6 research outputs found
Modulation of the Conformational Dynamics of Apo-Adenylate Kinase through a π–Cation Interaction
Large-scale
conformational transition from open to closed state
of adenylate kinase (ADK) is essential for its catalytic cycle. Apo-ADK
undergoes conformational transition in a way that closely resembles
an open-to-closed conformational transition. Here, equilibrium simulations,
free-energy simulations, and quantum mechanics/molecular mechanics
(QM/MM) calculations in combination with several bioinformatics approaches
have been used to explore the molecular origin of this conformational
transition in apo-ADK. In addition to its conventional open state, Escherichia coli apo-ADK adopts conformations that
resemble a closed-like intermediate, the “half-open-half-closed”
(HOHC) state, and a π–cation interaction can account
for the stability of this HOHC state. Energetics and the electronic
properties of this π–cation interaction have been explored
using QM/MM calculations. Upon rescinding the π–cation
interaction, the conformational landscape of the apo-ADK changes completely.
The apo-ADK population is shifted completely toward the open state.
This π–cation interaction is highly conserved in bacterial
ADK; the cationic guanidinium moiety of a conserved ARG interacts
with the delocalized π-electron cloud of either PHE or TYR.
Interestingly, this study demonstrates the modulation of a principal
protein dynamics by a conserved specific π–cation interaction
across different organisms
Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5‑(<i>tert</i>-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5‑<i>t</i>BHI)
5-(tert-Butyl)-2-hydroxy-1,3-isophthalaldehyde
(5-tBHI) is a photochromic material susceptible to
either excited state proton transfer or excited state intramolecular
proton transfer, depending upon the solvent. However, it has also
been found to aggregate in the presence of sodium dodecyl sulfate.
In this current study, based on the steady-state and time-resolved
spectroscopy, supported by crystallography, quantum chemical density
functional theory calculation, and molecular dynamics (MD) simulation,
we report on the aggregation of this potential single benzene-based
emitter (SBBE) in neat solvents as well as solid phase to modulate
its photophysics. It has been found that 5-tBHI forms
mixed aggregates of different orders, owing to the presence of both
enolic and tautomeric forms, to yield tunable emission, although the
emission intensity is quenched. These findings suggest that the intramolecular
hydrogen bonding of 5-tBHI not only limits intermolecular
interactions but also promotes nonradiative deactivation pathways.
Hence, designing and structural engineering, with a focus to suppressing
intramolecular hydrogen bonding as well as increasing through space
conjugation by replacing the aldehydic moieties with bulky aliphatic
or aromatic ketonic groups, can be a plausible approach to yielding
improved probes with tunable emission and higher fluorescence quantum
yields
Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5‑(<i>tert</i>-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5‑<i>t</i>BHI)
5-(tert-Butyl)-2-hydroxy-1,3-isophthalaldehyde
(5-tBHI) is a photochromic material susceptible to
either excited state proton transfer or excited state intramolecular
proton transfer, depending upon the solvent. However, it has also
been found to aggregate in the presence of sodium dodecyl sulfate.
In this current study, based on the steady-state and time-resolved
spectroscopy, supported by crystallography, quantum chemical density
functional theory calculation, and molecular dynamics (MD) simulation,
we report on the aggregation of this potential single benzene-based
emitter (SBBE) in neat solvents as well as solid phase to modulate
its photophysics. It has been found that 5-tBHI forms
mixed aggregates of different orders, owing to the presence of both
enolic and tautomeric forms, to yield tunable emission, although the
emission intensity is quenched. These findings suggest that the intramolecular
hydrogen bonding of 5-tBHI not only limits intermolecular
interactions but also promotes nonradiative deactivation pathways.
Hence, designing and structural engineering, with a focus to suppressing
intramolecular hydrogen bonding as well as increasing through space
conjugation by replacing the aldehydic moieties with bulky aliphatic
or aromatic ketonic groups, can be a plausible approach to yielding
improved probes with tunable emission and higher fluorescence quantum
yields
Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5‑(<i>tert</i>-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5‑<i>t</i>BHI)
5-(tert-Butyl)-2-hydroxy-1,3-isophthalaldehyde
(5-tBHI) is a photochromic material susceptible to
either excited state proton transfer or excited state intramolecular
proton transfer, depending upon the solvent. However, it has also
been found to aggregate in the presence of sodium dodecyl sulfate.
