No abstract

Solvation dynamics in the molten globule state of a protein, glutaminyl-tRNA synthetase (GlnRS), has been studied using both a noncovalent probe (bis-ANS) and a covalent probe 4-(N-thioacetylamino)-phthalimide. In the native state of GlnRS, bis-ANS exhibits an average solvation time (〈τ S 〉) of 1400 ps, which is 12 times longer than that for the covalent probe (120 ps). The difference in the solvation times for the two probes in the native state of the protein is ascribed to different locations of the probes. The covalent probe resides close to the protein surface and experiences fast relaxation of the water molecules. The noncovalent probe penetrates deeper inside the protein and displays slower relaxation in the buried region. In the molten globule state, 〈τ S 〉 is 400 ps for the noncovalent probe and 250 ps for the covalent probe. Evidently, in the molten globule state, 〈τ S 〉 is much longer than that the longest component of the solvation dynamics (∼1 ps) in bulk water. This shows that, in the compact molten globule state, the protein retains considerable residual structure.

No abstract

Solvation dynamics of coumarin 480 (C480) is studied in a sol−gel matrix containing dimyristoyl-phosphatidylcholine (DMPC). In the presence of DMPC, the average solvation time (〈τs〉) in the sol−gel glass is found to be 500 ps. This indicates that in the sol−gel matrix solvation dynamics in the presence of DMPC is slower than that in its absence. The solvation dynamics of C480 in the DMPC entrapped TEOS sol−gel matrix is much faster than that in DMPC liposomes in bulk water. This suggests that the DMPC entrapped TEOS sol−gel matrix is very different from DMPC liposomes in bulk water. The rotational relaxation of C480 is found to be very fast giving rise to a very small initial anisotropy value (r 0 = 0.08). This shows that even after incorporation of lipids inside the TEOS sol−gel matrix, the probe C480 remains highly mobile.