Metal heterodimers

LCA toward amino acids and nucleic bases has also been measured. Wesdemiotis and Cerda measured the alkali metal ion affinities of nucleobases in the gas phase from the dissociation of metal ion-bound heterodimers [nucleobase + B]M+, in which B represents a reference base of known affinity and M is an alkali metal. By assessing the dimer decomposition for two different internal energies, entropy is deconvoluted from enthalpy and LCA values are obtained. For guanine, cytosine, adenine, thymine and uracil, the corresponding Li+-nucleobase bond energies are as follows 57.2, 55.5, 54.1,... 

ECB deacylase is a heterodimer consisting of 63-kDa and 18-20-kDa subunits [25], The purified ECB deacylase requires no external cofactor, metal ion, or... 

The membrane-associated ECB deacylase of A. utahensis can be salt-solubilized, heat-treated, and purified to apparent homogeneity by a three-step chromatographic procedure. The deacylase is a heterodimer consisting of 63- and 18-20-kDa subunits. Except for salt stimulation, the deacylase has no external cofactor or metal ion requirement and has broad substrate specificity for the cyclic hexa-... 

Dimer ions such as (M + M + H)+ or of higher order ( M + H)+ are often observed. The proton can be replaced by another cation. Heterodimers of the general formula (M + M + H)+, or with a metal cation or of higher order, are also observed. The corresponding ions are also observed in negative ion mode. 

In vitro, both metals in the active site of SOD can be reversibly removed. This behavior has been elegantly expanded to produce a variety of metal-substituted derivatives. Co, Ni, and Ag derivatives, where the added metal ion may occupy the copper site or the zinc site (and in some cases both), have proven especially valuable in providing new spectroscopic probes of metal-site structure and reactivity in Cu, Zn SOD. Application of in vitro metal substitution to several of the FALS wild-type-like mutants has shown that these variants readily misfold and often exhibit altered metal ion binding. In addition to the in vitro metal studies, recent work has centered on the mechanism of in vivo copper incorporation. CCS is a copper chaperone protein that forms a heterodimer with Zn-loaded SOD to insert copper and activate the enzyme (see Metallochaperones Metal Ion Homeostasis). 

Recent studies indicate that a limited region of GPIIIa (V275GSDNH280) (58) expressed in an extended loop of the metal ion-dependent adhesion site appears to involved in heterodimer assembly. In addition, the expression of isolated residues 1-233 of GPIIb and 111 -318 of GPIIIa leads to the formation of soluble peptide heterodimers that recognize the RGD sequence (58). 

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