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171.
Jake E. Doiron Dr. Christina A. Le Dr. John Bacsa Prof. Gary W. Breton Prof. Kenneth L. Martin Prof. Stephen G. Aller Prof. Mark Turlington 《ChemMedChem》2020,15(18):1720-1730
Although the 1,2,3-triazole is a commonly used amide bioisostere in medicinal chemistry, the structural implications of this replacement have not been fully studied. Employing X-ray crystallography and computational studies, we report the spatial and electronic consequences of replacing an amide with the triazole in analogues of cystic fibrosis drugs in the VX-770 and VX-809 series. Crystallographic analyses quantify subtle differences in the relative positions and conformational preferences of the R1 and R2 substituents attached to the amide and triazole bioisosteres. Computational studies derived from the X-ray data highlight the improved hydrogen bonding donor and acceptor capabilities of the amide in comparison to the triazole. This analysis of the spatial and electronic differences between the amide and 1,2,3-triazole will inform medicinal chemists as they consider using the triazole as an amide bioisostere. 相似文献
172.
This study involved the use of an amphipathic graft copolymer, poly(methyl methacrylate-co-2-hydroxypropyl methacrylate)–graft–polyoxyethylene, as a stabilizer in the emulsion polymerization of methyl methacrylate. The stabilizing effectiveness of this graft copolymer was studied as a function of its chemical structure. It was found that the stabilizing effectiveness of the graft copolymer was independent of the molecular weight of the backbone within the investigated range of 4 × 103 g/mol to 2 × 104 g/mol. In all cases, stable emulsion polymerizations of methyl methacrylate were observed. Effective stabilization also occurred when the graft moieties possessed a molecular weight of either 2 × 103 g/mol or 5 × 103 g/mol. However, the stabilizing effectiveness was found to be dependent on the amount of polyoxyethylene (POE) contained in the graft copolymer. In this case, graft copolymers possessing 67% by weight POE were poor stabilizers, but ones with 85% POE were very good stabilizers. Moreover, the graft copolymers were found to be superior stabilizers as compared to POE homopolymers. 相似文献
173.
Phosphatidyl choline is a major lung surfactant. Insufficient development of the surfactant in neonates is often associated
with the Respiratory Distress Syndrome. The concentration and fatty acid composition of phosphatidyl choline have not been
studied in the subcellular organelles of the developing lung. This study has investigated the development of the concentration
and fatty acid composition of phosphatidyl choline in subcellular fractions of 28-day and 30-day fetal and maternal New Zealand
rabbit lungs. The concentration of total phospholipids in lamellar bodies increased four to five fold from 28-day fetus to
30-day fetus which, in turn, was similar to the maternal level. Total phospholipid content increased only about 50% in mitochondria
and microsomes. The percentage of phosphatidyl choline among total phospholipids in lamellar bodies increased successively
from 60% at 28 days gestation to 84% at 30 days gestation and leveled at 84% in maternal lamellar bodies. Microsomal PC increased
steadily from 52% in the 28-day fetus to 65% in the adult. Analysis of the fatty acid composition of phosphatidyl choline
in lamellar bodies confirmed 16∶0 as the major fatty acid, and its content remained constant from 28 days gestation to adult.
In contrast, the content of 16∶0 of the microsomal phosphatidyl choline decreased with increasing gestation. Changes of several
unsaturated fatty acid components were observed in both lamellar bodies and microsomes in the developing lungs. Maturational
development of phosphatidyl choline is reflected in an increase in the concentration of this surfactant, particularly in lamellar
bodies, and possibly in remodeling of fatty acid composition in both lamellar bodies and microsomes. 相似文献
174.
