@article {2309,
	title = {Conformations of Gas-Phase Ions of Ubiquitin, Cytochrome c, Apomyoglobin, and beta-Lactoglobulin Produced from Two Different Solution Conformations},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {19},
	number = {12},
	year = {2008},
	note = {ISI Document Delivery No.: 385IWTimes Cited: 2Cited Reference Count: 36Wright, P. John Zhang, Jianmin Douglas, D. J.},
	month = {Dec},
	pages = {1906-1913},
	type = {Article},
	abstract = {At low pH in solutions of 50\% methanol, proteins form expanded denatured states (the "H" state). In 90\% methanol, proteins form expanded helical denatured states with artificial alpha-helices (the "H-c" state). Gas-phase ions of ubiquitin, cytochrome c, apomyoglobin, and native and disulfide-reduced beta-lactoglobulin were formed by electrospray ionization (EST) of the proteins from the H and H-c states in solution. Both states in solution produce the same charge states in EST. The conformations of the ions were studied with cross section measurements and gas-phase H/D exchange experiments. The cross sections show that the ions retain considerable folded structure. For a given protein and given charge state, ions produced from the H and H-c states showed the same cross sections (within similar to 1\%). Ions of cytochrome c, apomyoglobin, and native and reduced beta-lactoglobulin of a given charge state showed no differences in H/D exchange level when produced from the H or H-c state. However, ubiquitin ions produced from the H-c state consistently exchange fewer (similar to 13\%) hydrogens than ions produced from the H state, suggesting that in this case the gas-phase protein ions retain some memory of their solution conformations. (J Am Soc Mass Spectrom 2008, 19, 1906-1913) (c) 2008 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry},
	keywords = {CIRCULAR-DICHROISM, COLLISION CROSS-SECTIONS, H/D EXCHANGE, HYDROGEN/DEUTERIUM EXCHANGE, IONIZATION MASS-SPECTROMETRY, MYOGLOBIN, OF-FLIGHT, PROTEIN IONS, STABILITY, SYSTEM, TRAP},
	isbn = {1044-0305},
	url = {<Go to ISI>://000261808900023},
	author = {Wright, P. J. and Zhang, J. M. and Douglas, D. J.}
}
@article {449,
	title = {Collision cross sections of gas phase DNA ions},
	journal = {International Journal of Mass Spectrometry},
	volume = {219},
	number = {1},
	year = {2002},
	note = {ISI Document Delivery No.: 591BVTimes Cited: 4Cited Reference Count: 27},
	month = {Aug},
	pages = {161-170},
	type = {Article},
	abstract = {Collision cross sections of negative ions of a 28-, 40- and 55-mer of single stranded DNA have been measured by an energy loss method, and compared to collision cross sections of proteins of nearly the same molecular weight-ubiquitin, cytochrome c and apomyoglobin, respectively. The oligonucleotides produce negative charge states in electrospray ionization (ESI) similar to the positive charge states produced by the proteins denatured in solution. Cross sections for deoxynucleotide ions increase with charge state in a manner similar to those of protein ions. However, for a given molecular weight and charge state, the cross sections of the oligodeoxynucleotide ions are about 22\% lower than those of the proteins. (C) 2002 Elsevier Science B.V. All rights reserved.},
	keywords = {collision cross sections, CONFORMATION, CONFORMERS, DNA ions, ELECTROSPRAY MASS-SPECTROMETRY, gas phase, MYOGLOBIN, PROTEIN IONS, SEQUENCE, VACUUM},
	isbn = {1387-3806},
	url = {<Go to ISI>://000177860600015},
	author = {Moradian, A. and Scalf, M. and Westphall, M. S. and Smith, L. M. and Douglas, D. J.}
}
@article {5053,
	title = {Detection of noncovalent complex between alpha-amylase and its microbial inhibitor tendamistat by electrospray ionization mass spectrometry},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {15},
	number = {2},
	year = {2001},
	note = {ISI Document Delivery No.: 396KYTimes Cited: 11Cited Reference Count: 58},
	pages = {89-96},
	type = {Article},
