane, DMF, and DMSO containing 1 M hydrazine at pH near 7. Bz-Gly-Arg-NHNH-Boc and Bz-Gly-Lys-NHNH-Boc were formed quite readily in 90-98% yields in H2O and in 50% aqueous solutions of dioxane, DMF, and DMSO containing 0.5 or 1 M Boc hydrazine at pH from 4 to 5. The Cbz-hydrazides of the peptides were also formed readily in 88-95% yields in the above mixed solvents containing 0.5 M Cbz-hydrazine. The formation constants of the hydrazides in H2O were in good agreement with those predicted by the empirical relationship. The formation constants in the form of log Ke in the mixed solvents calculated by taking the activity coefficients of the reactants as unity were 0.1 to 0.5 lower than the predicted values.