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Molecular clusters are non covalent aggregates recognized as a new state of matter, whose properties are neither those of the gas-phase isolated partners nor those of their condensed phases. Molecular clusters have proved to be ideal systems for modeling molecular recognition phenomena, and their applications in many scientific fields interlocking the physical and life sciences are now well assessed. In the last few years, it has become possible, through the use of advanced laser techniques, to study the single interactions acting between individual components of a cluster without the influence of the solvent. The studies were carried out developing laser spectroscopic methodologies, capable of characterizing molecular clusters and probing the chemical bond breaking and forming on an extremely short time scale. This contribution deals with chiral recognition of molecules and clusters of biological interest in the gas phase through the application of the laser resolved mass spectrometric Resonant Two Photon Ionization technique (R2PI). The measurement of the spectroscopic shifts and of the fragmentation thresholds of diasteromeric clusters allows the determination of the nature of the interactions which control the formation of biological material and affect their stability and reactivity.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Radical ions are open-shell elusive species of paramount importance in many organic reactions and in biological processes. Oxidative bond breaking and forming involving radical ions are common process taking place in asymmetric enzyme cavities. Side-chain Cα-CΒ bond fragmentation in the radical cations of aromatic alcohols is a common process in solution [1-3], whose efficiency is enhanced in polar solvents such as water. Hydrogen-bonding between the ion and the solvent in the relevant transition structure is thought as responsible of the rate acceleration [4]. Effects of achiral and chiral microsolvation on the radical cation of R-(+)-l-phenyl-l-propanol, have been investigated. The energy thresholds of the homolytic Cα-Cβ bond breaking of R-(+)-1-phenyl-1-propanol radical cation, its mono-hydrated cluster, and its clusters with (2R,3R)-(-)-2,3-butanediol and (2S,3S)-(+)-2,3-butanediol have been studied through two color Resonant Two Photon Ionization, Photodissociation and Mass Spectrometry. The barrier of the Cα-Cβ fragmentation is appreciably higher for the unsolvated molecular ion than for its adducts with solvent molecules. Moreover, marked differences in the ethyl loss fragmentation energy are observed for the clusters with water and with the two diols. In particular the homochiral cluster with (2R, 3R)-(-)-2,3-butanediol exhibits a fragmentation barrier higher than that of the corresponding heterochiral adduct with (25, 35)-(+)-2,3-butanediol.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present a novel optical system (patent pending), which makes homogeneous the spatial energy distribution of a light beam, independently of the local intensity fluctuations strength. It can also change the spot dimensions of the homogenized beam over a large range of values without replacement of any optical element and without changing the length of the radiation path.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser ablated chiral molecules and their clusters are studied by mass resolved R2PI technique. Attractive (electrostatic and polarization) and repulsive (steric) interaction influence both the shift and the binding energy of the complexes. In monofuctional systems, the homochiral complexes are found to be more stable than the heterochiral ones. The formation of stable L-Tyrosine-Aluminum (Al-Tyr) cluster in a supersonic beam expansion of a laser ablated Al-Tyr target has been observed.