16,386 research outputs found
Synthetic routes to Bis-Calix [n]areness : a thesis presented in partial fulfilment of the requirements for the degree of Masterate of Science in Chemistry at Massey University
The literature procedures for the targeted syntheses of p-tert-butylcalix[4]arene, p-tert-butylcalix[5]arene, p-tert-butylcalix[6]arene, p-tert-butylcalix[7]arene, and p-tert-butylcalix[8]arene have been repeated successfully. In the case of p-tert-butylcalix[4]arene, alterations led to a less capricious procedure, synthesis of the pure product directly and in higher yield. The residual xylene and toluene solutions from the targeted p-tert-butylcalix[8]arene preparation were utilised to obtain workable quantities of the rare calix[5]- and calix[7]arenes, a protocol that is far simpler and less time-consuming than the low-yielding targeted synthesis of these compounds. Dealkylation of p-tert-butylcalix[n]arenes is best accomplished at 30°C in 0.16-0.05 molL−¹ toluene solution. The insolubility of calix[8]arene in all common organic solvents is expected to limit its synthetic use. Two new protocols have been devised for the highly selective mono-O-alkylation of calixarenes 4 through 8. This work represents the realisation of the first selective functionalisation methods that are applicable to the calixarene family, and also the first selective functionalisation of a calix[7]arene. These findings will lead to more efficient synthesis of multiple calixarenes (cf. Chapter 3) and may allow for a better understanding of the reasons for selectivity in calixarene-O-alkylations. We have been able to synthesise a variety of bis-calixarenes by two different routes. Glaser-Hay coupling allowed the synthesis of symmetrical diyne bridged bis-calix[4, 6 and 8]arenes in high yield. Extension of the first general mono-O-alkylation procedure for calixarenes has made it possible to synthesise hom o-bis-calixarenes in good yield in one step from the parent calixarenes. The unexpected formation of monobromoxylyl calixarenes allows the prospect of the synthesis of hetero-bis-calixarenes under more forcing conditions. Most importantly this allows us to further explore the chemistry of bis-calixarenes by making them readily available (in large quantities) for more elaborate syntheses
A survey of chemical information systems
A survey of the features, functions, and characteristics of a fairly wide variety of chemical information storage and retrieval systems currently in operation is given. The types of systems (together with an identification of the specific systems) addressed within this survey are as follows: patents and bibliographies (Derwent's Patent System; IFI Comprehensive Database; PULSAR); pharmacology and toxicology (Chemfile; PAGODE; CBF; HEEDA; NAPRALERT; MAACS); the chemical information system (CAS Chemical Registry System; SANSS; MSSS; CSEARCH; GINA; NMRLIT; CRYST; XTAL; PDSM; CAISF; RTECS Search System; AQUATOX; WDROP; OHMTADS; MLAB; Chemlab); spectra (OCETH; ASTM); crystals (CRYSRC); and physical properties (DETHERM). Summary characteristics and current trends in chemical information systems development are also examined
A new global gas hydrate budget based on numerical reaction-transport modeling and a novel parameterization of Holocene and Quaternary sedimentation
This study provides new estimates for the global methane hydrate inventory based on reaction-transport modeling [1]. A multi-1D model for POC degradation, gas hydrate formation and dissolution is presented. The model contains an open three-phase system of two solid (organic carbon, gas hydrates), three dissolved (methane, sulfates, inorganic carbon) and one gaseous (free methane) compounds. The reaction module builds upon the kinetic model of POC degradation [2] which considers a down-core decrease in reactivity of organic matter and the inhibition of methane production via accumulation of metabolites in sediment pore fluids.
Global input grids have been compiled from a variety of oceanographic, geological and geophysical data sets including a parameterization of sedimentation rates in terms of water depth (Holocene) and distance to continents (Quaternary).The world's total gas hydrate inventory is estimated at 1.74 x 1013 m3 – ~2 x 1015 m3 CH4 (STP) or, equivalently, 8.3 – ~900 Gt of methane carbon. The first value refers to the present day conditions using the relatively low Holocene sedimentation rates; the second value corresponds to a scenario of higher Quaternary sedimentation rates along continental margins. This increase in the POC input could be explained by re-deposition process at the continental rise and slope due to erosion of continental shelf sediments during glacial times.
