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Gorle AK, Rajaratnam P, Chang CW, von Itzstein M, Berners-Price SJ, Farrell NP. Glycans as Ligands in Bioinorganic Chemistry. Probing the Interaction of a Trinuclear Platinum Anticancer Complex with Defined Monosaccharide Fragments of Heparan Sulfate. Inorg Chem 2019; 58:7146-7155. [PMID: 30632736 DOI: 10.1021/acs.inorgchem.8b03035] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We report herein a detailed NMR study of the aquation and subsequent covalent binding of the trinuclear clinical agent [{ trans-PtCl(15NH3)2}2{μ- trans-Pt(15NH3)2(15NH2(CH2)615NH2)2}]4+ (1, 1,0,1/ t, t, t or Triplatin) with three d-glucosamine residues containing varied O-sulfate and N-sulfate or N-acetyl substitutions, which represent monosaccharide fragments present within the repeating disaccharide sequences of cell surface heparan sulfate (HS). The monosaccharides GlcNS(6S), GlcNS, and GlcNAc(6S) were synthesized in good yield from a common 4,6-diol α-methyl glucopyranoside intermediate. The reactions of 15N-1 with sodium sulfate, GlcNS(6S), GlcNS, and GlcNAc(6S) were followed by 2D [1H,15N] heteronuclear single quantum coherence (HSQC) NMR spectroscopy using conditions (298 K, pH ≈5.4) similar to those previously used for other anionic systems, allowing for a direct comparison. The equilibrium constants (p K1) for the aquation of 1 in the presence of GlcNS(6S) and GlcNS were slightly higher compared to that of the aquation in a sulfate solution, while a comparable p K1 value was observed in the presence of GlcNAc(6S). A comparison of the rate constants for sulfate displacement of the aqua ligand showed preferential binding to 2- N-sulfate compared to 6- O-sulfate but a more rapid liberation. For disulfated GlcNS(6S), equilibrium conditions were achieved rapidly (9 h) and strongly favored the dichloro form, with <2% sulfato species observed. The value of kL1 was up to 15-fold lower than that for binding to sulfate, whereas the rate constant for the reverse ligation ( k-L1) was comparable. Equilibrium conditions were achieved much more slowly (∼ 100 h) for the reactions of 1 with GlcNS and GlcNAc(6S), attributed to covalent binding also to the N-donor of the sulfamate (GlcNS) group and the O-donor of the N-acetyl [GlcNAc(6S)] group. The rate constants ( kL2) were 20-40-fold lower than that for binding to the 2- N- or 6- O-sulfate, but the binding was less reversible, so that their equilibrium concentrations (5-8%) were comparable to the 2- N- or 6- O-sulfate-bound species. The results emphasize the relevance of glycans in bioinorganic chemistry and underpin a fundamental molecular description of the HS-Pt interactions that alter the profile of platinum agents from cytotoxic to metastatic in a systematic manner.
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Affiliation(s)
- Anil Kumar Gorle
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia
| | - Premraj Rajaratnam
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia
| | - Chih-Wei Chang
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia
| | - Mark von Itzstein
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia
| | - Susan J Berners-Price
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia
| | - Nicholas P Farrell
- Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia.,Department of Chemistry , Virginia Commonwealth University , Richmond , Virginia 23284 , United States
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Inoue Y, Nagasawa K, Iwashita T. Depolymerization of heparin with diazomethane. Structure of N,O-methylated, even-numbered oligosaccharides produced by β-eliminative cleavage of the 2-amino-2-deoxyglycosylic linkage. Carbohydr Res 1984. [DOI: 10.1016/0008-6215(84)85251-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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