Increase In Molecular Density Research Articles

Label-free fiber nanograting sensor for real-time in situ early monitoring of cellular apoptosis

The achievement of functional nanomodules for subcellular label-free measurement has long been pursued in order to fully understand cellular functions. Here, a compact label-free nanosensor based on a fiber taper and zinc oxide nanogratings is designed and applied for the early monitoring of apoptosis in individual living cells. Because of its nanoscale dimensions, mechanical flexibility, and minimal cytotoxicity to cells, the sensing module can be loaded in cells for long term in situ tracking with high sensitivity. A gradual increase in the nuclear refractive index during the apoptosis process is observed, revealing the increase in molecular density and the decrease in cell volume. The strategy used in our study not only contributes to the understanding of internal environmental variations during cellular apoptosis but also provides a new platform for nonfluorescent fiber devices for investigation of cellular events and understanding fundamental cell biochemical engineering.

Molecular weight dependent structure of the exopolysaccharide levan

Levan is a bacterial homopolysaccharide, which consists of β-2➔6 linked β-(D)-fructose monomers. Because of its structural properties and its health promoting effects, levan is a promising functional ingredient for food, cosmetic and pharmaceutical products. The properties of levan have been reported to be linked to its molecular weight. For a better understanding of how the molecular weight determines its polymer conformation in aqueous solution, levan produced by the food grade acetic acid bacterium Gluconobacter albidus TMW 2.1191 was analysed over a broad molecular weight range using dynamic and static light scattering and viscometry. Low molecular weight levan exhibit a compact random coil structure. As the molecular weight increases, the structure transforms into a compact non-drained sphere. The density of the sphere continues to increase with increasing molecular weight. This resulted in a negative exponent in the Mark-Houwink-Sakurada Plot. For the first time, an increase in molecular density with increasing molecular weight, as determined by a negative Mark-Houwink-Sakurada exponent, can be shown for biopolymers. Our results reveal the unique properties of high-molecular weight levan and confirm the need of further systematic studies on the structure-function relationship of levan for its targeted use in food, cosmetic and pharmaceutical applications.

Effect of Ferroelectric Nanopowder on Electrical and Acoustical Properties of Cholesteric Liquid Crysta

Ferroelectric nano-materials are very sensitive to several external stimuli and have attracted great deal of attention due to their property of improving various properties such as photoluminescence, higher polarization, fast response time, low operating voltage and improved conductivity. For enhancing the physical properties, a proper selection of nano-materials for liquid crystals depends upon various factors such as size, shape, preparation methods, surfactant concentration and amount of doping materials. In the present study an attempt is made to study electrical and acoustical properties of cholesteric liquid crystal after dispersing ferroelectric nano-powder of Barium Titanate (BaTiO3). In addition with this particle size and surface area of pure and nono-particle dispersed liquid crystal were also measured. Our investigation shows increase in Rao’s constant or molar sound velocity, which indicates increase in molecular density indicating a close packing of the material. The measurement of dielectric relaxation at different frequencies gives information about the dynamics of polar groups and molecular motion.

High‐pressure homogenization induced degradation of amylopectin in a gelatinized state

An investigation of the degradation mechanism of a highly branched polymer during a high‐pressure homogenization (HPH) process was performed using gelatinized waxy maize starch as a substrate. The degradation mechanism was studied using high‐performance size‐exclusion chromatography equipped with multi‐angle laser‐light scattering and refractive index detectors. The HPH induced an exponential molecular degradation trend that was a function of HPH pressure/cycles. The results revealed that HPH preferentially disrupted larger molecules and caused their size distribution (or molecular weight) to a narrow range, resulting in a maximum stable size (or molecular weight). A final z‐average radius of gyration of about 20 nm for amylopectin was observed after HPH for eight cycles at 100 MPa or two cycles at 150 MPa, which was due to the midpoint scission mechanism during the HPH treatment. The increase in molecular density after HPH verified the breakdown of the α‐1,4‐glycosidic bonds among the clusters of (midpoint scission) amylopectin.

