ABSTRACT
A methodology was developed to design superior sorbents of oxoanions. To integrate the high efficiency of chemisorption, selectivity, and recyclability into one sorbent, understanding the nature of oxoanions-sorbent interactions and the structural evolution of the sorbents is essential. Three cationic Ag(I) coordination polymers (CPs) are synthesized for dichromate (Cr2O72-) removal, and three distinct oxoanion-exchange mechanisms are identified, namely, the replacement, breath, and reconstruction processes, depending on the degree of framework distortion induced by the dichromate-CP interactions. The single crystal to single crystal transformation during the oxoanion exchange has been investigated by using single-crystal X-ray diffraction and energy-dispersive X-ray microanalysis. The replacement process, due to a weak chemisorption, shows excellent recyclability at the cost of reduction of efficiency and selectivity of adsorption. The reconstruction process may achieve a high efficiency and selectivity, but it loses recyclability. Due to the formation of a Ag-O(dichromate) bond and the breathing effect of the framework, the sorbent with the breath mechanism shows both superior efficiency and high recyclability in dichromate removal. The study of perrhenate (ReO4-) removal using the same CPs demonstrates that one CP performing the reconstruction process during dichromate removal turns to the breath process in removal of perrhenate anions. These results of mechanism-property correlation provide an insight into improvement of the methodology to fabricate a superior CP sorbent for oxoanion removal.
ABSTRACT
Objective The aim of this study was to construct a recombinant lentivirus-mediated short hairpin RNA (shRNA) expression vector targeting the long non-coding RNA (lncRNA) BC002811 and establish a gastric cancer SGC-7901 cell line with stable BC002811 down-regulation. Methods Three small interfering RNAs (siRNA) were designed and synthesized. The best sequence for RNA interference was selected by real-time quantitative PCR (qPCR) and inserted into the lentiviral vector pLVX-shRNA2. After identification by DNA sequencing, the lentiviral vectors carrying BC002811 shRNA were packaged in HEK293T cells. The lentiviral particles were collected to infect human gastric cancer SGC-7901 cells. After screened by limiting dilution analysis, the SGC-7901 cell line with stable BC002811 down-regulation was established, the expression level of BC002811 detected by qPCR, and the effect of BC002811 on the proliferation of the cells analyzed by MTS. Results The results of qPCR showed that BC002811 siRNA-1 was the most effective siRNA sequence, with a knockdown efficiency of 87%. The recombinant lentiviral vector was packaged in the HEK293T cells with a viral titer of 3.7 × 108 TU/mL in the shRNA-1 group as compared with 4.5 × 108 TU/mL in the control. The expression of BC002811 in the shRNA-1 group was only 10% of that in the control group (P < 0.01), which indicated the successful establishment of the gastric cancer SGC-7901 cell line with stable BC002811 down-regulation. BC002811 knockdown significantly inhibited the proliferation of the SGC-7901 cells in the shRNA-1 group as compared with the control. Conclusion A recombinant lentiviral vector expressing BC002811 shRNA was successfully constructed and the gastric cancer cell line SGC-7901 with stable BC002811 silencing was established.
ABSTRACT
To avoid the instability and inefficiency for anion-exchange resins and layered double-hydroxides materials, we present herein a flexible coordination network [Ag(L243)](NO3)(H2O)(CH3CN) (L243 = 3-(2-pyridyl)-4-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole) with superefficient trapping capacity for permanganate, as a group-7 oxoanion model for radiotoxic pertechnetate pollutant. Furthermore, a high-throughput screening strategy has been developed based on concentration-gradient design principle to ascertain the process and mechanism for anion exchange. Significantly, a series of intermediates can be successfully isolated as the qualified crystals for single-crystal X-ray diffraction. The result evidently indicates that such a dynamic material will show remarkable breathing effect of the three-dimensional host framework upon anion exchange, which mostly facilitates the anion trapping process. This established methodology will provide a general strategy to discover the internal secrets of complicated solid-state reactions in crystals at the molecular level.
