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91.
Ramón R Martín-Gago P Verdaguer X Macias MJ Martin-Malpartida P Fernández-Carneado J Gomez-Caminals M Ponsati B López-Ruiz P Cortés MA Colás B Riera A 《Chembiochem : a European journal of chemical biology》2011,12(4):625-632
We prepared the two enantiomers of 3‐(3′‐quinolyl)‐alanine (Qla, 1 ) in multigram scale by asymmetric hydrogenation. These amino acids, protected as Fmoc derivatives, were then used in the solid‐phase synthesis of two new somatostatin 14 (SRIF‐14) analogues 8 a and 8 b , tetradecapeptides in which the tryptophan residue (Trp8) is replaced by one of the two enantiomers of 3‐(3′‐quinolyl)‐alanine (Qla8) and therefore lack the N? H bond in residue 8. The selectivity of these new analogues for the somatostatin receptors, SSTR1–5, was measured. Substitution with L ‐Qla8 yielded peptide 8 a , which was highly selective for SSTR1 and SSTR3, with an affinity similar to that of SRIF‐14. Substitution by D ‐Qla gave the relatively selective analogue 8 b , which showed high affinity for SSTR3 and significant affinity for SSTR1, SSTR2 and SSTR5. The biological results demonstrate that bulky and electronically poor aromatic amino acids at position 8 are compatible with strong activity with SSTR1 and SSTR3. Remarkably, these high affinity levels were achieved with peptides in which the conformational mobility was increased with respect to that of SRIF‐14. This observation suggests that conformational rigidity is not required, and might be detrimental to the interaction with receptors SSTR1 and SSTR3. The absence of an indole N proton in Qla8 might also contribute to the increased flexibility observed in these analogues. 相似文献
92.
Dr. Geqing Wang Dr. Biswaranjan Mohanty Dr. Martin L. Williams Dr. Bradley C. Doak Dr. Rabeb Dhouib A/Prof. Makrina Totsika Dr. Róisín M. McMahon Dr. Gaurav Sharma Dr. Dan Zheng Dr. Matthew R. Bentley Dr. Yanni Ka-Yan Chin Dr. James Horne Dr. David K. Chalmers A/Prof. Begoña Heras Prof. Martin J. Scanlon 《ChemMedChem》2022,17(6):e202100673
DsbA enzymes catalyze oxidative folding of proteins that are secreted into the periplasm of Gram-negative bacteria, and they are indispensable for the virulence of human pathogens such as Vibrio cholerae and Escherichia coli. Therefore, targeting DsbA represents an attractive approach to control bacterial virulence. X-ray crystal structures reveal that DsbA enzymes share a similar fold, however, the hydrophobic groove adjacent to the active site, which is implicated in substrate binding, is shorter and flatter in the structure of V. cholerae DsbA (VcDsbA) compared to E. coli DsbA (EcDsbA). The flat and largely featureless nature of this hydrophobic groove is challenging for the development of small molecule inhibitors. Using fragment-based screening approaches, we have identified a novel small molecule, based on the benzimidazole scaffold, that binds to the hydrophobic groove of oxidized VcDsbA with a KD of 446±10 μM. The same benzimidazole compound has ∼8-fold selectivity for VcDsbA over EcDsbA and binds to oxidized EcDsbA, with KD>3.5 mM. We generated a model of the benzimidazole complex with VcDsbA using NMR data but were unable to determine the structure of the benzimidazole bound EcDsbA using either NMR or X-ray crystallography. Therefore, a structural basis for the observed selectivity is unclear. To better understand ligand binding to these two enzymes we crystallized each of them in complex with a known ligand, the bile salt sodium taurocholate. The crystal structures show that taurocholate adopts different binding poses in complex with VcDsbA and EcDsbA, and reveal the protein-ligand interactions that stabilize the different modes of binding. This work highlights the capacity of fragment-based drug discovery to identify inhibitors of challenging protein targets. In addition, it provides a starting point for development of more potent and specific VcDsbA inhibitors that act through a novel anti-virulence mechanism. 相似文献
93.
