Peptides zinc complexes

Fig. 10. The three best COSMOS-NMR force field results of a peptide-zinc complex obtained with NOE as well as chemical shift pseudo-forces. Zn-X bonds are shown if the distance is shorter than 2.5 A. The force field search for the most stable complex was run with a free Ziv ion.

Zinc complexes of peptides with N-terminal cysteine are monomeric of the form ZnL2 where the peptide is an anion with the SH deprotonated. Tetrahedral N2S2 coordination is observed with the chelating peptides and Zn(Cys-Gly-NH2)2 was structurally characterized.857... 

Methyl- l-[methyl-(2-pyridin-2-yl-ethyl)amino]propane-2-thiol (108) is a tridentate N2S ligand with an aliphatic thiolate ligand. The single-crystal X-ray structures demonstrate that the zinc complexes are close structural analogs of the His2Cys site found in peptide deformylase.873... 

Lelais G, Seebach D, Jaun B, Mathad RI, Flogel O, Rossi F, Campo M, Wort-mann A (2006) Beta-Peptidic Secondary Structures fortified and enforced by Zn2+ Complexation - On the Way to Beta-Peptidic Zinc Fingers Helv Chim Acta 89 361 103... 

The engineering of zinc-binding sites in a-helical peptides, where metal binding stabilizes protein tertiary structure, has been reported by Handel and DeGrado (1990). In these experiments zinc-binding sites are incorporated into a dimeric helix-loop—helix peptide (H3 2) and a protein composed of four helices connected by three short loop sequences (H3 4). a model of one subunit of the H3 2 dimer is found in Fig. 47. In addition to metal complexation by two histidine residues at positions n and n+4 of one a helix, the metal is coordinated by a third histidine residue of an adjacent a helix. The composition of the zinc coordination polyhedron is like that of carbonic anhydrase (i.e., Hiss), and spectroscopic results suggest that all three histidine residues are involved in zinc complexation. This work sets an important foundation... 

Some model Zn2+ complexes of the ethanol-pendant [12]aneN3 (34i) and ethanol-pendant cyclen (228) were reported. The former formed a dimeric alkoxide complex, while the latter (pifa 7.6) yielded a mononuclear hydroxide species. Some model Zn2+ complexes of carboxy-methyl and carboxyethyl and carboxypropyl pendant cyclen were prepared. All these zinc complexes exist in equilibrium between the CO2-bound and CO2 -unbound forms in acidic aqueous solution. Herr et al. (229) synthesized some zinc(II) complexes with tripodal peptide ligands with histidine side chains to mimic the zinc(II)-coordination sphere of CA. 

The study of these peptides and their copper and zinc complexes by mass spectrometry revealed much information about their composition and binding characteristics. The most interesting results were those from the study of patellamide C and its copper complexes. This revealed the formation of complexes, such as [PatCH2 + 2Cu + (CsHsOs)] which were not detected by CD. This species might be similar to the copper complex of ascidiacyclamide, which was shown by X-ray crystallography to have a bridging carbonate between the two copper atoms. ... 

Binuclear zinc complexes have been shown to mediate the hydrolysis of the activated peptide model substrate L-leucine- -nitroanilide (LNA, Fig. 32) with the reactions being followed spectroscopically by the formation of /7-nitroaniline ( max 400 nm).165-167 This model substrate has also been used in studies of ApAP.170 The hydrolysis of LNA mediated by the zinc complex [(bomp-)]Zn2(CH3C02)2]BPh4 (Fig. 33a H(bomp) 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol) in water/DMF (6 4) occurs via a reaction that is first-order in complex and substrate, with a second-order rate constant k = 2.3(1) x 10 3M 1 s-1 at 25 °C. At best, a yield of 65% for a single turnover reaction was obtained, indicating that... 

Outside the scope of coverage of this contribution are studies of zinc complexes having peptide-based ligands260 262 and Zn(II)-complex-promoted reactions involving RNA or DNA hydrolysis.261 263 288... 

The peptides cystein and methionine contain sulfur in their side groups. Sulfides bind easily to metal ions, such as Fe U Cu +, Zn +, and Pb ". In the case of Fe, Fe-S complexes are formed, which are capable of easy reduction or oxidation. Pb + is poisonous and binds strongly at Zn + sites, but the structure is very different from the tetrahedral zinc complex. 

The zinc enolate formed as an intermediate in these conjugate addition reactions can be trapped by an electrophile in situ to provide further functionalization of the substrate. This is demonstrated by the synthesis of the anticancer agent clavularin B (eq 103). Sequential conjugate addition to cycloheptenone of Me2Zn in the presence of catalytic CuOTf-chiral peptide ligand complex, and enolate alkylation with 4-iodo-1-butene provide the key compound with 97% ee. 

Lehmann, E. Zenobi, R. Detection of specific noncovalent zinc finger peptide-Oligodeoxynucleotide complexes by matrix-assisted laser desorption/ ionization mass spectrometry. Angew. Chem. Int. Ed. Engl. 1998, 38, 3430-3432. 

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