Hydration Structures of the Human Protein Kinase CK2α Clarified by Joint Neutron and X-ray Crystallography.

Casein kinase 2 (CK2) has broad phosphorylation activity against various regulatory proteins, which are important survival factors in eukaryotic cells. To clarify the hydration structure and catalytic mechanism of CK2, we determined the crystal structure of the alpha subunit of human CK2 containing hydrogen and deuterium atoms using joint neutron (1.9 Šresolution) and X-ray (1.1 Šresolution) crystallography. The analysis revealed the structure of conserved water molecules at the active site and a long potential hydrogen bonding network originating from the catalytic Asp156 that is well known to enhance the nucleophilicity of the substrate OH group to the γ-phospho group of ATP by proton elimination. His148 and Asp214 conserved in the protein kinase family are located in the middle of the network. The water molecule forming a hydrogen bond with Asp214 appears to be deformed. In addition, mutational analysis of His148 in CK2 showed significant reductions by 40%-75% in the catalytic efficiency with similar affinity for ATP. Likewise, remarkable reductions to less than 5% were shown by corresponding mutations on His131 in death-associated protein kinase 1, which belongs to a group different from that of CK2. These findings shed new light on the catalytic mechanism of protein kinases in which the hydrogen bond network through the C-terminal domain may assist the general base catalyst to extract a proton with a link to the bulk solvent via intermediates of a pair of residues.

Quantum optimal control pathways of ozone isomerization dynamics subject to competing dissociation: a two-state one-dimensional model.

We construct a two-state one-dimensional reaction-path model for ozone open → cyclic isomerization dynamics. The model is based on the intrinsic reaction coordinate connecting the cyclic and open isomers with the O2 + O asymptote on the ground-state (1)A(') potential energy surface obtained with the high-level ab initio method. Using this two-state model time-dependent wave packet optimal control simulations are carried out. Two possible pathways are identified along with their respective band-limited optimal control fields; for pathway 1 the wave packet initially associated with the open isomer is first pumped into a shallow well on the excited electronic state potential curve and then driven back to the ground electronic state to form the cyclic isomer, whereas for pathway 2 the corresponding wave packet is excited directly to the primary well of the excited state potential curve. The simulations reveal that the optimal field for pathway 1 produces a final yield of nearly 100% with substantially smaller intensity than that obtained in a previous study [Y. Kurosaki, M. Artamonov, T.-S. Ho, and H. Rabitz, J. Chem. Phys. 131, 044306 (2009)] using a single-state one-dimensional model. Pathway 2, due to its strong coupling to the dissociation channel, is less effective than pathway 1. The simulations also show that nonlinear field effects due to molecular polarizability and hyperpolarizability are small for pathway 1 but could become significant for pathway 2 because much higher field intensity is involved in the latter. The results suggest that a practical control may be feasible with the aid of a few lowly excited electronic states for ozone isomerization.

Ab initio MRSDCI study on the low-lying electronic states of the lithium chloride molecule (LiCl).

Potential energy curves (PECs) for the low-lying states of the lithium chloride molecule (LiCl) have been calculated using the internally contracted multireference single- and double-excitation configuration interaction (MRSDCI) method with the aug-cc-PVnZ (AVnZ) and aug-cc-PCVnZ (ACVnZ) basis sets, where n = T, Q, and 5. First, we calculate PECs for 7 spin-orbit (SO)-free Λ-S states, X(1)Σ(+), A(1)Σ(+), (3)Σ(+), (1)Π, and (3)Π, and then obtain PECs for 13 SO Ω states, X0(+), A0(+), B0(+), 0(-)(I), 0(-)(II), 1(I), 1(II), 1(III), and 2, by diagonalizing the matrix of the electronic Hamiltonian plus the Breit-Pauli SO Hamiltonian. The MRSDCI calculations not including core orbital correlation through the single and double excitations are also performed with the AV5Z and ACV5Z basis sets. The Davidson corrections (Q0) are added to both the Λ-S and Ω state energies. Vibrational eigenstates for the obtained X(1)Σ(+) and X0(+) PECs are calculated by solving the time-independent Schrödinger equation with the grid method. Thus, the effects of basis set, core orbital correlation, and the Davidson correction on the X(1)Σ(+) and X0(+) PECs of LiCl are investigated by comparing the spectroscopic constants calculated from the PECs with one another and with experiment. It is confirmed that to accurately predict the spectroscopic constants we need to include core-electron correlation in the CI expansion and use the basis sets designed to describe core-valence correlation, i.e., ACVnZ. The SO PECs presented in this paper will be of help in the future study of diatomic alkali halide dynamics.

Quantum optimal control for the full ensemble of randomly oriented molecules having different field-free Hamiltonians.

We have presented the optimal control theory formulation to calculate optimal fields that can control the full ensemble of randomly oriented molecules having different field-free Hamiltonians. The theory is applied to the fifty-fifty mixture of randomly oriented (133)CsI and (135)CsI isotopomers and an optimal field is sought to achieve isotope-selective vibrational excitations with high efficiency. Rotational motion is frozen and two total times (T's) of electric field duration, 460,000 and 920,000 a.u. (11.1 and 22.2 ps), are chosen in the present calculation. As a result, the final yields for T = 460,000 and 920,000 a.u. are calculated to be 0.706 and 0.815, respectively. The relatively high final yield obtained for T = 920,000 a.u. strongly suggests that a single laser pulse can control the full ensemble of randomly oriented non-identical molecules. The result is quite encouraging in terms of the application to isotope-separation processes.

