Lipika Adhya - Academia.edu (original) (raw)
Papers by Lipika Adhya
Il Nuovo Cimento D, 1992
Summary We show that in case of (1+ 1)-photon resonant absorption to and emission from an autoion... more Summary We show that in case of (1+ 1)-photon resonant absorption to and emission from an autoionizing state embedded into a continuum, the gain profile can be modified significantly in the presence of a parallel near-resonant channel leading to another ...
Physical Review a, 1994
We know that the Fano profile is obtained for single-photon absorption to the ionization continuu... more We know that the Fano profile is obtained for single-photon absorption to the ionization continuum in the presence of an autoionizing state. We have shown that, in the case of (1+1)-photon absorption to an autoionizing state embedded in the ionization continuum, the absorption profile ...
Il Nuovo Cimento D, 1998
We have shown that the amplification without population inversion (AWOPI) from the first excited ... more We have shown that the amplification without population inversion (AWOPI) from the first excited autoionizing (AI) state of the lL;g symmetry of the H 2 molecules can be obtained when the lowest AI state of the lL;g symmetry is pumped incoherently. We have considered a resonant two-photon transition scheme from the ground X1L;g(v O,j 1) state to the ionization continuum embracing the two AI states (the lowest and the first excited autoionizing states) of the 1 L;g symmetry via the resonant intermediate B 1 L;u (v 4, j 2) level. The effect of two-photon nearresonant autoionizing channels via the near-resonant rovibrationallevels of the B 1 L;u state has also been considered. We have found that the gain can be obtained in different spectral regions corresponding to the resonances with the lowest and first excited AI states from the intermediate levels of the B 1 L;u state. The inherent coherence between two AI states due to the configuration interaction coupling via the common continuum has been found to have a significant effect on the amplification process, which occurs around all the resonance frequencies connecting this AI state with the intermediate levels. This gain can be significantly modified by increasing the coupling strength of this excited AI state with the continuum. Moreover, the gain from the excited AI state remains unaffected by the damping caused by incoherent pumping to the lowest AI state. It has also been shown that the persistence of inversionless gain from the excited AI state is shorter than that from the lowest AI state. The presence of close-lying near-resonant rovibrationallevels leads to the increase in gain around the resonances with two AI states from the B1L;u (v 4,j 2) level. The advantages of this type of scheme are; i) AWOPI can be obtained from an excited AI state although it has not been pumped and Ii) the amplification obtained from the excited AI state is almost unaffected by the distortion caused by incoherent pumping to the lower AI state. PACS 42.55.Ah-General laser theory. PACS 42.50.Hz-Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift.
Journal of Natural Science, Biology and Medicine, 2015
Background:There is experimental evidence of many cases of stable macromolecular conformations wi... more Background:There is experimental evidence of many cases of stable macromolecular conformations with charged amino-acids facing lipid, an arrangement thought to be energetically unfavourable. Methods and Objectives: Employing classical electrostatics, we show that, this is not necessarily the case and studied the physical basis of the specifi c role of proximity of charges to the dielectric interface between two different environments. We illustrate how self and induced energies due to the dielectric medium polarization, on either side of the interface, contribute differentially to the stability of a pair of charges and hence the mutual conformation of the S3b-S4 α-helix pair of the voltage-gated K + channel. Results and Conclusion: We show that (1) a pair of opposite charges on either side of lipid-protein interface confers signifi cant stability; (2) hydrophobic media has an important role in holding together two similar repelling charges; (3) dielectric interface has stabilizing effect on a pair of charges, when an ion is closer to its interface than its neighboring charge; (4) in spite of the presence of dielectric interface, there is a nonexistence of any dielectric effect, when an ion is equidistant from its image and neighboring charge. We also demonstrate that, variation in dielectric media of the surrounding environment confers new mutual conformations to S3b-S4 α-helices of voltage sensor domain at zero potential, especially lipid environment on the helix side, which improved stability to the confi guration by lowering the potential energy. Our results provide an answer to the long standing question of why charges face hydrophobic lipid membranes in the stable conformation of a protein.
