Sanghamitra Deb | Duke University (original) (raw)
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Papers by Sanghamitra Deb
Apart from few early biophysical studies, the relative thermal instability of HbE has been only s... more Apart from few early biophysical studies, the relative thermal instability of HbE has been only shown by clinical investigations. We have compared in vitro thermal stability of HbE with HbA 2 and HbA using optical spectroscopy. From absorption measurements in the soret region, synchronous fluorescence spectroscopy and dynamic light scattering experiments, we have found thermal stability of the three hemoglobin variants following the order HbE<HbA<HbA 2 in terms of structural unfolding and aggregation pattern. We have found formation of intermolecular dityrosine fluorophores with characteristic fluorescence signature, at pH >11.0 in all the three variants. Under oxidative stress conditions in presence of hydrogen peroxide, HbE has been found to be more vulnerable to aggregation compared to HbA and HbA 2 . Taken together, these studies have shown thermal and oxidative instability of HbE and points towards the role of HbE in the upregulation of redox regulators and chaperone proteins in erythrocyte proteome of patients suffering from HbEbeta thalassemia. Citation: Chakrabarti A, Bhattacharya D, Deb S, Chakraborty M (2013) Differential Thermal Stability and Oxidative Vulnerability of the Hemoglobin Variants, HbA 2 and HbE. PLoS ONE 8(11): e81820.
The Journal of Physical Chemistry Letters
Journal of Chemical Physics
Journal of Physical Chemistry A
Annual Review of Physical Chemistry
The journal of physical chemistry. A, 2012
We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO... more We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO and pentoxy radicals. One-color multiphoton ionization with ultrashort laser pulses through the S(2) state resonance gives rise to photoelectron spectra that reflect ionization from the S(1) state. Time-resolved pump-probe photoionization measurements show that upon excitation at 207 nm, the generation of NO in the v = 2 state is delayed, with a rise time of 283 (16) fs. The time-resolved mass spectrum shows the NO to be expelled with a kinetic energy of 1.0 eV, which is consistent with dissociation on the S(1) state potential energy surface. Combined, these observations show that the first step of the dissociation reaction involves an internal conversion from the S(2) to the S(1) state, which is followed by the ejection of the NO radical on the predissociative S(1) state potential energy surface.
The Journal of …, Jan 1, 2010
The photoelectron spectrum shows that multiphoton ionization of amyl nitrite, C(5)H(11)ONO, using... more The photoelectron spectrum shows that multiphoton ionization of amyl nitrite, C(5)H(11)ONO, using ultrafast laser pulses deposits up to 3.7 eV of energy into internal degrees of freedom. As a result, the molecules fragment to produce various daughter ions of masses 87, 71, 60, 57, 41, 30, 29, and 27. Absorption of an additional photon with 3 eV of energy by the ions yields transients with picosecond decay times, revealing the time scale of the decomposition dynamics of the initially prepared parent ion. Each mass peak has a distinct time constant, in the range of 1.2 to 7.9 ps, emphasizing the dependence of the fragmentation mechanism on the ion internal energy.
Journal of Molecular …, Jan 1, 2010
66th International …, Jan 1, 2011
The ultrafast structural dynamics of 1,3-cyclohexadiene has been investigated using structurally ... more The ultrafast structural dynamics of 1,3-cyclohexadiene has been investigated using structurally sensitive Rydberg electron binding energies. Excitation to the 1B state and the 3p Rydberg state yielded different structural responses. In both experiments, the structural dynamics of the molecular core are reflected by time-dependent shifts of the Rydberg electron binding energy. Structural distortions associated with 3p-excitation cause a dynamical shift
• Electron is moving in Coulomb potential created by proton
66th International …, Jan 1, 2011
ABSTRACT The structural response of several tertiary amines to electronic excitation has been inv... more ABSTRACT The structural response of several tertiary amines to electronic excitation has been investigated using Rydberg Fingerprint Spectroscopy. The 3p Rydberg states are reached by excitation with a 5.93 eV photon while 3s states are populated by electronic relaxation from 3p state. We observe binding energy shifts on ultrafast time scales in all peaks that reflect the structural change of the molecular ion cores. The shifts are in the range of 15 meV to 30 meV, within time scales of less than 500 fs, depending on the specific molecular systems and the nature of the electronic state. In cases where the p states are spectrally separate, the trends of the energy shifts are different for the pz and pxy Rydberg states whereas the pz and s states are similar. This suggests that the response of the Rydberg states to structural displacements depends on the symmetry. Very fast binding energy shifts, observed on sup-picosecond time scales, are attributed to the structural adjustment from a pyramidal to a planar structure upon Rydberg excitation. The quantitative values of the binding energy shifts can also be affected by laser chirp, which we model using simulations.
