Diel variation of the cellular carbon to nitrogen ratio of Chlorella autotrophica (Chlorophyta) growing in phosphorus‐ and nitrogen‐limited continuous cultures

We investigated the relationship between daily growth rates and diel variation of carbon (C) metabolism and C to nitrogen (N) ratio under P‐ and N‐limitation in the green algae Chlorella autotrophica. To do this, continuous cultures of C. autotrophica were maintained in a cyclostat culture system under 14:10 light:dark cycle over a series of P‐ and N‐limited growth rates. Cell abundance, together with cell size, as reflected by side scatter signal from flow cytometric analysis demonstrated a synchronized diel pattern with cell division occurring at night. Under either type of nutrient limitation, the cellular C:N ratio increased through the light period and decreased through the dark period over all growth rates, indicating a higher diel variation of C metabolism than that of N. Daily average cellular C:N ratios were higher at lower dilution rates under both types of nutrient limitation but cell enlargement was only observed at lower dilution rates under P‐limitation. Carbon specific growth rates during the dark period positively correlated with cellular daily growth rates (dilution rates), with net loss of C during night at the lowest growth rates under N‐limitation. Under P‐limitation, dark C specific growth rates were close to zero at low dilution rates but also exhibited an increasing trend at high dilution rates. In general, diel variations of cellular C:N were low when dark C specific growth rates were high. This result indicated that the fast growing cells performed dark C assimilation at high rates, hence diminished the uncoupling of C and N metabolism at night.     

Extensive polymorphism and geographical variation at a positively selected MHC class II B gene of the lesser kestrel (Falco naumanni)

Understanding the selective forces that shape genetic variation in natural populations remains a high priority in evolutionary biology. Genes at the major histocompatibility complex (MHC) have become excellent models for the investigation of adaptive variation and natural selection because of their crucial role in fighting off pathogens. Here we present one of the first data sets examining patterns of MHC variation in wild populations of a bird of prey, the lesser kestrel, Falco naumanni . We report extensive polymorphism at the second exon of a putatively functional MHC class II gene, Fana- DAB*1. Overall, 103 alleles were isolated from 121 individuals sampled from Spain to Kazakhstan. Bayesian inference of diversifying selection suggests that several amino acid sites may have experienced strong positive selection (ω = 4.02 per codon). The analysis also suggests a prominent role of recombination in generating and maintaining MHC diversity (ρ = 4 Nc  = 0.389 per codon, θ = 0.017 per codon). Both the Fana -DAB*1 locus and a set of eight polymorphic microsatellite markers revealed an isolation-by-distance pattern across the Western Palaearctic ( r  = 0.67; P  = 0.01 and r  = 0.50; P  = 0.04, respectively). Nonetheless, geographical variation at the MHC contrasts with relatively uniform distributions in the frequencies of microsatellite alleles. In addition, we found lower fixation rates in the MHC than those predicted by genetic drift after controlling for neutral mitochondrial sequences. Our results therefore underscore the role of balancing selection as well as spatial variations in parasite-mediated selection regimes in shaping MHC diversity when gene flow is limited.     

DNA-fiber EPR spectroscopy as a tool to study DNA-metal complex interactions: DNA binding of hydrated Cu(II) ions and Cu(II) complexes of amino acids and peptides

DNA-fiber EPR spectroscopy and its application to studies of the DNA binding orientation and dynamic properties of Cu(II) ions and their complexes with amino acids and peptides are reviewed. Cu(II) ions bind in at least two different binding modes; one mode was mobile while the other mode fixed the orientation of the coordination plane. The hydroxyl groups of L-Ser and L-Thr fixed the coordination plane of their respective Cu(II) complexes parallel to the DNA base pair plane, whereas Cu(II) complexes of Lys and Arg induced several binding modes, depending on the tertiary structure of the DNA and the chirality of the amino acids. Unusually broadened signals observed for the His complex were assigned to a mono-L-His complex stacked stereospecifically along the DNA double helix. In comparison, Cu(II). Xaa-Xaa' -His type complexes oriented in the minor groove with different affinities and extents of randomness depending on the Xaa-Xaa' sequence and the chirality of Xaa or Xaa' while the C-terminal Xaa residues in Cu(II).Arg-Gly-His-Xaa (Xaa=L-Leu or L-Glu) decreased the stereospecificity and the stability of the complexes bound to DNA. In contrast to Xaa-Xaa'- His complexes, the coordination planes of Cu(II).Gly-L-His-Gly and Cu(II).Gly-L-His-L-Lys complexes were found to lie parallel to the DNA-fiber axis. Dinuclear Cu(II).carnosine complexes were also shown to bind to DNA stereospecifically.     

