Asymmetric counteranion-directed photoredox catalysis.

Photoredox catalysis enables distinctive and broadly applicable chemical reactions, but controlling their selectivity has proven to be difficult. The pursuit of enantioselectivity is a particularly daunting challenge, arguably because of the high energy of the activated radical (ion) intermediates, and previous approaches have invariably required pairing of the photoredox catalytic cycle with an additional activation mode for asymmetric induction. A potential solution for photoredox reactions proceeding via radical ions would be catalytic pairing with enantiopure counterions. However, although attempts toward this approach have been described, high selectivity has not yet been accomplished. Here we report a potentially general solution to radical cation-based asymmetric photoredox catalysis. We describe organic salts, featuring confined imidodiphosphorimidate counteranions that catalyze highly enantioselective [2+2]-cross cycloadditions of styrenes.

Post-transcriptional regulation of MMP2 mRNA by its interaction with miR-20a and Nucleolin in breast cancer cell lines.

Matrix-metalloproteinase-2 (MMP2) is a foremost MMP, governing invasion of breast cancer cells during metastasis. miR-20a was reported to induce mesenchymal to epithelial transition in MDA-MB-231 cells and its endogenous expression varies directly with invasiveness of breast cancer cells. The inverse and direct correlation of invasiveness with miR-20a and Nucleolin respectively led us to study the post-transcriptional regulation of MMP2 by miR-20a and mRNA stabilizing protein, Nucleolin. Thus, understanding the mechanism of its regulation will enable modification of the invasion potential. MMP2 was found to be higher in MDA-MB-231 than MCF-7 cells both at RNA and protein levels. RNA-protein co-immunoprecipitation assay with Argonaute 2 revealed that MMP2 undergoes miRNA-mediated post-transcriptional regulation. miR-20a decreased MMP2 expression as well as its enzymatic activity as found by zymogram assay. Reporter assay showed that miR-20a directly binds to its putative binding site in MMP2 3'-UTR as per in silico prediction. miR-20a additionally impeded MMP2 mRNA stability, and binding of stabilizing trans-factor Nucleolin to its 3'-UTR was confirmed by RNA-protein co-immunoprecipitation assay. Partial down-regulation of Nucleolin by Si-RNA resulted in the downregulation of MMP2 and Nucleolin over-expression rescued the inhibitory effect of miR-20a on MMP2 expression. Delineating the mechanism of post-transcriptional regulation of MMP2, two of its potent regulators, miR-20a and Nucleolin were identified. It was established for the first time that MMP2 is a direct target of miR-20a. The results also elucidated that Nucleolin binds to MMP2 3' UTR and its abundance affects MMP2 expression.

Effects of menstrual characteristics, symptoms and hygiene-related practices on menstrual experience: A comparative study between freeholder and tenant adolescent schoolgirls of North 24 Parganas, West Bengal, India.

Adolescence is a significant event in woman's life when the process of menstruation occurs with several physical, mental and physiological developments. Menstrual experience of women is largely determined by environmental factors occurring during this period. In India, disparities in numerous factors result in different menstrual characteristics, menstruation-related symptoms and menstrual hygiene-related practices. However, the effect of residential status on the menstrual characteristics of adolescent girls is still unknown. In this context, the present study attempted to explore the variation in overall socio-economic condition and menstrual experience of tenant adolescent girls in comparison to freeholder adolescent girls. A well-structured questionnaire was used to collect information from 167 freeholder and 133 tenant adolescent schoolgirls on socio-economic and menstrual characteristics, menstruation-related symptoms and menstrual hygiene-related practices. Results showed that differences existed for these traits between freeholder and tenant adolescents. The key factors behind unsatisfied menstrual experience of tenant adolescent girls were lack of privacy, unsuitable sanitation facilities and use of cloth as preferred absorbent.

Strong and Confined Acids Control Five Stereogenic Centers in Catalytic Asymmetric Diels-Alder Reactions of Cyclohexadienones with Cyclopentadiene.

We describe a highly enantioselective Diels-Alder reaction of cross-conjugated cyclohexadienones with cyclopentadiene, in which five stereocenters are effectively controlled by a strongly acidic and confined imidodiphosphorimidate catalyst. Our approach provides tricyclic products in excellent stereoselectivity. We also report methods to convert the obtained products into useful intermediates and a computational study that aids in gaining deeper insight into the reaction mechanism and origin of stereoselectivity.

Involvement of HuR in the serum starvation induced autophagy through regulation of Beclin1 in breast cancer cell-line, MCF-7.

