Mass selection of ions in a Fourier transform ion cyclotron resonance trap using correlated harmonic excitation fields (CHEF)

The ammonium ion binding affinities of tetraethyl resorcarene (1) and its per-methylated derivative (2) were studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. Ten different ammonium ions were tested as guests for the resorcarenes. A strong tendency for complex formation was observed with all ammonium ions of size and charge distribution suitable for noncovalent interactions with the cavities of the resorcarene hosts 1 and 2. Although differences in ammonium ion affinities were observed between 1 and 2 due to the dissimilar conformations, the overall tendency was that increase in the degree of substitution and the length of carbon chain of the ammonium cation facilitated the complex formation until the sterical hindrance impeded the complexation. Dimeric as well as monomeric ammonium ion complexes were formed with resorcarene 1, but resorcarene 2 was unable to form the dimeric capsules because of the lack of H-bond donor possibilities. The nature of binding of the guest was further investigated with ion-molecule reactions and by determination of the single crystal X-ray structure of host 1 complexed with tetramethyl ammonium bromide.

Section: Mass Spectrometric Studiesmentioning

confidence: 99%

Ammonium ion mediated resorcarene capsules: ESI-FTICRMS study on gas-phase structure and ammonium ion affinity of tetraethyl resorcarene and its per-methylated derivative

Mäkinen

Vainiotalo

Nissinen

2003

“…Tandem mass spectrometry (MS n ) experiments were performed by first isolating the precursor ion by a CHEF [32] isolation sweep, followed by "cleanup" shots if necessary. SORI-CID [33] was accomplished by lowering the cell pressure to ϳ1 ϫ 10 Ϫ6 mbar range, while exciting the ion off resonance for 250 ms.…”

Section: Instrumentationmentioning

confidence: 99%

Probing isomeric differences of phosphorylated carbohydrates through the use of ion/molecule reactions and FT-ICR MS

Leavell

Leary

2003

Through the use of ion/molecule reactions and tandem mass spectrometry, phosphate position is assigned in both phosphorylated monosaccharides and oligosaccharides. In previous work [1, 2] phosphate moieties of monosaccharides were stabilized under collisional activation, by first derivatizing the deprotonated monosaccharide with trimethyl borate through an ion/molecule reaction, and the phosphate position determined through marker ions generated in tandem mass spectra. In this work, the methodology is extended to larger phosphorylated oligomers employing chlorotrimethylsilane (TMSCl) as the ion/molecule reagent. Phosphorylated monosaccharides were first investigated to determine diagnostic ions for phosphate linkage in monomeric standards. It was observed that the diagnostic ions showed both linkage and some monosaccharide stereochemical information. Furthermore, it was observed that TMS addition stabilized the phosphate moiety under collisionally activated conditions. Upon identification of the diagnostic ions, the methodology was applied to lactose-1-phosphate. It was found that TMSCl, stabilized the phosphate moiety upon collisional activation, and furthermore, the phosphate linkage could be determined through tandem mass spectrometric analysis. As a further extrapolation to biologically relevant problems, the methodology was applied to a lipophosphoglycan analog from the protozoan parasite Leishmania. This sample contains bridging phosphates which were converted to terminal phosphates through collision induced dissociation. The sample was then analyzed in the same manner as lactose-1-phosphate, yielding phosphate linkage information and stereochemical information. This study showed that, using the developed methodology, phosphate linkage can be determined from both monosaccharides and larger oligosaccharides; furthermore it is applicable to samples in which the phosphates are either terminating or bridging. (J Am Soc Mass Spectrom 2003, 14, 323-331)

“…Also in Table 1 are the BIRD rate constants obtained when (Ade) 2 (H 2 O) 3 K ϩ or (Ade) 2 (H 2 O) 2 K ϩ were isolated in the ICR cell using correlated harmonic excitation fields (CHEF) [30,31]. It is not expected that the BIRD rate constants are affected by the isolation process.…”

Section: Resultsmentioning

confidence: 99%

Solvation of electrosprayed ions in the accumulation/collision hexapole of a hybrid Q-FTMS

Rajabi

Easterling

Fridgen

2009

In an effort to spectroscopically determine the structures of solvated ions composed of nucleic acid bases and amino acids, methods for their gas-phase synthesis have been studied. Ions were electrosprayed and solvated in the accumulation cell of a hybrid Q-FTICR filled with methanol or water vapor at ϳ10 Ϫ2 bar. There were subsequently transferred to the FTICR cell at 10 Ϫ10 mbar. Following their isolation in the FTICR, they can be investigated by studying their unimolecular blackbody infrared radiative dissociation (BIRD) or infrared multiple photon dissociation (IRMPD) spectroscopy. The IRMPD spectra for (Ade) 2 Li ϩ and (Ade) 2 Li(H 2 O) ϩ are reported and compared as well as BIRD rate constants for multiply solvated and metalated adenine ions. . The structural properties are typically deduced from fundamental studies of their thermochemistries, reactivities, and more recently, the vibrational spectroscopy of gaseous ions [2]. The ultimate purpose and challenge for studying the physical properties of sequentially solvated ions is to extrapolate to, or contrast these properties with, those in the solution phase especially for biologically interesting ions. Mass spectrometry has become a powerful technique for investigating biomolecules following the development of electrospray ionization (ESI) [3] and matrix-assisted laser desorption/ionization (MALDI) [4 -6]. Noncovalently bound biological complexes can be transferred from aqueous solutions to the gas phase by ESI for further study of the completely desolvated complex. In some instances a small amount of solvated ions have been reported from electrospray allowing the structure, reactivity and thermochemistry of the hydrated ions to be studied [7]. Lee et al.[8] studied extensively hydrated peptides from an electrospray source by operating the capillary at room-temperature, with no nebulizer or drying gas, and optimizing the potentials in the electrospray source. These ions were found to be cooled to between 130 and 150 K by evaporation of water without drying gas, effectively freezing the biomolecules. RodriguezCruz et al. [9] studied doubly protonated gramicidin S ions with up to 50 water molecules attached in a modified instrument with a home-built electrospray source equipped with a heated capillary inlet. They formed the ions under "gentle" electrospray conditions and later described two possible mechanisms for formation of hydrated ions by ESI [10], condensation of solvent onto ions due to expansion inside the ESI interface, and/or solvent evaporation of more extensively hydrated ions or electrospray droplets. The extent of hydration of gas-phase gramicidin S (M ϩ 2H) 2ϩ ions was observed to decrease with an increase in the temperature of the capillary.Rodriguez-Cruz and Williams [11] also studied solvent exchange reactions of hydrated divalent alkaline earth metals with benzene by ESI Fourier-Transform mass spectrometry (FTMS) at room temperature. Aqueous solutions of metal chloride salts were introduced to the mass spectrometer by nanoelectrospray. Me...