Quartic anharmonic resonances in acetylene molecules

Formulas are derived for the quartic anharmonic resonance coefficients observed to be important between C–H stretching and the combination of one quantum of C≡C stretching and two quanta of H–C≡C bending in a number of acetylene molecules. Examples of this resonance are ν3 with ν2+ν4+ν5 in 12C2H2, ν1 with ν2+2ν5 in 13C2H2, and ν1 with ν2+2ν4 in monofluoroacetylene and monochloroacetylene. The coefficients characterizing the resonances in these examples, which we denote K3,245, K1,255, and K1,244, arise from cubic and quartic terms in the anharmonic force field, in the normal coordinate representation, through second order and first order perturbation treatments respectively, where the second order resonances are calculated by a Van Vleck resonance formalism. The experimentally determined values of these coefficients are compared with values calculated from model anharmonic force fields.

Mapping antimalarial pharmacophores as a useful tool for the rapid discovery of drugs effective in vivo: design, construction, characterization, and pharmacology of metaquine

Resistant strains of Plasmodium falciparum and the unavailability of useful antimalarial vaccines reinforce the need to develop new efficacious antimalarials. This study details a pharmacophore model that has been used to identify a potent, soluble, orally bioavailable antimalarial bisquinoline, metaquine (N,N'-bis(7-chloroquinolin-4-yl)benzene-1,3-diamine) (dihydrochloride), which is active against Plasmodium berghei in vivo (oral ID50 of 25 mu mol/kg) and multidrug-resistant Plasmodium falciparum K1 in vitro (0.17 mu M). Metaquine shows strong affinity for the putative antimalarial receptor, heme at pH 7.4 in aqueous DMSO. Both crystallographic analyses and quantum mechanical calculations (HF/6-31+G*) reveal important regions of protonation and bonding thought to persist at parasitic vacuolar pH concordant with our receptor model. Formation of drug-heme adduct in solution was confirmed using high-resolution positive ion electrospray mass spectrometry. Metaquine showed strong binding with the receptor in a 1: 1 ratio (log K = 5.7 +/- 0.1) that was predicted by molecular mechanics calculations. This study illustrates a rational multidisciplinary approach for the development of new 4-aminoquinoline antimalarials, with efficacy superior to chloroquine, based on the use of a pharmacophore model.

Proteomic analysis of the site specificity of glycation and carboxymethylation of ribonuclease

Proteomic analysis using electrospray liquid chromatography-mass spectrometry (ESI-LC-MS) has been used to compare the sites of glycation (Amadori adduct formation) and carboxymethylation of RNase and to assess the role of the Amadori adduct in the formation of the advanced glycation end-product (AGE), N-is an element of-(carboxymethyl)lysine (CIVIL). RNase (13.7 mg/mL, 1 mM) was incubated with glucose (0.4 M) at 37 degreesC for 14 days in phosphate buffer (0.2 M, pH 7.4) under air. On the basis of ESI-LC-MS of tryptic peptides, the major sites of glycation of RNase were, in order, K41, K7, K1, and K37. Three of these, in order, K41, K7, and K37 were also the major sites of CIVIL formation. In other experiments, RNase was incubated under anaerobic conditions (1 mM DTPA, N-2 purged) to form Amadori-modified protein, which was then incubated under aerobic conditions to allow AGE formation. Again, the major sites of glycation were, in order, K41, K7, K1, and K37 and the major sites of carboxymethylation were K41, K7, and K37. RNase was also incubated with 1-5 mM glyoxal, substantially more than is formed by autoxidation of glucose under experimental conditions, but there was only trace modification of lysine residues, primarily at K41. We conclude the following: (1) that the primary route to formation of CIVIL is by autoxidation of Amadori adducts on protein, rather than by glyoxal generated on autoxidation of glucose; and (2) that carboxymethylation, like glycation, is a site-specific modification of protein affected by neighboring amino acids and bound ligands, such as phosphate or phosphorylated compounds. Even when the overall extent of protein modification is low, localization of a high proportion of the modifications at a few reactive sites might have important implications for understanding losses in protein functionality in aging and diabetes and also for the design of AGE inhibitors.

