Electrospray ionization mass spectrometry (ESI-MS) is found to gently and efficiently transfer small to large as well as singly to multiply charged [X+]n[A-]m supramolecules of imidazolium ion (X+) ionic liquids to the gas phase, and to reveal "magic numbers" for their most favored assemblies. Tandem mass spectrometric experiments (ESI-MS/MS) were then used to dissociate, via low-energy collision activation, mixed and loosely bonded [A- - - -X- - - -A']- and [X- - - -A- - - -X']+ gaseous supramolecules, as well as their higher homologues, and to estimate and order via Cooks' kinetic method (CKM) and B3LYP/6-311G(d,p) calculations the intrinsic solvent-free magnitude of hydrogen bonds. For the five anions studied, the relative order of intrinsic hydrogen-bond strengths to the 1-n-butyl-3-methylimidazolium ion [X1]+ is: CF3CO2- (zero) > BF4- (-3.1) > PF6- (-10.0) > InCl4- (-16.4) and BPh4- (-17.6 kcal mol(-1)). The relative hydrogen-bond strength for InCl4- was measured via CKM whereas those for the other anions were calculated and used as CKM references. A good correlation coefficient (R=0.998) between fragment ion ratios and calculated hydrogen-bond strengths and an effective temperature (Teff) of 430 K demonstrate the CKM reliability for measuring hydrogen-bond strengths in gaseous ionic liquid supramolecules. Using CKM and Teff of 430 K, the intrinsic hydrogen-bond strengths of BF4- for the three cations investigated is: 1-n-butyl-3-methyl-imidazolium ion (0) > 1,3-di-[(R)-3-methyl-2-butyl]-imidazolium ion (-2.4) > 1,3-di-[(R)-alpha-methylbenzyl]-imidazolium ion (-3.0 kcal mol(-1)). As evidenced by "magic" numbers, greater stabilities are found for the [(X1)2(BF4)3]- and [(X1)5A4]+ supramolecules (A not equal InCl4-).

A novel mass spectrometric method for rapid, accurate (2-4% ee) quantitation of chiral drugs is described. Copper(II)-bound complexes of seven model drugs (atenolol, DOPA, ephedrine, pseudoephedrine, isoproterenol, norepinephrine, propranolol) with chiral reference compounds (L-amino acids) are generated by electrospray ionization mass spectrometry. The trimeric complex ions (three chiral ligands--one of the analyte and two of the reference compound) are collisionally activated, and they undergo dissociation by competitive loss of either the neutral reference or the neutral drug molecule. The ratio of the two competitive dissociation rates, viz. the product ion branching ratio, is related via the kinetic method to the enantiomeric composition of the drug mixture. A two-point calibration curve, derived from the kinetic method, allows rapid quantitation of enantiomeric excess of drug mixtures. The chiral sensitivity of the method is such as to allow determination of mixtures with a few percent enantiomeric contamination.

The hemoglobin ␣-chain fragment PVNFKFLSH, which we have named hemopressin, produced dose-dependent hypotension in anesthetized rats, starting at 0.001 g/kg. The hypotensive effect of the peptide was potentiated by enalapril only at the lowest peptide dose. These results suggest a role for hemopressin as a vasoactive substance in vivo. The identification of these putative intracellular substrates for ep24.15 and ep24.16 is an important step toward the elucidation of the role of these enzymes within cells. Endopeptidase EC 3.4.24.15 (ep24.15; also referred to as thimet oligopeptidase) and endopeptidase EC 3. 4.24.16 (ep24.16; also referred to as neurolysin) were initially detected in and purified from rat brain homogenates (1, 2). The cloned rat brain ep24.16 (3) showed 80% similarity and 63% identity with the previously cloned rat testis ep24.15 (4). Both peptidases share most of their natural substrates, including bradykinin, neurotensin, opioids, angiotensin I, and gonadotrophinreleasing hormone (5, 6

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Malaria is one of the leading causes of morbidity and mortality in the tropics, with 300 to 500 million clinical cases and 1.5 to 2.7 million deaths per year. Nearly all fatal cases are caused by Plasmodium falciparum. The resistance of this parasite to conventional antimalarial drugs such as chloroquine is growing at an alarming rate and therefore new efficient drugs are urgently needed (1-3).In all organisms studied so far, the biosynthesis of isoprenoids such as dolichol, cholesterol, and ubiquinones depends on the condensation of the different numbers of isopentenyl diphosphate (IPP) 1 and dimethylallyl diphosphate units. In mammals and fungi, these units are derived from the classical mevalonate pathway (4). However, in higher plants, in several algae, in some eubacteria, and in P. falciparum the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway was described as the alternative non-mevalonate pathway for the synthesis of IPP (for reviews, see Refs. 5-10). This pathway starts with the condensation of pyruvate and glyceraldehyde 3-phosphate, which yields 1-deoxy-D-xylulose-5-phosphate (DOXP) as a key metabolite (11-17). The DOXP reductoisomerase then catalyzes the simultaneous intramolecular rearrangement and reduction of DOXP to form MEP (18 -22). The activity of this enzyme is specifically inhibited by fosmidomycin (23). Several reaction steps are necessary for the conversion of MEP to IPP. The downstream intermediates of MEP for this pathway are: 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol (CDP-ME) (24), 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol-2-phosphate (CDP-MEP), 2-C-methyl-D-erythritol-2,4-cyclodiphosphate (ME-2,4-cPP) (25, 26), and 4-hydroxy-3-methylbut-2-enyl pyrophosphate (27-31). IPP and dimethylallyl diphosphate are synthesized through independent routes in the late steps of the non-mevalonate pathway (32). These units are used for the biosynthesis of ubiquinones and dolichols, and for the prenylation of proteins and other products (33)(34)(35).Based on the sequence data provided by the malaria genome project (plasmodb.org), Jomaa and co-workers (21) identified two genes in P. falciparum that encode key enzymes of the MEP pathway: 1-deoxy-D-xylulose-5-phosphate synthase and 1-deoxy-D-xylulose-5-phosphate reductoisomerase. They also demonstrated that an amino-terminal signal sequence in 1-de- 1 The abbreviations and trivial names used are: IPP, isopentenyl diphosphate; MEP, 2-C-methyl-D-erythritol-4-phosphate; DOXP, 1-deoxy-D-xylulose-5-phosphate; DOX, 1-deoxy-D-xylulose; CDP-ME, 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol; CDP-MEP, 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol-2-phosphate; ME-2,4-cPP, 2-Cmethyl-D-erythritol-2,4-cyclodiphosphate; HPLC, high-performance liquid chromatography; ESI-QTOF-MS, ESI-quadrupole time-of-flight mass spectrometry; Q n , Coenzyme Q n .