Prof. Massimo Olivucci

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We use state-of-the-art quantum chemical methods to investigate the photophysics, photoisomerization and protein catalysis of the protonated Schiff base of retinal (i.e. the chromophore of the human visual pigment rhodopsin and of the bacterial photosynthetic pigment bacteriorhodopsin). The main targets of this research are to comprehend the structural and electronic requirements that make the retinal chromophore able to fulfill its biological role and to explain why other structurally related conjugated systems cannot. Recently we have demonstrated that the computed reaction co-ordinate supports a "two-state two-mode model" of the photoisomerization which constitutes a substantial revision of the previously proposed models. This model has recently been confirmed by several different time-resolved experiments. The investigation of other biological photoreceptors is currently a major research line in our laboratory.

The main target of the present research is the computational investigation of excited state minimum energy paths (MEP) in protein environments. The novel computational strategy employed for such a study is based on a hybrid QM/MM scheme, that can be correctly applied to the investigation of an electronically excited chromophore covalently linked to a protein matrix.

The expected result is an atomic-level description of the mechanism lying behind the protein catalysis in rhodopsin-like systems. This will allow us to investigate the effects of the modification in the chromophore and in the protein matrix on the catalytic activities and on some spectroscopic properties, comparing with experimental data available.

The search for smaller and smaller components for machines is a major challenge for science. Nanoscale machinery is nowadays a hot topic due to the far-reaching consequences in daily life that might have the size reduction in common components such as switches or motors. The research in this field requires high-level tools, usually involving synthetic and computational chemists. Mother Nature offers ingenious solutions to control motion at molecular level converting chemical energy into mechanical energy. For instance, the protonated Schiff base of retinal, the chromophore of rodopsin proteins, undergoes a unidirectional photoisomerization that triggers a conformational change of the protein scaffold. Using these examples as an inspiration, we are currently working in a new kind of light-driven molecular motor, where rotary motion is produced upon a photochemical stimulus.

We have concluded, by means of isomerization path computations, that molecules containing the rigid framework of 4-(cyclopent-2'-enylidene)-3,4-dihydro-2H-pyrrolium cation undergo a UV-visible light-driven cis-trans isomerization along the central C-C double bond.

The irradiation of such molecules with UV-visible light causes the trans-cis isomerization along the central double bond. Our efforts are directed towards the design, synthesis and photochemical study of this kind of systems. The possibility of tuning the photostability and composition of the photostationary equilibrium through the use of different structures and substituents, as well as the capacity to induce an unidirectional motion allow considering this kind of systems as a promising example of what a molecular motor should be.

2000. Infrastruttura di calcolo costuita da: quattro processori IBM eServer pSeries 630 Model 6E4; due processori IBM RS/6000 44P-270; due processori Compaq DS25; un processore Compaq XP1000 e due processori IBM RS/6000 260; una workstation a due processori Compaq DS25.
2003. Due workstation a due processori HP-rx2600 Itenium.
2004. Cluster di otto processori di tipo HP-rx2600 o IBM-xSeries 382 Itenium 2.
2005. 2 workstation a due processori IBM-xSeries 326.