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Biomedical subjects

Thomas M Fyles

Publications and source records attributed to Thomas M Fyles.

7 recordsLinked to original sources
PubMed2007

Simple bis-thiocarbono-hydrazones as sensitive, selective, colorimetric, and switch-on fluorescent chemosensors for fluoride anions.

Bis-thiocarbono-hydrazones are found to be a class of sensitive, selective, ratiometric, and colorimetric chemosensors for anions such as fluoride (F(-)) or acetate (Ac(-)). The sensitivities, or the binding constants of the sensors with anions, were found to be strongly dependent on the substituents appended on the pi-conjugation framework, the delocalization bridge CH==N, the aromatic moiety, and the hetero atom in the C==X group (X=O, S) of the sensors. Single-crystal structures and (1)H NMR titration analysis shows that the --CH==N-- moiety is a hydrogen-bond donor, and it is proposed that an additional CHF hydrogen bond is formed for the sensors in the presence F(-). A sensor bearing anthracenyl groups is demonstrated as a switch-on fluorescent chemosensor for F(-) and Ac(-). The recognition of F(-) in acetonitrile (MeCN) by a sensor with nitrophenyl substituents is tolerant to MeOH (MeCN/MeOH=10:1, v/v) and water (MeCN/H(2)O=30:1, v/v); at these solvent ratios the absorption intensity of the sensor-F(-) complex solution at maximal absorption wavelength was attenuated to half of the original value in pure MeCN.

Absorption↗
PubMed2006

Solid-phase synthesis of oligoester ion channels.

A simple synthesis of oligoesters from TBDMS-protected-beta- and THP-protected-omega-hydroxycarboxylic acids using a solid-phase synthesis protocol is reported. Procedures were optimized for the efficient production of ion channel candidates in high purity with minimal purification. The product oligoesters were evaluated for ion transport activity using a fluorescent dye/vesicle assay. Oligoesters produced by this strategy show structure-dependent activity; the most active compounds are closely comparable to previously known oligoesters, but are available at a fraction of the synthetic effort.

Combinatorial Chemistry Techniques↗
PubMed2006

Columnar self-assembled ureido crown ethers: an example of ion-channel organization in lipid bilayers.

The self-assembly of ureido crown-ether derivatives has been examined in homogeneous solution, in the solid state, and in planar bilayer membranes. The self-assembly is driven by head-to-tail hydrogen bonding between the urea functional groups. Dimers and higher oligomers are formed in CDCl3 solution as assessed by the change in the ureido NH chemical shift as a function of concentration. Single-crystal X-ray diffraction shows that an antiparallel association of the ureas produces columnar channels composed of face-to-face crown ethers. Powder X-ray diffraction studies also show the presence of a minor phase based upon a parallel urea association leading to an alternative columnar arrangement of the crown ethers. In bilayer membranes at low concentration of ureido crown ether added, membrane disruption is observed together with rare single-channel openings, but at higher concentration, a rich array of interconverting channel conductance states is observed. The channel results are interpreted as arising from discreet stacks of ureido crown ethers where the transport of cations would occur via the macrocycles, admixed with larger pores formed by association of the crown ether headgroups around a central large pore.

Journal Article↗
PubMed2004

A ditopic fluorescent sensor for potassium fluoride.

The addition of potassium fluoride 'switches on' the fluorescence of sensors and while potassium chloride and bromide cause no fluorescence change; the fluorescence can be 'switched off' by removing the potassium cation from the benzocrown ether receptors of sensors and through the addition of [2.2.2]-cryptand and restored by the addition of the potassium cation as potassium chloride.

Boron Compounds↗
PubMed2002

Synthesis and membrane activity of a bis(metacyclophane)bolaamphiphile.

The synthesis of macrocyclic tetraesters from 5-substituted isophthalic acids and 1,8-octane diol gave macrocylic metacyclophanes with the axially symmetric positions differentially protected. Dimer bis(metacyclophane)bolaamphiphiles proved to be extremely insoluble, but one derivative was shown to have significant membrane activity. Very high continuous conductance and the formation of discrete single-ion channels were both observed, depending on how the compound was incorporated into the bilayer membrane.

Biological Transport↗