Analysis of the contribution of receptor subdomains to the cooperative binding and internalization of transforming growth factor-beta (TGF-beta) type I and type II receptors

The mechanistic basis underlying the striking cooperativity observed for the assembly of TGF-β family ligand/receptor complexes is not well understood. We report here an investigation in which we used a novel ligand sequestration assay, in combination with immunofluorescent light microscopy and flow cytometry analyses, to examine and quantify cooperative assembly of TGF-β ligand/receptor complexes on the cell surface, as well as ligand/receptor complex internalization. We analyzed the roles played by the ecto/transmembrane (ecto/TM) domains and endodomains of RI and RII TGF-β receptors in these processes by transfecting 293 or HeLa cells with different combinations of receptor mutants. We found that the ecto/TM domains of RII and RI cooperated together to promote the formation of cell surface receptor/ligand complexes. Furthermore, in agreement with the recently determined structure of the TGF-β3/RII ectodomain/RI ectodomain complex [J. Groppe, C.S. Hinck, P. Samavarchi-Tehrani, C. Zubieta, J.P. Schuermann, A.B. Taylor, P.M. Schwarz, J.L. Wrana, A.P. Hinck, Cooperative assembly of TGF-beta superfamily signaling complexes is mediated by two disparate mechanisms and distinct modes of receptor binding, Mol. Cell 29 (2008) 157–168], we observed that the N-terminus of the RII ectodomain was required for full assembly. With respect to endodomains, we found that the RI endodomain enhanced cooperative complex assembly at the cell surface, whereas both the RI and RII endodomains enhanced internalization. Finally, we observed that ligand/receptor internalization, but not complex assembly at the cell surface, was partly raft-dependent. In light of these results, currently proposed mechanisms of cooperative ligand/receptor assembly are discussed.     

Mechanism of lectin-cell interactions: thermodynamic and kinetic analysis of the binding of winged bean acidic lectin (WBA II) to human erythrocytes.

In order to identify the forces involved in the binding and to understand the mechanism involved, equilibrium and kinetic studies were performed on the binding of the winged bean acidic lectin to human erythrocytes. The magnitudes of delta S and delta H were positive and negative respectively, an observation differing markedly from the lectin-simple sugar interactions where delta S and delta H are generally negative. Analysis of the sign and magnitudes of these values indicate that ionic and hydrogen bonded interactions prevail over hydrophobic interactions resulting in net -ve delta H (-37.12 kJ.mol-1) and +ve delta S (14.4 J.mole-1 K-1 at 20 degrees C), thereby suggesting that this entropy driven reaction also reflects conformational changes in the lectin and/or the receptor. Presence of two kinds of receptors for WBA II on erythrocytes, as observed by equilibrium studies, is consistent with the biexponential dissociation rate constants (at 20 degrees C K1 = 1.67 x 10(-3) M-1 sec-1 and K2 = 11.1 x 10(-3) M-1 sec-1). These two rate constants differed by an order of magnitude accounting for the difference in the association constants of the two receptors of WBA II. However, the association process remains monoexponential suggesting no observable difference in the association rates of the lectin molecule with both the receptors, under the experimental conditions studied. The thermodynamic parameters calculated from kinetic data correlate well with those observed by equilibrium. A two-step binding mechanism is proposed based on the kinetic parameters for WBA II-receptor interaction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Coral communities of the northwestern Gulf of Aden (Yemen): variation in framework building related to environmental factors and biotic conditions

Coral communities were investigated in the northwestern Gulf of Aden, Yemen, for their composition, structure, and bioconstruction potential. Although no true reef was encountered, high cover coral carpets were found where hard substrate was available. Seven different types of coral communities were differentiated, and both non-framework and framework coral communities were found. Monotypy or oligotypy seem to be consistent characteristics of framework-building coral communities in the study area. Apart from substrate availability, proximity to the upwelling area and exposure were found to be the most important environmental factors influencing coral communities structure, composition, and bioconstruction potential.     