Gary J. Blomquist Charles L. Soliday Barbara A. Byers Joyce W. Brakke Larry L. Jackson 《Lipids》1972,7(5):356-362
Wax esters of secondary alcohols constitute 18–20% of the cuticular lipid extract ofMelanoplus packardii and 26–31% of the cuticular lipids ofMelanoplus sanguinipes. The total number of carbons in the wax esters range from 37–54 with 41 predominating in both species. The fatty acids ofM. packardii wax esters are 16∶0, 18∶0, 14∶0, 20∶0 and 12∶0 in decreasing quantity. The fatty acids ofM. sanguinipes wax esters are 18∶0, 20∶0, 16∶0 22∶0, 14∶0, 19∶0 and 17∶0 in decreasing quantity. The secondary alcohols from the wax esters
ofM. packardii are C25, C23 and C27 in decreasing quantity, and the secondary alcohols of theM. sanguinipes are C23, C25, C21, C27, C24, C22 and C26 in decreasing quantity. Each secondary alcohol consists of two to four isomers with the hydroxyl group located near the center
of the chain.
Montana Agriculture Experiment Station, Journal Series No. 332. 相似文献
175.
Harold N. Evin Gary Jacobs Javier Ruiz-Martinez Uschi M. Graham Alan Dozier Gerald Thomas Burtron H. Davis 《Catalysis Letters》2008,122(1-2):9-19
Doping Pt/ceria catalysts with the Group 1 alkali metals was found to lead to an important weakening of the C–H bond of formate
and methoxy species. This was demonstrated by a shift to lower wavenumbers of the formate and methoxy ν(CH) vibrational modes
by DRIFTS spectroscopy. Li and Na-doped Pt/ceria catalysts were tested relative to the undoped catalyst for low temperature
water–gas shift and methanol steam reforming using a fixed bed reactor and exhibited higher catalytic activity. Steaming of
formate and methoxy species pre-adsorbed on the catalyst surface during in-situ DRIFTS spectroscopy suggested that the species
were more reactive for dehydrogenation steps in the catalytic cycle for the Li and Na-doped catalysts relative to undoped
Pt/ceria. However, with increasing atomic number over the series of alkali-doped catalysts, the stability of a fraction of
the carbonate species was found to increase. This was observed during TPD-MS measurements of the adsorbed CO2 probe molecule by a systematic increase of a high temperature peak for a fraction of the CO2 desorbed. This result indicates that alkali-doping is an optimization problem—that is, while improving the dehydrogenation
rates of methoxy and formate species, the carbonate intermediate stability increases, making it difficult to liberate the
CO2. Infrared spectroscopy results of CO adsorbed on Pt and ceria suggest that the alkali dopant is located on, and electronically
modifies, both the Pt and ceria components. The results not only lend further support to the role that methoxy and formate
species play as intermediates in the catalytic mechanisms, but also provide a path forward for improving rates by means other
than resorting to higher noble metal loadings. 相似文献
176.
Abstract: It remains important to establish the stability of anthocyanins throughout commercial processing in order to maintain the bioactivity of the processed food/s. The present study aimed to assess the recovery and formation of anthocyanins and their free phenolic acid degradation products during the commercial processing of blackcurrant juice concentrate. A bench‐scale processing model was also established to allow for alteration of predefined parameters to identify where commercial processes could be modified to influence anthocyanin yield. No significant loss in anthocyanins was observed throughout the commercial processing of blackcurrants, from whole berry through milling, to pectin hydrolysis and sodium bisulphite addition (P ≥ 0.7). No significant loss in anthocyanins was observed following the subsequent processing of pressed juice, through pasteurization, decantation, filtration, and concentration (P ≥ 0.9). Similarly, the bench‐scale model showed no significant losses in anthocyanin content except during pasteurization (22%± 0.7%, P < 0.001). In the full‐factorial Design of Experiment model analysis, only sodium bisulphite concentration had an impact on anthocyanin recovery, which resulted in an increase (23% to 27%; P < 0.001) in final anthocyanin concentration. No phenolic degradation products (free protocatechuic acid or gallic acid derived from cyanidin and delphinin species, respectively) were identified in any processed sample when compared to authentic analytical standards, analyzed by ultra‐performance liquid chromatography DAD. Practical Application: This article provides crucial data directly applicable to commercial juice processing, such as improving anthocyanin yield and practical considerations for anthocyanin stability and degradation. This aspect is particularly pertinent considering the current commercial interest in anthocyanin‐derived phenolic acids and their health‐related benefits. Further research and development targets in the area of commercial juice product development are identified. 相似文献
177.
