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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pristine Alpian fresh water lakes with no run off were selected to monitor the atmospheric fall-out of C6--C12 -organochlorine compounds. Off-shore marine areas were taken for monitoring the average marine pollution by these compounds. In both cases fishes have been used as bioextractors. The analytical work-up combines solvent-partition, liquid chromatography and glass capillary gas chromatography with the electron capture detector. The idenfification is done by matching high-resilution retention indices of unknowns with those of reference compounds. The following compounds could be identified in the spawn of arctic chars (Salvelinus alpinus) caught in off-road Alpian lakes as well as in the liver of predatory antarctic cod (Dissostichus eleginoides) caught near South Georgia, as well as in Peru fish oil and crude sperm oil: hexachlorobenzene alpha-, beta-, gamma-hexachlorocyclohexane; 4,4'-DDT; 4,4'-DDE; 4,4'-DDD; 2,4'-DDE; 2,4'-DDD; heptachloroepoxide; polychlorobiphenyls (PCB) and polychlorocamphenes. Concentrations are given in nanogram/gram total lipid extract (ppb). First value Salvelinus (Alps), second value Dissostich (Antarctic Ocean), alpha-HCH: 40/0,1; beta-HCH: 4,1/0,1; gamma-HCH: 17,2/0,1; HCB: 65/8; 4,4'-DDT: 59/4; 4,4'-DDE: 477/5; sigma DDT 646/11,4; sigma PCB: 1030/32; sigma PCC: 124/68.
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PMID:Baseline studies of the global pollution. I. Occurrence of organohalogens in pristine European and antarctic aquatic environments. 739 98

Integral membrane proteins remain a challenge to proteomics because they contain domains with physicochemical properties poorly suited to today's bottom-up protocols. These transmembrane regions may potentially contain post-translational modifications of functional significance, and thus development of protocols for improved coverage in these domains is important. One way to achieve this goal is by using top-down mass spectrometry whereby the intact protein is subjected to mass spectrometry and dissociation. Here we describe top-down high resolution Fourier transform mass spectrometry with collisionally activated dissociation to study post-translationally modified integral membrane proteins with polyhelix bundle and transmembrane porin motifs and molecular masses up to 35 kDa. On-line LC-MS analysis of the bacteriorhodopsin holoprotein yielded b- and y-ions that covered the full sequence of the protein and cleaved 79 of 247 peptide bonds (32%). The experiment proved that the mature sequence consists of residues 14-261, confirming N-terminal propeptide cleavage and conversion of N-terminal Gln-14 to pyrrolidone carboxylic acid (-17.02 Da) and C-terminal removal of Asp-262. Collisionally activated dissociation fragments localized the N(6)-(retinylidene) modification (266.20 Da) between residues 225-248 at Lys-229, the sole available amine in this stretch. Off-line nanospray of all eight subunits of the cytochrome b(6)f complex from the cyanobacterium Nostoc PCC 7120 defined various post-translational modifications, including covalently attached c-hemes (615.17 Da) on cytochromes f and b. Analysis of murine mitochondrial voltage-dependent anion channel established the amenability of the transmembrane beta-barrel to top-down MS and localized a modification site of the inhibitor Ro 68-3400 at Cys-232. Where neutral loss of the modification is a factor, only product ions that carry the modification should be used to assign its position. Although bond cleavage in some transmembrane alpha-helical domains was efficient, other regions were refractory such that their primary structure could only be inferred from the coincidence of genomic translation with precursor and product ions that spanned them.
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PMID:Post-translational modifications of integral membrane proteins resolved by top-down Fourier transform mass spectrometry with collisionally activated dissociation. 2009 75