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Spherical cerium oxide nanoparticles and microsized rod-shaped and spindle-like CeO2 structures have been synthesized using a polyol method. When the duration of reaction and the concentration of cerium precursor are controlled, CeO2 products of different morphologies can be selectively produced. Results from XRD, XPS, SEM, and FT-IR measurements suggest that the CeO2 nanospheres are formed from the decomposition of the cerium precursor. Further reactions between the as-prepared CeO2 and ethylene glycol yield the rods/spindle-like cerium formate particles. These morphologies are preserved even after calcination. The order of band gap energy of these samples was found to be rod-shaped > spherical > spindle-like samples, as determined by the UV−Vis spectroscopic method. Compared to a nonoriented polycrystalline CeO2, these samples show an increase in band gap energy due to the quantum size effect. The higher catalytic activity on CO conversion in a spindle-like sample can be explained from the extent of Ce(IV) reduction and the oxygen vacancy.

A new approach for the fabrication of oriented TiO2/glass nanoflake arrays has been developed. The ceramic nanoflake array was formed on a glass substrate via a simple, low temperature, and one-step hydrothermally induced phase separation approach without using any templates or additives. The factors affecting the formation of ceramic nanoflakes were examined by various characterization techniques. The results showed that the leaching of the soluble phase from the glass surface through hydrothermal processes resulted in oriented uniform ceramic nanoflake arrays. Electron microscope observations revealed that the nanoflakes formed a continuous porous three-dimensional-network array with a large surface-to-volume ratio. In addition, an anatase TiO2 film was successfully coated onto the nanoflake array by the sol−gel method. The TiO2/glass nanoflake array exhibited high activity for the photocatalytic degradation of acetone and for photoinduced hydrophilic conversion. Such enhancements were attributed to the beneficial effects of the new continuous porous three-dimensional-interconnected nanoflake network and its surface geometrical nanostructure. The present approach provides a convenient route to modify a photocatalytic coating with a porous nano-architectured substrate. This opens extensive new opportunities in the design of semiconductor/ceramic nanostructural array thin films with unusual properties for future optical and electronic applications.

Light-harvesting macroporous channels have been successfully incorporated into a mesoporous TiO2 framework to increase its photocatalytic activity. This bimodal porous material was characterized by X-ray diffractometry in both low-angle and wide-angle ranges, N2 adsorption−desorption analysis, scanning and transmission electron microscopy, FT-IR, and diffuse reflectance spectroscopy. Ethylene photodegradation in gas-phase medium was employed as a probe reaction to evaluate the photocatalytic reactivity of the catalysts. The results reveal that sintering temperature significantly affects the structural stability and photocatalytic activity of titania. The catalyst which calcined at 350 °C possessed an intact macro/mesoporous structure and showed photocatalytic reactivity about 60% higher than that of commercial P25 titania. When the sample was calcined at 500 °C, the macroporous structure was retained but the mesoporous structure was partly destroyed. Further heating at temperatures above 600 °C destroyed both macro- and mesoporous structures, accompanied by a loss in photocatalytic activity. The high photocatalytic performance of the intact macro/mesoporous TiO2 may be explained by the existence of macrochannels that increase photoabsorption efficiency and allow efficient diffusion of gaseous molecules.

A new approach has been developed for the fabrication of visible light photocatalysts. Nanoclusters of MoS2 and WS2 are coupled to TiO2 by an in situ photoreduction deposition method taking advantage of the reducing power of the photogenerated electrons from TiO2 particles. The photocatalytic degradation of methylene blue and 4-chlorophenol in aqueous suspension has been employed to evaluate the visible light photocatalytic activity of the powders. The blue shift in the absorption onset confirms the size quantization of MS2 nanoclusters, which act as effective and stable sensitizers, making it possible to utilize visible light in photocatalysis. Quantum size effects alter the energy levels of the conduction and valence band edges in the coupled semiconductor systems, which favors the interparticle electron transfer. In addition, the coupled systems are believed to act in a cooperative manner by increasing the degree of charge carrier separation, which effectively reduces recombination.

