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Venkataraman S, Wooley KL. ATRP from an amino acid-based initiator: A facile approach for α-functionalized polymers. Macromolecules 2006; 39:9661-9664. [PMID: 19043615 DOI: 10.1021/ma0619583] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A L-valine-derived α-haloamide was synthesized and investigated as an initiator for the atom transfer radical polymerization of tert-butyl acrylate using commercially available CuBr, CuBr(2) and N,N,N',N",N"-pentamethyldiethylenetriamine as the catalyst and ligand system. Kinetic studies and extension to a diblock copolymer with styrene, each indicated that the polymerizations were well controlled. Poly(tert-butyl acrylate) having M(n) (NMR) = 8.6 kDa, M(n) (GPC) = 8.3 kDa, PDI = 1.11 and a diblock of poly(tert-butyl acrylate)-b-polystyrene having M(n) (NMR) = 20.2 kDa, M(n) (GPC) = 22.5 kDa, PDI = 1.22 were prepared by the sequential polymerization of tert-butyl acrylate and styrene at 55 °C and 90 °C, respectively.
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Affiliation(s)
- Shrinivas Venkataraman
- Center for Materials Innovation and Department of Chemistry, Washington University in Saint Louis, One Brookings Drive, Campus Box 1134, Saint Louis, MO 63130
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Mustafi D, Hofer JE, Huang W, Palzkill T, Makinen MW. Chromophoric spin-labeled beta-lactam antibiotics for ENDOR structural characterization of reaction intermediates of class A and class C beta-lactamases. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2004; 60:1279-1289. [PMID: 15134725 DOI: 10.1016/j.saa.2003.10.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Revised: 07/13/2003] [Accepted: 10/16/2003] [Indexed: 05/24/2023]
Abstract
The chromophoric spin-label substrate 6-N-[3-(2,2,5,5-tetramethyl-1-oxypyrrolin-3-yl)-propen-2-oyl]penicillanic acid (SLPPEN) was synthesized by acylation of 6-aminopenicillanic acid with the acid chloride of 3-(2,2,5,5-tetramethyl-1-oxypyrrolinyl)-2-propenoic acid and characterized by physical methods. By application of angle-selected electron nuclear double resonance (ENDOR), we have determined the molecular structure of SLPPEN in solution. SLPPEN exhibited UV absorption properties that allowed accurate monitoring of the kinetics of its enzyme-catalyzed hydrolysis. The maximum value of the (substrate-product) difference extinction coefficient was 2824 M(-1) cm(-1) at 275 nm compared to 670 M(-1) cm(-1) at 232 nm for SLPEN [J. Am. Chem. Soc. 117 (1995) 6739]. For SLPPEN, the steady-state kinetic parameters kcat and kcat/KM, determined under initial velocity conditions, were 637 +/- 36 s(-1) and 13.8 +/- 1.4 x 10(6) M(-1) s(-1), respectively, for hydrolysis catalyzed by TEM-1 beta-lactamase of E. coli, and 0.5 +/- 0.04 s(-1) and 3.9 +/- 0.4 x 10(4) M(-1) s(-1) for hydrolysis catalyzed by the beta-lactamase of Enterobacter cloacae P99. We have also observed "burst kinetics" for the hydrolysis of SLPPEN with P99 beta-lactamase, indicative of formation of an acylenzyme reaction intermediate. In DMSO:H2O (30:70, v:v) cryosolvent mixtures buffered to pH* 7.0, the half-life of the acylenzyme intermediate formed with the P99 enzyme at -5 degrees C was > or = 3 min, suitable for optical characterization. The observation of burst kinetics in the hydrolysis of SLPPEN catalyzed by P99 beta-lactamase suggests that this chromophoric spin-labeled substrate is differentially sensitive to active site interactions underlying the cephalosporinase and penicillinase reactivity of this class C enzyme.
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Affiliation(s)
- Devkumar Mustafi
- Department of Biochemistry and Molecular Biology, Cummings Life Science Center, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
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Mustafi D, Sosa-Peinado A, Gupta V, Gordon DJ, Makinen MW. Structure of spin-labeled methylmethanethiolsulfonate in solution and bound to TEM-1 beta-lactamase determined by electron nuclear double resonance spectroscopy. Biochemistry 2002; 41:797-808. [PMID: 11790101 DOI: 10.1021/bi010539p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Site-directed spin-labeling of proteins whereby the spin-label methyl 3-(2,2,5,5-tetramethyl-1-oxypyrrolinyl)methanethiolsulfonate (SLMTS) is reacted with the -SH groups of cysteinyl residues incorporated into a protein by mutagenesis has been successfully applied to investigate secondary structure and conformational transitions of proteins. In these studies, it is expected that the spin-label moiety adopts different conformations dependent on its local environment. To determine the conformation of SLMTS in solution reacted with L-cysteine (SLMTCys) and bound in the active site of the Glu240Cys mutant of TEM-1 beta-lactamase, we have synthesized SLMTS both of natural abundance isotope composition and in site-specifically deuterated forms for electron nuclear double resonance (ENDOR) studies. ENDOR-determined electron-proton distances from the unpaired electron of the nitroxyl group of the spin-label to the methylene and methyl protons of SLMTS showed three conformations of the oxypyrrolinyl ring with respect to rotation around the S-S bond dependent on the solvent dielectric constant. For SLMTCys, two conformations of the molecule were compatible with the ENDOR-determined electron-nucleus distances to the side-chain methylene protons and to H(alpha) and H(beta1,2) of cysteine. To determine SLMTS conformation reacted with the Glu240Cys mutant of TEM-1 beta-lactamase, enzyme was overexpressed in both ordinary and perdeuterated minimal medium. Resonance features of H(alpha) and H(beta1,2) of the Cys240 residue of the mutant and of the side-chain methylene protons within the spin-label moiety yielded electron-proton distances that sterically accommodated the two conformations of free SLMTCys in solution.
