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Strategies for the rapid and reliable analysis of microorganisms have been sought to meet national needs in defense, homeland security, space exploration, food and water safety, and clinical diagnosis. Mass spectrometry has long been a candidate technique because it is extremely rapid and can provide highly specific information. It has excellent sensitivity. Molecular and fragment ion masses provide detailed fingerprints, which can also be interpreted. Mass spectrometry is also a broad band method--everything has a mass--and it is automatable. Mass spectrometry is a physiochemical method that is orthogonal and complementary to biochemical and morphological methods used to characterize microorganisms.

In addition to its critical role in normal cell function, growth, and metabolism, zinc is implicated as a major factor in the development and progression of many pathological conditions and diseases. Despite this importance of zinc, many important factors, processes, and mechanisms of the physiology, biochemistry, and molecular biology of zinc remain unknown. Especially important is the unresolved issue regarding the mechanism and process of the trafficking, transport, and reactivity of zinc in cells; especially in mammalian cells. This presentation focuses on the concept that, due to the existence of a negligible pool of free Zn(2+) ions in the mammalian cell environment, the trafficking, transport and reactivity of zinc occurs via a direct exchange of zinc from donor Zn-ligands to acceptor ligands. This Zn exchange process occurs without the requirement for production of free Zn(2+) ions. The direct evidence from mammalian cell studies is presented in support of the operation of the direct Zn-ligand exchange mechanism. The paper also provides important information and conditions that should be considered and employed in the conduct of studies regarding the role and effects of zinc in biological/biomedical research; and in its clinical interpretation and application., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The biotin repressor is an allosterically regulated, site-specific DNA-binding protein. Binding of the small ligand bio-5'-AMP activates repressor dimerization, which is a prerequisite to DNA binding. Multiple disorder-to-order transitions, some of which are known to be important for the functional allosteric response, occur in the vicinity of the ligand-binding site concomitant with effector binding to the repressor monomer. In this work, the extent to which these local changes are coupled to additional changes in the structure/dynamics of the repressor was investigated using hydrogen/deuterium exchange coupled to mass spectrometry. Measurements were performed on the apo-protein and on complexes of the protein bound to four different effectors that elicit a range of thermodynamic responses in the repressor. Global exchange measurements indicate that binding of any effector to the intact protein is accompanied by protection from exchange. Mass spectrometric analysis of pepsin-cleavage products generated from the exchanged complexes reveals that the protection is distributed throughout the protein. Furthermore, the magnitude of the level of protection in each peptide from hydrogen/deuterium exchange correlates with the magnitude of the functional allosteric response elicited by a ligand. These results indicate that local structural changes in the binding site that occur concomitant with effector binding nucleate global dampening of dynamics. Moreover, the magnitude of dampening of repressor dynamics tracks with the magnitude of the functional response to effector binding.

A quantitative method was developed for the determination of heme (ferriprotoporphyrin IX) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The method was designed for forensic characterization of the use of blood agar in preparation of Bacillus spores. An alkali wash of 0.3 M ammonium hydroxide was used to solubilize heme from spore samples. The wash was concentrated and analyzed by MALDI-TOFMS. Experimental parameters were optimized to obtain the best signal intensity, maximize signal reproducibility, and improve day-to-day repeatability of the measurement. Sinapinic acid was found to be the best matrix. A sandwich sample preparation protocol was determined to increase the shot-to-shot and point-to-point reproducibility of the measurement. Cobalt(III) protoporphyrin was used as an internal standard and the analyte/internal standard ratio responses from solutions of known concentrations were used to construct a calibration curve (R(2) = 0.993). Limits of detection and quantitation for heme were calculated to be approximately 0.4 (200 fmol) and 0.8 microM (400 fmol), respectively. Spore samples prepared on blood agar and nonblood agar were analyzed using the method. Heme was detected at a concentration of approximately 0.3 ng/mg of spore on samples prepared on blood agar and purified by extensive washing. Heme was not detected on spore samples prepared without blood.

Cadmium-induced metallothionein in a mollusc, the oyster Crassostrea virginica, occurs in both blocked and unblocked forms (Roesijadi, G., Kielland, S.L. and Klerks, P. (1989) Arch. Biochem. Biophys. 273, 403-413). The block, which is the sole difference in the structure of the two proteins, was identified as an acetyl group with use of tandem mass spectrometry. The blocked and unblocked proteins carried N-acetylserine and serine, respectively, at the N-terminus and were designated CvNAcMT and CvMT. Only CvNAcMT was detected under basal conditions. Both forms were induced by Cd. Pulse-labeling with [35S]cyteine at specified times during exposure showed that the rate of CvNAcMT synthesis in gills increased rapidly, initially exceeding that of CvMT, then declined to the rate attained by CvMT. Turnover rates for Cd-induced CvMT and CvNAcMT were similar to each other. They appeared to be faster when measured in the absence of Cd in the external medium (k = 0.18 and 0.16/day, respectively), than in its presence (k = 0.03 and 0.06/day, respectively).

