Fluorescence-labeled peptide pI markers for capillary isoelectric focusing

Nineteen fluorescent pH standards or pI markers ranging pH 3.64-10.12 were developed for use in capillary isoelectric focusing using laser-induced fluorescence detection. Tetra- to tridecapeptides containing one cysteine residue were designed to focus sharply at their respective isoelectric points by including amino acids that contain charged side chains, the pKa values of which are close to the corresponding pI values. An iodoacetylated derivative of tetramethylrhodamine was coupled to the thiol group of cysteine to yield fluorescent pI markers. The pI values of the labeled peptides were precisely determined after isoelectric focusing on polyacrylamide gel slabs by direct measurement of the pH of the focused bands. The markers were subjected to capillary isoelectric focusing for 10-15 min in coated capillaries under conditions of low electroosmosis and were detected by means of a scanning laser-induced fluorescence detector down to a level of subpicomolar range. The markers permitted the calibration of a wide-range pH gradient formed in a capillary by fluorescence detection for the first time and should facilitate the development of highly sensitive analytical methods based on a combination of capillary isoelectric focusing and laser-induced fluorescence detection.     

Preparation of NbN fibres by nitridation of sol-gel derived Nb2O5 fibres

Nbn fibres were prepared by nitriding sol-gel-derived Nb₂O₅ fibres. Precursor niobium-oxide-gel fibres were obtained by spinning viscous sots prepared through acid-catalysed hydrolysis of niobium penta-ethoxide, Nb(OC₂H₅)₅. It was found that the spinnability of the sols depended on the water/alkoxide and the acid/alkoxide ratios. The niobium-oxide-gel fibres thus obtained were converted to niobium nitride by heat-treatment in a NH₃ gas above 800°C. Characterization of these fibres was carried out using X-ray powder diffraction, Auger electron spectroscopy and scanning electron microscopy. The nitride fibres obtained at 1050°C were mostly of stoichiometric -NbN phase, and they showed a transition to a superconducting state at around 11 K.     

The photochemical reaction applied to a multiply hybridized water-splitting system

The photochemical reaction expressed by

$\text{2Fe}{}^{\mathrm{2+}}\text{+ I}{}^{\mathrm{?}}{}_3\text{+ light →2FE}{}^3\text{+ 3I}{}^{\mathrm{?}}$

is applied to the water-splitting cycles hybridized by photochemical and electrochemical reactions (Yokohama Mark 5), and by photochemical, electrochemical, and thermochemical reactions (Yokohama Mark 6).The theoretical expression for the conversion efficiency of light energy to chemical energy is derived using the reaction dynamics, and the factor which maximizes it and the Gibbs free energy change ΔG are studied.The magnitude of stored energy depends on the intensity of light, the concentration of the reactants, and the kind of anions existing in the solution.Considering the reactivity of the photochemical process and the retardation of the back reaction, the SO₄^2? system yields a large value of ΔG.A value of 15–20% is finally obtained for the efficiency of the photochemical conversion process.     

Sol-gel preparation and properties of TiO2-P2O5 bulk glasses

Monolithic transparent and colorless, or Ti³⁺-free TiO₂-P₂O₅ glasses containing very large amounts of TiO₂ (up to 93 mol%) were successfully prepared by heat-treating the xerogels, which were made from titanium tetraisopropoxide and triethyl phosphate, through the sol-gel reaction. The density and refractive index n_632.8 nm of the sol-gel-derived glasses were higher than the melt-derived glasses of the corresponding compositions. The glasses of TiO₂ content of larger than 80 mol% seemed somewhat porous, but n_632.8 nm of these glasses was very high as 2.2-2.3. Higher density and higher n_632.8 nm than the melt-derived glasses were considered to be due to more abundance of six-fold coordinated Ti⁴⁺ ions.     