Trifluoroethanol and binding to model membranes stabilize a predicted turn in a peptide corresponding to the first extracellular loop of the angiotensin II AT(1A) receptor

Deuterium oxide solutions of a triple-helical polysaccharide schizophyllan, undergoing an order-disorder transition centered around 17 degrees C, were studied by the time-domain reflectometry (TDR) to obtain dielectric dispersions in the solution and frozen states. In the solution state, the dispersion below the transition temperature is resolved in three dispersions (relaxation times at 0 degrees C) ascribed to side chain glucose residue (1; 102 ns), structured water (s; 2.0 ns) and bulk water (h), respectively, from low to high frequencies. Bulk water is divided into slow water (h2; 0.04 ns) and free or pure water (h1; 0.02 ns). Above the transition temperature structured water almost disappears and is compensated by slow water. Structured water is similar to bound water for proteins but different from it because of this transition behavior. Another dispersion (l) seen at the lowest frequency is assigned to the rotation of side-chain glucose residue coupled with hydrated water. Parts of this dispersion and structured water are suggested to constitute bound water. In the frozen state were observed a major dispersion (h; 0.14 ns) and a minor one (m; 28 ns), which were ascribed to considerably mobile and less mobile waters. They are similar to but not exactly the same as that for unfreezable water in bovine serum albumin solutions argued by Miura et al. (Biopolymers, 1995, Vol. 36, p. 9). Water is molded into different structures by the triple helix.     

Factors affecting the metal ion-hydroxamate interactions II: effect of the length of the connecting chain on the Fe(III), Mo(VI) and V(V) complexation of some new desferrioxamine B (DFB) model dihydroxamic acids

Three new dihydroxamic acids (HO(CH₃)NCO-(CH₂)₂-CO-NH-(CH₂)_x-CON(CH₃)OH where the x values are 4; 3 and 2, and the compounds are abbreviated as 2,4-DIHA, 2,3-DIHA and 2,2-DIHA), containing the peptide group in a certain position to one of the two functional groups and in different distances to the other one, were synthesized and their complexation with Fe(III), Mo(VI) and V(V) was studied by pH-potentiometric, spectrophotometric and in some cases by CV methods to evaluate the redox behaviour of the Fe(III) complexes and assess their potential biological activity as siderophore models. All these compounds are structural models for the natural siderophore, desferrioxamine B (DFB). The results were compared to those of the complexes of 2,5-DIHA having the same connecting chain structure and length as DFB has, and the effects of the length of the connecting chain on the co-ordination mode and on the stability of the complexes formed were evaluated.Very similar stability of the mono-chelated complexes formed with all these dihydroxamic acids was found. All the results obtained suggest that one dihydroxamic acid (even the 2,2-DIHA) is able to complete the four coordination sites of a MoO₂ ²⁺ core forming simple mononuclear complexes. Favoured monomeric structures of the bis-chelated complexes of these dihydroxamic acids are also suggested with V(V) having the smallest ionic radius among the three metal ions studied. In the case of iron(III), however, clear indication was obtained for the slightly different complexation behaviour of 2,2-DIHA. Namely, the formation of the mononuclear bis-chelated complex with this shortest ligand seems to have sufficient strain to induce the formation of bimetallic species such as [Fe(2,2-DIHA)₂Fe)]²⁺.     