In this current study, based on the steady-state and time-resolved
spectroscopy, supported by crystallography, quantum chemical density
functional theory calculation, and molecular dynamics (MD) simulation,
we report on the aggregation of this potential single benzene-based
emitter (SBBE) in neat solvents as well as solid phase to modulate
its photophysics. It has been found that 5-tBHI forms
mixed aggregates of different orders, owing to the presence of both
enolic and tautomeric forms, to yield tunable emission, although the
emission intensity is quenched. These findings suggest that the intramolecular
hydrogen bonding of 5-tBHI not only limits intermolecular
interactions but also promotes nonradiative deactivation pathways.
Hence, designing and structural engineering, with a focus to suppressing
intramolecular hydrogen bonding as well as increasing through space
conjugation by replacing the aldehydic moieties with bulky aliphatic
or aromatic ketonic groups, can be a plausible approach to yielding
improved probes with tunable emission and higher fluorescence quantum
yields
Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5‑(<i>tert</i>-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5‑<i>t</i>BHI)
5-(tert-Butyl)-2-hydroxy-1,3-isophthalaldehyde
(5-tBHI) is a photochromic material susceptible to
either excited state proton transfer or excited state intramolecular
proton transfer, depending upon the solvent. However, it has also
been found to aggregate in the presence of sodium dodecyl sulfate.
In this current study, based on the steady-state and time-resolved
spectroscopy, supported by crystallography, quantum chemical density
functional theory calculation, and molecular dynamics (MD) simulation,
we report on the aggregation of this potential single benzene-based
emitter (SBBE) in neat solvents as well as solid phase to modulate
its photophysics. It has been found that 5-tBHI forms
mixed aggregates of different orders, owing to the presence of both
enolic and tautomeric forms, to yield tunable emission, although the
emission intensity is quenched. These findings suggest that the intramolecular
hydrogen bonding of 5-tBHI not only limits intermolecular
interactions but also promotes nonradiative deactivation pathways.
Hence, designing and structural engineering, with a focus to suppressing
intramolecular hydrogen bonding as well as increasing through space
conjugation by replacing the aldehydic moieties with bulky aliphatic
or aromatic ketonic groups, can be a plausible approach to yielding
improved probes with tunable emission and higher fluorescence quantum
yields
Role of Dispersive Fluorous Interaction in the Solvation Dynamics of the Perfluoro Group Containing Molecules
Perfluoro
group containing molecules possess an important self-aggregation property
through the fluorous (F···F) interaction which makes
them useful for diverse applications such as medicinal chemistry,
separation techniques, polymer technology, and biology. In this article,
we have investigated the solvation dynamics of coumarin-153 (C153)
and coumarin-6H (C6H) in ethanol (ETH), 2-fluoroethanol (MFE), and
2,2,2-trifluoroethanol (TFE) using the femtosecond upconversion technique
and molecular dynamics (MD) simulation to understand the role of fluorous
interaction between the solute and solvent molecules in the solvation
dynamics of perfluoro group containing molecules. The femtosecond
upconversion data show that the time scales of solvation dynamics
of C6H in ETH, MFE, and TFE are approximately the same whereas the
solvation dynamics of C153 in TFE is slow as compared to that of ETH
and MFE. It has also been observed that the time scale of solvation
dynamics of C6H in ETH and MFE is higher than that of C153 in the
same solvents. MD simulation results show a qualitative agreement
with the experimental data in terms of the time scale of the slow
components of the solvation for all the systems. The experimental
and simulation studies combined lead to the conclusion that the solvation
dynamics of C6H in all solvents as well as C153 in ETH and MFE is
mostly governed by the charge distribution of ester moieties (Cî—»O
and O) of dye molecules whereas the solvation of C153 in TFE is predominantly
due to the dispersive fluorous interaction (F···F)
between the perfluoro groups of the C153 and solvent molecules