The supramolecular architectures of crystals of substituted benzenes possessing shearing mechanical properties have been analyzed from the viewpoint of energy of intermolecular interactions. It is demonstrated that suggested earlier layered structure of these crystals do not correspond to the character of intermolecular interactions. Analysis of the topology of intermolecular interactions indicates that the crystals have a columnar supramolecular architecture with weak interactions between the columns. The presence of shearing mechanical properties is caused by localization of intercolumnar interactions within some layers and a relatively small (less than 12 kcal mol 21 ) barrier of shift of molecules within this layer.

Spasticity, a common complication after spinal cord injury (SCI), is frequently accompanied by chronic pain. The physiological origin of this pain (critical to its treatment) remains unknown, although spastic motor dysfunction has been related to the hyperexcitability of motoneurons and to changes in spinal sensory processing. Here we show that the pain mechanism involves changes in sensory circuits of the dorsal horn (DH) where nociceptive inputs integrate for pain processing. Spasticity is associated with the DH hyperexcitability resulting from an increase in excitation and disinhibition occurring in two respective types of sensory interneurons. In the tonic-firing inhibitory lamina II interneurons, glutamatergic drive was reduced while glycinergic inhibition was potentiated. In contrast, excitatory drive was boosted to the adapting-firing excitatory lamina II interneurons while GABAergic and glycinergic inhibition were reduced. Thus, increased activity of excitatory DH interneurons coupled with the reduced excitability of inhibitory DH interneurons post-SCI could provide a neurophysiological mechanism of central sensitization and chronic pain associated with spasticity.

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The crystal structure of 1,1-dioxo-tetrahydro-1l 6 -thiopyran-3-one has been determined and analyzed in terms of the topology of intermolecular interactions between the basic molecule located in the asymmetric part of the unit cell and its first coordination sphere. Supramolecular architecture of the crystal represents packing of strongly bonded flat layers formed mainly due to the SLO … H-C hydrogen bonds. Comparison of the crystal structure of the title compound and its analogues demonstrates the major role of the sulfonic group in the crystal organization. A layered structure is observed also for cyclic sulfone without the carbonyl group and in the case of replacement of the CLO bond by a cyclic oxygen atom. Presence of a saturated six-membered ring is a second factor influencing the crystal structure of the title compound. Absence of a ring in the dimethylsulfone results in formation of a highly corrugated columnar structure. Similar architecture of the crystal is found also for the cyclohexanone. A highly corrugated columnar structure is observed also in the case of replacement of the carbonyl group of the title compound by a considerably more polar sulfoxide S-O bond which is more active in the formation of intermolecular hydrogen bonds than a sulfone SO 2 group.

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