Aggregation of Gold Nanoparticles in Presence of the Thermoresponsive Cationic Diblock Copolymer PNIPAAM-b-PAMPTMA.

The adsorption of the thermoresponsive positively charged copolymer poly(-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride, PNIPAAM-b-PAMPTMA(+), onto negatively charged gold nanoparticles can provide stability to the nanoparticles and make the emerging structure tunable by temperature. In this work, we characterize the nanocomposite formed by gold nanoparticles and copolymer chains and study the influence of the copolymer on the expected aggregation process that undergoes those nanoparticles at high ionic strength. We also determine the lower critical solution temperature (LCST) of the copolymer (around 42 °C) and evaluate the influence of the temperature on the nanocomposite.

The Histidine Phosphocarrier Kinase/Phosphorylase from Bacillus Subtilis Is an Oligomer in Solution with a High Thermal Stability.

The histidine phosphocarrier protein (HPr) kinase/phosphorylase (HPrK/P) modulates the phosphorylation state of the HPr protein, and it is involved in the use of carbon sources by Gram-positive bacteria. Its X-ray structure, as concluded from crystals of proteins from several species, is a hexamer; however, there are no studies about its conformational stability, and how its structure is modified by the pH. We have embarked on the conformational characterization of HPrK/P of (bsHPrK/P) in solution by using several spectroscopic (namely, fluorescence and circular dichroism (CD)) and biophysical techniques (namely, small-angle X-ray-scattering (SAXS) and dynamic light-scattering (DLS)).

The Effect of Number of Arms on the Aggregation Behavior of Thermoresponsive Poly(N-isopropylacrylamide) Star Polymers.

The thermoresponsive nature of aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM) star polymers containing 2, 3, 4, and 6 arms has been investigated by turbidity, dynamic light scattering, rheology, and rheo-SALS. Simulations of the thermosensitive nature of the single star polymers have also been conducted. Some of the samples form aggregates even at temperatures significantly below the lower critical solution temperature (LCST) of PNIPAAM.

Prediction of solution properties and dynamics of RNAs by means of Brownian dynamics simulation of coarse-grained models: Ribosomal 5S RNA and phenylalanine transfer RNA.

Background: The possibility of validating biological macromolecules with locally disordered domains like RNA against solution properties is helpful to understand their function. In this work, we present a computational scheme for predicting global properties and mimicking the internal dynamics of RNA molecules in solution. A simple coarse-grained model with one bead per nucleotide and two types of intra-molecular interactions (elastic interactions and excluded volume interactions) is used to represent the RNA chain.

Application of recent advances in hydrodynamic methods for characterising mucins in solution.

Mucins are the primary macromolecular component of mucus--nature's natural lubricant--although they are poorly characterised heterogeneous substances. Recent advances in hydrodynamic methodology now offer the opportunity for gaining a better understanding of their solution properties. In this study a combination of such methods was used to provide increased understanding of a preparation of porcine intestinal mucin (PIM), MUC2 mucin, in terms of both heterogeneity and quantification of conformational flexibility.