Ultrasonic and dielectric study of nonequilibrium monosaccharide solutions in water

Based on broadband acoustical (10 kHz < or = nu < or = 2 GHz) and dielectric (1 MHz < or = nu < or = 40 GHz) spectrometry, time-resolved ultrasonic attenuation coefficient and static permittivity measurements have been performed on nonequilibrium tautomer solutions of d-arabinose and d-fructose in water. Via the chair-chair ring inversion the ultrasonic attenuation measurements display the decrease in the content of beta-arabinopyranoside and the increase of the alpha-fructopyranoside concentration during the establishment of the tautomer equilibrium. For the arabinose solutions, the mutarotation decay constant (m=(0.027+/-0.004) min(-1), 20 degrees C) from the ultrasonic measurements almost agrees with that from optical activity observations. For d-fructose the ultrasonic decay constant (m=(0.043+/-0.007) min(-1), 20 degrees C) is smaller than that from rotary polarization (m=0.054 min(-1), 20 degrees C) and dielectric permittivity (m=(0.058+/-0.007) min(-1), 20 degrees C), likely because the latter methods probe parallel pathways in the tautomer equilibrium whereas the former one reflects only one pathway.     

Solution properties of viilian, the exopolysaccharide from Lactococcus lactis subsp. cremoris SBT 0495

The exopolysaccharide (EPS) "viilian" was isolated from a large-batch fermentation of Lactococcus lactis subsp. cremoris SBT 0495. After applying a newly developed purification procedure, pure viilian with a weight-averaged molar mass of 2.64 x 10(3) kg/mol was obtained in a yield of 0.6 g/L culture broth. The native EPS, as well as lower molar mass fractions obtained by sonication of the native polymer, were studied by capillary viscometry and size-exclusion chromatography (SEC) coupled to multiangle laser light scattering detection (MALLS). From the viscosity data at various ionic strengths, we extracted a Mark-Houwink-Kuhn-Sakurada exponent a = 0.79, and a Smidsrod B value of 0.03. By application of the Hearst, Bohdanecky, and Odijk models for stiff polymer coils, in connection to the experimental viscosity data, we established the characteristic ratio to be C(infinity) = 44 and the intrinsic persistence length q(0) = 11.5 nm. The rms radii of gyration predicted from each of the models were in good agreement with the experimental radii (e.g., (1/2)(w) = 162 nm for native viilian in 0.2M NaNO(3)), as determined by SEC-MALLS. In addition, the Odijk model predicts correct ionic strength-linear charge density dependence of the rms radius of gyration. From the combined viscosity and SEC-MALLS experiments we concluded that, in dilute aqueous solutions, viilian behaves as an intermediately stiff, random coil polyelectrolyte system.Copyright 2000 John Wiley & Sons, Inc.     

Dielectric properties of poly-L-glutamic acid in salt-free aqueous solutions

The electric permittivity of poly-L-glutamic acid (PGA) in salt-free aqueous solutions was measured in the frequency range 2.5 kHz – 100 MHz at different concentrations and degrees of ionization. Two samples of different molecular weight were investigated. The experimental results could under most circumstances be described by a superposition of two dispersion curves of the Cole-Cole type. The low-frequency dielectric parameters were strongly molecular weight dependent, the high-frequency ones not. Strong concentration effects were observed resulting in increasing specific dielectric increments and relaxation times with decreasing concentration. Using the theory proposed by Van der Touw and Mandel to interpret the experimental results these concentration effects could be ascribed to the influence of the polyion interactions on the average dimensions and the rigidity of the polyelectrolyte chains. The change in the total dielectric increment and low-frequency relaxation time with degree of ionization correctly reflects the helix-coil transition of PGA occurring in ths region α = 0.3–0.5. The effect of counterion size and charge on the dielectric behaviour was also found to be consistent with the theoretical model.     