Transparent zeolite-like mesoporous TiO2 nanocrystalline thin films with high photocatalytic activity were synthesized via a surfactant-templated method. The films were characterized by TGA−DTA, XRD, nitrogen adsorption, SEM, TEM, UV/vis, and FT-IR spectroscopy. The photocatalytic activity of the films was evaluated by photodecomposition of acetone in air at ambient conditions. It was found that thermal treatment resulted in surfactant elimination, framework solidification, as well as pore-wall crystallization of the mesoporous TiO2. The resulting zeolite-like mesoporous TiO2 nanocrystalline films had large specific surface areas (~100 m²/g), high porosity (~40%), extended band gap energy (~3.3 eV), tri-directional communicating pore systems, and enhanced photocatalytic activity. The optimum calcination temperature was found to be 500 °C, at which the film possessed a cubic ordered mesoporous structure and exhibited the highest photocatalytic activity. A comparison with a conventional TiO2 film (prepared from a sol−gel method) showed that the ordered mesoporous TiO2 nanocrystalline film (calcined at 500 °C) had over 2 times the specific photocatalytic activity as the conventional film. The high photocatalytic activity of zeolite-like mesoporous TiO2 thin films can be explained by the large specific surface area and the three-dimensionally connected mesoporous architecture.

We have previously reported that a series of 4-[4-(N-substituted (thio)carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives were potent and selective inhibitors of platelet-derived growth factor receptor (PDGFR) phosphorylation and demonstrated several biological effects such as suppression of neointima formation following balloon injury in rat carotid artery by oral administration. Here, we investigated structure−activity relationships of the 6,7-dimethoxyquinazolinyl moiety. In regard to 6,7-dimethoxy groups, ethoxy analogues showed potent activity (IC50 of 16b is 0.04 μM; IC50 of 17a is 0.01 μM) and further extension of the alkyl group reduced activity. Interestingly, methoxyethoxy (IC50 of 16j is 0.02 μM; IC50 of 17h is 0.01 μM) and ethoxyethoxy (IC50 of 17j is 0.02 μM) analogues showed the most potent activity, suggesting that the inserted oxygen atom significantly interacts with β-PDGFR. Among tricyclic quinazoline derivatives, the 2-oxoimidazo[4,5-e]quinazoline derivative 21a showed potent activity (IC50 = 0.10 μM). Regarding replacements of quinazoline by other heterocyclic rings, pyrazolo[3,4-d]pyrimidine (39a, IC50 = 0.17 μM) and quinoline (IC50 of 40a is 0.18 μM; IC50 of 40b is 0.09 μM) derivatives showed potent activity. Isoquinoline and some pyridopyrimidine derivatives were completely inactive; therefore, 1-aza has an important role. Also 7-aza and 8-aza substitution on the parent quinazoline ring has a detrimental effect on the interaction with β-PDGFR. We also demonstrated that the substituents on the quinazoline ring possess major consequences for metabolic polymorphism. Although there existed extensive metabolizers and poor metabolizers in Sprague−Dawley rats administrated 6,7-dimethoxyquinazoline derivatives (1b and 1c), 6-(2-methoxy)ethoxy-7-methoxyquinazoline analogue 16k showed no metabolic polymorphism.

Under ambient light illumination, silver nanoparticles can be synthesized by a triblock copolymer induced reduction of [Ag(NH3)2]⁺ ions in ethanol. Conventional chemical reducing agents, thermal treatment, and radiation sources are no longer necessary in this novel approach. A possible mechanism was proposed to explain the formation and stabilization of silver nanoparticles based on UV−vis absorption spectra and transmission electron microscopy results. This novel ambient light route has been successfully applied to deposit silver nanoclusters on TiO2. Silver nanoclusters of about 2 nm in size were found to strongly anchor to the TiO2 nanoparticles with high dispersion. The resulting silver-coated TiO2 material with optimal silver loading showed enhanced photocatalytic and bactericidal activities compared to the uncoated TiO2. The reasons for the enhancements of the activities were discussed.

