Optical rotation of some α-1,4-linked glucopyranosides in the system H2O–DMSO and solution conformation of amylose

The specific rotation of starch components, corrected for refractive index variation, exhibits a discontinuity in the region of the water–dimethyl sulfoxide (H₂O–DMSO) system that corresponds to the composition of the complex 2H₂O–DMSO. This discontinuity is a property dependent upon the presence of a number of consecutively linked α-1,4 glucose units and, therefore, must reflect a change in symmetry of a segment, of polymer chain. The optical rotation of amylose between 26.5 and 92.5°C. does not change in DMSO and is only slightly lowered in water at the higher temperature. The behavior of amylose in both DMSO and H₂O is like that of a random coil, as indicated by viscosity and sedimentation measurements. These results may be interpreted either as being compatible with models of amylose in solution in which the polymer backbone has helical twist, or as indicating removal of strong interactions between polymer chain segments by a good solvent.     

X-Ray diffraction of ethylenediamine–amylose complex

Solutions of amylose in ethylenediamine yield a crystalline film complex upon evaporation of solvent. The x-ray analysis indicates the presence of a tetragonal-shaped cell with a symmetry approximating that of space group P2₁2₁2₁. The amylose sixfold helix has a diameter of 13.3 Å and a translation period of 8.0Å. Chemical and physical analyses support a complexing ratio of one ethylenediamine molecule to every two glucose units. The structure is nearly identical to any amylose–dimethyl sulfoxide complex previously examined. The square mode of packing arrangement appears to result from complexation between amylose chains. Such complexing indicates a much greater degree of amylose interaction than is observed in amylose complex structures having a hexagonal close-packing arrangement.     

Amylose conformational transitions in binary DMSO/water mixtures

The effects on amylose conformation of percentage water in dimethyl sulfoxide (DMSO)/water mixtures were measured by following changes in specific optical rotation, limiting viscosity number, and ¹³C-NMR chemical shifts. The temperature dependence of specific optical rotation showed differences in amylose conformation at four chosen ratios of dimethyl sulfoxide/water. An amylose conformational change was also deduced from ¹³C-NMR chemical shift data. Changes in limiting viscosity of amylose in different proportions of DMSO/water, and the effect of tetramethylurea on the specific rotation of amylose, indicate that intramolecular hydrogen bonding decreases with increased water content. 66.6% DMSO appears to be a crossover concentration, below which the helical conformation is progressively lost as water is added. When water content is over 60%, transition to a conformation which allows iodine complexation to take place is complete. A transition of amylose conformation from helix to loose helix to random coil with increasing water content was deduced from the experimental results.     

Crystal and molecular structure of the amylose–DMSO complex

The crystal and molecular structure of the complex of amylose with dimethyl sulfoxide has been studied by a combination of stereochemical analysis, potential energy, and X-ray diffraction methods. The complex crystallizes in a pseudotetragonal unit cell with a = b = 19.17 Å and c (fiber axis) = 24.39 Å, with two antiparallel chains per unit cell and space group P2₁2₁2₁. The amylose chain is a left-handed 6₁(1.355) helix with three turns per crystallographic repeat. The O(6) rotational position is approximately gt. Dimethyl sulfoxide is located inside the helix with one DMSO molecule for every three glucose residues. An additional four DMSO molecules and eight water molecules each are located in the large interstices between chains, and it is the interaction of these molecules with the helix that results in the pseudotetragonal chain packing. The interstitial DMSO is the source of the previously reported additional layer lines, which are not consistent with the 8.13-Å amylose repeat distance. The final R factor for the layers with amylose contribution to the structure factors was 0.29, while the overall R factor was 0.35. The stereochemical packing analysis provided suitable phasing models for the subsequent X-ray refinement.     

Stabilization of Li Metal Anode in DMSO‐Based Electrolytes via Optimization of Salt–Solvent Coordination for Li–O2 Batteries

The conventional electrolyte of 1 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethyl sulfoxide (DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li–O₂ batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li–O₂ batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI^?)_a ? Li⁺? (DMSO)_b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition, such salt–solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon‐based air electrodes has been greatly enhanced, resulting in improved cycling performance of Li–O₂ batteries. The fundamental stability of the electrolyte in the absence of free‐solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems.     