Structures and negative thermal expansion properties of the one-dimensional cyanides, CuCN, AgCN and AuCN

The behaviour of the lattice parameters of HTCuCN (high-temperature form), AgCN and AuCN have been investigated as a function of temperature over the temperature range 90–490 K. All materials show one-dimensional negative thermal expansion (NTE) along the ––(M––CN)–– chain direction c (ac(HT-CuCN) ¼32.1 10–6 K1, ac(AgCN)¼23.910–6 K1 and ac(AuCN) ¼9.3106 K1 over the temperature range 90–490 K). The origin of this behaviour has been studied using RMC modelling of Bragg and total neutron diffraction data from AgCN and AuCN at 10 and 300 K. These analyses yield details of the local motions within the chains responsible for NTE. The low-temperature form of CuCN, LT-CuCN, has been studied using single-crystal X-ray diffraction. In this form of CuCN, wavelike distortions of the ––(Cu––CN)–– chains occur in the static structure, which are reminiscent of the motions seen in the RMC modelling of AgCN and AuCN, which are responsible for the NTE behaviour.

Homoleptic Diphosphacyclobutadiene Complexes [M(η4-P2C2R2)2]x− (M=Fe, Co; x=0, 1)

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown-6)(thf)2][Fe(hapto4-P2C2tBu2)2] (K1), [K([18]crown-6)(thf)2][C(h4-P2C2tBu2)2] (K2), and [K([18]crown-6)(thf)2][Co(hapto4-P2C2Ad2)2] (K3, Ad=adamantyl) were obtained from reactions of [K([18crown-6)(thf)2][M(hapto4-C14H10)2] (M=Fe, Co) with tBuCP (1, 2), or with AdCP (3). Neutral sandwiches [M(hapto4-P2C2tBu2)2] (4: M=Fe 5: M=Co) were obtained by oxidizing 1 and 2 with [Cp2Fe]PF6. Cyclic voltammetry and spectro-electrochemistry indicate that the two [M(hapto4-P2C2tBu2)2]-/[M(hapto4-P2C2tBu2)2] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1–5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis,and Moessbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1–3). The molecular structures of 1–5 were determined by using X-ray crystallography. Essentially D2d-symmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal–ligand pi bonding in 1–5. Possible oxidation state assignments for the metal ions are discussed.

Unraveling the electronic structures of low-valent naphthalene and anthracene iron complexes: x-ray, spectroscopic, and density functional theory studies

Naphthalene and anthracene transition metalates are potent reagents, but their electronic structures have remained poorly explored. A study of four Cp*-substituted iron complexes (Cp* = pentamethylcyclopentadienyl) now gives rare insight into the bonding features of such species. The highly oxygen- and water-sensitive compounds [K(18-crown- 6){Cp*Fe(η4-C10H8)}] (K1), [K(18-crown-6){Cp*Fe(η4-C14H10)}] (K2), [Cp*Fe(η4-C10H8)] (1), and [Cp*Fe(η4-C14H10)] (2) were synthesized and characterized by NMR, UV−vis, and 57Fe Mössbauer spectroscopy. The paramagnetic complexes 1 and 2 were additionally characterized by electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements. The molecular structures of complexes K1, K2, and 2 were determined by single-crystal X-ray crystallography. Cyclic voltammetry of 1 and 2 and spectroelectrochemical experiments revealed the redox properties of these complexes, which are reversibly reduced to the monoanions [Cp*Fe(η4-C10H8)]− (1−) and [Cp*Fe(η4-C14H10)]− (2−) and reversibly oxidized to the cations [Cp*Fe(η6-C10H8)]+ (1+) and [Cp*Fe(η6-C14H10)]+ (2+). Reduced orbital charges and spin densities of the naphthalene complexes 1−/0/+ and the anthracene derivatives 2−/0/+ were obtained by density functional theory (DFT) methods. Analysis of these data suggests that the electronic structures of the anions 1− and 2− are best represented by low-spin FeII ions coordinated by anionic Cp* and dianionic naphthalene and anthracene ligands. The electronic structures of the neutral complexes 1 and 2 may be described by a superposition of two resonance configurations which, on the one hand, involve a low-spin FeI ion coordinated by the neutral naphthalene or anthracene ligand L, and, on the other hand, a low-spin FeII ion coordinated to a ligand radical L•−. Our study thus reveals the redox noninnocent character of the naphthalene and anthracene ligands, which effectively stabilize the iron atoms in a low formal, but significantly higher spectroscopic oxidation state.

