1D iron(II)-1,2,4-triazolic chains with spin crossover assembled from discrete trinuclear complexes

We report on a molecular cationic iron(II) complex with a 4-amino-1,2,4-triazole ligand and a tetraiodomercurate anion exhibiting an incomplete spin crossover (SCO). The complex exhibits an unusual disordered structure with...

Data-driven design of bi-selective OSDAs for intergrowth zeolites

Zeolites are inorganic materials with wide industrial applications due to their topological diversity. Tailoring confinement effects in zeolite pores, for instance by crystallizing intergrown frameworks, can improve their catalytic and transport properties, but controlling zeolite crystallization often relies on heuristics. In this work, we use computational simulations and data mining to design organic structure-directing agents (OSDAs) to favor the synthesis of intergrown zeolites. First, we propose design principles to identify OSDAs which are selective towards both end members of the disordered structure. Then, we mine a database of hundreds of thousands of zeolite-OSDA pairs and downselect OSDA candidates to synthesize known intergrowth zeolites such as CHA/AFX, MTT/TON, and BEC/ISV. The computationally designed OSDAs balance phase competition metrics and shape selectivity towards the frameworks, thus bypassing expensive dual-OSDA approaches typically used in the synthesis of intergrowths. Finally, we propose potential OSDAs to obtain hypothesized disordered frameworks such as AEI/SAV. This work may accelerate zeolite discovery through data-driven synthesis optimization and design.

The intrinsically disorderly story of Ki-67

Ki-67 is one of the most famous marker proteins used by histologists to identify proliferating cells. Indeed, over 30 000 articles referring to Ki-67 are listed on PubMed. Here, we review some of the current literature regarding the protein. Despite its clinical importance, our knowledge of the molecular biology and biochemistry of Ki-67 is far from complete, and its exact molecular function(s) remain enigmatic. Furthermore, reports describing Ki-67 function are often contradictory, and it has only recently become clear that this proliferation marker is itself dispensable for cell proliferation. We discuss the unusual organization of the protein and its mRNA and how they relate to various models for its function. In particular, we focus on ways in which the intrinsically disordered structure of Ki-67 might aid in the assembly of the still-mysterious mitotic chromosome periphery compartment by controlling liquid–liquid phase separation of nucleolar proteins and RNAs.

Mapping of the fibrinogen-binding site on the staphylocoagulase C-terminal repeat region

The N-terminus of S. aureus staphylocoagulase (SC) triggers activation of host prothrombin (ProT), and the SCProT* complex cleaves host fibrinogen (Fbg) to form fibrin (Fbn) deposits, a hallmark of SC-positive endocarditis. The C-terminal domain of the prototypical Newman D2 Tager 104 SC contains 1 pseudo-repeat (PR) and 7 repeats (R1R7) that bind Fbg/Fbn Fragment D (Frag D). This work defines affinities and stoichiometries of Frag D binding to single- and multi-repeat C-terminal constructs, using fluorescence equilibrium binding, NMR titration, Ala scanning, and native PAGE. Constructs containing PR and each single repeat bound Frag D with KD ~50 130 nM and a 1:1 stoichiometry, indicating a conserved binding site shared between PR and each repeat. NMR titration of PR-R7 with Frag D revealed that residues 22-49, bridging PR and R7, constituted the minimal peptide (MP) required for binding, corroborated by Ala scanning, and binding of labeled MP to Frag D. MP alignment with the PR-repeat and inter-repeat junctions identified conserved residues critical for binding. Labeled PR-(R1R7) bound Frag D with KD ~7 32 nM and stoichiometry of 1:5; and PR-R1R2R3, PR-R1R6R7, PR-R3R4R7, and PR-R3R6R7 competed with PR-(R1R7) for Frag D binding, with a 1:3 stoichiometry and KD ~7 42 nM. These findings are consistent with binding at the PR-R junctions with modest inter-repeat sequence variability. Circular dichroism of PR-R7 and PR-(R1R7) suggested a largely disordered structure and conformational flexibility, allowing binding of multiple fibrin(ogen) molecules. This property facilitates pathogen localization on host fibrin networks.

Получение нерастворимых в воде пленок из фиброина шелка, исследование их структуры и свойств

Silk fibroin is one of the promising natural polymers that already being used in medicine to forming of suture materials. The possibility of forming scaffolds in the form of films, sponges or gels for cell cultivation and transplantation will significantly expand the scope of application of this material in tissue engineering. The conditions for obtaining silk fibroin insoluble in water in the form of films were worked out. The structural transition on the surface of the films to a coarsely fragmented state after treatment of the films with methanol was demonstrated using optical microscopy. Using FTIR spectroscopy, the conformational transition of silk fibroin from the disordered structure of the untreated film to the β-folded structure was confirmed. Using the method of differential scanning calorimetry, the glass transition temperature of the native film was determined as 216 °C. The study of the mechanical properties of silk fibroin films in a liquid medium showed that their strength decreases and their elasticity increases by almost 15 times compared to tests of the same films in a dry state.