Physical Review A, 2001
... 64, 523 1987 ; 66, 333 1988 . 6 L. Adhya, S. Sanyal, and K. RaiDastidar, Phys. Rev. A 52, 407... more ... 64, 523 1987 ; 66, 333 1988 . 6 L. Adhya, S. Sanyal, and K. RaiDastidar, Phys. Rev. A 52, 4078 1995 ; Nuovo Cimento D 20, 1283 1998 ; K. Rai Dastidar, L. Adhya, and R. Das, Pramana 52, 281 1999 ; G. Vemuri, KV Vasavada, and GS Agarwal, Phys. Rev. A 52, 3228 1995 . ...
Physical Review A, 1995
We have shown that (1+1′)-photon lasing without population inversion (LWOPI) can be achieved in a... more We have shown that (1+1′)-photon lasing without population inversion (LWOPI) can be achieved in a H 2 molecule for emission from the lowest doubly excited autoionizing (AI) state of 1 Σ g symmetry to the ground X 1 Σ g (v=0,j=1) state in the presence of the resonant B 1 Σ u ...
Physical Review A, 1994
We know that the Fano profile is obtained for single-photon absorption to the ionization continuu... more We know that the Fano profile is obtained for single-photon absorption to the ionization continuum in the presence of an autoionizing state. We have shown that, in the case of (1+1)-photon absorption to an autoionizing state embedded in the ionization continuum, the absorption profile ...
Journal of Natural Science, Biology and Medicine, 2013
Background: It is well known that α-helices of protein, possessing equal and opposite charged end... more Background: It is well known that α-helices of protein, possessing equal and opposite charged ends, behaves like a macrodipole, but the relative importance of such macrodipoles to the aggregation of a pair of helix in the voltage sensor domain (VSD) of K+ ion channel, has not been assessed. In the VSD, importance has been given primarily to the helically arranged Arginine residues of helix, but the role of the charged residues of S3b is less focused. Method and Objective: Applying electrostatic theory, we have studied the interaction between the charges of S3b-S4 α-helix pair of KvAP through virtual mutagenesis. Result and Conclusion: We have shown that the terminal charges arising from the inherent dipolar property of α-helices play an important role in affecting the stability of the S3b-S4 pair, and in determining its spatial position at zero transmembrane potential. Moreover, the negatively charged side chain of S3b was found to be the primary stabilizing factor in holding S3b-S4 pair together as a "paddle". Comparison of sequences of S3b helix of K+ channels from different species showed a previously unreported positional conservation of negative residues, highlighting their functional importance. These charges may contribute to the energetic of α-helix movements in an electric field.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2013
The voltage sensor domain (VSD) of the potassium ion channel KvAP is comprised of four (S1-S4) α-... more The voltage sensor domain (VSD) of the potassium ion channel KvAP is comprised of four (S1-S4) α-helix proteins, which are encompassed by several charged residues. Apart from these charges, each peptide α-helix having two inherent equal and opposite terminal dipolar charges behave like a macrodipole. The activity of voltage gated ion channel is electrostatic, where all the charges (charged residues and dipolar terminal charges) interact with each other and with the transmembrane potential. There are evidences that the role of the charged residues dominate the stabilization of the conformation and the gating process of the ion channel, but the role of the terminal dipolar charges are never considered in such analysis. Here, using electrostatic theory, we have studied the role of the dipolar terminal charges in aggregation of the S3b-S4 helix pair of KvAP in the absence of any external field (V = 0). A system attains stability, when its potential energy reaches minimum values. We have shown that the presence of terminal dipole charges (1) change the total potential energy of the charges on S3b-S4, affecting the stabilization of the α-helix pair within the bilayer lipid membrane and (2) the C-and the N-termini of the α-helices favor a different dielectric medium for enhanced stability. Thus, the dipolar terminal charges play a significant role in the aggregation of the two neighboring α-helices.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2013
Il Nuovo Cimento D, 1992
Summary We show that in case of (1+ 1)-photon resonant absorption to and emission from an autoion... more Summary We show that in case of (1+ 1)-photon resonant absorption to and emission from an autoionizing state embedded into a continuum, the gain profile can be modified significantly in the presence of a parallel near-resonant channel leading to another ...
