Molecular Interactions

Ultrasonic investigations of molecular interactions of polymer blends of chitosan (Ch)/ polyvinyl pyrrolidone (PVP), in a buffer solution (0.1 M acetic acid + 0.2 M sodium acetate) have been reported within the temperature range 303.15 K-323.15 K. Several acoustic parameters such as acoustic impedance, isothermal compressibility, adiabatic compressibility, internal pressure have been determined. Various thermo-dynamical parameters viz; pseudo-Gruneisen parameter and surface tension have been evaluated. Some thermo-elastic parameters such as bulk modulus, shear modulus and Young's modulus are also computed. The non-ideal behaviour of the blend, in the buffer solution has been explained in terms of its composition and temperature variation of acoustical and thermo-dynamical parameters. The reliability model for polymer blends of chitosan (Ch)/ polyvinyl pyrrolidone (PVP) has also been proposed.

The espresso coffee beverage is a polyphasic colloidal system, in which the liquid phase is topped by a wet foam of tiny sphere-shaped gas bubbles. Each sphere is surrounded by a liquid film (lamellae) that isolates it from its neighbours and that hosts biopolymers and natural ...

Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol, and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds of sound were combined with our previous densitity results to obtain the isentropic compressibility κ S . The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K S,m and its excess counterparts \(K_{S,m}^{\mathrm{E}}\) . The \(K_{S,m}^{\mathrm{E}}\) values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x i ln η i and excess Gibbs energies of activation for viscous flow ΔG ∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities \(\overline{K}_{\phi ,i}^{0}\) of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental results have also been discussed on the basis of IR measurements.

Introduction. – Comprehension of cell cycle regulation mechanisms has progressed very quickly these past few years and regulators of the cell cycle have gained widespread importance in cancer. This review first summarizes major advances in the understanding of the control of cell cycle mechanisms. Examples of how this control is altered in tumoral cells are then described.Current knowledge and key points. – The typical mammalian cell cycle consists of four distinct phases occurring in a well-defined order, each of which should be completed successfully before the next begins. Progression of eukaryotic cells through major cell cycle transitions is mediated by sequential assembly and activation of a family of serine-threonine protein kinases, the cyclin dependent kinases (CDK). The timing of their activation is determined by their post-translational modifications (phosphorylations/dephosphorylations), and by the association of a protein called cyclin, which is the regulatory subunit o...

Alkyl glucosides are non-ionic surfactants with wide range applications in food, cosmetics and pharmaceutical industries. They are derived from carbohydrate feedstocks and due to their favourable environmental and dermatological properties, they are increasing in popularity. Dodecyl β-D-glucopyranoside is a surfactant with molecular structure of 12 carbons chains with glucopyranoside as the head group of the molecule. In this research, molecular dynamics (MD) simulation is applied to examine the molecular interactions between dodecyl β-Dglucopyranoside and water by using COMPASS force field. The main objective is to determine the tendency of hydrogen bonding forming between the head group of the glucosides and water. The periodic system is constructed at 298K. The ensemble used in this research is NVT (constant volume – constant temperature). The equilibration stage is 1ns prior to the actual production stage of 3ns. The molecular interaction is analysed using Radial Distribution Function (RDF) where hydrogen bonding is considered in the range of 1.48Å to 4.0Å. Accelerys Material Studio 7.0 software is used as the computational technique in this research. The tendency to form hydrogen bonding is between 1.63Å - 3.99Å of first peak hydrogen bond radius detected from the radial distribution analysis (RDF). At least, a single hydrogen bond is form for every hydroxyl group attached to the head group and water molecules.

Alkyl glucosides are non-ionic surfactants with wide range applications in food, cosmetics and pharmaceutical industries. They are derived from carbohydrate feedstocks and due to their favourable environmental and dermatological properties, they are increasing in popularity. Dodecyl β-D-glucopyranoside is a surfactant with molecular structure of 12 carbons chains with glucopyranoside as the head group of the molecule. In this research, molecular dynamics (MD) simulation is applied to examine the molecular interactions between dodecyl β-Dglucopyranoside and water by using COMPASS force field. The main objective is to determine the tendency of hydrogen bonding forming between the head group of the glucosides and water. The periodic system is constructed at 298K. The ensemble used in this research is NVT (constant volume – constant temperature). The equilibration stage is 1ns prior to the actual production stage of 3ns. The molecular interaction is analysed using Radial Distribution Function (RDF) where hydrogen bonding is considered in the range of 1.48Å to 4.0Å. Accelerys Material Studio 7.0 software is used as the computational technique in this research. The tendency to form hydrogen bonding is between 1.63Å - 3.99Å of first peak hydrogen bond radius detected from the radial distribution analysis (RDF). At least, a single hydrogen bond is form for every hydroxyl group attached to the head group and water molecules.

Pesticides are extensively used in agriculture as a part of pest control strategies. Owing to their xenobiotics characteristics, pesticides may adversely affect the proliferation of beneficial soil microorganisms and their associated biotransformation in the soil. Inactivation of nitrogen‐fixing and phosphorus‐solubilizing microorganisms is observed in pesticide‐contaminated soils. Recent studies show that some pesticides disturb molecular interactions between plants and N‐fixing rhizobacteria

Fluorescent peptides form a new generation of analytical tools for visualizing intracellular processes and molecular interactions at the level of single cells. The peptide-based reporters combine the sensitivity of fluorescence detection with the information specificity of amino acid sequences. Recently we have succeeded in targeting a fluorescent heptapeptide (acetyl-CKGGAKL) carrying a peroxisomal targeting signal (PTS1) to peroxisomes in intact cells. The fluorophores conjugated to the PTS1-peptide were fluorescein, BODIPY and the pH-sensitive SNAFL-2. When added to cells, these fluorescent peptides were internalized at 37 degrees C and typically visible in the cell after 15 min or less. Cells lacking an active peroxisomal protein import system, as in the case of Zellweger syndrome, were stained diffusely throughout the cell. Uptake of the peptide probes was not inhibited at 4 degrees C or when the cells were depleted of ATP. Under these conditions translocation to peroxisomes wa...

It has been generally accepted that the macromolecular hypothesis was for the first time presented by H. Staudinger (1920). It is shown in this article, however, that Roger Boscovich, in his monumental work "Theory of natural philosophy", as early as in the 18th century, pointed out that the spiral atomic chains could be formed. He also pointed out that the shape of the chain could be markedly changed due to slight changes in the distances among the atoms. The elastic properties of the chains have been stressed. The author of this article also presented some examples of the applications of Boscovich's theory for the interpretation of free-radical polymerization of compressed ethylene gas and liquid methyl methacrylate. The priority of Boscovich's macromolecular hypothesis is doubtless and his theory is still applicable in the current polymer science.