A surfactant-templated approach was used to synthesize phosphated mesoporous titanium dioxide by incorporating phosphorus from phosphoric acid directly into the framework of TiO2. The resulting materials were characterized by XRD, nitrogen adsorption, TEM, XPS analysis, UV−vis spectroscopy, FT-IR spectroscopy, and isoelectric point measurements. The surface area of phosphated mesoporous TiO2 exceeded 300 m²/g after calcination at 400 °C. It was found that the incorporation of phosphorus could stabilize the TiO2 framework and increase the surface area significantly. This stabilization is attributed to two reasons:  the more complete condensation of surface Ti−OH in the as-prepared sample and the inhibition of grain growth of the embedded anatase TiO2 by the interspersed amorphous titanium phosphate matrix during thermal treatment. Both pure and phosphated mesoporous TiO2 show significant activities on the oxidation of n-pentane. The higher photocatalytic activity of phosphated mesoporous TiO2 can be explained by the extended band gap energy, large surface area, and the existence of Ti ions in a tetrahedral coordination.

Enhancement of the photocatalytic activity of sol−gel-derived TiO2 thin films by a simple treatment with trifluoroacetic acid (TFA) was investigated. The thin films were characterized with N2 adsorption, Fourier transform infrared spectroscopy, UV−visible spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, X-ray diffraction, atomic force microscopy, and differential thermal analysis/thermogravimetry analysis. The photocatalytic activity of the thin films was evaluated by the photocatalytic decomposition of acetone in air. The results show that TFA is chemisorbed on the surface of the TiO2 films as a trifluoroacetate complex. The photocatalytic activity of modified TiO2 thin films is higher than that of unmodified TiO2 thin films, and the modified film treated at 250 °C shows the highest activity. This is ascribed to the fact that the TFA complex bound on the surface of TiO2 acts as an electron scavenger and, thus, reduces the recombination of photogenerated electrons and holes. The enhancement is only temporary, however, as the TFA eventually decomposes under the strong oxidizing environment of photocatalysis. Reaction schemes are proposed to explain the interaction between TFA and TiO2. This detailed study may shed some light on the future development of more durable enhanced photocatalysts.

A stable mesoporous network formed by nanoparticles of ZnS was achieved by an ultrasound-mediated fabrication method. The ZnS nanoparticles were generated in situ during the sonication, and dodecylamine was used as the structure-directing agent. All the synthesized materials were characterized using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), electron diffraction, energy dispersive analysis of X-rays, Fourier transform infrared, UV−vis diffuse reflectance spectroscopy, and thermal analyses. After the template extraction, the obtained mesoporous ZnS possessed a high surface area of 210 m²/g with an average pore diameter of 28 Å. HRTEM analysis revealed a mesostructure consisting of closely spaced ZnS nanocrystallites of ~3 nm size. The individual nanocrystallites showed typical lattice spacings corresponding to the cubic phase of ZnS. The existence of ZnS particles in a compact structure resulted in a dramatic increase in the thermal stability of the cubic phase. As revealed from optical absorption measurements, the ZnS nanoparticles exhibited quantum-size effect with a blue shift in the band gap. Finally, a systematic analysis was carried out to find the role of ultrasound on the supramolecular assembling process that leads to the generation of a mesostructure.