The effect of dimethyl sulfoxide on the enantioselectivity in the pig liver esterase catalyzed hydrolysis of dialkylated propanedioic acid dimethyl esters

The effect of dimethyl sulfoxide (DMSO) on the enantioselectivity in the pig liver esterase (EC 3.1.1.1) catalyzed hydrolysis of dialkylated propanedioic acid diesters was studied. Increasing concentrations of DMSO increased the ratio of the (R)-enantiomers of the produced monoesters. This effect was not due to the change in pH_app caused by the solvent. The reaction rate was lowered to one-tenth of the rate without DMSO when the DMSO concentration was increased to 50%.     

A V7 conformation of dimethyl sulfoxide-amylose complex

X-ray investigation of a crystalline complex between dimethyl sulfoxide (DMSO) and amylose indicates a sevenfold helical structure having an orthogonal unit cell: a = 30.23 Å, b = 28.18 Å, and C = 7.91 Å (helix axis). This helical amylose results from precipitation of amylose in DMSO solutions under suitably dry conditions using toluene as a precipitating agent. Analyses show a molar ratio of 0.95:2:0.4:0.08 for DMSO, amylose glucose units, water, and toluene, respectively. DMSO and amylose combine in at least two crystalline conformations, sixfold and sevenfold helices. The amount of water present influences the resulting conformation. The existence of the sevenfold helical solid indicates that the amylose sevenfold helix has greater stability than previously recognized by conformational energy calculations. In general, potential energy calculations cannot be correct that ignore the influence of guest molecules and their effects upon the maltose residue conformation and that lead to a sixfold helix as the most probable structure.     

The beta-galactosidase-catalyzed hydrolysis of o-nitrophenol-beta-D-galactoside at subzero temperatures: evidence for a galactosyl-enzyme intermediate.

The reaction of β-galactosidase ($\text{E. coli}$ K12) with $\text{o}$-nitrophenyl-β-$\text{D}$-galactoside has been investigated over the temperature range +25° to ?30° using 50% aqueous dimethyl sulfoxide as solvent. At temperatures below ?10° turnover becomes very slow and a burst of $\text{o}$-nitrophenol is observed. Such a burst indicates the existence of a galactosyl-enzyme intermediate whose breakdown is rate-limiting and provides a means of determining the active site normality. The Arrhenius plot for turnover is linear in the ?25 to +25° range with E_a = 26 ± 3 kcal/mole. The presence of the 50% DMSO had no effect on K_m but caused a small decrease in K_cat.     

Vibrational circular dichroism of polypeptides. VI. Polytyrosine alpha-helical and random-coil results

We have measured the VCD of polytyrosine in the amide I and II regions in dimethyl sulfoxide (DMSO) and in 80:20 mixtures of DMSO with trifluoroethanol, trifluoroacetic acid (TFA), and dichloroacetic acid and in 50:50 mixtures of DMSO and trimethyl phosphate (TMP). Additionally, VCD was obtained for deuterated polytyrosine in DMSO and DMSO:D₂O, DMSO:TFA(d₁), and DMSO:TMP mixtures as before. Amide A VCD was obtained in DMSO and DMSO:TMP mixtures. In the pure solvent, VCD of an opposite sign was seen as compared with that seen in the mixtures. The latter were characteristic in sign pattern and shape of right-handed α-helices for poly(L -tyrosine). The pure polytyrosine:DMSO results are similar to those of polylysine:D₂O at neutral pH and poly(β-benzyl-aspartate) in DMSO and may be characteristic of random-coil VCD.     