Talks by Sanghamitra Deb
Apart from few early biophysical studies, the relative thermal instability of HbE has been only s... more Apart from few early biophysical studies, the relative thermal instability of HbE has been only shown by clinical investigations. We have compared in vitro thermal stability of HbE with HbA 2 and HbA using optical spectroscopy. From absorption measurements in the soret region, synchronous fluorescence spectroscopy and dynamic light scattering experiments, we have found thermal stability of the three hemoglobin variants following the order HbE<HbA<HbA 2 in terms of structural unfolding and aggregation pattern. We have found formation of intermolecular dityrosine fluorophores with characteristic fluorescence signature, at pH >11.0 in all the three variants. Under oxidative stress conditions in presence of hydrogen peroxide, HbE has been found to be more vulnerable to aggregation compared to HbA and HbA 2 . Taken together, these studies have shown thermal and oxidative instability of HbE and points towards the role of HbE in the upregulation of redox regulators and chaperone proteins in erythrocyte proteome of patients suffering from HbEbeta thalassemia. Citation: Chakrabarti A, Bhattacharya D, Deb S, Chakraborty M (2013) Differential Thermal Stability and Oxidative Vulnerability of the Hemoglobin Variants, HbA 2 and HbE. PLoS ONE 8(11): e81820.
The Journal of Physical Chemistry Letters
Journal of Chemical Physics
Journal of Physical Chemistry A
Annual Review of Physical Chemistry
The journal of physical chemistry. A, 2012
We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO... more We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO and pentoxy radicals. One-color multiphoton ionization with ultrashort laser pulses through the S(2) state resonance gives rise to photoelectron spectra that reflect ionization from the S(1) state. Time-resolved pump-probe photoionization measurements show that upon excitation at 207 nm, the generation of NO in the v = 2 state is delayed, with a rise time of 283 (16) fs. The time-resolved mass spectrum shows the NO to be expelled with a kinetic energy of 1.0 eV, which is consistent with dissociation on the S(1) state potential energy surface. Combined, these observations show that the first step of the dissociation reaction involves an internal conversion from the S(2) to the S(1) state, which is followed by the ejection of the NO radical on the predissociative S(1) state potential energy surface.
The Journal of …, Jan 1, 2010
The photoelectron spectrum shows that multiphoton ionization of amyl nitrite, C(5)H(11)ONO, using... more The photoelectron spectrum shows that multiphoton ionization of amyl nitrite, C(5)H(11)ONO, using ultrafast laser pulses deposits up to 3.7 eV of energy into internal degrees of freedom. As a result, the molecules fragment to produce various daughter ions of masses 87, 71, 60, 57, 41, 30, 29, and 27. Absorption of an additional photon with 3 eV of energy by the ions yields transients with picosecond decay times, revealing the time scale of the decomposition dynamics of the initially prepared parent ion. Each mass peak has a distinct time constant, in the range of 1.2 to 7.9 ps, emphasizing the dependence of the fragmentation mechanism on the ion internal energy.
Journal of Molecular …, Jan 1, 2010
66th International …, Jan 1, 2011
The ultrafast structural dynamics of 1,3-cyclohexadiene has been investigated using structurally ... more The ultrafast structural dynamics of 1,3-cyclohexadiene has been investigated using structurally sensitive Rydberg electron binding energies. Excitation to the 1B state and the 3p Rydberg state yielded different structural responses. In both experiments, the structural dynamics of the molecular core are reflected by time-dependent shifts of the Rydberg electron binding energy. Structural distortions associated with 3p-excitation cause a dynamical shift
• Electron is moving in Coulomb potential created by proton
66th International …, Jan 1, 2011
ABSTRACT The structural response of several tertiary amines to electronic excitation has been inv... more ABSTRACT The structural response of several tertiary amines to electronic excitation has been investigated using Rydberg Fingerprint Spectroscopy. The 3p Rydberg states are reached by excitation with a 5.93 eV photon while 3s states are populated by electronic relaxation from 3p state. We observe binding energy shifts on ultrafast time scales in all peaks that reflect the structural change of the molecular ion cores. The shifts are in the range of 15 meV to 30 meV, within time scales of less than 500 fs, depending on the specific molecular systems and the nature of the electronic state. In cases where the p states are spectrally separate, the trends of the energy shifts are different for the pz and pxy Rydberg states whereas the pz and s states are similar. This suggests that the response of the Rydberg states to structural displacements depends on the symmetry. Very fast binding energy shifts, observed on sup-picosecond time scales, are attributed to the structural adjustment from a pyramidal to a planar structure upon Rydberg excitation. The quantitative values of the binding energy shifts can also be affected by laser chirp, which we model using simulations.