@article {4726,
	title = {Methanol-induced conformations of myoglobin at pH 4.0},
	journal = {Biochemistry},
	volume = {39},
	number = {47},
	year = {2000},
	note = {ISI Document Delivery No.: 378UETimes Cited: 62Cited Reference Count: 78},
	month = {Nov},
	pages = {14702-14710},
	type = {Article},
	abstract = {The equilibrium methanol-induced conformation changes of holomyoglobin (hMb) at pH 4.0 have been studied by circular dichroism, tryptophan fluorescence, and Soret band absorption and by electrospray ionization mass spectrometry (ESI-MS). Optical spectra show the following: (1) In 35-40\% (v/v) methanol/water, the native-like secondary structure remains, the tertiary structure is lost, the heme protein interactions are decreased, and a folding intermediate is formed. (2) In 50\% methanol, heme is lost from the protein, and there is a small decrease in helicity together with a loss of tertiary structure. (3) At > 60\% methanol, the helicity increases and the apoprotein goes into a helical denatured state. The conformations are also probed by the charge states produced in ESI-MS and by hydrogen/deuterium (H/D) exchange with mass measurement by ESI-MS. At 0-30\% methanol, native hMb produces relatively low charge states (9(+)-13(+)) in ESI-MS and exchanges relatively few hydrogens. In 35-40\% methanol, at which an intermediate is formed, there is a bimodal distribution of hMb ions with both low (9(+)-13(+)) and high (14(+)-23(+)) charge states and also a high charge state distribution (12(+)-26(+)) of apomyoglobin (aMb) ions. Low and high charge states of hMb and a high charge state of aMb all show the same H/D exchange rate, indicating that an unfolded hMb intermediate interconverts between folded hMb and unfolded aMb. The charge state distribution for the unfolded hMb intermediate observed here is similar to that of the recently reported transient intermediate formed during the acid denaturation of hMb. At 50\% alcohol the protein produces predominantly high charge states of aMb ions and shows H/D exchange rates close to those of the acid-denatured protein. H/D exchange of the helical denatured protein at alcohol concentrations >60\%, at which high charge states of aMb are produced, shows that the protein structure is more protected than at similar to 50\% methanol.},
	keywords = {AMIDE HYDROGEN-EXCHANGE, APOMYOGLOBIN, BETA-LACTOGLOBULIN, CYTOCHROME-C, ELECTROSPRAY-IONIZATION, FOLDING INTERMEDIATE, IONIZATION MASS-SPECTROMETRY, MOLTEN GLOBULE INTERMEDIATE, SPERM-WHALE, STRUCTURAL-CHARACTERIZATION, X-RAY-SCATTERING},
	isbn = {0006-2960},
	url = {<Go to ISI>://000165602400040},
	author = {Babu, K. R. 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.}
}
