Search results for "COPI"

Nonclassical crystallization in vivo et in vitro (I): Process-structure-property relationships of nanogranular biominerals.

2016

A distinct nanogranular fine structure is shared by a wealth of biominerals from several species, classes and taxa. This nanoscopic organization affects the properties and behavior of the biogenic ceramic material and confers on them attributes that are essential to their function. We present a set of structure-relationship properties that are rooted in the nanogranular organization and we propose that they rest on a common pathway of formation, a colloid-driven and hence nonclassical mode of crystallization. With this common modus operandi, we reveal the most fundamental and wide spread process-structure-property relationship in biominerals. With the recent increase in our understanding of…

GUARDARE PER LIVELLI: DAI SISTEMI AI COMPONENTI, DALLE PROPRIETÀ MACROSCOPICHE ALLE STRUTTURE MICROSCOPICHE

2008

Modelling Photoionisation in Isocytosine: Potential Formation of Longer‐Lived Excited State Cations in its Keto Form

2021

Abstract Studying the effects of UV and VUV radiation on non‐canonical DNA/RNA nucleobases allows us to compare how they release excess energy following absorption with respect to their canonical counterparts. This has attracted much research attention in recent years because of its likely influence on the origin of our genetic lexicon in prebiotic times. Here we present a CASSCF and XMS‐CASPT2 theoretical study of the photoionisation of non‐canonical pyrimidine nucleobase isocytosine in both its keto and enol tautomeric forms. We analyse their lowest energy cationic excited states including 2π+ , 2nO+ and 2nN+ and compare these to the corresponding electronic states in cytosine. Investigat…

The gold-sulfur interface at the nanoscale.

2012

Thiolate-protected gold surfaces and interfaces, relevant for self-assembled monolayers of organic molecules on gold, for passivated gold nanoclusters and for molecule-gold junctions, are archetypal systems in various fields of current nanoscience research, materials science, inorganic chemistry and surface science. Understanding this interface at the nanometre scale is essential for a wide range of potential applications for site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, functionalization of gold surfaces for sensing, molecular recognition and molecular electronics, and gold nanoparticle catalysis. During the past five years, considerable experimental …

Interaction of Doxorubicin with Polynucleotides. A Spectroscopic Study

2014

The interaction of doxorubicin (DX) with model polynucleotides poly(dG-dC)·poly(dG-dC) (polyGC), poly(dA-dT)·poly(dA-dT) (polyAT), and calf thymus DNA has been studied by several spectroscopic techniques in phosphate buffer aqueous solutions. UV-vis, circular dichroism, and fluorescence spectroscopic data confirm that intercalation is the prevailing mode of interaction, and also reveal that the interaction with AT-rich regions leads to the transfer of excitation energy to DX not previously documented in the literature. Moreover, the DX affinity for AT sites has been found to be on the same order of magnitude as that reported for GC sites.

Telechelic Star Polymers as Self-Assembling Units from the Molecular to the Macroscopic Scale

2012

By means of multiscale molecular simulations, we show that telechelic-star polymers are a simple, robust, and tunable system, which hierarchically self-assembles into soft-patchy particles and mechanically stabilizes selected, open crystalline structures. The self-aggregating patchy behavior can be fully controlled by the number of arms per star and by the fraction of attractive monomeric units at the free ends of the arms. Such self-assembled soft-patchy particles while forming, upon augmenting density, gel-like percolating networks, preserve properties as particle size, number, and arrangement of patches per particle. In particular, we demonstrate that the flexibility inherent in the soft…

Engineering thermal conductance using a two-dimensional phononic crystal

2014

Controlling thermal transport has become relevant in recent years. Traditionally, this control has been achieved by tuning the scattering of phonons by including various types of scattering centres in the material (nanoparticles, impurities, etc). Here we take another approach and demonstrate that one can also use coherent band structure effects to control phonon thermal conductance, with the help of periodically nanostructured phononic crystals. We perform the experiments at low temperatures below 1 K, which not only leads to negligible bulk phonon scattering, but also increases the wavelength of the dominant thermal phonons by more than two orders of magnitude compared to room temperature…

The second round of Critical Assessment of Automated Structure Determination of Proteins by NMR: CASD-NMR-2013

2015

The second round of the community-wide initiative Critical Assessment of automated Structure Determination of Proteins by NMR (CASD-NMR-2013) comprised ten blind target datasets, consisting of unprocessed spectral data, assigned chemical shift lists and unassigned NOESY peak and RDC lists, that were made available in both curated (i.e. manually refined) or un-curated (i.e. automatically generated) form. Ten structure calculation programs, using fully automated protocols only, generated a total of 164 three-dimensional structures (entries) for the ten targets, sometimes using both curated and un-curated lists to generate multiple entries for a single target. The accuracy of the entries could…

Interaction of Heparins and Dextran Sulfates with a Mesoscopic Protein Nanopore

2009

A mechanism of how polyanions influence the channel formed by Staphylococcus aureus alpha-hemolysin is described. We demonstrate that the probability of several types of polyanions to block the ion channel depends on the presence of divalent cations and the polyanion molecular weight and concentration. For heparins, a 10-fold increase in molecular weight decreases the half-maximal inhibitory concentration, IC(50), nearly 10(4)-fold. Dextran sulfates were less effective at blocking the channel. The polyanions are significantly more effective at reducing the conductance when added to the trans side of this channel. Lastly, the effectiveness of heparins on the channel conductance correlated wi…

Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

2015

Abstract Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N‐terminal segment containing heavy isotopes (2H, 13C, 15N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C‐terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N‐terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C‐terminal segment. QM/MM studies support th…