Mechanism of Protein Molecule Isolation by IR Laser Ablation of Droplet Beam.

Gas-phase isolation of bovine serum albumin (BSA) from aqueous solutions is performed by IR laser ablation of a droplet beam. Multiply charged BSA ions (positive and negative) were produced by the IR laser irradiation onto a droplet beam of aqueous BSA solutions with various pH values prepared by addition of hydrochloric acid or sodium hydroxide to the solution. The isolation mechanism was discussed based on the charge state of the isolated BSA ions. A nanodroplet model explains the gas-phase charge distribution of the BSA ions. This study provides a fundamental basis for further studies of a wide variety of biomolecules in the gas phase isolated directly from solution.

Rotationally resolved high-resolution spectrum of the S(1)-S(0) transition of jet-cooled thioanisole.

The rotationally resolved high-resolution fluorescence excitation spectrum of the 0-0 band in the S(1)← S(0) electronic excitation of thioanisole was observed using the techniques of a collimated supersonic jet and a single-mode ultraviolet laser for the first time. High accurate rotational constants for the S(0) and the S(1) states have been determined by precisely calibrated transition energies of about 1000 assigned rotational lines. The molecular structure of thioanisole has been estimated by high-level MO calculations. The planarity of thioanisole in the S(0) and the S(1) states was also demonstrated clearly. The lifetime of the S(1) state was estimated to be 2.0 ns from the observed line width. This line shape did not change with the magnetic field of 1 Tesla, suggesting that the main radiationless process should be internal conversion to the S(0) state.