Coherent correlation between nonadiabatic rotational excitation and angle-dependent ionization of NO in intense laser fields.

We investigate coherent correlation between nonadiabatic rotational excitation and angle-dependent ionization of NO in intense laser fields in the state-resolved manner. When neutral NO molecules are partly ionized in intense laser fields (I(0) > 35 TW/cm(2)), a hole in the rotational wave packet of the remaining neutral NO is created because of the ionization rate depending on the alignment angle of the molecular axis with respect to the laser polarization direction. Rotational state distributions of NO are experimentally observed, and then the characteristic feature that the population at higher J levels is increased by the ionization can be identified. Numerical calculation for solving time-dependent rotational Schrödinger equations including the effect of the ionization is carried out. The numerical results suggest that NO molecules aligned perpendicular to the laser polarization direction are dominantly ionized at the peak intensity of I(0) = 42 TW/cm(2), where the multiphoton ionization is preferred rather than the tunneling ionization.

Quantum control study of multilevel effect on ultrafast isotope-selective vibrational excitations.

Quantum optimal control calculations have been carried out for isotope-selective vibrational excitations of the cesium iodide (CsI) molecule on the ground-state potential energy curve. Considering a gaseous isotopic mixture of (133)CsI and (135)CsI, the initial state is set to the condition that both (133)CsI and (135)CsI are in the vibrational ground level (v=0) and the target state is that (133)CsI is in the v=0 level while (135)CsI in the first-excited level (v=1). We find that, using the density-matrix formalism, perfect isotope-selective excitations for multilevel systems including more than ten lowest vibrational states can be completed in much shorter time scales than those for two-level systems. It is likely that this multilevel effect comes from the large isotope shifts in the vibrational levels of v>1. To check the reliability of the calculation we also carry out optimal control calculations based on the conventional wave-packet formalism, where the wave-function amplitude is temporally propagated on the grid points in real space, and obtain almost the same results as those with the density-matrix formalism.

Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel.

Quantum wave packet optimal control simulations with intense laser pulses have been carried out for studying molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open --> cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O(2) + O asymptote on the O(3) ground-state (1)A(') potential energy surface. Energetically, the cyclic ring isomer, the TS barrier, and the O(2) + O dissociation channel lie at approximately 0.05, approximately 0.086, and approximately 0.037 hartree above the open isomer, respectively. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum. The quick transition of the ozone wave packet avoids detrimental leakage into the competing O(2) + O channel. It is possible to obtain weaker optimal laser fields, resulting in slower transfer of the wave packets over the TS, when a reduced level of isomerization is satisfactory.

Ab initio study on the ground and low-lying excited states of cesium iodide (CsI).

Potential energy curves (PECs) for the ground and low-lying excited states of the cesium iodide (CsI) molecule have been calculated using the internally contracted multireference configuration interaction calculation with single and double excitation method with the relativistic pseudopotentials. PECs for seven Lambda-S states, X 1Sigma+, 2 1Sigma+, 3Sigma+, 1Pi, and 3Pi are first calculated and then those for 13 Omega states are obtained by diagonalizing the matrix of the electronic Hamiltonian H(el) plus the effective one-electron spin-orbit (SO) Hamiltonian H(SO). Spectroscopic constants for the calculated ground X 0+-state PEC with the Davidson correction are found to agree well with the experiment. Transition dipole moments (TDMs) between X 0 and the other Omega states are also obtained and the TDM between X 0+ and A 0+ is predicted to be the largest and that between X 0+ and B 0+ is the second largest around the equilibrium internuclear distance. The TDMs between X 0+ and the Omega=1 states are estimated to be nonzero, but they are notably small as compared with those between the 0+ states. Finally, vibrational levels of the X 0+ PEC for the two isotopic analogs, (133)CsI and (135)CsI, are numerically obtained to investigate the isotope effect on the vibrational-level shift. It has been found that the maximized available isotope shift is approximately 30 cm(-1) around nu=136.

Energy-flow dynamics in the molecular channel of propanal photodissociation, C2H5CHO --> C2H6 + CO: direct ab initio molecular dynamics study.

Direct ab initio molecular dynamics calculations have been carried out for the molecular channel of the photodissociation of propanal, C2H5CHO --> C2H6 + CO, at the RMP2(full)/cc-pVDZ level of ab initio molecular orbital theory. The initial conditions were generated using the microcanonical sampling to put the excess energy randomly into all vibrational modes of the TS. Starting from the TS, a total of approximately 700 trajectories were numerically integrated for 100 fs. The obtained final energy distributions for the C2H6 and CO fragments and their relative translational motion were found to be quite similar to those obtained for the acetaldehyde reaction, CH3CHO --> CH4 + CO, in our previous study (Chem. Phys. Lett. 2006, 421, 549) despite the fact that the number of degree of freedom for C2H6 is larger than that for CH4. The coupling between the intrinsic reaction coordinate and one of the generalized normal modes orthogonal to it was predicted substantially strong around s = 1.4 amu(1/2) bohr, and it is expected that the energy flow out of C2H6 proceeds through this coupling. However, the obtained energy distributions strongly suggest that the coupling among the modes in C2H6 is quite small and the intramolecular energy redistribution does not occur efficiently in this molecule.