No abstract

We report on the first direct nanoscale imaging of elementary edge dislocations in a thermotropic smectic-C* liquid crystal with the Burgers vector equal to one smectic layer spacing d. We find two different types of dislocation profiles. In the dislocation of type A, the layers deformations lack mirror symmetry with respect to the plane perpendicular to the Burgers vector; the dislocation core size is on the order of d. In the dislocation of type S, the core is strongly anisotropic, extending along the Burgers vector over distances much larger (by a factor of 4) than d. The difference is attributed to a different orientation of the molecular tilt plane with respect to the dislocation's axis; the asymmetric layers distortions are observed when the molecular tilt plane is perpendicular to the axis and the split S core is observed when the molecules are tilted along the line.

Directly obtaining kinetic and mechanistic data for the reactions of nitroxyl (HNO) with biomolecules (k≈10 -10 m s ) is not feasible for many systems because of slow HNO release from HNO donor molecules (t is typically minutes to hours). To address this limitation, we have developed a photoactivatable HNO donor incorporating the (3-hydroxy-2-naphthalenyl)methyl phototrigger, which rapidly releases HNO on demand. A "proof of concept" study is reported, which demonstrates that, upon continuous xenon light excitation, rapid decomposition of the HNO donor occurs within seconds. The amount of HNO generated is strongly dependent on solvent and the rate of the reaction is dependent on the light intensity.

The design and synthesis of a photoactivatable HNO donor incorporating the (6-hydroxynaphthalen-2-yl)­methyl (6,2-HNM) photocage coupled to the trifluoromethanesulfonamidoxy analogue of the well-established HNO generator Piloty’s acid is described. The photoactive HNO donor stoichiometrically generates HNO (∼98%) at neutral pH conditions, and evidence for concerted C–O and N–S bond cleavage was obtained. The methanesulfonamidoxy analogue primarily undergoes undesired N–O bond cleavage.

No abstract