Novel silicone surfactant was first used as the template to prepare mesostructured silica films with unusual lamellar structure. Complex mesostructured silica films can be obtained using the mixture of silicone surfactant and cetyltrimethylammonium bromide (C16TAB: CH3(CH2)15N⁺(CH3)3Br^-) as the surfactant in conjunction with the sol−gel dip-coating process. The results show that silicone surfactants favor the formation of lamellar structure. Highly ordered long-range lamellar structure has the largest lattice constant known for lamellar materials to date reported. Moreover, the hexagonal mesophase can be easily created in layered silica walls just by adding C16TAB in the silicone surfactant templating system. The lamellar mesophase and the hexagonal mesoporosity in the walls were separately templated from silicone-based surfactant and C16TAB in the mixed surfactant templating systems, and thus hierarchically ordered silica formed. The examples presented supply strong evidence that oxide mesophases are governed by supramolecular chain configuration; i.e., unrestricted chain configuration (Si−O−Si chain in silicone surfactant) is responsible for the formation of the zero-curvature lamellar silica mesophase and restrictive chain configuration (C−C−C chain in C16TAB) for the high-curvature hexagonal mesophase, even their existing in a one-pot system.

In this study mesoporous TiO2 with a bicrystalline (anatase and brookite) framework was synthesized directly under high-intensity ultrasound irradiation. This was carried out separately, both with and without the use of a triblock copolymer. Without thermal treatment, mesoporous TiO2 was formed by the agglomeration of monodispersed TiO2 sol particles. The resulting materials were characterized by XRD, TEM, nitrogen adsorption, TGA/DTA, and FTIR. The use of ultrasound irradiation assisted in the formation of the brookite phase. As the content of the brookite phase increased, the pore size and the crystalline sizes of anatase and brookite became larger when the triblock copolymer was used in the synthesis. Both as-prepared samples exhibited better activities than the commercial photocatalyst P25 in the degradation of n-pentane in air. The degradation rate of mesoporous TiO2 synthesized in the presence of triblock copolymer was about two times greater than that of P25. The high activities of the mesoporous TiO2 with a bicrystalline framework can be attributed to the combined effect of three factors:  high brookite content, high surface area, and the existence of mesopores.

4-[4-(N-Substituted (thio)carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives such as KN1022 are potent inhibitors of the phosphorylation of platelet derived growth factor receptor (PDGFR). Structure activity relationships in the (thio)urea moiety, the phenyl ring itself, the linker between these two moieties, and the piperazine moiety were investigated. The role of the linker was found to be quite different, where ureas yielded decreasing activity, while thioureas provided increasing activity. Cyanoguanidine as a bioisostere of thiourea and related dicyanovinyl or nitrovinyl groups were not suitable for potent activity. A hydrogen atom on the (thio)urea moiety was essential for activity. Stereochemistry was also important for inhibition of PDGFR phosphorylation. Through the modification of these moieties, benzylthiourea analogues with a small substituent on the 4-position and the 3,4-methylenedioxy group (KN734/CT52923) were found to be optimal for selective and potent activity. Replacement of the phenyl ring by heterocycles improved aqueous solubility without loss of activity and kinase selectivity. Introduction of a methyl group on 5-position of the piperazine ring and replacement by homopiperazine reduced inhibitory activity. An efficient synthetic method was also developed for 2-pyridylurea-containing analogues, via carbonylation of 2-aminopyridine with N,N‘-carbonyldiimidazole. A potent analogue, KN734, inhibited smooth muscle cell proliferation and migration induced by platelet derived growth factor-BB (PDGF-BB) and suppressed neointima formation following balloon injury in rat carotid artery by oral administration. Therefore, 4-[4-(N-substituted (thio)carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives may be expected to have potential as therapeutic agents for the treatment of restenosis.

A novel and simple method for preparing highly photoactive nanocrystalline F^--doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution. The prepared F^--doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F^- doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F^--doped TiO2 samples exhibited stronger absorption in the UV−visible range with a red shift in the band gap transition. The photocatalytic activity of F^--doped TiO2 powders prepared by this method exceeded that of Degussa P25 when the molar ratio of NH4F to H2O was kept in the range of 0.5−3.

