Histidine effect

The ability of an imidazole (24.1.1.1 and 24.4.1) to act as both an acid (A-hydrogen) and a base (the imine nitrogen) is put to good use in the active sites of several enzymes in which the imidazole rings of appropriately placed histidines effectively shuffle protons from one place to another. One example is the... 

Citir M, Hinton CS, Oomens J, Steill JD, Armentrout PB. Infrared multiple photon dissociation spectroscopy of cationized histidine effects of metal cation size on gas-phase conformation. J Phys Chem A. 2012 116 1532-41. 

Type 3 a pair of Cu atoms about 360 pm apart and attaehed to protein through histidine residues these effect O2 transport by means of the... 

Treatment of bovine heart bci complex with ethoxyformic anhydride (EFA), which is known to modify amino acid residues covalently (preferentially histidine residues), inhibits electron transfer and has an effect on the EPR spectra of the Rieske cluster comparable to that observed upon addition of stigmatellin, that is, a decrease in rhombicity (80). This further supports the suggestion that quinones as well as quinonoid inhibitors interact directly with the histidine ligands of the Rieske cluster. 

Two-dimensional protein layer orientation could be also effected by metal-ion coordination Monolayer of iminodiacetate-Cu(II) lipid was successfully employed as substrate for oriented immobilization of proteins naturally displaying histidine residues on their surface [37]. Affmity-resin-displaying Ni(II) complexes could also be successfully employed for oriented protein immobilization [38]. 

In hemoglobin M, histidine F8 (His F8) has been replaced by tyrosine. The iron of HbM forms a tight ionic complex with the phenolate anion of tyrosine that stabilizes the Fc3 form. In a-chain hemoglobin M variants, the R-T equilibrium favors the T state. Oxygen affinity is reduced, and the Bohr effect is absent. P Ghain hemoglobin M variants exhibit R-T switching, and the Bohr effect is therefore present. 

These complexes show considerable in vitro cytotoxic effects against various tumor cell lines [70, 71[. Moreover, the cationic complexes [Au(N,N, N")Cl[Cl are able to intercalate into ct DNA [71[. Gold(III) amidate complexes of histidine containing... 

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