Size and molecular flexibility affect the binding of ellagitannins to bovine serum albumin

Binding to bovine serum albumin of monomeric (vescalagin and pedunculagin) and dimeric ellagitannins (roburin A, oenothein B, and gemin A) was investigated by isothermal titration calorimetry and fluorescence spectroscopy, which indicated two types of binding sites. Stronger and more specific sites exhibited affinity constants, K1, of 104–106 M–1 and stoichiometries, n1, of 2–13 and dominated at low tannin concentrations. Weaker and less-specific binding sites had K2 constants of 103–105 M–1 and stoichiometries, n2, of 16–30 and dominated at higher tannin concentrations. Binding to stronger sites appeared to be dependent on tannin flexibility and the presence of free galloyl groups. Positive entropies for all but gemin A indicated that hydrophobic interactions dominated during complexation. This was supported by an exponential relationship between the affinity, K1, and the modeled hydrophobic accessible surface area and by a linear relationship between K1 and the Stern–Volmer quenching constant, KSV.

Nodal variations and long-term changes in the main tides on the coasts of China

The long-term changes in the main tidal constituents (O1, K1, M2, N2, and S2) along the coasts of China and in adjacent seas are investigated based on 17 tide-gauge records covering the period 1954–2012. The observed 18.61 year nodal modulations of the diurnal constituents O1 and K1 are in agreement with the equilibrium tidal theory, except in the South China Sea. The observed modulations of the M2 and N2 amplitudes are smaller than theoretically predicted at the northern stations and larger at the southern stations. The discrepancies between the theoretically predicted nodal variations and the observations are discussed. The 8.85 year perigean cycle is identifiable in the N2 parameters at most stations, except those in the South China Sea. The radiational component of S2 contributes on average 16% of the observed S2 except in the Gulf of Tonkin, on the south coast, where it accounts for up to 65%. We confirmed the existence of nodal modulation in S2, which is stronger on the north coast. The semidiurnal tidal parameters show significant secular trends in the Bohai and Yellow Seas, on the north coast, and in the Taiwan Strait. The largest increase is found for M2 for which the amplitude increases by 4–7 mm/yr in the Yellow Sea. The potential causes for the linear trends in tidal constants are discussed.

Genetic diversity at the Dhn3 locus in Turkish Hordeum spontaneum populations with comparative structural analyses

We analysed Hordeum spontaneum accessions from 21 different locations to understand the genetic diversity of HsDhn3 alleles and effects of single base mutations on the intrinsically disordered structure of the resulting polypeptide (HsDHN3). HsDHN3 was found to be YSK2-type with a low-frequency 6-aa deletion in the beginning of Exon 1. There is relatively high diversity in the intron region of HsDhn3 compared to the two exon regions. We have found subtle differences in K segments led to changes in amino acids chemical properties. Predictions for protein interaction profiles suggest the presence of a protein-binding site in HsDHN3 that coincides with the K1 segment. Comparison of DHN3 to closely related cereals showed that all of them contain a nuclear localization signal sequence flanking to the K1 segment and a novel conserved region located between the S and K1 segments [E(D/T)DGMGGR]. We found that H. vulgare, H. spontaneum, and Triticum urartu DHN3s have a greater number of phosphorylation sites for protein kinase C than other cereal species, which may be related to stress adaptation. Our results show that the nature and extent of mutations in the conserved segments of K1 and K2 are likely to be key factors in protection of cells.

Functional analysis of the sheep Wilson disease protein (sATP7B) in CHO cells

In this study we investigated the function of the sheep orthologue of ATP7B (sATP7B), the protein affected in the human copper toxicosis disorder Wilson disease. Two forms of sATP7B are found in the sheep, a ‘normal’ form and one with an alternate N terminus, both of which were expressed in CHO-K1 cells. Cells expressing either form of sATP7B were more resistant to copper than the parental CHO-K1 cells. Subcellular localisation studies showed that both forms of sATP7B were similarly located in the trans-Golgi network (TGN). When the extracellular copper concentration was increased, each form of sATP7B redistributed to a punctate, vesicular compartment that extended throughout the cytoplasm. Both forms of sATP7B recycled to the perinuclear location within one hour when the cells were subsequently incubated in basal medium. After treatment of cells with bafilomycin A1 sATP7B accumulated in cytoplasmic vesicles, implying that ATP7B continuously recycles via the endocytic pathway. These results suggest that both forms of sATP7B are functional copper-transport proteins and that the intracellular location and trafficking of the sheep protein within the cell also appears normal.

