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Lillo V, Galán-Mascarós JR. Transition metal complexes with oligopeptides: single crystals and crystal structures. Dalton Trans 2014; 43:9821-33. [PMID: 24874062 DOI: 10.1039/c4dt00650j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The coordination chemistry of short chain peptides with transition metals is described in terms of the available crystal structures. Despite their high interest as synthetic models for metalloproteins and as building blocks for molecular materials based on the tuneable properties of oligopeptides, single crystal X-ray diffraction studies are scarce. A perusal of the most relevant results in this field allows us to define the main characteristics of oligopeptide-metal interactions, the fundamental problems for the crystallization of these complexes, and some hints to identify future promising approaches to advance the development of metallopeptide chemistry.
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Affiliation(s)
- Vanesa Lillo
- Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans, 16. E-43007, Tarragona, Spain.
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Kumar A, Zhu X, Walsh K, Prabhakar R. Theoretical Insights into the Mechanism of Selective Peptide Bond Hydrolysis Catalyzed by [Pd(H2O)4]2+. Inorg Chem 2009; 49:38-46. [DOI: 10.1021/ic901071v] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amit Kumar
- Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146
| | - Xiaoxia Zhu
- Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146
| | - Kathryn Walsh
- Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146
| | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146
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Stoffregen SA, Griffin AKK, Kostić NM. Thioether Complexes of Palladium(II) and Platinum(II) as Artificial Peptidases. Residue-Selective Peptide Cleavage by a Palladium(II) Complex. Inorg Chem 2005; 44:8899-907. [PMID: 16296845 DOI: 10.1021/ic0506613] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the synthesis and characterization of perchlorate salts containing the following three novel complex cations each with a bidentate thioether ligand: binuclear cis-[Pt(CH3SCH2CH2CH2SCH3)(mu-OH)]22+, mononuclear cis-[Pt(CH3SCH2CH2CH2SCH3)(H2O)2]2+, and mononuclear cis-[Pd(CH3SCH2CH2CH2SCH3)(H2O)2]2+. Despite their analogous compositions, the mononuclear Pt(II) and Pd(II) complexes differ in the selectivity with which they promote the hydrolysis of polypeptides. The complex cis-[Pt(CH3SCH2CH2CH2SCH3)(H2O)2]2+ promotes slow but selective cleavage of Met-Pro peptide bonds at pH 2.0. The selectivity of the complex cis-[Pd(CH3SCH2CH2CH2SCH3)(H2O)2]2+ is pH-dependent. At pH 2.0, this Pd(II) complex promotes residue-selective hydrolysis of the X-Y bond in X-Y-Met and X-Y-His sequences; the rate is enhanced when residue Y is proline. At pH 7.0, this kinetic preference becomes sequence-selective in that the Pd(II) complex exclusively cleaves the X-Pro bond in X-Pro-Met and X-Pro-His sequences. The enhanced reactivity of the X-Pro amide group is attributed to the high basicity of its carbonyl oxygen atom. Binding of the metal(II) atom enhances the electrophilicity of the carbonyl carbon atom and promotes nucleophilic attack by a solvent water molecule. The bidentate thioether ligand disfavors the formation of hydrolytically unreactive complexes, allowing the Pd(II) complex to promote the cleavage reaction.
