The pathway, in which a protein folds, is most likely governed by early """"""""seeding"""""""" events and transient conformational changes defined by the biomolecules primary sequence. In order to understand fully the correlation between the primary sequence and the pathway through which proteins fold to their native conformations will require knowledge of the entire kinetic history. Current stopped flow methods can following the folding events over a range from milliseconds and longer, yet, there is significant information lost in the stopped-flow dead time (less than milliseconds in time). We have synthesized several alpha helical peptides which are stabilized by a tyrosinate disulfide bridge that are candidates for photochemical breakage of the S-S bond. In order to analyze the kinetic history over as many decades in time, we have constructed a dual Nd:YAG regen system. In this system, two regenerative amplifiers are seeded in parallel by a pulse from a modelocked Nd:YAG. The shortest time delays (70 ps to 20 ns) are determined by an optical time delay (optical rail) whereas the longer time delays are set by triggering the Pockels cell of the probe regen to successive pulses in the mode locked train. In this way, we can delay out to the repetition rate of the regen system (1 kHz = 1 ms). The probe regen is configured in two ways: 1) a visible travelling wave dye laser (~610 nm) can probe the S? radical of the broken S-S bond as a monitor of the recombination of the peptide ends; 2) the probe laser can be used to create a mid -IR pulse (~ 6 ?m) in order to probe the Amide I region of this peptide. The system can be easily switched between either configuration.
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