Ion Transport Study in CS: POZ Based Polymer Membrane Electrolytes Using Trukhan Model

In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (Rb) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σdc) patterns, considerations on the ion transport models of Arrhenius and Vogel–Tammann–Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (Mi) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (Mi) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδmax). The Einstein–Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10−5 cm2/s, 3.4 × 1015 cm−3, and 1.2 × 10−4 cm2/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase.

Cell cycle– and genomic distance–dependent dynamics of a discrete chromosomal region

In contrast to the well-studied condensation and folding of chromosomes during mitosis, their dynamics during interphase are less understood. We deployed a CRISPR-based DNA imaging system to track the dynamics of genomic loci situated kilobases to megabases apart on a single chromosome. Two distinct modes of dynamics were resolved: local movements as well as ones that might reflect translational movements of the entire domain within the nucleoplasmic space. The magnitude of both of these modes of movements increased from early to late G1, whereas the translational movements were reduced in early S phase. The local fluctuations decreased slightly in early S and more markedly in mid-late S. These newly observed movements and their cell cycle dependence suggest the existence of a hitherto unrecognized compaction–relaxation dynamic of the interphase chromosome fiber, operating concurrently with changes in the extent of overall movements of loci in the 4D genome.

Dinuclear CoIIYIIIvs. tetranuclear CoII2YIII2 complexes: the effect of increasing molecular size on magnetic anisotropy and relaxation dynamics

The lower distortion of the CoII ions in the new tetranuclear CoII2YIII2 complex leads to a larger magnetic anisotropy than in its CoIIYIII counterparts, whereas its larger size and flexibility seem to promote a faster relaxation dynamic.

CRISPR-Based DNA Imaging in Living Cells Reveals Cell Cycle-Dependent Chromosome Dynamics

SUMMARYIn contrast to the well-studied condensation and folding of chromosomes during mitosis, their dynamics in interphase are less understood. We developed a sensitive, multicolor system, CRISPR-Sirius, allowing the real-time tracking of the dynamics of chromosomal loci. We tracked loci kilobases to megabases apart and found significant variation in the inter-locus distances of each pair, indicating differing degrees of DNA contortion. We resolved two distinct modes of dynamics of loci: saltatory local movements as well as translational movements of the domain. The magnitude of both of these modes of movements increased from early to late G1, whereas the translational movements were reduced in early S. The local fluctuations decreased slightly in early S and more markedly in mid-late S. These newly observed movements and their cell cycle-dependence are indicative of a hitherto unrecognized compaction-relaxation dynamic of the chromosomal fiber operating concurrently with changes in the extent of observed genomic domain movements.IN BRIEFDistinct chromosome folding and dynamics during cell cycle progression were dissected by CRISPR-Sirius DNA imaging in living cells.HIGHLIGHTSCRISPR-Sirius allows tracking of pairs of chromosomal loci having kilobase to megabase inter-locus distancesPair-wise tracking of loci allows measurement of both local and domain dynamicsChromosomal fiber relaxation is positively correlated with local dynamicsGenomic region size contributes to local and domain movementsDistinct chromosome dynamics were uncovered during cell cycle progression in interphase

Spectroscopic insight into molecular fluctuations and phase stability of nematic composites containing gold nanoparticles or carbon nanotubes

We demonstrate the fundamental difference between molecular dopants and nanoparticles in their impact on the molecular relaxation dynamic of nematic liquid crystals.