Analysis by fast-atom bombardment tandem mass spectrometry of phosphatidylcholine isolated from heart mitochondrial fractions: Evidence of incorporation of monohydroxylated fatty acyl moieties

Phosphatidylcholine (PC) is one of the main phospholipids present in mitochondrial membranes. According to current knowledge, the predominant fatty acyl moieties in this phospholipid are 16, 18, 20, or 22 carbon atoms long with chains that contain only carbon and hydrogen atoms. We have conducted a detailed analysis of the fatty acid substituents of the phospholipids present in mitochondrial fractions by using fast-atom bombardment tandem PC extracted from mitochondrial fractions of rat heart. The structure of one of these monohydroxylated fatty acids has been elucidated and corresponded to 12-hydroxy 9-octadecenoic acid. Indications that concern the structure of the five other monohydroxylated fatty acids are presented. These monohydroxylated fatty acyl groups are preferentially associated in the PC molecule with C-18 and C-20 fatty acyl moieties. We present arguments to suggest that the formation of these compounds is probably not due to a free-radical initiated mechanism. The potential implication of these monohydroxylated fatty acids in several physiological functions is suggested by the fact that free hydroxylated fatty acids that are identical or closely related to those found in the mitochondrial fractions possess various biological activities.     

Determination of the anomeric configuration of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl phosphates by fast-atom bombardment tandem mass spectrometry

Collision-induced dissociation of the deprotonated molecules of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl (dolichyl and polyprenyl) phosphates results in distinct fragmentation patterns that depend on cis-trans configuration of the phosphodiester and 2″ (or 2′, respectively)-hydroxyl groups of the glycosyl residue. At the collision-offset voltage of 0. 5 V, sugar nucleotides with cis configuration produce only one very abundant fragment of nucleoside monophosphate, whereas compounds with trans configuration give weak signals for nucleoside di- and mono-phosphates and their dehydration products. These fragmentation patterns are largely preserved at higher collision energy, with the exception that, for sugar nucleotides with trans configuration, the characteristic signals are much more abundant and a novel diagnostic fragment of [ribosyl(deoxyribosyl)-5′-P₂O₅ — H]^? is generated. In the case of polyisoprenyl-P-sugars, polyisoprenyl phosphate ion is the only fragment observed for compounds with trans configuration, whereas in compounds with cis configuration, this ion is accompanied by another abundant fragment, which is derived from the cleavage across the sugar ring and corresponds to [polyisoprenyl-PO₄-(C₂H₃O)]^?. The relative intensity ratio of the latter ion to the [polyisoprenyl-HPO₄]^? ion is close to 1 for compounds with cis configuration, but it is only about 0. 01 for compounds with trans configuration. This ratio may serve, therefore, as a diagnostic value for determination of the anomeric configuration of glycosyl esters of polyisoprenyl phosphates. It is proposed that the observed differences in fragmentation patterns of cis-trans sugar nucleotides and polyisoprenyl-P-sugars could be explained in terms of kinetic stereoelectronic effect, and a speculative mechanism of fragmentation of compounds with trans configuration is presented. For compounds with cis configuration, formation of a hydrogen bond between the C-2″(2′) hydroxyl and the phosphate group could play a crucial role in directing the specific fragmentation reactions. Consequently, the described empirical rules would hold only for compounds that have a free 2″(2′)-hydroxyl group and no alternative charge location. Owing to its simplicity, sensitivity, and tolerance of impurities, fast-atom bombardment-tandem mass spectrometry represents a suitable method for determination of the anomeric linkage of glycosyl esters of nucleoside pyrophosphates and polyisoprenyl phosphates if the absolute configuration of glycosyl residue is known and the compound fulfills the above-mentioned requirements.     

Fast-atom bombardment mass spectrometry and low energy collision-induced tandem mass spectrometry of tauroconjugated bile acid anions

Fragmentation of negative ions produced by fast-atom bombardment (FAB) from 14 tauroconjugated bile acids and some of their deuterated analogs has been studied by mass spectrometry and by collision-induced dissociation (CED) tandem mass spectrometry at low energy. Low energy collision-induced dissociation of the deprotonated molecules [M - H]^? of these tauroconjugated bile acids leads to both charge-driven and charge-remote fragmentations (CRF). The former yields neutral loss from the side chain with charge migration during the fragmentation process. These fragments dominate the CID spectra, but are absent from the FAB spectra. Their relative abundances are dependent on the number and the positions of the hydroxyl groups in the steroid nucleus and thus permit distinction among some positional isomers. The CRF fragments correspond to cleavages in the side chain up to fragmentations across the steroid rings with charge retention on the sulfonate group. These CRF fragments, which also are useful for structural identification, are less intense in CID than in FAB spectra. It appears that these charge-remote fragments are favored by unsaturation in the steroid rings, either as keto groups or as endocyclic double bonds. Tandem mass spectrometry combined with the use of deuterated analogs demonstrates that the structures of the survivor pseudomolecular ions and of the CRF fragments are not rearranged.     

