Short chain ferrocenylalkyl disulfides, where n < 9, with the amide functionality (−OCN) at variable positions were synthesized and self-assembled on vapor-deposited gold. The effects of interchain hydrogen bonding on the stability, packing density, electron transfer rate and the formal potential of these self-assembled monolayers were investigated using cyclic voltammetry and infrared reflection−absorption spectroscopy. Interchain hydrogen bonding appeared to enhance the stability of these monolayers, although the packing densities were lower than that expected for a full monolayer. The electrochemical behavior of coadsorbed monolayers of ferrocenylalkyl disulfides and nonelectroactive unsubstituted alkanethiols was also examined. In these coadsorbed systems, an unexpected negative shift in the formal potential of the ferrocenyl compounds with the amide linkages was observed. This was attributed to disorder arising from the disruption of the hydrogen bonds within the monolayer caused by the alkanethiol “spacers”, thus making it slightly easier for the ferrocene subunits to undergo oxidation. Interchain hydrogen bonding within each surface-confined layer was also probed with infrared reflection−absorption spectroscopy. A general broadening of the amide stretch appearing around 3300 cm-1 in the surface spectra relative to the same amide stretch in the calculated surface spectra provided compelling evidence for interchain hydrogen bonding.

Human and pig cDNAs for a novel stomach protein, the product of a gene expressed at high levels specifically in cells of the antrum mucosa, have been characterized. The general exon/intron structure of the genomic DNA is conserved in humans and mice. The predicted protein sequences of the human and mouse mRNAs contain 185 and 184 amino acids, respectively. The protein isolated from pig antral extracts has an NH2 terminus consistent with cleavage of a 20-amino acid signal peptide. Human cDNA was expressed in E. coli to generate a protein antigen for antibody production. The antibodies detected polypeptides of approximately 18 kDa in antrum extracts from all mammalian species tested. Immunocytochemistry located antrum mucosal protein (AMP)-18 to surface mucosal cells of the mouse antrum and, specifically, to secretion granules, suggesting that it is cosecreted with mucins. Antrum extracts and recombinant human AMP-18 exhibit growth-promoting activity on epithelial cells that can be blocked by the specific antisera. We suggest that AMP-18 is a "gastrokine" that maintains the integrity of the gastric mucosal epithelium.

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To induce variation through chromosome doubling in Gerbera jamesonii Bolus cv. Sciella, twoweek-old in vitro grown shoots were treated with various concentrations of colchicine (0.01, 0.05, 0.10, 0.50 or 1% w/v) for 2, 4 or 8 h. Treated shoots were then cultured on Murashige and Skoog (MS) medium supplemented with 8.8 lM 6-benzyladenine (BA) and 155 lM adenine sulphate (ADS), and subsequently transferred to fresh MS medium containing 2.85 lM indole-3 acetic acid (IAA) for rooting. When shoots were treated with 0.1% colchicine for 8 h, 64% of recovered plantlets were tetraploid. Ploidy of plantlets was confirmed by flow cytometry, stomatal analysis, and morphological characters. Tetraploid plantlets displayed slower proliferation along with higher vigor and thickened broad leaves. Moreover, tetraploid plants developed larger flowers, longer stalks, and have improved vase-life, all contributing to higher ornamental value of gerbera.