Peptides, coordinated

H+]) s 1 (23). The redox decomposition prevents the observation of additional substitution reactions, but it shows that substitutions of the other three equatorial nickel(III)-peptide coordination sites are sluggish with rate constants generally -3 -1... 

It is well known that a great variety of biomolecules exist where metals and metalloids are bound to proteins and peptides, coordinated by nucleic acids or complexed by polysaccharides and small organic ligands such as organic acids.55 Most proteins contain amino acids with covalently bonded heteroelements such as sulphur, selenium, phosphorus or iodine.51 Several reviews have been published on the development of mass spectrometric techniques for bioanalysis in metal-lomics , which integrate work on metalloproteins, metalloenzymes and other metal containing biomolecules.1 51 53 54 56-59 The authors consider trace metals, metalloids, P and S (so-called... 

Recently, aconitase has been proposed to have a unique Fe4S42 + core at the active site, as shown in Fig. 17 (57). The cluster consists of one reactive Fe ion in one corner of the cubane cluster and three inert Fe ions occupying the three other corners (42). The heterogeneity of the Fe4S42+ core may be caused by the unusual peptide coordination. 

Kremer, C., Torres, J., Dominguezb, S., and Mederos, A. (2005) Structure and thermodynamic stability of lanthanide complexes with amino acids and peptides. Coordination Chemistry Reviews, 249, 567-590. 

To demonstrate how powerful this method is, Gilbertson and Wang synthesized libraries of phosphines containing peptides, coordinated them to rhodium, and tested the corresponding precursors in asymmetric hydrogenation of enamides [76]. Although the enantiomeric excesses are still moderate (35-40%) the best solvent is water and this approach has proved its viability. 

Examples of amino acid and peptide coordination to a metal ion. Deprotonation of carboxylic acid and amide groups is required for efficient coordination potential donor groups are highlighted in the free hgands. 

The free energy differences obtained from our constrained simulations refer to strictly specified states, defined by single points in the 14-dimensional dihedral space. Standard concepts of a molecular conformation include some region, or volume in that space, explored by thermal fluctuations around a transient equilibrium structure. To obtain the free energy differences between conformers of the unconstrained peptide, a correction for the thermodynamic state is needed. The volume of explored conformational space may be estimated from the covariance matrix of the coordinates of interest, = ((Ci [13, lOj. For each of the four selected conform-... 

Some of the other features of this program are the ability to compute transition states, coordinate driving, conformation searches, combinatorial tools, and built-in visualization. The builder includes atoms and fragments for organics, inorganics, peptides, nucleotides, chelates, high-coordination geometries, and... 

FIGURE 27 19 Proposed mechanism of hydrolysis of a peptide catalyzed by carboxypeptidase A The peptide is bound at the active site by an ionic bond between its C terminal ammo acid and the positively charged side chain of arginine 145 Coordination of Zn to oxygen makes the carbon of the carbonyl group more positive and increases the rate of nucleophilic attack by water... 

Figure 8 A joint principal coordinate projection of the occupied regions in the conformational spaces of linear (Ala) (triangles) and its conformational constraint counterpart, cyclic-CAla) (squares), onto the optimal 3D principal axes. The symbols indicate the projected conformations, and the ellipsoids engulf the volume occupied by the projected points. This projection shows that the conformational volume accessible to the cyclic analog is only a small subset of the conformational volume accessible to the linear peptide, (Adapted from Ref. 41.)...

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