The use of Forster resonance energy transfer (FRET) as a probe of the structure of biological molecules through fluorescence measurements in solution is well-attested. The transposition of this technique to the gas phase is appealing since it opens the perspective of combining the structural accuracy of FRET with the specificity and selectivity of mass spectrometry (MS). Here, we report FRET results on gasphase polyalanine ions obtained by measuring FRET efficiency through specific photofragmentation rather than fluorescence. The structural sensitivity of the method was tested using commercially available chromophores (QSY 7 and carboxyrhodamine 575) grafted on a series of small, alanine-based peptides of differing sizes. The photofragmentation of these systems was investigated through action spectroscopy, and their conformations were probed using ion mobility spectrometry (IMS) and Monte Carlo minimization (MCM) simulations. We show that specific excitation of the donor chromophore results in the observation of fragments that are specific to the electronic excitation of the acceptor chromophore. This shows that energy transfer took place between the two chromophores and hence that the action-FRET technique can be used as a new and sensitive probe of the structure of gas-phase biomolecules, which opens perspectives as a new tool in structural biology.F orster resonance energy transfer (FRET) is a widely used probe of molecular structure in solution. 1−4 It requires a photon source to electronically excite the so-called "donor chromophore" and a light-harvesting setup to detect either the "donor" or "acceptor" chromophore fluorescence. The occurrence of FRET is then usually evidenced through a decrease in the fluorescence of the donor chromophore (quenching), with the concurrent onset of the fluorescence of the acceptor chromophore or by changes in fluorescence decay times. The interpretation of FRET results relies on the known distance dependence of the effect and on the possibility to graft specific chromophores at relatively well-defined sites on a molecule. FRET is then used to characterize the distance between the chromophores and hence separation between the grafting sites, although extracting exact distances is difficult due to the uncertainty of the exact orientation of the transition dipole moments of the chromophores. This allows the use of FRET to probe intra-or intermolecular distances, especially the change in distance, depending on whether the chromophores are attached to the same or to different molecules.The versatility of FRET makes it a powerful tool to assess the conformation and/or association of molecules. It has been shown that the overall structure of complex molecular edifices can be preserved in the gas phase using soft ionization techniques. 5,6 Therefore, the development of techniques capable of probing FRET in the gas phase is of high interest and could be integrated into a global approach for structure determination of proteins and protein complexes. 7−9 There are few tec...

This manuscript describes a new experimental setup that allows to perform tandem ion mobility spectrometry (IMS) measurements and which is coupled to a high resolution time-of-flight mass spectrometer. It consists of two 79 cm long drift tubes connected by a dual ion funnel assembly. The setup was built to permit laser irradiation of the ions in the transfer region between the two drift tubes. This geometry allows selecting ions according to their ion mobility in the first drift tube, to irradiate selected ions, and examine the ion mobility of the product ions in the second drift tube. Activation by collision is possible in the same region (between the two tubes) and between the second tube and the time-of-flight. IMS-IMS experiments on Ubiquitin are reported. We selected a given isomer of charge state +7 and explored its structural rearrangement following collisional activation between the two drift tubes. An example of IMS-laser-IMS experiment is reported on eosin Y, where laser irradiation was used to produce radical ions by electron photodetachment starting from doubly deprotonated species. This allowed measuring the collision cross section of the radical photo-product, which cannot be directly produced with an electrospray source.

The gas phase conformations of two amyloid beta mutants are studied by multiple techniques to elucidate the origin of the different aggregation behaviour.

Recent evidence suggests that ERAS might also be suited to pediatric surgery 1,2 and might, as previously demonstrated in adults, have beneficial effects in terms of recovery, hospital length of stay (HLOS), and overall quality of care. 3,4 Scoliosis surgery is a major surgical procedure in pediatrics, 5,6 and the postoperative period is often very challenging. Intense postoperative pain and high postoperative opioid consumption 5,6 result in high incidences of nausea, vomiting, constipation, and urinary retention. Early efficacious physiotherapy is frequently hindered by pain and analgesic side effects. In addition, cognitive impairment,

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Ion mobility experiments are combined with Infra-Red Multiple Photon Dissociation (IRMPD) spectroscopy and quantum chemical calculations for assessing the role of chirality in the structure of protonated and sodiated di- or tetra-peptides. Sodiated systems show a strong chirality dependence of the competition between Na(+)O and Na(+)π interactions. Chirality effects are more subtle in protonated systems and manifest themselves by differences in the secondary interactions such hydrogen bonds between neutral groups or those involving the aromatic rings.

Monitoring the chromism induced by intramolecular hydrogen and charge transfers within proteins as well as the isomerization of both protein and cofactor is essential not only to understand photoactive signaling pathways but also to design targeted opto-switchable proteins. We used a dual-ion mobility drift tube coupled to a tunable picosecond laser to explore the optical and structural properties of a peptide chain bound to a chromophore—a prototype system allowing for a proton transfer coupled to conformational change. With the support of molecular dynamics and DFT calculations, we show how proton transfer between the peptide and its cofactor can dramatically modify the optical properties of the system and demonstrate that these changes can be triggered by collisional activation in the gas phase.

Coronal alignment was restored in both groups. Hyperselective posterior fusions can be considered in Lenke 5 AIS, preserving one or two mobile segments, with similar clinical and radiological outcomes. However, selection of the LIV according to SV and LTV need to be accurately analyzed in order to avoid adding-on during follow-up.