Dynamics of hydrogen bonding and energy transfer in matrix-assisted laser desorption

A molecular dynamics simulation of matrix-assisted laser desorption is presented for host and guest particles with internal structure. The laser-induced phase transition is modeled in a hemispherical volume of pyridine-3-carboxylic acid matrix seeded with a leucine enkephalin guest molecule. Following an instantaneous temperature jump to 1500 K, representing the laser excitation, the network of hydrogen bonds is disrupted in approximately 3 ps. After a 0.7 ps segregation period, the guest molecule is entrained by the evaporating matrix molecules. The guest lift-off velocity is estimated at ≈ 156 m/s, a value about a factor of two lower than measured for neutral matrix molecules in similar systems.