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We compiled a social network of directors who were serving concurrently on the boards of several listed companies in China and analyzed the effect of the directors' social network centrality on corporate charitable donation. The results revealed that the directors' social network centrality had differing effects according to whether or not the enterprise was state-owned. Charitable donation of state-owned enterprises was not sensitive to directors' social network centrality, whereas the directors' social network centrality exerted a positive effect on charitable donation among enterprises that were not state-owned. These findings support the application of a political cost perspective to gain a better understanding of the mechanism of charitable donation. [ABSTRACT FROM AUTHOR]

Most of the >50 000 different pharmacologically active peptides in Conus venoms belong to a small number of gene superfamilies. In this work, the M-conotoxin superfamily is defined using both biochemical and molecular criteria. Novel excitatory peptides purified from the venoms of the molluscivorous species Conus textile and Conus marmoreus all have a characteristic pattern of Cys residues previously found in the μ-, kM-, and ψ-conotoxins (CC-C-C-CC). The new peptides are smaller (12-19 amino acids) than the μ-, kM-, and ψ-conotoxins (22-24 amino acids). One peptide, mr3a, was chemically synthesized in a biologically active form. Analysis of the disulfide bridges of a natural peptide tx3c from C. textile and synthetic peptide mr3a from C. marmoreus showed a novel pattern of disulfide connectivity, different from that previously established for the μ- and ψ-conotoxins. Thus, these peptides belong to a new group of structurally and pharmacologically distinct conotoxins that are particularly prominent in the venoms of mollusc-hunting Conus species. Analysis of cDNA clones encoding the novel peptides as well as those encoding μ-, kM-, and ψ-conotoxins revealed highly conserved amino acid residues in the precursor sequences; this conservation in both amino acid sequence and in the Cys pattern defines a gene superfamily, designated the M-conotoxin superfamily. The peptides characterized can be provisionally assigned to four distinct groups within the M-superfamily based on sequence similarity within and divergence between each group. A notable feature of the superfamily is that two distinct structural frameworks have been generated by changing the disulfide connectivity on an otherwise conserved Cys pattern. [ABSTRACT FROM AUTHOR]