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Detection and elimination profile of cathinone in equine after norephedrine (Propalin®) administration using a validated liquid chromatography–tandem mass spectrometry method. Anal Bioanal Chem 2013; 405:9711-22. [DOI: 10.1007/s00216-013-7073-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/04/2013] [Accepted: 05/16/2013] [Indexed: 12/01/2022]
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Sinhababu AK, Borchardt RT. Silica gel-assisted reduction of nitrostyrenes to 2-aryl-2-[2H]-1-nitroethanes with sodium borodeuteride. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.2580200814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
The wide media coverage given recently to a study correlating higher selenium levels with a reduced risk of advanced prostate cancer is but the latest addition to a growing body of epidemiological findings which link dietary selenium deficiency to diseases as diverse as cancer, heart disease, arthritis and AIDS. Indeed, selenium has a long history of association with human health and disease. Moreover, direct evidence is now emerging for specific beneficial effects of dietary selenium supplementation. Thus, the pharmacology, biology and biochemistry of selenium metabolism have become subjects of intense current interest. At the molecular level, selenium (as selenocysteine) is an essential component of the active sites of the enzymes glutathione peroxidase, iodothyronine 5'-deiodinase and mammalian thioredoxin reductase, and is also present in several other mammalian selenoproteins. Both glutathione peroxidase and thioredoxin reductase catalyse reactions essential to the protection of cellular components against oxidative and free radical damage. As a consequence of the growing recognition of the important biological role of selenium, a number of novel pharmaceutical agents, either selenium-based or which target specific aspects of selenium metabolism, are under development. Among these are orally active selenium-based antihypertensive agents, anticancer, antiviral, immunosuppressive and antimicrobial agents, and organoselenium compounds which reduce oxidative tissue damage and oedema. It can be anticipated that as our understanding of the basic biology and biochemistry of selenium increases, future efforts will uncover even more sophisticated approaches for the rational development of new selenium-based pharmaceutical agents.
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Affiliation(s)
- S W May
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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Mounier CE, Shi J, Sirimanne SR, Chen BH, Moore AB, Gill-Woznichak MM, Ping D, May SW. Pyruvate-extended amino acid derivatives as highly potent inhibitors of carboxyl-terminal peptide amidation. J Biol Chem 1997; 272:5016-23. [PMID: 9030564 DOI: 10.1074/jbc.272.8.5016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Carboxyl-terminal amidation, a required post-translational modification for the bioactivation of many neuropeptides, entails sequential enzymatic action by peptidylglycine monooxygenase (PAM, EC 1.14.17.3) and peptidylamidoglycolate lyase (PGL, EC 4.3.2.5). The monooxygenase, PAM, first catalyzes conversion of a glycine-extended pro-peptide to the corresponding alpha-hydroxyglycine derivative, and the lyase, PGL, then catalyzes breakdown of this alpha-hydroxyglycine derivative to the amidated peptide plus glyoxylate. We now introduce the first potent inhibitors for peptidylamidoglycolate lyase. These inhibitors, which can be viewed as pyruvate-extended N-acetyl amino acids, constitute a novel class of compounds. They were designed to resemble likely transient species along the reaction pathway of PGL catalysis. A general synthetic procedure for preparation of pyruvate-extended N-acetyl amino acids or peptides is described. Since these compounds possess the 2,4-dioxo-carboxylate moiety, their solution tautomerization was investigated using both NMR and high performance liquid chromatography analyses. The results establish that freshly prepared solutions of N-Ac-Phe-pyruvate consist predominantly of the enol tautomer, which then slowly tautomerizes to the diketo form when left standing for several days in an aqueous medium; upon acidification, formation of the hydrate tautomer occurs. Kinetic experiments established that these novel compounds are highly potent, pure competitive inhibitors of PGL. Kinetic experiments with the ascorbate-dependent copper monooxygenases, PAM and dopamine-beta-monooxygenase, established that these compounds also bind competitively with respect to ascorbate; however, pyruvate-extended N-acyl-amino acid derivatives possessing hydrophobic side chains are much more potent inhibitors of PGL than of PAM. Selective targeting of N-Ac-Phe-pyruvate so as to inhibit the lyase, but not the monooxygenase, domain was demonstrated with the bifunctional amidating enzyme of Xenopus laevis. The availability of potent inhibitors of PGL should facilitate studies regarding the possible biological role of alpha-hydroxyglycine-extended peptides.
