Theoretical exploration of the cooperative effect in NMF-NMF-amino acid residue hydrogen bonding system

This paper presents a theoretical study of the cooperative effect in sixteen linearly-arranged trimer systems consisting of N-methylformamide dimer and an extra amino acid residue. These trimer systems, NMF-NMF-AAR, in short, have been systematically investigated by full optimization at B3LYP/cc-pVTZ level and subsequent electronic energy calculations at PBE1PBE/cc-pVTZ, HF/cc-pVTZ and MP2/cc-pVTZ, respectively. Obvious spatial transformation due to energetic factors has been found in almost all the trimers. Systematic analysis in weak interaction energy components has shown that: (1) in these trimer systems, the bonding structure and the cooperative effect combine to determine the stability of both HB1 and HB2. For HB2, the structure of the constituent amino acid residue also plays a crucial role by interfering with the neighboring moieties; (2) the large contribution of the cooperative effect to the overall hydrogen bonding energy has claimed the importance of cooperativity in our systems; (3) the non-hydrogen bonding weak interaction components are found to be non-negligible in these trimer systems; (4) moreover, the cooperative effect between these non-hydrogen bonding components is always found to be positive. The good performances of PBE1PBE and PM6 have been established by comparisons between these methods.     

Green and high efficient synthesis of triaza‐benzo[b]fluoren‐6‐one derivatives in water under microwave irradiation

Triaza‐benzo[b]fluoren‐6‐one derivatives were synthesized via the three‐component reaction of aldehyde, cyclohexane‐1,3‐dione compound and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.     

Molecular ferroelectrics for efficient perovskite solar cells

During the past decade,the power conversion efficiencies(PCEs)of organic-inorganic hybrid perovskite solar cells(PSCs)have exceeded 25%[1],which is expected to be one of the candidates for the next generation of thin-film photovoltaic technology.Fundamentally speaking,the performance of PSCs mainly depends on the light absorption capacity,defect passivation and photo-induced exciton separation and extraction of perovskite films.Under the light illumination,photo-induced excitons were separated and extracted by the built-in electric field of PSCs.     

The Luminescence of The Phosphor Sr_2ZrO_4 with One-dimensional Chains Structure

IntroductionThenumberofzirconateswhichcanbeexcitedbyconventionalUVexcitation(X>240urn)issmall,sothatzirconateemissioniseasilyoverlooked.SomecompoundswhichabsorbcoventionalUVradiation.ig.ZrO,andBaZrO,(240urn)donotluminenceowingtoenergymigration=.Ontheotherhand,althoughseveralzircinatessuchasZrP,O,:.BaZrSi,O,'andSrZrSi=O,'showefficientUVzirconateemission(around300"m),theirexcitationwavelengthsareshorterthanusual(200"m).Moreover.theirluminescenceareatverylowtemperature(4.2K),whichlimits…     

Colloidal woodpile structure: three-dimensional photonic crystal with a dual periodicity

With planar photolithography and self-assembly techniques, multilayer colloidal crystals with a woodpile structure were fabricated. They represent a new kind of photonic crystals, that is, three-dimensional (3D) photonic crystals with a dual periodicity; one comes from the face-centered cubic (fcc) structure within the colloidal crystal strips and the other one results from the periodic arrangement of the colloidal crystal strips.     

Ammine magnesium borohydride complex as a new material for hydrogen storage: structure and properties of Mg(BH4)2.2NH3

The ammonia complex of magnesium borohydride Mg(BH4)2.2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2.6NH3 (II), which crystallizes in the cubic space group Fm3 m with unit cell parameter a=10.82(1) A and is isostructural to Mg(NH3) 6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a=17.4872(4) A, b=9.4132(2) A, c=8.7304(2) A, and Z=8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2.2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by N-H...H-B dihydrogen bonds. Complex I decomposes endothermically starting at 150 degrees C, with a maximum hydrogen release rate at 205 degrees C, which makes it competitive with ammonia borane BH 3NH3 as a hydrogen storage material.     

