2 research outputs found
Modulation of Environmental Dynamics at the Active Site and Activity of an Enzyme under Nanoscopic Confinement: Subtilisin Carlsberg in Anionic AOT Reverse Micelle
Hydration
dynamics plays a crucial role in determining the structure, function,
dynamics, and stability of an enzyme. These dynamics involve the trapped-water
motions within small distance along with the total protein dynamics.
However, the exact molecular basis for the induction of enzyme function
by water dynamics is still remain unclear. Here, we have studied both
enzymatic activity and environmental dynamics at the active site of
an enzyme, Subtilisin Carlsberg (SC), under confined environment of
the reverse micelle (RM) retaining the structural integrity of the
protein. Kinetic measurements show that enzymatic activity increases
with increasing the water content of the RM. The picosecond-resolved
fluorescence Stokes shift studies indicate faster hydration dynamics
at the active site of the enzyme with increasing the water content
in the RM (<i>w</i><sub>0</sub> values). Temperature-dependent
hydration dynamics studies demonstrate the increased flexibility of
the protein at higher temperature under confinement. From temperature-dependent
solvation dynamics study, we have also calculated the activation energy
that has to be overcome for full orientational freedom to the water
molecules from bound to free-state. The results presented here establish
a correlation between the enzymatic activity and dynamics of hydration
of the encapsulated protein SC in cell-like confined environment within
the structural integrity of the enzyme
Microstructure, Morphology, and Ultrafast Dynamics of a Novel Edible Microemulsion
An edible microemulsion (ME) composed of Tween 80/butyl
lactate/isopropyl
myristate (IPM)/water has been formulated. Pseudoternary phase diagram
of the system contains a large single isotropic region. The phase
behavior of the system is also studied at low pH (2.6) and in 0.9%
NaCl solution. Conductivity, viscosity, ultrasonic velocity, and compressibility
studies find consistent results in the structural transition (from
water-in-oil (w/o) to bicontinuous, and from bicontinuous to oil-in-water
(o/w)) behavior of the ME. Dynamic light scattering studies reveal
the size of the MEs. The absorption and steady state emission spectra
of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran
(DCM) successfully probe the polarity of the ME at its solvation shell
and shows the efficacy of hosting model drug molecules. The rotational
anisotropy of the dye has been studied to ascertain the geometrical
restriction of the probe molecule. Picosecond-resolved fluorescence
spectroscopy applies well to study the relaxation dynamics of water
in the solvation shell of the MEs. The study finds strong correlation
in the relaxation dynamics of water with the structure of host assembly
and offers an edible ME system which could act as a potential drug
delivery system and nontoxic nanotemplate for other applications