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Expression of the human surfactant protein-A2 (hSP-A2) gene is lung specific, occurs in type II and Clara ceils, and is developmentally and hormonally regulated in fetal lung. Using transfected human fetal type II cells, we previously observed that ~300 bp of 5'-flanking DNA mediated cAMP and interleukin-1 (IL-1) stimulation and dexamethasone (Dex) inhibition of hSP-A2 promoter activity. This region contains response elements for estrogen-related receptor a element (ERRE, -241 bp), thyroid transcription factor (TTF)- 1/Nkx2.1 (TTF-binding protein, -171 bp), upstream stimulatory factor 1/2 (E-box, -80 bp), and stimulatory protein (Sp) 1 (G/T-box, -62 bp), which are essential for basal and cAMP induction of hSP-A2 expression, To define genomic regions necessary for developmental, hormonal, and tissue-specific regulation of hSP-A2 expression in vivo, we analyzed transgenic mice carrying hGH reporter genes comprised of 313 bp of hSP-A2 gene 5'-flanking DNA [+ or -] mutation in the TBE or 175 bp of 5'-flanking DNA, containing TBE, E-box and G/T-box, but lacking ERRE. Transgenes containing 313 or 175 bp of hSP-A2 5'-flanking DNA were expressed in a lung cell-specific manner and developmentally regulated in concert with the endogenous mouse SP-A gene. In cultured lung explants from hSP-A_313:hGH transgenic fetal mice, cAMP and IL-1 induced and Dex inhibited transgene expression. However, the 175-bp hSP-A2 genomic region was insufficient to mediate hormonal regulation of hSP-A2 promoter activity. The finding that expression of the hSP-A_313TBEmut:hGH transgene was essentially undetectable in fetal lung and was not hormonally regulated in transgenic fetal lung explants underscores the critical importance of the TBE in lung cell-specific, developmental, and hormonal regulation of hSP-A2 gene expression. fetal lung; tissue specific; type II cell; adenosine 3',5'-cyclic monophosphate; glucocorticoid

Single-atom catalysts (SACs) regulated by heteroatoms have displayed great potential as electrocatalysts for highly efficient hydrogen evolution reaction (HER); however, the controllable synthesis of an axial coordination structure of SACs to achieve robust HER performance remains a great challenge. Herein, we have proposed a doping-adsorption-pyrolysis strategy to construct NiN4–Cl active sites with axial Cl coordination for accelerating electrocatalytic HER. The obtained NiN4–Cl SAs/NC catalyst exhibits superior HER activity with low over-potential, small Tafel slope, high turnover frequency, and long-term stability. Density functional theory calculation reveals that the excellent HER performance of NiN4–Cl SAs/NC originates from the axial Cl-coordination-induced electronic localization enhancement, which is beneficial for the adsorption and activation of H* intermediate, thus accelerating the HER process. This work opens a new opportunity for rational design and construction of high-performance SAC catalysts by axial coordination strategy for electrocatalytic application. [ABSTRACT FROM AUTHOR]

Adsorption and dehydrogenation of C2–C6n-alkanes are investigated on a Pt substrate using density functional theory (DFT) calculations, and the size effects of alkane molecules and Pt substrates are discussed in detail. The Pt(111) surface and Pt55 cluster are chosen to represent large and small Pt nanoparticles, respectively. The C2–C6 straight-chain alkanes show no site preference on Pt(111) drifting over the surface, but prefer to locate along the edge sites of Pt55. Our results suggest that a linear relationship holds for the adsorption energies of n-alkanes against the chain length on Pt(111), in accordance with the experimental observations. Pt55 also exhibits a similar linear relationship for n-alkanes but with larger adsorption energies due to the low-coordinated Pt atoms at the edge site. For the two-step dehydrogenation from alkanes to alkenes, the first dehydrogenation reaction is the rate-determining step (RDS) on Pt(111), and a larger size of alkane molecule will lead to a lower dehydrogenation activity. While on Pt55, no RDS is present and the dehydrogenation activity oscillates slightly as the chain length of n-alkane increases. Generally, Pt55 involves lower energy barriers for most dehydrogenation steps compared to Pt(111), indicating that small Pt particles with more low-coordinated Pt atoms are more active towards alkane dehydrogenation. In addition, a clear BEP relationship is identified for all the dehydrogenation reactions of C2–C6n-alkanes on Pt substrates, and this linear relationship is independent of the particle size of the Pt substrate and the chain length of alkanes. [ABSTRACT FROM AUTHOR]