Ab initio and density functional theory (DFT) studies on triflic acid with water and protonated water clusters

The structure, stability and infrared spectral signatures of triflic acid (TA) with water clusters (W_n) and protonated water clusters (TAH⁺W_n, n?=?1???6) were computed using DFT and MP2 methods. Our calculations show that a minimum of three water molecules are necessary to stabilize the dissociated zwitterionic form of TA. It can be seen from the results that there is no significant movement of protons in smaller (n?=?1 and 2) and linear (n?=?1 – 6) types of water clusters. Further, the geometries of TAW_n clusters first form a neutral pair (NP) to contact ion pair (CIP), then form a solvent separated ion pair (SSIP) in a water hexamer. These findings reveal that proton transfer may take place through NP to CIP and then CIP to SSIP. The calculated binding energies (BEs) of ion pair clusters is always higher than that of NP clusters (i.e., more stable than the NP). Existing excess proton linear chain clusters transfer a proton to adjacent water molecules via a Grotthuss mechanism, whereas the same isomers in the branched motifs do not conduct protons. Examination of geometrical parameters and infrared frequencies reveals hydronium ion (H₃O⁺ also called Eigen cation) formation in both TAW_n and protonated TAW_n clusters. The stability of Eigen water clusters is three times higher than that of other non-Eigen water clusters. Our study shows clearly that formation of ion pairs in TAW_n and TAH⁺W_n clusters greatly favors proton transfer to neighboring water molecules and also enhances the stability of these complexes.     

Structural elucidation,theoretical investigation,biological screening and molecular docking studies of metal(II) complexes of NN donor ligand derived from 4-(2-aminopyridin-3-methylene)aminobenzoic acid

Complexes of 4-(((2-aminopyridin-3-yl)methylene)amino)benzoic acid ligand with cobalt(II) (1), nickel(II) (2), copper(II) (3), zinc(II) (4) and palladium(II) (5) are synthesized and characterized by using different spectroscopic methods like, UV–Visible, infrared, ¹H, ¹³C NMR, molar conductance, ESR and elemental analysis. Quantum chemical computations were made using DFT (density functional theory), B3LYP functional and 6-31+?+G(d,p)/SDD basis set in order to determine optimized structure parameters, frontier molecular orbital parameters and NLO properties. Based on DFT and experimental evidence, the complexes ensured that the octahedral geometry have been proposed for complexes 1, 2 and 4, square planar for complexes 3 and 5. All the complexes showed only residual molar conductance values and hence they were considered as non-electrolytes in DMF. In addition, the anti-proliferative activity of the compounds was evaluated against different human cancer cell lines (IMR-32, MCF-7, COLO205, A549, HeLa and HEK 293) and cisplatin is used as a reference drug. Compounds 1 and 4 showed remarkable cytotoxicity in five cancer cell lines tested except MCF-7. Also, the compounds were examined for their in vitro antimicrobial and scavenging activities. The molecular docking results are well corroborated with the experimental anticancer activity results.

     

Steric hindrance effect of the equatorial ligand on Fe(IV)O and Ru(IV)O complexes: a density functional study

The geometric structures and mechanisms for hydrogen abstraction from cyclohexane for four high-valent complexes, [Fe^IV(O)(TMC)(NCMe)]²⁺ (where TMC is 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane; 1-NCMe), the inverted isomer [Fe^IV(NCMe)(TMC)(O)]²⁺ (2-NCMe), [Ru^IV(O)(TMC)(NCMe)]²⁺ (the ruthenium analogue of 1-NCMe; 3-NCMe), and the inverted isomer [Ru^IV(NCMe)(TMC)(O)]²⁺ (4-NCMe), were investigated using density functional theory. The axial NCMe ligand was found to be sterically more hindered in 2-NCMe than in 1-NCMe, which is in accord with the calculated results that the Fe–L_axial distance is longer in the former. Both 1-NCMe and 2-NCMe are capable of hydrogen abstraction from cyclohexane via two-state reactivity patterns. In contrast, 3-NCMe and 4-NCMe react with cyclohexane by a single-state mechanism. The reaction pathways computed reveal that 2-NCMe is more reactive than 1-NCMe, in agreement with experimental results, whereas the reactivity of 3-NCMe and 4-NCMe shows little dependence on whether the oxo unit is syn or anti to the four N-methyl groups. Our analysis shows that along the reaction pathway for 2-NCMe in the triplet spin state, the NCMe ligand moves away from the iron center, and therefore the energy of the s_z^{* 2} sigma_{z}^{* 2} (α-spin) orbital decreases and an electron is transferred to this orbital. Finally, we calculated the kinetic isotope effect and investigated the relationship between this effect and reaction barriers.     