The LiCl effect on the conformation of lentinan in DMSO

Lentinan (β‐(1→3)‐D ‐glucan) was found to be successfully fractionated by the mixture of dimethyl sulfoxide (DMSO) and lithium chloride (LiCl) as a solvent and acetone as a precipitant. Light scattering and viscosity measurements were made on solutions of fractionated samples in pure DMSO and 0.2M LiCl/DMSO in the range of the molecular weight M_w from 21.7 × 10⁴ to 84.7 × 10⁴. The values of M_w in both solvents were almost the same, but the remarkable difference between the values of intrinsic viscosity [η] demonstrated that the LiCl/DMSO solvent greatly enhances the stiffness of the lentinan backbone. The observed intrinsic viscosity [η] was analyzed by the Yoshizaki‐Nitta‐Yamakawa theory of a worm‐like chain, and the persistence length q and molecular weight per unit contour length M_L were determined roughly as 6.0 nm and 890 g nm^?1 in 0.2M LiCl/DMSO, and 5.1 nm and 890 g nm^?1 in pure DMSO, respectively. This slightly larger persistent length in 0.2M LiCl/DMSO also confirmed the higher stiffness of lentinan enhanced by the LiCl/DMSO solvent. The enhancement of the chain stiffness was ascribed to the electrostatic repulsion because of the hydrogen bonding of the hydroxyl protons of lentinan with the chloride ion, which is in turn associated with the Li⁺(DMSO)_n macrocation complex. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 840–845, 2012.     

Denaturation of RNA with dimethyl sulfoxide

The denaturation of single-stranded and double-stranded RNA's in solutions with varying proportions of dimethyl sulfoxide has been followed by changes in absorbancy, optical rotation, and—with a double-stranded form of bacteriophage of MS2 RNA— infectivity for bacterial spheroplasts. By these criteria the RNA's studied, including the synthetic polynucleotide rG:rC, are completely denatured at room temperature in high concentrations of this solvent. In lower concentrations, the T_m of the RNA preparation is decreased only slightly as the dimethyl sulfoxide concentration is raised until a critical concentration is reached. The T_m falls sharply with small further increases in dimethyl sulfoxide concentration. Sedimentation studies can be conducted directly in these media. The determination of sedimentation velocity in 99% dimethyl sulfoxide containing 0.001M EDTA provides a reliable estimate of RNA molecular weights.     

Electron donors and the quinone involved in dimethyl sulfoxide reduction inEscherichia coli

Escherichia coli can use dimethyl sulfoxide (DMSO) as an electron acceptor during anaerobic growth on the oxidizable substrate, glycerol. During growth, the DMSO is reduced to dimethyl sulfide (DMS). For the reduction of DMSO, NADH, formate, lactate, reduced benzyl viologen, reduced methyl viologen, and dithionite can serve as electron donors. The terminal reductase and the dehydrogenases linking the various electron donors to the electron transport chain were found to be membrane bound. Chlorate-resistant mutants (chl) were unable to grow and reduce DMSO. However, in the case of thechlD mutant, growth and DMSO reduction can be restored by growth in the presence of high concentrations of molybdate. Mutants ofE. coli blocked in menaquinone (vitamin K₂) biosynthesis—menB, menC, andmenD—were unable to grow with DMSO as an electron acceptor, even though the terminal reductase is present in these mutants. Both growth and DMSO reduction could be restored in these mutants by growth in the presence of the menaquinone intermediates,o-succinylbenzoate and 1,4-dihydroxy-2-naphthoate, depending on the metabolic block of the mutant. Thus menaquinone is involved in electron transport during DMSO reduction.     

Evidence for a glucosyl-enzyme intermediate in the beta-glucosidase-catalyzed hydrolysis of p-nitrophenyl-beta-D-glucoside

The reaction of almond β-glucosidase with $\text{p}$-nitrophenyl-β-$\text{D}$-glucoside has been investigated over the temperature range +25° to ?45° using 50% aqueous dimethyl sulfoxide (DMSO) as solvent. At temperatures below those at which turnover occurs a “burst” of $\text{p}$-nitrophenol proportional to the enzyme concentration is observed. Such a “burst” suggests the existence of a glucosyl-enzyme intermediate whose breakdown is rate-limiting, and provides a method for measuring the active-site normality. At pH 5.9, 25°, the presence of 50% DMSO causes an increase in K_m from 1.7×10^?3M (0%) to 1.7×10^?2M, whereas V_max is unchanged. The DMSO thus apparently acts as a competitive inhibitor with K_i = 0.7M. The Arrhenius plot for turnover is linear over the accessible temperature range with E_a = 23.0 ± 2.0 kcal/mole.     

