Insight into shock-induced chemical reaction from the perspective of ring strain and rotation of chemical bonds

Density functional theory BLYP/DNP and hyperhomodesmotic equations were employed to calculate ring strain energy, the bond dissociation energy of X–NO₂ (X=C, N) and the charges on the nitro groups of several four-membered and six-membered heterocycle compounds. BLYP/DNP and LST/QST + CG method were also applied to calculate bond rotational energy of X–NO₂ (X=C, N) of above mentioned compounds. It indicated that ring strain energy of four-membered heterocycle nitro compounds is apparently higher than that of six-membered heterocycle nitro compounds. Predictably, ring-opening reactions may preferentially occur for those compounds containing higher ring strain energy under shock. In addition, C–NO₂ bonds in these compounds may rotate easier than N–NO₂ bonds in response to the external shock. As for N–NO₂ bonds in these compounds, they also respond to the external shock by the rotation of N–NO₂ bonds, once to the saddle point of the rotational energy barrier, the whole molecule will become relaxed, N–NO₂ bond becomes weaker and eventually leads to the breakage. When one ?C=O, ?C=NH or ?NH₂ group is introduced to the six-membered heterocycle, the charges on the nitro groups of the new compound decrease drastically, and ring strains increase remarkably. It can be predicted that the new compounds will be more sensitive to shock, and the viewpoint is confirmed by the experimental results of shock sensitivity (small scale gap test) of several explosives.     

A density functional theory analysis for the adsorption of the amine group on graphene and boron nitride nanosheets

In this paper first principles total energy calculations to study the adsorption of amine group (NH₂) on graphene (G) and boron nitride (hBN) nanosheets are developed; the density functional theory, within the local density approximation and Perdew-Wang functional was employed. The sheets were modeled with a sufficiently proved C_nH_m-like cluster with armchair edge. The optimized geometry was obtained following the minimum energy criterion, searching on four positions for each nanosheet: perpendicular to the carbon atom, on the hexagon, inside the hexagon and on the bridge C–C, for the G-amine interaction; and, perpendicular to the B, perpendicular to the N, on the hexagon, and inside the hexagon, for the hBN-amine interaction. A physisorption, with amine parallel to the C–C–C bond with a distance graphene-amine of 2.56 Å, was found. For the case of BN a B–N bond, with bond length equal to 1.56 Å, was found; the amine lies perpendicular to the nanosheet. When the graphene is doped with B and Al atoms a chemisorption with B–N (1.57 Å) and Al–N (1.78 Å) bonds is observed; the bond angle in the amine group is also incremented, 5.5° and 8.1°, respectively. In the presence of point defects (monovacancies) of B in the hBN-amine and C in the G-amine, there exists chemisorption, increasing the reactivity of the sheets.     

Synthesis,X-ray crystal structure study and antitumoral evaluations of 5,6-disubstituted pyrimidine derivatives

5,6-Disubstituted pyrimidine derivatives (3–20) were prepared by intramolecular cyclization reaction of α-(1-carbamyliminomethylene)-γ-butyrolactone (2) with sodium ethoxide and subsequent chemical transformation of 2-hydroxy group in C-5 side chain as well as lithiation reaction for introduction of acyclic side chain at C-6. All compounds were characterized by ¹H NMR, ¹³C NMR and mass spectra. Structures of compounds 4, 7 and 14 were unambiguously confirmed by X-ray crystal structural analysis. Supramolecular structures of these three compounds differ significantly. Two N–H?O and one C–H?O hydrogen bonds in 4 form three-dimensional network. One O–H?N hydrogen bond and one π?π interaction self-assemble the molecules of 7 into sheets. In supramolecular aggregation of 14, only π?π stacking interactions participate, so forming chains. The compounds were evaluated for their cytostatic activities against human malignant cell lines. Of all tested compounds, 2,4-dimethoxy-5-methoxytritylethylpyrimidine (9) and 2,4-dichloro-5-chloroethylpyrimidine (14) exhibited the most prominent inhibitory effects. Furthermore, compound 14 showed marked activity against human colon carcinoma (IC₅₀ = 0.4 μM).     

