The coherent 11-cis-retinal photoisomerization dynamics in bovine rhodopsin was studied by femtosecond time-resolved laser absorption spectroscopy at 30-fs resolution. Femtosecond pulses of 500, 535, and 560 nm wavelength were used for rhodopsin excitation to produce different initial Franck-Condon states and relevant distinct values of the vibrational energy of the molecule in its electron excited state. Time evolution of the photoinduced rhodopsin absorption spectra was monitored after femtosecond excitation in the spectral range of 400-720 nm. Oscillations of the time-resolved absorption signals of rhodopsin photoproducts represented by photorhodopsin(570) with vibrationally-excited all-trans-retinal and rhodopsin(498) in its initial state with vibrationally-excited 11-cis-retinal were studied. These oscillations reflect the dynamics of coherent vibrational wave-packets in the ground state of photoproducts. Fourier analysis of these oscillatory components has revealed frequencies, amplitudes, and initial phases of different vibrational modes, along which the motion of wave-packets of both photoproducts occurs. The main vibrational modes established are 62, 160 cm(-1) and 44, 142 cm(-1) for photorhodopsin(570) and for rhodopsin(498), respectively. These vibrational modes are directly involved in the coherent reaction under the study, and their amplitudes in the power spectrum obtained through the Fourier transform of the kinetic curves depend on the excitation wavelength of rhodopsin.

No abstract

Insulin stimulates carbohydrate uptake by cells and induces their conversion into lipids as a more efficient form of energy storage. Insulin resistance is associated with a decrease in glucose uptake by muscle and adipose cells and also with a decrease in glycogen synthesis on retention of glucose synthesis by liver cells. Disorders in the insulin signaling cascade on development of insulin resistance can be caused by both changes in functioning of transcriptional factors and in the secretion profile of hormone-like substances. Diacylglycerols and ceramides responsible for activation of some kinases and phosphatases can directly trigger these changes in muscle and liver cells. In adipose tissue, insulin mainly stimulates adipogenesis (adipocyte differentiation) and lipogenesis (lipid accumulation in the cells). Thus, studies on the action mechanisms of factors influencing adipogenesis can be of help for understanding the molecular mechanisms of insulin resistance.

No abstract

The dynamics of the coherent photoisomerization of the 11 cis retinal in bovine rhodopsin is studied by femtosecond time resolved laser absorption spectroscopy with a resolution of 30 fs. Rhodopsin is excited with 500 , 535 , and 560 nm femtosecond pulses to produce different initial Franck-Condon states with different vibrational energies of the molecule in its electronically excited state. The time evolution of the photoinduced differential absorption spectra of rhodopsin is measured upon excitation with a femtosecond pulse in a spectral range from 400 to 720 nm. Oscillations in the time resolved absorption of the rhodopsin photoproducts, such as photorhodopsin with a vibrationally excited all trans retinal and in its initial state rhodopsin with a vibrationally excited 11 cis retinal, are examined. It is demonstrated that these oscillations reflect the dynamics of coherent vibrational wavepackets. The Fourier transform of these oscillatory compo nents yields frequencies, amplitudes, and initial phases of various vibrational modes involved in the motion the wavepackets in both photoproducts. The main vibrational modes manifest themselves at frequencies of 62 and 160 cm -1 for photorhodopsin and 44 and 142 cm -1 for initial state rhodopsin. It is shown that these vibrational modes are directly involved in the coherent reaction under the study, with their amplitudes in the power spectrum produced by the Fourier transform of the kinetic curves being dependent on the wavelength of rhodopsin excitation.