The importance of temperature and viscosity effects for surfactant adsorption measurements made using the electrochemical quartz crystal microbalance

The measurement of adsorbed surfactant is important to fields such as corrosion inhibition, metal cleaning, and separation technologies. The electrochemical quartz crystal microbalance (EQCM) is an important tool that can be used to measure adsorbed surfactant. However, such measurements are subject to significant temperature and viscosity effects that must be appropriately considered. This paper discusses the effect of temperature and viscosity on EQCM measurements in solution environments and the ability of the EQCM to measure surfactant adsorption.     

Replacement of the phosphorodiester linkages of RNA with guanidinium linkages: the solid-phase synthesis of ribonucleic guanidine

[reaction: see text] Replacement of the negatively charged phosphodiester linkages of RNA with positively charged guanidinium linkages provides the polycationic ribonucleic guanidine (RNG). RNG is anticipated to bind strongly to target DNA/RNA through the specific interactions of nucleobases and the attractive electrostatic interactions of backbones. Preparation of building blocks and the solid-phase synthesis of RNG are reported. Both trimeric and pentameric uridyl RNG have been synthesized.     

Effect of Organic Ligands Used in Sol-Gel Process on the Formation of Mullite

The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate (TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)₂(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG>PD>MPD. When Al(OBu)₂(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG>BD>DEME>MPD. Between the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)₂(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility between the silica and alumina.     

Optimal use of the recurrence relations for the evaluation of molecular integrals over Cartesian Gaussian basis functions

We consider the tree search problem for the recurrence relation that appears in the evaluation of molecular integrals over Cartesian Gaussian basis functions. A systematic way of performing tree search is shown. By applying the result of tree searching to the LRL2 method of Lindh, Ryu, and Liu (LRL) (J. Chem. Phys., 95 , 5889 1991), which is an auxiliary function-based method, we obtain significant reductions of the floating point operations (FLOPS) counts in the K⁴ region. The resulting FLOPS counts in the K⁴ region are comparable up to [dd|dd] angular momentum cases to the LRL1 method of LRL, currently the method requiring least FLOPS for [dd|dd] and higher angular momentum basis functions. For [ff|ff], [gg|gg], [hh|hh], and [ii|ii] cases, the required FLOPS are 24, 40, 51, and 59%, respectively, less than the LRL1 method in the K⁴ region. These are the best FLOPS counts available in the literature for high angular momentum cases. Also, there will be no overhead in either the K² or K⁰ region in implementing the present scheme. This should lead to more efficient codes of integral evaluations for higher angular momentum cases than any other existing codes. © 1993 John Wiley & Sons, Inc.     

19F- and 1H-NMR spectra of tetrafluoroethylene–propylene copolymers

High resolution 94-MHz ¹⁹F- and 100-MHz ¹H-NMR spectra were measured on a series of tetrafluoroethylene (TFE)-propylene (P) copolymers having a range of composition (TFE/P molar ratio = 37/63–55/45) and polymerized at different temperatures (?23, 25 and 65°C). The spectra were analyzed in relation to copolymer compositions. The assignment of ¹⁹F resonance in terms of tetrads proposed previously was confirmed, and the tentative assignment of ¹H resonances was proposed in terms of triads. The spectra thus interpreted revealed the sequence distribution of the copolymers. Copolymer compositions calculated from NMR spectra and elemental analysis agreed rather well with each other. Monomer reactivity ratios were calculated from the sequence distributions and compared with those obtained from the elemental analysis. It was observed that highly alternating copolymers are obtained in this system over a wide range of monomer composition at lower temperatures and that a deviation from alternancy increases slightly with rising polymerization temperature.     

On the use of methyl substituted poly(vinylnaphthalene) as a reversible singlet oxygen carrier

Poly(1,4-dimethyl-6-vinylnaphthalene) and poly(1,2,4-trimethyl-6-vinylnaphthalene) react with singlet oxygen to give corresponding endoperoxide polymers which on warming generate singlet oxygen efficiently. Singlet oxygenations by the use of these polymers have been described.     

