Mixed-metal proteins

As the first step, a Ni(II) metal complex of HPMA copolymer was formed and purified [35]. It was then mixed with protein solutions to form dried films, which were rehydrated to investigate the swelling profile and stimuli sensitivity. 

Protein-protein interactions usually occur on the surface of proteins where mainly loops or turns are present [24], It is, therefore, of interest to stabilize specific peptide turns and test them for their biological activity [25-28], As discussed, metal coordination seems to be a powerful tool for obtaining macrocycles with a bent peptidic domain simply by mixing metal ions and peptide-bridged ligands. 

Figure 4 A schematic representation of the experimentai approach for time-resoived XAS measurements. XAS provides local structural and electronic information about the nearest coordination environment surrounding the catalytic metal ion within the active site of a metalloprotein in solution. Spectral analysis of the various spectral regions yields complementary electronic and structural information, which allows the determination of the oxidation state of the X-ray absorbing metal atom and precise determination of distances between the absorbing metal atom and the protein atoms that surround it. Time-dependent XAS provides insight into the lifetimes and local atomic structures of metal-protein complexes during enzymatic reactions on millisecond to minute time scales, (a) The drawing describes a conventional stopped-flow machine that is used to rapidly mix the reaction components (e.g., enzyme and substrate) and derive kinetic traces as shown in (b). (b) The enzymatic reaction is studied by pre-steady-state kinetic analysis to dissect out the time frame of individual kinetic phases, (c) The stopped-flow apparatus is equipped with a freeze-quench device. Sample aliquots are collected after mixing and rapidly froze into X-ray sample holders by the freeze-quench device, (d) Frozen samples are subjected to X-ray data collection and analysis.

The Tafel equation also describes the evolution of oxygen at a platinum anode. Bockris and Huq found that, with solutions carefully purified by preelectrolysis, the oxygen electrode exhibits reversible behavior (E = 1.24 V, compared with the theoretical 1.23 V). The exchange current density, however, is only of the order of 10" to 10" °A/cm in dilute sulfuric acid so polarization occurs readily, and relatively large overpotentials are observed at moderate current densities. In solutions of ordinary chemical purity the Nemst relation fails for the oxygen electrode because of mixed-potential behavior. Criddle, using platinum electrodes in highly purified 1 M KOH, obtained a rest potential of 1.59 V. The potential is reduced by peroxide, which may be formed with impurities such as metals, protein, or carbon. 

Fluids flow, boil, freeze, and evaporate. Solids melt and deform. Oil and water don t mix. Metals and semiconductors conduct electricity. Crystals grow. Chemicals react and rearrange, take up heat and gi e it off. Rubber stretches and retracts. Proteins catalyze biological reactions. What forces drive these processes This question is addressed by statistical thermodynamics, a set of tools for modeling molecular forces and behavior, and a language for interpreting experiments. 

Transfer from tryptophan residue donors on protein to nanoparticle acceptors The mixed metal, CD4 antibody-5X-aminodextran-(Cd Hg = 1 1)S conjugate prepared ° by a procedure similar to one already reported for the same -CdS conjugate showed an emission spectrum, with 283.2 nm excitation into the CD4 antibody absorption band (Fig. 15), showing (Fig. 16) an intense emission band centered at 339 nm from tryptophan residues of the CD4 antibody and a medium intensity emission band at 660 nm from the mixed (Cd,Hg)S semiconductor nanoparticles. The predominant excitation peak (Fig. 16, top) was at 281.6 nm when emission was monitored at 656 nm. 

Preparations of uteroferrin-like proteins have also been reported with less than two irons bound per molecule . However, present work on the stable mixed-metal (Fe-Zn, Fe-Cu and Fe-Hg) forms of uteroferrin, as well as the isolation of a naturally occurring... 

Mixed-metal, Fe-Zn forms of both uteroferrin and the splenic enzyme possessing full enzymic activity have been prepared . Susceptibility and EPR measurements of the splenic Fe-Zn enzyme indicate that its single iron is high-spin ferric in a state of rhombic symmetry . Its gave = 4.3 signal, which accounts for the protein s full complement of... 

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