2-Amino-3-aroyl-4,5-alkylthiophenes: Agonist allosteric enhancers at human A1 adenosine receptors

2-Amino-3-benzoylthiophenes are allosteric enhancers (AE) of agonist activity at the A₁ adenosine receptor. The present report describes syntheses and assays of the AE activity at the human A₁AR (hA₁AR) of a panel of compounds consisting of nine 2-amino-3-aroylthiophenes (3a-i), eight 2-amino-3-benzoyl-4,5-dimethylthiophenes (12a-h), three 3-aroyl-2-carboxy-4,5- dimethylthiophenes (15a-c), 10 2-amino-3-benzoyl-5,6-dihydro 4H-cyclopenta[b]thiophenes (17a-j), 14 2-amino-3-benzoyl-4,5,6,7-tetrahydrobenzo[b]thiophenes (18a-n), and 15 2-amino- 3-benzoyl-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophenes (19a-o). An in vitro assay employing the A₁AR agonist [¹²⁵I]ABA and membranes from CHO-K1 cells stably expressing the hA¹AR measured, as an index of AE activity, the ability of a candidate AE to stabilize the agonist- A₁AR-G protein ternary complex. Compounds 3a-i had little or no AE activity, and compounds 12a-h had only modest activity, evidence that AE activity depended absolutely on the presence of at least a methyl group at C-4 and C-5. Compounds 17a-c lacked AE activity, suggesting the 2-amino group is essential. Polymethylene bridges linked thiophene C-4 and C-5 of compounds 17a-j, 18a-n, and 19a-o. AE activity increased with the size of the -(CH₂)_n- bridge, n ) 3 < n ) 4 < n ) 5. The 3-carbethoxy substituents of 17a, 18a, and 19a did not support AE activity, but a 3-aroyl group did. Bulky (or hydrophobic) substituents at the meta and para positions of the 3-benzoyl group and also 3-naphthoyl groups greatly enhanced activity. Thus, the hA₁AR contains an allosteric binding site able to accommodate 3-aroyl substituents that are bulky and/or hydrophobic but not necessarily planar. A second region in the allosteric binding site interacts constructively with alkyl substituents at thiophene C-4 and/or C-5.

10 mM glucosamine prevents activation of proADAMTS5 (aggrecanase-2) in transfected cells by interference with post-translational modification of furin

Objective
Glucosamine has been previously shown to suppress cartilage aggrecan catabolism in explant cultures. We determined the effect of glucosamine on ADAMTS5 (a disintegrin-like and metalloprotease domain (reprolysin type) with thrombospondin type-1 motifs 5), a major aggrecanase in osteoarthritis, and investigated a potential mechanism underlying the observed effects.

Design
HEK293F and CHO-K1 cells transiently transfected with ADAMTS5 cDNA were treated with glucosamine or the related hexosamine mannosamine. Glucosamine effects on FURIN transcription were determined by quantitative RT-PCR. Effects on furin-mediated processing of ADAMTS5 zymogen, and aggrecan processing by glucosamine-treated cells, were determined by western blotting. Post-translational modification of furin and N-glycan deficient furin mutants generated by site-directed mutagenesis was analyzed by western blotting, and the mutants were evaluated for their ADAMTS5 processing ability in furin-deficient CHO-RPE.40 cells.

Results
Ten mM glucosamine and 5–10 mM mannosamine reduced excision of the ADAMTS5 propeptide, indicating interference with the propeptide excision mechanism, although mannosamine compromised cell viability at these doses. Although glucosamine had no effect on furin mRNA levels, western blot of furin from glucosamine-treated cells suggested altered post-translational modification. Glucosamine treatment led to decreased glycosylation of cellular furin, with reduced furin autoactivation as the consequence. Recombinant furin treated with peptide N-glycanase F had reduced activity against a synthetic peptide substrate. Indeed, site-directed mutagenesis of two furin N-glycosylation sites, Asn387 and Asn440, abrogated furin activation and this mutant was unable to rescue ADAMTS5 processing in furin-deficient cells.

