1
|
Broder BA, Bhuiyan M, Freifelder R, Rotsch DA, Chitneni SK, Makinen MW, Chen CT. Efficient Synthesis and HPLC-Based Characterization for Developing Vanadium-48-Labeled Vanadyl Acetylacetonate as a Novel Cancer Radiotracer for PET Imaging. Molecules 2024; 29:799. [PMID: 38398551 PMCID: PMC10892645 DOI: 10.3390/molecules29040799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 01/21/2024] [Accepted: 02/02/2024] [Indexed: 02/25/2024] Open
Abstract
Bis(acetylacetonato)oxidovanadium(IV) [(VO(acac)2], generally known as vanadyl acetylacetonate, has been shown to be preferentially sequestered in malignant tissue. Vanadium-48 (48V) generated with a compact medical cyclotron has been used to label VO(acac)2 as a potential radiotracer in positron emission tomography (PET) imaging for the detection of cancer, but requires lengthy synthesis. Current literature protocols for the characterization of VO(acac)2 require macroscale quantities of reactants and solvents to identify products by color and to enable crystallization that are not readily adaptable to the needs of radiotracer synthesis. We present an improved method to produce vanadium-48-labeled VO(acac)2, [48V]VO(acac)2, and characterize it using high-performance liquid chromatography (HPLC) with radiation detection in combination with UV detection. The approach is suitable for radiotracer-level quantities of material. These methods are readily applicable for production of [48V]VO(acac)2. Preliminary results of preclinical, small-animal PET studies are presented.
Collapse
|
2
|
Broder BA, Bhyuian MP, Freifelder R, Zhang HJ, Kucharski A, Makinen MW, Rotsch DA, Chen CT. Preliminary investigation of 48V-labeled VO(acac)2 for cancer imaging: An initial proof-of-concept study. Appl Radiat Isot 2022; 186:110270. [DOI: 10.1016/j.apradiso.2022.110270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/01/2022] [Accepted: 05/02/2022] [Indexed: 11/02/2022]
|
3
|
Hon J, Hwang MS, Charnetzki MA, Rashed IJ, Brady PB, Quillin S, Makinen MW. Kinetic characterization of the inhibition of protein tyrosine phosphatase-1B by Vanadyl (VO 2+) chelates. J Biol Inorg Chem 2017; 22:1267-1279. [PMID: 29071441 PMCID: PMC5671894 DOI: 10.1007/s00775-017-1500-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 10/12/2017] [Indexed: 10/18/2022]
Abstract
Protein tyrosine phosphatases (PTPases) are a prominent focus of drug design studies because of their roles in homeostasis and disorders of metabolism. These studies have met with little success because (1) virtually all inhibitors hitherto exhibit only competitive behavior and (2) a consensus sequence H/V-C-X5-R-S/T characterizes the active sites of PTPases, leading to low specificity of active site directed inhibitors. With protein tyrosine phosphatase-1B (PTP1B) identifed as the target enzyme of the vanadyl (VO2+) chelate bis(acetylacetonato)oxidovanadium(IV) [VO(acac)2] in 3T3-L1 adipocytes [Ou et al. J Biol Inorg Chem 10: 874-886, 2005], we compared the inhibition of PTP1B by VO(acac)2 with other VO2+-chelates, namely, bis(2-ethyl-maltolato)oxidovanadium(IV) [VO(Et-malto)2] and bis(3-hydroxy-2-methyl-4(1H)pyridinonato)oxidovanadium(IV) [VO(mpp)2] under steady-state conditions, using the soluble portion of the recombinant human enzyme (residues 1-321). Our results differed from those of previous investigations because we compared inhibition in the presence of the nonspecific substrate p-nitrophenylphosphate and the phosphotyrosine-containing undecapeptide DADEpYLIPQQG mimicking residues 988-998 of the epidermal growth factor receptor, a relevant, natural substrate. While VO(Et-malto)2 acts only as a noncompetitive inhibitor in the presence of either subtrate, VO(acac)2 exhibits classical uncompetitive inhibition in the presence of DADEpYLIPQQG but only apparent competitive inhibition with p-nitrophenylphosphate as substrate. Because uncompetitive inhibitors are more potent pharmacologically than competitive inhibitors, structural characterization of the site of uncompetitive binding of VO(acac)2 may provide a new direction for design of inhibitors for therapeutic purposes. Our results suggest also that the true behavior of other inhibitors may have been masked when assayed with only p-nitrophenylphosphate as substrate.