Starvation is a cellular stress that induces autophagy, a conserved cellular self-digestion mechanism that allows cells to degrade and recycle damaged proteins and organelles. The present study illustrated that during serum deprivation, Beclin1, a crucial gene that is essential for autophagosome formation in autophagy, gets controlled post-transcriptionally in breast cancer cell-line MCF-7. RNA affinity chromatography and co-immunoprecipitation confirmed the association of HuR with 3'-UTR of beclin1 mRNA. After cytosolic translocation, HuR enhances beclin1 protein synthesis in response to serum starvation by enhancing the association of beclin1 mRNA to the polysomes. Partial silencing of HuR resulted in reduction of beclin1 expression both at mRNA and protein levels, which in turn decreased starvation-induced autophagic flux. Thus, in conclusion, fine-tuning of beclin1 gene expression at post-transcriptional level by HuR is one of the key regulatory mechanisms of starvation induced autophagy in breast cancer cell-line, MCF-7.

Establishment of twist-1 and TGFBR2 as direct targets of microRNA-20a in mesenchymal to epithelial transition of breast cancer cell-line MDA-MB-231.

Messenchymal to epithelial transition (MET) is a significant physiological phenomenon involved in embryogenesis and cancer. This study aims at investigating the mechanism of microRNA-20a (miR-20a) mediated regulation of mesenchymal to epithelial transition and identification of its direct target genes in breast cancer cell-line, MDA-MB-231. Reduced migratory and invasive property, altered cellular morphology along with reduced capability for attachment to basement membrane was acquired by over-expression of miR-20a in invasive MDA-MB-231 cell-line initially expressing low level of this micro-RNA, indicating direct correlation between abundance of miR-20a and metastatic property. The switch from mesenchymal to epithelial cells mediated by miR-20a involved post-transcriptional down-regulation of twist1, which in turn controls downstream epithelial markers like E-cadherin, claudin and mesenchymal markers like N-cadherin, fibronectin, the crucial players of mesenchymal to epithelial transition (MET). Furthermore, another key component, TGF-ß and one of its receptors (TGFBR2) were found to be down-regulated by miR-20a. Additionally, reporter assay established that post-transcriptional down-regulation of TGFBR2 occurred through direct binding of miR-20a to its 3'UTR, thus abrogating the TGF-ß signaling pathway resulting in inhibition of MET. Delineating the underlying molecular mechanism of miR-20a-mediated MET and defining the target genes will help us to introduce a miRNA-mediated effective therapeutic strategy against breast cancer.

Withaferin A induced impaired autophagy and unfolded protein response in human breast cancer cell-lines MCF-7 and MDA-MB-231.

The autophagy-lysosome pathway and the ubiquitin-proteasome systems are the two major routes for eukaryotic intracellular protein clearance. Cancerous cells often display elevated protein synthesis and byproduct disposal, thus, inhibition of the protein degradation pathways became an emerging approach for cancer therapy. The present study revealed that withaferin-A (WA), the biologically active withanolide derived from Withania somnifera, initially induced formation of autophagosomes in human breast cancer cell-lines, MCF-7 and MDA-MB-231. WA treatment elevated the levels of autophagic substrate p62/SQSTM1 (p62) and both LC3-II and LC3-I (microtubule-associated protein 2 light chain 3) and simultaneously reduced the upstream autophagy markers like beclin-1 and ATG5-ATG12 complex, which indicate accumulation of autophagosomes in the cells. WA induced disruption of microtubular network through inhibition of tubulin polymerization and its hyper-acetylation, thus prevent the formation of autolysosome (by merging of autophagosomes with lysosomes) and its recycling process, leading to incomplete autophagy. Further, WA caused ER (Endoplasmic Reticulum) stress, which is evident from the activation of ER-related caspase-4 and increased levels of ER stress marker proteins. Thus, these findings altogether indicate that WA mediated inhibition of proteasomal degradation system and perturbation of autophagy, i.e. suppression of both the intracellular degradation systems caused accumulation of ubiquitinated proteins, which in turn led to unfolded protein response and ER stress mediated proteotoxicity in human breast cancer cell-lines, MCF-7 and MDA-MB-231.

Asymmetric Catalysis of the Carbonyl-Amine Condensation: Kinetic Resolution of Primary Amines.

A Brønsted acid catalyzed kinetic resolution of primary amines is described that is based on the condensation between an amine and a carbonyl compound. 1,3-Diketones react with racemic α-branched amines to furnish the corresponding enantioenriched enaminone and recovered starting material. Good to excellent enantioselectivity was observed with both aromatic and aliphatic primary amines. This process represents the first small-molecule catalyzed kinetic resolution of aliphatic amines.

Withaferin A Induces ROS-Mediated Paraptosis in Human Breast Cancer Cell-Lines MCF-7 and MDA-MB-231.

