pH-dependent Si-fluorescein hypochlorous acid fluorescent probe: spirocycle ring-opening and excess hypochlorous acid-induced chlorination.

We report the synthesis and characterization of a fluorescent probe (Hypo-SiF) designed for the detection of hypochlorous acid (HOCl) using a silicon analogue of fluorescein (SiF). The probe is regulated in an "off-on" fashion by a highly selective thioether spirocyclic nonfluorescent structure that opens to form a mixture of fluorescent products in the presence of HOCl. Over a range of pH values, the probe reacts with a stoichiometric amount of HOCl, resulting in a mixture of two pH-dependent fluorescent species, a SiF disulfide product and a SiF sulfonate product.

Design and investigation of a series of rhodamine-based fluorescent probes for optical measurements of pH.

A series of structurally similar fluorescent probes (1-4), synthesized from rhodamine B, were designed to optically measure pH. Each probe had a unique "off-on" response as the solution went from basic to acidic. Probes 1-3 exhibited a spirocyclic quenching of the pyronin B fluorophore, whereas probe 4 was quenched by PET from the amine moiety.

Computational studies on response and binding selectivity of fluorescence sensors.

Using a computational strategy based on density functional theory calculations, we successfully designed a fluorescent sensor for detecting Zn(2+) [J. Phys. Chem.

Separation of peptides with polyionic nanosponges for MALDI-MS analysis.

A polymer brush consisting of 70% poly(N-isopropylacrylamide) (PNIPAAM) and 30% polymethacrylic acid (PMAA) was synthesized from gold substrates with a "grafting from" AIBN-type free-radical initiator. Fractionation of two peptides, bradykinin and buccalin, was accomplished in less than 120 s by placing a 30 pM (pH approximately 6.2) droplet onto the polymer brush substrate.

Computational prediction and experimental evaluation of a photoinduced electron-transfer sensor.

An approach is presented for the design of photoinduced electron-transfer-based sensors. The approach relies on the computational and theoretical prediction of electron-transfer kinetics based on Rehm-Weller and Marcus theories. The approach allows evaluation of the photophysical behavior of a prototype fluorescent probe/sensor prior to the synthesis of the molecule.

A hydrogen-bonded heterodimer of 1-(4-hexyloxyphenyl)pyridin-4(1H)-one with 4-cyanobenzoic acid.

The two components of the title heterodimer, C17H21NO2.C8H5NO2, are linked end-to-end via O-H..

Hydrogen-bonded 1:1 adduct of 1,1'-(p-phenylene)dipyridin-4(1H)-one with terephthalic acid.

Cocrystallization of 1,1'-(p-phenylene)dipyridin-4(1H)-one (4,4'-dpy) and terephthalic acid (tpa) affords the hydrogen-bonded 1:1 title complex, C16H12N2O2.C8H6O4. Both molecules are symmetrically disposed about independent symmetry centers.

N,N',N''-Tris(p-methoxyphenyl)phosphoric triamide.

The title compound, C(21)H(24)N(3)O(4)P, is a self-complementary hydrogen-bond (HB) building unit, with (P=)O as the primary HB acceptor and N-H as the HB donor. Each of the four crystallographically distinct and nearly parallel molecules of the unit cell has a net dipole moment along the P=O bond direction and all of the dipoles are directed in the same general crystallographic direction. Head-to-tail N-H.

Field control of the surface electroclinic effect in chiral smectic-A liquid crystals.

The surface electroclinic effect, which causes an azimuthal deviation of the layer normal from the surface rubbing direction in cells of chiral smectic- A liquid crystals, can be eliminated (and even reversed) by applying an electric field during cooling from the isotropic phase. The observed dependence of layer orientation on field strength leads to a model in which the surface electroclinic tilt results from an effective surface electric field. The experiements suggest a general method for controlling the azimuthal layer alignment of chiral smectic cells.