Collapse
|
4
|
Makinen MW, Salehitazangi M. The Structural Basis of Action of Vanadyl (VO 2+) Chelates in Cells. Coord Chem Rev 2014; 279:1-22. [PMID: 25237207 DOI: 10.1016/j.ccr.2014.07.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Much emphasis has been given to vanadium compounds as potential therapeutic reagents for the treatment of diabetes mellitus. Thus far, no vanadium compound has proven efficacious for long-term treatment of this disease in humans. Therefore, in review of the research literature, our goal has been to identify properties of vanadium compounds that are likely to favor physiological and biochemical compatibility for further development as therapeutic reagents. We have, therefore, limited our review to those vanadium compounds that have been used in both in vivo experiments with small, laboratory animals and in in vitro studies with primary or cultured cell systems and for which pharmacokinetic and pharmacodynamics results have been reported, including vanadium tissue content, vanadium and ligand lifetime in the bloodstream, structure in solution, and interaction with serum transport proteins. Only vanadyl (VO2+) chelates fulfill these requirements despite the large variety of vanadium compounds of different oxidation states, ligand structure, and coordination geometry synthesized as potential therapeutic agents. Extensive review of research results obtained with use of organic VO2+-chelates shows that the vanadyl chelate bis(acetylacetonato)oxidovanadium(IV) [hereafter abbreviated as VO(acac)2], exhibits the greatest capacity to enhance insulin receptor kinase activity in cells compared to other organic VO2+-chelates, is associated with a dose-dependent capacity to lower plasma glucose in diabetic laboratory animals, and exhibits a sufficiently long lifetime in the blood stream to allow correlation of its dose-dependent action with blood vanadium content. The properties underlying this behavior appear to be its high stability and capacity to remain intact upon binding to serum albumin. We relate the capacity to remain intact upon binding to serum albumin to the requirement to undergo transcytosis through the vascular endothelium to gain access to target tissues in the extravascular space. Serum albumin, as the most abundant transport protein in the blood stream, serves commonly as the carrier protein for small molecules, and transcytosis of albumin through capillary endothelium is regulated by a Src protein tyrosine kinase system. In this respect it is of interest to note that inorganic VO2+ has the capacity to enhance insulin receptor kinase activity of intact 3T3-L1 adipocytes in the presence of albumin, albeit weak; however, in the presence of transferrin no activation is observed. In addition to facilitating glucose uptake, the capacity of VO2+- chelates for insulin-like, antilipolytic action in primary adipocytes has also been reviewed. We conclude that measurement of inhibition of release of only free fatty acids from adipocytes stimulated by epinephrine is not a sufficient basis to ascribe the observations to purely insulin-mimetic, antilipolytic action. Adipocytes are known to contain both phosphodiesterase-3 and phosphodiesterase-4 (PDE3 and PDE4) isozymes, of which insulin antagonizes lipolysis only through PDE3B. It is not known whether the other isozyme in adipocytes is influenced directly by VO2+- chelates. In efforts to promote improved development of VO2+- chelates for therapeutic purposes, we propose synergism of a reagent with insulin as a criterion for evaluating physiological and biochemical specificity of action. We highlight two organic compounds that exhibit synergism with insulin in cellular assays. Interestingly, the only VO2+- chelate for which this property has been demonstrated, thus far, is VO(acac)2.