	abstract = {Electrospray ionization mass spectrometry (ESI-MS) is now routinely used for detection of noncovalent complexes. However, detection of noncovalent protein-protein complexes is not a widespread practice and still produces some challenges for mass spectrometrists. Here we demonstrate the detection of a noncovalent protein-protein complex between alpha -amylase and its microbial inhibitor tendamistat using ESI-MS. Crude porcine pancreatic alpha -amylase was purified using a glycogen precipitation method. Noncovalent complexes between porcine pancreatic alpha -amylase and its microbial inhibitor tendamistat are probed and detected using ESI-MS. The atmosphere-vacuum ESI conditions along with solution conditions and the ratio of inhibitor over enzyme strongly affect the detection of noncovalent complexes in the gas phase. ESI mass spectra of alpha -amylase at pH 7 exhibited charge states significantly lower than that reported previously, which is indicative of a native protein conformation necessary to produce a noncovalent complex. Detection of noncovalent complexes in the gas phase suggests that further use of conventional biochemical approaches to provide a qualitative, and in some cases even quantitative, characterization of equilibria of noncovalent complexes in solution is possible. Copyright (C) 2001 John Wiley \& Sons, Ltd.},
	keywords = {ANALYTICAL ULTRACENTRIFUGATION, BINDING, CRYSTAL-STRUCTURE, CYTOCHROME-C, GAS-PHASE, HEME, MYOGLOBIN, PROBING CONFORMATIONAL-CHANGES, PROTEIN PROTEINASE-INHIBITORS, RECOGNITION SITES},
	isbn = {0951-4198},
	url = {<Go to ISI>://000166636600003},
	author = {Douglas, D. J. and Collings, B. A. and Numao, S. and Nesatyy, V. J.}
}
@article {5190,
	title = {Ion fragmentation in an electrospray ionization mass spectrometer interface with different gases},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {15},
	number = {4},
	year = {2001},
	note = {ISI Document Delivery No.: 405PTTimes Cited: 12Cited Reference Count: 43},
	pages = {249-257},
	type = {Article},
	abstract = {Nitrogen, argon, and krypton are used as curtain gases in an electrospray ionization mass spectrometer in an attempt to study the effect of these gases on the extent of ion fragmentation between the orifice and the skimmer of the interface region. A previously published collision model predicts that the degree of ion fragmentation increases with increasing mass of the curtain gas. However, the fragmentation yields are found to be the opposite to that expected. It is believed that the reversed trend with argon and krypton is caused by condensation of the gases within the free jet expansion between the orifice and the skimmer. A condensation parameter can be used to predict the degree of clustering of gases within a free jet expansion. When the condensation parameter is minimized, the predicted trend of fragmentation with mass is observed. Copyright (C) 2001 John Wiley \& Sons, Ltd.},
	keywords = {CONDENSATION, FREE-JET EXPANSIONS, INDUCED DISSOCIATION, LIQUID-HELIUM CLUSTERS, MYOGLOBIN, PERFORMANCE, PROTEIN IDENTIFICATION, SPECTROSCOPY, TECHNOLOGY, TEMPERATURE},
	isbn = {0951-4198},
	url = {<Go to ISI>://000167168800002},
	author = {Schneider, B. S. and Douglas, D. J. and Chan, D. D. Y.}
}
@article {5004,
	title = {The methanol-induced conformational transitions of beta-lactoglobulin, cytochrome c, and ubiquitin at low pH: A study by electrospray ionization mass spectrometry},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {12},
	number = {3},
	year = {2001},
	note = {ISI Document Delivery No.: 408WBTimes Cited: 45Cited Reference Count: 51},
	month = {Mar},
	pages = {317-328},
	type = {Article},
	abstract = {The methanol-induced conformational transitions under acidic conditions for beta -lactoglobulin, cytochrome c, and ubiquitin, representing three different classes of proteins with beta -sheets, alpha -helices, and both alpha -helices and beta -sheets, respectively, are studied under equilibrium conditions by electrospray ionization mass spectrometry (ESI-MS). The folding states of proteins in solution are monitored by the charge state distributions that they produce during ESI and by hydrogen/deuterium (H/D) exchange followed by ESI-MS. The changes in charge state distributions are correlated with earlier studies by optical and other methods which have shown that, in methanol, these proteins form partially unfolded intermediates with induced ct-helix structure. Intermediate states formed at about 35\% methanol concentration are found to give bimodal charge state distributions. The same rate of H/D exchange is shown by the two contributions to the bimodal distributions. This suggests the intermediates are highly flexible and may consist of a mixture of two or more rapidly interconverting conformers. H/D exchange of proteins followed by ESI-MS shows that helical denatured states, populated at around 50\% methanol concentration, transform into more protected structures with further increases in methanol concentration, consistent with previous circular dicroism studies. These more protected structures still produce high charge states in ESI, similar to those of the fully denatured proteins. (C) 2001 American Society for Mass Spectrometry.},