Synthesis and X-ray characterization of nickel(II) arsenatotungstate complexes: isolation of an intermediate leading to the formation of a sandwich-type polyoxometalate

The nickel arsenatotungstate K₁₀[As₂W₁₉(H₂O){Ni(H₂O)}₂O₆₇]·18H₂O (1) has been synthesized. Due to its instability in water, attempts to obtain crystals of 1 suitable for X-ray diffraction have failed. The stabilization of the [As₂W₁₉(H₂O){Ni(H₂O)}₂O₆₇]¹⁰⁻ core has been reached by synthesizing the analogue mixed {CsK} salt. The crystal structure of Cs₆K₂[Ni(H₂O)₆][As₂W₁₉(H₂O){Ni(H₂O)}₂O₆₇]·17H₂O (2) has been resolved. It consists of two [α-AsW₉O₃₃]⁹⁻ sub-units linked via a belt containing a tungsten and two nickel cations. Comparison of infrared and electronic absorption spectroscopic data for 1 and 2 has confirmed the structure proposed for 1. The instability of 1 led us to investigate the behavior of 1 in water. UV-Vis spectroscopy revealed that the formation of this complex is a multi-step reaction. An intermediate, the complex K₈[Ni(H₂O)₆]_1.5[As₂W₁₉(H₂O){K(H₂O)}{Ni(H₂O)₄}O₆₇]·21H₂O (3), has been isolated and characterized by elemental analysis, UV-Vis and infrared spectroscopies, and X-ray diffraction. In 3, the two vacant sites of the [As₂W₁₉O₆₇]¹⁴⁻ anion are occupied by a nickel and a potassium, forming a {WNiK} belt. It follows that the stability of 2 in water is due to the large ionic radius of Cs⁺, which prevents the inclusion of the alkaline cation into the cavity of the [As₂W₁₉O₆₇]¹⁴⁻ anion. The complex 3 represents a unique example of a fully characterized intermediate leading to the formation of a sandwich-type polyoxometalate.     

Test of local adaptation to biotic interactions and soil abiotic conditions in the ant-tended <Emphasis Type="Italic">Chamaecrista fasciculata</Emphasis> (Fabaceae)

Few previous studies have assessed the role of herbivores and the third trophic level in the evolution of local adaptation in plants. The overall objectives of this study were to determine (1) whether local adaptation is present in the ant-defended plant, Chamaecrista fasciculata, and (2) the contribution of ant-plant-herbivore interactions and soil source to such adaptation. We used three C. fasciculata populations and performed both a field and a greenhouse experiment. The first involved reciprocally transplanting C. fasciculata seedlings from each population-source to each site, and subsequently applying one of three treatments to one-third of the seedlings of each population-source at each site: control, reduced ant density and reduced folivory. The greenhouse experiment involved reciprocal transplants of population-sources with soil sources to test for a soil-source effect on flower production and local adaptation to soil conditions. Field results showed that ant and herbivore treatments reduced ant density (increasing folivory) and herbivore damage relative to controls, respectively; however, these manipulations did not impact C. fasciculata reproduction or the likelihood of survival. In contrast, greenhouse results showed that soil source significantly affected flower production. Overall, plants in both experiments, regardless of population-source, always had higher reproductive output at one specific site. Native populations did not outperform nonnative ones, causing us to reject the hypothesis of local adaptation. The absence of treatment effects on plant reproduction and the likelihood of survival suggest a limited effect of ants and folivores on C. fasciculata fitness and local adaptation during the study year. Temporally inconsistent effects of biotic forces across years, coupled with the young age of populations, relative proximity of populations and possible counter effects of seed predators may reduce the likelihood of local adaptation in the populations studied.     

A new, model-free calculation method to determine the coordination modes and distribution of copper(II) among the metal binding sites of multihistidine peptides using circular dichroism spectroscopy

A new calculation method to determine microscopic protonation processes from CD spectra measured at different pH and Cu(II):ligand ratios was developed and used to give the relative binding strengths for the three histidines of hsPrP(84-114), a 31-mer polypeptide modeling the N-terminal copper(II) binding region of human (homo sapiens) prion protein. Mutants of hsPrP(84-114) with two or one histidyl residues have also been synthesized and their copper(II) complexes studied by CD spectroscopy. The 1-His models were analyzed first, and the molar CD spectra for the different coordination modes on the different histidines were calculated using the general computational program PSEQUAD. These spectra were deconvoluted into the sum of Gaussian curves and used as a first parameter set to calculate the molar spectra for the different coordination modes (3N and 4N coordination) and coordination positions (His85, His96 and His111) of the 2-His peptides. The calculation method therefore does not require the direct use of CD spectra measured in the smaller peptide models. This is a significant improvement over earlier calculation methods. In the same runs, the stepwise deprotonation pK(mic) values were refined and the pH-dependent distribution of copper(II) between the two histidines was determined. The results revealed the high, but different copper(II) binding affinities of the three separate histidines in the following order: His85 < His96His111. The calculation also showed that molar CD spectra which belong to the same coordination mode and coordination position in different ligands have very similar transition energies but different intensities. For this reason, direct transfer of molar CD spectra between different ligands may be a source of error, but the pK(mic) values and the copper(II) binding preferences are transferable from the 2-His peptides to the 3-His hsPrP(84-114).     

