Mass Spectrometric Analysis. Aliphatic Nitriles

McLafferty, Fred W.

doi:10.1021/ac60181a005

Cited by 64 publications

(13 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4B). During the fragmentation, one fragment may exchange one AMU with the other fragment (7,15). Also, molecular ions become variably hydrated within argon collision cells (25).…”

Section: Fig 2 Carbohydrate Composition (A) Of Capsular Ps From 6a␣mentioning

confidence: 99%

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

et al. 2007

View full text Add to dashboard Cite

Using two monoclonal antibodies, we found subtypes among pneumococcal isolates that are typed as serotype 6A by the quellung reaction. The prevalent subtype bound to both monoclonal antibodies and was labeled here 6A␣, whereas the minor subtype bound to only one monoclonal antibody and was labeled 6A␤. To determine the biochemical nature of the two serologically defined subtypes, we purified capsular polysaccharides (PSs) from the two subtypes and examined their chemical structures with gas-liquid chromatography and mass spectrometry. The study results for 6A␣ PS are consistent with the previously published structure of 6A PS, which is 32) galactose (133) glucose (133) rhamnose (133) Streptococcus pneumoniae is a major human pathogen that is responsible for a large percentage of cases of pneumonia, meningitis, otitis media, and sepsis (6). All pathogenic pneumococci are known to display one of many structurally diverse carbohydrate capsules, which shield pneumococci from host phagocytes and increase their pathogenicity (2). Antisera to a capsule type can be used to treat patients infected with the pneumococci expressing that capsule type (4). Consequently, for the past century, the serological types of pneumococcal capsules have been extensively investigated with quellung reactions. These studies have culminated in identifying 90 different pneumococcal capsules with distinct serological patterns (9) and chemical structures (10).Not all 90 serotypes are equally pathogenic. For instance, serotypes 6A and 6B account for 4.7% and 7%, respectively, of cases of invasive pneumococcal disease in the U.S. population (19,20). Because of their medical importance, the molecular natures of serotype 6A and its related serotype, serotype 6B, have been studied extensively. Biochemical studies found that the capsular polysaccharides (PSs) of serotypes 6A and 6B are linear polymers with a repeating unit containing four monosaccharides/alditols: rhamnose, ribitol-phosphate (P), galactose, and glucose (10). The two PSs are identical except for a difference in the linkage between rhamnose and ribitol (see Fig. 6).Currently available pneumococcal vaccines are designed to elicit antibodies to the capsular PSs of the most common pneumococcal serotypes. Since vaccine-induced immunoprotection is serotype specific, serotyping pneumococcal isolates from patients is an important tool for monitoring the effectiveness of pneumococcal vaccines (3). Because the classical quellung reaction with rabbit antisera is tedious to perform (13), we have developed a new serotyping system based on mouse monoclonal antibodies (mAbs) and a multiplexed immunoassay (27). While validating the new system, we found that a minor fraction of the isolates determined to be serotype 6A by quellung reaction bound to one 6A-specific mAb (Hyp6AG1) but not to the other (Hyp6AM3), whereas the majority of the serotype 6A isolates bound to both mAbs (12). To distinguish between the isolates, we have labeled the isolates reacting with both mAbs as 6A␣ and those reacting wit...

show abstract

“…4B). During the fragmentation, one fragment may exchange one AMU with the other fragment (7,15). Also, molecular ions become variably hydrated within argon collision cells (25).…”

Section: Fig 2 Carbohydrate Composition (A) Of Capsular Ps From 6a␣mentioning

confidence: 99%

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Compound identification was achieved by comparing the experimentally obtained RI with those listed in literature, [22] co-injection of individual authentic components including pinenes (α and β), linalool, borneol, n-nonane, n-decanal, n-tetradecane, n-pentadecane, n-heptadecane, n-nanodecane, and by matching the mass spectral data with those held in the National Institute of Standards and Technology (NIST) and Wiley libraries of mass spectra and literature comparison. [22][23][24] Antimicrobial study…”

Section: Compound Identificationmentioning

confidence: 99%

Investigating the chemical Composition and the antimicrobial activity of the essential oil and Crude Extracts of Sedum Microcarpum (Sm.) schönl Growing Wild in Jordan

Al–Qudah¹,

Muhaidat²,

Alomary³

et al. 2012

Pharmacognosy Journal

View full text Add to dashboard Cite

Background: Several Sedum species, such as S. album L., S. acre L., S. palaestinum Bieb, and S. pallidum are used in traditional medicine to heal wounds, hemorrhoids, constipation, food fungi, and as laxative and diuretic agents. Materials and Methods: In this study, the antimicrobial activities of the hexane, n-butanol and aqueous methanol extracts as well as the essential oil from Jordanian sedum microcarpum (Sm.) schönl were investigated and Analysis of the oil constituents by using Gas chromatography-Mass spectrometer (GC/MS). Conclusion: The hexane extract showed no antibacterial activity against seven strains. The butanol and aqueous methanol extracts were active against the Gram-positive bacteria Staphylococcus epidermidis, Bacillus cereus and the Gram negative bacteria including Enterococcus faecalis, Escherichia coli, Klebsiella pneumonia and Serratia marcescens. Phytochemical screening of the active extracts revealed the presence of a mixture of quinones, tannins, alkaloids and flavonoids. The essential oil showed moderate activities against the tested strains. Analysis of the oil using Gas chromatography-Mass spectrometer (GC/MS) revealed a complex mixture of aldehydes, mono-and sesquiterpenes in addition to alkaloids. Oxygenated monoterpenes dominated the different classes of compounds detected (36.39%). The major volatile constituents from S. microcarpum included Myrtenol (21.7%), Caryophyllene oxide (8.2%) and z-1, 6-dioldihydromyrcene (5.87%).