Synthesis of a highly fluorescent N,N‐dimethyl benzylamine–palladium(II) curcuminate complex and its application for determination of trace amounts of water in organic solvents

In this work a new highly fluorescent N,N‐dimethyl benzylamine–palladium(II) yu complex was synthesized by the reaction of [Pd₂{(C,N–C₆H₄CH₂N(CH₃)₂}₂(μ‐OAc)]₂] with curcumin. The structure of the synthesized complex was characterized using Fourier transform infra‐red (FT‐IR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy, and elemental analysis. Fluorescence quantum yield (Φ_F) values of the synthesized complex in dimethyl sulfoxide (DMSO), acetonitrile, ethanol, and methanol were 0.160, 0.104, 0.068, and 0.061, respectively. The fluorescence signal of the complex in the organic solvents was very sensitive to the water content of the organic solvent. The quenching effect of water was used to determine trace amounts of water in the heteroatom‐containing organic solvents (ethanol, methanol, acetonitrile) and redox‐active solvents (DMSO). The linear ranges for determination of water (v/v %) in ethanol, DMSO and acetonitrile were found to be 0.03–14.5, 0.08–13.8, and 0.07–18.8, respectively. Two linear ranges were found for determination of water (v/v %) in methanol (0.1–1.2 and 4.7–25.0). Detection limit (DL) values were calculated to be 0.001, 0.05, 0.004, and 0.01 (v/v %) in ethanol, methanol, acetonitrile, and DMSO, respectively. The proposed method overcomes the problems of the standard Karl Fischer method for determination of water in DMSO. In addition, it gave the best DL value for determination of water in ethanol compared with all published papers to date.     

Why are dimethyl sulfoxide and dimethyl sulfone such good solvents?

We have carried out B3PW91 and MP2-FC computational studies of dimethyl sulfoxide, (CH₃)₂SO, and dimethyl sulfone, (CH₃)₂SO₂. The objective was to establish quantitatively the basis for their high polarities and boiling points, and their strong solvent powers for a variety of solutes. Natural bond order analyses show that the sulfur–oxygen linkages are not double bonds, as widely believed, but rather are coordinate covalent single S⁺→O⁻ bonds. The calculated electrostatic potentials on the molecular surfaces reveal several strongly positive and negative sites (the former including σ-holes on the sulfurs) through which a variety of simultaneous intermolecular electrostatic interactions can occur. A series of examples is given. In terms of these features the striking properties of dimethyl sulfoxide and dimethyl sulfone, their large dipole moments and dielectric constants, their high boiling points and why they are such good solvents, can readily be understood. Figure Dimers of dimethyl sulfoxide (DMSO; left) and dimethyl sulfone (DMSO2; right) showing O S—O -hole bonding and C H—O hydrogen bonding. Sulfur atoms are yellow, oxygens are red, carbons are gray and hydrogens are white     

Proton translocation coupled to dimethyl sulfoxide reduction in anaerobically grown Escherichia coli HB101.

Proton translocation coupled to dimethyl sulfoxide (DMSO) reduction was examined in Escherichia coli HB101 grown anaerobically on glycerol and DMSO. Rapid acidification of the medium was observed when an anaerobic suspension of cells, preincubated with glycerol, was pulsed with DMSO, methionine sulfoxide, nitrate, or trimethylamine N-oxide. The DMSO-induced acidification was sensitive to the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (60 microM) and was inhibited by the quinone analog 2-n-heptyl-4-hydroxy-quinoline-N-oxide (5.6 microM). Neither sodium azide nor potassium cyanide inhibited the DMSO response. An apparent----H+/2e- ratio of 2.9 was obtained for DMSO reduction with glycerol as the reductant. Formate and H2(g), but not lactate, could serve as alternate electron donors for DMSO reduction. Cells grown anaerobically on glycerol and fumarate displayed a similar response to pulses of DMSO, methionine sulfoxide, nitrate, and trimethylamine N-oxide with either glycerol or H2(g) as the electron donor. However, fumarate pulses did not result in acidification of the suspension medium. Proton translocation coupled to DMSO reduction was also demonstrated in membrane vesicles by fluorescence quenching. The addition of DMSO to hydrogen-saturated everted membrane vesicles resulted in a carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone-sensitive fluorescence quenching of quinacrine dihydrochloride. The data indicate that reduction of DMSO by E. coli is catalyzed by an anaerobic electron transport chain, resulting in the formation of a proton motive force.     

