Application Of Electrospray Ionization Research Articles

Differentiation between Isomeric 4,5-Functionalized 1,2,3-Thiadiazoles and 1,2,3-Triazoles by ESI-HRMS and IR Ion Spectroscopy.

A large variety of 1,2,3-thiadiazoles and 1,2,3-triazoles are used extensively in modern pure and applied organic chemistry as important structural blocks of numerous valuable products. Creation of new methods of synthesis of these isomeric compounds requires the development of reliable analytical tools to reveal the structural characteristics of these novel compounds, which are able to distinguish between isomers. Mass spectrometry (MS) is a clear choice for this task due to its selectivity, sensitivity, informational capacity, and reliability. Here, the application of electrospray ionization (ESI) with ion detection in positive and negative modes was demonstrated to be useful in structural studies. Additionally, interconversion of isomeric 4,5-functionalized 1,2,3-triazoles and 1,2,3-thiadiazoles was demonstrated. Application of accurate mass measurements and tandem mass spectrometry in MS2 and MS3 modes indicated the occurrence of gas-phase rearrangement of 1,2,3-triazoles into 1,2,3-thiadiazoles under (+)ESI-MS/MS conditions, independent of the nature of substituents, in line with the reaction in the condensed phase. Infrared multiple photon dissociation (IRMPD) spectroscopy enabled the establishment of structures of some of the most crucial common fragment ions, including [M+H-N2]+ and [M+H-N2-RSO2]+ species. The (-)ESI-MS/MS experiments were significantly more informative for the sulfonyl alkyl derivatives compared to the sulfonyl aryl ones. However, there was insufficient evidence to confirm the solution-phase transformation of 1,2,3-thiadiazoles into the corresponding 1,2,3-triazoles.

An electrospray ionization-ion mobility spectrometer as detector for high- performance liquid chromatography.

The application of electrospray ionization (ESI) ion mobility (IM) spectrometry on the detection end of a high-performance liquid chromatograph has been a subject of study for some time. So far, this method has been limited to low flow rates or has required splitting of the liquid flow. This work presents a novel concept of an ESI source facilitating the stable operation of the spectrometer at flow rates between 10 μL mn(-1) and 1500 μL min(-1) without flow splitting, advancing the T-cylinder design developed by Kurnin and co-workers. Flow rates eight times faster than previously reported were achieved because of a more efficient dispersion of the liquid at increased electrospray voltages combined with nebulization by a sheath gas. Imaging revealed the spray operation to be in a rotationally symmetric multijet mode. The novel ESI-IM spectrometer tolerates high water contents (≤90%) and electrolyte concentrations up to 10mM, meeting another condition required of high-performance liquid chromatography (HPLC) detectors. Limits of detection of 50 nM for promazine in the positive mode and 1 μM for 1,3-dinitrobenzene in the negative mode were established. Three mixtures of reduced complexity (five surfactants, four neuroleptics, and two isomers) were separated in the millisecond regime in stand-alone operation of the spectrometer. Separations of two more complex mixtures (five neuroleptics and 13 pesticides) demonstrate the application of the spectrometer as an HPLC detector. The examples illustrate the advantages of the spectrometer over the established diode array detector, in terms of additional IM separation of substances not fully separated in the retention time domain as well as identification of substances based on their characteristic Ims.

Cancer biomarkers and mass spectrometry-based analyses of phospholipids in body fluids

The lipid profiles of body fluids reflect the general condition of the whole organism and can indicate the existence of certain diseases such as cancer. Qualitative and quantitative assessment of lipids in blood and other body fluids could reveal novel biomarkers for early detection and prognosis of cancer; in addition, it may be useful in monitoring the efficacy and toxicity of anticancer treatment. Consequently, lipidomics is an emerging approach in cancer research. Phospholipids make up an important lipid class, which is particularly suitable for analyses by mass spectrometry. Mass spectrometry methods involving ‘soft’ ionization techniques, such as electrospray ionization and matrix-assisted laser desorption ionization, which are well established in the proteomics field, have also been implemented in analyses of lipids. This review focuses on the application of electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry in the characterization of structure and composition of phospholipids present in biofluids, and their importance for cancer-related problems.

Application of electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry for structural screening of core oligosaccharides from lipopolysaccharides of the bacteria Proteus

Electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used for screening and structural elucidation of core oligosaccharides isolated from lipopolysaccharides of bacteria of the genus Proteus. Mass spectra allowed the determination of the molecular masses with high accuracy and the estimation of the chemical heterogeneity of the samples. They did not, however, provide sufficient information to identify structural details of the branched oligosaccharides. Therefore, various fragmentation techniques for determining such details were examined. Infrared multiphoton dissociation tandem mass spectrometry (IRMPD-MS/MS) experiments in negative ion mode resulted in cleavage between the structurally conserved inner core region and the variable outer core region. Positive ion capillary skimmer dissociation mass spectra showed numerous fragment ion peaks, including those corresponding to the subsequent cleavage of the glycosidic linkages starting from the non-reducing end of the oligosaccharide. Despite their complexity, these mass spectrometric studies allowed confirmation of previously determined Proteus lipopolysaccharide core structures, and identification of new related structures in other strains of these bacteria.

