• Satish Kumar
• Ashok Jangid

Bacteriorhodopsin (bR) is light sensitive protein in purple membrane of halobacterium salinarum. Chromophore is region in the bR molecule corresponding to visible and ultraviolet spectrum. Chromophore of bR has been investigated using quantum mechanical approach. Spectral shift in absorption was found in water medium as comparison to gases medium. A retinal chromophore is attached with lysine amino acid of one α helix of proteins structure. Absorption spectra and circular dichroism spectra of retinal chromophore with lysine opsin has been calculated. Energies of the seven electronically excited states of chromophore has been calculated for all nonbonding orbitals n, and bonding and anti bonding π and π* molecular orbitals (MOs). The complete active space self consisting field CASSCF and N-electrons valence perturbation theory of second order NEVPT2 methods are applied to calculate energies of electronically excited states. In CASSCF, calculation 10 active electrons were kept in 9 active orbitals. All energies of electronically excited were calculated around the HOMO and LUMO orbitals as these being most probable transitions for the active electrons. Time dependent density functional theory TD-DFT method has been applied to calculate the absorption spectra and CD spectra. CD spectra is selective absorption of one of the two orthogonal component of two linearly plane polarized incident light beams. Study shows that an isotropic nature of medium causes strong asymmetric or preferential absorptions of one field component and transparent for second orthogonal component.

Bacteriorhodopsin-bR, Protonated Schiff base- PSB, Complete active self consist field theory- CASSCF, N-electrons valence perturbation theory to second order-NEVPT2, Time dependent density functional theory- TD-DFT and Circular dichroism-CD

"Spectral Shift in Retinal Chromophore of bacteriorhodopsin (bR) Protein in Different Medium ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.6, Issue 1, page no.1-10, January-2019, Available :http://www.jetir.org/papers/JETIR1901501.pdf

"Spectral Shift in Retinal Chromophore of bacteriorhodopsin (bR) Protein in Different Medium ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.6, Issue 1, page no. pp1-10, January-2019, Available at : http://www.jetir.org/papers/JETIR1901501.pdf