Positive mode electrospray ionization mass spectrometry of bisphosphonates using dicationic and tricationic ion-pairing agents.

A general method for detecting bisphosphonate drugs by ESI-MS and LC-ESI-MS as positive ions has been developed. Bisphosphonates can have multiple negative charges in solution. Tricationic ion-pairing reagents were paired with bisphosphonates to form a positively charged complex. It was clear that this facile pairing method worked. However, an appreciable presence of -1 bisphosphonate species were observed in positive mode ESI-MS (i.e. as the +2 complex with tricationic reagents). This led to an extended investigation on the use of dicationic pairing agents. The use of dicationic reagents improved the detection sensitivity for all of the bisphosphonates. Tandem mass spectrometry also improved the limits of detection for most of the bisphosphonates using both the tricationic and dicationic pairing reagents. A tricationic reagent also was used as an ion-pairing reagent in chromatography experiments. Thus the addition of a single reagent produced benefits in that it increased chromatographic retention and enhanced the ESI-MS detection of bisphosphonates.

The evaluation and comparison of trigonal and linear tricationic ion-pairing reagents for the detection of anions in positive mode ESI-MS.

A general and sensitive method for detecting divalent anions by ESI-MS and LC/ESI-MS as positive ions has been developed. The anions are paired with tricationic reagents to form positively charged complexes. In this study, four tricationic reagents, 2 trigonal and 2 linear, were used to study a wide variety of anions, such as disulfonates, dicarboxylates, and inorganic anions. The limits of detection for many of the anions studied were often improved by tandem mass spectrometry. Tricationic pairing agents can also be used with chromatography to enhance the detection of anions. The tricationic reagents were also used to detect monovalent anions by monitoring the doubly charged positive complex. The limits of detection for some of the divalent anions by this method are substantially lower than by other current analytical techniques.

Ionic liquids in analytical chemistry.

The role of ionic liquids (ILs) in analytical chemistry is increasing substantially every year. A decade ago there were but a handful of papers in this area of research that were considered curiosities at best. Today, those publications are recognized as seminal articles that gave rise to one of the most rapidly expanding areas of research in chemical analysis. In this review, we briefly highlight early work involving ILs and discuss the most recent advances in separations, mass spectrometry, spectroscopy, and electroanalytical chemistry. Many of the most important advances in these fields depend on the development of new, often unique ILs and multifunctional ILs. A better understanding of the chemical and physical properties of ILs is also essential.

Evaluation of flexible linear tricationic salts as gas-phase ion-pairing reagents for the detection of divalent anions in positive mode ESI-MS.

Anion analysis is of great importance to many scientific areas of interest. Problems with negative mode ESI-MS prevent researchers from achieving sensitive detection for anions. Recently, we have shown that cationic reagents can be paired with anions, such that detection can be done in the positive mode, allowing for low limits of detections for anions using ESI-MS. In this analysis, we present the use of 16 newly synthesized flexible linear tricationic ion-paring reagents for the detection of 11 divalent anions. These reagents greatly differ in structure from previously reported trigonal tricationic ion-pairing agents, such that they are far more flexible. Here we present the structural features of these linear trications that make for good ion-pairing agents as well as show the advantage of using these more flexible ion-pairing reagents. In fact, the limit of detection for sulfate using the best linear trication was found to be 25 times lower than when the best rigid trication was used. Also, MS/MS experiments were performed on the trication-dianion complex to significantly reduce the detection limit for many dianions. Limits of detection in this analysis were as low as 50 fg.

RLIP76 in defense of radiation poisoning.