Collapse
|
5
|
Makinen MW, Bamba R, Ikejimba L, Wietholt C, Chen CT, Conzen SD. The vanadyl chelate bis(acetylacetonato)oxovanadium(IV) increases the fractional uptake of 2-(fluorine-18)-2-deoxy-D-glucose by cultured human breast carcinoma cells. Dalton Trans 2013; 42:11862-7. [PMID: 23644715 PMCID: PMC3733664 DOI: 10.1039/c3dt50549a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Detection of breast cancer by positron emission tomography (PET) imaging with 2-(fluorine-18)-2-deoxy-D-glucose (FDG) as the tracer molecule is limited in part by both tumor dimension and metabolic activity. While some types of aggressive breast cancers are associated with a high capacity for FDG uptake, more indolent breast cancers are characterized by low FDG uptake. Moreover, detection of malignant lesions in most clinical settings requires tumor dimensions ≥10 mm. Development of a method to increase the fractional uptake of FDG by cancer tissue would provide a means to detect smaller tumors. However, there is no clinically available pharmacologic reagent known to enhance the preferential uptake of FDG by cancer tissue. Because the vanadyl (VO(2+)) chelate bis(acetylacetonato)oxovanadium(IV) [VO(acac)2] is known to enhance cellular uptake of glucose, we have investigated whether VO(acac)2 facilitates enhanced uptake of FDG by cultured human breast carcinoma cells. We observed that the fractional uptake of FDG by cultured human MDA-MB-231 carcinoma cells is increased in the presence of VO(acac)2 in a dose dependent manner. Preliminary results with xenograft tumors generated in severely compromised, immunodeficient (SCID) female mice showed that VO(acac)2 treatment of mice 3-4 h prior to FDG injection enhanced FDG uptake by the malignant tissue by a factor >2.0 compared with that by normal surrounding tissue.
Collapse
|
6
|
Mustafi D, Peng B, Foxley S, Makinen MW, Karczmar GS, Zamora M, Ejnik J, Martin H. New vanadium-based magnetic resonance imaging probes: clinical potential for early detection of cancer. J Biol Inorg Chem 2009; 14:1187-97. [PMID: 19572156 DOI: 10.1007/s00775-009-0562-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Accepted: 06/18/2009] [Indexed: 12/25/2022]
Abstract
We have developed a magnetic resonance imaging (MRI) method for improved detection of cancer with a new class of cancer-specific contrast agents, containing vanadyl (VO(2+))-chelated organic ligands, specifically bis(acetylacetonato)oxovanadium(IV) [VO(acac)(2)]. Vanadyl compounds have been found to accumulate within cells, where they interact with intracellular glycolytic enzymes. Aggressive cancers are metabolically active and highly glycolytic; an MRI contrast agent that enters cells with high glycolytic activity could provide high-resolution functional images of tumor boundaries and internal structure, which cannot be achieved by conventional contrast agents. The present work demonstrates properties of VO(acac)(2) that may give it excellent specificity for cancer detection. A high dose of VO(acac)(2) did not cause any acute or short-term adverse reactions in murine subjects. Calorimetry and spectrofluorometric methods demonstrate that VO(acac)(2) is a blood pool agent that binds to serum albumin with a dissociation constant K (d) ~ 2.5 +/- 0.7 x 10(-7) M and a binding stoichiometry n = 1.03 +/- 0.04. Owing to its prolonged blood half-life and selective leakage from hyperpermeable tumor vasculature, a low dose of VO(acac)(2) (0.15 mmol/kg) selectively enhanced in vivo magnetic resonance images of tumors, providing high-resolution images of their interior structure. The kinetics of uptake and washout are consistent with the hypothesis that VO(acac)(2) preferentially accumulates in cancer cells. Although VO(acac)(2) has a lower relaxivity than gadolinium-based MRI contrast agents, its specificity for highly glycolytic cells may lead to an innovative approach to cancer detection since it has the potential to produce MRI contrast agents that are nontoxic and highly sensitive to cancer metabolism.