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Affiliation(s)
- Stacey A Stoffregen
- Department of Chemistry, Gilman Hall, Iowa State University, Ames, Iowa 50011-3111, USA
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Milović NM, Dutca LM, Kostić NM. Combined use of platinum(II) complexes and palladium(II) complexes for selective cleavage of peptides and proteins. Inorg Chem 2003; 42:4036-45. [PMID: 12817959 DOI: 10.1021/ic026280w] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study shows, for the first time, the advantages of combining two transition-metal complexes as selective proteolytic reagents. In this procedure, cis-[Pt(en)(H(2)O)(2)](2+) is followed by [Pd(H(2)O)(4)](2+). In the peptide AcAla-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala, the Pt(II) reagent cleaves the Met6-Ala7 peptide bond, whereas the Pd(II) reagent cleaves the Gly4-Gly5 bond. In the peptide AcVal-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala, the Pt(II) reagent cleaves the Met11-Ala12 peptide bond, whereas the Pd(II) reagent cleaves the Gly3-Gly4 bond. All cleavage reactions are regioselective and complete at pH 2.0 and 60 degrees C. Each metal ion binds to an anchoring side chain and then, as a Lewis acid, activates a proximal peptide bond toward hydrolysis by the solvent water. The selectivity in cleavage is a consequence of the selectivity in this initial anchoring. Both Pt(II) and Pd(II) reagents bind to the methionine side chain, whereas only the Pd(II) reagent binds to the histidine side chain under the reaction conditions. Consequently, only methionine residues direct the cleavage by the Pt(II) reagent, whereas both methionine and histidine residues direct the cleavage by the Pd(II) reagent. The Pt(II) reagent cleaves the first bond downstream from the anchor, i.e., the Met-Z bond. The Pd(II) reagent cleaves the second bond upstream from the anchor, i.e., the X-Y bond in the X-Y-Met-Z and in the X-Y-His-Z segments. The diethylenetriamine complex [Pt(dien)(H(2)O)](2+) cannot promote cleavage. Its prior binding to the Met11 residue in the second peptide prevents the Pd(II) reagents from binding to Met11 and cleaving the Gly9-Gly10 bond and directs the cleavage by the Pd(II) reagent exclusively at the Gly3-Gly4 bond. Our new method was tested on equine myoglobin, which contains 2 methionine residues and 11 histidine residues. The complete methionine-directed cleavage of the Met55-Lys56 and Met131-Thr132 bonds by the Pt(II) reagent produced three fragments, suitable for various biochemical applications because they are relatively long and contain amino and carboxylic terminal groups. The deliberately incomplete histidine-directed cleavage of the long fragments 1.55 and 56.131 at many sites by the Pd(II) reagent produced numerous short fragments, suitable for protein identification by mass spectrometry. The ability of combined Pt(II) and Pd(II) complexes to cleave proteins with explicable and adjustable selectivity and with good yields bodes well for their greater use in biochemical and bioanalytical practice.
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Affiliation(s)
- Nebojsa M Milović
- Department of Chemistry, Gilman Hall, Iowa State University, Ames, Iowa 50011-3111, USA
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Milović NM, Kostić NM. Palladium(II) complex as a sequence-specific peptidase: hydrolytic cleavage under mild conditions of X-Pro peptide bonds in X-Pro-Met and X-Pro-His segments. J Am Chem Soc 2003; 125:781-8. [PMID: 12526679 DOI: 10.1021/ja027408b] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The X-Pro peptide bond (in which X represents any amino acid residue) in peptides and proteins is resistant to cleavage by most proteolytic enzymes. We show that [Pd(H(2)O)(4)](2+) ion can selectively hydrolyze this tertiary peptide bond within the X-Pro-Met and X-Pro-His sequence segments. The hydrolysis requires an equimolar amount of the Pd(II) reagent and occurs under mild conditions-at temperature as low as 20 degrees C (with half-life of 1.0 h at pH 2.0) and at pH as high as 7.0 (with half-life of 4.2 h at pH 7.0 and 40 degrees C). The secondary peptide bond, exemplified by X-Gly in the X-Gly-Met and X-Gly-His sequence segments, however, is cleaved only in weakly acidic solution (pH < 4.0) and more slowly (half-life is 4.2 h at pH 2.0 and 60 degrees C). We explain the sequence-specificity of X-Pro cleavage by NMR spectroscopic analysis of the coordination of the X-Pro-Met segment to the Pd(II) ion. We give indirect evidence for the mechanism of cleavage by analyzing the conformation of the scissile X-Pro peptide bond, and by comparing the rate constants for the cleavage of the tertiary X-Pro peptide bond, the tertiary X-Sar peptide bond (Sar is N-methyl glycine), and the typical secondary X-Gly peptide bond in a set of analogous oligopeptides. Methionine and histidine side chains provide the recognition by selectively binding (anchoring) the Pd(II) ion. The proline residue provides the enhanced activity because its tertiary X-Pro peptide bond favors the cleavage-enhancing binding of the Pd(II) ion to the peptide oxygen atom and prevents the cleavage-inhibiting binding of the Pd(II) ion upstream of the anchoring (histidine or methionine) residue. Cleavage can be switched from the residue-selective to the sequence-specific mode by simply adjusting the pH of the aqueous solution. In acidic solutions, any X-Y bond in X-Y-Met and X-Y-His segments is cleaved because the cleavage is directed by anchoring methionine and histidine residues. In mildly acidic and neutral solutions, only the X-Pro bond in X-Pro-Met and X-Pro-His sequences is cleaved because of an interplay between the anchoring residue and the proline residue preceding it. Because Pro-Met and Pro-His sequences are rare in proteins, this sequence-specific cleavage is potentially useful for the removal of the fusion tags from the bioengineered fusion proteins.
