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453 results on '"Bowers, Michael T."'

28. Characterization of phosphorylated peptides using traveling wave-based and drift cell ion mobility mass spectrometry

Author

Thalassinos, Konstantinos, Grabenauer, Megan, Slade, Susan E., Hilton, Gillian R., Bowers, Michael T., and Scrivens, James H.

Subjects
Phosphorylation -- Research, Mass spectrometry -- Methods, Peptides -- Properties, Ionic mobility -- Research, Post-translational modification -- Research, Wave propagation -- Research, Cells -- Motility, Cells -- Research, Chemistry
Abstract

Phosphorylation is one the most studied and important post translational modifications. Nano electrospray mass spectrometry coupled with traveling wave (T-Wave)-based ion mobility has been used to filter for phosphorylated peptides in tryptic protein digests. T-Wave parameters have been optimized to maximize the separation between phosphorylated and non-phosphorylated peptides. A method to calibrate the T-Wave device, to provide estimates of collision cross sections, is presented, and these estimates are in excellent agreement with values obtained on drift cell instrumentation. Phosphorylated peptides have smaller cross sections which enables their separation from non-phosphorylated peptides of the same m/z. Post-mobility fragmentation is used to obtain the primary sequence for peptides of interest. This approach is shown to have potential as an additional screen for phosphorylated peptides, where up to 40% of observed peptides can be eliminated from the study.

Published
2009

33. Hydration of mononucleotides

Author

Dengfeng Liu, Wyttenbach, Thomas, and Bowers, Michael T.

Subjects
Nucleotides -- Chemical properties, Hydration (Chemistry) -- Analysis, Water -- Chemical properties, Chemistry
Abstract

The interaction of individual water molecules with mononucleotides is investigated. The insight gained on nucleotide stabilization by individual water molecules is used to discuss the competition between hydration of individual nucleotides and Watson-Crick base pairing.

Published
2006

34. PNA/dsDNA complexes: Site specific binding and dsDNA biosensor applications

Author

Shammel Baker, Erin, Janice W. Hong, Gaylord, Brent S., Bazan, Guillermo C., and Bowers, Michael T.

Subjects
DNA -- Research, Energy transformation -- Research, Chemistry
Abstract

A biosensor mechanism for dsDNA based on peptide nucleic acid (PNA)/dsDNA based on recognitions properties and the action of a cationic conjugated polymer is presented. Fluorescence resonance energy transfer (FRET) experiments performed using a water-soluble cationic conjugated polymer as the donor and a dye-labeled PNA as the acceptor confirm specific PNA/dsDNA binding by a positive signal with complementary dsDNA.

Published
2006

35. Cyclo[n]pyrroles: Size and site-specific binding to G-quadruplexes

Author

Baker, Erin Shammel, Jeong Tae Lee, Sessler, Jonathan L., and Bowers, Michael T.

Subjects
Pyrrole -- Atomic properties, Pyrrole -- Chemical properties, Molecular dynamics -- Research, Telomeres -- Atomic properties, Telomeres -- Chemical properties, Chemistry
Abstract

A series of diprotonated cyclo[n]pyrroles (when n=6,7 and 8) was each added to human telomere repeat sequence d(T2AG3)4 and examined with mass spectrometry, ion mobility and molecular dynamics calculations. Diprotonated cyclo(n)pyrroles represent a set of expanded prophyrin analogues with structures similar to that of telomestain, a natural product known to bind to and stabilize G-quadruplexes.

Published
2006

39. Gas-phase conformations of deprotonated and protonated mononucleotides determined by ion mobility and theoretical modeling

Author

Gidden, Jennifer, Bowers, Michael T., Leitner, David M., Das, Bijan, Seddon, Kenneth R., De Souza, Herminio C., and Szydlowski, Jerzy

Subjects
Chemistry, Physical and theoretical -- Research, Nitrogen -- Research, Nitrogen -- Chemical properties, Ions -- Research, Ions -- Chemical properties, Density functionals -- Usage, Density functionals -- Observations, Chemicals, plastics and rubber industries
Abstract

Studies done on the preferred gas-phase conformations of a series of deprotonated and protonated mononucleotides by ion mobility experiments and theoretical modeling calculations is reported. Density Functional Theory (DFT) calculations indicate that the most energetically favored sites for protonation are N3 on dAMP, N7 on dGMP, N3 on dCMP, and the phosphate group on dTMP.

Published
2003

40. The effect of the initial water of hydration on the energetics, structures, and H/D exchange mechanism of a family of pentapeptides: An experimental and theoretical study

Author

Wyttenbach, Thomas, Paizs, Bela, Barran, Perdita, Bowers, Michael T., Breci, Linda, Wysocki, Vicki H., Dengfeng Liu, and Suhai, Sandor

Subjects
Molecular structure -- Research, Peptides -- Research, Peptides -- Structure, Chemistry
Abstract

A series of gas-phase experiments and extensive theoretical modeling was done on the family of singly protonated peptides AARAA, Ac-AARAA and AARAA-OMe to examine the effect of the initial water of hydration on the energetics, structures and the mechanism of H/D exchange on the peptides. It is concluded that (AARAA)H(super +) is capable of undergoing faster H/D exchange with D2O as compared to (AC-AARAA)H(super +) and (AARAA-OMe)H(super +).