We have previously found that the 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazolines can function as potent and selective inhibitors of platelet-derived growth factor receptor (PDGFR) phosphorylation. A series of highly potent, specific, orally active, small molecule kinase inhibitors directed against members of PDGFR receptor have been developed through modifications of the novel quinazoline template I. Systematic modifications in the A-bicyclic ring and D-rings of protype I were carried out to afford potent analogues, which display IC50 values of <250 nM in cellular βPDGFR phosphorylation assays. An optimized analogue in this series, 75 (CT53518), inhibits Flt-3, βPDGFR, and c-Kit receptor phosphorylation with IC50 values of 50−200 nM, whereas 15−20-fold less potent activity against CSF-1R was observed. This analogue also inhibits autophosphorylation of Flt-3 ligand-stimulated wild-type Flt-3 and a constitutively activated Flt-3/internal tandem duplication (ITD) with IC50 values of 30−100 nM. Through this optimization process, 75 was found to be metabolically stable and has desirable pharmacokinetic properties in all animal species studied (F% > 50%, T1/2 > 8 h). Oral administration of 75 promotes mice survival and significantly delayed disease progression in a Flt-3/ITD-mediated leukemia mouse model and shows efficacy in a nude mouse model of chronic myelomonocytic leukemia.

A new series of 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives were found to show potent and selective inhibition of platelet-dervied growth factor (PDGF) receptor phosphorylation. In this exploration of the structure−activity relationships (SARs) of the prototype inhibitor KN1022, the 4-nitrophenylurea moiety was probed. We found that 4-substitution on the phenyl ring was optimal and the introduction of more than two substituents on the phenyl ring decreased activities. Bulky substituents on the phenyl ring enhanced activities. Thiourea analogues were also prepared, and the SARs were found to be slightly different from those of the urea derivatives. Through this research, we obtained some potent KN1022 derivatives such as 4-(4-methylphenoxy)phenyl (36, IC50 0.02 μmol/L), 4-tert-butylphenyl (16, IC50 0.03 μmol/L), and 4-phenoxyphenyl (21, IC50 0.08 μmol/L) analogues, which had almost a 10-fold increase in activity against KN1022. These potent compounds retained their high selectivity against the PDGF receptor family similar to KN1022. We also observed that these compounds could inhibit the PDGF-BB-induced proliferation of porcine vascular smooth muscle cells without cell toxicity almost at the same IC50 values observed for PDGF receptor phosphorylation. To evaluate the biological effects in vivo, we selected some analogues on the basis of the measurement of the plasma drug concentration after oral administration to rats. Oral administration of the 4-chlorophenyl (6), 4-bromophenyl (9), or 4-isopropoxyphenyl (20) analogue to Sprague−Dawley rats (30 mg/kg, twice daily) resulted in significant inhibition (24−38%) of neointima formation in the carotid artery of the balloon catheter deendothelialized vessel in the rats. Therefore, 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives, which are potent inhibitors of PDGFR phosphorylation, may be expected to represent a new therapeutic approach for the treatment of various aspects of atherosclerosis and other cellar proliferative disorders.

Thermal treatment in air has a marked influence on the adsorption of oxygen and the photocatalytic activities of TiO2 (P25) for the oxidation of acetone in air. The photoactivity of TiO2 increases with the increase of thermal treatment temperature until 400 °C, above which more rutile is formed. On the basis of the photocatalytic performance of TiO2 thermally treated in a vacuum and the results of polycrystalline X-ray diffraction analysis, BET surface area, adsorption oxygen measurements and ESR spectra, the increase in photoactivity can be attributed to a catalyst surface with more adsorbed oxygen. This would generate more superoxide anion radicals under UV irradiation, resulting in a better separation of photoexcited electrons and holes.

