Metal ion probes

For different reasons all these physical techniques for studying proteins are most powerful when the protein contains metal atoms. We shall therefore consider metal ion probes and isomorphous replacement in general before turning to individual techniques. 

Martini, G., The state of water adsorbed on silica gel as determined by ESR of transition metal ion probe, J. Colloid Interf. Sci., 80, 39, 1981. 

Coordination, localization and stabilization of transition metal ions in zeolitic materials, apart from activation conditions, depend on the structure and composition of the zeolite matrix. To evaluate the extent of such a matrix effect Cu +ions are used as a metal ion probe in this work, and copper ion-matrix interaction in different zeolites and oxides has been studied by EPR and TPR. ... 

Yam, V.W.-W. Lo, K.K.-W. Cheung, K.-K. Synthesis and crystal structure of a novel copper(l) crown complex A spectrochemical metal ion probe for alkali metal and alkaline earth metal cations. Inorg. Chem. 1995, 34, 4013-4014. 

Choi LS, Mach T, Bayley H (2013) Rates and stoichiometries of metal ion probes of cysteine residues within ion channels. Biophys J 105 356-364... 

A number of quinolone and pyridine materials function as metal ion probes. For example, a fluorescent probe that visualizes zinc in living cells was prepared from a carboxamidoquinoline (13T15). Diaryltrisphaeridines can be fluorescent detectors of copper ion (13T4631).A fluorescent probe uses dihydropyridine derivatives to respond to mercury ions (13T1617). Another zinc-sensitive probe was developed that contains two pyridines and a coumarin ring (13T4743). 

Adsorption amount (Q) of the probes, detection (Lp) and quantification (Lg) limits and range (Dj), response times ((r), stoichiometry of metal ions/probes complex formation (S) and effective pH range used and stability constant (log K,) of the complexes.Adapted with permission from Ref [24] 2006, Wiley-VCH. 

Significant practical objective in analytical chemistry is control on contents of metal ions in various objects including natural. Effective method for practical uses is one of simultaneous determination of content of various metals in object, because it decreases time of analysis, quantity of reagents and probe. 

Substitution-inert metal ions as probes of biological function. J. I. Legg, Coord. Chem. Rev., 1978, 25,103-132 (84). 

Adsorbed CO and NO were used as probes to Investigate the effects of Co concentration and sulfide on the nature and numbers of exposed metal sites on reduced catalysts containing 1 to 6 wt% Co and 8 wt%. Mo on three alumina supports. Exposure of Mo Ions decreased with Increased Co concentration. Exposure of Co Ions typically reached a maximum at 2-4% Co. Sulfide decreased exposure of all metal Ion sites and Increased exposure of reduced metals. Effects of preadsorbed pyridine and 2,6-lutldlne, known poisons, on the exposure of metal sites, plus other evidence. 

IR spectroscopy of adsorbed carbon monoxide has been used extensively to characterize the diluted, reduced Cr/silica system [48-54,60,76,77]. CO is an excellent probe molecule for Cr(ll) sites because its interaction is normally rather strong. The interaction of CO with a transition metal ion can be separated into electrostatic, covalent a-dative, and 7r-back donation contributions. The first two cause a blue shift of the vco (with respect to that of the molecule in the gas phase, 2143 cm ), while the last causes a red shift [83-89]. From a measurement of the vco of a given Cr(II) carbonyl complex, information is thus obtained on the nature of the Cr(II)- CO bond. 

A series of amine-tethered nucleobases such as 8 has also been developed. These ligand systems have allowed the interaction of d-block metal ions with the N3pUrine site to be probed and an indication of base-specific metal-ion binding has begun to emerge (55-58). 

---