PURPOSE: To determine the role of RLIP76 in providing protection from radiation and chemotherapy. In the present report, we used RLIP76 to refer to both the mouse (Ralbp1) and the human (RLIP76) 76-kDa splice variant proteins (RLIP76) for convenience and to avoid confusion. In other reports, Ralbp1 refers to the mouse enzyme (encoded by the Ralbp1 gene), which is structurally and functionally homologous to RLIP76, the human protein encoded by the human RALBP1 gene. METHODS AND MATERIALS: Median lethal dose studies were performed in RLIP76(-/-) and RLIP76(+/+) C57B mice after treatment with a single dose of RLIP76 liposomes 14 h after whole body radiation. The radiosensitivity of the cultured mouse embryonic fibroblasts and the effects of buthionine sulfoximine (BSO), amifostine, c-jun N-terminal kinase (JNK), protein kinase B (Akt), and MAPK/ERK kinase (MEK) were determined by colony-forming assays. Glutathione-linked enzyme activities were measured by spectrophotometric assays, glutathione by dithiobis-2-nitrobenzoic acid (DTNB), lipid hydroperoxides by iodometric titration, and aldehydes and metabolites by thiobarbitauric acid reactive substances and liquid chromatography-mass spectrometry (LCMS). RESULTS: RLIP76(-/-) mice were significantly more sensitive to radiation than were the wild-type, and RLIP76 liposomes prolonged survival in a dose-dependent manner in both genotypes. The levels of 4-hydroxynonenal and glutathione-conjugate of 4-hydroxynonenal were significantly increased in RLIP76(-/-) tissues compared with RLIP76(+/+). RLIP76(-/-) mouse embryonic fibroblasts were markedly more radiosensitive than RLIP76(+/+) mouse embryonic fibroblasts, despite increased glutathione levels in the former. RLIP76 augmentation had a remarkably greater protective effect compared with amifostine. The magnitude of effects of RLIP76 loss on radiation sensitivity was greater than those caused by perturbations of JNK, MEK, or Akt, and the effects of RLIP76 loss could not be completely compensated for by modulating the levels of these signaling proteins. CONCLUSION: The results of our study have shown that RLIP76 plays a central role in radiation resistance.

The determination of glutathione-4-hydroxynonenal (GSHNE), E-4-hydroxynonenal (HNE), and E-1-hydroxynon-2-en-4-one (HNO) in mouse liver tissue by LC-ESI-MS.

Glutathione (GSH) conjugation of 4-hydroxy-2(E)-nonenal (HNE) is an efficient means of cellular detoxification. HNE is a byproduct of lipid peroxidation which has shown toxicity but also signaling roles. E-1-hydroxynon-2-en-4-one (HNO) is another byproduct of lipid peroxidation which has the same molecular weight as HNE. This study presents the LC-MS detection of GS-HNE, HNE, and HNO in tissue samples without derivatization and with minimal sample preparation. Tissue samples were taken from wild-type mice and knock-out mice, which have been bred without the RLIP76 transfer protein. Extraction procedures were developed to determine GS-HNE and HNE levels in the mouse liver tissue. A gradient elution LC-MS method was developed for GS-HNE analysis using electrospray ionization and selected ion monitoring (SIM). The HNE/HNO method involves isocratic elution due to instability issues. Higher levels of GSHNE, HNE, and HNO were found in the knock-out animals, due to the absence of the RLIP76 transport mechanism.

Resolution of enantiomers in solution and determination of the chirality of extended metal atom chains.

The resolution of enantiomers of extended metal atom chains of the type Ni3[(C5H5N)2N]4Cl2 has been accomplished by chromatographic methods in solution, and the chirality was determined using vibrational circular dichroism, electronic circular dichroism, optical rotatory dispersion, and density functional theory calculations.

Enantioseparation of extended metal atom chain complexes: unique compounds of extraordinarily high specific rotation.

Extended metal atom chains (EMACs) contain a linear metal chain wrapped by various ligands. Most complexes are of the form M(3)(dpa)(4)X(2), where M = metal, dpa = 2,2'-dipyridylamide, and X = various anions. The ligands form helical coils about the metal chain, which results in chiral EMAC complexes. The EMACs containing the metals Co and Cu were partially separated in polar organic mode using a vancomycin-based chiral stationary phase. Under similar conditions, two EMACs with Ni metal and varying anions could be baseline separated. The polar organic mode was used because of the instability of the compounds in aqueous mobile phases. Also, these conditions are more conducive to preparative separations. Polarimetric measurements on the resolved enantiomers of Ni(3)(dpa)(4)Cl(2) indicate that they have extraordinarily high specific rotations (on the order of 5000 deg cc/g dm).