A benchmark-learning roadmap for regional sustainable development in China

Journal of the Operational Research Society - Serious environmental problems have accompanied China's remarkable economic growth for decades, which also have direct and indirect impacts on its...     

A new decision support model in multi-criteria decision making with intuitionistic fuzzy sets based on risk preferences and criteria reduction

In this paper, we propose a new model for decision support to address the ‘large decision table’ (eg, many criteria) challenge in intuitionistic fuzzy sets (IFSs) multi-criteria decision-making (MCDM) problems. This new model involves risk preferences of decision makers (DMs) based on the prospect theory and criteria reduction. First, we build three relationship models based on different types of DMs’ risk preferences. By building different discernibility matrices according to relationship models, we find useful criteria for IFS MCDM problems. Second, we propose a technique to obtain weights through discernibility matrix. Third, we also propose a new method to rank and select the most desirable choice(s) according to weighted combinatorial advantage values of alternatives. Finally, we use a realistic voting example to demonstrate the practicality and effectiveness of the proposed method and construct a new decision support model for IFS MCDM problems.     

Tuning the regio- and stereoselectivity of C-H activation in n-octanes by cytochrome P450 BM-3 with fluorine substituents: evidence for interactions between a C-F bond and aromatic π systems

We employed the water-soluble cytochrome P450 BM-3 to study the activity and regiospecificity of oxidation of fluorinated n-octanes. Three mutations, A74G, F87V, and L188Q, were introduced into P450 BM-3 to allow the system to undergo n-octane oxidation. In addition, the alanine at residue 328 was replaced with a phenylalanine to introduce an aromatic residue into the hydrophobic pocket to examine whether or not van der Waals interactions between a C-F substituent in the substrate and the polarizable π system of the phenylalanine may be used to steer the positioning of the substrate within the active-site pocket of the enzyme and control the regioselectivity and stereoselectivity of hydroxylation. Interestingly, not only was the regioselectivity controlled when the fluorine substituent was judiciously positioned in the substrate, but the electron input into the iron-heme group became tightly coupled to the formation of product, essentially without abortive side reactions. Remarkable enhancement of the coupling efficiency between electron input and product formation was observed for a range of fluorinated octanes in the enzyme even without the A328F mutation, presumably because of interactions of the C-F substituent with the π system of the porphyrin macrocycle within the active-site pocket. Evidently, tightening the protein domain containing the heme pocket tunes the distribution of accessible enzyme conformations and the associated protein dynamics that activate the iron porphyrin for substrate hydroxylation to allow the reactions mediated by the high-valent Fe(IV)=O to become kinetically more commensurate with electron transfer from the flavin adenine dinucleotide (FAD)/flavin mononucleotide (FMN) reductase. These observations lend compelling evidence to support significant van der Waals interactions between the CF(2) group and aromatic π systems within the heme pocket when the fluorinated octane substrate is bound.     

A robust technique for two-dimensional separation of undistorted chemical-shift anisotropy powder patterns in magic-angle-spinning NMR

A robust magic-angle-spinning experiment for separating undistorted, quasi-static chemical-shift powder patterns is presented. It is derived from the technique of R. Tycko, G. Dabbagh, and P. Mirau (1989, J. Magn. Reson. 85, 265), but uses 360 degrees instead of 180 degrees pulses. In combination with a suitable phase sequence, this makes the spectral patterns very insensitive to pulse-length errors and other imperfections, as demonstrated both experimentally and theoretically. This method, termed separation of undistorted powder patterns by effortless recoupling (SUPER), can be used at standard spinning speeds, between 2.5 and 5 kHz, and with standard radiofrequency power levels (in particular, for protons, a decoupling field strength gammaB(1)/2pi of less than 80 kHz). No significant artifacts are observed even for samples extending to the ends of the radiofrequency coil. The method has been applied to samples containing various sp(2)- and sp(3)-hybridized carbon sites. Even for the methylene groups in polyethylene, a system with very strong C-H and H-H dipolar couplings and only moderate chemical-shift anisotropy (CSA), a useful CSA powder pattern has been obtained. With a CSA scaling factor of 0.155, accuracies of +/-5, +/-3, and +/-1 ppm of the principal values can be achieved for protonated aromatic carbons, unprotonated sp(2)-hybridized groups, and aliphatic sites, respectively. Examples of CSA-based assignment of COOC vs other COO or CON groups, and of aromatic vs olefinic C=C carbons are shown, for both small molecules and polymers.     

