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101.
Papeo G Giordano P Brasca MG Buzzo F Caronni D Ciprandi F Mongelli N Veronesi M Vulpetti A Dalvit C 《Journal of the American Chemical Society》2007,129(17):5665-5672
Two novel series of polyfluorinated amino acids (PFAs) were designed and synthesized according to a very short and scalable synthetic sequence. The advantages and limitations of these moieties for screening purposes are presented and discussed. The potential applications of these PFAs were tested with their incorporation into small arginine-containing peptides that represent suitable substrates for the enzyme trypsin. The enzymatic reactions were monitored by 19F NMR spectroscopy, using the 3-FABS (three fluorine atoms for biochemical screening) technique. The high sensitivity achieved with these PFAs permits a reduction in substrate concentration required for 3-FABS. This is relevant in the utilization of 3-FABS in fragment-based screening for identification of small scaffolds that bind weakly to the receptor of interest. The large dispersion of 19F isotropic chemical shifts allows the simultaneous measurement of the efficiency of the different substrates, thus identifying the best substrate for screening purposes. Furthermore, the knowledge of KM and Kcat for the different substrates allows the identification of the structural motifs responsible for the binding affinity to the receptor and those affecting the chemical steps in enzymatic catalysis. This enables the construction of suitable pharmacophores that can be used for designing nonpeptidic inhibitors with high affinity for the enzyme or molecules that mimic the transition state. The novel PFAs can also find useful application in the FAXS (fluorine chemical shift anisotropy and exchange for screening) experiment, a 19F-based competition binding assay for the detection of molecules that inhibit the interaction between two proteins. 相似文献
102.
Our research addresses the role of examples to foster the students’ development of the mathematical concepts, and of their mathematical ways of thinking. We consider the notion of example space introduced by Watson and Mason (Mathematics as a constructive activity: learners generating examples, 2005), particularly when it is not formed by a simple juxtaposition of examples, rather it is endowed by a certain structure. Such a structure is provided by the semiotic actions and by the theoretic and logical dimensions of the mathematical activities. However, the formation of structured example spaces is far from being an automatic process. In this paper, we focus on the genesis of examples and on the role of the teacher in helping the students to structure their examples spaces through the so-called cognitive apprenticeship method. We point out that the genesis of examples is often accomplished within a complex cyclic dynamics, the “cycle of examples production and modification”. We illustrate it by means of two emblematic episodes from a classroom discussion. We show that the teacher’s intervention can be crucial in helping the students to modify a wrong example, to generate the right one for the task and to start the long-term process of building up the structure of their own space of examples. 相似文献
103.
Stephen J. I. Shearan Jannick Jacobsen Prof. Ferdinando Costantino Dr. Roberto D'Amato Dr. Dmitri Novikov Prof. Norbert Stock Prof. Enrico Andreoli Dr. Marco Taddei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6579-6592
We report on the results of an in situ synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated CeIV-based metal–organic frameworks (MOFs), analogues of the already well investigated ZrIV-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as reagents, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds, varying parameters such as temperature, amount of the protonation modulator nitric acid and amount of the coordination modulator acetic acid. When only HNO3 is present in the reaction environment, only F4_MIL-140A(Ce) is obtained. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C. Upon addition of AcOH to the system, alongside HNO3, mixed-phased products are obtained. F4_UiO-66(Ce) is always formed faster, and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate-determining step. A higher amount of HNO3 favours the formation of F4_MIL-140A(Ce), whereas increasing the amount of AcOH favours the formation of F4_UiO-66(Ce). Based on the in situ results, a new optimised route to achieving a pure, high-quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified. 相似文献
104.
105.
Subhalakshmi Nagarajan Ramaswamy Nagarajan Rahul Tyagi Jayant Kumar Ferdinando F. Bruno Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):951-956
Hematin, a hydroxyferriprotoporphyrin, is the stable, oxidized form of heme. Heme has been reported to be the active catalytic center of naturally occurring peroxidases such as horseradish peroxidase (HRP). While there have been reports on the use of hematin as a catalyst for oxidative polymerization reactions, these reactions could be carried out only at high pH conditions due to limited aqueous solubility of hematin at lower pH conditions. We report here the biocatalytic modification of hematin using a lipase, Novozyme-435. Hematin has been modified by tethering monomethoxy polyethylene glycol (mPEG) chains which provide aqueous solubility over a fairly wide range of pH conditions. This pegylated Hematin (PEG-Hematin) is synthesized via a one-step solventless reaction and the products formed can be isolated with minimal purification. The PEG-Hematin synthesized serves as a robust alternative to HRP for the polymerization of aniline and phenol. 相似文献
106.
107.
The article contributes to the ongoing discussion on ways to deal with the diversity of theories in mathematics education research. It introduces and systematizes a collection of case studies using different strategies and methods for networking theoretical approaches which all frame (qualitative) empirical research. The term ‘networking strategies’ is used to conceptualize those connecting strategies, which aim at reducing the number of unconnected theoretical approaches while respecting their specificity. The article starts with some clarifications on the character and role of theories in general, before proposing first steps towards a conceptual framework for networking strategies. Their application by different methods as well as their contribution to the development of theories in mathematics education are discussed with respect to the case studies in the ZDM-issue. 相似文献
108.
Bernardo Nicoletti Luigi Mariani Ferdinando Pezzella 《European Journal of Operational Research》1979,3(1):23-29
In a highly simplified version of a common economic model, the planner can choose among alternative time-varying designs for the information structure in order to steer the system to a target state in an optimal way. The resulting problem is imbedded into a more general one with bilinear dynamics, that is, linear in the control and the state variables but not in both. The existence of a feasible decentralized information structure is studies and designs are found which make the system optimal, given a performance function assigning losses to deviations froma target state. The conditions under which a decentralized structure is optimal are also studied and a numerical case is considered. 相似文献
109.
In this paper a dynamic regional model is proposed, aimed at understanding and forecasting the dynamic response of the population to many different investment policies in the agricultural, services and industrial sectors. In spite of its generality, the model has been conceived in order to be applied to underdeveloped regions. Particularly, from the demographic point of view, attention has been focused on migration phenomena; from the economic point of view, attention has been focused mainly on the rate of growth of the capital stock.
Modularity is another feature of the proposed model; it is made of seven submodels which describe in a very aggregated form the evolution of the regional socio-economic system. The outputs of the submodels are then spatially distributed using a set of ‘spatial operators’ which take into account many social and economic factors relevant to the sub-areas into which the region can be divided. 相似文献
110.
Designs, Codes and Cryptography - Wachter-Zeh (IEEE Trans Inf Theory 59(11):7268–7276, 2013), and later together with Raviv (IEEE Trans Inf Theory 62(4):1605–1615, 2016), proved that... 相似文献