A theoretical study on 1,5-diazido-3-nitrazapentane (DANP) and 1,7-diazido-2,4,6-trinitrazaheptane (DATNH): molecular and crystal structures, thermodynamic and detonation properties, and pyrolysis mechanism

1,5-Diazido-3-nitrazapentane (DANP) and 1,7-diazido-2,4,6-trinitrazaheptane (DATNH) are two energetic plasticizers. To better understand them, a detailed theoretical investigation was carried out using density functional theory and molecular mechanics methods. The crystal structures, spectra, thermodynamic properties, heats of formation, detonation velocity, detonation pressure, specific impulse and thermal stability were estimated. Possible initiation steps of pyrolysis were discussed by considering the bond breaking of N–NO₂, C–N₃, and N–N₂ (via hydrogen transfer) for both compounds and the cyclization of the adjacent nitro and azido groups for DATNH. Results show that the rupture of N–NO₂ and N–N₂ (via hydrogen transfer) may happen simultaneously as the initial step of pyrolysis. Both crystals have P-1 symmetry as was observed experimentally. DANP has higher stability than DATNH, while DATNH has better detonation performance than DANP. In addition, DANP has a lower while DATNH has a higher specific impulse than RDX, which shows their prospects as propellant components.     

Land cover change effects on soil chemical and biological properties after planting Mongolian pine (Pinus sylvestris var. mongolica) in sandy lands in Keerqin, northeastern China

We compared soil moisture content, pH, total organic carbon (C _org), total nitrogen (TN), total phosphorus (TP) and inorganic N (NH₄ ⁺–N, NO₃ ^?–N) concentrations, soil potential C and N mineralization rates, soil microbial biomass C (C _mic), soil metabolic quotient (qCO₂), soil microbial quotient (C _mic/C _org) and soil enzyme (urease and invertase) activities in semiarid sandy soils under three types of land cover: grassland, Mongolian pine (Pinus sylvestris var. mongolica) plantation, and elm (Ulmus punila)–grass savanna in southeastern Keerqin, in northeast China. Soil C _org, TN and TP concentrations (0–10, 10–20, 20–40 and 40–60 cm) were lower while soil C/N and C/P ratios were higher in the plantation than in grassland and savanna. The effects of land cover change on NH₄ ⁺–N and NO₃ ^?–N concentrations, soil potential nitrification and C mineralization rates in the surface soil (0–10 cm) were dependent on sampling season; but soil potential N mineralization rates were not affected by land cover type and sampling season. The effects of land cover change on C _mic and qCO₂ of surface soil were not significant; but C _mic/C _org were significantly affected by land cover change and sampling season. We also found that land cover change, sampling season and land cover type?×?sampling season interaction significantly influenced soil enzyme (urease and invertase) activities. Usually soil enzyme activities were lower in the pine plantations than in grassland and savanna. Our results suggest that land cover change markedly influenced soil chemical and biological properties in sandy soils in the semiarid region, and these effects vary with sampling season.     

Characterization of Limonoids Isolated from the Fruits of Melia toosendan and Their Antifeedant Activity against Pieris rapae

The fruits of Melia toosendan Sieb . et Zucc . (Meliaceae) are a source of bioactive limonoids that can be used as effective pesticides. In this study, two novel limonoids, 6‐acetylsendanal and 6‐ketocinamodiol, were isolated together with fourteen known compounds, namely four protolimonoids, six trichilin‐class limonoids, and four C‐seco limonoids. The structures of the new compounds were determined by extensive spectroscopic analyses (HR‐ESI‐MS, UV, IR, 1D and 2D NMR). The bioassay results revealed that eleven of the extracted limonoids exhibited interesting antifeedant activities against the larvae of Pieris rapae with AFC₅₀ values in the range of 0.11–1.79 mm . Particularly, mesendanin H, with an AFC₅₀ value of 0.11 mm , exhibited a higher activity than the positive control toosendanin. Information on new bioactive limonoids may provide further insight into M. toosendan as a source of bioactive components.     

