Solvent-mediated gel formation, hierarchical structures, and rheological properties of organogels.

We report the formation of solvent-mediated gels as well as their hierarchical structures and rheological properties. The gelator used is a hybrid with a molecular structure of cholesterol-polyoxometalate-cholesterol, in which the cholesterol dissolves well in toluene and N,N-dimethylformamide (DMF), whereas the polyoxometalate cluster dissolves only in DMF. These solubility differences enable the gelator to form thermally reversible supramolecular organogels by mixing solvents of toluene and DMF when the volume fraction, ftol, of toluene is larger than 85.7 v/v%. We found a V-shaped correlation between the gelation times, tgel and ftol: tgel decreases from 1300 min to 2 min when ftol increases from 85.7 v/v% to 90.0 v/v%. It then increases from 2 min to 5800 min when ftol further increases from 90.0 v/v% to 100.0 v/v%. We observed ribbon-like self-assembled structures in the gels as well as a structural evolution from rigid and straight ribbons to twistable ones from ftol=85.7 v/v% to ftol=100.0 v/v%. These ribbons constitute two three-dimensional (3D) gel networks: one is constructed via physical connection of the rigid and straight ribbon, and the other is built up from ribbons splitting and intertwining. The latter has a better 3D gel network that offers improved rheological properties. Fundamentally, this solvent-mediated approach regulates the balance between solubility and insolubility of this gelator in the mixing solvents. It also provides a new method for the preparation of organogels.

Polyoxometalate-biomolecule conjugates: a new approach to create hybrid drugs for cancer therapeutics.

Some polyoxometalate (POM) clusters have demonstrated attractive anticancer properties. Unfortunately, their cytotoxicity upon normal cell is one of fateful side effects obstructing their further clinic application as inorganic drugs. In this communication, we report a new approach to create hybrid drugs potentially for cancer therapeutics. At first, the POM cluster bioconjugates were created by attaching the bioactive ligands on an amine grafted POM via simple amidation reaction. The cytotoxicity study with breast cancer cells (MCF-7 and MDA-MB-231) and non-cancerous breast epithelial cell (MCF-10A) showed that rationally selected ligands with cancer-cell targeting ability on POM-biomolecule conjugates can impart enhanced anti-tumor activity and selectivity, thus representing a new concept to develop novel POM-biomolecule hybrid drugs with the potential synergistic effect: increased bioactivity and lower side effect.

Chromosome-level genome assembly and resequencing of camphor tree (Cinnamomum camphora) provides insight into phylogeny and diversification of terpenoid and triglyceride biosynthesis of Cinnamomum.

Cinnamomum species attract attentions owing to their scents, medicinal properties, and ambiguous relationship in the phylogenetic tree. Here, we report a high-quality genome assembly of Cinnamomum camphora, based on which two whole-genome duplication (WGD) events were detected in the C. camphora genome: one was shared with Magnoliales, and the other was unique to Lauraceae. Phylogenetic analyses illustrated that Lauraceae species formed a compact sister clade to the eudicots. We then performed whole-genome resequencing on 24 Cinnamomum species native to China, and the results showed that the topology of Cinnamomum species was not entirely consistent with morphological classification. The rise and molecular basis of chemodiversity in Cinnamomum were also fascinating issues. In this study, six chemotypes were classified and six main terpenoids were identified as major contributors of chemodiversity in C. camphora by the principal component analysis. Through in vitro assays and subcellular localization analyses, we identified two key terpene synthase (TPS) genes (CcTPS16 and CcTPS54), the products of which were characterized to catalyze the biosynthesis of two uppermost volatiles (i.e. 1,8-cineole and (iso)nerolidol), respectively, and meditate the generation of two chemotypes by transcriptional regulation and compartmentalization. Additionally, the pathway of medium-chain triglyceride (MCT) biosynthesis in Lauraceae was investigated for the first time. Synteny analysis suggested that the divergent synthesis of MCT and long-chain triglyceride (LCT) in Lauraceae kernels was probably controlled by specific medium-chain fatty acyl-ACP thioesterase (FatB), type-B lysophosphatidic acid acyltransferase (type-B LPAAT), and diacylglycerol acyltransferase 2b (DGAT 2b) isoforms during co-evolution with retentions or deletions in the genome.

Using a facile experimental manipulation to fabricate and tune a polyoxometalate-cholesterol hybrid material.

In this work, we describe how the toluene and DMF addition order influences the gelation behaviors and supramolecular structures of a self-assembled polyoxometalate-cholesterol hybrid. Morphological studies of the dried xerogel samples were performed with transmission electron microscopy and atomic force microscopy, revealing that the order of solvent addition directed the self-assembly of polyoxometalate-cholesterol hybrids toward the formation of organogels with different supramolecular structures. In the case of organogel 1, which was formed by adding DMF dropwise into a hybrid-containing toluene solution, the characteristic organogel morphology contained a three-dimensional fibrous network structure. Meanwhile, organogel 2, which was prepared by adding toluene dropwise into a hybrid-containing DMF solution, had a supramolecular structure made up of short ribbons. Based on these results, a mechanism is proposed to illustrate the distinctly different self-assembly mechanisms of hybrid molecules in the formation of organogels 1 and 2. Importantly, the order of solvent addition plays a central role in the aggregation process. This study provides a rational method for the construction of supramolecular soft materials, and can be extended to other self-assembled systems.