Metal ion-biomolecule interactions. III. Versatility of metal ion binding to imidazoles. Synthesis and 1H nmr spectroscopic properties of N- and C-bound mercury(II) complexes

Methylmercury(II) and mercury(II) complexes of imidazole (1), 1-methylimidazole (2), and the 1,3-dimethylimidazolium ion (3) have been prepared in aqueous or ethanolic solution. Elemental analysis and ¹H nmr spectroscopy have been used to characterize the complexes. The MeHg (Me = methyl) binding sites have been identified as N₁, N₃ (1), N₃, C₂ (2), and C₂ (3). Reaction with HgO leads to the formation of Hg-bridged complexes of the type Im-Hg-Im, (Im = imidazole), where bonding occurs through N₁ (1) and C₂ (3); the latter is also formed as a result of symmetrization of the C₂-bound MeHg complex. The formation of the C₂-bound (carbene) complexes is discussed in terms of the increased acidity of the C₂ proton resulting from coordination of an electrophilic species at N₃. Based on electrostatic considerations, there appears to be a “minimum degree of activation” required before C₂ bonding can occur, which explains the lack of this coordination mode in 1. ¹⁹⁹Hg-¹H spin-spin coupling (⁴J) is observed for C-bound mercury, but not for N-bound mercury, which is interpreted in terms of a decreased ligand exchange rate in the former case, due to the greater stability of the Hg-C bond. ²J coupling constants measured in (CD₃)₂SO for a number of MeHg complexes of heterocyclic ligands (including the imidazoles of the present study) correlate well with the ligand pK_a (25°C, aqueous solution), according to ²J = ?3.88 pK_a + 248.5. Results in the present work are discussed in relation to our previous work with nucleosides. The significance of the results to biological systems is considered.     

Structural changes that occur upon photolysis of the Fe(II)(a3)-CO complex in the cytochrome ba(3)-oxidase of Thermus thermophilus: a combined X-ray crystallographic and infrared spectral study demonstrates CO binding to Cu(B)

The purpose of the work was to provide a crystallographic demonstration of the venerable idea that CO photolyzed from ferrous heme-a(3) moves to the nearby cuprous ion in the cytochrome c oxidases. Crystal structures of CO-bound cytochrome ba(3)-oxidase from Thermus thermophilus, determined at ~2.8-3.2? resolution, reveal a Fe-C distance of ~2.0?, a Cu-O distance of 2.4? and a Fe-C-O angle of ~126°. Upon photodissociation at 100K, X-ray structures indicate loss of Fe(a3)-CO and appearance of Cu(B)-CO having a Cu-C distance of ~1.9? and an O-Fe distance of ~2.3?. Absolute FTIR spectra recorded from single crystals of reduced ba(3)-CO that had not been exposed to X-ray radiation, showed several peaks around 1975cm(-1); after photolysis at 100K, the absolute FTIR spectra also showed a significant peak at 2050cm(-1). Analysis of the 'light' minus 'dark' difference spectra showed four very sharp CO stretching bands at 1970cm(-1), 1977cm(-1), 1981cm(-1), and 1985cm(-1), previously assigned to the Fe(a3)-CO complex, and a significantly broader CO stretching band centered at ~2050cm(-1), previously assigned to the CO stretching frequency of Cu(B) bound CO. As expected for light propagating along the tetragonal axis of the P4(3)2(1)2 space group, the single crystal spectra exhibit negligible dichroism. Absolute FTIR spectrometry of a CO-laden ba(3) crystal, exposed to an amount of X-ray radiation required to obtain structural data sets before FTIR characterization, showed a significant signal due to photogenerated CO(2) at 2337cm(-1) and one from traces of CO at 2133cm(-1); while bands associated with CO bound to either Fe(a3) or to Cu(B) in "light" minus "dark" FTIR difference spectra shifted and broadened in response to X-ray exposure. In spite of considerable radiation damage to the crystals, both X-ray analysis at 2.8 and 3.2? and FTIR spectra support the long-held position that photolysis of Fe(a3)-CO in cytochrome c oxidases leads to significant trapping of the CO on the Cu(B) atom; Fe(a3) and Cu(B) ligation, at the resolutions reported here, are otherwise unaltered.     