High-performance liquid chromatography (HPLC) has been successfully interfaced on-line with liquid secondary-ion time-of-flight mass spectrometry, utilizing a continuous-flow interface. Time-of-flight mass spectrometry (TOF-MS) is a low-resolution, high-mass-range technique, compatible with extremely rapid data acquisition rates. Thus a TOF-MS system is extremely well suited for coupling with HPLC. This paper describes the interface used to couple the HPLC and TOF-MS as well as the basic operating principles of such a system. Using both standard and packed-capillary reversed-phase HPLC columns, the HPLC-TOF-MS system has been successfully used to separate and detect peptides, providing molecular weight information for the peptide analytes. Experimental data, including chromatograms (UV, reconstructed ion and selected ion) and mass spectra, are presented to demonstrate the ability of the HPLC-liquid secondary-ion TOF-MS system to resolve chromatographically analytes as well as to resolve mass spectrometrically analytes which are unresolved on the chromatographic column.

We have identified two metabolites of clofazimine (B663; Lamprene; 3-(p-chloroanilino)-10-(p-chlorophenyl)-2,10-dihydro-2-isopropyliminophenazine) in our initial investigation of its metabolism in leprosy patients. Based on mass, ultraviolet, and visible spectrometry, we characterized an unconjugated (metabolite I, 3-(p-hydroxyanilino)-10-(p-chlorophenyl)-2,10-dihydro-2-isopropyliminophenazine ) and a conjugated (metabolite II, 3-(beta-D-glucopyranosiduronic acid)-10-(p-chlorophenyl)-2,10-dihydro-2-isopropyliminophenazine) metabolite from the urine of patients. Both metabolites were red in color, similar to clofazimine; however, both were considerably more polar than the parent drug. We suggest that metabolite I was formed by a hydrolytic dehalogenation reaction, and metabolite II by hydrolytic deamination followed by glucuronidation.

In this investigation, 31 1-O-acyl glucuronides were synthesized and 25 of these were shown to react with 4-(p-nitrobenzyl)pyridine (NBP), a standard chemical nucleophil, on thin layer chromatography plates. A quantitative NBP assay was developed based on existing methods, and the rates of reaction of three acyl glucuronides, clofibric 1-O-acyl glucuronide, indomethacin 1-O-acyl glucuronide, and flufenamic 1-O-acyl glucuronide, were determined. These rates ranged from 0.436 min-1 to 1.08 min-1. Chlorambucil, a powerful alkylating agent, reacted with NBP 127 times faster than the most reactive of the three glucuronides assayed. The half-lives of these three 1-O-acyl glucuronides, determined at pH 2.0, 4.0, 6.0, 7.4, and 10.0 in aqueous phosphate solution, ranged from greater than 1000 hr at pH 2 to less than 1 min at pH 10.0. Determination of the rates of reaction of 1-O-acyl glucuronides with NBP and the rates of hydrolysis as a function of pH further characterize these compounds as activated phase II metabolites.

Sialylated biantennary glycopeptides from human fibrinogen were analyzed with fast atom bombardment mass spectrometry. The mass spectrometric conditions used in the positive mode showed predominantly molecular ions with no fragment ions due to the loss of sialic acid. Standard mixtures of glycopeptides with zero, one, and two sialic acid residues revealed a linear relationship between ion abundance and molar fraction. The desorption efficiency varied according to the number of sialic acid residues in these biantennary glycopeptides. The relative abundance of different molecular ion species differing only in amino acid content was in agreement with chemical analysis. Sensitivity, precision, and requirements for sample preparation were assessed. Both assignment of molecular weights and quantification of individual glycopeptide species from human fibrinogen were obtained. The glycopeptides from human fibrinogen were found to consist of a mixture of equal amounts of monosialylated and disialylated species with no asialoglycopeptides.

1-O-acyl glucuronides are reactive Phase II metabolites which can alkylate chemical nucleophiles. Industrial sulfate ester mixed anhydrides have been reported to be active acylating agents. This study was undertaken in order to establish that sulfate ester mixed anhydrides of clinically useful drugs could be synthesized, purified, and characterized as reactive chemical species. Their ability to alkylate 4-(p-nitrobenzyl)pyridine (NBP) and their stability in aqueous solution was compared with 1-O-acyl glucuronide conjugates of the same drugs. Synthesis of the 1-O-acyl glucuronides of the hypolipidemic agent, clofibric acid, and the nonsteroidal antiinflammatory drugs flufenamic acid and indomethacin were catalyzed by immobilized microsomal rabbit liver UDP-glucuronyltransferase. Potassium salts of the sulfate ester mixed anhydrides of these drugs were synthesized chemically by temperature-controlled reaction with chlorosulfonic acid in anhydrous pyridine. Half-lives at pH 2.0, 6.0, 7.4, and 10.0 were determined for each compound. The reactivity of the acyl glucuronides and sulfate ester mixed anhydrides towards the standard chemical nucleophile, 4-(p-nitrobenzyl pyridine (NBP), was measured using a spectrophotometric assay at several substrate concentrations. Acyl sulfate ester mixed anhydrides were shown to be 3-20 times more reactive towards NBP than their corresponding 1-O-acyl glucuronides. For both glucuronides and sulfate esters, relative reactivity towards NBP was: clofibric acid greater than indomethacin greater than flufenamic acid. This behavior paralleled the hydrolytic instability of the compounds.