CD44, an integral membrane glycoprotein expressed by many cell types, serves as the principal transmembrane hyaluronate receptor and might be a determinant of metastatic and invasive behaviour in carcinomas. The generation of CD44 splice variants might be linked closely with gastric carcinoma tumorigenesis and differentiation. Some studies have reported that the magnitude of CD44 variant synthesis at the protein level correlates with lymph node metastasis. A number of studies have examined the possible mechanism of involvement of the CD44 variant in tumour metastasis. Most studies have reported that the regulation of CD44 binding to hyaluronate results from glycosylation of variably spliced exons. Direct hyaluronate binding studies of CD44 V4-V7 isoforms transfected into the human gastric carcinoma cell line, SC-M1, have indicated that the V4-V7 isoforms themselves, in addition to glycosylation, can alter hyaluronate binding.

We have reported previously that a chimeric platelet-derived growth factor receptor (PDGFR) possessing the ligand binding domain of the alpha PDGFR and the intracellular domain of the beta PDGFR (alpha 340 beta 342 R) was markedly more efficient than the wild type alpha PDGFR (alpha RWT) in its ability to enhance PDGF-A transforming activity in NIH/3T3 fibroblasts. To determine the region within the cytoplasmic domain of beta PDGFR that confers this higher transforming activity, we generated several additional alpha/beta PDGFR chimerae. When a chimeric PDGFR possessing the first 933 amino-terminal amino acids from the alpha PDGFR and the final 165 amino acids from the carboxyl-terminal of the beta PDGFR (alpha 933 beta 942 R) was cotransfected with the PDGF-A gene into NIH/3T3 cells, it showed a similar high efficiency to enhance PDGF-A chain transforming activity as alpha 340 beta 342 R. However, when chimeric PDGFRs in which either the kinase insert domain (alpha beta RKI) or the last 79 amino acids from the carboxyl-terminal end of the beta PDGFR (alpha 1024 beta 1028 R) were substituted into alpha PDGFR sequences were cotransfected with PDGF-A, they showed similar low efficiencies in enhancing transforming activity as the alpha RWT. These results predicted that the 86 amino acids following the tyrosine kinase 2 domain of beta PDGFR (amino acid residues 942-1027) were responsible for the higher transforming activity of beta PDGFR. To confirm this finding, we next constructed a chimera in which amino acid residues 942-1028 of the beta PDGFR (alpha beta 942-1028R) were substituted for those in the alpha PDGFR. Cotransfection experiments indicated that alpha beta 942-1028R increased transforming activity of PDGF-A to similar extent as the alpha 933 beta 942R, or alpha 340 beta 342R. Therefore, our findings define a critical domain within the noncatalytic region of beta PDGFR intracellular domain that confers the higher focus forming activity mediated by the beta PDGFR.

The purpose of this study was to bacterially express, purify, and refold combinations of the extracellular immunoglobulin (Ig)-like domains (2-3, 1-3, and 1-5) of the human alpha-platelet-derived growth factor receptor (alpha PDGFR) to characterize molecular interactions with its ligand, platelet-derived growth factor (PDGF). The far UV circular dichroism spectroscopy of the alpha-PDGFR extracellular domains (ECDs) revealed a predominantly beta-sheet protein, with a structure consistent with folded Ig-like domains. The addition of PDGF-BB to these ECD types changed the conformation of all three types with a decrease in mean residue ellipticity in the following rank order: 1-5 = 1-3 > 2-3. In striking contrast, addition of PDGF-AA to these ECD types markedly changed the conformation of ECD 2-3, by an increased mean residue ellipticity but no changes were observed for ECDs 1-3 and 1-5. PDGF-AA bound to the immobilized ECD types 2-3, 1-3, and 1-5 at concentrations of 20, 11, and 7.5 nM, respectively. In contrast, PDGF-BB bound the ECD types 2-3, 1-3, and 1-5 at concentrations of 3, 3, and 2.2 nM, respectively. Scatchard analysis of binding studies using labeled ECDs indicated that PDGF-BB bound ECD 1-3 and ECD 2-3 with KD values of 74 and 72 nM, respectively. While, PDGF-AA bound ECD 1-3 and ECD 2-3 with KD values of 33 and 87 nM, respectively. Therefore, our results indicated that the loss of ECD 1 impaired the binding affinity of alpha PDGFR ECD 1-3 toward PDGF-AA without having a similar effect on PDGF-BB binding. Together all of our data suggest that ECD 1 is differentially required for proper orientation of PDGF-AA but not PDGF-BB binding determinant within ECDs 2 and 3.