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Affiliation(s)
- C E Mounier
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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Kolhekar AS, Mains RE, Eipper BA. Peptidylglycine alpha-amidating monooxygenase: an ascorbate-requiring enzyme. Methods Enzymol 1997; 279:35-43. [PMID: 9211255 DOI: 10.1016/s0076-6879(97)79007-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- A S Kolhekar
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Debnath J, Husain PA, May SW. Activation of an adrenergic pro-drug through sequential stereoselective action of tandem target enzymes. Biochem Biophys Res Commun 1992; 189:33-9. [PMID: 1449487 DOI: 10.1016/0006-291x(92)91521-q] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The synthetic amino acid, 3,4-dihydroxyphenylserine (DOPS) has been of great interest for many years as an adrenergic pro-drug, since the L-threo diastereomer of DOPS can be a precursor of R-(-)-norepinephrine, the natural form of this neurotransmitter. We now report bioactivation of DOPS to the potent pharmacological agent, noradrenalone (arterenone), via sequential stereoselective action by two target enzymes--dopamine beta-monooxygenase (DBM) and L-aromatic amino acid decarboxylase (AADC)--acting in tandem. Enzymatic activation is stereospecific, with only the L-erythro DOPS diastereomer producing noradrenalone; this is consistent with the known stereospecificities of AADC and DBM. These results provide a heretofore unrecognized rationale for the bioactivity of L-erythro DOPS and provide a basis for the design of new adrenergic pro-drugs.
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Affiliation(s)
- J Debnath
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta 30332
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Abstract
Studies with biomimetic models can yield considerable insight into mechanisms of enzymatic catalysis. The discussion above indicates how such information has been important in the cases of flavoproteins, hemoproteins, and, to a lesser extent, the copper protein dopamine beta-hydroxylase. Some of the moieties that we generally accept as intermediates (i.e., high-valent iron oxygen complex in cytochrome P-450 reactions) would be extremely hard to characterize were it not for biomimetic models and more stable analogs such as peroxidase Compound I complexes. Although biomimetic models can be useful, we do need to keep them in perspective. It is possible to alter ligands and aspects of the environment in a way that may not reflect the active site of the protein. Eventually, the model work needs to be carried back to the proteins. We have seen that diagnostic substrates can be of considerable use in understanding enzymes and examples of elucidation of mechanisms through the use of rearrangements, mechanism-based inactivation, isotope labeling, kinetic isotope effects, and free energy relationships have been given. The point should be made that a myriad of approaches need to be applied to the study of each enzyme, for there is potential for misleading information if total reliance is placed on a single approach. The point also needs to be made that in the future we need information concerning the structures of the active sites of enzymes in order to fully understand them. Of the enzymes considered here, only a bacterial form of cytochrome P-450 (P-450cam) has been crystallized. The challenge to determine the three-dimensional structures of these enzymes, particularly the intrinsic membrane proteins, is formidable, yet our further understanding of the mechanisms of enzyme catalysis will remain elusive as long as we have to speak of putative specific residues, domains, and distances in anecdotal terms. The point should be made that there is actually some commonality among many of the catalytic mechanisms of oxidation, even among proteins with different structures and prosthetic groups. Thus, we see that cytochrome P-450 has some elements of a peroxidase and vice versa; indeed, the chemistry at the prosthetic group is probably very similar and the overall chemistry seems to be induced by the protein structure. The copper protein dopamine beta-hydroxylase appears to proceed with chemistry similar to that of the hemoprotein cytochrome P-450 and, although not so thoroughly studied, the non-heme iron protein P. oleovarans omega-hydroxylase.(ABSTRACT TRUNCATED AT 400 WORDS)
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Phillips RS, Fletcher JG, Von Tersch RL, Kirk KL. Oxygenation of fluorinated tyrosines by mushroom tyrosinase releases fluoride ion. Arch Biochem Biophys 1990; 276:65-9. [PMID: 2105082 DOI: 10.1016/0003-9861(90)90010-v] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The reactions of 2-fluoro- and 3-fluoro-L-tyrosine with mushroom tyrosinase have been investigated. Both fluorinated tyrosines are good substrates for tyrosinase, with Vmax and Vmax/Km values similar to those for L-tyrosine. Oxygenation of 2-fluorotyrosine is regioselective, and only 6-fluorodopa was detected by HPLC in reaction mixtures. Oxygenation of both isomers of monofluorotyrosine results in fluoride ion production in the absence of ascorbic acid; however, 2-fluorotyrosine also produces fluoride in the presence of ascorbic acid. These results are consistent with previous studies demonstrating rapid intramolecular cyclization of nascent 6-fluorodopaquinone (M.E. Rice, B. Moghaddan, C.R. Creveling, and K.L. Kirk, 1987, Anal. Chem. 59, 1534-1538), which is competitive with reduction by ascorbate, resulting in elimination of the aromatic fluorine as fluoride ion.