Results of L-[1-13C]phenylalanine breath test with air isotope ratio mass spectrometry can reflect the activity of phenylalanine hydroxylase in cirrhotic rat liver

The L-[1-13C]phenylalanine breath test (PheBT) could potentially advance the evaluation of hepatocyte function and liver functional reserve. However, because the factors influencing PheBT results have not been clarified, the clinical application of the test has been limited. This study investigated the relationship between the parameters of PheBT, performed with air isotope ratio mass spectrometry, and the activity of phenylalanine hydroxylase (PAH), the phenylalanine metabolism rate-limiting enzyme, in rat liver, and proposes valid parameters for the assessment of liver function. Chronic injury to the liver was induced by the administration of CCl4 to male Sprague-Dawley rats for either 8 or 12 weeks. Livers from rats in the two cirrhotic groups were discolored, enlarged and roughly textured, with cells filled with fat granules of various sizes, pseudolobuli formations, and regenerated tubercles. Of the 12 parameters tested, only the unit liver weight (LW) breath test parameters, including the maximum abundance of 13C in breath (13Cmax/LW), 13C abundance in breaths 2 and 7 min after administration of L-[1-(13)C]phenylalanine (13C-phe) (13C2/LW and 13C7/LW), cumulative 13C excretion 10 and 30 min after 13C-phe administration (AUC10/LW and AUC30/LW), and the 13C excretion rate constant (PheBT-k/LW) were significantly affected in the chronic liver injury groups. There was no significant difference in the total PAH activity in liver among the three groups, but there was significant difference in unit LW PAH activity. Total PAH activity in the liver was significantly correlated with 13Cmax, 13C2, 13C7, AUC10, AUC30 and PheBT-k, while the unit LW PAH activity was significantly correlated with 13Cmax/LW, 13C2/LW, 13C7/LW, AUC10/LW, AUC30/LW and PheBT-k/LW. PheBT-k/LW was also correlated with biochemical indices that are used to assess liver function. The present findings indicate that the PheBT results based on air isotope ratio mass spectrometry can quantitatively reflect the change in total PAH activity in the livers of chronically injured rats. PheBT-k and PheBT-k/LW are the most sensitive among the test parameters, and can be used to assess liver functional reserve and hepatocyte damage at the molecular level.     

Solid-state near-edge X-ray absorption fine structure spectra of glycine in various charge states

The experimental solid-state near-edge X-ray absorption fine structure spectra for a series of glycine-related samples including alpha-glycine, beta-glycine, glycinium chloride, glycinium trifluoroacetate, and sodium glycinate at the C, N, and O K-edges measured under identical conditions are reported and compared. An assignment of spectral features for alpha-glycine is proposed on the basis of extended theoretical simulations of polarization-dependent spectra performed within the real-space multiple-scattering formalism explicitly taking into account the intermolecular environment of a glycine molecule in a crystal.     

Double-strand DNA cleavage by copper complexes of 2,2'-dipyridyl with electropositive pendants

Two highly charged cationic copper(II) complexes have been synthesized and characterized structurally and spectroscopically: [Cu(L1)2(Br)](ClO4)5 (1) and [Cu(L2)2(Br)](ClO4)5 (2) (L1= 5,5'-di(1-(triethylammonio)methyl)-2,2'-dipyridyl cation and L2= 5,5'-di(1-(tributylammonio)methyl)-2,2'-dipyridyl cation bidentate ligands). X-Ray structures show that Cu(II) ions in both complexes have a trigonal-bipyramidal CuN4Br-configuration. Two nitrogen atoms of the electropositive pendants and coordinated bromine atom basically array in a straight line. Their close distances of N[dot dot dot]Br atoms are 5.772 and 5.594 A, respectively, which is comparable to that of adjacent phosphodiesters in B-form DNA (ca. 6 A). In the absence of reducing agent, supercoiled plasmid DNA cleavage by the complexes has been performed and their hydrolytic mechanisms have been investigated. The pseudo-Michaelis-Menten kinetic parameters (kcat), 4.15 h(-1) for 1, 0.43 h(-1) for 2 and 0.61 h(-1) for [Cu(bipy)(NO3)2], were obtained. This result indicates that 1 exhibits markedly higher nuclease activity than its corresponding analogues. The high ability of DNA cleavage for 1 is attributed to the effective cooperation of the metal moiety and two positive pendants since the array of linear tri-binding sites matches with one of three phosphodiester backbones of nucleic acid.     

On the origin of the unique properties of supported Au nanoparticles

The unique catalytic activity of supported Au nanoparticles has been ascribed to various effects including thickness/shape, the metal oxidation state, and support effects. Previously, we reported the synthesis of ordered Au monolayers and bilayers on TiO(x), with the latter being significantly more active for CO oxidation than the former. In the present study, the electronic and chemical properties of ordered monolayer and bilayer Au films have been characterized by infrared reflection adsorption spectroscopy using CO as a probe and ultraviolet photoemission spectroscopy. The Au overlayers are found to be electron-rich and to have significantly different electronic properties compared with bulk Au. The common structural features of ordered Au bilayers and Au bilayer nanoparticles on TiO2(110) are described, and the exceptionally high catalytic activity of the Au bilayer structure related to its unique electronic properties.