Pavel E. Ramirez Lopez Kenneth C. Mills Peter D. Lee Bego?a Santillana 《Metallurgical and Materials Transactions B》2012,43(1):109-122
Oscillation marks (OMs) are regular, transverse indentations formed on the surface of continuously cast (CC) steel products. OMs are widely considered defects because these are associated with segregation and transverse cracking. A variety of mechanisms for their formation has been proposed (e.g., overflow, folding, and meniscus freezing), whereas different mark types have also been described (e.g., folded, hooks, and depressions). The current work uses numerical modeling to formulate a unified theory for the onset of OMs. The initial formation mechanism is demonstrated to be caused by fluctuations in the metal and slag flow near the meniscus, which in turn causes thermal fluctuations and successive thickening and thinning of the shell, matching the thermal fluctuations observed experimentally in a mold simulator. This multiphysics modeling of the transient shell growth and explicit prediction of OMs morphology was possible for the first time through a model for heat transfer, fluid flow, and solidification coupled with mold oscillation, including the slag phase. Strategies for reducing OMs in the industrial practice fit with the proposed mechanism. Furthermore, the model provides quantitative results regarding the influence of slag infiltration on shell solidification and OM morphology. Control of the precise moment when infiltration occurs during the cycle could lead to enhanced mold powder consumption and decreased OM depth, thereby reducing the probability for transverse cracking and related casting problems. 相似文献
94.
This paper focuses on the differences in the levels of accessibility to public employment offices in the Spanish municipalities. Hence the main purpose is to evaluate the role of the public employment services in local labour markets by considering the physical distance to employment offices and the spatial structure of their catchment areas. First, we propose an accessibility measure and, second, we estimate a spatial model and test whether a higher accessibility to employment offices could contribute to reduce local unemployment rates. The results suggest that policy‐makers should strive to improve the accessibility to employment offices so that adequate assistance to find suitable employment may be ensured to every jobseeker. Resumen Este artículo se centra en las diferencias en los niveles de accesibilidad a las oficinas públicas de empleo en los municipios españoles. El objetivo principal es por tanto evaluar el papel de los servicios públicos de empleo en los mercados laborales locales, en función de la distancia física a las oficinas de empleo y la estructura espacial de sus zonas de influencia. Primero, se propone una medida de accesibilidad y, a continuación, se estima un modelo espacial y se comprueba si una mayor accesibilidad a las oficinas de empleo podría contribuir a reducir las tasas de desempleo local. Los resultados sugieren que los responsables de formular políticas deberían esforzarse por mejorar la accesibilidad a las oficinas de empleo, a fin de poder asegurar a cada demandante de empleo la ayuda apropiada para que logre encontrar un empleo adecuado. 相似文献
95.
Miguel A. Esteruelas Fernando González Juana Herrero Patricia Lucio Montserrat Oliván Begoña Ruiz-Labrador 《Polymer Bulletin》2007,58(5-6):923-931
Summary The thermal properties of trans-polynorbornene, cis-polynorbornene and hydrogenated polynorbornene were examined and its reversibility tested. Trans-polynorbornene samples, formed in various solvents, exhibit a softening range, from ambient temperature until 375 °C. However,
syndiotactic cis-polynorbornene samples show a narrower melting range (between 150 and 375 °C). The fusion enthalpies of cis-polynorbornene samples are around 300-400 J/g. The temperature of decomposition is ca. 456 °C (minimum peak DSC) for trans-polynorbornene and ca. 466 °C, 10 °C higher, for cis-polynorbornene. The solvent used for the polymerization of norbornene has a negligible influence in the melting temperature
range or in the decomposition temperature. The treatment with 2,6-di-tert-butyl-4-methyl-phenol during the isolation of polynorbornene leads to materials with different thermal properties. Trans-polynorbornene isolated without 2,6-di-tert-butyl-4-methyl-phenol exhibited an exothermic peak accompanied by an slight increase in weight (1-2%), while samples treated
with 2,6-di-tert-butyl-4-methyl-phenol do not show these features. 相似文献
96.