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Affiliation(s)
- R S Phillips
- Department of Chemistry, School of Chemical Sciences, University of Georgia, Athens 30602
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Herman HH, Wimalasena K, Fowler LC, Beard CA, May SW. Demonstration of the ascorbate dependence of membrane-bound dopamine beta-monooxygenase in adrenal chromaffin granule ghosts. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)35404-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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May SW, Herman HH, Roberts SF, Ciccarello MC. Ascorbate depletion as a consequence of product recycling during dopamine beta-monooxygenase catalyzed selenoxidation. Biochemistry 1987; 26:1626-33. [PMID: 3036204 DOI: 10.1021/bi00380a021] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The competence of dopamine beta-monooxygenase (DBM) to process selenide substrates was investigated, in anticipation that the expected selenoxide products would exhibit unique reactivity and redox properties. The prototypical selenide phenyl 2-aminoethyl selenide (PAESe) was synthesized and shown to be a substrate for DBM with the characteristic e/O2 ratio of 2:1 for monooxygenation. The kinetic parameters for oxygenation of PAESe were found to be similar to those for the DBM-catalyzed sulfoxidation of the cognate sulfide phenyl 2-aminoethyl sulfide [May, S. W., & Phillips, R. S. (1980) J. Am. Chem. Soc. 102, 5981-5983], and selenoxidation was stimulated by fumarate in a manner similar to other well-characterized DBM monooxygenation reactions. Identification of phenyl 2-aminoethyl selenoxide (PAESeO) as the enzymatic product was accomplished by the demonstration of coincident elution of authentic PAESeO with the enzymatic product in three significantly different HPLC systems. PAESeO was found to oxidize ascorbic acid with the concomitant and stoichiometric reduction of PAESeO back to the selenide, PAESe. As a consequence of this nonenzymatic reaction, ascorbate-supported DBM turnover was prematurely terminated under standard assay conditions due to depletion of reduced ascorbate. The kinetics of the redox reaction between PAESeO and ascorbate were investigated with a spectrophotometric assay of ascorbate at 300 nm, and a second-order rate constant of 3.4 M-1 s-1 was determined at pH 5.0, 25 degrees C. Spectrophotometric assay of cytochrome c (cyt c) reduction at 550 nm during the oxidation of ascorbate by PAESeO demonstrated that no cyt c trappable semidehydroascorbate was produced in this nonenzymatic reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
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May SW, Katopodis AG. Oxygenation of alcohol and sulphide substrates by a prototypical non-haem iron monooxygenase: catalysis and biotechnological potential. Enzyme Microb Technol 1986. [DOI: 10.1016/0141-0229(86)90004-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Padgette SR, Wimalasena K, Herman HH, Sirimanne SR, May SW. Olefin oxygenation and N-dealkylation by dopamine beta-monooxygenase: catalysis and mechanism-based inhibition. Biochemistry 1985; 24:5826-39. [PMID: 4084493 DOI: 10.1021/bi00342a021] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In an initial communication [May, S. W., Mueller, P. W., Padgette, S. R., Herman, H. H., & Phillips, R. S. (1983) Biochem. Biophys. Res. Commun. 110, 161-168], we reported that 1-phenyl-1-(aminomethyl)ethene hydrochloride (PAME) is an olefinic substrate for dopamine beta-monooxygenase (DBM; EC 1.14.17.1) which inactivates the enzyme in an apparent mechanism-based manner. The present study further characterizes this reaction. The inactivation reaction yields kinact = 0.23 min-1 at pH 5.0 and 37 degrees C and is strictly dependent on reductant (ascorbate) and oxygen. The DBM/PAME substrate reaction (apparent kcat = 14 s-1), shown to be stimulated by fumarate, gives the corresponding epoxide as product, identified by derivatization with 4-(p-nitrobenzyl)pyridine. However, the lack of DBM inhibition by alpha-methylstyrene oxide, and the observation of identical PAME/DBM inactivation rates in the absence and presence of preformed enzymatic PAME epoxide, indicates that free epoxide is not the inactivating species. A structure-activity study revealed that 4-hydroxylation of PAME (to give 4-HOPAME) increases both kinact (0.81 min-1) and apparent kcat (56 s-1) values, while 3-hydroxylation (to give 3-HOPAME) greatly diminishes inactivation activity while retaining substrate activity (apparent kcat = 47 s-1). 4-Hydroxy-alpha-methylstyrene was found to be a DBM inhibitor (kinact = 0.53 min-1) with weak substrate activity (apparent kcat = 0.71 s-1), while 3-hydroxy-alpha-methylstyrene and alpha-(cyanomethyl) styrene were found not to exhibit detectable DBM substrate activity and only weak inhibitory activity. 3-Phenylpropargylamine hydrochloride showed no detectable DBM substrate activity but rapidly inactivated the enzyme. A new substrate activity for DBM was discovered, N-dealkylation of N-phenylethylenediamine and N-methyl-N-phenylethylenediamine, and the lack of O-dealkylation activity with phenyl 2-aminoethyl ether and 4-hydroxyphenyl 2-aminoethyl ether indicates that DBM N-dealkylation proceeds via initial one-electron abstraction from the benzylic nitrogen heteroatom. With this new substrate and inhibitor reactivity information in hand, along with the other known substrate reactions, a DBM oxygenation mechanism analogous to that for cytochrome P-450 is proposed.