Nicole J. Gaudette Gary J. Pickering 《Critical reviews in food science and nutrition》2013,53(5):464-481
The functional foods sector represents a significant and growing portion of the food industry, yet formulation of these products often involves the use of ingredients that elicit less than desirable oral sensations, including bitterness. Promising new functional ingredients, including polyphenolics, may be more widely and readily employed in the creation of novel functional foods if their aversive bitter taste can be significantly reduced. A number of approaches are used by the industry to improve the taste properties and thus the acceptance of conventional foods that elicit excessive bitterness. This article reviews the most commonly employed techniques, including the use of bitter-modifying additives, which may prove useful for successfully introducing new functional ingredients into this rapidly growing sector. 相似文献
178.
Multifunctional iron-carbon nanocomposites through an aerosol-based process for the in situ remediation of chlorinated hydrocarbons 总被引:1,自引:0,他引:1
Zhan J Kolesnichenko I Sunkara B He J McPherson GL Piringer G John VT 《Environmental science & technology》2011,45(5):1949-1954
Spherical iron-carbon nanocomposites were developed through a facile aerosol-based process with sucrose and iron chloride as starting materials. These composites exhibit multiple functionalities relevant to the in situ remediation of chlorinated hydrocarbons such as trichloroethylene (TCE). The distribution and immobilization of iron nanoparticles on the surface of carbon spheres prevents zerovalent nanoiron aggregation with maintenance of reactivity. The aerosol-based carbon microspheres allow adsorption of TCE, thus removing dissolved TCE rapidly and facilitating reaction by increasing the local concentration of TCE in the vicinity of iron nanoparticles. The strongly adsorptive property of the composites may also prevent release of any toxic chlorinated intermediate products. The composite particles are in the optimal range for transport through groundwater saturated sediments. Furthermore, those iron-carbon composites can be designed at low cost, the process is amenable to scale-up for in situ application, and the materials are intrinsically benign to the environment. 相似文献
179.
Recovery of surface orientation from diffuse polarization. 总被引:1,自引:0,他引:1
When unpolarized light is reflected from a smooth dielectric surface, it becomes partially polarized. This is due to the orientation of dipoles induced in the reflecting medium and applies to both specular and diffuse reflection. This paper is concerned with exploiting polarization by surface reflection, using images of smooth dielectric objects, to recover surface normals and, hence, height. This paper presents the underlying physics of polarization by reflection, starting with the Fresnel equations. These equations are used to interpret images taken with a linear polarizer and digital camera, revealing the shape of the objects. Experimental results are presented that illustrate that the technique is accurate near object limbs, as the theory predicts, with less precise, but still useful, results elsewhere. A detailed analysis of the accuracy of the technique for a variety of materials is presented. A method for estimating refractive indices using a laser and linear polarizer is also given. 相似文献
180.
Wael E. Houssen Dr. Stephen H. Wright Dr. Arnout P. Kalverda Dr. Gary S. Thompson Dr. Sharon M. Kelly Dr. Marcel Jaspars Prof. 《Chembiochem : a European journal of chemical biology》2010,11(13):1867-1873
The solution structure of the leader sequence of the patellamide precursor peptide was analysed by using CD and determined with NOE‐restrained molecular dynamics calculations. This leader sequence is highly conserved in the precursor peptides of some other cyanobactins harbouring heterocycles, and is assumed to play a role in targeting the precursor peptide to the post‐translational machinery. The sequence was observed to form an α‐helix spanning residues 13–28 with a hydrophobic surface on one side of the helix. This hydrophobic surface is proposed to be the site of the initial binding with modifying enzymes. 相似文献