Dioxygen activation of a trinuclear Cu(I)Cu(I)Cu(I) cluster capable of mediating facile oxidation of organic substrates: competition between O-atom transfer and abortive intercomplex reduction

The dioxygen activation of a series of Cu(I)Cu(I)Cu(I) complexes based on the ligands (L) 3,3'-(1,4-diazepane- 1,4-diyl)bis(1-{[2-(dimethylamino)ethyl](methyl)amino}propan-2-ol)(7-Me) or 3,3'-(1,4-diazepane-1,4-diyl)bis(1-{[2-(diethylamino)ethyl](ethyl)amino}propan-2-ol)(7-Et) forms an intermediate capable of mediating facile O-atom transfer to simple organic substrates at room temperature. To elucidate the dioxygen chemistry, we have examined the reactions of 7-Me, 7-Et, and 3,3'-(1,4-diazepane-1,4-diyl)bis[1-(4-methylpiperazin-1-yl)propan-2-ol] (7-N-Meppz) with dioxygen at -80, -55, and -35?°C in propionitrile (EtCN) by UV-visible, 77?K EPR, and X-ray absorption spectroscopy, and 7-N-Meppz and 7-Me with dioxygen at room temperature in acetonitrile (MeCN) by diode array spectrophotometry. At both -80 and -55?°C, the mixing of the starting [Cu(I)Cu(I)Cu(I)(L)](1+) complex (1) with O(2)-saturated propionitrile (EtCN) led to a bright green solution consisting of two paramagnetic species: the green dioxygen adduct [Cu(II)Cu(II)(μ-η(2):η(2)-peroxo)Cu(II)(L)](2+) (2) and the blue [Cu(II)Cu(II)(μ-O)Cu(II)(L)](2+) species (3). These observations are consistent with the initial formation of [Cu(II)Cu(II)(μ-O)(2)Cu(III)(L)](1+)(4), followed by rapid abortion of this highly reactive species by intercluster electron transfer from a second molecule of complex 1 to give the blue species 3 and subsequent oxygenation of the partially oxidized [Cu(II)Cu(I)Cu(I)(L)](2+)(5) to form the green dioxygen adduct 2. Assignment of 2 to [Cu(II)Cu(II)(μ-η(2):η(2)-peroxo)Cu(II)(L)](2+) is consistent with its reactivity with water to give H(2)O(2) and the blue species 3, as well as its propensity to be photoreduced in the X-ray beam during X-ray absorption experiments at room temperature. In light of these observations, the development of an oxidation catalyst based on the tricopper system requires consideration of the following design criteria: 1)?rapid dioxygen chemistry; 2)?facile O-atom transfer from the activated cluster to substrate; and 3)?a suitable reductant to rapidly regenerate complex 1 to accomplish efficient catalytic turnover.     

Adsorption of a statherin peptide fragment on the surface of nanocrystallites of hydroxyapatite

Statherin is an active inhibitor of calcium phosphate precipitation in the oral cavity. For many studies of the interaction between statherin and hydroxyapatite (HAp), the samples are prepared by a direct mixing of statherin or its fragment with well-crystalline HAp crystals. In this work, the HAp sample is precipitated in the presence of peptide fragment derived from the N-terminal 15 amino acids of statherin (SN-15). The in situ prepared HAp crystallites are nanosized, leading to a significant increase of the peptide amount adsorbed on the HAp surface. The enhancement in NMR sensitivity allows, for the first time, the measurement of a two-dimensional 13C-13C correlation spectrum for a 13C uniformly labeled peptide sample adsorbed on mineral surface. The measurement time is about 18.5 h at a field strength of 7.05 T. Preliminary results suggest that there may exist two different mechanisms for the interaction between SN-15 and HAp. In addition to the one which will cause a conformational change near the N-terminal, SN-15 may also be absorbed on the HAp surface by simple electrostatic interaction, without any significant conformational changes of the peptides.