Dynamics of simple carbon compounds in two forest soils as revealed by soil solution concentrations and biodegradation kinetics

Simple compounds in soil such as organic acids, amino acids and monosaccharides are believed to be important in regulating many aspects of terrestrial ecosystem functioning (e.g. C cycling, nutrient acquisition). Understanding the fate and dynamics of these low molecular weight (MW) compounds is therefore essential for predicting ecosystem responses to disturbance. Our aim was to quantify the amounts of these compounds in two podzolic forest soil profiles (O, E, Bs and C horizons) and to quantify their contribution to total soil respiration. The total concentration of organic acids, amino acids and monosaccharides in soil solution comprised on average 15?±?10% of the total dissolved organic C (DOC), with declining concentrations in the deeper soil layers. Dissolved organic N (DON) was the dominant form of N in soil solution and free amino acids contributed to 34% of this pool. The mineralization behaviour of glucose and galactose was described by parabolic (Michaelis–Menten) type kinetics with V _max and K _M values in the range of <1–250 μmol kg^?1 h^?1 and 15–1,100 μM, respectively. Assuming that (1) microbially mediated substrate turnover follows Michaelis–Menten kinetics, and (2) steady state soil solution concentrations, we calculated the rate of CO₂ efflux attributable to the mineralisation of the three classes of low MW compounds. Our results indicated that in the O horizon, the turnover of these substrates could comprise ~100% of the basal, heterotrophic, soil respiration. In contrast, in the deeper mineral soil <20% of total soil respiration could be attributable to the mineralization of these compounds. Our compound-specific approach has identified the main substrates contributing to soil respiration in forest topsoils. However, our results also suggest that soil respiration in subsoils may be attributable to compounds other than organic acids, amino acids and monosaccharides.     

Intramolecular electronic energy transfer in peptides carrying naphthalene and protoporphyrin molecules: A spectroscopic and conformational statistics investigation

Short linear peptides, carrying an AA spacer in the backbone chain (AA = Aib or Ala),and naphthalene(N) and protoporphyrin IX(P) covalently bound to ?-amino groups of lysine side chains, were synthesized. The general formula is Boc-Leu-Leu-Lys(P)-(AA)_n-Leu-Leu-Lys(N)-OtBu, with n = 0–2. The photophysical behavior of these compounds was investigated in water/methanol 75/25(v/v) solution by steady-state and time-resolved fluorescence experiments. Quenching of excited naphthyl chromophore lakes place by electronic energy transfer to the porphyrin ground state, and proceeds on a time scale of 3–8 ns, while a minor and slower(≈45 ns) fluorescence lifetime measures the decay of the exciplexes. The results were compared with those earlier obtained with the P(Ala)_nN peptides(n = 0–4) in methanol solution, showing that addition of water does not significantly alter the dynamic relaxation behavior of the systems investigated, but affects the dissipation mechanism of the energy transferred to P. Quenching efficiencies from both fluorescence intensity and fluorescence lifetime measurements follow a different trend as the number of AA units increases, depending on whether AA = Aib or Ala, indicating that there are differences in the structural features of the two series of peptides. Consistently, CD spectral results suggest that the former compounds attain ordered conformations, possibly of the 3₁₀-helical type, while the latter populate α-helical structures to an extent depending on the chain length. The ir data in dilute CD₃OD or CDCl₃ solution confirm this conclusion in that there is an increased percentage of intramolecular H bonds in the P(Aib)_nN as compared to the corresponding P(Ala)_nN peptides. The photophysical results can be well described by a long-range dipole–dipole interaction model, provided the separation distances distribution and mutual orientation of N and P groups are taken into account. The need of using the angular relationships between the probes implies that interconversion among conformational substates of chromophores linkages is slow on the time scale of the transfer process, very likely because of both the amide bond in the linkages and the bulkiness of the donor–acceptor pair. © 1995 John Wiley & Sons, Inc.     