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Ash DE, Papadopoulos NJ, Colombo G, Villafranca JJ. Kinetic and spectroscopic studies of the interaction of copper with dopamine beta-hydroxylase. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43105-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Colombo G, Rajashekhar B, Giedroc DP, Villafranca JJ. Alternate substrates of dopamine beta-hydroxylase. I. Kinetic investigations of benzyl cyanides as substrates and inhibitors. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43450-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Colombo G, Giedroc DP, Rajashekhar B, Villafranca JJ. Alternate substrates of dopamine beta-hydroxylase. II. Inhibition by benzyl cyanides and reactivation of inhibited enzyme. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43451-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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May SW, Padgette SR. Oxidoreductase Enzymes in Biotechnology: Current Status and Future Potential. Nat Biotechnol 1983. [DOI: 10.1038/nbt1083-677] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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May SW, Mueller PW, Padgette SR, Herman HH, Phillips RS. Dopamine-B-hydroxylase: suicide inhibition by the novel olefinic substrate, 1-phenyl-1-aminomethylethene. Biochem Biophys Res Commun 1983; 110:161-8. [PMID: 6860408 DOI: 10.1016/0006-291x(83)91274-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Dopamine-B-hydroxylase [E.C.1.14.17.1] plays a key role in the biosynthetic interconversion of neurotransmitters. It is now demonstrated for the first time that dopamine-B-hydroxylase also catalyzes the oxygenation of an olefinic substrate, 1-phenyl-1-aminomethylethene, producing 2,3-dihydroxy-2-phenylpropylamine after acid workup. This reaction gives the normal oxygenase stoichiometry of electrons to O2 to product of 2:1:1, and is kinetically comparable to other oxygenase activities of dopamine-B-hydroxylase, with a kcat value of 10 sec-1 and a KM of 8.3 mM. 1-Phenyl-1-aminomethylethene is also a time-dependent, first-order inactivator of dopamine-B-hydroxylase. The inactivation process exhibits the characteristics of mechanism-based, irreversible inactivation, giving a KI value of 13 mM and a kinac of 0.04 min-1. The central role of dopamine-B-hydroxylase in catecholamine metabolism suggests possible pharmacological uses for olefinic inhibitors of this enzyme.
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Holme E, Linstedt S, Nordin I. Uncoupling in the gamma-butyrobetaine hydroxylase reaction by D- and L-carnitine. Biochem Biophys Res Commun 1982; 107:518-24. [PMID: 7126226 DOI: 10.1016/0006-291x(82)91522-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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May SW, Phillips RS, Herman HH, Mueller PW. Bioactivation of Catha edulis alkaloids: enzymatic ketonization of norpseudoephedrine. Biochem Biophys Res Commun 1982; 104:38-44. [PMID: 7073680 DOI: 10.1016/0006-291x(82)91937-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Klinman JP, Krueger M. Dopamine beta-hydroxylase: activity and inhibition in the presence of beta-substituted phenethylamines. Biochemistry 1982; 21:67-75. [PMID: 7059582 DOI: 10.1021/bi00530a013] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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May S, Phillips R, Mueller P, Herman H. Dopamine beta-hydroxylase. Comparative specificities and mechanisms of the oxygenation reactions. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68867-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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