Vibrational (FT-IR and FT-Raman) spectral investigations of 7-aminoflavone with density functional theoretical simulations

FT-Raman and FT-IR spectra of the 7-aminoflavone have been recorded and analysed. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. The various intramolecular interactions that are responsible for stabilisation of the molecule were revealed by natural bond orbital analysis. The obtained vibrational wavenumbers and optimised geometric parameters were observed to be in good agreement with the experimental data. The carbonyl stretching vibrations have been lowered due to conjugation and hydrogen bonding in the molecules.     

Synthesis, characterization and catalytic oxidation of cyclohexane using a novel host (zeolite-Y)/guest (binuclear transition metal complexes) nanocomposite materials

Transition metal (M = Mn(II), Co(II), Ni(II) and Cu(II)) complexes with octahydro-Schiff base (H₄-N₄O₄) = 2,7,13,18-tetramethyl-3,6,14,17-tetraazatricyclo-[17.3.1.1]-tetracosa-1(23),2,6,8(24),9,11,13,17,19,21-decaene-9,11,20,22-tetraol; H₄([H]₈-N₄O₄) = 2,7,13,,18-tetramethyl-3,6,14,17-tetraazatricyclo-[17.13.1.1.]-tetracosa-1(23),8(24),9,11,19,21-hexane-9,11,20,22-tetraol) have been encapsulated in nanopores of zeolite-Y; [M([H]₈-N₄O₄)]@NaY; with Flexible Ligand Method (FLM) for the first time. The new Host-Guest Nanocomposite Materials (HGNM) was characterized by several techniques: chemical analysis, spectroscopic methods (DRS, FT-IR and UV/Vis), BET technique, conductometric and magnetic measurements. The catalytic activities for oxidation of cyclohexane with HGNM complexes are reported. Zeolite encapsulated octahydro-Schiff base copper(II) complex; [Cu([H]₈-N₄O₄)]@NaY; was found to be more active than the corresponding cobalt(II), manganese(II) and nickel(II) complexes for cyclohexane oxidation. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. HGNM are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts. The encapsulated catalysts systems; [M([H]₈-N₄O₄)]@NaY; were more active than the corresponding neat complexes; [M([H]₈-N₄O₄))].     

Tuning the electronic and photophysical properties of platinum(II) complexes through ancillary ligand modification: a theoretical study

In this work, six Pt(II) complexes have been studied via density functional theory (DFT)/time-dependent DFT caculations to explore the influence of different ancillary ligand on electron structures, photophysical properties and radiative decay processes. Moreover, the self-consistent spin–orbit coupling TDDFT was used to calculate zero-field splitting, radiative rate and radiative lifetime to unveil the radiative deactivation processes for these complexes. The results indicated that [Pt(ppy)(ppz)] (ppy = 2-phenylpyridine and ppz = 5-(2-pyridyl)-pyrazole) has a higher radiative decay rate constant and a smaller nonradiative decayrate constant than that of [Pt(ppy)(acac)] (acac = acetylacetonate). Furthermore, complex 5, with dimesityboron added on the 3′-position of the pyrazole ring in [Pt(ppy)(ppz)], shows great potential to serve as an efficient blue-green light emitter in OLED.     

Synthesis, crystal structures and density functional theory study of dimeric copper(II) complexes of a tridentate Schiff-base ligand

Oxalate- or 4,4′-bipyridine-bridged dimeric copper(II) complexes, [Cu₂L₂(μ-ox)] (1) and [Cu₂L₂(μ-bipy)](BF₄)₂ (2) [where ox = oxalate, bipy = 4,4′-bipyridine, HL = N-(1H-pyrrol-2-ylmethylene)-2-pyridineethanamine, L⁻ = HL−H⁺], have been synthesised and characterised by elemental analysis, IR, UV-Vis and single crystal X-ray diffraction. Crystal structure determinations carried out on 1 and 2 reveal that 1 is an oxalate-bridged centrosymmetrical square pyramidal dimeric copper(II) complex while 2 is a 4,4′-bipyridine-bridged non-centrosymmetric square planar dinuclear copper(II) complex. Comparison of the optimised geometries with the corresponding crystal structures suggests that the B3LYP/LANL2DZ level can reproduce the structures of 1 and 2 on the whole. The electronic spectra of 1 and 2 predicted by B3LYP/LANL2DZ method show some blue shifts compared with their experimental data. Thermal analysis carried out on 1 shows that there is only one exothermal peak at about 260 °C and the residue is presumably Cu₂O₄N₆.     

