The interaction of L-(+)-histidine methyl ester with metal ions. Part II. The metal-ion catalysed base hydrolysis of L-(+)-histidine methyl ester

1971 ◽  
pp. 1524 ◽  
Author(s):  
R. W. Hay ◽  
P. J. Morris
Keyword(s):  
Methyl Ester ◽  
Metal Ions ◽  
Metal Ion ◽  
Base Hydrolysis ◽  
Hydrolysis Of

scholarly journals Applications of Coordination Chemistry in Biological Systems

2014 ◽  
Vol 70 (a1) ◽  
pp. C1376-C1376
Author(s):  
Gurpreet Kaur ◽  
Richard Hartshorn
Keyword(s):  
Metal Ions ◽  
Metal Binding ◽  
Binding Sites ◽  
Metal Ion ◽  
Hydrolytic Enzymes ◽  
Dinuclear Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nitrophenyl Phosphate ◽  
Hydrolysis Of

A novel 2,2′:6′,2″-terpyridine–picolylamine-based bridging ligand has been synthesized and fully characterized using a variety of analysis techniques including single crystal X-ray diffraction. As shown in figure (a), the ligand has both tridentate and bidentate metal binding sites available to coordinate with various metal ions. By varying the size of anions both dinuclear complexes and supramolecular assemblies have been produced. Addition of metal salts containing small anions like halides result in formation of Cu2L and Zn2L dinuclear complexes, figure (b), where one metal ion binds at each of the binding sites of the ligand. The metal ions in these complexes mimic active site of the hydrolytic enzymes and promote phosphatediester hydrolysis of model DNA/RNA compounds. Nearly ten times increase in the rate of hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) is observed in comparison to the parent terpyridine and picolylamine complexes under physiological conditions. Larger anions like PF6-, ClO4-, SO42- , NO3- result in formation of Zn4L4 type squares via. head-to-head and tail-to-tail, HH-TT, (H=tridentate site, T=bidentate site) coordination of the ligand. The octahedrally bound Zn(II) ion between two tridentate sites can be replaced with Fe(II) to prepare Fe2Zn2L4 squares. A flat molecule of terephthalic acid was also deliberately encapsulated in the middle of the Fe2Zn2L4 square as shown in figure (c). The head-to-tail, HT, coordination of the ligand in case of Ni(II) results in formation of decanickel wheels, like [Ni10L10Cl4(H2O)6](Cl)15Br·~140H2O shown in figure (d). Due to the large structure of the molecule X-ray crystallographic studies rather have been quite challenging.

The recognition and catalytic hydrolysis of ATP by protonated phenanthroline-bridged polyamine and (or) Ca(II), Mg(II), Zn(II), and La(III) ions

2004 ◽  
Vol 82 (4) ◽  
pp. 504-512 ◽  
Author(s):  
Yan-He Guo ◽  
Qing-Chun Ge ◽  
Hai Lin ◽  
Hua-Kuan Lin ◽  
Shou-Rong Zhu
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Atp Hydrolysis ◽  
Amino Nitrogen ◽  
Supramolecular Interactions ◽  
Hydrolysis Rate ◽  
Catalytic Hydrolysis ◽  
Mixed Ligands ◽  
Hydrolysis Of ◽  
Protonated Ligand

The supramolecular interactions of 2,9-di(((2′-phenylamino)ethyleneamino)methyl)-1,10-phenanthroline (L) and (or) metal ions (M = Ca2+, Mg2+, Zn2+, or La3+) with nucleotides were investigated. Furthermore, the hydrolysis of ATP catalyzed by a protonated ligand and (or) a metal ion (M = Ca2+, Mg2+, Zn2+, or La3+) was studied at pH 7.6 using 31P NMR spectra. Kinetics studies show that at pH 7.6 the protonated ligand, with a rate constant of 2.9 × 10–4 min–1, does not significantly promote ATP hydrolysis. However, in the presence of Ca2+, Mg2+, Zn2+, or La3+ ions, L can accelerate the hydrolysis of ATP, with corresponding rate constants of 5.73, 1.48, 6.76, and 31.7 × 10–3 min–1, respectively, which are about 29-, 7.5-, 34-, and 159-fold faster than the hydrolysis rate of free ATP. By comparison with M–ATP (M = Ca2+, Mg2+, and La3+) systems, the rates of M–L–ATP were also promoted. This has been achieved through the effective recognition of ATP and the availability of a good intramolecular nucleophile, i.e., a free amino nitrogen atom of L. Compared with the Zn2+–ATP system, the decrease in the rate of the Zn2+–L–ATP system at pH 7.6 may be attributed to the competition between the mixed ligands in binding Zn2+. Similar to L–ATP, the hydrolysis reactions in the Zn2+–L–ATP or M–L–ATP (M = Ca2+, Mg2+, and La3+) systems occur through an addition–elimination type mechanism, in which phosphoramidate intermediates were observed at 2.88 and 4.06 parts per million (ppm) in the L–ATP and Mg2+–L–ATP systems, respectively. Here, metal ions add control or regulation to the hydrolysis reaction. Key words: recognition, ATP hydrolysis, metal ions, phenanthroline-bridged polyamine.

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