	keywords = {2-DIMENSIONAL NMR, ALPHA-HELIX, AMIDE HYDROGEN-EXCHANGE, COMPLETE SEQUENCE, DENATURED STATES, DEUTERIUM-EXCHANGE, INTERMEDIATE, MYOGLOBIN, PROTEIN, SOLVENT},
	isbn = {1044-0305},
	url = {<Go to ISI>://000167349200010},
	author = {Babu, K. R. and Moradian, A. and Douglas, D. J.}
}
@article {5226,
	title = {Reaction of human myoglobin and peroxynitrite: Characterizing biomarkers for myoglobin-derived oxidative stress},
	journal = {Biochemical and Biophysical Research Communications},
	volume = {286},
	number = {2},
	year = {2001},
	note = {ISI Document Delivery No.: 465TNTimes Cited: 11Cited Reference Count: 32},
	month = {Aug},
	pages = {352-356},
	type = {Article},
	abstract = {Mixtures of human myoglobin (Mb) (or the Y103F variant of human Mb), authentic peroxynitrite (ONOO-, ONOO-:protein 2 mol/mol), and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gave radicals adducts at cysteine-110 (DMPO-C110) that are detected directly by electron paramagnetic magnetic spectroscopy (EPR). DMPO-C110 was detected exclusively over a range of DMPO concentrations (DMPO:protein ratios 25-100 mol/mol). Treatment of human Mb (or Y103F Mb) with the ONOO- generator 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium (SIN-1) chloride (ONOO-: protein 5 mol/mol) yielded a cross-linked Mb dimer as judged by SDS-PAGE analyses. Addition of DMPO or carbonate effectively eliminated the cross-linked product. Mass analyses of samples containing human Mb (or Y103F Mb), carbonate, and ONOO- indicated that nitration occurs exclusively at Y103. Thus, reaction of human Mb and ONOO- yields specific products that depend on the presence or absence of physiological concentrations of carbonate. These products may serve as biomarkers for the participation of Mb-derived radicals in the oxidative damage associated with myocardial reperfusion injury. (C) 2001 Academic Press.},
	keywords = {ARRHYTHMIAS, free radical, GENERATION, HYDROGEN-PEROXIDE, ischaemia reperfusion injury, MECHANISMS, MYOGLOBIN, NITRATION, NITRIC-OXIDE, nitro-tyrosine, peroxynitrite, protein-thiyl radical, radicals, REPERFUSION INJURY, SITE-DIRECTED MUTAGENESIS, SUPEROXIDE, SYSTEMS},
	isbn = {0006-291X},
	url = {<Go to ISI>://000170606200020},
	author = {Witting, P. K. and Mauk, A. G. and Douglas, D. J. and Stocker, R.}
}
@article {4365,
	title = {Conformation of native, reduced and [5-55](Ala) bovine pancreatic trypsin inhibitor in the gas phase},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {12},
	number = {1},
	year = {1998},
	note = {ISI Document Delivery No.: YQ873Times Cited: 14Cited Reference Count: 46},
	pages = {40-44},
	type = {Article},
	abstract = {Collision cross sections have been measured for gas phase ions of native oxidized bovine pancreatic trypsin inhibitor (BPTI), native reduced BPTI and a mutant form of BPTI containing a single disulphide bond between residues 5 and 55 ([5-55](Ala) BPTI). Cross sections for [5-55](Ala) BPTI and reduced BPTI were 9\% and 17\% greater respectively than those for native BPTI, Cross sections for native BPTI were smaller than previous estimates from the crystal structure but in reasonable agreement with values calculated from the radius of gyration determined by x-ray scattering from solution BPTI. The increase in cross section for reduced BPTI over native BPTI is similar to that seen in molecular dynamics simulations, The results show that the disulphide bonds of BPTI contribute to the folding of the gas phase ions, but that even in the absence of disulphide bonds the protein ions maintain compact structures. Comparisons to relative areas calculated from hydrodynamic radii of BPTI in solution suggest that when disulphide linkages are removed, BPTI in the gas phase unfolds less than BPTI in solution. (C) 1998 John Wiley \& Sons, Ltd.},