The effect of prey density and host plant characteristics on oviposition and fertility in Anthocoris confusus (Reuter)

• 1 Anthocoris confusus females show the greatest egg production when fed on eight adult Aulacorthum circumflexus per day. Prey densities below six result in a marked fall off in egg production.
• 2 Low prey densities result in reduced egg fertility and a decrease in oviposition period.
• 3 A.confusus females oviposit on those parts of a broad bean plant which support the highest aphid densities. This increases the probability of survival of the emerging nymphs.
• 4 Females are also able to distinguish between young, fully turgid, plants and older, more flaccid, plants and oviposit preferentially in the younger ones. Thus the eggs develop before the plant dies.

     

Interactions of hydrated IIa and IIb group metal cations with thioguanine-cytosine DNA base pair: Ab initio and density functional theory investigation of polarization effects, differences among cations, and flexibility of the cation hydration shell.

The structures and energies of the thioguanine-cytosine Watson-Crick (thioGC WC) base pair interacting with hydrated IIa (Mg2+, Ca2+, Ba2+) and IIb group (Zn2+, Cd2+, Hg2+) cations have been studied using ab initio techniques. Furthermore, complexes between guanine and thioguanine with hydrated cations have been characterized assuming various structures of the hydration shells. The complexes of the thioGC WC base pair with hydrated cations have similar properties as the previously studied GC WC base pair. There is substantial polarization stabilization of the base pairing due to cation binding which amounts to 7 - 11 kcal/mol. Soft Cd2+ and Hg2+ cations have a uniquely strong interaction with the thiogroup and induce substantial nonplanarity of the pairing. The thiogroup tends to reduce the number of water molecules in the first hydration shell of the cation. All complexes were optimized within the Hartree-Fock (HF) approximation while their energetics has been evaluated using the second-order Moller-Plesset perturbational method (MP2). All interaction energy evaluations and a substantial portion of the optimizations of the hydrated cation-(thio)guanine complexes have been repeated using Becke-3LYP Density Functional Theory method. All three approximations used (HF, Becke-3LYP, and MP2) give qualitatively the same results for the present cationic complexes. The results demonstrate specific differences among the cations and provide a set of reference structures and energies for verification and/or parametrization of empirical potentials and other theoretical methods.     

Effect of metal ion complexation and chalcogen donor identity on the antiproliferative activity of 2-acetylpyridine N,N-dimethyl(chalcogen)semicarbazones

Three chalcogensemicarbazones, viz., 2-acetylpyridine N,N-dimethylsemicarbazone (HL(1)), 2-acetylpyridine N,N-dimethylthiosemicarbazone (HL(2)) and 2-acetylpyridine N,N-dimethylselenosemicarbazone (HL(3)), their corresponding gallium(III) complexes [Ga(L(1-3))(2)]PF(6) and the ruthenium(III) compound [Ru(L(2))(2)]PF(6) have been prepared and characterised by X-ray crystallography and spectroscopic techniques (IR, UV/vis, (1)H, (13)C, (15)N, (77)Se NMR) in order to elucidate the effect of metal ion complexation and chalcogen donor identity on the cytotoxicity of chalcogensemicarbazones in two human tumour cell lines 41M (ovarian carcinoma) and SK-BR-3 (mammary carcinoma).     

Effect of graft-versus-host disease (GVHD) on host hematopoietic progenitor cells is mediated by Fas-Fas ligand interactions but this does not explain the effect of GVHD on donor cells.