Plasma desorption mass spectrometry (PD-MS) was used to assess the molecular weight heterogeneity of glycopeptides (6-12 amino acids) from each of the three N-linked glycosylation sites of bovine fetuin (R.G. Spiro (1962) J. Biol. Chem. 237, 382-388). The glycopeptides were purified by a combination of anion exchange chromatography and reverse-phase HPLC. Since no detectable fragmentation was observed in the PD-MS of these asialoglycopeptides, the observation of multiple molecular ions could be attributed to either carbohydrate or peptide heterogeneity. Assignment of molecular ions, within 3 to 5 amu of the theoretical mass, of glycopeptides from each glycosylation site was made from amino acid composition, peptide sequence around the glycosylation sites, and previously reported triantennary oligosaccharide structures (B. Nilsson, N.E. Nordén, and S. Svensson (1979) J. Biol. Chem. 254, 4545-4553). Ion groups differing in mass by one N-acetyllactosamine unit were observed in glycopeptides from the Asn-Asp and Asn-Cys sites, localizing these previously observed biantennary oligosaccharide structures (R.R. Townsend, M.R. Hardy, T.C. Wong, and Y.C. Lee (1986) Biochemistry 25, 5716-5725; S. Takasaki and A. Kobata (1986) Biochemistry 25, 5709-5715) to these two sites. The presence of biantennary oligosaccharides at the Asn-Asp sites could be substantiated using 1H NMR but were not detected in the Asn-Cys glycopeptides. PD-MS was also implemented in the purification protocol for these glycopeptides and proved to be useful in assessing purity of chromatographic fractions which were mixtures of glycopeptides displaying both carbohydrate and peptide heterogeneity. A preparation scheme was developed to obtain molecular ions of desialylated glycopeptides by PD-MS.

Dicyclopentadiene, a waste product of manufacturing at the Rocky Mountain Arsenal near Denver Colorado, has been detected in ground water at this facility. Ground water extracts were analysed by gas chromatography-mass spectrometry (GC/MS) to determine if derivatives of dicyclopentadiene were present in addition to dicyclopentadiene and other chemical wastes. The derivatives thus identified were characterized by GC high resolution MS, deuterium exchange for active hydrogen in the chemical ionization source of the mass spectrometer, and GC/MS following on-column base catalyzed deuteration of enolizable hydrogen. Two ketone derivatives of dicyclopentadiene were identified by comparison with synthetic standards. Ground water derivatives of dicyclopentadiene were compared with mammalian enzymatic metabolites produced in vitro by incubation with immobilized rabbit liver cytochromes P-450. The metabolites were analysed by GC/MS and by GC/MS following derivatization and deuterium labelling. Although not found in ground water samples, the two metabolites were identified as monoepoxides of dicyclopentadiene by comparison with compounds synthesized in the laboratory.

Examination of the product of affinity labeling of delta 5-3-ketosteroid isomerase (EC 5.3.3.1) of Pseudomonas testosteroni by the suicide substrate [7-3H]5,10-secoestr-5-yne-3,10,17-trione has demonstrated that the steroid becomes bound by an acid- and base-labile linkage to an active-site peptide representing residues 55-58 (H2N-Tyr-Ala-Asn-Ser-CO2H) of the primary structure (Penning, T. M., and Talalay, P. (1981) J. Biol. Chem. 256, 6851-6858). Upon release of the steroid by mild acid hydrolysis, the peptide is converted into a more basic structure while retaining its amino acid composition (as determined by conventional means). These findings were rationalized by postulating that the steroid is bound as an imido ester via the amide group of asparagine 57 and that the polypeptide backbone participates (via attack by nitrogen or oxygen) in the hydrolysis of this ester with the formation of a cyclic amidine or basic oxazine. By comparing the properties of the isolated tetrapeptide, from which the steroid has been removed, with those of synthetic H2N-Tyr-Ala-Asn-Ser-CO2H and H2N-Tyr-Ala-Asp-Ser-CO2H by electron impact and fast atom bombardment mass spectrometry, we now have evidence for the presence of an oxazine (5,6-dihydro-6-iminio-4H-1,3-oxazine) in the modified peptide. Our results draw attention to the hitherto unsuspected degree of nucleophilicity of the amide group of the side chain of asparagine and the participation of this group in the formation of an imido ester.