show abstract

“…A similar mechanism has been proposed in the case of aliphatic and aromatic iodocompounds. 5,6 Although a hydrogen rearrangement to the oxygen atom of the carbonyl group has favourable geometry in 3a-6a, and may give more stable products, as in the McLafferty rearrangement of carbonyl compounds, it is unlikely that it occurs since the oxygen atom is in an unexcited state. In the molecular ions studied, the oxygen excitation process (n, p*) has a unfavourable energy, about 1230 kJ/mol, in comparison to the critical energies (E o ) for the cleavage of the C-I bonds (Table 2).…”

Section: Fragmentation Of Molecular Ionsmentioning

confidence: 99%

“…5,6 The usefulness of mass spectral techniques in differentiating E-and Z-isomers across the carbon-carbon double bond has been reviewed.…”

mentioning

confidence: 99%

EI fragmentation of E,Z-3-iodo-2-alkenoic acids and methyl E,Z-3-iodo-2-alkenoates

Herrera

Urdaneta

1998

Rapid Commun. Mass Spectrom.

View full text Add to dashboard Cite

The electron ionization mass spectra of some E,Z-3-iodo-2-alkenoic acids and methyl E,Z-3-iodo-2-alkenoates were investigated. A semi-empirical method was used to examine the thermochemical and molecular properties of the species. Two fragmentation paths of the molecular ions are determined by the geometry of the carbon-carbon double bond: (i) heterolytic loss of I Á radical, and ( The 3-halo-2,3-unsaturated acids and esters are valuable intermediates in organic synthesis. They present biological properties such as the defoliating agent of cotton plants 1 and they also have given rise to concern due to impact on the environment.2 Knowledge of the mass spectrometric behaviour of these compounds is important especially in the case of geometric isomers. Mass fragmentation studies have been carried out only for C 3 and C 4 alkenoates substituted with chloride and/or bromine atom.2-4 The mass fragmentation of iodo-substituted alkyl and aromatic compounds have been reported. 5,6 The usefulness of mass spectral techniques in differentiating E-and Z-isomers across the carbon-carbon double bond has been reviewed. 7In a previous work, concerned with the synthesis and characterization of 3-halo-2,3-unsaturated acids, we reported that E,Z-3-iodo-2-butenoic acids have a significant difference in the abundances of their molecular ions upon electron ionization. 8 We examined a group of E,Z-3-iodo-2-alkenoic acids and methyl E,Z-3-iodo-2-alkenoates in order to investigate the generality of that geometric effect. The results of this investigation are the subject of this paper.The application of the semi-empirical PM3 method, 9 to calculate theoretical thermochemical and molecule orbital data, provides insight into reactions of the studied molecular ions. PM3 has been utilized in the study of carbocations, 10 and the mass spectra of carbonyl, 11 aromatic 12,13 and alkyltrimethylammonium 14 compounds, as well as in the determination of proton affinities. 15 EXPERIMENTALThe mass spectra were obtained on individual compounds by using gas chromatographic introduction into a quadrupole mass detector. The gas chromatograph was a HewlettPackard 5890 Series II (Hewlett Packard, Avondale PA, USA) equipped with a cross-linked methyl silicone capillary column (Ultra 1, 25 m Â 0.2 mm i.d. 0.11 mm thickness), and the mass detector was a Hewlett-Packard Model HP 5971A. The injector, transfer line and mass detector temperatures were 200, 280 and 176°C respectively. The electron ionization energy was 70 eV.The Z-3-iodo-2-alkenoic acids were prepared by heating for 12 hours 2,3-acetylenic acids with an excess of concentrated aqueous HI, in a sealed glass ampoule at 100°C, following the method reported by Noble.16 The E-isomers were obtained by heating for 14 hours the pure Z-isomer in a sealed glass ampoule at 130°C. The esters were prepared by esterification of the carboxylic acid according to the method of Marshall et al. 17 The purity and configuration of the compounds were verified as explained elsewhere.2 The following twelve compounds were p...

show abstract

Mass Spectrometric Analysis. Aliphatic Nitriles

Cited by 64 publications

References 15 publications

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

Investigating the chemical Composition and the antimicrobial activity of the essential oil and Crude Extracts of Sedum Microcarpum (Sm.) schönl Growing Wild in Jordan

EI fragmentation of E,Z-3-iodo-2-alkenoic acids and methyl E,Z-3-iodo-2-alkenoates

Contact Info

Product

Resources

About