Structural motifs of oxacalix[4]arene for molecular recognition of nitroaromatic explosives: Experimental and computational investigations of host-guest complexes

Two new structural motifs based on oxacalix[4]arene appended N-(3-bromopropyl) phthalimide moieties, FON3PPh and PON3PPh was prepared, and its fluorogenic behaviors towards nitroaromatic explosives were investigated. The sensors exhibit preferential binding towards 4-nitro toluene (4-NT) and 2,6-dinitro toluene (2,6-DNT) based on the conformational orientation of the oxacalix[4]arene-host cavity. Spectrofluorimetric and 1H NMR titration studies support drastic changes inferred due to the complexation of the nitroaromatic explosives with FON3PPh and PON3PPh. The linear concentration range of FON3PPh for 4-NT is 5 μM to 4.5 mM with the detection limit of 2.4 μM and for PON3PPh, the linear concentration range 2,6-DNT is 0.5 μM to 5 mM with the detection limit of 0.1 μM. The binding ability of FON3PPh and PON3PPh for 4-NT and 2,6-DNT was determined as 1.15 × 104 M−1 and 3.02 × 104 M−1, respectively. Further, Density Functional Theory (DFT) based conformational modeling suggested that the spatial orientation of the guests in conformationally different hosts (PON3PPh and FON3PPh) lead to a varied selectivity pattern. The calculations also reveal that the complexation is thermodynamically favorable and selective. This work provides methodology to understand selective recognition of explosives based on structurally altered motifs of supramolecular architectures. The cytotoxic activity of FON3PPh and PON3PPh was also evaluated against human cancer cell lines in vitro

Manually defining regions of interest when quantifying paravertebral muscles fatty infiltration from axial magnetic resonance imaging: a proposed method for the lumbar spine with anatomical cross-reference

© 2017 The Author(s). Background: There is increasing interest in paravertebral muscle composition as a potential prognostic and diagnostic element in lumbar spine health. As a consequence, it is becoming popular to use magnetic resonance imaging (MRI) to examine muscle volume and fatty infiltration in lumbar paravertebral muscles to assess both age-related change and their clinical relevance in low back pain (LBP). A variety of imaging methods exist for both measuring key variables (fat, muscle) and for defining regions of interest, making pooled comparisons between studies difficult and rendering post-production analysis of MRIs confusing. We therefore propose and define a method as an option for use as a standardized MRI procedure for measuring lumbar paravertebral muscle composition, and to stimulate discussion towards establishing consensus for the analysis of skeletal muscle composition amongst clinician researchers. Method: In this descriptive methodological study we explain our method by providing an examination of regional lumbar morphology, followed by a detailed description of the proposed technique. Identification of paravertebral muscles and vertebral anatomy includes axial E12 sheet-plastinates from cadaveric material, combined with a series of axial MRIs that encompass sequencing commonly used for investigations of muscle quality (fat-water DIXON, T1-, and T2-weighted) to illustrate regional morphology; these images are shown for L1 and L4 levels to highlight differences in regional morphology. The method for defining regions of interest (ROI) for multifidus (MF), and erector spinae (ES) is then described. Results: Our method for defining ROIs for lumbar paravertebral muscles on axial MRIs is outlined and discussed in relation to existing literature. The method provides a foundation for standardising the quantification of muscle quality that particularly centres on examining fatty infiltration and composition. We provide recommendations relating to imaging parameters that should additionally inform a priori decisions when planning studies examining lumbar muscle tissues with MRI. Conclusions: We intend this method to provide a platform towards developing and delivering meaningful comparisons between MRI data on lumbar paravertebral muscle quality