	keywords = {BPTI, DISULFIDE BOND, IONS, MASS-SPECTROMETRY, MOLECULAR-DYNAMICS SIMULATIONS, MYOGLOBIN, protein dynamics, STABILITY},
	isbn = {0951-4198},
	url = {<Go to ISI>://000071433000008},
	author = {Nesatiy, V. and Chen, Y. L. and Collings, B. A. and Douglas, D. J.}
}
@article {4227,
	title = {Stability of a highly charged noncovalent complex in the gas phase: Holomyoglobin},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {12},
	number = {15},
	year = {1998},
	note = {ISI Document Delivery No.: 105GATimes Cited: 33Cited Reference Count: 56},
	pages = {1003-1010},
	type = {Article},
	abstract = {Gas phase holomyoglobin (hMb) ions in charge states +7 to +21 were formed by electrospray ionization in combination with a continuous-flow mixing apparatus. Collision cross section measurements show that the highly charged ions are somewhat unfolded in comparison to low charge states but still retain a considerable degree of folding. A new collision model is presented which calculates the relative energies transferred to complexes in tandem mass spectrometry. Tandem mass spectrometry and ion trapping experiments both show that the energies required to dissociate heme from the highly charged heme-protein complexes in the gas phase are similar to those of low charge states, previously shown in literature ion cyclotron resonance experiments to be 0.7-1.0 eV, These energies are comparable to those of the heme binding energy in solution. The results suggest that even for the highly charged hMb ions which have unfolded somewhat, the heme-protein interactions remain relatively unperturbed. (C) 1998 John Wiley \& Sons, Ltd.},
	keywords = {CONFORMATION, CYTOCHROME-C, ELECTROSPRAY-IONIZATION, ion-molecule, IONIZATION MASS-SPECTROMETRY, METMYOGLOBIN, MYOGLOBIN, PROTEIN IONS, PROTON-TRANSFER REACTIVITY, QUADRUPOLE, reaction},
	isbn = {0951-4198},
	url = {<Go to ISI>://000075063300003},
	author = {Chen, Y. L. and Campbell, J. M. and Collings, B. A. and Konermann, L. and Douglas, D. J.}
}
@article {4313,
	title = {Unfolding of proteins monitored by electrospray ionization mass spectrometry: A comparison of positive and negative ion modes},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {9},
	number = {12},
	year = {1998},
	note = {ISI Document Delivery No.: 141FPTimes Cited: 72Cited Reference Count: 56},
	month = {Dec},
	pages = {1248-1254},
	type = {Article},
	abstract = {Electrospray ionization (ESI) mass spectrometry (MS) in both the positive and negative ion mode has been used to study protein unfolding transitions of lysozyme, cytochrome c (cyt c), and ubiquitin in solution. As expected, ESI of unfolded lysozyme leads to the formation of substantially higher charge states than the tightly folded protein in both modes of operation. Surprisingly, the acid-induced unfolding of cyt c as well as the acid and the base-induced unfolding of ubiquitin show different behavior: In these three cases protein unfolding only leads to marginal changes in the negative ion charge state distributions, whereas in the positive ion mode pronounced shifts to higher charge states are observed. This shows that ESI MS in the negative ion mode as a method for probing conformational changes of proteins in solution should be treated with caution. The data presented in this work provide further evidence that the conformation of a protein in solution not its charge state is the predominant factor for determining the ESI charge slate distribution in the positive ion mode. Furthermore, these data support the hypothesis of a recent study (Konermann and Douglas, Biochemistry 1997, 36, 12296-12302) which suggested that ESI in the positive ion mode is not sensitive to changes in the secondary structure of proteins but only to changes in the tertiary structure. (C) 1998 American Society for Mass Spectrometry.},
	keywords = {A-STATE, BINDING, CIRCULAR-DICHROISM, CYTOCHROME-C, HYDROGEN-DEUTERIUM EXCHANGE, INDUCED CONFORMATIONAL-CHANGES, MYOGLOBIN, NUCLEAR-MAGNETIC-RESONANCE, SITES, SPECTRA, UBIQUITIN},
	isbn = {1044-0305},
	url = {<Go to ISI>://000077132600002},
	author = {Konermann, L. and Douglas, D. J.}
}