Published
2003

41. Sequential hydration of small protonated peptides

Author

Dengfeng Liu, Wyttenbach, Thomas, Barran, Perdita E., and Bowers, Michael T.

Subjects
Hydrates -- Structure, Hydrates -- Chemical properties, Peptides -- Chemical properties, Ionization -- Research, Chemistry
Abstract

A study was conducted on the sequential addition of water molecules to a series of small protonated peptides by equilibrium experiments using electrospray ionization combined with drift cell techniques. The experimental data was compared to theoretical structures of selected hydrated species obtained by molecular mechanics simulations.

Published
2003

42. Conformation and luminescence of isolated molecular semiconductor molecules

Author

Summers, Melissa A.; Bowers, Michael T., Kemper, Paul R.; Buratto, Steven K., Bushnell, John E., Robinson, Matthew R., and Bazan, Guillermo C.

Subjects
Fluorescence spectroscopy -- Usage, Molecules -- Research, Molecules -- Chemical properties, Molecules -- Atomic properties, Chemistry
Abstract

Direct comparisons of the detailed structures of two small molecule organic semiconductors and their luminescence properties on a single molecule level are presented. The combination of techniques (ion mobility and single molecule fluorescence spectroscopy) provides a level of information far beyond that obtained via any other analytical technique.

Published
2003

43. Catalytic gas phase oxidation of Methanol to Formaldehyde

Author

Waters, Tom, O'Hair, Richard A.J., Wedd, Anthony G., and Bowers, Michael T.

Subjects
Oxidation-reduction reaction -- Research, Formaldehyde -- Chemical properties, Methanol -- Chemical properties, Chemistry
Abstract

Two gas-phase catalytic cycles is presented for the oxidation of primary and secondary alcohols to aldehydes and ketones, with a binuclear dimolybdate center acting as the catalyst. The nature of the reactions is probed by variation of the substrate alcohols and by variation of the reactive center. It is also detected by multistage mass spectrometry experiments.

Published
2003

44. On the dissolution processes of Na2l(super +) and Na3l2(super +) with the association of water molecules: mechanistic and energetic details

Author

Zhang, Qiang, Carpenter, Catherine J., Kemper, Paul R., Bowers, Michael T., Lednev, Igor K., Wilcox, Craig S., and Finegold, David N.

Subjects
Molecular dynamics -- Research, Sodium compounds -- Chemical properties, Chemistry
Abstract

The sequential association energies for one through six water molecules clustering to Na2l(super +) as well as one and two water molecules clustering to Na3l2(super +) are measured. The association energies show a pairwise behavior, indicating a symmetric association of water molecules to the linear Na2l(super +) and Na3l2(super +) ions.

Published
2003

45. Relaxation-assisted separation of chemical sites in NMR spectroscopy of static solids

Author

Lupulescu, Adonis, Kotecha, Mrignayani, Frydman, Lucio, and Bowers, Michael T.

Subjects
Chemistry, Physical and theoretical -- Research, Nuclear magnetic resonance spectroscopy -- Usage, Chemistry
Abstract

The potential use of relaxation times toward the resolution of inequivalent chemical sites in the NMR spectroscopy of powdered or disordered samples is discussed. The proposal is motivated by the significant differences that could often be detected in the relaxation behavior of sites in solids.

Published
2003

46. Mechanism and energetics of intramolecular hydrogen transfer in amide and peptide radicals and cation-radicals

Author

Turecek, Frantisek, Syrstad, Erik A., Kemper, Paul R., Bowers, Michael T., Lednev, Igor K., Wilcox, Craig S., and Finegold, David N.

Subjects
Radicals (Chemistry) -- Research, Hydrogen -- Chemical properties, Amides -- Chemical properties, Chemistry
Abstract

Intramolecular hydrogen transfer in five model amide and peptide radicals and cation-radicals is investigated by combined B3LYP-MP2 calculations. Hypervalent ammonium radicals produced by electron capture in protonated peptides undergo competitive elimination of ammonia, H-atom loss and H-atom migration to neighboring amide carbonyls.

Published
2003

47. A route for bulk separation of semiconducting from metallic single-wall carbon nanotubes

Author

Chattopadhyay, Debjit, Galeska, Izabela, Papadimitrakopoulos, Fotios, Bowers, Michael T., Wilcox, Craig S., and Finegold, David N.

Subjects
Nanotubes -- Research, Carbon compounds -- Chemical properties, Raman spectroscopy -- Research, Chemistry
Abstract

Substantial separation of single-wall carbon nanotubes (SWNTs) according to type (metallic versus semiconducting) is achieved for HIPco and laser-ablated SWNTs. The affinity of amine groups for semiconducting SWNTs provides a venue for the selective precipitation of metallic SWNTs upon increasing dispersion concentration, as indicated by Raman investigations.

Published
2003

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