Conclusions
Ten mM glucosamine reduces excision of the ADAMTS5 propeptide via interference with post-translational modification of furin and leads to reduced aggrecanase activity of ADAMTS5.

Structure and phase stability of NiMnGa ferromagnetic shape memory alloys by experimental and ab-initio techniques

This paper summarizes some of our recent results on crystal structure, microstructure, orientation relationship between martensitic variants and crystallographic features of martensitic transformation in Ni-Mn-Ga FSMAs. It was shown that Ni53Mn25Ga22 has a tetragonal I4/mmm martensitic structure at room temperature. The neighboring martensitic variants in Ni53Mn25Ga22 have a compound twinning relationship with the twinning elements K1={112}, K2={11-2}, η1=<11-1>, η2=<111>, P={1-10} and s=0.379. The ratio of the relative amounts of twins within the same initial austenite grain is ~1.70. The main orientation relationship between austenite and martensite is Kurdjumov-Sachs (K-S) relationship. Based on the crystallographic phenomenological theory, the calculated habit plane is {0.690 -0.102 0.716}A (5.95° from {101}A), and the magnitude, direction and shear angle of the macroscopic transformation shear are 0.121, <-0.709 0.105 0.698>A (6.04° from <-101>A) and 6.88°, respectively.

Influence of orientation on twin nucleation and growth at low strains in a magnesium alloy

The resolved shear stress is believed to play an important role in twin formation. The present study tests this idea for an extruded magnesium alloy by examining "tension" twinning in different grain orientations. Electron backscatter diffraction analysis is employed for alloy AZ31 tested in compression along the extrusion axis to strains between 0.008 and 0.015. For heavily twinned grains, it is seen that twinning occurs on 2.3 twin systems per grain on average. The active systems are also most commonly those with, or very near to, the highest Schmid factor. The most active system in multiply twinned grains accounts on average for ∼0.6 of the twinning events. In addition, it is found that the twin habit plane falls within 6° of the K1 plane. Orientations with the highest Schmid factors (0.45-0.5) for twinning display twin aspect ratios greater by ∼40% and twin number densities greater by ∼10 times than orientations with maximum Schmid factors for twinning of 0.15-0.2. Thus the Schmid factor for twinning is seen to affect nucleation more than thickening in the present material. Viscoplastic crystal plasticity simulations are employed to obtain approximations for the resolved shear stress. Both the twin aspect ratio and number density correlate quite well with this term. The effect of the former can be assumed to be linear and that of the latter follows a power law with exponent ∼13. Increased aspect ratios and number densities are seen at low Schmid factors and this may relate to stress fluctuations, caused most probably in the present material by the stress fields at the tips of blocked twins. Overall, it is evident that the dominance of twinning on high Schmid factor systems is preserved at the low strains examined in the present work, despite the stress fluctuations known to be present. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Avaliação do estresse oxidativo induzido por superfícies de titânio

Commercially pure Titanium (cp Ti) is a material largely used in orthopedic and dental implants due to its biocompatibility properties. Changes in the surface of cp Ti can determine the functional response of the cells such as facilitating implant fixation and stabilization, and increased roughness of the surface has been shown to improve adhesion and cellular proliferation. Various surface modification methods have been developed to increase roughness, such as mechanical, chemical, electrochemical and plasma treatment. An argon plasma treatment generates a surface that has good mechanical proprieties without chemical composition modification. Besides the topography, biological responses to the implant contribute significantly to its success. Oxidative stress induced by the biomaterials is considered one of the major causes of implant failure. For this reason the oxidative potential of titanium surfaces subjected to plasma treatment was evaluated on this work. CHO-k1 cells were cultivated on smooth or roughed Ti disks, and after three days, the redox balance was investigated measuring reactive oxygen species (ROS) generation, total antioxidant capacity and biomarkers of ROS attack. The results showed cells grown on titanium surfaces are subjected to intracellular oxidative stress due to hydrogen peroxide generation. Titanium discs subjected to the plasma treatment induced less oxidative stress than the untreated ones, which resulted in improved cellular ability. Our data suggest that plasma treated titanium may be a more biocompatible biomaterial.