Physical Review a, 1994
We know that the Fano profile is obtained for single-photon absorption to the ionization continuu... more We know that the Fano profile is obtained for single-photon absorption to the ionization continuum in the presence of an autoionizing state. We have shown that, in the case of (1+1)-photon absorption to an autoionizing state embedded in the ionization continuum, the absorption profile ...
Il Nuovo Cimento D, 1998
We have shown that the amplification without population inversion (AWOPI) from the first excited ... more We have shown that the amplification without population inversion (AWOPI) from the first excited autoionizing (AI) state of the lL;g symmetry of the H 2 molecules can be obtained when the lowest AI state of the lL;g symmetry is pumped incoherently. We have considered a resonant two-photon transition scheme from the ground X1L;g(v O,j 1) state to the ionization continuum embracing the two AI states (the lowest and the first excited autoionizing states) of the 1 L;g symmetry via the resonant intermediate B 1 L;u (v 4, j 2) level. The effect of two-photon nearresonant autoionizing channels via the near-resonant rovibrationallevels of the B 1 L;u state has also been considered. We have found that the gain can be obtained in different spectral regions corresponding to the resonances with the lowest and first excited AI states from the intermediate levels of the B 1 L;u state. The inherent coherence between two AI states due to the configuration interaction coupling via the common continuum has been found to have a significant effect on the amplification process, which occurs around all the resonance frequencies connecting this AI state with the intermediate levels. This gain can be significantly modified by increasing the coupling strength of this excited AI state with the continuum. Moreover, the gain from the excited AI state remains unaffected by the damping caused by incoherent pumping to the lowest AI state. It has also been shown that the persistence of inversionless gain from the excited AI state is shorter than that from the lowest AI state. The presence of close-lying near-resonant rovibrationallevels leads to the increase in gain around the resonances with two AI states from the B1L;u (v 4,j 2) level. The advantages of this type of scheme are; i) AWOPI can be obtained from an excited AI state although it has not been pumped and Ii) the amplification obtained from the excited AI state is almost unaffected by the distortion caused by incoherent pumping to the lower AI state. PACS 42.55.Ah-General laser theory. PACS 42.50.Hz-Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift.
Journal of Natural Science, Biology and Medicine, 2015
Background:There is experimental evidence of many cases of stable macromolecular conformations wi... more Background:There is experimental evidence of many cases of stable macromolecular conformations with charged amino-acids facing lipid, an arrangement thought to be energetically unfavourable. Methods and Objectives: Employing classical electrostatics, we show that, this is not necessarily the case and studied the physical basis of the specifi c role of proximity of charges to the dielectric interface between two different environments. We illustrate how self and induced energies due to the dielectric medium polarization, on either side of the interface, contribute differentially to the stability of a pair of charges and hence the mutual conformation of the S3b-S4 α-helix pair of the voltage-gated K + channel. Results and Conclusion: We show that (1) a pair of opposite charges on either side of lipid-protein interface confers signifi cant stability; (2) hydrophobic media has an important role in holding together two similar repelling charges; (3) dielectric interface has stabilizing effect on a pair of charges, when an ion is closer to its interface than its neighboring charge; (4) in spite of the presence of dielectric interface, there is a nonexistence of any dielectric effect, when an ion is equidistant from its image and neighboring charge. We also demonstrate that, variation in dielectric media of the surrounding environment confers new mutual conformations to S3b-S4 α-helices of voltage sensor domain at zero potential, especially lipid environment on the helix side, which improved stability to the confi guration by lowering the potential energy. Our results provide an answer to the long standing question of why charges face hydrophobic lipid membranes in the stable conformation of a protein.