Collapse
|
7
|
Walsh AM, Mustafi D, Makinen MW, Lee RC. A surfactant copolymer facilitates functional recovery of heat-denatured lysozyme. Ann N Y Acad Sci 2006; 1066:321-7. [PMID: 16533935 DOI: 10.1196/annals.1363.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The triblock copolymer poloxamer 188 is a non-cytotoxic, nonionic surfactant with both hydrophobic and hydrophilic domains. We show that P188 is able to facilitate the recovery of catalytic activity of heat-denatured lysozyme in dilute solution at low molar ratios of P188:enzyme. Heat-denatured enzyme retained 55% of native activity. After treatment with P188, the enzyme's activity was 85% of native. Because of the low molar ratios used and the non-cytotoxic nature of the compound, P188 may be of potential use in burn therapy.
Collapse
|
8
|
Ou H, Yan L, Mustafi D, Makinen MW, Brady MJ. The vanadyl (VO2+) chelate bis(acetylacetonato)oxovanadium(IV) potentiates tyrosine phosphorylation of the insulin receptor. J Biol Inorg Chem 2005; 10:874-86. [PMID: 16235045 DOI: 10.1007/s00775-005-0037-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2005] [Accepted: 09/20/2005] [Indexed: 10/25/2022]
Abstract
We have compared the insulin-like activity of bis(acetylacetonato)oxovanadium(IV) [VO(acac)2], bis(maltolato)oxovanadium(IV) [VO(malto)2], and bis(1-N-oxide-pyridine-2-thiolato)oxovanadium(IV) [VO(OPT)2] in differentiated 3T3-L1 adipocytes. The insulin-like influence of VO(malto)2 and VO(OPT)2 was decreased compared with that of VO(acac)2. Also, serum albumin enhanced the insulin-like activity of all three chelates more than serum transferrin. Each of the three VO2+ chelates increased the tyrosine phosphorylation of proteins in response to insulin, including the beta-subunit of the insulin receptor (IRbeta) and the insulin receptor substrate-1 (IRS1). However, VO(acac)2 exhibited the greatest synergism with insulin and was therefore further investigated. Treatment of 3T3-L1 adipocytes with 0.25 mM VO(acac)2 in the presence of 0.25 mM serum albumin synergistically increased glycogen accumulation stimulated by 0.1 and 1 nM insulin, and increased the phosphorylation of IRbeta, IRS1, protein kinase B, and glycogen synthase kinase-3beta. Wortmannin suppressed all of these classical insulin-signaling activities exerted by VO(acac)2 or insulin, except for tyrosine phosphorylation of IRbeta and IRS1. Additionally, VO(acac)2 enhanced insulin signaling and metabolic action in insulin-resistant 3T3-L1 adipocytes. Cumulatively, these results provide evidence that VO(acac)2 exerts its insulin-enhancing properties by directly potentiating the tyrosine phosphorylation of the insulin receptor, resulting in the initiation of insulin metabolic signaling cascades in 3T3-L1 adipocytes.