Dielectric spectroscopy on aqueous electrolytic solutions

In this work, detailed dielectric measurements are presented on aqueous electrolytic solutions of NaCl and KCl in a broad frequency range, typical for modern telecommunication techniques. The complex dielectric permittivity or equivalently the complex conductivity are systematically studied as function of frequency (100 MHz-40 GHz), temperature (10-60 degrees C) and molar concentration (0.001-1 mol/l). By a detailed analysis of the dielectric results using an asymmetrically broadened Cole-Davidson distribution of relaxation times, in addition to dc conductivity, the dielectric response as function of frequency, temperature, and molar concentration was fully parameterized by a total of 13 parameters. This model ansatz and the 13 parameters include an enormous predictive power, allowing a reasonable estimation of the dielectric constant, loss, and the conductivity for any set of external variables frequency, temperature and concentration. The proposed method is not only useful for rather simple electrolytic solutions, but also for cell suspensions and biological matter, if additional processes, especially at low frequencies, are adequately taken into account.     

Dielectric increment and dielectric dispersion of solutions containing simple charged linear macromolecules. II. Experimental results with synthetic polyelectrolytes

The electric permittivity of aqueous solutions of different synthetic polyelectrolytes have been measured as a function of frequency in the range 5 kHz up to 100 MHz in the absence of added salt. Solutions of polymethacrylic acid and polyacrylic acid of different degrees of polymerization, both partially neutralized with NaOH, were investigated as well as solutions of Na-polystyrenesulphonate at different concentrations.For all systems a dispersion profile with two separated dispersion regions was obtained with a molecular weight dependent value of the static electric permittivity. The low frequency dispersion region was found to be characterized by a molecular weight dependent mean relaxation time while for the high frequency dispersion region both the mean relaxation time and the dielectric increment are molecular weight independent. It is shown that the reciprocal values of the specific increments and of the relaxation times depend linearly on the macromolecular concentration. Extrapolation of the corresponding quantities to infinite dilution was found to be possible. A comparison of these extrapolated values with calculated ones according to the previously derived theory also applicable to flexible macromolecules establishes that this theory describes satisfactorily the dielectric behaviour of the systems investigated.The conclusion is reached that the high frequency dispersion and relaxation can be attributed to fluctuations in the distribution of bound counterions along limited parts of the macromolecule. The relaxation time of the low frequency dispersion region seems to be essentially determined by the rotation of the complete molecule and the static electric permittivity can he explained in terms of fluctuations in the counterion density extending over the whole macromolecule.     

Hydration dependence of conformational dielectric relaxation of lysozyme

Dielectric response of hen egg white lysozyme is measured in the far infrared (5-65 cm-1, 0.15-1.95 THz, 0.6-8.1 meV) as a function of hydration. The frequency range is associated with collective vibrational modes of protein tertiary structure. The observed frequency dependence of the absorbance is broad and glass-like. For the entire frequency range, there is a slight increase in both the absorbance and index of refraction with increasing hydration for <0.27 h (mass of H2O per unit mass protein). At 0.27 h, the absorbance and index begin to increase more rapidly. This transition corresponds to the point where the first hydration shell is filled. The abrupt increase in dielectric response cannot be fully accounted for by the additional contribution to the dielectric response due to bulk water, suggesting that the protein has not yet achieved its fully hydrated state. The broad, glass-like response suggests that at low hydrations, the low frequency conformational hen egg white lysozyme dynamics can be described by a dielectric relaxation model where the protein relaxes to different local minima in the conformational energy landscape. However, the low frequency complex permittivity does not allow for a pure relaxational mechanism. The data can best be modeled with a single low frequency resonance (nu approximately 120 GHz=4 cm-1) and a single Debye relaxation process (tau approximately .03-.04 ps). Terahertz dielectric response is currently being considered as a possible biosensing technique and the results demonstrate the required hydration control necessary for reliable biosensor applications.     

Ab initio and dielectric studies of succinic acid and maleic acid in 1,4-dioxane

In a continuing effort to understand the hydrogen bond through the study of dielectric and computational conformal studies of dilute solutions, succinic acid and maleic acid are studied in solutions of 1,4-dioxane solvent. Dielectric studies give an account of the net dipole moment of the system under study, which is then compared with the values obtained from conformal analysis. The dielectric measurements were made at 303 K at a frequency of 9.83 GHz using a X-band microwave test bench in order to determine the relaxation times and the dipole moments. The static dielectric permittivity and the high frequency dielectric permittivity were measured using a LCR meter and an Abbe's refractometer, respectively. The results are inspected in comparison with the dipole moment results of ab initio calculations of some of the conformers in gas phase and in liquid phase. Gaussian-03 software package with 6–31G(d) basis set optimisation was used for this purpose. Onsager's reaction field model is used to study the solvation of the dicarboxylic acids in 1,4-dioxane. The results are interpreted in terms of the intermolecular and intramolecular hydrogen bond interactions in the dilute systems.     

