@article {2575,
	title = {An electropneumatic-heated nebulizer for enhancing spray ionization in PhotoSpray atmospheric pressure photoionization sources for liquid chromatography/mass spectrometry},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {23},
	number = {21},
	year = {2009},
	note = {ISI Document Delivery No.: 514YATimes Cited: 1Cited Reference Count: 30Robb, Damon B. Blades, Michael W.},
	month = {Nov},
	pages = {3394-3400},
	type = {Article},
	abstract = {We introduce a novel electropneumatic-heated nebulizer (EPn-HN), incorporating an electrified internal pneumatic nebulizer, to enhance the yield of sprayed ions from PhotoSpray (TM) atmospheric pressure photoionization (APPI) sources for liquid chromatography/mass spectrometry (LC/MS). Spray ionization from the pneumatic-heated nebulizers used in APPI sources provides a supplemental, complementary ionization method to be used for involatile and thermally labile compounds, otherwise intractable to APPI. Details of the construction and operation of the EPn-HN device are provided. The performance of the EPn-HN is demonstrated using two model compounds: substance P, a peptide used as a standard in studies of ion fragmentation mechanisms, and aztreonam, a thermally labile antibiotic. At the optimum voltage for spray ionization, improvements in sensitivity of two orders of magnitude are obtained relative to when the sprayer is grounded, the conventional case. Since both substance P and aztreonam cannot be detected using the APPI method alone, the results demonstrate how spray ionization from the EPn-HN may be used to extend the range of compounds amenable to PhotoSpray sources. Copyright (C) 2009 John Wiley \& Sons, Ltd.},
	keywords = {CHEMICAL-IONIZATION, ELECTROSPRAY, PEPTIDES, RESIDUES, TANDEM MASS-SPECTROMETRY},
	isbn = {0951-4198},
	url = {<Go to ISI>://000271431500006},
	author = {Robb, D. B. and Blades, M. W.}
}
@article {454,
	title = {Dehydroalanine-based inhibition of a peptide epimerase from spider venom},
	journal = {Journal of Organic Chemistry},
	volume = {67},
	number = {24},
	year = {2002},
	note = {ISI Document Delivery No.: 620AATimes Cited: 17Cited Reference Count: 42},
	month = {Nov},
	pages = {8389-8394},
	type = {Article},
	abstract = {Ribosomally produced peptides that contain D-amino acids have been isolated from a number of vertebrate and invertebrate sources. In each case, the D-amino acids are introduced by a posttranslational modification of a parent peptide containing only amino acids of the L-configuration. The only known enzyme to catalyze such a reaction is the peptide epimerase (also known as peptide isomerase) from the venom of the funnel web spider, Agelenopsis aperta. This enzyme interconverts two 48-amino-acid-long peptide toxins that differ only by the stereochemistry at a single serine residue. In this paper we report the synthesis and testing of two pentapeptide analogues that contain modified amino acids at the site normally occupied by the substrate serine residue. When the L-chloroalanine-containing peptide 3 was incubated with the epimerase it was converted into the dehydroalanine-containing peptide 4 via an elimination of HCl. The dehydroalanine peptide 4 was independently synthesized and found to act as a potent inhibitor of the epimerase (IC50 = 0.5 muM). These results support a direct deprotonation/reprotonation mechanism in which a carbanionic intermediate is formed. The observed inhibition by 4 can be attributed to the sp(2)-hybridization of the a-carbon in the dehydroalanine unit that mimics the planar geometry of the anionic intermediate.},
	keywords = {ACID, ACTIVE-SITE, ENZYME, GLUTAMATE RACEMASE, GRAMICIDIN-S SYNTHETASE, INFLUENZAE DIAMINOPIMELATE EPIMERASE, INITIATION MODULE PHEATE, MECHANISM, PROLINE RACEMASE, RESIDUES},
	isbn = {0022-3263},
	url = {<Go to ISI>://000179509400011},
	author = {Murkin, A. S. and Tanner, M. E.}
}
@article {520,
	title = {Understanding nature{\textquoteright}s strategies for enzyme-catalyzed racemization and epimerization},
	journal = {Accounts of Chemical Research},
	volume = {35},
	number = {4},
	year = {2002},
	note = {ISI Document Delivery No.: 544TBTimes Cited: 65Cited Reference Count: 36},
	month = {Apr},
	pages = {237-246},
	type = {Review},