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Affiliation(s)
- Nebojsa M Milović
- Department of Chemistry, Gilman Hall, Iowa State University, Ames 50011-3111, USA
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Milović NM, Kostić NM. Interplay of terminal amino group and coordinating side chains in directing regioselective cleavage of natural peptides and proteins with palladium(II) complexes. Inorg Chem 2002; 41:7053-63. [PMID: 12495344 DOI: 10.1021/ic025640c] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Palladium(II) ions anchored to side chains of histidine and methionine residues in peptides and proteins in weakly acidic aqueous solutions promote hydrolytic cleavage of proximate amide bonds in the backbone. In this study, we determine how attachment of Pd(II) ions to histidine and methionine anchors and also to the terminal amino group in six natural peptides (chains A and B of insulin, segment 11-14 of angiotensinogen, pentagastrin, angiotensin II, and segment 3-8 of angiotensin II) and two proteins (ubiquitin and cytochrome c) affects regioselectivity and rate of backbone cleavage. These Pd(II)-promoted reactions follow a clear pattern of regioselectivity, directed by the anchoring side chains. When the Pd(II) reagent is nonspecifically anchored to the terminal amino group, the ligating site that is present in almost all proteins, the cleavage is fortunately absent. When the reagent is anchored to a residue in positions 1, 2, or 3, cleavage is absent, because the terminal amino group and deprotonated amide nitrogen atom(s) interposed between it and the anchor "lock" the Pd(II) ion in hydrolytically inactive chelate complexes. When the reagent is anchored to residues in positions beyond 3, the second amide bond upstream from the anchor is regioselectively cleaved in all cases when the anchor was "isolated," that is, flanked by noncoordinating side chains. Segment 3-8 of angiotensin II undergoes additional cleavage, which we explain by determining the rate constants for the cleavage, identifying the rate-limiting displacement of ethylenediamine ligand from the Pd(II) ion, and detecting several intermediates. Experiments with cytochrome c demonstrate that the number of cleavage sites can be controlled by adjusting the mole ratio of the Pd(II) reagent to the substrate. Our inorganic peptidases are useful for biochemical applications because their regioselectivity and reactivity set them apart from proteolytic enzymes and organic chemical reagents.
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Affiliation(s)
- Nebojsa M Milović
- Department of Chemistry, Gilman Hall, Iowa State University, Ames 50011-3111, USA
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Milović NM, Kostić NM. Palladium(II) complexes, as synthetic peptidases, regioselectively cleave the second peptide bond "upstream" from methionine and histidine side chains. J Am Chem Soc 2002; 124:4759-69. [PMID: 11971725 DOI: 10.1021/ja012366x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Palladium(II) complexes promote hydrolysis of natural and synthetic oligopeptides with unprecedented regioselectivity; the only cleavage site is the second peptide bond upstream from a methionine or a histidine side chain, that is, the bond involving the amino group of the residue that precedes this side chain. We investigate this regioselectivity with four N-acetylated peptides as substrates: neurotransmitter methionine enkephalin (Ac-Tyr-Gly-Gly-Phe-Met) and synthetic peptides termed Met-peptide (Ac-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala), His-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met(OX)-Ala-Ala-Arg-Ala), in which a Met is oxidized to sulfone, and HisMet-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala). While maintaining protein-like properties, these substrates are suitable for quantitative study since their coordination to Pd(II) ion can be determined (by NMR spectroscopy), and the cleavage fragments can be separated (by HPLC methods) and identified (by MALDI mass spectrometry). The only peptide bonds cleaved were the Gly3-Phe4 bond in methionine enkephalin, Gly4-Gly5 bond in Met-peptide, Gly3-Gly4 in His-peptide, and Gly3-Gly4 and Gly9-Gly10 bonds in HisMet-peptide. We explain this consistent regioselectivity of cleavage by studying the modes of Met-peptide coordination to the Pd(II) ion in [Pd(H(2)O)(4)](2+) complex. In acidic solution, the rapid attachment of the Pd(II) complex to the methionine side chain is followed by the interaction of the Pd(II) ion with the peptide backbone upstream from the anchor. In the hydrolytically active complex, Met-peptide is coordinated to Pd(II) ion as a bidentate ligand - via sulfur atom in the methionine side chain and the first peptide nitrogen upstream from this anchor - so that the Pd(II) complex approaches the scissile peptide bond. Because the increased acidity favors this hydrolytically active complex, the rate of cleavage guided by either histidine or methionine anchor increased as pH was lowered from 4.5 to 0.5. The unwanted additional cleavage of the first peptide bond upstream from the anchor is suppressed if pH is kept above 1.2. Four Pd(II) complexes cleave Met-peptide with the same regioselectivity but at somewhat different rates. Complexes in which Pd(II) ion carries labile ligands, such as [Pd(H(2)O)(4)](2+) and [Pd(NH(3))(4)](2+), are more reactive than those containing anionic ligands, such as [PdCl(4)](2)(-), or a bidentate ligand, such as cis-[Pd(en)(H(2)O)(2)](2+). When both methionine and histidine residues are present in the same substrate, as in HisMet-peptide, 1 molar equivalent of the Pd(II) complex distributes itself evenly at both anchors and provides partial cleavage, whereas 2 molar equivalents of the promoter completely cleave the second peptide bond upstream from each of the anchors. The results of this study bode well for growing use of palladium(II) reagents in biochemical and bioanalytical practice.