Dielectric relaxation of DNA solutions. II

Real and imaganiry parts of complex dielectric constant of dilute solutions of DNA in 10^?3M NaCl with molecular weight ranging from 0.4 × 10⁶ to 4 × 10⁶ were measured at frequencies from 0.2 Hz to 30 kHz. Dielectric increments Δε were obtained from Cole-Cole plots and relaxation times τ_D from the loss maximum frequency. The τ_D of all samples agrees well with twice of the maximum viscoelastic relexation time in the Zimm theory, indicating that the low-frequency dielectric relaxiation should be ascribed to be the rotation of DNA. The rms dipole moment, which was obtained from Δε, agree well with that calculated from the counterion fluctuation theory. The dielectric increment was found to be greatly depressed in MgCl₂, which is resonably interpreted in terms of a strong binding of Mg⁺⁺ ions with DNA.     

A comparative dielectric study of human serum low density lipoprotein before and after partial digestion by trypsin

The relative permittivity of aqueous solutions of human serum low density lipoprotein (LDL) and partially trypsin digested lipoprotein (T-LDL) has been determined for various concentrations at 20°C over the frequency range 0.15–100 MHz. Comparison of the dielectric dispersion curves for the digested lipoprotein with those for the native preparation revealed a larger low-frequency dielectric increment, which may be attributed to an increase in the number of counterions moving over the surface of the molecule. An explanation of this observation is an elevation of 70% in the net negative charge on the surface of the trypsin-treated particle as compared to its native counterpart.     

Fatty acid contamination and dielectric relaxation in phospholipid vesicle suspensions

Aqueous vesicle or micelle suspensions from various synthetic lecithins or surfactants - most of them purified by a simple ion-exchange procedure in methanol - were investigated, some with ionic admixtures. The dielectric permittivity '(nu) between 5 kHz and 100 MHz was determined by different time-and frequency-domain methods, with attention given to electrode polarization below 1 MHz. Pure ether lecithins (used to reduce hydrolysis during preparation) as well as ester lecithins showed no dielectric dispersion below 10 MHz (Delta' 3). In contrast, even dilute colloidal solutions containing about 1 mol% (with respect to solute) ionic amphiphiles normally exhibited large dielectric dispersion (10 < Delta' < 700), especially with electrolyte present. This low-frequency dispersion is sensitive to vesicle coagulation or fusion. Underlying relaxation mechanisms are discussed, and the main relaxation is shown to be the same as for other charged colloids. This conclusion suggest a new interpretation of measurements, previously reported by other authors, who gave an interpretation in terms of correlated zwitterionic head group orientation in multilamellar lecithin liposomes. Possible effects from traces of impurities in lipids are discussed.     

The periodicity of primary increment formation in the otoliths of Arctic charr Salvelinus alpinus (L.)

The role of environmental factors in the regulation of sub-annual increment formation in fish otoliths appears to differ markedly between species. To examine the periodicity of primary increment formation in the otoliths of O + Arctic charr, Salvelinus alpinus (L.), and the effects of temperature, and photoperiod on their formation, fish were held under controlled environmental conditions. Primary growth increments were found in the otoliths of fish held at constant temperature (18° C) and at ambient temperature [fluctuating with a circadian and circannual rhythm (4–18° C)]. Consistent and significant disruptions in increment formation occurred however, in experimental groups subjected to rapid change from ambient photoperiod to a 6L: 6D photo-period for 96 h. Disruptions in increment formation were also observed immediately following transportation of fish between holding facilities and following disease treatment. The number of otolith increments formed in fish held on an ambient photoperiod regime, correlated closely with time elapsed in days since checkmark formation ( r = 0.989, P ≤0.001) in fish sampled sequentially over a period of 10 to 105 days. Thus we demonstrate that under conditions of ambient photoperiod, primary increments are formed daily.     

