Reaction of a redox-active ligand complex of nickel with dioxygen probes ligand-radical character.

Bis(imino)pyridine complex [Ni{2,6-(ArN=CMe)(2)C(5)H(3)N}Cl] (where Ar = 2,6-(i)Pr(2)C(6)H(3)) was synthesized by reduction of the corresponding dichloride complex and characterized as a ligand-radical complex of Ni(II). Reaction of this complex with O(2) caused intraligand C-C bond cleavage to afford the Ni complex of the new iminoethylpyridylcarboxamidato ligand, which also was isolated as the corresponding carboxamide, 6-(ArN=CMe)C(5)H(3)N-2-C(O)NHAr. This reaction serves as an example of small-molecule activation effected directly at the redox-active bis(imino)pyridine ligand without an overall oxidation state change at the Ni center.

Oxidase activity of a flavin-dependent thymidylate synthase.

Flavin-dependent thymidylate synthases (FDTS) catalyze the production of dTMP from dUMP and N(5),N(10)-methylene-5,6,7,8-tetrahydrofolate (CH(2)H(4)folate). In contrast to human and other classical thymidylate synthases, the activity of FDTS depends on a FAD coenzyme, and its catalytic mechanism is very different. Several human pathogens rely on this recently discovered enzyme, making it an attractive target for novel antibiotics.

As epidermal stem cells age they do not substantially change their characteristics.

In this study, we ask the basic question: do stem cells age? We demonstrated that epidermal stem cells isolated from neonatal mice had the capacity to form multiple cell lineages during development. Here we demonstrate the cell lineages are clonal, and that epidermal stem cells isolated from the footpad epithelium of old mice have similar capabilities. Using Hoechst dye exclusion and cell size, we isolated viable homogenous populations of epidermal stem and transit-amplifying (TA) cells from GFP-transgenic mice, and injected these cells into 3.

Effect of the delta6-desaturase inhibitor SC-26196 on PUFA metabolism in human cells.

The objective of this study was to determine the effect of 2,2-diphenyl-5-(4-[[(1 E)-pyridin-3-yl-methylidene]amino]piperazin-1-yl)pentanenitrile (SC-26196), a delta6-desaturase inhibitor, on PUFA metabolism in human cells. SC-26196 inhibited the desaturation of 2 microM [1-14C] 18:2n-6 by 87-95% in cultured human skin fibroblasts, coronary artery smooth muscle cells, and astrocytes. By contrast, SC-26196 did not affect the conversion of [1-14C]20:3n-6 to 20:4 in the fibroblasts, demonstrating that it is selective for delta6-desaturase.