menthifolia

Monarda fistulosa Linnaeuswild bergamot;wild horsemint;purple beebalm;Oswego-teafistulosaDistrict de Medicine Hat. Ruisseau des Pieganes. 12 milles au nord d'Orion.Platieres du ruissea

Structure and Shape Effects of Molecular Glue on Supramolecular Tubulin Assemblies

The possibility to arrange biological molecules into ordered nanostructures is an important issue in nano- and biotechnology. Nature offers a wide range of molecular “bricks” (<i>e.g.</i>, proteins, oligonucleotides, <i>etc</i>.) that spontaneously assemble into more complex hierarchical systems with unique functionalities. Such molecular building blocks can be also used for the construction of nanomaterials with peculiar properties (<i>e.g.</i>, DNA origami). In some cases, molecular glues able to bind biomolecules and to induce their assembly can be used to control the final structure and properties in a convenient way. Here we provide molecular-level description of how molecular glues designed to stick to the surface of microtubules (MTs) can control and transform the α/β-tubulin assembly upon temperature decreasing. By means of all-atom molecular dynamics (MD) simulations, we compared the adhesion to the MT surface of three molecular glues bearing the same guanidinium ion surface adhesive groups, but having different architecture, <i>i.e.</i>, linear or dendritic backbone. Our evidence demonstrates that the adhesive properties of the different molecular glues are dependent on the shape they assume in solution. In particular, adhesion data from our MD simulations explain how globular- or linear-like molecular glues respectively stabilize MTs or transform them into a well-defined array of α/β-tubulin rings at 15 °C, where MTs naturally depolymerize. The comprehension of the MT transformation mechanism provides a useful rationale for designing <i>ad hoc</i> molecular glues to obtain ordered protein nanostructures from different biological materials

Dynamic or Nondynamic? Helical Trajectory in Hexabenzocoronene Nanotubes Biased by a Detachable Chiral Auxiliary

When ether vapor was allowed to diffuse into a CH₂Cl₂ solution of an enantiomer of a hexa-<i>peri</i>-hexabenzocoronene (HBC) derivative carrying a chiral (BINAP)­Pt­(II)-appended coordination metallacycle (HBC^Py_{[(<i>R</i>)‑Pt]} or HBC^Py_{[(<i>S</i>)‑Pt]}), screw-sense-selective assembly took place to give optically active nanotubes (NT^Py_{[(<i>R</i>)‑Pt]} or NT^Py_{[(<i>S</i>)‑Pt]}) with helical chirality, which were enriched in either left-handed (<i>M</i>)-NT^Py_{[(<i>R</i>)‑Pt]} or right-handed (<i>P</i>)-NT^Py_{[(<i>S</i>)‑Pt]}, depending on the absolute configuration of the (BINAP)­Pt­(II) pendant. When MeOH was used instead of ether for the vapor-diffusion-induced assembly, nanocoils formed along with the nanotubes. As determined by scanning electron microscopy, the diastereomeric excess of the nanocoils was 60% (80:20 diastereomeric ratio). Removal of the (BINAP)­Pt­(II) pendants from NT^Py_{[(<i>R</i>)‑Pt]} or NT^Py_{[(<i>S</i>)‑Pt]} with ethylenediamine yielded metal-free nanotubes (NT^Py) that remained optically active even upon heating without any change in the circular dichroism spectral profile. No helical inversion took place when NT^Py derived from HBC^Py_{[(<i>R</i>)‑Pt]} or HBC^Py_{[(<i>S</i>)‑Pt]} was allowed to complex with (BINAP)­Pt­(II) with an absolute configuration opposite to the original one

Asymmetry in the function and dynamics of the cytosolic group II chaperonin CCT/TRiC

<div><p>The eukaryotic group II chaperonin, the chaperonin-containing t-complex polypeptide 1 (CCT), plays an important role in cytosolic proteostasis. It has been estimated that as much as 10% of cytosolic proteins interact with CCT during their folding process. CCT is composed of 8 different paralogous subunits. Due to its complicated structure, molecular and biochemical investigations of CCT have been difficult. In this study, we constructed an expression system for CCT from a thermophilic fungus, <i>Chaetomium thermophilum</i> (CtCCT), by using <i>E</i>. <i>coli</i> as a host. As expected, we obtained recombinant CtCCT with a relatively high yield, and it exhibited fairly high thermal stability. We showed the advantages of the overproduction system by characterizing CtCCT variants containing ATPase-deficient subunits. For diffracted X-ray tracking experiment, we removed all surface exposed cysteine residues, and added cysteine residues at the tip of helical protrusions of selected two subunits. Gold nanocrystals were attached onto CtCCTs via gold-thiol bonds and applied for the analysis by diffracted X-ray tracking. Irrespective of the locations of cysteines, it was shown that ATP binding induces tilting motion followed by rotational motion in the CtCCT molecule, like the archaeal group II chaperonins. When gold nanocrystals were attached onto two subunits in the high ATPase activity hemisphere, the CtCCT complex exhibited a fairly rapid response to the motion. In contrast, the response of CtCCT, which had gold nanocrystals attached to the low-activity hemisphere, was slow. These results clearly support the possibility that ATP-dependent conformational change starts with the high-affinity hemisphere and progresses to the low-affinity hemisphere.</p></div