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Affiliation(s)
- Devkumar Mustafi
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, USA.
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Van Zele CJ, Cunningham MA, Makinen MW. Validation of nitroxyl spin-label force-field parameters through molecular dynamics simulations. J Comput Chem 2001. [DOI: 10.1002/jcc.1071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Mustafi D, Sosa-Peinado A, Makinen MW. ENDOR structural characterization of a catalytically competent acylenzyme reaction intermediate of wild-type TEM-1 beta-lactamase confirms glutamate-166 as the base catalyst. Biochemistry 2001; 40:2397-409. [PMID: 11327860 DOI: 10.1021/bi0021075] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The catalytically competent active-site structure of a true acylenzyme reaction intermediate of TEM-1 beta-lactamase formed with the kinetically specific spin-labeled substrate 6-N-(2,2,5,5-tetramethyl-1-oxypyrrolinyl-3-carboxyl)-penicillanic acid isolated under cryoenzymologic conditions has been determined by angle-selected electron nuclear double resonance (ENDOR) spectroscopy. Cryoenzymologic experiments with use of the chromophoric substrate 6-N-[3-(2-furanyl)-propen-2-oyl]-penicillanic acid showed that the acylenzyme reaction intermediate could be stabilized in the -35 to -75 degrees C range with a half-life suitably long to allow freeze-quenching of the reaction species for ENDOR studies while a noncovalent Michaelis complex could be optically identified at temperatures only below -70 degrees C. The wild-type, Glu166Asn, Glu240Cys, and Met272Cys mutant forms of the mature enzyme were overexpressed in perdeuterated minimal medium to allow detection and assignment of proton resonances specific for the substrate and chemically modified amino acid residues in the active site. From analysis of the dependence of the ENDOR spectra on the setting of the static laboratory magnetic field H0, the dipolar contributions to the principal hyperfine coupling components were estimated to calculate the separations between the unpaired electron of the nitroxyl group and isotopically identified nuclei. These electron-nucleus distances were applied as constraints to assign the conformation of the substrate in the active site and of amino acid side chains by molecular modeling. Of special interest was that the ENDOR spectra revealed a water molecule sequestered in the active site of the acylenzyme of the wild-type protein that was not detected in the deacylation impaired Glu166Asn mutant. On the basis of the X-ray structure of the enzyme, the ENDOR distance constraints placed this water molecule within hydrogen-bonding distance to the carboxylate side chain of glutamate-166 as if it were poised for nucleophilic attack of the scissile ester bond. The ENDOR results provide experimental evidence of glutamate-166 in its functional role as the general base catalyst in the wild-type enzyme for hydrolytic breakdown of the acylenzyme reaction intermediate of TEM-1 beta-lactamase.
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Affiliation(s)
- D Mustafi
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, USA
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Makinen MW. Electron nuclear double resonance determined structures of enzyme reaction intermediates: structural evidence for substrate destabilization. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 1998; 54A:2269-2281. [PMID: 9974225 DOI: 10.1016/s1386-1425(98)00210-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Angle selective ENDOR of nitroxyl spin-labels is briefly reviewed to illustrate the methodology of structure analysis developed in our laboratory for characterizing catalytically competent intermediates of enzyme catalyzed reactions. ENDOR structure determination of a reaction intermediate of alpha-chymotrypsin formed with a kinetically specific spin-labeled substrate and of an enzyme-inhibitor complex formed with a spin-labeled transition-state inhibitor analog is briefly described. Both spin-labeled molecules bound in the active site of the enzyme are found in torsionally distorted conformations. It is suggested that this torsionally distorted state in which the bound ligand is of higher potential energy than in the ground state conformation reflects substrate destabilization in the course of the enzyme catalyzed reaction.
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Affiliation(s)
- M W Makinen
- Department of Biochemistry and Molecular Biology, University of Chicago, IL 60637, USA.
