Few cycle optical pulse studies of the transition state process in myoglobin

Requisite to the detection of high frequency nuclear motions in biological molecules presented in this work was the development of very stable high power amplified laser systems and a reliable method to accurately manipulate the phase of broadband, ultrashort pulses. These systems include a novel two-head laser design providing up to 25 W of TEM₀₀ output and a unique compressed disk design which produces up to 20 W of TEM₀₀ output. The compressed disk design in particular represents a fundamental advance in the development of high power, high beam quality laser design and has the potential to scale to greater than 50 W output power. Also presented are the details of the development and construction of a versatile, sub-10 fs pulse generation and phase manipulation technique. This technique includes the generation of very broadband (as much as 150 nm) 150 fs duration visible pulses via noncollinear optical parametric amplification. These broadband pulses are then compressed to 7 fs pulse duration in a compact, glassless combination of static negatively chirped mirrors and a zero dispersion stretcher with a deformable mirror at the focal plane for the manipulation of the spectral phase. These ultrashort pulses are then used to investigate with very high resolution the early time dynamics of deoxyand carboxymyoglobin after the photoinitiated dissociation of the carbonmonoxide ligand. Using time domain pump-probe spectroscopy, we observe known oscillations of the heme in the MbCO photoproduct at frequencies corresponding to the deoxyMb species, indicating that these oscillations are driven by the dissociation event, not field driven wavepacket propagation due to Raman prepared ground state vibrational motion of MbCO. Furthermore, we measure the phase of these oscillations and find it to be consistent with a very fast (with 20–30 fs) crossing from the excited state of MbCO to the photoproduct ground state deoxyMb, with strong channeling of the excited state wavepacket into the ground state ν₇ and ν₄ oscillations of the heme. This is direct evidence of significant coupling between these in-plane vibrational motions and the conformational change of the heme upon ligand dissociation.