Asunción Aranda Begoña Puértolas Benjamín Solsona Said Agouram Ramón Murillo Ana María Mastral Stuart H. Taylor Tomas Garcia 《Catalysis Letters》2010,134(1-2):110-117
Ceria catalysts have been prepared by a nanocasting procedure using SBA-15, MCM-48 and KIT-6 silica-based templates, and investigated for the total oxidation of naphthalene. In all cases cubic fluorite CeO2 was prepared, and the structure of the template was replicated when SBA-15 and MCM-48 were used. The KIT-6 template was not replicated by the nanocasting synthesis, but in all cases mesoporous CeO2 was obtained with high surface areas (91–190 m2 g?1). All of the catalysts demonstrated high activity for naphthalene oxidation to CO2, and the most active was the catalyst prepared from the KIT-6 template. The high activity was attributed to the small crystallite size of the CeO2, combined with high surface area and the highly accessible catalyst surface. 相似文献
97.
Sonia Zaragoza Ana Álvarez Begoña Álvarez Jorge López‐Beceiro Salvador Naya Patricia Forcén Ramón Artiaga 《应用聚合物科学杂志》2015,132(31)
Thermal stability in nonoxidizing atmosphere of a polyetherimide (PEI) is investigated by thermogravimetry (TG). It is observed that thermal degradation of this product consists of two overlapping processes, which are conveniently separated by fitting the TG curves to mixtures of generalized logistic functions. Thus, each process is represented by a single function. The analysis of the fitting parameter values obtained for the main degradation process in different isothermal and heating ramp conditions allows to obtain insightful kinetic parameters (critical temperature, energy barrier, and reaction‐order) which allow to make predictions in both isothermal and nonisothermal contexts. There is a minimum temperature for each process to occur and a ramp‐energy barrier related to the process rate. In the ramp context, the values of these two parameters explain that, although one process starts at lower temperature, it proceeds at a very low rate until reaching temperatures at which the other process goes much faster. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42329. 相似文献
98.
The possibilities for adapting the existing electrostatic device known as the voltage balance ETF-84, to work with a voltage of 100 kV and a weight of 1 kg, are considered. A few theoretical analyses, experiments, and computer simulations have been carried out to define the measurement procedure needed at the required level of uncertainty of 1 part in 108. These analyses identified which parts of the balance itself and of the high voltage electrode isolation have to be reconstructed, as well as how the associated high voltage resistor has to be designed for this purpose 相似文献
99.
Changes in phenolic compounds in lentils (Lens culinaris) during germination and fermentation 总被引:1,自引:0,他引:1
Begoña Bartolomé Isabel Estrella T. Hernández 《European Food Research and Technology》1997,205(4):290-294
Germination and fermentation have been proposed to improve the nutritive value of legumes. This paper reports the changes
that occur in phenolic compounds in lentils (Lens culinaris var. vulgaris) during germination and fermentation. Levels of low-molecular-weight phenolic compounds (benzoic acids and
aldehydes, hydroxycinnamic acids and derivatives, flavan-3-ols and procyanidins) were determined. Germination did not appreciably
vary the content of phenolic compounds, although important structural changes in procyanidin-type compounds were observed.
Fermentation led to a general increase in the content of phenolic compounds. Gentisic acid, p-hydroxyphenylpropionic acid, tryptophol and three other unknown compounds were detected in fermented lentils, but not in
raw lentils. The influence of these changes on the potential antinutritional effects associated with phenolic compounds in
legumes, as well as on the antioxidant properties attributed to these compounds is discussed.
Received: 16 December 1996 / Revised version: 6 March 1997 相似文献
100.
S Razavi B Bego J Kabbani V Bodiguel E Bodard-Rickelman 《Canadian Metallurgical Quarterly》1997,20(9):689-692
To evaluate the effect of education in children with chronic defaecation problems, a prospective 6-week intervention study was designed. A total of 54 children (5-14 years) underwent an education programme, with demystification of symptoms and advice about diet and toilet training. The present treatment was continued. After 6 weeks, children with persistent problems received biofeedback training with a follow up of 1 year. The intervention programme was successful in 8 children (15%). Biofeedback training was successful in 49% of the remaining group after 1 year. CONCLUSION: A total of 15% of the children with chronic defaecation problems seen at a referral centre could surprisingly be helped by a simple education programme with, demystification and toilet training. Further studies evaluating treatment in children with defaecation problems should account for the primary effect of these measures. 相似文献