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Cobalt carbonyl complexes as probes for alkyne-tagged lipids.

ABSTRACT: Monitoring lipid distribution and metabolism in cells and biological fluids poses many challenges because of the many molecular species and metabolic pathways that exist. This study describes the synthesis and study of molecules that contain an alkyne functional group as surrogates for natural lipids in cultured cells. Thus, hexadec-15-ynoic and hexadec-7-ynoic acids were readily incorporated into RAW 264.7 cells, principally as phosphocholine esters; the alkyne was used as a "tag" that could be transformed to a stable dicobalt-hexacarbonyl complex; and the complex could then be detected by HPLC/MS or HPLC/UV(349nm). The 349 nm absorbance of the cobalt complexes was used to provide qualitative and quantitative information about the distribution and cellular concentrations of the alkyne lipids. The alkyne group could also be used as an affinity tag for the lipids by a catch-and-release strategy on phosphine-coated silica beads. Lipid extracts were enriched in the tagged lipids in this way, making the approach of potential utility to study lipid transformations in cell culture. Both terminal alkynes and internal alkynes were used in this affinity "pull-down" strategy. This method facilitates measuring lipid species that might otherwise fall below limits of detection.

SUBMITTER: Tallman KA

PROVIDER: S-EPMC3617960 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Cobalt carbonyl complexes as probes for alkyne-tagged lipids.

Tallman Keri A KA Armstrong Michelle D MD Milne Stephen B SB Marnett Lawrence J LJ Brown H Alex HA Porter Ned A NA

Journal of lipid research 20130110 3

Monitoring lipid distribution and metabolism in cells and biological fluids poses many challenges because of the many molecular species and metabolic pathways that exist. This study describes the synthesis and study of molecules that contain an alkyne functional group as surrogates for natural lipids in cultured cells. Thus, hexadec-15-ynoic and hexadec-7-ynoic acids were readily incorporated into RAW 264.7 cells, principally as phosphocholine esters; the alkyne was used as a "tag" that could be ...[more]

PMID: 23307946

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Project description:The structures and energetics of the binuclear cyclopentadienylmetal alkyne systems Cp2M2C2R2 (M = Ni, Co, Fe; R = Me and NMe2) have been investigated using density functional theory. For the Cp2M2C2(NMe2)2 (M = Ni, Co, Fe) systems the relative energies of isomeric tetrahedrane Cp2M2(alkyne) structures having intact alkyne ligands and alkyne dichotomy structures Cp2M2(CNMe2)2 in which the C[triple bond, length as m-dash]C triple bond of the alkyne has broken completely to give separate Me2NC units depending on the central metal atoms. For the nickel system Cp2Ni2C2(NMe2)2 as well as the related nickel systems Cp2Ni2(MeC2NMe2) and Cp2Ni2C2Me2 the tetrahedrane structures are clearly preferred energetically consistent with the experimental syntheses of several stable Cp2Ni2(alkyne) complexes. The tetrahedrane and alkyne dichotomy structures have similar energies for the Cp2Co2C2(NMe2)2 system whereas the alkyne dichotomy structures are significantly energetically preferred for the Cp2Fe2C2(NMe2)2 system. The potential energy surfaces for the Cp2M2(MeC2NMe2) and Cp2M2C2Me2 systems (M = Co, Fe) are complicated by low-energy structures in which hydrogen migration occurs from the alkyne methyl groups to one or both alkyne carbon atoms to give Cp2M2(C3H3NMe2) and Cp2M2(C3H3Me) derivatives with bridging metalallylic ligands, Cp2M2(CH2[double bond, length as m-dash]C[double bond, length as m-dash]CHNMe2) and Cp2M2(CH2[double bond, length as m-dash]C[double bond, length as m-dash]CHMe) with bridging allene ligands, as well as Cp2M2(CH2[double bond, length as m-dash]CH-CNMe2) and Cp2M2(CH2[double bond, length as m-dash]CH-CHMe) with bridging vinylcarbene ligands. For the Cp2M2C2Me2 (M = Co, Fe) systems migration of a hydrogen atom from each methyl group to an alkyne carbon atom can give relatively low-energy Cp2M2(CH2[double bond, length as m-dash]CH-CH[double bond, length as m-dash]CH2) structures with a bridging butadiene ligand. Five transition states have been identified in a proposed mechanism for the conversion of the Cp2Co2/MeC[double bond, length as m-dash]CNMe2 system to the cobaltallylic complex Cp2Co2(C3H3NMe2) with intermediates having agostic C-H-Co interactions and an activation energy barrier sequence of 13.1, 17.0, 15.2, and 12.0 kcal mol-1.

Dataset Information

Cobalt carbonyl complexes as probes for alkyne-tagged lipids.

Publications

Cobalt carbonyl complexes as probes for alkyne-tagged lipids.

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