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Results for “Hybrid catalyst”

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PubMed2026

Design of an innovative framework based hybrid catalyst for simultaneous and sensitive monitoring of food additive and preservative of vanillin and nitrite in direct samples.

As vanillin (VAN) and nitrite (NIT) contamination in the food chain poses substantial threats to environmental and public health, rapid and portable detection is essential. The present study presents the first electrochemical sensor report based on a hybrid composite of Ni-TPA-MOF and MoS2/Co3O4. The oxidation of VAN and NIT exhibited sharp peaks and less over-potential on Ni-TPA-MOF/MoS2/Co3O4/GCE than on control electrode surfaces. On modified composite electrode surfaces, pH and scan rate were investigated for VAN and NIT. Further, the oxidation current exhibited high linearity at VAN and NIT concentrations of 5 nM-1000 μM and 3 nM-1250 μM, with detection limits of 0.102 nM and 0.073 nM (S/N = 3). We also applied anti-interfering ability (five/ten-fold excess of co-interfering compounds) and practical tests to various food-based real samples, with high recoveries of 98.85-102.41%. This study highlights the catalytic properties of Ni-TPA-MOF/MoS2/Co3O4 and demonstrates the sensor as a promising tool for food safety.

Benzaldehydes↗

PubMed1991

Photo-activation of resin cements through porcelain veneers.

The purpose of this study was to determine the effects of porcelain opacity, chemical catalyst, and exposure time on polymerization of light-activated resin-composite cements. Samples of microfill and hybrid composites, with and without catalyst (i.e., dual-cure and visible-light-activated), were polymerized by exposure to visible light through porcelain discs of different opacities. Microhardness testing (KHN) was used to compare degree of cure for each material at various exposure times. Porcelain opacity did not significantly affect hardness. However, the results indicated that a chemical catalyst and prolonged curing times might be essential for clinical success.

Analysis of Variance↗

PubMed2026

Tele-Oncology in the Post-Pandemic Era: Clinical Integration, Access Disparities and Medico-Legal Accountability.

PURPOSE OF THE REVIEW: Tele-health has evolved from a marginal tool confined to rural populations and selected follow-up programs into a structurally integrated component of modern cancer care. Prior to COVID-19, its adoption was constrained by regulatory fragmentation, non-uniform reimbursement, and licensure barriers. This narrative review evaluates the evolutionary integration of tele-health in oncology post-COVID-19, examines digital disparities across patient populations, and addresses the medico-legal implications of this integration, with the objective of providing a comprehensive and clinically actionable framework for the governance of virtual oncology care. RECENT FINDINGS: The pandemic acted as a global catalyst, driving telehealth to over 50% of oncology outpatient encounters in some settings, before stabilising post-pandemic at approximately 10-20% of consultations within hybrid care models. Evidence supports meaningful clinical benefits - improved access to specialist services, reduced travel burden, and sustained continuity of care - with outcomes comparable to in-person care in postoperative follow-up, symptom monitoring, and survivorship. However, persistent disparities in device availability, connectivity, and digital literacy disproportionately affect older, rural, and socioeconomically disadvantaged patients, raising the risk that geographic inequalities are replaced by technological ones. From a medico-legal standpoint, the remote modality does not modify the applicable standard of care, yet restricted physical examination and reliance on patient-reported data introduce risks of diagnostic delay and incomplete clinical assessment, with direct implications for professional liability, data protection under HIPAA and GDPR, cross-border licensure, and multi-party accountability across physicians, institutions, and technology providers. Tele-oncology has become a permanent structural feature of modern cancer care, offering demonstrable benefits in access, continuity, and patient satisfaction. Yet its integration has been uneven, its governance remains fragmented, and its medico-legal landscape is still evolving. Realising the full potential of virtual oncology care - equitably and safely - requires coherent regulatory frameworks, sustained investment in digital infrastructure, and explicit attention to the populations at greatest risk of being left behind.

Humans↗

PubMed1992

A new approach to template purification for sequencing applications using paramagnetic particles.

A new method using traditional hybridization methodology, coupled with the new magnetic particle technology, has been developed for DNA purification, specifically for sequencing applications. The method is similar to the reverse hybridization blot system; however, a specific oligonucleotide probe was attached to the paramagnetic particle instead of a sheet membrane. The target DNA containing the complementary sequence of the probe hybridizes to the probe that is attached to the bead and is then magnetically removed from solution, washed and collected. This system eliminates the need of organic extractions and precipitation/concentration steps. The entire hybridization-purification system can be done in a 1.5-ml microcentrifuge tube making the method ideal for automation. M13 phage clones were purified with this method, both by manual means and by using the CATALYST 800 Molecular Biology LabStation fitted with a prototype magnetic station, and then sequenced. DNA sequencing results obtained with this system were reproducible and gave excellent length of read with low background.