Characteristics of excited-state intermediates of TiO2–Y-Zeolite and MCM41 encapsulating photosensitive molecules: design of new photocatalysts

Some photosensitive molecules, such as p-N,N′-dimethylaminobenzoic acid (DMABA), Nile Red, heteropolytungstic acid (H₃PW₁₂O₄₀, HPA) and metalloporphyrins, have been entrapped onto nano-scale pores or channels of TiO₂-modified Y-Zeolite (TiO₂-Y-Zeolite) and MCM41 (TiO₂-MCM41) and their excited-state intermediates have been characterized in terms of the excited-state dynamics by using laser spectroscopic techniques. Through these studies, it has been found that the photo-induced electrons are generated from the intramolecular charge transfer (ICT) state of DMABA, Nile Red or metalloporphyrin (MnTPP(Cl)), followed by transferring to the TiO₂-Y-Zeolite or TiO₂-MCM41 more efficiently as compared to the bulk TiO₂, NaY-Zeolite or MCM41. The efficient photoinduced interfacial electron transfer causes the rapid formation of radicals of those photosensitive molecules (a few tens ps). It has been also found that these photophysical properties can be applied to develop the new photocatalyst as observed by the efficient photocatalytic activities of the DMABA or Nile Red-entrapped TiO₂-Y-Zeolites for the photoreduction of an azo-dye such as Methyl Orange in water. On the other hand, in case of HPA-entrapped TiO₂-Y-zeolite, the electron generated from the excited-state TiO₂ is transferred to HPA, followed by formation of the reduction product, heteropoly blue (HPB) which is also generated by UV irradiation of HPA. This electron transfer is analogous to the Z-scheme mechanism of plant photosynthetic systems showing two photon reactions. Because of this photoelectron transfer mechanism, the HPA-entrapped TiO₂-Y-zeolite has demonstrated the synergistic enhancement of the photocatalytic decomposition of Methyl Orange and hydrogen generation from photolysis of water.     

Effect of polymer excipients on the enzyme activity of lyophilized bilirubin oxidase and beta-galactosidase formulations

The effects of excipients on the protein stability during lyophilization as well as the storage stability of lyophilized bilirubin oxidase (BO) and beta-galactosidase (GA) formulations were studied using four polymer excipients: dextran, polyvinylalcohol (PVA), poly(acrylic acid) (PAA), and alpha, beta-poly(N-hydroxyethyl)-L-aspartamide (PHEA). Denaturation of BO and GA during lyophilization largely depended on the excipient used. Dextran appeared to cause severe damage to proteins, whereas PHEA protected proteins effectively from denaturation. Storage stability of BO and GA formulations also depended on the excipients, such that the formulations containing dextran and PAA were relatively unstable. Storage stability was improved by absorption of a small amount of water for all the formulations studied. Absorption of a larger amount of water, however, decreased the storage stability of the formulations containing PVA, PAA or PHEA. In contrast, the storage stability of formulations containing dextran did not decrease noticeably with increasing water. This may be because formulations containing dextran have a higher glass transition temperature than formulations containing PVA, PAA or PHEA when a large amount of water is absorbed.     

Dynamic identification of phosphopeptides using immobilized metal ion affinity chromatography enrichment, subsequent partial beta-elimination/chemical tagging and matrix-assisted laser desorption/ionization mass spectrometric analysis

The enrichment of phosphopeptides using immobilized metal ion affinity chromatography (IMAC) and subsequent mass spectrometric analysis is a powerful protocol for detecting phosphopeptides and analyzing their phosphorylation state. However, nonspecific binding peptides, such as acidic, nonphosphorylated peptides, often coelute and make analyses of mass spectra difficult. This study used a partial chemical tagging reaction of a phosphopeptide mixture, enriched by IMAC and contaminated with nonspecific binding peptides, following a modified beta-elimination/Michael addition method, and dynamic mass analysis of the resulting peptide pool. Mercaptoethanol was used as a chemical tag and nitrilotriacetic acid (NTA) immobilized on Sepharose beads was used for IMAC enrichment. The time-dependent dynamic mass analysis of the partially tagged reaction mixture detected intact phosphopeptides and their mercaptoethanol-tagged derivatives simultaneously by their mass difference (-20 Da for each phosphorylation site). The number of new peaks appearing with the mass shift gave the number of multiply phosphorylated sites in a phosphopeptide. Therefore, this partial chemical tagging/dynamic mass analysis method can be a powerful tool for rapid and efficient phosphopeptide identification and analysis of the phosphorylation state concurrently using only MS analysis data.     

Relative binding affinities of alkali metal cations to

The binding affinity and selectivity of a new ionophore, [1(8)]starand (1), toward alkali metal cations in methanol were examined through NMR titration experiments and free energy perturbation (FEP) and molecular dynamics simulations. The preference was determined to be K(+) > Rb(+) > Cs(+) > Na(+) > Li(+) in both FEP simulations and NMR experiments. The FEP simulation results were able to predict the relative binding free energies with errors less than 0.13 kcal/mol, except for the case between Li(+) and Na(+). The cation selectivity was rationalized by analyzing the radial distribution functions of the M-O and M-C distances of free metal cations in methanol and those of metal-ionophore complexes in methanol.