Quassinoids: Phytochemistry and antitumor prospect.

Quassinoids, originating from the oxidative degradation of tetracyclic tirucallane triterpene, are a diverse class of secondary metabolites identifying from nature mostly in Simaroubaceae family. The crucial pharmacological activities and structural complexity of quassinoids have long fascinated scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. In the past few decades, 482 quassinoids, assigned to 6 skeletons, have been isolated and identified from plants. The names, classes, molecular formula, and plant sources of these secondary metabolites are collated here. This review will be a detailed update of the naturally occurring quassinoids reported from the plant kingdom, providing an in-depth discussion of their diversity, antitumor activities, structure-activity relationship.

Electronic stopping power for slow ions in the low-hardness semimetal HgTe using first-principles calculations.

The electronic stopping power for low-velocity ions (including protons, [Formula: see text]-particles, and [Formula: see text]) is investigated in a novel semimetal HgTe system, where the data are obtained with the aid of Ehrenfest dynamics combined with time-dependent density functional theory. For the light projectile ions (protons and [Formula: see text]-particles), the linear and nonlinear behaviors of electronic stopping power in three different channel directions are analyzed in detail. In the case where the projectile ion is a proton, the linear results for the threshold velocity are correlated with an indirect band gap; the direction of the electronic stopping power depends on the radial drag force, the channeling electronic density and the trapped charge. More notably, we report an interesting channel-geometry fact, i.e. that the electronic stopping power of HgTe is powerfully modulated by the impact parameters. The parallel off-center tracks increase the electronic stopping power, making it more consistent with the SRIM data. In the case of an [Formula: see text]-particle as the projectile ion, nonlinear behavior that varies with velocity can be ascribed to the charge transfer, which is another mode of energy dissipation. In addition, when the slightly heavier projectile [Formula: see text] travels through the medium HgTe, the projectile [Formula: see text] can capture more free charges than the protons and [Formula: see text]-particles under the same circumstances. Especially, for the projectile in the off-channel, the electronic stopping power is close to the SRIM data with the decrease of the impact parameter. These results extend the study of radiation damage to a new field of materials.

[Synergistic regulation of the erythroid differentiation of K562 cells by KLF1 and KLF9].

Krüppel-like factors (KLFs) regulate diverse physiological processes such as the differentiation and development of red blood cells. However, it remains unclear whether KLFs exhibit synergistic regulatory effects. Transcriptomic data from our previous study showed that KLF1 and KLF9 expression was significantly higher in differentiated red blood cells than in hematopoietic stem cells. In the present study, we manipulated KLF1 and KLP9 gene expression by overexpressing or knocking down KLF1 and KLF9 in K562 cells and revealed a positive correlation between the expression of KLF1 and KLF9; their co-expression can significantly promote erythroid differentiation and specifically enhance ß-globin gene expression. Further, we analyzed the transcriptome data of K562 cells with altered KLF1/KLF9 levels and found that KLF1 and KLF9 synergistically regulated erythroid differentiation through the PI3K-Akt and FoxO signaling pathways. KLF1 and KLF9 may exert this synergistic effect through FOS, TF, and IL8 in K562 cells. We have provided evidence that KLF1 and KLF9 play a synergistic role in regulating erythroid differentiation.

[Role of chromatin conformation in eukaryotic gene regulation].

Gene expression in eukaryotes is regulated at multiple levels, which involves various cis-regulatory elements and trans-acting factors at transcriptional level. In addition, DNA methylation and histone modifications also play crucial roles in epigenetic regulation of eukaryotic genes. It is pivotal for evaluating the regulation of gene expression to understand the structural properties and spatial organization of chromatin at 3-D level. The dynamic alternations of chromatin conformation can either activate gene expression by facilitating the interactions between enhancers or other cis-regulatory elements and their target genes or suppress gene expression by blocking the interactions due to steric hindrance. Although the precise molecular mechanisms underlying the gene regulation via conformational changes of chromatin remain obscure, epigenetic studies including histone modification, nucleosome positioning, chromosome territories as well as chromatin interactions, have provided accumulating evidence to demonstrate the significance of chromatin conformation in eukaryotic gene regulation. Here, we reviewed the recent advances on the role of dynamic alterations of chromatin in gene regulation , which occur at different levels from the primary structure to three dimensional conformation.

Contribution of the conserved A16Leu to insulin foldability.

Contributions of the evolutionarily conserved A16Leu and B17Leu to insulin foldability were characterized by evaluating folding properties of single-chain insulin analogs. The results showed A16Leu had much more significant effects on the foldability of insulin than B17Leu.