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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.

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.

Domain III in annexin V exhibits a high conformational flexibility at membrane/water interfaces which may indicate its insignificance in the interaction of the protein with the membrane. This is evident in the weak interaction between domain III and the membrane surface, and this observation agrees with atomic force microscopy results. The conformational dynamics of domain III bound to negatively charged phospholipid vesicles of 1-palmitoyl-2-oleoyl-sn-glycerophosphocholine and 1-palmitoyl-2-oleoyl-sn-glycerophosphoserine or combined with reverse micelles of water/sodium bis(2-ethylhexyl) sulfosuccinate in isooctane.

Both steady-state and time-resolved tryptophan fluorescence spectroscopy were used in investigating the interaction between the immunophilin domain of FKBP59 (FKBP59-I) and a number of immunosuppressant drugs. The highly homologous protein FKBP12's weak fluorescence is shown to due to an atypical hydrogen bond interaction between the indole nitrogen and Phe129 benzene ring. FKBP59-I, located on the external hydrophilic side of the 50-60 beta-sheet, is determined to be responsible for over 95% of the observed fluorescence.