Base Sequence↗

PubMed1991

Effect of 2-(methacryloxy)ethyl phenyl hydrogen phosphate on adhesion to dentin.

A variety of methacrylate-based materials has been developed with the capacity of adhering to dentin. This study investigated the effectiveness of 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) for bonding 5% phenyl-P in methyl methacrylate (MMA) to dentinal surfaces. Polymerization of the phenyl-P/MMA monomer was initiated by partially oxidized tri-n-butyl borane catalyst (TBB). The mean tensile bond strength of 5% phenyl-P in MMA to dentin that was pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride, abbreviated as 10-3, was found to be 10.5 MPa. Scanning electron microscope examination demonstrated the formation of a transitional or "hybrid" layer of resin-reinforced dentin, created by the intermingling and entanglement of polymerized resin with collagen bundles exposed by dentin pre-treatment with 10-3, an effective remover of the dentinal smear layer. This "hybrid" layer or zone was essential for high tensile bond strength to be attained. Phenyl-P was found to be effective in promoting monomer diffusion and impregnating monomer into demineralized dentinal surfaces. The formation of the "hybrid" layer of resin-reinforced dentin followed in situ resin polymerization initiated by partially oxidized tri-n-butyl borane (TBB). Ferric (Fe3+) ions deposited on dentinal surfaces from the 10-3 solution also acted to improve monomer diffusion and entanglement with demineralized dentin, and facilitated the formation of the "hybrid" layer/zone.

Acid Etching, Dental↗

PubMed1992

Two metal-dependent steps in the biosynthesis of Scenedesmus obliques plastocyanin. Differential mRNA accumulation and holoprotein formation.

The accumulation of the interchangeable electron transfer catalysts plastocyanin and cytochrome c6 (cyt c6) in Scenedesmus obliquus is reciprocally regulated by the amount of copper ions in the medium. In copper-deficient cells, plastocyanin levels are severely reduced, whereas cyt c6 levels are high. Western blot analysis indicates that neither pre-apoplastocyanin nor apoplastocyanin accumulate to significant extents in copper-deficient Scenedesmus cells, and time course studies indicate that upon provision of copper salts to copper-deficient cells, the accumulation of plastocyanin to the levels maintained in copper-sufficient cells takes about 12-24 h. By 1) Northern hybridization analysis of Scenedesmus obliquus mRNA and 2) in vitro translation of polyadenylylated mRNA followed by immunoprecipitation of a 19.2-kilodalton precursor to plastocyanin, we demonstrate that the regulation of plastocyanin synthesis by copper must occur primarily at the level of mRNA accumulation. These results suggest that copper-dependent stimulation of holoplastocyanin accumulation requires de novo synthesis of the pre-apoprotein and contradict the conclusion of Bohner, H., Bohme, H., and Boger, P. (1981) FEBS Lett. 131, 386-388 that high levels of apoplastocyanin and a precursor to plastocyanin accumulate in copper-deficient Scenedesmus cells. We note also that although metal ions other than copper (e.g. silver) insert into Scenedesmus obliquus plastocyanin in vitro, synthesis of holoplastocyanin in vivo is specific for copper versus silver or mercury as it is in Chlamydomonas reinhardtii. Finally, the very different electrophoretic mobility and immunoreactivity of apoplastocyanin compared with holoplastocyanin suggests rather significant differences in structure between the copper-protein and the metal-free protein.

Blotting, Northern↗

PubMed1979

Preparation of the bifunctional enzyme ribonuclease-deoxyribonuclease by cross-linkage.