To investigate the function of protein kinase C (PKC)-delta, we mutated its ATP binding site by converting the invariant lysine in the catalytic domain (amino acid 376) to an arginine. Expression vectors containing wild type and mutant PKC-delta cDNAs were generated either with or without an influenza virus hemagglutinin epitope tag. After expression in 32D cells by transfection, the PKC-delta ATP binding mutant (PKC-delta K376R) was not able to phosphorylate itself or the PKC-delta pseudosubstrate region-derived substrate, indicating that PKC-delta K376R was an inactive enzyme. PKC activity was inhibited by 67% in 32D cells coexpressing both PKC-delta wild type (PKC-delta WT) and PKC-delta K376R when compared to 32D cells expressing only PKC-delta WT. Mixture of PKC-delta WT and PKC-delta K376R kinase sources in vitro also reduced the enzymatic activity of PKC-delta WT. These results suggest that PKC-delta K376R competes with PKC-delta WT and inhibits PKC-delta WT phosphorylation of its in vitro substrate. While PKC-delta WT overexpressed in 32D cells demonstrated 12-O-tetradecanoylphorbol-13-acetate (TPA)-dependent translocation from the cytosolic to the membrane fraction, PKC-delta K376R was exclusively localized in the membrane fraction even prior to TPA stimulation. Unlike PKC-delta WT which was phosphorylated on tyrosine residue(s) only after TPA treatment, PKC-delta K376R was constitutively phosphorylated on tyrosine residue(s). Although exposure of PKC-delta WT transfectants to TPA induced 32D monocytic differentiation, the 32D/PKC-delta K376R transfectants were resistant to TPA-induced differentiation. Thus, expression of active PKC-delta is required to mediate 32D monocytic differentiation in response to TPA stimulation.

To determine the molecular basis for the transforming function of platelet-derived growth factor (PDGF)-A in NIH/3T3 cells, we have constructed chimerae consisting of the extracellular domain of the human CSF-1R (fms) linked to the cytoplasmic domain of the alpha PDGF receptor (alpha R) containing a series of deletion or point mutations. The ability of fms/alpha R chimerae to mediate CSF-1-dependent anchorage-independent growth, focus formation, and chemotaxis of NIH/3T3 cells was then examined. Our results provide evidence that a domain encompassing amino acid residues 977-1024 of the alpha PDGFR is required for ligand-dependent focus formation, but not chemotaxis or anchorage-independent growth, and that tyrosine residues within this domain constitute the major binding site for phospholipase C gamma. Therefore, our findings suggest that: (i) the focus forming function of alpha PDGFR correlates well with the ability of the receptor to bind phospholipase C gamma, and (ii) the mechanism of focus formation mediated by alpha PDGFR may be distinguished from that required for chemotaxis or anchorage-independent growth.

Solid solutions of Ti1-xZrxO2 (0.00 < x ≤ 0.10) exhibit higher photocatalytic activity than pure anatase TiO2 for the degradation of acetone in air. The activity increases with increase of zirconium substitution in the TiO2 lattice until nominal x = 0.075. The results of polycrystalline X-ray diffraction analysis, BET surface area, XPS, and zeta potential measurements show that the increase in activity is related to changes in the lattice parameters and cell volume. A mechanism is proposed suggesting that lattice O^2- and O^- species ionosorbed on surface are responsible for the increased activity. The synthesis of the solid solutions and the effects of zirconium addition on phase constitution, lattice parameters, BET surface area, and surface hydroxyl groups are also discussed.