The acute graft-versus-host disease (GVHD) generated in BDF1 mice by the injection of spleen cells from the C57BL/6 parental strain induces a direct cell-mediated attack on host lymphohematopoietic populations, resulting in the reconstitution of the host with donor hematopoietic stem cells. We examined the effect of GVHD on the donor and host hematopoiesis in parental-induced acute GVHD. The bone marrow was hypoplastic and the number of hematopoietic progenitor cells significantly decreased at 4 weeks after GVHD induction. However, extramedullary splenic hematopoiesis was present and the number of hematopoietic progenitor cells in the spleen significantly increased at this time. Fas expression on the host spleen cells and bone marrow cells significantly increased during weeks 2 to 8 of GVHD. Host cell incubation with anti-Fas Ab induced apoptosis, and the number of hematopoietic progenitor cells decreased during these weeks. A significant correlation between the augmented Fas expression on host bone marrow cells and the decreased number of host bone marrow cells by acute GVHD was observed. Furthermore, the injection of Fas ligand (FasL)-deficient B6/gld spleen cells failed to affect host bone marrow cells. Although Fas expression on repopulating donor cells also increased, Fas-induced apoptosis by the repopulating donor cells was not remarkable until 12 weeks, when more than 90% of the cells were donor cells. The number of hematopoietic progenitor cells in the bone marrow and the spleen by the repopulating donor cells, however, decreased over an extended time during acute GVHD. This suggests that Fas-FasL interactions may regulate suppression of host hematopoietic cells but not of donor hematopoietic cells. Hematopoietic dysfunctions caused by the reconstituted donor cells are independent to Fas-FasL interactions and persisted for a long time during parental-induced acute GVHD.     

The effect of temperature acclimation on myocardial beta-adrenoceptor density and ligand binding affinity in African catfish (Claris gariepinus)

This study assessed the effects of temperature acclimation on myocardial beta-adrenoceptor density (B(max)) and binding affinity (K(d)) in African catfish (Claris gariepinus) acclimated to 15, 22 and 32 degrees C. B(max) values were not significantly different (P > 0.05) among the three acclimation groups. Conversely, the K(d) value of the 32 degrees C acclimation group (K(d) = 0.88) was significantly higher (P = 0.002) than both the 15 degrees C (K(d) = 0.48) and 22 degrees C (K(d) = 0.46) acclimation groups. In addition, K(d) of rainbow trout (Oncorhynchus mykiss) was significantly lower (P < 0.001) and B(max) significantly higher (P < 0.05) than that of African catfish at all three acclimation temperatures. These results contrast with those reported previously for temperate species, in which B(max) is inversely related to acclimation temperature, and counter a previous suggestion that B(max) is higher in tropical versus temperate species.     

Synthesis,spectral characterisation and cytotoxic effect of metal complexes of 2-(2-(4-carboxyphenyl)guanidino) acetic acid ligand

Abstract

A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Sr(II), Hg(II), Ag(I), Tl(I) and UO₂(II) complexes of 2-(2-(4-carboxyphenyl)guanidino)acetic acid ligand have been synthesised and characterised by elemental analyses, IR, UV-Vis spectra, mass spectra (ligand and its zinc(II) complex), ¹H NMR spectra (ligand and its mercury(II) complex), magnetic moments, conductances, thermal analyses (DTA and TGA) and ESR measurements. The IR data show that, the ligand behaves as neutral tridentate, (2), [(H_{2 L}L)_{3 C}Cu_{2 (}(OAc)_{4 (}(H_{2 O}O)_{2 ]} ], neutral bidentate, (3), [(H_2LL)Cu(OAc)_2]].1/2H_2OO, (13), [(HL)_2CCuCl₂₍(H_2OO)_2]], (17), [(H_2LL)Cu(OOSO₂₎)(H_2OO)J,dibasic hexadentate, (4), [(L) Ni₄₍(OAc)₆₍(H_2OO)J.4H_2OO, (5), [(L)Mn4(OAc)6(H2O)10]. 4H2O, (6), [(L)Co4(OAc)6(H2O)10] . 4H2O, monobasic bidentate, (7), [(HL)(UO2)(OAc)(H2O)3], (12), [(HL)2Cu], (15), [(HL)2Fe2(Cl4)(H2O)2]. 7H2O, (16), [(HL)2Cr2(Cl4)(H2O)2]. 7H2O, (21 ), [(H2L)Cd (OOSO2)(H2O)3]. 2H2O, monobasic tridentate, (8), [(L)_2HHg₂₍(OAc)₂ (H2O)6].H2O, (9), [(L)2Zn2(OAc)2(H2O)6].H2O, (10), [(L) _2ZZn₂₍(OAc)₂₍(H_2OO)_6]].H_2OO, (11), [(L)Tl4(OAc)3 (H2O)6], (18), [(HL)(OH)Cr2(SO4)2(H2O)5]. H2O, (19), [(HL)3Ag3NO3], or dibasic tridentate, (14), [(L) Sr(Cl)_{20 (}(H_{2 O}O)_{24 ]}], (20), [(L)_{3 C}Cu (H_{2 O}O)_{2 ]} ]. Molar conductances in DMF indicate that, the complexes are non-electrolyte. The ESR spectra of Cu(II) complexes (2), (3) and (20) at room temperature show axial type symmetry with g_// > g_-> 2.00, indicating a d_(x2-y2) ground state with significant covalent bond character in an octahedral or square planar geometry. However, Cu(II) complexes (12) and (13) show isotropic type, indicating square planar and octahedral structure. Complexes Mn(II) (5) and Co(II) (6) show broad signals in the low field region indicating spin exchange interaction take place between metal(II) ion. Hg(II) complex (9), Tl(I) complex (11), Cr(III) complex (16), Cu(II) complex (17) and Cd(II) complex (21) showed potential antiproliferative activity where they showed inhibitory effect on breast carcinoma (MCF-7 cell line) in comparing with the standard drug.     