Protease-free bovine pancreatic deoxyribonuclease (DNase) (1.6 X 10(-4) mmol) was thiolated on the NH2 groups with N-acetyl-DL-homocysteine thiolactone (2.4 X 10(-2) mmol) at pH 10.5 with imidazole (2.4 X 10(-2) mmol) as the catalyst in the presence of 4,4'-dithiodipyridine (4.2 X 10(-2) mmol). The product obtained after 16 h at 4 degrees C, 2-acetamido-4-(4'-dithiopyridyl)butyryl-DNase, isolated by gel filtration, contained an average of 0.87 +/- 0.13 mol of mixed disulfide per mol of DNase. Ribonuclease (RNase) was thiolated in a similar manner, but under N2 in the absence of 4,4'-dithiodipyridine. The protein N-acetylhomocysteinyl-RNase contained on the average 0.94 +/- 0.11 mol of sulfhydryl groups per mol of RNase. The coupling of RNase ot DNase was accomplished by thiol-disulfide interchange at pH 6.2 and 25 degrees C for 90 min. The hybrid enzyme (yield 25--33%, based upon the DNase derivative used) was freed from unreacted DNase, RNase, and homodimers by gel filtration, affinity chromatography, and salting-out chromatography. The purified enzyme contained one molecule each of DNase and RNase and hydrolyzed thymus deoxyribonucleic acid (DNA) and yeast or transfer ribonucleic acid (RNA) with 75 and 40% of the efficiencies, respectively, of the parent enzymes. The RNA strand of the hybrid substrate, phage f1 DNA-[3H]RNA, prepared from phage DNA with RNA polymerase, was hydrolyzed rapidly by the hybrid enzyme but was not hydrolyzed by RNase alone. A conjugate of the two enzymes offers the possibility in vivo of delivering two enzymes that differ in size, charge, and biological function to the same site at the same time.

Animals↗

PubMed1992

Molecular cloning and functional characterization of chicken cathepsin D, a key enzyme for yolk formation.

Upon receptor-mediated endocytosis of very-low-density lipoprotein (VLDL) and vitellogenin into growing chicken oocytes, the protein moieties of these lipoproteins are proteolytically cleaved. Unlike the complete lysosomal degradation in somatic cells, enzymatic ligand breakdown in oocytes generates a characteristic set of polypeptides, which enter yolk storage compartments for subsequent utilization by the embryo. Here, we demonstrate directly that the catalyst for the intraoocytic processing of both apolipoprotein B and vitellogenin is cathepsin D. The enzyme was purified from oocytic yolk, preovulatory follicle homogenates, and liver by affinity chromatography. When plasma VLDL and vitellogenin were incubated with the purified enzyme, fragments indistinguishable from those found in yolk were generated from both precursors under identical, mildly acidic conditions. Amino-terminal sequencing of the pure enzyme demonstrated 88% identity with mammalian cathepsin Ds over 34 residues. On the basis of this information, a full-length clone specifying chicken preprocathepsin D was isolated from a chicken follicle cDNA library by screening with a human cathepsin D probe. Whereas previous studies have demonstrated that the receptors for lipoproteins in somatic cells and oocytes, respectively, of the chicken are the products of different genes, Southern and Northern blot hybridization experiments showed that the enzymes expressed in oocytes and liver are the product of a single gene, giving rise to a 3.3-kb transcript. The primary structure of the 335-residue mature protein suggests a high degree of conservation of known crucial features of aspartyl proteases; however, the absence of the so-called processing region and of an aromatic residue in a region thought to partake in catalysis raise questions with possible evolutionary implications.

Amino Acid Sequence↗

PubMed1991

Cytochrome P-450 monooxygenase systems in aquatic species: carcinogen metabolism and biomarkers for carcinogen and pollutant exposure.

High levels of polynuclear aromatic hydrocarbon (PAH) carcinogens commonly occur in aquatic systems where neoplasms arise in fish and other animals. Enzymes that transform PAHs can act in initiating these diseases and can indicate the contamination of fish by carcinogens and other pollutants. Cytochrome P-450 has similar roles in activating PAH carcinogens in fish and mammalian species. PAHs and many chlorinated hydrocarbons, e.g., polychlorinated biphenyls (PCBs) induce a form of cytochrome P-450 in fish that is the primary catalyst of PAH metabolism. The induction of this P-450 in fish can accelerate the disposition of hydrocarbons, but can also enhance the formation of carcinogenic derivatives of PAHs. Invertebrates have lower rates of PAH metabolism than fish. These rates are not obviously inducible by exposure to PAHs or PCBs. The lower rates of foreign compound metabolism contribute to higher pollutant residue levels in bivalve mollusks (clams, mussels, etc.) than in fish and may limit the involvement of some procarcinogens (requiring activation) in disease processes in invertebrates. The induction of P-450 forms can indicate the exposure of fish to PAHs, PCBs, and other toxic compounds. This is not restricted to carcinogens. Environmental induction has been detected in fish from contaminated areas by use of catalytic assay, antibodies to fish P-450, and cDNA probes that hybridize with P-450 messenger RNA. Application of these methods can provide sensitive biological monitoring tools that can detect environmental contamination of fish by some carcinogens and tumor promoters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