Chiral BINOL-phosphate assembled single hexagonal nanotube in aqueous solution for confined rearrangement acceleration

Creating microenvironments that mimic an enzyme's active site is a critical aspect of supramolecular confined catalysis. In this study, we employ the commonly used chiral 1,1'-bi-2-naphthol (BINOL) phosphates as subcomponents to construct supramolecular hollow nanotube in an aqueous medium through non-covalent intermolecular recognition and arrangement. The hexagonal nanotubular structure is characterized by various techniques, including X-ray, NMR, ESI-MS, AFM, and TEM, and is confirmed to exist in a homogeneous aqueous solution stably. The nanotube's length in solution depends on the concentration of chiral BINOL-phosphate as a monomer. Additionally, the assembled nanotube can accelerate the rate of the 3-aza-Cope rearrangement reaction by up to 85-fold due to the interior confinement effect. Based on the detailed kinetic and thermodynamic analyses, we propose that the chain-like substrates are constrained and pre-organized into a reactive chair-like conformation, which stabilizes the transition state of the reaction in the confined nanospace of the nanotube. Notably, due to the restricted conformer with less degrees of freedom, the entropic barrier is significantly reduced compared to the enthalpic barrier, resulting in a more pronounced acceleration effect.

Precise heteroatom doping determines aqueous solubility and self-assembly behaviors for polycyclic aromatic skeletons

Developing effective strategies to improve the hydrophilicity or aqueous solubility of hydrophobic molecular scaffolds is meaningful for both academic research and industrial applications. Herein, we demonstrate that stepwise and precise N/O heteroatoms doping on a polycyclic aromatic skeleton can gradually alter these structures from hydrophobic to hydrophilic, even resulting in excellent aqueous solubility. The Hansen solubility parameters (HSP) method shows that the three partial solubility parameters are closely related to N/O doping species, numbers and positions on the molecular panel. The hydrogen bonding solubility parameter indicates that the hydrogen bonding interactions between N/O doped molecules and water play a key role in enhancing hydrophilicity. Moreover, three optimized water-soluble molecules underwent a self-assembly process to form stable nanoparticles in water, thus facilitating better hydrogen bonding interactions disclosed by HSP calculations, NMR and single crystal X-ray analysis. These ensembles even show quasi-solid properties in water from NMR and luminescence perspectives.

Improved arachidonic acids production from the fungus Mortierella alpina by glutamate supplementation

The effect of various concentrations of glutamate on arachidonic acid (AA) production from Mortierella alpina in shaker flask culture was studied. Glutamate supplementation promoted Mortierella growth, accelerated substrate metabolism, and increased AA production, and a concentration of 0.8 g/l glutamate resulted in the greatest AA yield (1.41 g/l). In 10 l airlift stirred fermenter culture, AA yield in the cultures exposed to 0.8 g/l glutamate was also greater than that in the control (0.56 g/l).

Cell death unlikely contributes to taxol production in fungal elicitor-induced cell suspension cultures of Taxus chinensis

Cell suspension cultures of Taxus chinensis, with 20, 40 and 100 mg fungal elicitor l(-1) from Aspergillus niger, underwent rapid cell death after 24 h, which was about 2, 3.7 and 5-fold of that of the control. At the same time, Taxol production was increased, respectively, to about 5, 8 and 3-fold of that of the control. Inhibition of phenolics biosynthesis resulted in a 150% increase in cell death but a 54% decrease in Taxol production compared with 40 mg elicitor l(-1) alone. O2-free N2 inhibited cell death but had little effect on Taxol production as induced by 40 mg fungal elicitor l(-1).