Preparation of nylon 66/mesoporous molecular sieve composite under high pressure

Nylon 66/mesoporous molecular sieve (pore diameter: 2.7 nm) composites were prepared by annealing mixtures of nylon 66 and mesoporous molecular sieve (FSM) powders under high pressures and high temperature (FSM content: 0–60 wt %; pressure: 0.5–30 MPa; temperature: 300°C; time: 1 h). X‐ray diffraction and TEM measurements indicated the presence of the pores of FSM in the composite. Above 2 MPa, nylon 66 was charged in the pores of FSM. The fraction of the charged nylon 66 increased with pressure and was independent of the FSM content (pressure: 2–30 MPa; fraction of charged nylon 66: 54–66%). The infrared spectrum of the composite showed the bands based on Si O, C H, N H, CO. DSC measurement indicated that the heat of fusion of nylon 66 crystallite in the FSM pores was low compared with that of nylon 66. The composites prepared above 2 MPa were found to be superior in storage modulus to nylon 66. The modulus increased with an increase in the fraction of charged nylon 66 and the amount of FSM. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3254–3258, 1999     

Interaction between anionic molecule and colored copolypeptide microspheres

Summary Tryptophan (Trp) residues within copoly(L-glutamic acid-co-L-Trp) (GAT) form a tricyclic structure when treatment with trifluoroacetic acid (TFA) and show reversible color change from yellow (above pH 8.0) to red (below pH 7.0) when the nitrogen atom in an indole ring dissociates positively in the neutral pH region. The interaction between TFA-treated GAT (GAT-T) and an anionic molecule such as warfarin was investigated using VIS and fluorescence spectrophotometry. Trp residues within GAT-T were found to interact with warfarin electrostatically besides hydrophobic interaction resulting in a color change from red to yellow. Release behavior of warfarin from GAT-T microspheres (MS) was also investigated. Binding amount and retention time of warfarin in GAT-T MS were found to be superior to those in untreated GAT MS. Received: 22 January 1999/Revised version: 29 March 1999/Accepted: 31 March 1999     

Shape measurements of mirror surfaces with a lateral-shearing interferometer during machine running

A common path lateral-shearing interferometer with a minimum number of optical components has been developed. Because the interferometer is little affected by mechanical vibrations and air turbulence, it can be mounted on an ultraprecision lathe and can be used to measure the shapes of workpieces. A plane parallel glass plate is used to shear the wavefront under test in the interferometer. To analyze the interference fringes obtained by the interferometer precisely, a fringe-scanning method using a slight tilt of the glass plate is used. Zone plates that are computer-generated holograms are used to measure spherical and aspherical surfaces with the interferometer. A spherical and a parabolic concave mirror were measured with the interferometer. The spherical mirror was also measured by a Fizeau interferometer to compare the error with that measured by the lateral-shearing interferometer. The experimental results agreed well with those measured by the lateral-shearing interferometer.     

Fluorine uptake into human enamel around fluoride-containing dental materials during cariogenic pH cycling

Using PIGE (Proton Induced Gamma Emission) technique at TARRI (Takasaki Advanced Radiation Research Institute), Japan, we measured fluorine (F) uptake into the tooth enamel around two fluoride-containing materials during caries progression using pH cycling. Class V cavities in extracted human teeth were drilled and filled with fluoride-containing materials (i.e. “Fuji IX” (FN) and “UniFil flow with MEGA bond” (UF)) and a non-fluoride-containing material (i.e. “SOLARE with MEGA bond” (SO)). Three 120 μm longitudinal sections including the filling material were obtained from each tooth. In order to simulate daily acid attack occurring in the oral cavity, the pH cycling (pH 6.8–4.5) was carried out for 1, 3 and 5 weeks, separately. After pH cycling, the caries progression in all specimens was observed using transverse microradiography (TMR). The F and calcium distributions of the specimens were evaluated using PIGE and PIXE techniques. The F distribution of the specimens clearly showed the F uptake from FN into enamel adjacent to the filling material, while the F uptakes from UF and SO were not detected. For UF, the MEGA bond (non-fluoride-containing) between the tooth and UniFil flow interfered with the F absorption into the tooth. For FN, the amount of F uptake into the subsurface enamel increased during pH cycling. The amount of F uptake in 5-week pH cycling had significantly higher value compared to those in 1- and 3-week pH cycling. For UF and SO, there were no significant differences between the different durations of pH cycling.Among fluoride-containing materials, there were some differences in the F uptake with increased pH cycling, which could possibly lead to obtaining difference in clinical performance. The data obtained using PIGE and PIXE techniques were useful in understanding the benefit of fluorine by means of fluoride-containing material for preventing caries.