Collapse
|
9
|
Mustafi D, Makinen MW. Structure and conformation of bis(acetylacetonato)oxovanadium(IV) and bis(maltolato)oxovanadium(IV) in solution determined by electron nuclear double resonance spectroscopy. Inorg Chem 2005; 44:5580-90. [PMID: 16060607 DOI: 10.1021/ic040120y] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structure and conformation of bis(acetylacetonato)oxovanadium(IV) [VO(acac)(2)] and bis(maltolato)oxovanadium(IV) [VO(malto)(2)] in frozen methanol have been determined by application of electron nuclear double resonance (ENDOR) spectroscopy. The positions of inner- and outer-sphere-coordinated solvent were assigned by ENDOR through use of selectively deuterated analogues of methanol. Similarly, the methyl and methylinyl proton resonance features of VO(acac)(2) were identified by site-selective deuteration. For VO(acac)(2), the ENDOR-determined metal-proton distances were best accounted for by a complex of tetragonal-pyramidal geometry, essentially identical to that determined by X-ray crystallography [Dodge, R. P.; Templeton, D. H.; Zalkin, A. J. Chem. Phys. 1961, 35, 55] but with an inner-sphere solvent molecule coordinated trans to the vanadyl oxygen and an axially positioned solvent molecule hydrogen-bonded to the vanadyl oxygen. In contrast to its trans conformation in crystals [Caravan, P.; et al. J. Am. Chem. Soc. 1995, 117, 12759], the VO(malto)(2) complex was found in a cis conformation whereby the donor oxygen atoms of one maltolato ligand occupied equatorial coordination sites. One of the donor oxygen atoms of the second maltolato ligand occupied the axial coordination site opposite the vanadyl oxygen atom, and the other an equatorial position. An inner-sphere-coordinated methanol molecule in the equatorial plane and a solvent molecule hydrogen-bonded to the vanadyl oxygen were also identified. No evidence for the trans isomer was observed.
Collapse
|
10
|
Savard PY, Sosa-Peinado A, Levesque RC, Makinen MW, Gagné SM. 1H, 13C and 15N backbone resonance assignments for TEM-1, a 28.9 kDa beta-lactamase from E. coli. JOURNAL OF BIOMOLECULAR NMR 2004; 29:433-434. [PMID: 15213455 DOI: 10.1023/b:jnmr.0000032503.96942.68] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
|
11
|
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.
Collapse
|
12
|
Mustafi D, Bekesi A, Vertessy BG, Makinen MW. Catalytic and structural role of the metal ion in dUTP pyrophosphatase. Proc Natl Acad Sci U S A 2003; 100:5670-5. [PMID: 12721364 PMCID: PMC156259 DOI: 10.1073/pnas.1031504100] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The metal ion dependence of the catalytic activity of recombinant Escherichia coli dUTP pyrophosphatase (dUTPase), an essential enzyme preventing incorporation of uracil into DNA, has been investigated by steady-state kinetic, electron paramagnetic resonance, and electron nuclear double resonance methods. Values of k(cat) and k(cat)K(m) were 4.5 +/- 0.1 s(-1) and 0.49 +/- 0.1 x 10(6) M(-1).s(-1) in the absence of divalent metal ions, 14.7 +/- 2.2 s(-1) and 25.1 +/- 7.4 x 10(6) M(-1).s(-1) in the presence of Mg(2+) or Mn(2+), and 24.2 +/- 3.6 s(-1) and 2.4 +/- 0.7 x 10(6) M(-1).s(-1) when supported by VO(2+) or bis(acetylacetonato)oxovanadium(IV). Binding of VO(2+) to the enzyme in the presence of dUDP, a nonhydrolyzable substrate analog, was specific and competitive with Mg(2+). Electron paramagnetic resonance spectra of the ternary enzyme-VO(2+)-chelate-dUDP complex revealed a pattern of (31)P superhyperfine coupling specifying two structurally equivalent phosphate groups equatorially coordinated to the VO(2+) ion. Proton electron nuclear double resonance spectra revealed an equatorial acetylacetonate ligand, indicating that one of the organic ligands had been displaced. By molecular graphics modeling, we show that the diphosphate group of enzyme-bound dUDP is sterically accessible to a hemi-chelate form of VO(2+). We propose a similar location compatible with all kinetic and spectroscopic results to account for the reactivity of VO(2+) and the VO(2+)-chelate in dUTP hydrolysis. In this location the metal ion could promote an ordered conformation of the C-terminal fragment that is obligatory for catalysis but dynamically flexible in the free enzyme.