Scaled Gromov hyperbolic graphs

In this article, the δ‐hyperbolic concept, originally developed for infinite graphs, is adapted to very large but finite graphs. Such graphs can indeed exhibit properties typical of negatively curved spaces, yet the traditional δ‐hyperbolic concept, which requires existence of an upper bound on the fatness δ of the geodesic triangles, is unable to capture those properties, as any finite graph has finite δ. Here the idea is to scale δ relative to the diameter of the geodesic triangles and use the Cartan–Alexandrov–Toponogov (CAT) theory to derive the thresholding value of δdiam below which the geometry has negative curvature properties. © 2007 Wiley Periodicals, Inc. J Graph Theory 57: 157–180, 2008     

The Intersection of Pseudovarieties of Central Simple Semigroups

The problem of computing a finite semigroup generating the intersection of two finitely generated pseudovarieties is considered. A solution to this problem is presented for central simple semigroups.     

Lower limits on R-parity-violating couplings in supersymmetric models with light squarks

We interpret the results of searches for strongly interacting massive particles to place absolute lower limits on R-parity-violating couplings for squarks with mass (m(q) below 100 GeV. Recent searches for anomalous isotopes require that there be a baryon-number-violating or lepton-number-violating coupling larger than 10(-22)-10(-21) if m(q)>18 GeV. Using data from searches for stable particles at the CERN Large Electron Positron Collider (LEP) we demonstrate that this lower limit increases by 14 orders of magnitude, to an R-parity-violating coupling larger than 10(-8)-10(-7) for any squarks of mass less than 90 GeV. In the presence of an R-parity-violating coupling of this magnitude, neutralinos cannot explain the dark matter density in the Universe.     

Conventional MR imaging with simultaneous measurements of cerebral blood volume and vascular permeability in ganglioglioma

The conventional MR imaging appearance of gangliogliomas is often variable and nonspecific. Conventional MR images, relative cerebral blood volume (rCBV) and vascular permeability (K(trans)) measurements were reviewed in 20 patients with pathologically proven grade 1 and 2 gangliogliomas (n = 20) and compared to a group of grade 2 low-grade gliomas (n = 30). The conventional MRI findings demonstrated an average lesion size of 4.1 cm, contrast enhancement (n = 19), variable degree of edema, variable mass effect, necrosis/cystic areas (n = 8), well defined (n = 12), signal heterogeneity (n = 9), calcification (n = 4). The mean rCBV was 3.66 +/- 2.20 (mean +/- std) for grade 1 and 2 gangliogliomas. The mean rCBV in a comparative group of low-grade gliomas (n = 30), was 2.14 +/- 1.67. p Value < 0.05 compared with grade 1 and 2 ganglioglioma. The mean K(trans) was 0.0018 +/- 0.0035. The mean K(trans) in a comparative group of low-grade gliomas (n = 30), was 0.0005 +/- 0.001. p Value = 0.14 compared with grade 1 and 2 ganglioglioma. The rCBV measurements of grade 1 and 2 gangliogliomas are elevated compared with other low-grade gliomas. The K(trans), however, did not demonstrate a significant difference. Gangliogliomas demonstrate higher cerebral blood volume compared with other low-grade gliomas, but the degree of vascular permeability in gangliogliomas is similar to other low-grade gliomas. Higher cerebral blood volume measurements can help differentiate gangliogliomas from other low-grade gliomas.     

Relaxation of an optimal control problem involving a perturbed sweeping process

We establish first, in the setting of infinite dimensional Hilbert space, a result concerning the existence of solutions for perturbed sweeping processes whose perturbations are Lipschitz single-valued maps. Then we use this result to extend to the infinite dimensional setting a relaxation result concerning optimal control problems involving such processes. Dedicated to R. Tyrrell Rockafellar on the occasion of his 70th birthday