Coherent control of bond breaking in amino acid complexes with tailored femtosecond pulses

Abstract

Intense femtosecond laser pulses, judiciously tailored in an adaptive, optimal control feedback loop were used to break preferentially the acyl-N ("peptide") bond of Ac-Phe-NHMe that may be regarded as a dipeptide model. We show that coherent excitation of complex wave packets in the strong-field regime allows to cleave strong backbone bonds in the molecular system preferentially, while keeping other more labile bonds intact. These results show the potential of pulse shaping as a powerful complementary analytical tool for protein sequencing of large biopolymers in addition to the well-known mass spectrometry and chemical analysis.

Quantitative differentiation of dyes with overlapping one-photon spectra by femtosecond pulse-shaping

“…This can be accomplished via the multiplicative fitness parameter (A– c )( c −1 -B), where values of A and B are normalized to the unshaped pulse measurement (obtained when the Dazzler performs no phase or amplitude shaping beyond compensation of its own dispersion). We have found that setting the constant c to 0.8 yields better convergence in our experimental conditions, relative to the original implementation of unity for c 27, as this enables the GA to explore a broader range of signal strengths.…”

Control of the blue fluorescent protein with advanced evolutionary pulse shaping

“…To avoid bias towards the noise-dominated low-signal regime, we maximize a ratio A/B with the fitness parameter (A-c)(c −1 -B), where values of A and B are normalized to the unshaped pulse measurement. We have found that setting c to 0.8 yields better convergence relative to the original implementation of unity for c [13]. If both multiplicands are negative, an infinite negative fitness is given to the pulse.…”

Selectivity in fragmentation of N-methylacetamide after resonant K-shell excitation

“…Here the localized excitations resulted in the cleavage of the stronger N-C α bonds before the energy was distributed throughout the molecule. Furthermore the use of intense femtosecond near infrared laser beams with feedbackoptimized pulse shapes has revealed preferential cleavage of specific peptide bonds 19 . This type of control has potential use as a complementary tool for protein sequencing 19 .…”