Theoretical ab Initio Study of the Effects of Methylation on Structure and Stability of G:C Watson-Crick Base Pair

Abstract

Methylation of DNA occurs most readily at N(3), N(7), and O(6) of purine bases and N(3) and O(2) of pyrimidines. Methylated bases are continuously formed through endogenous and exogenous mechanisms. The results of a theoretical ab initio study on the methylation of G:C base pair components are reported. The geometries of the local minima were optimized without symmetry restrictions by the gradient procedure at DFT level of theory and were verified by energy second derivative calculations. The standard 6–31G(d) basis set was used. The single-point calculations have been performed at the MP2/6–31G(d,p), MP2/6–31₊₊G(d,p), and MP2/6–311₊₊G(2d,2p) levels of theory. The geometrical parameters, relative stability and counterpoise corrected interaction energies are reported. Also, using a variation-perturbation energy decomposition scheme we have found the vital contributions to the total interaction energy.     

Evolution of 1, 3, 5-trisubstituted bipyrazole scaffold based platinum(II) complexes as a biological active agent

Abstract

Square planar mononuclear platinum(II) complexes having general formula [Pt(Lⁿ)Cl₂], (where, Lⁿ?=?L^1–4) were synthesized with neutral bidentate heterocyclic 1,3,5-trisubstituted bipyrazole based ligands. The synthesized compounds were characterized by physicochemical method such as TGA, molar conductance, micro-elemental analysis and magnetic moment, and spectroscopic method such as, FT-IR, UV–vis, ¹H NMR, ¹³C NMR and mass spectrometry. Biological applications of the compounds were carried out using in vitro brine shrimp lethality bioassay, in vitro antimicrobial study against five different pathogens, and cellular level cytotoxicity against Schizosaccharomyces pombe (S. Pombe) cells. Pt(II) complexes were tested for DNA interaction activities using electronic absorption titration, viscosity measurements study, fluorescence quenching technique and molecular docking assay. Binding constants (K_b) of ligands and complexes were observed in the range of 0.23–1.07?×?10⁵?M^?1 and 0.51–3.13?×?10⁵?M^?1, respectively. Pt(II) complexes (I–IV) display an excellent binding tendency to biomolecule (DNA) and possess comparatively high binding constant (K_b) values than the ligands. The DNA binding study indicate partial intercalative mode of binding in complex-DNA. The gel electrophoresis activity was carried out to examine DNA nuclease property of pUC19 plasmid DNA.     

Biological role of mycorrhizal fungi on the assimilation and transportation of carbon and nitrogen to Anacamptis palustris and Anacamptis laxiflor

Fungal is a physiological trail and its understanding in the assimilation with the transfer of carbon (C) cum nitrogen (N) or (C/N) to orchid-seedlings have not been determined. Labelled stable isotopes ¹³C and ¹⁵N were used to plan the flow of C and N between orchid plants and mycorrhizal connotations in-terms of bulk transfer for C/N. This study attends to comprehend the mechanism, supporting mycorrhizal fungi which influences on orchid-seedling growth. Determined integration and transfer of C/N from amino acids (AA), ammonium nitrate (NH₄NO₃) and sugar for orchid-plant may lead to understand these mechanisms. This current study tries to estimate the importance of organic compounds as a source for C/N over the inorganic-NH₄NO₃. Generally, after begging of germination and when it is found to be associated to the nutrient resource, organic compound enhance the biomass accumulation of two orchid species. AA significantly increase the mass of ¹³C assimilated by two species. With amino acids the concentration of ¹³C in two species was greater than with NH₄NO₃ and sugar. At another phase, amount of ¹⁵N content shoots was a higher value in Anacamptis laxiflora shoots assimilated substantially additional of ¹⁵N with NH₄NO₃ plus sugar compared with ammonium nitrate only. This study showed that two terrestrial orchids species are reliant on organic compounds as a source of carbon and nitrogen more than inorganic compounds.     

