Reprogramming of mouse and human somatic cells by high-performance engineered factors.

Reprogramming somatic cells to become induced pluripotent stem cells (iPSCs) by using defined factors represents an important breakthrough in biology and medicine, yet remains inefficient and poorly understood. We therefore devised synthetic factors by fusing the VP16 transactivation domain to OCT4 (also known as Pou5f1), NANOG and SOX2, respectively. These synthetic factors could reprogramme both mouse and human fibroblasts with enhanced efficiency and accelerated kinetics. Remarkably, Oct4-VP16 alone could efficiently reprogramme mouse embryonic fibroblasts (MEFs) into germline-competent iPSCs. Furthermore, episomally delivered synthetic factors could reproducibly generate integration-free iPSCs from MEFs with enhanced efficiency. Our results not only demonstrate the feasibility of engineering more potent reprogramming factors, but also suggest that transcriptional reactivation of OCT4 target genes might be a rate-limiting step in the conversion of somatic cells to pluripotent cells. Synthetic factor-based reprogramming might lead to a paradigm shift in reprogramming research.

Ab initio chemical kinetics for the hydrolysis of N2O4 isomers in the gas phase.

The mechanism and kinetics for the gas-phase hydrolysis of N(2)O(4) isomers have been investigated at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) level of theory in conjunction with statistical rate constant calculations. Calculated results show that the contribution from the commonly assumed redox reaction of sym-N(2)O(4) to the homogeneous gas-phase hydrolysis of NO(2) can be unequivocally ruled out due to the high barrier (37.6 kcal/mol) involved; instead, t-ONONO(2) directly formed by the association of 2NO(2), was found to play the key role in the hydrolysis process. The kinetics for the hydrolysis reaction, 2NO(2) + H(2)O ↔ HONO + HNO(3) (A) can be quatitatively interpreted by the two step mechanism: 2NO(2) → t-ONONO(2), t-ONONO(2) + H(2)O → HONO + HNO(3). The predicted total forward and reverse rate constants for reaction (A), k(tf) = 5.36 × 10(-50)T(3.95) exp(1825/T) cm(6) molecule(-2) s(-1) and k(tr) = 3.31 × 10(-19)T(2.478) exp(-3199/T) cm(3) molecule(-1) s(-1), respectively, in the temperature range 200-2500 K, are in good agreement with the available experimental data.

A Facile, Low-Cost Hot-Pressing Process for Fabricating Lithium-Sulfur Cells with Stable Dynamic and Static Electrochemistry.

Lithium-sulfur batteries are among the most promising low-cost, high-energy-density storage devices. However, the inability to host a sufficient amount of sulfur in the cathode while maintaining good electrochemical stability under a lean electrolyte condition has limited the progress. The main cause of these challenges is the sensitivity of the sulfur cathode to the cell-design parameters (i.e., the amount of sulfur and electrolyte) and the experimental testing conditions (i.e., cycling rates and analysis duration). Here, a hot-pressing method is presented that effectively encapsulates a high amount of sulfur in the cathode within only 5 s, resulting in high sulfur loading and content of, respectively, 10 mg cm-2 and 65 wt%. The hot-pressed sulfur (HPS) cathodes exhibit superior dynamic and static electrochemical performance under a broad cycling-rate (C/20-1C rates) and low electrolyte/sulfur ratio (6 µL mg-1 ) conditions. The dynamic cell stability is demonstrated by high gravimetric and areal capacities of, respectively, 415-730 mAh g-1 and 7-12 mAh cm-2 at C/20-1C rates with a high capacity retention of over 70% after 200 cycles. The static cell stability is demonstrated by excellent shelf life with low self-discharge and stable cycle life on storing for over one year.