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Jiang F, Tsai SW, Chen S, Makinen MW. ENDOR Determined Structure of a Complex of α-Chymotrypsin with a Spin-Labeled Transition-State Inhibitor Analogue. J Phys Chem B 1998. [DOI: 10.1021/jp972742t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fashun Jiang
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 E. 58th Street, Chicago, Illinois 60637
| | - Shih-Wa Tsai
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 E. 58th Street, Chicago, Illinois 60637
| | - Shan Chen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 E. 58th Street, Chicago, Illinois 60637
| | - Marvin W. Makinen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 E. 58th Street, Chicago, Illinois 60637
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Mustafi D, Knock MM, Shaw RW, Makinen MW. Conformational Changes in Spin-Labeled Cephalosporin and Penicillin upon Hydrolysis Revealed by Electron Nuclear Double Resonance Spectroscopy. J Am Chem Soc 1997. [DOI: 10.1021/ja971717y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Devkumar Mustafi
- Contribution from the Department and Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, and Department of Chemistry and Biochemistry, Box 41061, Texas Tech University, Lubbock, Texas 79409
| | - Mona M. Knock
- Contribution from the Department and Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, and Department of Chemistry and Biochemistry, Box 41061, Texas Tech University, Lubbock, Texas 79409
| | - Robert W. Shaw
- Contribution from the Department and Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, and Department of Chemistry and Biochemistry, Box 41061, Texas Tech University, Lubbock, Texas 79409
| | - Marvin W. Makinen
- Contribution from the Department and Biochemistry and Molecular Biology, The University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, Illinois 60637, and Department of Chemistry and Biochemistry, Box 41061, Texas Tech University, Lubbock, Texas 79409
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Ballinger MD, Frey PA, Reed GH, LoBrutto R. Pulsed electron paramagnetic resonance studies of the lysine 2,3-aminomutase substrate radical: evidence for participation of pyridoxal 5'-phosphate in a radical rearrangement. Biochemistry 1995; 34:10086-93. [PMID: 7632680 DOI: 10.1021/bi00031a033] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The role of pyridoxal 5'-phosphate (PLP) in the radical-mediated amino group migration catalyzed by lysine 2,3-aminomutase from Clostridia SB4 has been investigated by electron spin echo envelope modulation (ESEEM) spectroscopy. This pulsed electron paramagnetic resonance (EPR) method was used to estimate the distance between the unpaired electron in the alpha-radical of beta-lysine, a steady-state intermediate in the reaction, and deuterium at the C4' position of the cofactor, PLP. [4'-2H]PLP was synthesized and exchanged into the enzyme. The steady-state radical was generated in the labeled samples and in samples with unlabeled PLP by addition of L-lysine.H2SO4 to activated enzyme. ESEEM spectra of the samples prepared with [4'-2H]PLP exhibited distinctive low-frequency modulations that were not present in spectra of matched samples with unlabeled PLP. Fourier transformation of the modulations yielded a prominent doublet signal centered about the Larmor frequency of deuterium. The magnitude of the doublet splitting of the 2H ESEEM signal exhibited angle selection across the CW EPR powder pattern. The observed angle selection, as well as simulation of the time domain spectra, indicated that the doublet splitting was due to the combined effects of the 2H hyperfine and nuclear quadrupole interactions. The influences of the quadrupole interaction and of isotropic and dipolar hyperfine interactions were explored by simulations of the ESEEM spectra. The analysis indicates a distance of < 3.5 A between the 2H at C4' of PLP and the radical center at C alpha lysine. The data are most compatible with an aldimine linkage between PLP and the beta-nitrogen of beta-lysine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M D Ballinger
- Institute for Enzyme Research, Graduate School, Life Sciences, University of Wisconsin-Madison 53705, USA
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Wells G, Mustafi D, Makinen M. Structure at the active site of an acylenzyme of alpha-chymotrypsin and implications for the catalytic mechanism. An electron nuclear double resonance study. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41816-3] [Citation(s) in RCA: 4] [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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Mustafi D, Makinen M. Catalytic conformation of carboxypeptidase A. Structure of a true enzyme reaction intermediate determined by electron nuclear double resonance. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41817-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Mino H, Satoh JI, Kawamori A, Toriyama K, Zimmermann JL. Matrix ENDOR of tyrosine D+ in oriented Photosystem II membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90130-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Larsen RG, Singel DJ. Double electron–electron resonance spin–echo modulation: Spectroscopic measurement of electron spin pair separations in orientationally disordered solids. J Chem Phys 1993. [DOI: 10.1063/1.464916] [Citation(s) in RCA: 204] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Metalloenzyme Active-Site Structure and Function through Multifrequency CW and Pulsed ENDOR. EMR OF PARAMAGNETIC MOLECULES 1993. [DOI: 10.1007/978-1-4615-2892-0_4] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Boisvert WE, Mustafi D, Kasa S, Makinen MW, Halpern HJ, Yu C, Barth E, Peric M. Kinetically specific spin-label substrates of liver alcohol dehydrogenase and of liver aldehyde dehydrogenase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1993; 328:501-12. [PMID: 8388157 DOI: 10.1007/978-1-4615-2904-0_53] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- W E Boisvert
- Department of Biochemistry and Molecular Biology, University of Chicago, Illinois 60637
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