Chilling and freezing stress in live oaks (Quercus section Virentes): intra- and inter-specific variation in PS II sensitivity corresponds to latitude of origin

Sensitivity to cold and freezing differs between populations within two species of live oaks (Quercus section Virentes Nixon) corresponding to the climates from which they originate. Two populations of Quercus virginiana (originating from North Carolina and north central Florida) and two populations of the sister species, Q. oleoides, (originating from Belize and Costa Rica) were grown under controlled climate regimes simulating tropical and temperate conditions. Three experiments were conducted in order to test for differentiation in cold and freezing tolerance between the two species and between the two populations within each species. In the first experiment, divergences in response to cold were tested for by examining photosystem II (PS II) photosynthetic yield (ΔF/F _m′) and non-photochemical quenching (NPQ) of plants in both growing conditions after short-term exposure to three temperatures (6, 15 and 30°C) under moderate light (400 μmol m⁻² s⁻¹). Without cold acclimation (tropical treatment), the North Carolina population showed the highest photosynthetic yield in response to chilling temperatures (6°C). Both ecotypes of both species showed maximum ΔF/F _m′ and minimum NPQ at their daytime growth temperatures (30°C and 15°C for the tropical and temperate treatments, respectively). Under the temperate treatment where plants were allowed to acclimate to cold, the Q. virginiana populations showed greater NPQ under chilling temperatures than Q. oleoides populations, suggesting enhanced mechanisms of photoprotective energy dissipation in the more temperate species. In the second and third experiments, inter- and intra-specific differentiation in response to freezing was tested for by examining dark-adapted F _v/F _m before and after overnight freezing cycles. Without cold acclimation, the extent of post-freezing declines in F _v/F _m were dependent on the minimum freezing temperature (0, −2, −5 or −10°C) for both populations in both species. The most marked declines in F _v/F _m occurred after freezing at −10°C, measured 24 h after freezing. These declines were continuous and irreversible over the time period. The North Carolina population, however, which represents the northern range limit of Q. virginiana, showed significantly less decline in F _v/F _m than the north central Florida population, which in turn showed a lower decline in Fv/F _m than the two Q. oleoides populations from Belize and Costa Rica. In contrast, after exposure to three months of chilling temperatures (temperate treatment), the two Q. virginiana populations showed no decline in F _v/F _m after freezing at −10°C, while the two Q. oleoides populations showed declines in F _v/F _m reaching 0.2 and 0.1 for Costa Rica and Belize, respectively. Under warm growth conditions, the two species showed different F ₀ dynamics directly after freezing. The two Q. oleoides populations showed an initial rise in F ₀ 30 min after freezing, followed by a subsequent decrease, while the Q. virginiana populations showed a continuous decrease in F ₀ after freezing. The North Carolina population of Q. virginiana showed a tendency toward deciduousness in response to winter temperatures, dropping 58% of its leaves over the three month winter period compared to only 6% in the tropical treatment. In contrast, the Florida population dropped 38% of its leaves during winter. The two populations of the tropical Q. oleoides showed no change in leaf drop during the 3-months winter (10% and 12%) relative to their leaf drop over the same timecourse in the tropical treatment. These results indicate important ecotypic differences in sensitivity to freezing and cold stress between the two populations of Q. virginiana as well as between the two species, corresponding to their climates of origin.     