Cooperativity effect involving drug–DNA/RNA intermolecular interaction: A B3LYP-D3 and MP2 theoretical investigation on ketoprofen⋯cytosine⋯H2O system

In order to examine the origin of the drug action and design new DNA/RNA-targeted drugs, the cooperativity effect involving drug–DNA/RNA intermolecular interaction in ketoprofen?cytosine?H₂O ternary system were investigated by the B3LYP, B3LYP-D3, and MP2 methods with the 6-311++G(2d,p) basis set. The thermodynamic cooperativity was also evaluated at 310.15 K. The N–H?O, O–H?O, O–H?N, C–H?N, and C–H?O H bonds coexist in ternary complexes. The intermolecular interactions obtained by B3LYP-D3 are close to those calculated by MP2. The steric effects and van der Waals interactions have little influence on the cooperativity effects. The anti-cooperativity effect in ket?cyt?H₂O is far more notable than the cooperativity effect, and the stability of the cyclic structure with anti-cooperativity effect is higher than that of the linear structure with cooperativity effect, as is confirmed by the AIM (atoms in molecules) and RDG (reduced density gradient) analysis. Thus, it can be inferred that, in the presence of H₂O, the anti-cooperativity effect plays a dominant role in the drug–DNA/RNA interaction, and the nature of the hydration in the binding of drugs to DNA/RNA bases is the H-bonding anti-cooperativity effect. Furthermore, the drug always links simultaneously with DNA/RNA base and H₂O, and only in this way can the biological activity of drugs play a role. In most cases, the enthalpy change is the major factor driving the cooperativity, as is different from most of biomacromolecule complexes.     

Coordination chemistry of group 4 metal compounds with mixed-ligand,silyl-linked bis(amidinate) ligand and cyclopentadienyl

The synthesis and characterization of a class of group 4 metal derivatives based on the silyl-linked bis(amidinate) ligands [SiMe₂{NC(Ph)N(2,6-R₂Ph)Li}₂] [L¹ (R = H) and L² (R = Me)] are described. The metal salts coordinated with cyclopentadienyl were used in order to increase the steric hindrance and lower the Lewis acidity of metal centers, which could prevent the N-ligands from rearranging. The tetradentate ligands L¹ and L² reacted with TiCl₂(C₅H₅)₂ to give compounds 1 and 2 in tridentate and bidentate bonding modes, respectively. Treatment of the ligand L¹ with ZrCl₃(C₅H₅) produced the half-sandwich zirconium complex 3. Reactions of the ligands with ZrCl₂(C₅H₅)₂ afforded zirconium compounds 4 and 5, demonstrating the same geometry as 1. Comparing these analogous molecular structures, it suggests that the coordination modes of the N-ligands are variable according to the properties of the metal centers as well as the bulky hindrance of the terminal groups on the seven-membered N–C–N–Si–N–C–N backbone.     

A Tannic Acid–Derived N‐, P‐Codoped Carbon‐Supported Iron‐Based Nanocomposite as an Advanced Trifunctional Electrocatalyst for the Overall Water Splitting Cells and Zinc–Air Batteries

Rational design and construction of a multifunctional electrocatalyst featuring with high efficiency and low cost is fundamentally important to realize new energy technologies. Herein, a trifunctional electrocatalyst composed of FeP_x nanoparticles and Fe–N–C moiety supported on the N‐, P‐codoped carbon (NPC) is masterly synthesized by a facile one‐pot pyrolysis of the mixture of tannic acid, ferrous chloride, and sodium hydrogen phosphate. The synergy of each component in the FeP_x/Fe–N–C/NPC catalyst renders high catalytic activities and excellent durability toward both oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The electrocatalytic performance and practicability of the robust FeP_x/Fe–N–C/NPC catalyst are further investigated under the practical operation conditions. Particularly, the overall water splitting cell assembled by the FeP_x/Fe–N–C/NPC catalyst only requires a voltage of 1.58 V to output the benchmark current density of 10 mA cm^?2, which is superior to that of IrO₂–Pt/C‐based cell. Moreover, the FeP_x/Fe–N–C/NPC‐based zinc–air batteries deliver high round‐trip efficiency and remarkable cycling stability, much better than that of Pt/C–IrO₂ pair‐based batteries. This work offers a new strategy to design and synthesize highly effective multifunctional electrocatalysts using cheaper tannic acid derived carbon as support applied in electrochemical energy devices.     