Conformation of amylose in aqueous solution: Optical rotatory dispersion and circular dichroism of amylose–iodine complexes and dependence on chain length of retrogradation of amylose

The dependence on chain length of two characteristic properties of amylose, i.e., retrogradation and complex formation with iodine, have been studied by using enzymatically synthesized, homodisperse amyloses. The association rates of amyloses in water containing 5% dimethyl sulfoxide have a sharp maximum at a degree of polymerization P?_n of 80; shorter and longer molecules are much more soluble. The iodine complexes of amylose exhibit a strong Cotton effect in the range of the long-wave absorption maximum (position depending on chain length) and two weaker Cotton effects at 480 and 350 nm. The long-wave Cotton effect is most intense at about P?_n 50 and decreases rapidly for shorter and longer chains. This behavior is unexpected and is not in accordance with the further increase of λ_max and λ_max. The experiments can best be interpreted by assuming well ordered, stiff chains in the low molecular weight range (P?_n 50–80). For longer chains, the findings are discussed in the light of current concepts of amylose conformation in aqueous solution, namely the model of the broken helical chain (alternating stiff helical segments and unordered regions) and the model of a flexible coil without a significant helical content. However, according to the results given in this paper, a wormlike helical chain seems to be the most adequate model for amylose conformation in neutral solution.     

Delineating the conformational dynamics of intermediate structures on the unfolding pathway of β-lactoglobulin in aqueous urea and dimethyl sulfoxide

Abstract

The funnel shaped energy landscape model of the protein folding suggests that progression of folding proceeds through multiple pathways, having the multiple intermediates which leads to multidimensional free-energy surface. Herein, we applied all-atom MD simulation to conduct a comparative study on the structure of β-lactoglobulin (β-LgA) in aqueous mixture of 8?M urea and 8?M dimethyl sulfoxide (DMSO), at different temperatures. The cumulative results of multiple simulations suggest a common unfolding pathway of β-LgA, occurred through the stable and meta-stable intermediates (I), in both urea and DMSO. However, the free-energy landscape (FEL) analyses show that the structural transitions of I-states are energetically different. In urea, FEL shows distinct ensemble of intermediates, I1 and I2, separated by the energy barrier of ～3.0?kcal mol^?1. Similarly, we find the population of two distinct I1 and I2 states in DMSO, however, the I1 appeared transiently around ～30–35?ns and is short-lived. But, the I2 ensemble is observed structurally compact and long-lived (～50–150?ns) as compared to unfolding in urea. Furthermore, the I1 and I2 are separated through a high energy barrier of ～6.0?kcal mol^?1. Thus, our results provide the structural insights of intermediates which essentially bear the signature of a different unfolding pathway of β-LgA in urea and DMSO.

Abbreviations β-LgA β-lactoglobulin

DMSO dimethyl sulfoxide

FEL free-energy landscape

GdmCl guanidinium chloride

I intermediate state

MG molten globule state

PME particle mesh Ewald

Q fraction of native contacts

RMSD root mean square deviation

RMSF root mean square fluctuation

R_g radius of gyration

SASA solvent Accessible Surface Area

scSASA the side chain SASA

Trp tryptophan

Communicated by Ramaswamy H. Sarma     

Dimethyl sulfoxide induces multilayer aggregates and prolongs survival of primary cultured hepatocytes

Hepatocytes cultured on collagen-coated surfaces formed aggregates in WilliamÕs E medium when supplemented with 1–2% dimethyl sulfoxide (DMSO) without causing obvious cellular injury. Hepatocytes in aggregates remained alive and differentiated for more than one month. DMSO decreased the adhesion of hepatocytes to collagen-coated surfaces which may explain the formation of hepatocyte aggregates.