Physical Review A, 2001
... 64, 523 1987 ; 66, 333 1988 . 6 L. Adhya, S. Sanyal, and K. RaiDastidar, Phys. Rev. A 52, 407... more ... 64, 523 1987 ; 66, 333 1988 . 6 L. Adhya, S. Sanyal, and K. RaiDastidar, Phys. Rev. A 52, 4078 1995 ; Nuovo Cimento D 20, 1283 1998 ; K. Rai Dastidar, L. Adhya, and R. Das, Pramana 52, 281 1999 ; G. Vemuri, KV Vasavada, and GS Agarwal, Phys. Rev. A 52, 3228 1995 . ...
Physical Review A, 1995
We have shown that (1+1′)-photon lasing without population inversion (LWOPI) can be achieved in a... more We have shown that (1+1′)-photon lasing without population inversion (LWOPI) can be achieved in a H 2 molecule for emission from the lowest doubly excited autoionizing (AI) state of 1 Σ g symmetry to the ground X 1 Σ g (v=0,j=1) state in the presence of the resonant B 1 Σ u ...
Physical Review A, 1994
We know that the Fano profile is obtained for single-photon absorption to the ionization continuu... more We know that the Fano profile is obtained for single-photon absorption to the ionization continuum in the presence of an autoionizing state. We have shown that, in the case of (1+1)-photon absorption to an autoionizing state embedded in the ionization continuum, the absorption profile ...
Journal of Natural Science, Biology and Medicine, 2013
Background: It is well known that α-helices of protein, possessing equal and opposite charged end... more Background: It is well known that α-helices of protein, possessing equal and opposite charged ends, behaves like a macrodipole, but the relative importance of such macrodipoles to the aggregation of a pair of helix in the voltage sensor domain (VSD) of K+ ion channel, has not been assessed. In the VSD, importance has been given primarily to the helically arranged Arginine residues of helix, but the role of the charged residues of S3b is less focused. Method and Objective: Applying electrostatic theory, we have studied the interaction between the charges of S3b-S4 α-helix pair of KvAP through virtual mutagenesis. Result and Conclusion: We have shown that the terminal charges arising from the inherent dipolar property of α-helices play an important role in affecting the stability of the S3b-S4 pair, and in determining its spatial position at zero transmembrane potential. Moreover, the negatively charged side chain of S3b was found to be the primary stabilizing factor in holding S3b-S4 pair together as a "paddle". Comparison of sequences of S3b helix of K+ channels from different species showed a previously unreported positional conservation of negative residues, highlighting their functional importance. These charges may contribute to the energetic of α-helix movements in an electric field.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2013
The voltage sensor domain (VSD) of the potassium ion channel KvAP is comprised of four (S1-S4) α-... more The voltage sensor domain (VSD) of the potassium ion channel KvAP is comprised of four (S1-S4) α-helix proteins, which are encompassed by several charged residues. Apart from these charges, each peptide α-helix having two inherent equal and opposite terminal dipolar charges behave like a macrodipole. The activity of voltage gated ion channel is electrostatic, where all the charges (charged residues and dipolar terminal charges) interact with each other and with the transmembrane potential. There are evidences that the role of the charged residues dominate the stabilization of the conformation and the gating process of the ion channel, but the role of the terminal dipolar charges are never considered in such analysis. Here, using electrostatic theory, we have studied the role of the dipolar terminal charges in aggregation of the S3b-S4 helix pair of KvAP in the absence of any external field (V = 0). A system attains stability, when its potential energy reaches minimum values. We have shown that the presence of terminal dipole charges (1) change the total potential energy of the charges on S3b-S4, affecting the stabilization of the α-helix pair within the bilayer lipid membrane and (2) the C-and the N-termini of the α-helices favor a different dielectric medium for enhanced stability. Thus, the dipolar terminal charges play a significant role in the aggregation of the two neighboring α-helices.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2013