Precise Calculation of Single and Double Ionization of Hydrogen Molecule in Intense Laser Pulses

A new simulation box setup is introduced for the precise description of the wavepacket evolution of two electronic systems in intense laser pulses. In this box, the regions of the hydrogen molecule H$_{2}$, and singly and doubly ionized species, H$_{2}^+$ and H$_{2}^{+2}$, are well recognized and their time-dependent populations are calculated at different laser field intensities. In addition, some new regions are introduced and characterized as quasi-double ionization and their time-dependencies on the laser field intensity are calculated and analyzed. The adopted simulation box setup is special in that it assures proper evaluation of the second ionization. In this study, the dynamics of the electrons and nuclei of the hydrogen molecule are separated based on the adiabatic approximation. The time-dependent Schr\"{o}dinger and Newton equations are solved simultaneously for the electrons and the nuclei, respectively. Laser pulses of 390 nm wavelength at four different intensities (i.e. $1\times10^{14}$, $5\times10^{14}$, $1\times10^{15}$, and $5\times10^{15}$ W cm$^{-2}$) are used in these simulations. Details of the central H$_{2}$ region is also presented and discussed. This region is divided into four sub-regions related to the ionic state H$^+$H$^-$ and covalent (natural) state HH. The effect of the motion of nuclei on the enhanced ionization is discussed. Finally, some different time-dependent properties are calculated and their dependencies on the intensity of the laser pulse are studied, and their correlations with the populations of different regions are analyzed.Comment: 30 pages, 17 figure

Thermal stability of pepsin: A predictive thermodynamic model of a multi-domain protein

Pepsin is generally used in the preparation of F(ab)2 fragments from antibodies. The antibodies that are one of the largest and fastest growing categories of bio- pharmaceutical candidates. Differential scanning calorimetric is principally suitable method to follow the energetics of a multi-domain, fragment to perform a more exhaustive description of the thermodynamics in an associating system. The thermodynamical models of analysis include the construction of a simultaneous fitting of a theoretical expression. The expression depending on the equilibrium unfolding data from multimeric proteins that have a two-state monomer. The aim of the present study is considering the DSC data in connection with pepsin going through reversible thermal denaturation. Afterwards, we calculate the homology modeling identification of pepsin in complex multi-domain families with varied domain architectures. In order to analyze the DSC data, the thermal denaturation of multimer proteins were considered, the “two independent two-state sequential transitions with domains dissociation model” was introduced by using of the effective ΔG concept. The reversible unfolding of the protein description was followed by the two-state transition quantities which is a slower irreversible process of aggregation. The protein unfolding is best described by two non-ideal transitions, suggesting the presence of unfolding intermediates. These evaluations are also applicable for high throughput investigation of protein stability

Thermal denaturation of pepsin at acidic media: Using DSC, MALDI-TOF MS and PAGE techniques

The thermal stability of pepsin in a strong acid medium as a function of pH has been investigated using differential scanning calorimetry (DSC), UV absorbance, polyacrylamide gel electrophoresis (PAGE) and MALDI-TOF MS methods. The two independent two-state transitions model with view of physiological function of pepsin was used for analyzing thermal denaturation curves. The transition temperature (T-m) values ranging from 305.15 to 319.15K for the first transition and from 322.15 to 349.15K for the second transition in the examined pH range implicating the higher stability at pH 4 are in good agreement with MALDI-TOF MS results. The corresponding maximum, Delta G degrees(25), was stability obtained at pH 4 with values of 65.3 kJ mol(-1). (C) 2013 Elsevier B.V. All rights reserved