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of metal-ion selected dynamic protein libraries.

The application of electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry to the investigation of the relative stabilities (and thus packing efficiencies) of Fe-bound trihelix peptide bundles is demonstrated. Small dynamic protein libraries are created by metal-ion assisted assembly of peptide subunits. Control of the trimeric aggregation state is coupled to stability selection by exploiting the coordination requirements of Fe(2+) in the presence of bidentate 2,2'-bipyridyl ligands covalently appended to the peptide monomers. At limiting metal-ion concentration, the most thermodynamically stable, optimally packed peptide trimers dominate the mass spectrum. The identities of optimally stable candidate trimers observed in the ESI FT-ICR mass spectra are confirmed by resynthesis of exchange-inert analogues and measurement of their folding free energies. The peptide composition of the trimers may be determined by infrared multiphoton dissociation (IRMPD) MS(3) experiments. Additional sequence information for the peptide subunits is obtained from electron capture dissociation (ECD) of peptides and metal-bound trimers. The experiments also suggest the presence of secondary structure in the gas phase, possibly due to partial retention of the solution-phase coiled coil structure.

Newborn Screening by Tandem Mass Spectrometry

Major expansion of newborn screening for inherited metabolic disorders is taking place across the US and around the world as newer analytical technology is applied. Historically, each disorder to be screened required a separate test with associated costs and requirement for a portion of the dried-blood-spot specimen from a heel stick. This limitation of the existing tests was partially responsible for the limitation of mandated newborn screening in the US to a small number of disorders (usually three to seven, depending on the state). The technique of tandem mass spectrometric (MS) analysis of dried-blood spots was first proposed for newborn screening in 1990 by Millington et al. (1). Using ionization techniques of fast atom bombardment or liquid secondary ionization with tandem MS, they simultaneously determined a large number of acylcarnitines as an acylcarnitine profile. This allowed newborn screening for numerous inherited fatty acid oxidation and organic acid disorders by a single procedure. Tandem MS was extended to amino acids, including phenylalanine, the screening target for detection of the phenylketonuria (PKU) test (2)(3)(4), and to other disorders, with several such tests described in these pages during the last 8 years (3)(5)(6)(7)(8)(9). The development and application of electrospray ionization (ESI) tandem MS with its ability to be automated made high-volume tandem MS screening for amino acid, organic acid, and fatty acid metabolic disorders practical by the mid-1990s (10)(11)(12). Automated ESI tandem MS newborn screening of amino acids …

Characterization of Macromolecules by Electrospray lonization Mass Spectrometry

Application of electrospray ionization (ESI) mass spectrometry (MS) to the analysis of oligomers and polymers is reviewed through several representative examples. The benefits and limitations of the technique are discussed considering the molecular weight and complexity (polydispersity) of the analyte. Recent results demonstrating the advantage of using hyphenated techniques such as size exclusion chromatography (SEC) coupled with ESI-MS are highlighted.

Analysis of short tandem repeat polymorphisms by electrospray ion trap mass spectrometry.

The application of electrospray ionization (ESI) ion trap mass spectrometry (MS) to the analysis of short tandem repeats (STRs or microsatellites) is described. Several equine dinucleotide STR loci were chosen as a model system to evaluate ESI ion trap as a routine instrument for rapid and reliable genoytping. With the use of specific primers STR loci were amplified from different blood samples having allele sizes between 60 and 100 bp. A new purification method based on reversible binding of PCR products to magnetic particles has proven to be directly compatible with ESI ion trap MS analysis. The sense and antisense strands of the PCR products with concentrations of approximately 100 fmol/microliter were measured with a mass accuracy of 0.01%. The simplicity of the purification method and the capability for automated handling together with the precise sizing of PCR products by ESI ion trap MS facilitate the large scale analysis of polymorphic STRs. Moreover, mixtures of different allele length as obtained for heterozygous samples could accurately be assigned as well as a C-->G switch between the two strands of a PCR product.

Analysis of O -glucuronide conjugates in urine by electrospray ion trap mass spectrometry

The application of electrospray ionization (ESI) ion trap mass spectrometry in the characterization of O-glucuronide conjugates of some drugs in urine is described. The conjugated metabolites formed in rabbit and human were separated by reversed-phase high-performance liquid chromatography (HPLC) and characterized by multi-stage mass spectrometry (MSn) experiments in negative ion mode. The ESI mass spectra showed a deprotonated molecule [M–H]–, which was chosen as precursor ion. Collision-induced dissociation (CID) of [M–H]– in MSn experiments resulted in the appearance of glucuronate ‘fingerprint’ ions at m/z 175 and 113 as well as prominent aglycone ions which were the same as those produced from authentic specimens. This information can be used to identify this type of compound directly without the need for derivatization or hydrolysis of enzymes, providing a rapid and specific method for guiding the isolation and characterization of similar compounds in complex matrices with LC/MS.