PROTEIN-AQUA

AquaPAC LV. See Polyanionic cellulose Aquapac . See Polyaluminum chloride AquaPAC . See Polyanionic cellulose Aquapalm No. 63841. See Retinyl palmitate Aqua Poly 225. See Polyethylene wax Aqua Poly 250, Aqua Polyfluo 411] Aqua Polysilk 19. See Synthetic wax Aqua Pro IIBG. See p-Glucan Aqua Pro II OP. See Hydrolyzed oat protein Aqua Pro IIQSL. See Laurdimonium hydroxypropyl hydrolyzed soy protein Aqua Pro IIQST. See Hydroxypropyltrimonium hydrolyzed soy protein... 

Aqua Pro IIQWC. See Cocodimonium hydroxypropyl hydrolyzed wheat protein Aqua Pro IIQWL. See Laurdimonium hydroxypropyl hydrolyzed wheat protein Aqua Pro IIQWS. See Steardimonium hydroxypropyl hydrolyzed wheat protein Aqua Pro IIRB. See Rice (Oryza sativa) bran Aqua Pro IIRP. See Hydrolyzed rice protein Aqua Pro IISP. See Hydrolyzed soy protein Aqua Pro II VP. See Hydrolyzed vegetable protein... 

RA Laskowski, JAC Rullmann, MW MacArthur, R Kaptem, JM Thornton. AQUA and PRO-CHECK-NMR Programs for checking the quality of protein stiaictures solved by NMR. J Biomol NMR 8 477-486, 1996. 

Selective cleavage of peptides and proteins is an important procedure in biochemistry and molecular biology. The half-life for the uncatalyzed hydrolysis of amide bonds is 350 500 years at room temperature and pH 4 8. Clearly, efficient methods of cleavage are needed. Despite their great catalytic power and selectivity to sequence, proteinases have some disadvantages. Peptides 420,423,424,426 an(j proteins428 429 can be hydrolytically cleaved near histidine and methionine residues with several palladium(II) aqua complexes, often with catalytic turnover. 

Fig. 13 CORCEMA-ST optimized structure of bovine DHFR/TMP complex. Protein residues within the binding pocket are aqua blue and ligand residues light purple. The hydrogens were omitted for clarity. Reprinted with permission from [75] 2005, American Chemical Society...

Water NMRD profiles acquired for other complexes and proteins always exhibit the same features of hexaaqua nickel(II). As an example, we report here the profile of the hexa-coordinate nickel(II)-substituted bovine carbonic anhydrase II 54,55) (Fig. 15). As in the aqua complex, (i) the low-field profile is flat, (ii) no dispersion appears, the cOg dispersion being quenched in S = 1 complexes with large static ZFS 56) (see Section I.A.5) and the... 

At variance with the aqua ion, in most manganese(II) proteins and complexes the contact contribution to relaxation is found negligible. This is clearly the case for MnEDTA (Fig. 33), the relaxivity of which indicates the presence of the dipolar contribution only, and one water molecule bound to the complex 93). Actually the profile is very similar to that of GdDTPA (see Chapter 4), and is provided by the sum of inner-sphere and outer-sphere contributions of the same order. The relaxation rate of MnDTPA is accounted for by outer-sphere relaxation only (see Section II.A.7), no water molecules being coordinated to the complex 94). 

ApoSOD, 45 186, 190 Apo VFe protein, 47 204 APS reductase, see Adenylylsulfate reductase Aqua-bridged hydroxo complexes acid-base equilibria, 32 110 of dihydroxo-bridged species, 32 114-115... 

The most elegant example which demonstrates this aspect of proton transfer equilibrium of heme proteins is the study reported on six coordinated aqua (pyridine) iron(III) porphyrin complexes encapsulated in aqueous micelles [27]. The ferric ion in these complexes is axially co-ordinated to a water and a pyridine molecule, thus having a coordination geometry similar to that of the heme in metmyoglobin. The pH dependence of the absorption spectra of the... 

A family of integral proteins discovered by Peter Agre, the aquaporins (AQPs), provide channels for rapid movement of water molecules across all plasma membranes (Table 11-6 lists a few examples). Ten aquaporins are known in humans, each with its specialized role. Erythrocytes, which swell or shrink rapidly in response to abrupt changes in extracellular os-molarity as blood travels through the renal medulla, have a high density of aqua-porin in their plasma membranes (2 X 105 copies of AQP-1 per cell). In the nephron (the functional unit of the kidney), the plasma membranes of proximal renal tubule cells have five different aquaporin types. 

In blood plasma, the chloride ion concentration is sufficiently large (about 100 mAf) to prevent cis-Pt hydrolysis, and the neutral platinum species most likely crosses the cell membrane. Inside the cell the chloride ion concentration is much lower (about 4mM), which allows for hydrolysis (35, 37). Because water is a far better leaving group than chloride or hydroxide (38, 39), the aqua species are most likely the reactive form of cis-Pt in vivo. Thus hydrolysis is the rate-limiting step in the reaction of cis-Pt with biomolecules such as proteins, RNA, and DNA (40). 

It increases the water permeability of the kidney collecting duct cells by inducing translocation of aqua-porin proteins from intracellular storage vesicles into the apical plasma membrane.78 Vasopressin binds to... 

In a number of cases, a common pattern for catalytic activity seems to be developing, where the zinc centre, already four-coordinate with three protein ligands and an aqua group, binds the substrate to give a five-coordinate complex. The zinc-bound aqua group is ionized to give hydroxide, which participates in the catalytic reaction. Changes in coordination number of the zinc from four to five and back to four appear to be a common feature of zinc metalloenzymes. 

Some small peptide-heme complexes have been prepared, including an undecapeptide (residues 11-21)668"669 and an octapeptide (residues 14-21). TTiese are useful models as they include the two cysteine residues that covalently link the heme to the peptide, and one of the axial ligands. The axial Met-80 residue is absent, but the position can be filled by methionine or by other ligands as required.670 Work with several octapeptide complexes shows that the rates of outer-sphere electron transfer appear to be independent of the axial ligand, and faster than the reaction for cytochrome c. Other comparisons show that the orientation of the axial methionine in cytochrome c and the contacts between heme and protein are important controlling factors in the electronic structure of the heme. Aqua and hydroxo complexes of iron(III) octapeptide complexes are also useful models for studying spin equilibria in iron(III) hemoproteins.671... 

The electron relaxation time is always found to be field independent, and has values in the 10-8-10-9 s range, i.e. one order of magnitude longer than the aqua ion (Table 5.6). Electron relaxation can occur through modulation of g and A anisotropy, which is rr dependent, or through the interaction with collective motions in the case of proteins. 

Although the low field profile is flat, a sharp rise occurs at high field. The absence of the large with respect to the Zeeman splitting. As in the aqua complex, the increase in relaxivity is due to the field dependence of the electron relaxation. As for other metal ions, the correlation time, r , for the modulation of the ZFS in proteins is longer than that in the aquaion. 

Benga G. Birth of water channel proteins—the aqua-porins. Cell Biol Int. 2003 27 701-709. 

DE, two-dimensional gel electrophoresis WB, Western blot MS, mass spectrometry LC, liquid chromatography 2DE DICE, two-dimensional difference gel electrophoresis, SRM, selected-reaction monitoring MRM, multiple reaction monitoring AQUA, absolute protein quantitation SMIM, selected MS/MS ion monitoring. ... 

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