Ab initio calculation of the geometries, stabilities, and electronic properties for the bimetallic Be2Au(n) (n = 1-9) clusters: comparison with pure gold clusters

Ab initio methods based on density functional theory at BP86 level were applied to the study of the geometrical structures, relative stabilities, and electronic properties of small bimetallic Be₂Au _n (n = 1–9) clusters. The optimized geometries reveal that the most stable isomers have 3D structures at n = 3, 5, 7, 8, and 9. Here, the relative stabilities were investigated in terms of the averaged atomic binding energies, fragmentation energies and second-order difference of energies. The results show that the planar Be₂Au₄ structure is the most stable structure for Be₂Au _n clusters. The HOMO−LUMO gap, vertical ionization potential, vertical electron affinity and chemical hardness exhibit a pronounced even–odd alternating phenomenon. In addition, charge transfer and natural electron configuration were analyzed and compared.     

Life tables of Habrobracon hebetor (Hymenoptera: Braconidae) parasitizing Anagasta kuehniella and Plodia interpunctella (Lepidoptera: Pyralidae): effect of host density

The reproductive performance of the parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) against the moths Anagasta kuehniella Zeller and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) was studied in the laboratory. The analysis was based on the comparison of parasitoid's life table parameters related to those of its hosts at various conditions of host density (daily supply of 1, 5, 15, and 30 full-grown host larvae). The estimated parameters were the intrinsic rate of natural increase (rm), the net reproductive rate (R0), the mean generation time (G), the finite capacity of increase (lambda), the gross reproductive rate (GRR), the doubling time (DT), the reproductive value (Vx), and the life expectancy (ex). The rm of H. hebetor proved to be significantly higher than those of its hosts at all host densities. When only one host per day was supplied, the wasp had the lowest reproductive potential, whereas it was maximized when 15 hosts per day were exposed. Maximum values of R0 and GRR were obtained at densities > or =15 host larvae per day. Any increase in host supply above this threshold did not cause significant changes in life table parameters. Variation of rm as a function of host density can be described by the linear regression. Sex ratio of wasp progeny (females/total) ranged from 0.36 to 0.42, irrespective of host density or species. Newly emerged adults recorded maximum ex and Vx. The results of this study can be used to improve mass rearing programs and inoculative release applications of H. hebetor against moth pests of stored products.     

Calcium(II) site specificity: effect of size and charge on metal ion binding to an EF-hand-like site

The molecular mechanisms by which protein Ca(II) sites selectively bind Ca(II) even in the presence of high concentrations of other metals, particularly Na(I), K(I), and Mg(II), have not been fully described. The single Ca(II) site of the Escherichia coli receptor for D-galactose and D-glucose (GGR) is structurally related to the eukaryotic EF-hand Ca(II) sites and is ideally suited as a model for understanding the structural and electrostatic basis of Ca(II) specificity. Metal binding to the bacterial site was monitored by a Tb(III) phosphorescence assay: Ca(II) in the site was replaced with Tb(III), which was then selectively excited by energy transfer from protein tryptophans. Photons emitted from the bound Tb(III) enabled specific detection of this substrate; for other metals binding was detected by competitive displacement of Tb(III). Representative spherical metal ions from groups IA, IIA, and IIIA and the lanthanides were chosen to study the effects of metal ion size and charge on the affinity of metal binding. A dissociation constant was measured for each metal, yielding a range of KD's spanning over 6 orders of magnitude. Monovalent metal ions of group IA exhibited very low affinities. Divalent group IIA metal ions exhibited affinities related to their size, with optimal binding at an effective ionic radius between those of Mg(II) (0.81 A) and Ca(II) (1.06 A). Trivalent metal ions of group IIIA and the lanthanides also exhibited size-dependent affinities, with an optimal effective ionic radius between those of Sc(III) (0.81 A) and Yb(III) (0.925 A). The results indicate that the GGR site selects metal ions on the basis of both charge and size.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of ancillary ligand chirality and phenanthroline functional group substitution on the cytotoxicity of platinum(II)-based metallointercalators

