Dynamics and Transport of Molecules in Polymer and Colloidal-Rod Networks

MRS Proceedings ◽

10.1557/proc-1060-ll04-05 ◽

2007 ◽

Vol 1060 ◽

Author(s):

Kyongok Kang

Keyword(s):

Electric Field ◽

Electrostatic Interactions ◽

Polymer Network ◽

Mesh Size ◽

Limited Range ◽

Correlation Spectroscopy ◽

Relaxation Dynamics ◽

Screening Length ◽

Cholesteric Phase ◽

Hydrodynamic Screening

ABSTRACTRe-orientational dynamics of liquid crystal molecules in a polymer network subjected to an electric field is studied by means of light diffraction [1]. When the optical pitch of the electric-field induced cholesteric phase is small compared to the optical wavelength of light, dynamic light scattering (DLS) can be performed to extract the relaxation dynamics of the chiral nematic molecules in the presence of the polymer network. Intriguingly, the reactive mesogenic type of polymer network exhibits a confinement effect, which can be probed within the limited range of scattering angles that comply with the structural correlation length in the system [2].Diffusive mass transport of molecules through a rod network can be studied via fluorescence correlation spectroscopy (FCS) and DLS. Long time self-diffusion of tracer spheres (silica and proteins) in isotropic and nematic colloidal-rod networks (fd-viruses) is systematically studied for various tracer-sphere sizes as compared to the mesh size of the network [3]. In addition, by varying the salt concentration, the relative contribution of electrostatic interactions can be varied. A theory is developed where the diffusion coefficient is expressed in terms of the hydrodynamic screening length of the highly entangled rod-network. The hydrodynamic screening length of rod networks is extracted from diffusion data as a function of the rod concentration both for isotropic and nematic networks [4-5].

Download Full-text

Addressing a lattice of rotatable molecular dipoles with the electric field of an STM tip

Physical Chemistry Chemical Physics ◽

10.1039/d0cp06146h ◽

2021 ◽

Vol 23 (8) ◽

pp. 4874-4881

Author(s):

Timo Frauhammer ◽

Lukas Gerhard ◽

Kevin Edelmann ◽

Marcin Lindner ◽

Michal Valášek ◽

...

Keyword(s):

Electric Field ◽

Electrostatic Interactions ◽

Head Groups

Electrostatic interactions within a lattice of freestanding rotatable head groups mounted on tripodal molecular platforms.

Download Full-text

Insight into Inhibitor Binding in the Eukaryotic Proteasome: Computations of the 20S CP

International Journal of Molecular Sciences ◽

10.3390/ijms19123858 ◽

2018 ◽

Vol 19 (12) ◽

pp. 3858

Author(s):

Milan Hodošček ◽

Nadia Elghobashi-Meinhardt

Keyword(s):

Electrostatic Interactions ◽

Active Sites ◽

Sampling Period ◽

Md Simulations ◽

Structural Features ◽

Relaxation Dynamics ◽

Inhibitor Binding ◽

Computational Analyses ◽

Insight Into ◽

Proteolytic Chamber

A combination of molecular dynamics (MD) simulations and computational analyses uncovers structural features that may influence substrate passage and exposure to the active sites within the proteolytic chamber of the 20S proteasome core particle (CP). MD simulations of the CP reveal relaxation dynamics in which the CP slowly contracts over the 54 ns sampling period. MD simulations of the SyringolinA (SylA) inhibitor within the proteolytic B 1 ring chamber of the CP indicate that favorable van der Waals and electrostatic interactions account for the predominant association of the inhibitor with the walls of the proteolytic chamber. The time scale required for the inhibitor to travel from the center of the proteolytic chamber to the chamber wall is on the order of 4 ns, accompanied by an average energetic stabilization of approximately −20 kcal/mol.

Download Full-text

Small Oligonucleotides Detection in Three-Dimensional Polymer Network of DNA-PEG Hydrogels

10.20944/preprints202106.0264.v1 ◽

2021 ◽

Author(s):

Alessia Mazzarotta ◽

Tania Maristella Caputo ◽

Luca Raiola ◽

Edmondo Battista ◽

Paolo Antonio Netti ◽

...

Keyword(s):

Polymer Network ◽

Three Dimensional ◽

Mesh Size ◽

Short Oligonucleotide ◽

Dna Oligonucleotides ◽

Hydrogel Network ◽

Displacement Assay ◽

Oligonucleotide Detection ◽

Biomolecules Detection ◽

And Diffusion

The control of the three-dimensional (3D) polymer network structure is important for permselective materials when specific biomolecules detection is needed. Here we investigate conditions to obtain a tailored hydrogel network that combine both molecular filtering and molecular capture capabilities for biosensing applications. Along this line short oligonucleotide detection in a displacement assay is set within PEGDA hydrogels synthetized by UV radical photopolymerization. To provide insights on the molecular filter capability, diffusion studies of several probes (sulforhodamine G and dextrans) with different hydrodynamic radii were carried out using NMR technique. Moreover, fluorometric analyses of hybridization of DNA oligonucleotides inside PEGDA-hydrogels shed light on the mechanisms of recognition in 3D, highlighting that mesh size and crowding effect greatly impact of hybridization mechanism onto polymer network. Finally, we found the best probe density and diffusion transport conditions to allow the specific oligonucleotide capture and detection inside PEGDA-hydrogels for oligonucleotide detection and the filtering out of higher molecular weight molecules.

Download Full-text

Single-Macromolecular Level Imaging of a Hydrogel Structure

10.33774/chemrxiv-2021-x1s5k ◽

2021 ◽

Author(s):

Ryuji Kiyama ◽

Takayuki Nonoyama ◽

Sedlacik Tomas ◽

Hiroshi Jinnai ◽

Jian Ping Gong

Keyword(s):

Polymer Network ◽

Mesh Size ◽

Fixation Method ◽

Gel Properties ◽

Cell Scaffolds ◽

Transmission Electron ◽

Hydrogel Network ◽

Network Observation ◽

Surface Network ◽

First Time

Hydrogels are promising materials for several applications, including cell scaffolds and artificial load-bearing substitutes (cartilages, ligaments, tendons, etc.). Direct observation of the nanoscale polymer network of hydrogels is essential in understanding its properties. However, imaging of individual network strands at the molecular level is not achieved yet due to the lack of suitable methods. Herein, for the first time, we developed a novel mineral-staining method and network fixation method for transmission electron microscopy observation to visualize the hydrogel network in its unperturbed conformation with nanometer resolution. Surface network observation indicates that the length of surface dangling chains, which play a major role in friction and wetting, can be estimated from the gel mesh size. Moreover, bulk observations reveals a hierarchical formation mechanism of gel heterogeneity. These observations have the great potential to advance gel science by providing comprehensive perspective that link bulk gel properties with nanoscale.

Download Full-text

Separation of water–ethanol solutions with carbon nanotubes and electric fields

Physical Chemistry Chemical Physics ◽

10.1039/c6cp06731j ◽

2016 ◽

Vol 18 (48) ◽

pp. 33310-33319 ◽

Cited By ~ 19

Author(s):

Winarto Winarto ◽

Daisuke Takaiwa ◽

Eiji Yamamoto ◽

Kenji Yasuoka

Keyword(s):

Carbon Nanotubes ◽

Electric Field ◽

Electric Fields ◽

Electrostatic Interactions ◽

Water Molecules ◽

Ordered Structure

Under an electric field, water prefers to fill CNTs over ethanol, and electrostatic interactions within the ordered structure of the water molecules determine the separation effects.

Download Full-text