	abstract = {Epimerases and racemases are enzymes that catalyze the inversion of stereochemistry in biological molecules. In this article, three distinct examples are used to illustrate the wide range of chemical strategies employed during catalysis, and the diverse set of ancestors from which these enzymes have evolved. Glutamate racemase is an example of an enzyme that operates at an "activated" stereocenter (bearing a relatively acidic proton) and employs a nonstereospecific deprotonation/reprotonation mechanism. UDP-N-Acetylglucosamine 2-epimerase acts at an "unactivated" stereocenter and uses a mechanism involving a nonstereospecific elimination/addition of UDP. L-Ribulose phosphate 4-epimerase also acts at an unactivated stereocenter and uses a nonstereospecific retroaldol/aldol mechanism.},
	keywords = {ALDOLASE, CLASS-II, ESCHERICHIA-COLI, GLUTAMATE RACEMASE, IDENTIFICATION, L-FUCULOSE-1-PHOSPHATE, L-RIBULOSE-5-PHOSPHATE 4-EPIMERASE, MECHANISM, N-ACETYLGLUCOSAMINE 2-EPIMERASE, PHOSPHATE, RESIDUES},
	isbn = {0001-4842},
	url = {<Go to ISI>://000175175800005},
	author = {Tanner, M. E.}
}
@article {4689,
	title = {Undercarboxylation of recombinant prothrombin revealed by analysis of gamma-carboxyglutamic acid using capillary electrophoresis and laser-induced fluorescence},
	journal = {Febs Letters},
	volume = {445},
	number = {2-3},
	year = {1999},
	note = {ISI Document Delivery No.: 175YCTimes Cited: 6Cited Reference Count: 37},
	month = {Feb},
	pages = {256-260},
	type = {Article},
	abstract = {The gamma-carboxyglutamic acid (Gla) content of several variants of human prothrombin has been measured by using capillary electrophoresis and laser-induced fluorescence (CE-LIF). Both plasma-derived prothrombin and recombinant prothrombin contain ten residues of Gla per molecule of protein. In contrast, a variant of human prothrombin (containing the second kringle domain of bovine prothrombin) was separated into two populations that differed in their Gla content. Direct measurement of the Gla content showed an association with the presence or absence of the calcium-dependent conformational change that is required for prothombinase function. Thus, the CE-LIF assay is useful in determining the carboxylation status of recombinant proteins. (C) 1999 Federation of European Biochemical Societies.},
	keywords = {baby hamster kidney, calcium, capillary electrophoresis, cell, EXPRESSION, FACTOR-X, gamma carboxy glutamic acid, GLUTAMIC-ACID, HUMAN PROTEIN-C, LASER-INDUCED FLUORESCENCE, METAL, PHOSPHOLIPID-BINDING-PROPERTIES, PROTHROMBIN, PURIFICATION, recombinant protein, RESIDUES, VITAMIN-K},
	isbn = {0014-5793},
	url = {<Go to ISI>://000079122800007},
	author = {Vo, H. C. and Britz-McKibbin, P. and Chen, D. D. Y. and MacGillivray, R. T. A.}
}
@article {4020,
	title = {Complete measurement of the pK(a) values of the carboxyl and imidazole groups in Bacillus circulans xylanase},
	journal = {Protein Science},
	volume = {6},
	number = {12},
	year = {1997},
	note = {ISI Document Delivery No.: YK912Times Cited: 44Cited Reference Count: 29},
	month = {Dec},
	pages = {2667-2670},
	type = {Article},
	abstract = {Electrostatic interactions in proteins can be dissected experimentally by determining the pK(a), values of their constituent ionizable amino acids. To complement previous studies of the glutamic acid and histidine residues in Bacillus circulans xylanase (BCX), we have used NMR methods to measure the pK(a)s of the seven aspartic acids and the C-terminus of this protein. The pK(a)s of these carboxyls are all less than the corresponding values observed with random coil polypeptides, indicating that their ionization contributes favorably to the stability of the folded enzyme. In general, the aspartic acids with the most reduced pK(a)s are those with limited exposure to the solvent and a high degree of conservation among homologous xylanases. Most dramatically, Asp 53 and Asp 101 have pK(a)s < 2 and thus remain deprotonated in native BCX under all conditions examined. Asp 83 is completely buried, forming a strong salt bridge with Arg 136. In contrast, Asp 101 is located on the surface of the protein, stabilized in the deprotonated form by an extensive network of hydrogen bonds involving an internal water molecule and the neutral side-chain and main-chain atoms of Ser 100 and Thr 145. These data provide a complete experimental database for theoretical studies of the ionization behavior of BCX under acidic conditions.},
	keywords = {aspartic acid, electrostatics, FAMILIES, NMR, NMR ASSIGNMENTS, NUCLEAR-MAGNETIC-RESONANCE, PK(A), PROTEINS, RESIDUES, SHIFTS, titration, XYLANASE},
	isbn = {0961-8368},
	url = {<Go to ISI>://A1997YK91200024},
	author = {Joshi, M. D. and Hedberg, A. and McIntosh, L. P.}
}
