Publications by authors named "Asha Brown"

Chiral communications exist in secondary structures of foldamers and copolymers via a network of noncovalent interactions within effective intermolecular force (IMF) range. It is not known whether long-range chiral communication exists between macromolecular tertiary structures such as peptide coiled-coils beyond the IMF distance. Harnessing the high sensitivity of single-molecule force spectroscopy, we investigate the chiral interaction between covalently linked DNA duplexes and peptide coiled-coils by evaluating the binding of a diastereomeric pair of three DNA-peptide conjugates.

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Purpose: To analyse the morphological characteristics of eyes with neovascular age-related macular degeneration (AMD) with good long-term visual acuity after anti-VEGF (vascular endothelial growth factor) therapy.

Methods: Retrospective, observational study of 175 patients with neovascular AMD with >5 years of follow-up after initiating anti-VEGF therapy. Spectral-domain optical coherence tomography images were assessed for thickness of pigment epithelial detachment (PED), subretinal hyper-reflective material (SHRM), subretinal fluid and subfoveal choroidal, as well as the integrity of the outer retinal bands.

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A series of heteroditopic receptors containing halogen bond (XB) and unprecedented chalcogen bond (ChB) donors integrated into a 3,5-bis-triazole pyridine structure covalently linked to benzo-15-crown-5 ether motifs exhibit remarkable cooperative recognition of halide anions. Multi-nuclear H, C, Te and F NMR, ion pair binding investigations reveal sodium cation-benzo-crown ether binding dramatically enhances the recognition of bromide and iodide halide anions, with the chalcogen bonding heteroditopic receptor notably displaying the largest enhancement of halide binding strength of over two hundred-fold, in comparison to the halogen bonding and hydrogen bonding heteroditopic receptor analogues. DFT calculations suggest crown ether sodium cation complexation induces a polarisation of the sigma hole of ChB and XB heteroditopic receptor donors as a significant contribution to the origin of the unique cooperativity exhibited by these systems.

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Background/aims: To report a case of a 65-year-old female who presented with bilateral anterior granulomatous uveitis, which led to the diagnosis of Rosai-Dorfman Disease (RDD) and the discovery of an associated pancreatic mass.

Methods: This is a retrospective case report of a single patient.

Results: A 65-year-old African American Female received a full workup for bilateral anterior granulomatous uveitis and was found to have a pancreatic mass on imaging.

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Cyclic oligonucleotides are valuable targets with a broad range of potential applications spanning molecular biology and nanotechnology. Of particular importance is their role as templates in the rolling circle amplification (RCA) reaction. We describe three different chemical cyclisation methods for the preparation of single-stranded cyclic DNA constructs.

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A new bis-triazacyclononane tris-pyridyl N -azacryptand ligand is prepared via a convenient one-pot [2+3] condensation reaction between triazacyclononane and 2,6-bis(bromomethyl) pyridine in the presence of M CO (M=Li, Na, K). The proton, lithium, sodium, potassium and lead(II) complexes of the ligand are characterised in the solid state. Preliminary solution-phase competition experiments indicate that the cryptand ligand preferentially binds lead(II) in the presence of sodium, calcium, potassium and zinc cations in methanol solution.

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Purpose: The retina is continually exposed to free radicals from its rich blood supply, numerous mitochondria, and photons of light which strike its surface. Most pathological processes that take place in the retina, such as inflammation, cell apoptosis, or angiogenesis, can hence involve free radicals directly or indirectly.  Since inflammatory and oxidative stress pathways underlie retinal pathology, compounds that address these factors are therefore natural choices for treatment.

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Neutral heteroditopic [2]rotaxane ion-pair host systems were synthesised via a Cu(ii) directed passive metal template strategy. Each rotaxane contains discrete, axle-separated interlocked binding sites for a guest anion and a transition metal countercation. The anion binding sites are composed of convergent X-H (X = C, N) hydrogen bond donor groups, or mixed X-H and C-I hydrogen and halogen bond donor groups, whereas an equivalent three-dimensional array of amine, pyridine and carbonyl oxygen donor groups comprise the transition metal binding site.

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An active metal template strategy was used to synthesise a neutral indolocarbazole containing [2]rotaxane anion host system. H NMR anion binding investigations reveal that the [2]rotaxane recognises a range of monoanions in acetone-d : DO 95 : 5 with an unusual interlocked host selectivity for acetate and dihydrogenphosphate oxoanions over halides. The rotaxane displays an overall selectivity for the sulfate dianion, favouring a 2 : 1 host : guest binding stoichiometry at low sulfate concentration and a 1 : 1 stoichiometry in the presence of excess sulfate.