Design,synthesis, evaluation and molecular modelling studies of some novel 5,6-diphenyl-1,2,4-triazin-3(2H)-ones bearing five-member heterocyclic moieties as potential COX-2 inhibitors: A hybrid pharmacophore approach

A series of novel hybrids comprising of 1,3,4-oxadiazole/thiadiazole and 1,2,4-triazole tethered to 5,6-diphenyl-1,2,4-triazin-3(2H)-one were designed, synthesised and evaluated as COX-2 inhibitors for the treatment of inflammation. The synthesised hybrids were characterised using FT-IR, 1H NMR, 13C NMR, elemental (C,H,N) analyses and assessed for their anti-inflammatory potential by in vitro albumin denaturation assay. Compounds exhibiting activity comparable to indomethacin and celecoxib were further evaluated for in vivo anti-inflammatory activity. Oral administration of promising compounds 3c–3e and 4c–4e did not evoke significant gastric, hepatic and renal toxicity in rats. These potential compounds exhibited reduced malondialdehyde (MDA) content on the gastric mucosa suggesting their protective effects by inhibition of lipid peroxidation. Based on the outcome of in vitro COX assay, compounds 3c–3e and 4c–4e (IC₅₀ 0.60–1.11 μM) elicited an interesting profile as competitive selective COX-2 inhibitors. Further, selected compounds 3e and 4c were found devoid of cardiotoxicity post evaluation on myocardial infarcted rats. The in silico binding mode of the potential compounds into the COX-2 active site through docking and molecular dynamics exemplified their consensual interaction and subsequent COX-2 inhibition with significant implications for structure-based drug design.     

A theoretical investigation into the cooperativity effect between the H∙∙∙O and H∙∙∙F– interactions and electrostatic potential upon 1:2 (F–:N-(Hydroxymethyl)acetamide) ternary-system formation

The cooperativity effects between the O/N–H???F^– anionic hydrogen-bonding and O/N–H???O hydrogen-bonding interactions and electrostatic potentials in the 1:2 (F^–:N-(Hydroxymethyl)acetamide (signed as “ha”)) ternary systems are investigated at the B3LYP/6-311++G** and MP2/6-311++G** levels. A comparison of the cooperativity effect in the “F^–???ha???ha” and “FH???ha^–???ha” systems is also carried out. The result shows that the increase of the H???O interaction energy in the O–H???O–H, N–H???O–H or N–H???O?=?C link is more notable than that in the O–H???O?=?C contact upon ternary-system formation. The cooperativity effect is found in the complex formed by the O/N–H???F^– and O/N–H???O interactions, while the anti-cooperativity effect is present in the system with only the O/N–H???F^– H-bond or the “FH???ha^–???ha” complex by the N^–???H–F contact. Atoms in molecules (AIM) analysis and shift of electron density confirm the existence of cooperativity. The most negative surface electrostatic potential (V _S,min ) correlates well with the interaction energy E′ _{int.(ha???F–)} and synergetic energy E _syn., respectively. The relationship between the change of V _S,min (i.e., ΔV _S,min ) and E _syn. is also found.

Theoretical study of the effect of N-oxides on the performances of energetic compounds

In order to study the effects of N-oxide on structure and performance, six categories of energetic compounds were systemically investigated. The results indicated that the C–C bonds in the rings were shortened, and the C–N bonds close to the N?→?O bond were elongated when N atoms was oxidized to form N?→?O bonds. N?→?O bonds can increase the densities of most categories of compounds, and the increment will increase with the number of N?→?O bonds. As to their detonation performances, almost all categories of compounds had an increased trend, except for some NO₂-, NHNO₂- and ONO₂-substituted compounds. The contribution of 1,2,3,4-tetrazine and 1,2,4,5-tetrazine to performances was better than that of pyrazine and [1,2,5] oxadiazolo [3,4-b] pyrazine on the whole, and the groups, especially energetic groups, made a huge contribution to performance. When R was a NH₂ or ONO₂ group, all compounds had lower impact sensitivities, and thus represent candidates for novel energetic compounds. However, other than the sixth category of compounds, all compounds had higher impact sensitivities when R was a NO₂ or NHNO₂ group, and have little significance in application.