ChemInform Abstract: Structure of 9-Nitro-(4)peristylane-1,5-dione

Decahydro-1,6:3,4-dimethano-3a-nitrocyclobuta [1,2:3,4]dicyclopentene-2,5-dione (II), C12-H11NO4, Mr = 233.2, monoclinic, P2(1)/n, a = 13.378 (7), b = 6.614 (1), c = 23.040 (15) A, beta = 92.53 (5) degrees, V = 2036.6 (4) A3, Z = 8, D chi = 1.521 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 9.3 cm-1, F(000) = 1312, T = 293 K, final R = 0.047, wR = 0.075 for 3075 reflections with I greater than 3 sigma(I). There are no unusually short intermolecular distances. A comparison of the molecular densities and packing coefficients of (I) [4]peristylane-1,5-dione with (II), indicates that the change in crystal density from (I) (1.415 g cm-3) to (II) (1.521 g cm-3) is the sole result of an increase in molecular density with NO2 substitution. The packing coefficients for (I) and (II) are identical.

Energy Shift for Core Electron Levels of Chemisorbed Molecules Observed by X-ray Photoelectron Spectroscopy in the Course of Monolayer Growth on a Si(111) Surface

Adsorption of fluorinated molecules from a liquid solution onto a fluorine-terminated Si(111) surface has been examined using X-ray photoelectron spectroscopy (XPS). The observed interchange of an F 1s peak from the terminal Si−F at the surface by the core electron peaks ascribed to the adsorbed molecule indicates the formation of an adsorbed monomolecular layer on the surface. In the case of molecules with a linear fluoroalkyl chain, the adsorbate core peaks are observed to shift to lower binding energies with increasing coverage of the Si surface by chemisorbed molecules: the maximum energy shifts, observed for 3-perfluorohexyl-1,2-epoxypropane, are −0.56 eV for C 1s and −0.35 eV for F 1s. This decrease in binding energy can be explained by the increasing relaxation shift caused by the increase of molecular density which permits a larger contribution of the van der Waals attraction among adsorbed molecules. This could be the first observation of a core-level shift due to lateral interchain interactions among ad-molecules, which shows that XPS is also useful for examining intermolecular interactions in the adsorbed layer.

Structure of 9-nitro-[4]peristylane-1,5-dione

Decahydro-1,6:3,4-dimethano-3a-nitrocyclobuta [1,2:3,4]dicyclopentene-2,5-dione (II), C12-H11NO4, Mr = 233.2, monoclinic, P2(1)/n, a = 13.378 (7), b = 6.614 (1), c = 23.040 (15) A, beta = 92.53 (5) degrees, V = 2036.6 (4) A3, Z = 8, D chi = 1.521 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 9.3 cm-1, F(000) = 1312, T = 293 K, final R = 0.047, wR = 0.075 for 3075 reflections with I greater than 3 sigma(I). There are no unusually short intermolecular distances. A comparison of the molecular densities and packing coefficients of (I) [4]peristylane-1,5-dione with (II), indicates that the change in crystal density from (I) (1.415 g cm-3) to (II) (1.521 g cm-3) is the sole result of an increase in molecular density with NO2 substitution. The packing coefficients for (I) and (II) are identical.

The accurate determination of ionospheric equivalent heights

A method has been described for measuring the equivalent height of an ionized region of the upper atmosphere with an accuracy of ? 0.5 km. It has been shown that though the accuracy is of this magnitude the resolving-power of the apparatus, which is fixed by the width of the pulse used, is not so great, there being difficulties in determining the height difference of two pulses less than 5 km. apart. However, when certain precautions are taken it is possible to obtain height separations of the order of 5 km. with a fair degree of accuracy. With the aid of the apparatus described it has been shown that there are no sudden changes of height in either the E1 or the F2 region greater than those which might be expected from errors of measurement. The equivalent height of the so-called abnormal E region has been compared with that of E1 and is shown to be not more than 3 or 4 km. greater. The frequency separation of the two critical frequencies for the ordinary and the extraordinary rays returned from the abnormal E region has been measured and is shown to be in agreement with the value to be expected on the magneto-ionic theory of the propagation of waves through an ionized medium. A discontinuity in the curve of height against frequency has been shown to exist at a frequency just less than 2 Mc./sec. This phenomenon, which was first noticed by Naismith at Slough two years ago, is shown to have all the characteristics of penetration and leads to the inference that there is a secondary maximum of ionization a few kilometres below the maximum of the E1 region, somewhat similar to the ledge on the F region discovered by Appleton. For purposes of reference in the paper this maximum is called Es. It has been shown that the height of the E1 region is less in winter than in summer but that the diurnal variation of height shows a minimum of height several hours after midday. It is suggested that the winter minimum is due to a general increase in molecular density in the atmosphere caused by the lower temperatures of winter time.