Ariana Rondi

Coherent manipulation of free amino acids fluorescence

Coherent manipulation of molecular wavepackets in biomolecules might contribute to the quest towards label-free cellular imaging and protein identification. We report the use of optimally tailored UV laser pulses in pump-probe depletion experiments that selectively enhance or decrease fluorescence between two aromatic amino acids: tryptophan (Trp) and tyrosine (Tyr). Selective fluorescence modulation is achieved with a contrast of ~35%. A neat modification of the time-dependent fluorescence depletion signal of Trp is observed, while the Tyr transient trace remains unchanged. The mechanism invoked for explaining the change of the depletion of Trp is a less efficient coupling between the fluorescing state and the higher non-radiative excited states by the optimally shaped pulse, than by the reference pulse.

MEMS for femtosecond pulse shaping applications

There are many potential applications for MEMS micromirror devices for femtosecond pulse shaping applications. Their broadband reflectivity gives them an advantage in comparison to devices such as liquid crystal- and acousto-optical modulators because of the possibility to directly shape UV pulses in the range 250 - 400 nm, and thus address UV-absorbing molecules. The identification and discrimination of biomolecules which exhibit almost the same spectra has sparked some interest in the last years as it allows real-time, environmental and optical monitoring. Here, we present the last developments using the Fraunhofer IPMS MEMS phase former capable of accomplishing such goals.

Label free optimal dynamic discrimination of biological macromolecules

The fast development of laser techniques, in particular, the generation of ultrashort femtosecond and even attosecond pulses opens new frontiers and various experimental tools for biomedical applications. The combination of pulse shaping and optimal control is a very promising tool based on coherent manipulation of wavepackets on an ultrafast time scale. It already has successfully been applied for optimal dynamic discrimination (ODD) experiments of biomolecules like free amino acids and flavins which are indistinguishable by spectroscopic means. This approach can be extended toward to label free cellular imaging and detection of chemical or biological substances.

Deep UV Strategy for Discriminating Biomolecules

Label-free selective discrimination of spectrally similar biomolecules, such as peptides and proteins using Optimal Control strategies is a challenge in a variety of practical applications such as label-free fluorescence imaging and protein identification. The principle of Optimal Control is based on the fact that a suitably shaped laser field can differently drive the dynamics of almost identical quantum systems [1, 2].

A Multi-Objective Genetic Approach for Optimal Control of Photo-Induced Processes

We have applied a multi-objective genetic algorithm to the optimization of multiphoton excited fluorescence. Our study indicates the consistent advantages this method can offer to experiments based on adaptive shaping of femtosecond pulses.