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Affiliation(s)
- Nebojsa M Milović
- Department of Chemistry, Iowa State University, Ames, Iowa 50011-3111, USA
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Ward MS, Shepherd RE. Comparison of energy-minimized structures of [PdII(mida)] complexes of peptide sequences used in immobilized metal ion affinity chromatography protein separations. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(00)00312-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Klein, A, Tsiveriotis, P, Malandrinos, G, Hadjiliadis, N.. Platinum(II) and Palladium(II) Complexes with Histidine and Histidyl Containing Peptides: Structure and Reactivity. REV INORG CHEM 2000. [DOI: 10.1515/revic.2000.20.4.305] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Chen Y, Pasquinelli R, Ataai M, Koepsel RR, Kortes RA, Shepherd RE. Coordination of two high-affinity hexamer peptides to copper(II) and palladium(II) models of the peptide-metal chelation site on IMAC resins. Inorg Chem 2000; 39:1180-6. [PMID: 12526408 DOI: 10.1021/ic990520z] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The coordination of peptides Ser-Pro-His-His-Gly-Gly (SPHHGG) and (His)6 (HHHHHH) to [PdII(mida)(D2O)] (mida2- = N-methyliminodiacetate) was studied by 1H NMR as model reactions for CuII(iminodiacetate)-immobilized metal affinity chromatography (IMAC) sites. This is the first direct physical description of peptide coordination for IMAC. A three-site coordination is observed which involves the first, third, and fourth residues along the peptide chain. The presence of proline in position 2 of SPHHGG achieves the best molecular mechanics and bonding angles in the coordinated peptide and enhances the interaction of the serine amino nitrogen. Histidine coordination of H1, H3, and H4 of (His)6 and H3 and H4 of SPHHGG was detected by 1H NMR contact shifts and H/D exchange of histidyl protons. The EPR spectra of SPHHGG and HHHHHH attached to the [CuII(mida)] unit were obtained for additional modeling of IMAC sites. EPR parameters of the parent [Cu(mida)(H2O)2] complex are representative: gzz = 2.31; gyy = 2.086; gxx = 2.053; A parallel = 161G; AN = 19G (three line, one N coupling). Increased rhombic distortion is detected relative to the starting aqua complex in the order of [Cu(mida)L] for distortion of HHHHHH > SPHHGG > (H2O)2. The lowering of symmetry is also seen in the decrease in the N-shf coupling, presumably to the imino nitrogen of mida2- in the order 19 G (H2O), 16 G (SPHHGG) and 11 G (HHHHHH). Visible spectra of the [Cu(mida)(SPHHGG)] and [Cu(mida)(HHHHHH)] as a function of pH indicate coordination of one histidyl donor at ca. 4.5, two in the range of pH 5-7, and two chelate ring attachments involving the terminal amino donor for SPHHGG or another histidyl donor of HHHHHH in the pH domain of 7-8 in agreement with the [PdII(mida)L] derivatives which form the two-chelate-ring attachment even at lower pH as shown by the 1H NMR methods.
