Dielectric behavior of aqueous solutions of plasmid DNA at microwave frequencies.

The relative permittivity and dielectric loss of aqueous solutions of plasmid (pUC8.c1 and pUC8.c2) DNA have been measured at 20 degrees C over the frequency range 100 MHz-10 GHz. The solutions had a concentration of 0.1% DNA, and were studied both in the relaxed and the supercoiled form. The dielectric measurements were made using a variety of techniques including frequency domain and time domain methods of operation. No evidence of any resonance absorption, nor of any other kind of enhanced absorption, was observed.     

Dielectric properties of oxyhemoglobin and deoxyhemoglobin in aqueous solution at microwave frequencies

The complex dielectric constant of aqueous hemoglobin solution was measured at 9.5 GHz. A microwave technique allowing phase and attenuation settings with an accuracy of 0.3° and 0.03 db was used. The shift of the relaxation wavelength and the hydration values of horse hemoglobin were determined for native and lyophilized hemoglobin solution and erythrocytes suspensions as well. The isotope effect of light and heavy water on these parameters was detected. The influence of buffers was studied. Relative measurements, with the sensitivity increased by a factor of 20, were made with alternating oxygenated and deoxygenated human hemoglobin solutions. The oxygenation of hemoglobin was found to leave the hydrated molecule volume invariant within ±250 ų, while a shift of the relaxation wavelength of 0.0025 ± 0.0015 cm occurs for a hemoglobin concentration of 107 g/l. The results are discussed in terms of the structure and function interrelationship of hemoglobin and the current picture of water structure.     

Dielectric properties of lens tissue at microwave frequencies

The relative permittivity and conductivity of rabbit eye lens were measured in the frequency domain between 2 and 18 GHz at temperatures of 37 and 20°C. An analysis of the data suggested that a significant proportion of the bulk water in nuclear and cortical lens tissue may behave differently to pure water. In addition, the Maxwell-Fricke mixture theory was used to estimate the amount of hydrated water that relaxes far below 1 GHz.     

Dielectric properties of human fetal organ tissues at radio frequencies

The in vitro dielectric properties of human fetal organ tissues were measured in the frequency range from 100 kHz to 500 MHz at 24 °C. The dielectric measurements were performed by using a network analyzer (HP4195A) and a coaxial line capacitive sensor. The tested samples, including skin, muscle, heart, lung, liver, kidney, spleen, and brain tissues, were obtained from the legal abortion of five women with 14–16 week gestation periods. © 1996 Wiley-Liss, Inc.     

Dielectric studies of wheat in powder form at microwave frequencies

Dielectric constant and loss factor of Raj-4120 variety of Indian wheat were determined in powder form (grain size 125 to 150 micron) at room temperature. Microwaves at three different frequencies were employed in C-band, X-band and Ku-band respectively for investigating frequency dependence of dielectric parameters of the sample. Bulk dielectric values of the sample were determined by employing the dielectric mixture relations, such as, half power mixture equation, Landau and Lifshitz, Looyenga equation etc.     

DNA replication in Escherichia coli 15T- growing at 20 degrees C

Escherichia coli 15T⁻ grows slowly in succinate or aspartate-M9 media. In both media, a gap in DNA replication is observed at 37 °C which is either not present at 20 °C or of very much shorter duration than at 37 °C. However, dichotomous replication is not observed in glucose M9 at 20 °C. The results suggest that initiation of replication in glucose is different from that in aspartate or succinate cultures.     

Dielectric properties of human red blood cells in suspension at radio frequencies

Dielectric properties of human red blood cells (RBCs) in suspension (hematocrit 50%) from 243 healthy persons (120 males, 123 females) were measured at 25 °C in a frequency range of 1–500 MHz, with a coaxial transmission line reflection method (one-side measurement). The measuring system, controlled by an IBM-PC computer, was composed of a network analyzer (HP4195A), an impedance test adapter (HP41951-61001), a coaxial line sensor, and a temperature-controlling set. The data measured revealed a statistically significant age dependence, with a critical age of about 49 years, above which permittivity and conductivity of human RBCs in suspension decreased significantly. © 1994 Wiley-Liss, Inc.     

Dielectric properties of developing rabbit brain at 37 degrees C

The dielectric properties of developing rabbit brain were measured at 37 degrees C between 10 MHz and 18 GHz using time domain and frequency domain systems. The results show a variation with age of the dielectric properties of brain. An analysis of the data suggests that the water dispersion in the brain of newly born animals can be represented by a Debye equation. This dispersion increases in complexity with age, and there is evidence of a smaller additional relaxation process centered around 1 GHz. It is concluded that the principal contribution to this subsidiary dispersion region arises from water of hydration.     

Theory of the anomalous resonant absorption of DNA at microwave frequencies

Aqueous solutions of oligopolymer DNA have been observed by Edwards, Davis, Swicord & Saffer to show structured absorption of microwave energy in the region of several gigahertz characteristic of an ordered series of compressional normal mode vibrations propagating on the polymer chain. Hydrodynamic coupling of such vibrations to the surrounding solvent would preclude the existence of sharp resonances. The inclusion of electromagnetic interactions with surrounding counter ions yields a richer space of possibilities for complex behavior of the combined system. A well defined resonant absorption peak appears when the molecular motion and the nearby solvent motion are even slightly decoupled. The microwave electric fields in the vicinity of the molecule provide a mechanism for such a decoupling not present for the case of electrically neutral solvent.     