Collapse
|
13
|
Makinen MW, Kuo LC, Yim MB, Wells GB, Fukuyama JM, Kim JE. Ground term splitting of high-spin cobalt(2+) ion as a probe of coordination structure. 1. Dependence of the splitting on coordination geometry. J Am Chem Soc 2002. [DOI: 10.1021/ja00304a035] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
14
|
Makinen MW, Hill SC, Zeppezauer M, Little CL, Burdett JK. Molecular spectroscopy of high-spin Co(II). Polarized single crystal electronic absorption spectra of structurally defined tetracoordinate complexes with sulfur-donor ligands. J Am Chem Soc 2002. [DOI: 10.1021/ja00247a038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
15
|
Mustafi D, Sachleben JR, Wells GB, Makinen MW. Structure and conformation of spin-labeled amino acids in frozen solutions determined by electron nuclear double resonance. 1. Methyl N-(2,2,5,5-tetramethyl-1-oxypyrrolinyl-3-carbonyl)-L-alanate, a molecule with a single preferred conformation. J Am Chem Soc 2002. [DOI: 10.1021/ja00163a012] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
16
|
Kuo LC, Lipscomb WN, Makinen MW. Polarized single-crystal absorption spectra of cobalt2+-carboxypeptidase A. J Am Chem Soc 2002. [DOI: 10.1021/ja00276a049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
17
|
Wells GB, Makinen MW. ENDOR-determined molecular geometries of spin-labeled fluoroanilides in frozen solution. J Am Chem Soc 2002. [DOI: 10.1021/ja00227a012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
18
|
Makinen MW, Fukuyama JM, Kuo LC. Evidence by gel filtration at subzero temperatures for the covalent reaction intermediate of carboxypeptidase A in ester hydrolysis. J Am Chem Soc 2002. [DOI: 10.1021/ja00373a070] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
19
|
Kuo LC, Makinen MW. Ground term splitting of high-spin cobalt(2+) ion as a probe of coordination structure. 2. The ligand environment of the active site metal ion of carboxypeptidase A in ester hydrolysis. J Am Chem Soc 2002. [DOI: 10.1021/ja00304a036] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
20
|
Mustafi D, Telser J, Makinen MW. Molecular geometry of vanadyl-adenine nucleotide complexes determined by EPR, ENDOR, and molecular modeling. J Am Chem Soc 2002. [DOI: 10.1021/ja00041a046] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
21
|
Mustafi D, Boisvert WE, Makinen MW. Multiple rotamers of 3-(2,2,5,5-tetramethyl-1-oxypyrrolinyl)-2-propen-1-ol, a stereospecific substrate of liver alcohol dehydrogenase: determination of molecular structure and conformation by electron nuclear double resonance. J Am Chem Soc 2002. [DOI: 10.1021/ja00062a038] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
22
|
Wells GB, Mustafi D, Makinen MW. Structure and conformation of spin-labeled amino acids in frozen solutions determined by electron nuclear double resonance. 2. Methyl N-(2,2,5,5-tetramethyl-1-oxypyrrolinyl-3-carbonyl)-L-tryptophanate, a molecule with multiple conformations. J Am Chem Soc 2002. [DOI: 10.1021/ja00163a013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
23
|
Mustafi D, Makinen MW. Structure, Conformation, and Probable Mechanism of Hydrolysis of a Spin-Labeled Penicillin Revealed by Electron Nuclear Double Resonance Spectroscopy. J Am Chem Soc 2002. [DOI: 10.1021/ja00130a014] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
24
|
Jiang FS, Makinen MW. NMR and ENDOR Conformational Studies of the Vanadyl Guanosine 5'-Monophosphate Complex in Hydrogen-Bonded Quartet Assemblies. Inorg Chem 2002. [DOI: 10.1021/ic00111a021] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
25
|
Joela H, Mustafi D, Fair CC, Makinen MW. Structure and conformation of spin-labeled methyl L-phenylalanate and L-phenylalanine determined by electron nuclear double resonance spectroscopy. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100176a021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|