Dielectric and conformal studies of 1-propanol and 1-butanol in methanol

Hydrogen bonds in small chain alcohol-alcohol binary systems alter the dielectric permittivity of the binary system. With a view to obtain a better understanding of the interactions in such systems, the complex permittivity spectra of mixtures of methanol (ME) with 1propanol (1PR) and 1butanol (1BU) have been measured in the frequency range 10 MHz to 20 GHz using time domain reflectometry at 288 K, 298 K, 308 K and 318 K. The dielectric parameters such as static dielectric constant and relaxation time were obtained using the calibration method based on nonlinear least squares fit method. Using these parameters excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, and thermodynamic parameters were determined. It is observed that the static permittivity decreases with increase in mole fractions of 1PR/1BU in ME whereas the relaxation time increases for both the binary systems. Computational conformational analysis was performed using ab initio Hartree-Fock using Gaussian-03 program. The present studies indicate a difference in the solvation of ME by 1PR/1BU and vice versa. Further, the interaction of ME-1PR is distinctly different at the 0.55 molar concentration of 1PR while the ME-1BU system shows strong interactions in both the methanol and the 1BU rich regions.     

Effect of ions on counterion fluctuation in low-molecular weight DNA dielectric dispersions

The dielectric permittivity of aqueous solutions of low-molecular weight DNA (Mr = 3.2 X 10(5) ) in the presence of MgCl2 and AgNO3 has been measured in the frequency range from 5 kHz to 30 MHz, at a temperature of 25 degrees C. The DNA concentration was 3.5 X 10(-4) M in terms of phosphate and the salt concentration was varied from 1 X 10(-5) to 2 X 10(-4) M. The dielectric results have been analyzed in terms of two contiguous dielectric dispersions, and characteristic parameters have been discussed on the basis of polyelectrolyte theories which deal with counterion fluctuation. Some molecular parameters of the DNA molecule in electrolyte solutions are estimated.     

Analytical ultracentrifugation in a Gibbsian perspective

The analytical ultracentrifuge has come into new intensive use following complete instrumental redesign and the use of advanced computer technologies for the analysis and interpretation of experimental results. Major attention is now devoted to the evaluation of interactions between similar and dissimilar biological macromolecules in dilute and concentrated systems. Electrostatically charged biological solute systems additionally comprise low molecular weight charged and non-charged cosolvents. Solvent/cosolvent interactions, insufficiently considered in most current analytical ultracentrifugation analyses, may quantitatively affect solute/solute interactions. For comprehensive analysis the Svedberg derivation considering a buoyant molar mass (1 - rho0 partial specific volume)M2 and valid at vanishing solute concentration for strictly two component systems only, should be replaced, following classical thermodynamic analysis, by the ratio (delta rho/delta c2)(mu)/d pi/dc2 of the density increment at constant chemical potential of diffusible cosolvents, to the derivative of the osmotic pressure with solute concentration. Disregard of the solvent/cosolvent and solute/cosolvent interactions should be avoided.     

Otolith morphology and periodicity of increment formation on the sagitta of manybar goatfish Parupeneus multifasciatus (Mullidae)

Otolith morphology and microstructure of the sagitta are described in the mass tropical species manybar goatfish Parupeneus multifasciatus. The hatch check is absent on the sagitta, and the appearance of the first contrasting increment is connected with the transition of the larva to exogenous feeding. The increments are distributed within several concentric zones, and each zone is separated by more pronounced dark areas (in transmitted light) of the increments (checks). The number of increments within a zone is variable; and the modal group (with the exception of the first zone from the primordium to the first check) includes from six to ten increments. In the juveniles, the periodicity of increment formation on the sagitta ranges from <1 to >3 in a day, but it is close to one increment per day in the individuals larger than 86 mm FL and 11 g in weight. The number of increments deposited in a day does not depend on the growth rate or feeding frequency of the juveniles.     

Molecular-weight dependence of the low-frequency dielectric properties of aqueous solutions of gel-fractionated DNA

Combined three- and four-terminal AC bridge measurements have been made at frequencies from 10 Hz to 100 KHz on samples of DNA with different molecular weight in aqueous solution under varying conditions of DNA concentrations and added salt. A method is described for the separation of large quantities of DNA fractionated according to size. A complicated pattern of dependence of the specific dielectric increment on concentration is found, and the difficulties of comparing the results from sample to sample are discussed. The dielectric properties of the fractionated samples of DNA in aqueous solution are reported for solutions sufficiently dilute that specific dielectric increment is independent of concentration. The specific dielectric increment of the solutions (with concentration measured in moles of DNA molecules/liter) is found to increase as the square of the molecular weight. The results are compared with results of polyelectrolyte theories which deal explicitly with counterion fluctuations and interactions. The frequency dependence of the dispersion is much broader than for simple Debye relaxation. It is satisfactorily fitted by the empirical Cole–Cole circular are function and the breadth of the dispersion is found to be, if anything, less for the fractionated samples than for native DNA in solution.     

