@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 {4030,
	title = {Acid-induced denaturation of myoglobin studied by time-resolved electrospray ionization mass spectrometry},
	journal = {Biochemistry},
	volume = {36},
	number = {21},
	year = {1997},
	note = {ISI Document Delivery No.: XB321Times Cited: 74Cited Reference Count: 43},
	month = {May},
	pages = {6448-6454},
	type = {Article},
	abstract = {The acid-induced denaturation of holo-myoglobin (hMb) following a pH-jump from 6.5 to 3.2 has been studied by electrospray ionization (ESI) mass spectrometry in combination with a continuous flow mixing technique (time-resolved ESI MS). Different protein conformations are detected by the different charge state distributions that they generate during ESI. The changes in intensity of the peaks in the mass spectrum as a function of time can be described by two exponential lifetimes of 0.38 +/- 0.06 s and 6.1 +/- 0.5 s, respectively. The acid-induced denaturation of hMb was also studied in stopped-flow experiments by monitoring changes in the Soret absorption. The lifetimes measured by this method are in good agreement with those obtained by time-resolved ESI MS. The shorter lifetime is associated with the formation of a transient intermediate which shows the mass of the intact heme-protein complex but leads to the formation of much higher charge states during ESI than native hMb at pH 6.5. This form of hMb has an absorption spectrum similar to that of the native protein, indicating a relatively unperturbed chromophore environment inside the heme binding pocket. The intermediate can thus be characterized as an unfolded form of hMb with essentially intact heme-protein interactions. The longer of the two lifetimes is associated with the formation of a product which has a blue-shifted absorption spectrum with a much lower maximum absorption coefficient than observed for native hMb. In the ESI mass spectrum, this product appears as the apoprotein with high charge states which indicates the disruption of the native heme-protein interactions and a considerable degree of unfolding compared to native apo-myoglobin. The mechanism of acid-induced denaturation of hMb, therefore, appears to follow the sequence (heme protein)(native) {\textendash}> (heme-protein)(unfolded) {\textendash}> heme + (protein)(unfolded).},
	keywords = {APOMYOGLOBIN, HEME-PROTEINS, INTERMEDIATE, IONS, LOW PH, METMYOGLOBIN, PROBING CONFORMATIONAL-CHANGES, RESOLUTION, SPERM WHALE, STABILITY},
	isbn = {0006-2960},
	url = {<Go to ISI>://A1997XB32100022},
	author = {Konermann, L. and Rosell, F. I. and Mauk, A. G. 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 {4028,
	title = {Cytochrome c folding kinetics studied by time-resolved electrospray ionization mass spectrometry},
	journal = {Biochemistry},
	volume = {36},
	number = {18},
	year = {1997},
	note = {ISI Document Delivery No.: WY063Times Cited: 82Cited Reference Count: 46},
	month = {May},
	pages = {5554-5559},
	type = {Article},
	abstract = {A new method for studying the folding kinetics of proteins is described. The method combines a continuous flow mixing technique with an electrospray mass spectrometer. Different protein conformations in solution are detected by the different charge states they produce during electrospray ionization. Unfolded proteins generally have more accessible protonation sites and give higher charge states than native proteins. The method is applied to study the refolding of acid-denatured cytochrome c. Global data analysis is used to obtain the exponential lifetimes which are associated with the refolding process. The kinetics can be described by two lifetimes of 0.17 +/- 0.02 and 8.1 +/- 0.9 s which are in accordance with the results of stopped flow experiments previously described in the literature. These lifetimes are associated with roughly 90 and 10\% of the total intensity changes in the mass spectrum, respectively, and most likely reflect fast and slow refolding subpopulations of cytochrome c in solution.},
	keywords = {COMPLEX, denaturation, FERRICYTOCHROME-C, IRON BLEOMYCIN, LIGANDS, MECHANISM, PATHWAYS, PROBING CONFORMATIONAL-CHANGES, PROTEINS, SPECTRA},
	isbn = {0006-2960},
	url = {<Go to ISI>://A1997WY06300029},
	author = {Konermann, L. and Collings, B. A. and Douglas, D. J.}
}
