Open Source 3D Multipurpose Measurement System with Submillimetre Fidelity and First Application in Magnetic Resonance.

Magnetic resonance imaging (MRI) is the mainstay of diagnostic imaging, a versatile instrument for clinical science and the subject of intense research interest. Advancing clinical science, research and technology of MRI requires high fidelity measurements in quantity, location and time of the given physical property. To meet this goal a broad spectrum of commercial measurement systems has been made available. These instruments frequently share in common that they are costly and typically employ closed proprietary hardware and software. This shortcoming makes any adjustment for a specified application difficult if not prohibitive. Recognizing this limitation this work presents COSI Measure, an automated open source measurement system that provides submillimetre resolution, robust configuration and a large working volume to support a versatile range of applications. The submillimetre fidelity and reproducibility/backlash performance were evaluated experimentally. Magnetic field mapping of a single ring Halbach magnet, a 3.0 T and a 7.0 T MR scanner as well as temperature mapping of a radio frequency coil were successfully conducted. Due to its open source nature and versatile construction, the system can be easily modified for other applications. In a resource limited research setting, COSI Measure makes efficient use of laboratory space, financial resources and collaborative efforts.

Simultaneous Interaction of Hydrophilic and Hydrophobic Solvents with Ethylamino Neurotransmitter Radical Cations: Infrared Spectra of Tryptamine(+)-(H2O)m-(N2)n Clusters (m,n ≤ 3).

Solvation of biomolecules by a hydrophilic and hydrophobic environment strongly affects their structure and function. Here, the structural, vibrational, and energetic properties of size-selected clusters of the microhydrated tryptamine cation with N2 ligands, TRA(+)-(H2O)m-(N2)n (m,n ≤ 3), are characterized by infrared photodissociation spectroscopy in the 2800-3800 cm(-1) range and dispersion-corrected density functional theory calculations at the ωB97X-D/cc-pVTZ level to investigate the simultaneous solvation of this prototypical neurotransmitter by dipolar water and quadrupolar N2 ligands. In the global minimum structure of TRA(+)-H2O generated by electron ionization, H2O is strongly hydrogen-bonded (H-bonded) as proton acceptor to the acidic indolic NH group. In the TRA(+)-H2O-(N2)n clusters, the weakly bonded N2 ligands do not affect the H-bonding motif of TRA(+)-H2O and are preferentially H-bonded to the OH groups of the H2O ligand, whereas stacking to the aromatic π electron system of the pyrrole ring of TRA(+) is less favorable. The natural bond orbital analysis reveals that the H-bond between the N2 ligand and the OH group of H2O cooperatively strengthens the adjacent H-bond between the indolic NH group of TRA(+) and H2O, while π stacking is slightly noncooperative. In the larger TRA(+)-(H2O)m clusters, the H2O ligands form a H-bonded solvent network attached to the indolic NH proton, again stabilized by strong cooperative effects arising from the nearby positive charge. Comparison with the corresponding neutral TRA-(H2O)m clusters illustrates the strong impact of the excess positive charge on the structure of the microhydration network.

Weak hydrogen bonding motifs of ethylamino neurotransmitter radical cations in a hydrophobic environment: infrared spectra of tryptamine(+)-(N2)n clusters (n ≤ 6).

Size-selected clusters of the tryptamine cation with N2 ligands, TRA(+)-(N2)n with n = 1-6, are investigated by infrared photodissociation (IRPD) spectroscopy in the hydride stretch range and quantum chemical calculations at the ωB97X-D/cc-pVTZ level to characterize the microsolvation of this prototypical aromatic ethylamino neurotransmitter radical cation in a nonpolar solvent. Two types of structural isomers exhibiting different interaction motifs are identified for the TRA(+)-N2 dimer, namely the TRA(+)-N2(H) global minimum, in which N2 forms a linear hydrogen bond (H-bond) to the indolic NH group, and the less stable TRA(+)-N2(π) local minima, in which N2 binds to the aromatic π electron system of the indolic pyrrole ring. The IRPD spectrum of TRA(+)-(N2)2 is consistent with contributions from two structural H-bound isomers with similar calculated stabilization energies. The first isomer, denoted as TRA(+)-(N2)2(2H), exhibits an asymmetric bifurcated planar H-bonding motif, in which both N2 ligands are attached to the indolic NH group in the aromatic plane via H-bonding and charge-quadrupole interactions. The second isomer, denoted as TRA(+)-(N2)2(H/π), has a single and nearly linear H-bond of the first N2 ligand to the indolic NH group, whereas the second ligand is π-bonded to the pyrrole ring. The natural bond orbital analysis of TRA(+)-(N2)2 reveals that the total stability of these types of clusters is not only controlled by the local H-bond strengths between the indolic NH group and the N2 ligands but also by a subtle balance between various contributing intermolecular interactions, including local H-bonds, charge-quadrupole and induction interactions, dispersion, and exchange repulsion. The systematic spectral shifts as a function of cluster size suggest that the larger TRA(+)-(N2)n clusters with n = 3-6 are composed of the strongly bound TRA(+)-(N2)2(2H) core ion to which further N2 ligands are weakly attached to either the π electron system or the indolic NH proton by stacking and charge-quadrupole forces.