DIMERIZATION IN HIGHLY CONCENTRATED SOLUTIONS OF PHOSPHOIMIDAZOLIDE ACTIVATED MONONUCLEOTIDES

Phosphoimidazolide activated ribomononucleotides (*pN) are useful substrates for the non-enzymatic synthesis of polynucleotides. However, dilute neutral aqueous solutions of *pN typically yield small amounts of dimers and traces of polymers; most of *pN hydrolyzes to yield nucleoside 5-monophosphate. Here we report the self-condensation of nucleoside 5-phosphate 2-methylimidazolide (2-MeImpN with N = cytidine, uridine or guanosine) in the presence of Mg2+ in concentrated solutions, such as might have been found in an evaporating lagoon on prebiotic Earth. The product distribution indicates that oligomerization is favored at the expense of hydrolysis. At 1.0 M, 2-MeImpU and 2-MeImpC produce about 65% of oligomers including 4% of the 3,5-linked dimer. Examination of the product distribution of the three isomeric dimers in a self-condensation allows identification of reaction pathways that lead to dimer formation. Condensations in a concentrated mixture of all three nucleotides (U,C,G mixtures) is made possible by the enhanced solubility of 2-MeImpG in such mixtures. Although percent yield of internucleotide linked dimers is enhanced as a function of initial monomer concentration, pyrophosphate dimer yields remain practically unchanged at about 20% for 2-MeImpU, 16% for 2-MeImpC and 25% of the total pyrophosphate in the U,C,G mixtures. The efficiency by which oligomers are produced in these concentrated solutions makes the evaporating lagoon scenario a potentially interesting medium for the prebiotic synthesis of dimers and short RNAs.     

Dielectric studies on self-associating nucleosides and bases in aqueous solution

Measurements have been made of the dielectric properties of aqueous solutions in which aggregates are formed by stacking. The nucleosides cytidine, uridine and thymidine, and the bases purine, pyrimidine and 6-methylamino-9-methyl-purine (N⁶N⁹-dimethyladenine) were investigated at around 1 MHz, where the static increments can be determined, and for cytidine, dimethyladenine, uridine and pyrimidine measurements were also made in the 100–2000 MHz range where the main relaxation of the solute dipoles is found. Whereas cytidine and purine show a positive static dielectric increment increasing linearly with concentration, dimethyladenine, uridine, thymidine and pyrimidine show a similar negative effect. Also, within the experimental accuracy, single retaxation times are found for the solute dispersions investigated.It is suggested that these relaxations correspond to the effects of free rotation of individual polar molecules in the plane of stacking. This phenomenon would also account for the linear variation of the dielectric increments with concentration. These increments are thought to be positive or negative due to the varying balance in the solutions between the loss of polarization due to displaced and “bound” water and the corresponding gain due to the polarity of the solute molecules.     

Complex Dielectric Properties of Sulfate-Reducing Bacteria Suspensions

Sulfate-reducing bacteria (SRB) can potentially enhance the remediation of heavy metals in the subsurface. Previous geophysical research has demonstrated the sensitivity of electrical measurements to SRB-mediated mineral transformation in porous media. However, the inherent dielectric properties of SRB and their direct contribution to the electrical properties of porous media are poorly understood. We studied the complex dielectric properties of SRB (Desulfovibrio vulgaris) suspensions at different concentrations and at different growth stages using a two-electrode dielectric spectroscopy measurement over the frequency range of 20 Hz to 1 MHz. Our results show higher dielectric responses (relative dielectric permittivity, real and imaginary conductivity) occurred with higher bacteria concentration at frequencies <10 kHz. Additionally, permittivity and conductivity both decreased as cells aged from mid-log phase to late stationary phase. Our results suggest that dielectric spectroscopy measurements can be used to noninvasively monitor biomass and various growth stages of SRB. Our work advances the interpretation of electrical signals associated with SRB observed in the subsurface.