Advancement in cancer therapy requires a better understanding of the detailed mechanisms that induce death in cancer cells. Besides apoptosis, themode of other types of cell death has been increasingly recognized in response to therapy. Paraptosis is a non-apoptotic alternative form of programmed cell death, morphologically) distinct from apoptosis and autophagy. In the present study, Withaferin-A (WA) induced hyperpolarization of mitochondrial membrane potential and formation of many cytoplasmic vesicles. This was due to progressive swelling and fusion of mitochondria and dilation of endoplasmic reticulum (ER), forming large vacuolar structures that eventually filled the cytoplasm in human breast cancer cell-lines MCF-7 and MDA-MB-231. The level of indigenous paraptosis inhibitor, Alix/AIP-1 (Actin Interacting Protein-1) was down-regulated by WA treatment. Additionally, prevention of WA-induced cell death and vacuolation on co-treatment with protein-synthesis inhibitor indicated requirement of de-novo protein synthesis. Co-treatment with apoptosis inhibitor resulted in significant augmentation of WA-induced death in MCF-7 cells, while partial inhibition in MDA-MB-231 cells; implyingthat apoptosis was not solely responsible for the process.WA-mediated cytoplasmic vacuolationcould not be prevented by autophagy inhibitor wortmanninas well, claiming this process to be a non-autophagic one. Early induction of ROS (Reactive Oxygen Species)by WA in both the cell-lines was observed. ROS inhibitorabrogated the effect of WA on: cell-death, expression of proliferation-associated factor andER-stress related proteins,splicing of XBP-1 (X Box Binding Protein-1) mRNA and formation of paraptotic vacuoles.All these results conclusively indicate thatWA induces deathin bothMCF-7 and MDA-MB-231 cell lines byROS-mediated paraptosis.

Nitrated Confined Imidodiphosphates Enable a Catalytic Asymmetric Oxa-Pictet-Spengler Reaction.

The development of a highly enantioselective catalytic oxa-Pictet-Spengler reaction has proven a great challenge for chemical synthesis. We now report the first example of such a process, which was realized by utilizing a nitrated confined imidodiphosphoric acid catalyst. Our approach provides substituted isochroman derivatives from both aliphatic and aromatic aldehydes with high yields and excellent enantioselectivities. DFT calculations provide insight into the reaction mechanism.

Biocompatibility of calcined mesoporous silica particles with ventricular myocyte structure and function.

In vivo and in vitro systems were employed to investigate the biocompatibility of two forms of calcined mesoporous silica microparticles, MCM41-cal and SBA15-cal, with ventricular myocytes. These particles have potential clinical use in delivering bioactive compounds to the heart. Ventricular myocytes were isolated from 6 to 8 week male Wistar rats. The distribution of the particles in ventricular myocytes was investigated by transmission electron microscopy and scanning electron microscopy. The distribution of particles was also examined in cardiac muscle 10 min after intravenous injection of 2.0 mg/mL MCM41-cal. Myocyte shortening and the Ca(2+) transient were determined following exposure to 200 µg/mL MCM41-cal or SBA15-cal for 10 min. Within 10 min of incubation at 25 °C, both MCM41-cal and SBA15-cal were found attached to the plasma membrane, and some particles were observed inside ventricular myocytes. MCM41-cal was more abundant inside the myocytes than SBA15-cal. The particles had a notable affinity to mitochondrial membranes, where they eventually settled. Within 10 min of intravenous injection (2.0 mg/mL), MCM41-cal traversed the perivascular space, and some particles entered ventricular myocytes and localized around the mitochondrial membranes. The amplitude of shortening was slightly reduced in myocytes superperfused with MCM41-cal or SBA15-cal. The amplitude of the Ca(2+) transient was significantly reduced in myocytes superperfused with MCM41-cal but was only slightly reduced with SBA15-cal. Overall, the results show reasonable bioavailability and biocompatibility of MCM41-cal and SBA15-cal with ventricular myocytes.

Lanthanide oxochalcogenido clusters.

Lanthanide chalcogenolates react with either TeO(2) in pyridine or py-SO(3) in THF to give oxychalcogenido clusters. The sulfido derivatives (THF)(8)Ln(8)S(2)O(2)(SePh)(16) (Ln = Ce, Nd) are isostructural with previously reported oxoselenido compounds, and must be prepared at low temperatures to avoid the introduction of Se into the sulfide position. Analogous telluride derivatives for the early lanthanides were not obtained, but reactions of in situ prepared Ln(TePh)(3) with elemental Te and TeO(2) gave a complicated heterocluster product, with tetrametallic polytelluride [(py)(7)Ln(4)(mu(4)-Te)(mu(2)-Te(2))(2)(mu-eta(2)-eta(2)-Te(2)Te(Ph)Te(2))(TePh)] co-crystallizing with the oxotellurido compound [(py)(5)Ln(3)(mu(3)-O)(mu(2)-Te(2))(3)(TePh)] (Ln = Ho, Er). An analysis of the thermal decomposition of these compounds did not identify the oxo-containing products, with the sulfide compounds decomposing to give only Ln(3)Se(4) and the telluride compounds forming crystalline LnTe and Te metal.