Nickel histidine complexes

Toxic and carcinogenic effects of nickel compounds are associated with nickel-mediated oxidative damage to DNA and proteins and to inhibition of cellular antioxidant defenses. Most authorities agree that albumin is the main transport protein for nickel in humans and animals and that nickel is also found in nickeloplasmin - a nickel-containing alpha-macroglobulin - and in an ultrafilterable semm fraction similar to a nickel-histidine complex. Normal routes of nickel intake for humans and animals are ingestion, inhalation, and... 

More detailed studies of reactions of this type have been reported.96,97 Nickel(II) complexes of histidine and tryptophan provide stereoselectivity in the hydrolysis of histidine methyl ester, but stereoselectivity is not observed with nickel(Il) complexes of aspartic acid or methionine. Only tridentate ligands with a minimum steric bulk appear to be capable of exhibiting stereoselectivity in reactions of this type. 

Treatment with the nickel(II) complex of the tripeptide glycine-glycine-histidine in the presence of magnesium monoperoxyphthalate Visible light irradiation in the presence of tris(bipyridyl)ruthenium(II) dication and ammonium persulfate Ethylmercury phosphate Fluorescein... 

Inoue S, Kawanishi S (1989) ESR evidence for superoxide, hydroxyl radicals and singlet oxygen produced from hydrogen peroxide and nickel(II) complex of glycylglycyl-L-histidine. Biochem Biophys Res Commum 159 445-451 Inoue S, Yamamoto K, Kawanishi S (1990) DNA damage induced by metabolites of o-phenylphenol in the presence of copper(II) ion. Chem Res Toxicol 3 144-149... 

Derived from the German word meaning devil s copper, nickel is found predominantly in two isotopic forms, Ni (68% natural abundance) and Ni (26%). Ni exists in four oxidation states, 0, I, II, III, and IV. Ni(II), which is the most common oxidation state, has an ionic radius of —65 pm in the four-coordinate state and —80 pm in the octahedral low-spin state. The Ni(II) aqua cation exhibits a pAa of 9.9. It forms tight complexes with histidine (log Af = 15.9) and, among the first-row transition metals, is second only to Cu(II) in its ability to complex with acidic amino acids (log K( = 6-7 (7). Although Ni(II) is most common, the paramagnetic Ni(I) and Ni(III) states are also attainable. Ni(I), a (P metal, can exist only in the S = state, whereas Ni(lll), a cT ion, can be either S = or S =. ... 

The advantage of such co-purification protocols is that the fully processed protein serving as the bait can allow interactions in a native environment and cellular location to allow isolation of multicomponent complexes. One limitation with this approach is the necessity for an antibody with specific immunoreactivity and immunoprecipitative capability for the bait protein. This drawback can be addressed by expression of the protein with an epitope tag. Excellent antibodies to a variety of epitope tags are available and can be utilized for immunoaffinity purification. Tags such as 6-histidine and GST allow purification using affinity characteristics to nickel and GSH beads, respectively. 

Among protein aromatic groups, histidyl residues are the most metal reactive, followed by tryptophan, tyrosine, and phenylalanine.1 Copper is the most reactive metal, followed in order by nickel, cobalt, and zinc. These interactions are typically strongest in the pH range of 7.5 to 8.5, coincident with the titration of histidine. Because histidine is essentially uncharged at alkaline pH, complex-ation makes affected proteins more electropositive. Because of the alkaline optima for these interactions, their effects are most often observed on anion exchangers, where complexed forms tend to be retained more weakly than native protein. The effect may be substantial or it may be small, but even small differences may erode resolution enough to limit the usefulness of an assay. 

Brydon and Roberts- added hemolyzed blood to unhemolyzed plasma, analyzed the specimens for a variety of constituents and then compared the values with those in the unhemolyzed plasma (B28). The following procedures were considered unaffected by hemolysis (up to 1 g/100 ml hemoglobin) urea (diacetyl monoxime) carbon dioxide content (phe-nolphthalein complex) iron binding capacity cholesterol (ferric chloride) creatinine (alkaline picrate) uric acid (phosphotungstate reduction) alkaline phosphatase (4-nitrophenyl phosphate) 5 -nucleotidase (adenosine monophosphate-nickel) and tartrate-labile acid phosphatase (phenyl phosphate). In Table 2 are shown those assays where increases were observed. The hemolysis used in these studies was equivalent to that produced by the breakdown of about 15 X 10 erythrocytes. In the bromocresol green albumin method it has been reported that for every 100 mg of hemoglobin/100 ml serum, the apparent albumin concentration is increased by 100 mg/100 ml (D12). Hemolysis releases some amino acids, such as histidine, into the plasma (Alb). 

In human serum, nickel binds to albumin, L-histidine, and 2 i croglobulin (Sarkar 1984). The principal binding locus of nickel to serum albumin is the histidine residue at the third position from the amino terminus (Hendel and Sunderman 1972). A proposed transport model involves the removal of nickel from albumin to histidine via a ternary complex composed of albumin, nickel, and L-histidine. 

The low molecular weight L-histidine nickel complex can cross biological membranes (Sarkar 1984). How nickel gets inside of cells may determine the effects of the nickel compounds. If nickel ions are taken into the cytosol and bind to protein, they are not delivered to the nucleus, which prevents the interaction of nickel ions with DNA. Crystalline nickel compounds are phagocytized and nickel ions are delivered to the nucleus where they interact with DNA or DNA protein complexes (Costa 1995). 

The complex was produced in E. coli cells from the cloned genes allowing for some "engineering" of the proteins. A ten-histidine "tag" was added at the N termini of the P subunits so that the complex could be "glued" to a microscope coverslip coated with a nickel complex with a high affinity for the His tags. The y subunit shafts protrude upward as shown in Fig. 18-16. The y subunit was mutated to replace its... 

The possibility of using surface modification of cheap metals to make them effective electrode materials has been mentioned (Section 57.3.2.3(1)). A further example employs cyanoferrates and cyanoruthenates as the redox centres.76 Complexes such as [M(CN)5L]" (M = Fe, Ru L = CN, H20, NO, L-histidine) may be immobilized on a partially corroded nickel surface. The surfaces have good stability and diffuse reflectance IR spectroscopy shows the presence of bridging cyano groups, implying the presence of a binuclear (Ni, M) species in the surface. A general equation for the redox reaction is ... 

Bivalent zinc, cadmium, nickel, and copper have been found to form ternary mixed-ligand complexes with histidine or edta and polyphenols.268 The formation constants for the ternary complexes are less than those for the binary systems. 

EXAFS studies (Hasnain and Piggott, 1983 Alagna et al., 1984) have shown that the spectrum of urease is similar to those of benzimidazole complexes (Fig. 5-2) suggesting that the nickel is coordinated by histidine nitrogen and oxygen ligands. 

Most biocatalytic conversions are performed with the enzyme immobilized in the microreactor. Miyazaki et al. [426] developed a simple noncovalent immobilization method for His-tagged enzymes on a microchannel surface. These enzymes contain a polyhistidine-tag motif that consists of at least six histidine residues, often located at the N- or C-terminus. The H is-tag has a strong affinity for nickel and can be reversibly immobilized by a nickel-nitrilotriacetic acid (Ni-NTA) complex (Scheme 4.103), a strategy commonly used in affinity chromatography. 

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