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Graphical abstract To study the effects of N-oxide on the structure and performance of energetic compounds, and to propose theoretical guidance for the design of novel compounds, the six categories (94 species) listed in the figure were investigated systemically by density functional theory methods and some empirical formulae

     

Synthesis and spectroscopic characterization study of new palladium complexes containing bioactive O,O-chelated ligands: evaluation of the DNA/protein BSA interaction,in vitro antitumoural activity and molecular docking

[Pd{(C,N)–C₆H₄CH₂NH(Et) (Qu)] (2) and [Pd{(C,N)–C₆H₄CH₂NH(Et) (Nar)] (3) (Qu = Quercetin, Nar = Naringin) mononuclear palladium (II) complexes have been synthesized and characterized using elemental analysis, IR and electronic spectroscopy. The interaction of the prepared complexes with calf thymus DNA and bovine serum albumin (BSA), monitored by UV–visible and fluorescence titrations, respectively, have been carried out to better understand the mode of their action under biological conditions. Intercalative binding mode between the complexes and DNA is suggested by the binding constant (K_b) values of 2.5 × 10⁶ and 3.2 × 10⁶ for complexes 2 and 3, respectively. In particular, the in vitro cytotoxicity of the complexes on two cancer cells lines (bladder carcinoma TCC and breast cancer MCF7) showed that the compounds had broad spectrum, anti-cancer activity with low IC₅₀ values and the order of in vitro anticancer activities is consistent with the DNA-binding affinities. In the meantime, the quenching of tryptophan emission with the addition of complexes using BSA as a model protein indicated the protein binding ability. The quenching mechanisms of BSA by the complexes were static processes, according to the results obtained. The competitive binding using Warfarin, Digoxin and Ibuprofen site markers, which contain definite biding sites, demonstrated that the complexes bind to site I on BSA. Ultimately, the binding sites of DNA and BSA with the complexes have been determined by molecular modelling studies.     

Correction to: An analysis of structural phase transition and allied properties of cubic ReN and MoN compounds

The dependence of sensitivity of an explosive on its molecular structure may be mainly attributed to the molecular deformability, which can be expressed by some characteristic parameters, resonance energy for aromatic an explosive, strain energy for a strained-ring or strained-cage explosive, large π-π separation energy for a large π-π linked-explosive, bond rotational energy barriers of C–NO₂, N–NO₂, O–NO₂ for C–NO₂, N–NO₂, O–NO₂ bond-based explosives, and so on. Molecular polarizability of an explosive is also an important molecular deformability index, which can be effectively used to compare impact sensitivities of explosive’s isomers, isoelectronic species, and similar structures. Interestingly, comparing the molecular polarizabilities under external electric fields with different energy levels of isomeric N₂₀(Ih) and N₂₀(D_3d) clusters and the Mo₂N₂₀ and Re₂N₂₀ complex compounds, it is found that there are different energy thresholds of significant molecular expansion.

     

Soil C and N dynamics within a precipitation gradient in Mediterranean eucalypt plantations

Soil C and N dynamics were evaluated in five eucalypt plantations within a precipitation gradient (500–2,000 mm) in Portugal. Soil physical and chemical properties, total and labile (particulate organic matter, hydrolyzable, hot water soluble and microbial) soil C and N pools, and C and N mineralization were measured to characterize the C and N dynamics and their controlling factors within this gradient. Contents of total and labile soil organic C and N were positively correlated with the mean annual precipitation. A similar relationship was observed for net N mineralization (anaerobic and long-term aerobic incubation), gross N mineralization (¹⁵N isotope dilution technique) and C mineralization. In contrast, rates of C and N mineralization (per unit of C and N) were higher in the driest sites due to their higher proportion of particulate organic matter C. Net and gross N mineralization were strongly correlated and showed similar controlling factors (mean annual precipitation, total and labile C and N and extractable P contents), suggesting that net N mineralization during long-term aerobic incubation reflects gross N transformations. Although, gross NO₃–N production and gross NO₃–N immobilization were observed in all sites, net nitrification in the drier sites was not observed in the first weeks of the study. Our results suggest that, under Mediterranean conditions, mean annual precipitation is the major factor determining the C and N dynamics in soils with Eucalyptus plantations.