Scanning cysteine

FIGURE 6.1 CVs obtained at cysteine-modified (curves a and b) and bare Au (curve c) electrodes in 25 mM phosphate buffer in the presence (curves a and c) and absence (curve b) of 0.56 mM Cu, Zn-SOD. Potential scan rate, lOOmV s-1. (Reprinted from [98], with permission from Elsevier.)... 

Similar to those observed with the cysteine-modified electrode in Cu, Zn-SOD solution [98], CVs obtained at the MPA-modified Au electrode in phosphate buffer containing Fe-SOD or Mn-SOD at different potential scan rates (v) clearly show that the peak currents obtained for each SOD are linear with v (not v 1/2) over the potential scan range from 10 to 1000 mVs-1. This observation reveals that the electron transfer of the SODs is a surface-confined process and not a diffusion-controlled one. The previously observed cysteine-promoted surface-confined electron transfer process of Cu, Zn-SOD has been primarily elucidated based on the formation of a cysteine-bridged SOD-electrode complex oriented at an electrode-solution interface, which is expected to sufficiently facilitate a direct electron transfer between the metal active site in SOD and Au electrodes. Such a model appears to be also suitable for the SODs (i.e. Cu, Zn-SOD, Fe-SOD, and Mn-SOD) with MPA promoter. The so-called... 

FIGURE 6.7 CVs obtained at (a, b) Cu,Zn-SOD/cysteine-modified, (c) bare, and (d) cysteine-modified Au electrodes in 25 mM PBS (pH 7.4) saturated by N2 (a, c, d) or 02 (b). Solutions (b) and (c) contain 0.002U ml-1 XOD and 25mM xanthine. Potential scan rate, lOOmV s. (Reprinted from [150], with permission from the Royal Society of Chemistry.)... 

Zarbiv, R., Grunewald, M Kavanaugh, M. P., and Kanner, B. I. (1998) Cysteine scanning of the surroundings of an alkali-ion binding site of the glutamate transporter GLT-1 reveals a conformationally sensitive residue. J. Biol. Chem. 273,14231-14237. 

A related fibril model for A/ o was proposed based on scanning proline mutagenesis (Williams et al, 2004) and molecular modeling (Guo et al., 2004). This model proposes that residues 15-21, 24-28, and 31-36 form 3 /-strands, with 2 intervening turns formed by residues 22-23 and 29-30 (Fig. 17G). Residues 17 and 34 are placed in close proximity, as double cysteine mutants at these positions form disulfide bonds on oxidation after fibrillization (Shivaprasad and Wetzel, 2004). Since fibrils with this triangular cross section would not be expected to show an H0-A... 

Loo, T.W. and Clarke, D.M. (1999) Determining the structure and mechanism of the human multidrug resistance P-glycoprotein using cysteine-scanning mutagenesis and thiol-modification techniques. Biochimica et Biophysica Acta, 1461, 315-325. 

Fig. 9. Precursor ion scan on an electrospray triple quadrupole mass spectrometer. From all the peptides present of the digested protein only those that are phosphorylated are detected in a precursor ion scan for the phosphate ion (P03, mass 79 Da) in negative ion mode. From the TPX protein three phosphorylated peptides could be detected Ml, AQLTM PSTPTVLK M2, LSETSVNTEQNSK and M3, VQPVQTTPSKDDVSNSATHVC DVK. M, Oxidized methionine C, carbamidomethylated cysteine.

Amino acids enhance the oxidation peak of Cu(0) obtained with a carbon paste electrode incorporating Cu(II) cyclohexylbutyrate. The increased current is proportional to the amino acid concentration at trace levels in the pM range373. The behavior of such electrodes was investigated for cysteine (115). On scanning potentials in the positive direction, the amino acid is accumulated on the electrode as the Cu(I) complex at +0.90 V vs a standard calomel electrode (SCE), in acetate buffer at pH 4.5 linear range is 2 x 10 9 to 1 x 10-7 M, 1 min accumulation, RSD 3% (n = 5)374,375. 

Cysteine Scanning Mutagenesis Mapping Binding Sites of Ligand-Gated Ion Channels... 

Cysteine scanning mutagenesis mapping binding sites of ligand-gated ion channels... 

Bass RB, Falke JJ. 1998. Detection of a converved a-helix in the kinase-docking region of the aspartate receptor by cysteine and disulfide scanning. J Biol Chem 273 ... 

Danielson MA, Bass RB, Falke JJ. 1997. Cysteine and disulfide scanning reveals a regulatory a-helix in the cytoplasmic domain of the aspartate receptor. J Biol Chem 272 32878-32888. 

Sullivan D, Chiara DC, Cohen JB. 2002. Mapping the agonist binding site of the nicotinic acetylcholine receptor by cysteine scanning mutagenesis antagonist footprint and secondary structure predictions. Mol Pharmacol 61 ... 

The aquated iron(III) ion is an oxidant. Reaction with reducing ligands probably proceeds through complexing. Rapid scan spectrophotometry of the Fe(III)-cysteine system shows a transient blue Fe(lII)-cysteine complex and formation of Fe(II) and cystine. The reduction of Fe(lII) by hydroquinone, in concentrated solution has been probed by stopped-flow linked to x-ray absorption spectrometry. The changing charge on the iron is thereby assessed. In the reaction of Fe(III) with a number of reducing transition metal ions M in acid, the rate law... 

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