@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 {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.}
}
@article {4029,
	title = {Acid-induced unfolding of cytochrome c at different methanol concentrations: Electrospray ionization mass spectrometry specifically monitors changes in the tertiary structure},
	journal = {Biochemistry},
	volume = {36},
	number = {40},
	year = {1997},
	note = {ISI Document Delivery No.: YA264Times Cited: 132Cited Reference Count: 51},
	month = {Oct},
	pages = {12296-12302},
	type = {Article},
	abstract = {The acid-induced denaturation of ferricytochrome c (cyt c) was examined in aqueous solutions containing different concentrations of methanol by electrospray ionization mass spectrometry (ESI MS) and optical spectroscopy. Circular dichroism, fluorescence, and absorption spectroscopy show that at a low concentration of methanol (3\%) a decrease in pH induces a cooperative unfolding transition at around pH 2.6 that is accompanied by a breakdown of the native secondary and tertiary structure of the protein. In 50\% methanol the breakdown of the tertiary structure occurs at around pH 4.0, whereas the alpha-helical content remains largely intact over the whole pH range studied. In ESI MS different protein conformations in solution are monitored by the different charge state distributions they generate during ESI. The ESI mass spectra recorded at near-neutral pH for both methanol concentrations are very similar and show a maximum at (cyt c + 8H(+))8(+). Despite the different conformations of the protein in solution, the acid-denatured states for the two methanol concentrations also show very similar mass spectra with a maximum at (cyt c + 17H(+))17(+). This indicates that the charge state distribution generated during EST is not sensitive to the differences in the secondary structure of the denatured protein. The observed transition from low to high charge states is due to the breakdown of the tertiary structure in both cases. These findings suggest that ESI MS might be a general method to selectively monitor changes in the tertiary structure of proteins.},
	keywords = {ALPHA-HELIX, BETA-LACTOGLOBULIN, CIRCULAR-DICHROISM, DENATURED, FERRICYTOCHROME-C, HEME, PARTIALLY FOLDED STATE, PROBING CONFORMATIONAL-CHANGES, PROTEIN, STATE, TRIFLUOROETHANOL},
	isbn = {0006-2960},
	url = {<Go to ISI>://A1997YA26400034},
	author = {Konermann, L. and Douglas, D. J.}
}
@article {7358,
	title = {MONOMER AND EXCIMER FLUORESCENCE OF HORSE PLASMA GELSOLIN LABELED WITH N-(1-PYRENYL)IODOACETAMIDE},
	journal = {Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire},
	volume = {70},
	number = {7},
	year = {1992},
	note = {ISI Document Delivery No.: JP667Times Cited: 3Cited Reference Count: 27},
	month = {Jul},
	pages = {573-578},
	type = {Article},
	abstract = {Horse plasma gelsolin was labelled with the sulfhydryl-specific fluorescent reagent N-(1-pyrenyl)iodoacetamide. The level of incorporation of probe was 1.6 +/- 0.3 mol pyrene/mol gelsolin. The circular dichroism spectrum of pyrenyl-gelsolin and its ability to interact with muscle actin were not different from that found for unmodified gelsolin. The emission from pyrenyl-gelsolin was dominated by a broad emission band centred near 483 nm, characteristic of the presence of pyrene excimers. Analysis of excitation spectra for the monomer and excimer-type fluorescence suggested that ground-state interactions may occur between adjacent pyrenes in the gelsolin structure. In the case either of excimer formation or of ground-state pyrene-pyrene interactions in doubly labelled gelsolin molecules, the modified Cys residues must be in close proximity in the folded protein structure. Thermal denaturation of gelsolin could be monitored by observing the decrease in excimer emission that accompanied heating and unfolding of the tertiary structure. While heat treatment alone did not eliminate excimer fluorescence, digestion of gelsolin with chymotrypsin completely abolished such emission. Also, pyrenyl-gelsolin prepared and studied in 6 M guanidine-HCl exhibited fluorescence characteristic of pyrene monomers exclusively.},
	keywords = {ACTIN-FILAMENTS, BINDING, CIRCULAR-DICHROISM, denaturation, FLUORESCENCE LIFETIME, gelsolin, POLYMERIZATION, PROBE, PROTEIN, PYRENE EXCIMER FLUORESCENCE, PYRENE-ACTIN, STATE, thermal, TROPOMYOSIN},
	isbn = {0829-8211},
	url = {<Go to ISI>://A1992JP66700008},
	author = {Silva, B. E. R. and Koepf, E. K. and Burtnick, L. D. and Turro, N. J.}
}
@article {7352,
	title = {STABILIZATION OF THE STRUCTURE OF HORSE PLASMA VITAMIN-D BINDING-PROTEIN BY DISULFIDE BONDS},
	journal = {Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire},
	volume = {70},
	number = {1},
	year = {1992},
	note = {ISI Document Delivery No.: HG742Times Cited: 1Cited Reference Count: 27},
	month = {Jan},
	pages = {10-15},
	type = {Article},
	abstract = {Vitamin D binding protein (DBP) was isolated from horse plasma in a four-step procedure that involved Affi-Gel Blue affinity chromatography, gel filtration, hydroxylapatite chromatography, and anion exchange high-pressure liquid chromatography. The yield of DBP from 80 mL of plasma was 6-7 mg. Horse plasma DBP closely resembles other plasma DBPs, being a tryptophan-free protein of M(r) 53 000. It is able to bind to and block the polymerization of monomeric actin. The secondary structure of DBP was calculated from circular dichroism measurements to be 39\% alpha-helix, 42\% beta-sheet, and 19\% random coil. Circular dichroism and fluorescence studies revealed that the disulfide bonds of DBP contribute substantial structural stabilization to the molecule with respect to thermal denaturation. The thermal stability of DBP can be used to advantage. Incorporation of a brief treatment at 70-degrees-C into the preparative scheme enables omission of one chromatographic step, without detectable alteration of the purified product.},
	keywords = {actin, circular dichroism, CIRCULAR-DICHROISM, COMPLEX, denaturation, DISULFIDE BONDS, FLUORESCENCE, GC-GLOBULIN, POLYMERIZATION, RAT, SERUM, thermal, TROPOMYOSIN, VITAMIN-D BINDING PROTEIN},
	isbn = {0829-8211},
	url = {<Go to ISI>://A1992HG74200002},
	author = {Robinson, R. C. and Burtnick, L. D.}
}
