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The ocular lens is an important determinant of overall vision quality whose refractive and transparent properties change throughout life. The lens operates an internal microcirculation system that generates circulating fluxes of ions, water and nutrients that maintain the transparency and refractive properties of the lens. This flow of water generates a substantial hydrostatic pressure gradient which is regulated by a dual feedback system that uses the mechanosensitive channels TRPV1 and TRPV4 to sense decreases and increases, respectively, in the pressure gradient. This regulation of water flow (pressure) and hence overall lens water content, sets the two key parameters, lens geometry and the gradient of refractive index, which determine the refractive properties of the lens. Here we focus on the roles played by the aquaporin family of water channels in mediating lens water fluxes, with a specific focus on AQP5 as a regulated water channel in the lens. We show that in addition to regulating the activity of ion transporters, which generate local osmotic gradients that drive lens water flow, the TRPV1/4‐mediated dual feedback system also modulates the membrane trafficking of AQP5 in the anterior influx pathway and equatorial efflux zone of the lens. Since both lens pressure and AQP5‐mediated water permeability (PH2O${P_{{{\mathrm{H}}_{\mathrm{2}}}{\mathrm{O}}}}$) can be altered by changes in the tension applied to the lens surface via modulating ciliary muscle contraction we propose extrinsic modulation of lens water flow as a potential mechanism to alter the refractive properties of the lens to ensure light remains focused on the retina throughout life. [ABSTRACT FROM AUTHOR]

The molecule of the title compound, C9H7NO, is nearly planar, with an r.m.s. deviation of 0.018 (7) Å. In the crystal structure, two molecules form an R²2(8) centrosymmetric dimer through N H⋯O hydrogen bonds. The three-dimensional packing is additionally stabilized through weak C—H⋯O interactions. [ABSTRACT FROM AUTHOR]

In the crystal structure of the title compound [systematic name: 3-amino-1,3-diazaspiro[4.5]decane-2,4-dione-phenylboronic acid (1/1)], C8H13N3O2·C6H7BO2, molecules are held together by O—H…O, N—H…O and C—H…O hydrogen bonds and by an N—H…π interaction. [ABSTRACT FROM AUTHOR]

The title compound, C26H26N2O3, crystallizes as a racemic mixture of R, R and S, S enantiomers. The two independent mol­ecules show a similar conformation. They are connected via C—H⋯O and C—H⋯π inter­actions to form ribbons along the a axis. [ABSTRACT FROM AUTHOR]

The title compound, C16H9NO4, also known as the 3-benzoylpyridinium betaine of squaric acid, exhibits a dipolar electronic ground-state structure with a positively charged pyridinium fragment and a negatively charged squarate moiety. In the molecule, the two aromatic rings are twisted by 56.03 (2)° relative to one another. The three-dimensional packing of the molecules is stabilized by C—H··O· short contacts. [ABSTRACT FROM AUTHOR]

The molecule of the title compound, C5H14NO4P, exists as a zwitterion rather than as [1-(hydroxyethyl­amino)propyl]­phospho­nic acid, with the N atom of the amino group protonated and the phospho­nic acid group negatively charged. In the crystal structure, the molecules are linked via extensive hydrogen bonding, forming layers parallel to (100). [ABSTRACT FROM AUTHOR]

In the title compound, NH4+·C4HO4−·H2O, the hydrogen squarate anions and water molecules are arranged to form planes almost parallel to bc. The ammonium cations are located between these planes and cross-link them in the a direction by means of an extensive network of hydrogen bonds. There are two symmetry-independent sets of cations and anions. One of the hydrogen squarate anions and one of the ammonium cations are situated on a twofold axis and the H atoms of these moieties are disordered over the symmetry-related sites. [ABSTRACT FROM AUTHOR]

The title compound, C6H12NO5P, was synthesized as an inter­mediate phase in a search for new N-(phosphono­methyl)glycine derivatives. The mol­ecules are held together by O—H⋯O hydrogen bonds, forming chains along the b axis in the crystal structure. The observed mol­ecular structure is compared with that calculated by the density functional theory method. [ABSTRACT FROM AUTHOR]

