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Results demonstrate that the outer membrane receptor of pyoverdine in Pseudomonas aeruginosa is capable of interacting with the pyoverdine. Data indicate that the enzyme-pyoverdin complex adopts atleast two different conformations and exhibit diverse characteristics under in vivo and in vitro conditions.

The solution structure of the N-terminal domain of the calcium sensor calcium vector protein reveals that the domain is largely monomeric and exhibits isotropic Brownian rotational diffusion. The amide backbone groups of the alpha-helices, beta-strands, and the amide groups in calcium-binding loops show restricted but rapid movements.

The dynamics of the ATP binding site of cytidine monophosphate kinase from Escherichaia coli indicate a conformational change of the LID region consequent upon binding by a phosphate donor. Data indicate that this region may wrap around ATP rendering the active site inaccessible to the solvent enabling kinases avoid hydrolysis

The conformation of annexin 2 in both monomeric and heterotetrameric forms changes when calcium binds to the protein. This causes an increase in the major excited-state lifetime and a decrease in flexibility of the W212 tryptophan residue. The flexibility increases when annexin 2 binds to membranes but no further conformational change takes place beyond that induced by calcium.

Research was conducted to examine the effect of pH on the steady-state fluorescence emission spectrum of its single tryptophan residue (Trp187). Circular dichroism calculations provide evidence for a preservation of the native folding of the protein in mild acidic conditions. At high pH of ~11, a fluorescence red-shift of smaller amplitude was also noted. Results indicate that electrostatic interactions may be more essential for the stabilization of domain III folding without the presence of calcium.

Experiments were conducted to measure sodium ion (Na+) concentrations using the fluorescent indicator SBFO. Using global compartmental analysis, the values of four rate constants in excited-state reactions were measured. The global biexponential analyses failed to provide a precise value for fluorescence decay traces of SBFO in the Na+ concentrations. However, estimated rate constant values ranged from 0.465 to 0.127. It was also observed that the excited-state reaction had negligible impact on the fluorimetric estimation of Kd.

Steady-state and time-resolved fluorescence, circular dichroism and ultraviolet (UV)-difference spectroscopy studies indicate the tryptophan 187 in the domain III of annexin V is required for calcium ion binding. Trp 187 exhibits an excited-state reaction that causes hydrogen bond formation in the alpha-carbonyl groups of Thr224. Trp 187 is not seen in crystal structures with high level of calcium ions indicating structural changes that enable the incorporation of the protein on phospholipid membranes.

Site-directed mutagenesis is carried out on FpvA to identify the extracellular loops or parts of these loops involved in the various stages of siderophore pyoverdine-iron (Pvd-Fe) uptake in Pseudomonas aeruginosa. Results suggest that W434, S603 and G701 mutations in loops [L.sub.4], [L.sub.7] and [L.sub.9] respectively are involved on the mechanism of Pvd-Fe intake.

The dynamical behavior of a biomimetic molecule, basket-handle porphyrins (BHP), is studied using several techniques. The results show complimentarity between experiments and theoretical simulations.

The fluorescent dynamic stokes shift method has emphasized a time-dependent dipolar relaxation process around the single tryptophan residue (Trp31) in cytidine monophosphate kinase from E.coli. This Trp residue, located close to the protein surface in a hydrophobic pocket, is weakly accessible to acrylamide, a water-soluble quencher.

Right-handed twisting is a fundamental structural feature of beta-plated sheets in globular proteins, which is critical for their geometry and function. Density functional theory using the B3LYP exchange-correlation functional and the split-valence 6-31G basis set is utilized to examine the structure and conformational transitions of single and double-stranded antiparrallel B-sheet models to determine the driving force for the right-handed twisting.