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Affiliation(s)
- Y Chen
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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Coordination of the six-mer peptide Gly-His-Pro-His-His-Gly to CuII and PdII N-methyliminodiacetate complexes as IMAC chelation site models. J Inorg Biochem 1999. [DOI: 10.1016/s0162-0134(99)00129-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Tsiveriotis P, Hadjiliadis N. Studies on the interaction of histidyl containing peptides with palladium(II) and platinum(II) complex ions. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00076-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Tsiveriotis P, Hadjiliadis N, Stavropoulos G. NMR study of the interaction of platinum(II) and palladium(II) complex ions with His–Ala and His–Gly–Ala. Inorganica Chim Acta 1997. [DOI: 10.1016/s0020-1693(97)05454-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Parac TN, Kostić NM. Effects of Linkage Isomerism and of Acid−Base Equilibria on Reactivity and Catalytic Turnover in Hydrolytic Cleavage of Histidyl Peptides Coordinated to Palladium(II). Identification of the Active Complex between Palladium(II) and the Histidyl Residue. J Am Chem Soc 1996. [DOI: 10.1021/ja960168d] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tatjana N. Parac
- Contribution from the Department of Chemistry, Iowa State University, Ames, Iowa 50011
| | - Nenad M. Kostić
- Contribution from the Department of Chemistry, Iowa State University, Ames, Iowa 50011
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Parac TN, Kostić NM. New Selectivity and Turnover in Peptide Hydrolysis by Metal Complexes. A Palladium(II) Aqua Complex Catalyzes Cleavage of Peptides Next to the Histidine Residue. J Am Chem Soc 1996. [DOI: 10.1021/ja952162e] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tatjana N. Parac
- Contribution from the Department of Chemistry, Iowa State University, Ames, Iowa 50011
| | - Nenad M. Kostić
- Contribution from the Department of Chemistry, Iowa State University, Ames, Iowa 50011
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Kane-Maguire LAP, Riley PJ. HIGH FIELD NMR STUDY OF THE BINDING OF LEAD(II) TO CYSTEINE AND GLUTATHIONE. J COORD CHEM 1993. [DOI: 10.1080/00958979308035150] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Interaction of palladium(II) with DL-selenamethionine in acidic aqueous solution. TRANSIT METAL CHEM 1991. [DOI: 10.1007/bf01024068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Binary complexes of palladium(II) with peptides and ternary complexes of palladium(II) with peptides and nucleosides-nucleotides. Coord Chem Rev 1990. [DOI: 10.1016/0010-8545(90)80038-u] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Mixed ligand complexes of cadmium(II) involving nitrilotriacetic acid. J CHEM SCI 1990. [DOI: 10.1007/bf02861566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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23
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Shoukry MM. Ternary complexes of zinc(II) with nitrilotriacetic acid and some selected thiol amino-acids and related molecules. Talanta 1989; 36:1151-3. [DOI: 10.1016/0039-9140(89)80018-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/1988] [Revised: 03/28/1989] [Accepted: 06/02/1989] [Indexed: 11/25/2022]
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Equilibrium and hydrolysis of?-amino acid esters in ternary complexes of copper(II) involving glycyl-L-tyrosine. TRANSIT METAL CHEM 1989. [DOI: 10.1007/bf01032507] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ternary complexes of copper(II) involving diethylenetriamine and their role in the promotion of hydrolysis of ?-amino acid esters. TRANSIT METAL CHEM 1988. [DOI: 10.1007/bf01225132] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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28
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Shoukry MM, Khairy EM, Saeed A. MIXED-LIGAND COMPLEXES OF PALLADIUM(II) WITH DIETHYLENETRIAMINE. J COORD CHEM 1988. [DOI: 10.1080/00958978808073921] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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29
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Shoukry MM, Khairy EM, Saeed A. Hydrolysis of?-amino acid esters in ternary complexes of copper(II) involving glycyl-DL-valine. TRANSIT METAL CHEM 1988. [DOI: 10.1007/bf01087808] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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30
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Equilibrium and hydrolysis of ?-amino acid esters in mixed-ligand complexes with diethylenetriaminepalladium(II). TRANSIT METAL CHEM 1987. [DOI: 10.1007/bf01024021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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31
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Shoukry MM, Mahgoub AE, Hosny WM. Mixed ligand complexes of palladium(II) with diethylenetriamine as a primary ligand and amino acids as secondary ligands. TRANSIT METAL CHEM 1987. [DOI: 10.1007/bf01023138] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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The palladium(II) promoted hydrolysis of the methyl esters of glycyl-L-leucine, glycyl-L-alanine and L-alanylglycine. Inorganica Chim Acta 1986. [DOI: 10.1016/s0020-1693(00)86341-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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