The crystal structures of four cyclo­alkane­spiro-4′-imidazolidine-2′,5′-dithiones, namely cyclo­pentane­spiro-4′-imidazolidine-2′,5′-dithione {systematic name: 1,3-diaza­spiro­[4.4]­nonane-2,4-dithione}, C7H10N2S2, cyclo­hexane­spiro-4′-imidazolidine-2′,5′-dithione {systematic name: 1,3-diaza­spiro­[4.5]decane-2,4-dithione}, C8H12N2S2, cyclo­heptane­spiro-4′-imidazolidine-2′,5′-dithione {systematic name: 1,3-diaza­spiro­[4.6]undecane-2,4-dithione}, C9H14N2S2, and cyclo­octane­spiro-4′-imidazolidine-2′,5′-dithione {systematic name: 1,3-di­aza­spiro­[4.7]dodecane-2,4-dithione}, C10H16N2S2, have been determined. The three-dimensional packing in all of the structures is based on closely similar chains, in which hydantoin moieties are linked through N—H⋯S hydrogen bonding. The size of the cyclo­alkane moiety influences the degree of its deformation. In the cyclo­octane compound, the cyclo­octane ring assumes both boat–chair and boat–boat conformations. [ABSTRACT FROM AUTHOR]

The title compound [systematic name: 1′-amino­cyclo­hexane­spiro-4′-imidazole-2′,5′(3′ H,4′ H)-dione], C8H13N3O2, has been synthesized and was found to crystallize in two different structures, both monoclinic and both with the same P21/ c space group. In the first structure, there are two mol­ecules in the asymmetric unit, one of which uses all of its hydrogen-bond donors and acceptors and forms undulating layers, while the other forms chains propagating perpendicular to the layers. In the second structure, there is only one independent mol­ecule and the packing is based on a chain structure mediated by hydrogen bonding between the hydantoin moieties and further grouped into hydro­philic layers separated by layers of the hydro­phobic cyclo­hex­yl groups. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, C9H12N+·C4H4O−, contains two independent 1,2,3,4-tetrahydroisoquinolinium cations and two independent hydrogensquarate anions. In one of the cations, the N atom is disordered over two positions with occupancies of approximately 0.8 and 0.2. The pyridinium rings adopt envelope conformations. The hydrogensquarate anions are linked to form cyclic tetramers through strong O—H...O hydrogen bonds. The tetrahydroisoquinolinium and hydrogensquarate ions are linked via N—H...O hydrogen bonds, forming a three-dimensional framework. [ABSTRACT FROM AUTHOR]

In the title compound, C11H10N+·C4H5O6−·2H2O, hydrogen tartrate anions and water molecules are linked by strong O—H...O hydrogen bonds to form corrugated layers. The 4-phenylpyridinium cation decorates the layer from both sides, being hydrogen bonded to the water molecule only. The three-dimensional packing of the complex layers is accomplished by strong π–π interactions of 3.668 (2) Å between the centroids of the benzyl and pyridine rings related by the symmetry operator ( x −  , − y +  , − z). [ABSTRACT FROM AUTHOR]

The article presents information on the structure of codeinone. Codeinone has been found to possess antitumor potential, with high cytotoxic activity against human promyelocytic leukaemic cell lines and is known that codeinone in the living cell is produced from the reaction of codeine with nicotinamide adenine dinucleotide phosphate. The molecular structure exhibits features typical for morphine derivatives, with a T-shaped configuration. The crystal packing was found to be stabilized by weak intermolecular C-H&3x22EF;O interactions.

The title compound (systematic name: 6α-acet­oxy-4,5α-ep­oxy-3-meth­oxy-17-meth­yl-morphin-7-ene), C20H23NO4, crystallizes with one mol­ecule in the asymmetric unit. The mol­ecular structure exhibits features typical of morphine derivatives with a T configuration. The three-dimensional packing is stabilized by inter­molecular C—H⋯N and C—H⋯π inter­actions. [ABSTRACT FROM AUTHOR]

The mol­ecule of the title compound, C21H22N2O2, is nearly planar, except for the C(CH3)2 group on the cyclo­hexene ring. Molecules are connected via electrostatic C⋯O contacts, forming zigzag pseudo-chains along the c axis. [ABSTRACT FROM AUTHOR]

In the title compound, 3,4-dioxo-2-(pyridinium-1-yl)cyclobut-1-enolate, C9H5NO3, molecules are connected three-dimensionally through nonclassical C—H...O and π–π interactions [3.220 (3) Å] between the oppositely charged squarate and pyridinium fragments. Classical hydrogen-bonding interactions are not observed. In the unit cell, only half an independent molecule is present and a twofold rotation axis passes through the pyridinium ring and the opposite CO group. [ABSTRACT FROM AUTHOR]

In the title compound, sodium 2-hydr­oxy-3,4-dioxocyclo­but-1-en-1-olate monohydrate, Na+·C4HO4−·H2O, the Na atom is six-coordinated by the O atoms from four hydrogensquarate anions and two water mol­ecules. The three-dimensional packing is stabilized by a system of hydrogen bonds. [ABSTRACT FROM AUTHOR]