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Neutral tetradentate halogen bond donor foldamers were synthesised and exhibit enhanced anion affinities over their hydrogen bonding analogues, displaying iodide selectivity over lighter halide, carboxylate and dihydrogen phosphate anions. A foldamer with a chiral (S)-binaphthol motif was demonstrated to distinguish between enantiomers of chiral anions.

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A halogen bond is an attractive non-covalent interaction between an electrophilic region in a covalently bonded halogen atom and a Lewis base. While these interactions have long been exploited as a tool in crystal engineering their powerful ability to direct supramolecular self-assembly and molecular recognition processes in solution has, until recently, been overlooked. During the last decade however an ever-increasing number of studies on solution-phase halogen-bond-mediated anion recognition processes has emerged.

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The synthesis, structure and anion-recognition properties of a new strapped-porphyrin-containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor-acceptor and coordinative pyridine-zinc interactions. The [2]catenane incorporates a three-dimensional, hydrogen-bond-donating anion-binding pocket; solid-state structural analysis of the catenane⋅chloride complex reveals that the chloride anion is encapsulated within the catenane's interlocked binding cavity through six convergent CH⋅⋅⋅⋅Cl and NH⋅⋅⋅Cl hydrogen-bonding interactions and solution-phase (1) H NMR titration experiments demonstrate that this complementary hydrogen-bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution.

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Strong bidentate ligation between a fluorinated isophthalate and binuclear lanthanide-DO3A species yields a new class of (19)F NMR agent with very high nuclear relaxation rates at physiologically-relevant pH.

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The synthesis and anion binding properties of novel halogen-bonding (XB) bis-iodotriazole-pyridinium-containing acyclic and [2]catenane anion host systems are described. The XB acyclic receptor displays selectivity for acetate over halides with enhanced anion recognition properties compared to the analogous hydrogen-bonding (HB) acyclic receptor. A reversal in halide selectivity is observed in the XB [2]catenane, in comparison to the acyclic XB receptor, due to the interlocked host's unique three-dimensional binding cavity, and no binding is observed for oxoanions.

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Binuclear lanthanide complexes consisting of two lanthanide binding domains in kinetically stable DO3A binding pockets linked by a 3-functionalized meta-xylyl bridge form stable 1:1 adducts with isophthalate and dinicotinate in water. The influence of buffer, pH and ligand structure on the binding of dinicotinate has been investigated.

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Prism use in adult diplopia.

Curr Opin Ophthalmol

September 2012

Purpose Of Review: Prismatic correction to restore binocularity in adult diplopia can be challenging. This review summarizes the results of prismatic correction in adults based on the cause of diplopia.

Recent Findings: Satisfaction with prismatic correction is achieved in approximately 80% of all adult patients with diplopia when combining the causes.

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The synthesis and anion-recognition properties of two new porphyrin-functionalised [2]rotaxane host molecules are described. The rotaxane compounds are prepared via a chloride-anion-templated clipping strategy. (1)H NMR titration experiments demonstrate that the rotaxane host systems exhibit high binding affinities and general selectivities for chloride anions in DMSO-d(6) or CDCl(3)/CD(3)OD solvent systems.

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The design, synthesis, structure, and anion-binding properties of the first indolocarbazole-containing interlocked structure are described. The novel [2]rotaxane molecular structure incorporates a neutral indolocarbazole-containing axle component which is encircled by a tetracationic macrocycle functionalized with an isophthalamide anion recognition motif. (1)H NMR and UV-visible spectroscopies and X-ray crystallography demonstrated the importance of pi-donor-acceptor, CH.

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The surface covalent attachment of indolocarbazole axles enables anion templation to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral isophthalamide macrocycles from solution. The anion selectivity of this templating process can be monitored by a number of surface spectroscopic methods and shows subtle differences compared to the same process in solution. Though the fluxional and disordered nature of ethylene glycol extended axle adlayers prohibits detectable threading on the surface, rotaxane monolayers can be generated by a preassociation of the components and templating anion in solution.

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The first example of anion templated pseudorotaxane formation between two neutral components in solution and in surface assembled monolayers is described.

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