Why structured water causes sharp absorption by DNA at microwave frequencies

Aqueous solutions of oligopolymer DNA have been observed by G.S. Edwards, C.C. Davis, M.L. Swicord and J.D. Saffer, Phys. Rev. Lett. 53, 1284 (1984) to show structured absorption of microwave energy in the region of several gigahertz, characteristic of an ordered series of compressional normal mode vibrations propagating on the polymer chain. Although hydrodynamic coupling of such vibrations to the surrounding solvent would preclude the existence of sharp resonances, the molecular nature of the solvent in the near neighborhood of the polymer and- paradoxically- the strong water/polymer interactions provide a means for effectively decoupling the polymer motion from the dissipation of the liquid. Recent measurements of DNA/water relaxation times allow estimating numerical values in a parameterization of the decoupling effect. The resulting predicted frequency dependence explains many of the smaller features of Edwards' experiment as well as the overall anomaly. A simple model gives a surprisingly complete account of the features of the data using only values determined from other experiments.     

Structure and mechanical properties of giant lipid (DMPC) vesicle bilayers from 20 degrees C below to 10 degrees C above the liquid crystal-crystalline phase transition at 24 degrees C

We have used micromechanical tests to measure the thermoelastic properties of the liquid and gel phases of dimyristoylphosphatidylcholine (DMPC). We have found that the rippled P beta' phase is only formed when a vesicle is cooled to temperatures below the main acyl chain crystallization transition, Tc, under zero or very low membrane tension. We also found that the P beta' surface ripple or superlattice can be pulled flat under high membrane tension into a planar structure. For a ripple structure formed by acyl chains perpendicular to the projected plane, the projected area change that results from a flattening process is a direct measure of the molecular crystal angle. As such, the crystal angle was found to increase from about 24 degrees just below Tc to about 33 degrees below the pretransition. It was also observed that the P beta' superlattice did not form when annealed L beta' phase vesicles were heated from 5 degrees C to Tc; likewise, ripples did not form when the membrane was held under large tension during freezing from the L alpha phase. Each of these three procedures could be used to create a metastable planar structure which we have termed L*beta' since it is lamellar and plane-crystalline with acyl chains tilted to the bilayer plane. However, we show that this structure is not as condensed as the L beta' phase below 10 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement and modeling of multiple substrate oxidation by methanotrophs at 20 degrees C

Earlier experiments have shown that when Methylosinus trichosporium OB3b was grown at 30 degrees C, greater growth and degradation of chlorinated ethenes was observed under particulate methane monooxygenase (pMMO)-expressing conditions than sMMO-expressing conditions. The effect of temperature on the growth and ability of methanotrophs to degrade chlorinated ethenes, however, has not been examined, particularly temperatures more representative of groundwater systems. Thus, experiments were performed at 20 degrees C to examine the effect of mixtures of trichloroethylene, trans-dichloroethylene and vinyl chloride in the presence of methane on the growth and ability of Methylosinus trichosporium OB3b cells to degrade these pollutants. Although the maximal rates of chlorinated ethane degradation were greater by M. trichosporium OB3b expressing sMMO as compared with the same cell expressing pMMO, the growth and ability of sMMO-expressing cells to degrade these cosubstrates was substantially inhibited in their presence as compared with the same cell expressing pMMO. The Delta model developed earlier was found to be useful for predicting the effect of chlorinated ethenes on the growth and ability of M. trichosporium OB3b to degrade these compounds at a growth temperature of 20 degrees C. Finally, it was also discovered that at 20 degrees C, cells expressing pMMO exhibited faster turnover of methane than sMMO-expressing cells, unlike that found earlier at 30 degrees C, suggesting that temperature may exert selective pressure on methanotrophic communities to express sMMO or pMMO.     

Studies of alpha- and betaL-crystallin complex formation in solution at 60 degrees C

Studies of molecular mechanisms of chaperone-like activity of alpha-crystallin became an active field of research over last years. However, fine interactions between alpha-crystallin and the damaged protein and their complex organization remain largely uncovered. Complexation between alpha- and betaL-crystallins was studied with thermal denaturation of betaL-crystallin at 60 degrees C using small-angle X-ray scattering (SAXS), light scattering, gel-permeation chromatography and electrophoresis. A mixed solution of alpha- and betaL-crystallins in concentrations about 10 mg/ml incubated at 60 degrees C was found to contain their soluble complexes with mean radius of gyration approximately 14 nm, mean molecular weight approximately 4000 kDA and maximal size approximately 40 nm. In pure betaL-crystallin solution, complexes were not observed at 60 degrees C. In SAXS studies, transitions in the alpha-crystallin quaternary structure at 60 degrees C were shown to occur and result in a double increase of the molecular weight. It suggests that during the temperature-induced denaturation of betaL-crystallin it binds with modified alpha-crystallin or, alternatively, alpha-betaL-crystallin complexation and alpha-crystallin modifications are concurrent. Estimates of the alpha-betaL-crystallin dimensions and relative contents of alpha- and betaL-crystallins in the complex suggest that several alpha-crystallin molecules are involved in complex formation.     

Conductivity values of tissue culture medium from 20 degrees C to 40 degrees C

Few studies are available that relate conductivity and temperature in solutions commonly used in tissue culture media. The purpose of this paper is to provide equations relating conductivity and temperature (in the range 20 degrees C-40 degrees C) for five solutions: 0.9% saline, MEM (Minimum Essential Media), horse serum, MEM with 1% horse serum, and MEM with 10% horse serum.