Our results show that in-situ POC degradation is at present not an efficient hydrate forming process. Significant hydrate deposits are more likely to have formed at times of higher sedimentation during the Quaternary or/and as a consequence of active upward fluid transport
Bioorganic chemistry. Laboratory classes
УЧЕБНО-МЕТОДИЧЕСКИЕ ПОСОБИЯХИМИЯ ОРГАНИЧЕСКАЯБИООРГАНИЧЕСКАЯ ХИМИЯИНОСТРАННЫЕ СТУДЕНТЫBIOORGANIC CHEMISTRYLABORATORY CLASSESЛАБОРАТОРНЫЕ ЗАНЯТИЯПособие написано в соответствии с типовой учебной программой по биоорганической химии для студентов высших медицинских учреждений образования и предназначено для освоения дисциплины "Биоорганическая химия" студентами 1 курса, обучающимися по специальности "Лечебное дело" на английском языке
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General method for prediction of thermal conductivity for well-characterized hydrocarbon mixtures and fuels up to extreme conditions using entropy scaling
A general and efficient technique is developed to predict the thermal conductivity of well-characterized hydrocarbon mixtures, rocket propellant (RP) fuels, and jet fuels up to high temperatures and high pressures (HTHP). The technique is based upon entropy scaling using the group contribution method coupled with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. The mixture number averaged molecular weight and hydrogen to carbon ratio are used to define a single pseudo-component to represent the compounds in a well-characterized hydrocarbon mixture or fuel. With these two input parameters, thermal conductivity predictions are less accurate when the mixture contains significant amounts of iso-alkanes, but the predictions improve when a single thermal conductivity data point at a reference condition is used to fit one model parameter. For eleven binary mixtures and three ternary mixtures at conditions from 288 to 360 K and up to 4,500 bar, thermal conductivities are predicted with mean absolute percent deviations (MAPDs) of 16.0 and 3.0% using the two-parameter and three-parameter models, respectively. Thermal conductivities are predicted for three RP fuels and three jet fuels at conditions from 293 to 598 K and up to 700 bar with MAPDs of 14.3 and 2.0% using the two-parameter and three-parameter models, respectively
Inhibition by small-molecule ligands of formation of amyloid fibrils of an immunoglobulin light chain variable domain.
Overproduction of immunoglobulin light chains leads to systemic amyloidosis, a lethal disease characterized by the formation of amyloid fibrils in patients' tissues. Excess light chains are in equilibrium between dimers and less stable monomers which can undergo irreversible aggregation to the amyloid state. The dimers therefore must disassociate into monomers prior to forming amyloid fibrils. Here we identify ligands that inhibit amyloid formation by stabilizing the Mcg light chain variable domain dimer and shifting the equilibrium away from the amyloid-prone monomer
Unraveling the functional role of the orphan solute carrier, SLC22A24 in the transport of steroid conjugates through metabolomic and genome-wide association studies.
Variation in steroid hormone levels has wide implications for health and disease. The genes encoding the proteins involved in steroid disposition represent key determinants of interindividual variation in steroid levels and ultimately, their effects. Beginning with metabolomic data from genome-wide association studies (GWAS), we observed that genetic variants in the orphan transporter, SLC22A24 were significantly associated with levels of androsterone glucuronide and etiocholanolone glucuronide (sentinel SNPs p-value <1x10-30). In cells over-expressing human or various mammalian orthologs of SLC22A24, we showed that steroid conjugates and bile acids were substrates of the transporter. Phylogenetic, genomic, and transcriptomic analyses suggested that SLC22A24 has a specialized role in the kidney and appears to function in the reabsorption of organic anions, and in particular, anionic steroids. Phenome-wide analysis showed that functional variants of SLC22A24 are associated with human disease such as cardiovascular diseases and acne, which have been linked to dysregulated steroid metabolism. Collectively, these functional genomic studies reveal a previously uncharacterized protein involved in steroid homeostasis, opening up new possibilities for SLC22A24 as a pharmacological target for regulating steroid levels
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Entropy scaling based viscosity predictions for hydrocarbon mixtures and diesel fuels up to extreme conditions
An entropy scaling based technique using the Perturbed-Chain Statistical Associating Fluid Theory is described for predicting the viscosity of hydrocarbon mixtures and diesel fuels up to high temperatures and high pressures. The compounds found in diesel fuels or hydrocarbon mixtures are represented as a single pseudo-component. The model is not fit to viscosity data but is predictive up to high temperatures and pressures with input of only two calculated or measured mixture properties: the number averaged molecular weight and hydrogen to carbon ratio. Viscosity is predicted less accurately when the mixture contains high concentrations of iso-alkanes and cyclohexanes. However, it is shown that predictions for these mixtures are improved by fitting a third parameter to a single viscosity data point at a chosen reference state. For hydrocarbon mixtures, viscosity is predicted with average mean absolute percent deviations (MAPDs) of 12.2% using the two-parameter model and 7.3% using the three-parameter model from 293 to 353 K and up to 1000 bar. For two different diesel fuels, viscosity is predicted with an average MAPD of 21.4% using the two-parameter model and 9.4% using the three-parameter model from 323 to 423 K and up to 3500 bar
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