Fifteen platinum(II)-based metallointercalators have been synthesised that utilise substituted 1,10-phenanthroline (phen) ligands, including 5-chloro-1,10-phenanthroline (5-Cl-phen), 5-methyl-1,10-phenanthroline (5-CH3-phen), 5-amino-1,10-phenanthroline (5-NH2-phen), 5-nitro-1,10-phenanthroline (5-NO2-phen) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), and achiral ethylenediamine (en) and the chiral ancillary ligands 1S,2S-diaminocyclohexane (S,S-dach) and 1R,2R-diaminocyclohexane (R,R-dach). Their cytotoxicity in the L1210 murine leukaemia cell line was determined using growth inhibition assays. The most cytotoxic metal complexes are those that contain S,S-dach ancillary ligands and 5-CH3-phen intercalating ligands. One metallointercalator [Pt(5-CH3-phen)(S,S-dach)]Cl2 (5MESS), displays a 5-10-fold increase in cytotoxicity compared to the clinical agent cisplatin. From DNA binding experiments there appears to be no significant difference between any of the metal complexes, indicating that neither DNA binding affinity nor the mode of binding/DNA adduct formed is the sole determinant of the cytotoxicity of this family of platinum(II)-based metallointercalators.     

Supramolecular chirality induction in bis(zinc porphyrin) by amino acid derivatives: rationalization and applications of the ligand bulkiness effect

The achiral syn conformer (face-to-face) of the ethane-bridged bis(zinc porphyrin) (syn-ZnD) transforms into the corresponding chiral extended anti bis-ligated species (anti-ZnD.L2) in the presence of enantiopure ligands (L: amino acid derivatives). The mechanism of the supramolecular chirality induction is based on chiral ligand binding to zinc porphyrins and subsequent formation of either right- or left-handed screw structures in anti-ZnD.L2. The screw structure formation arises from steric interactions between the bulkiest substituent at the asymmetric carbon of the ligand and the peripheral ethyl groups of the neighboring porphyrin ring directed towards the covalent bridge. The sign and amplitude of the induced circular dichroism (CD) are dependent on the steric bulk of the substituents at the chiral center. The greater difference in size between the chiral center's substituents gives the stronger induced CD signal. Rationalization of the ligand bulkiness effect on chirality induction by amino acid derivatives, application of this supramolecular system for the determination of ligand absolute configuration, and relative bulkiness of the substituents at the asymmetric carbon are discussed.     

Effect of host species,host nest density and nest size on the occurrence of the shining guest ant <Emphasis Type="Italic">Formicoxenus nitidulus</Emphasis> (Hymenoptera: Formicidae)

Understanding habitat requirements of species is important in conservation. As an obligate ant nest associate, the survival of the globally vulnerable shining guest ant, Formicoxenus nitidulus, is strictly tied to that of its hosts (mound building Formica ants). We investigated how host species, nest density, inter-nest distance and nest mound size relate to the occurrence of F. nitidulus. In total, 166 red wood ant nests were surveyed in SW Finland (120 Formica polyctena, 25 F. rufa, 14 F. aquilonia, 5 F. pratensis, and 2 F. lugubris). Overall, F. nitidulus was found in 60% of the nests. For the actual analysis, only F. polyctena and F. rufa nests were included due to the small number of other nests. F. nitidulus was more likely to be found among F. polyctena than F. rufa. Also, while inter-nest distance was not important, a high nest density, commonly found in polydomous (multi-nest) wood ant colonies, was beneficial for F. nitidulus. The guest ant was also more likely to be found in large host nests than small nests. Thus, our results show that the best habitat for the guest ant is a dense population of host nest mounds with a high proportion of large mounds. Conservation efforts should be directed at keeping the quality of the red wood ant habitats high to preserve their current populations and to increase colonization. This will not only benefit the guest ant, but also a plethora of other species, and help in maintaining the biodiversity of forests.