The backbone dynamics of the full length and the N-domain of geobacillus stearothermophillus phosphoglycerate kinase (gsPGK) have been characterised using 15N relaxation and relaxation dispersion measurements. The V I42C mutation of NPGK induced unexpected decrease in the denaturant dependence of the free energy between the folded and unfolded states (m-values) (Cliff, et al.. 2006). This decrease in m-values of the V142C NPGK cannot be ascribed to a change in the backbone dynamics. Backbone conformational dynamics in the free and bound forms of gsPGK were recorded. Comparison of the fast time scale dynamics (pico-nanosecond) of the free and the bound (ADP complexes) forms of gsPGK show a significant increase in the backbone dynamics upon the ADP binding. This increase in dynamics is global. The increase in dynamics caused by ADP binding is reversed by the formation of transition state analogue (TSA) complex. These results are interpreted in the context of the structural tightening hypothesis, which predicts shorter, less dynamic, hydrogen bonding in TS-bound states compared to substrate-bound states of enzymes. In particular, the recorded changes in dynamics of the ADP binding site residues of gsPGK and their hydrogen bond network show a strong correlation with the changes in amide proton shifts, which are strongly affected by hydrogen bond length. Relaxation dispersion experiments detect slow (millisecond) timescale dynamics and conformational exchange in the ADP and 3-phosphoglycerate (3PG) complexes of gsPGK. The induced chemical shifts changes associated with ms dynamics in the ADP complex do not correlate with the amide nitrogen shifts changes between the ground states of the ADP and TSA complexes, which indicates that the conformational exchange rate does not reflect the complete opening and closing process of gsPGK. These studies have provided a reasonably complete picture of how gsPGK responds to structural and dynamics changes during its catalytic cycle.

Liposomes vesicles have drawn attention of researchers as carriers of various drugs that could be used for therapeutic applications. In the present work liposomes were prepared from a mixture of egg yolk L-α-phosphatidylcholine,, 3-sn- phosphatidylcholine from soybeans (as commercial substance) and 1.2-dipalmitoiyle-sn-1-phosphatidylcholine (DPPC) (as a photosensitive substance) and cholesterol in a ratio of 1: 3: 2: 1.2 respectively. Liposomes loaded with Methotrexate (MTX) as a model drug. Effect of 30, 60, and 80 joules/ml of laser 650 nm irradiation on the drug release of MTX, phase transition Tc size distribution, dielectric properties and molecular stability of the prepared liposomes were studied pre and post irradiation with laser. The results indicated that, the drug release percentages of the irradiation samples increase in comparison with the control as laser doses increase. The drug release was followed by using spectrofluorometer technique excitation wavelength of 345 nm and emission wavelength of 450 nm measured every 3 hours. The phase transition temperature Tc showed a decrease as the laser dose increase. All studied liposomes have a dielectric dispersion in the frequency range from 0.1 – 10 MHz. Liposomes exposed to different laser doses showed an increase in and decrease in α dielectric decrement ε and slight changes in the relaxation time corresponding to the higher laser dose. FTIR spectra showed that the laser energy did not cause any changes in the chemical stability of the encapsulated drug. It was concluded that, laser irradiation can be powerful technique in order to increase the encapsulated drug release from liposomes in comparison with the control which consequently thus reducing the side effects of the drug and increasing its therapeutic effect.