田间二化螟雄蛾对不同配比性信息素的嗅觉反应 及性信息素识别相关基因表达水平差异

【目的】本研究旨在从行为和嗅觉分子水平探究二化螟Chilo suppressalis雄蛾对性信息素嗅觉反应的地理种群差异及其机理,以明确该害虫田间种群雄成虫的嗅觉适应性及其特点。【方法】采用7种Z11-16∶Ald, Z9-16∶Ald和Z13-18∶Ald配比不同的三元性信息素诱芯(Z11-16∶Ald和Z9-16∶Ald配比分别为540 μg∶540 μg, 864 μg∶216 μg, 945 μg∶135 μg, 980 μg∶98 μg, 1 003 μg∶77 μg, 1 016 μg∶64 μg和1 045 μg∶35 μg,而Z13-18∶Ald含量保持不变),在中国6省水稻田间诱捕二化螟雄成虫;利用实验室风洞测定864 μg∶216 μg, 980 μg∶98 μg和1 016 μg∶64 μg配比诱芯在田间诱捕的越冬代和第2代二化螟雄蛾分别对这3个配比的性信息素诱芯的行为反应;并采用RT-qPCR方法测定这7种性信息素配比不同的诱芯诱捕的雄蛾触角中二化螟雄蛾12个性信息素识别相关基因的表达水平。【结果】在田间试验中,Z11-16∶Ald和Z9-16∶Ald不同配比的性信息素诱芯对水稻二化螟雄蛾均有引诱作用,但不同配比引诱的二化螟雄蛾占比不同。6省诱芯中Z11-16∶Ald和Z9-16∶Ald的最佳配比不同,并且同一配比性信息素诱芯在不同省份引诱的二化螟雄蛾占比也不同。结果表明,不仅在不同地区诱芯的性信息素最佳配比不同,而且在不同地区不同配比性信息素的诱蛾量占比也不同。实验室风洞试验中,864 μg∶216 μg和1 016 μg∶64 μg配比诱芯田间诱捕雄蛾分别对864 μg∶216 μg和1 016 μg∶64 μg配比诱芯的行为反应均显著强于对其余两种配比诱芯,980 μg∶98 μg配比诱芯田间诱捕雄蛾对1 016 μg∶64 μg, 980 μg∶98 μg和864 μg∶216 μg配比诱芯的行为反应无显著差异。在RT-qPCR测定中,除GOBP1外,其余11个性信息素识别相关基因在Z11-16∶Ald和Z9-16∶Ald不同配比诱芯诱捕雄蛾触角中的表达水平均存在显著差异,其中PBP3, PBP4, PR1, PR2, PR4, PR5和PR6 7个基因的表达水平与性信息素配比之间存在显著的线性相关。【结论】本研究明确了中国二化螟不同地理种群性信息素嗅觉差异,不仅有助于提高该害虫的性诱防控效率,而且也有助于理解其嗅觉地理种群差异的成因。     

Heavy metal-nucleotide interactions. III. The participation of amino groups in the binding of methylmercury (II) to cytidine and adenosine 5'-phosphate in aqueous solution: studies by Raman difference spectrophotometry.

Raman difference spectrophotometry has been used to study the interaction of CH3Hg(II) with cytidine and Ado-5'-P at high pH. In contrast to the binding reactions which occur at lower pH or in non-aqueous solvents such as dimethyl sulfoxide, a proton is transferred from the amino group; and the complexes are CH3HgCydH-1 and CH3HgAdoH-1-5'-P. The spectra are significantly different from those of the cationic complexes. The integrated intensities of ligand modes which shift upon metalation can be used to measure the concentration of unreacted ligand and consequently the extent of the reaction. Equilibrium constants for the reactions CH3HgOH + L yields CH3HgLH-1 + H2O were estimated to be log KCyd equals 0.63 plus or minus 0.05 and log KAdo-5'-P equals 0.85 plus or minus 0.05, in fair agreement with values determined under very different conditions by ultraviolet spectrophotometry. The vibrational spectrum of the ligand in CH3HgCydH-1 is virtually the same as that of UrdH-1- which is isoelectronic. The spectrum of the ligand in CH3HgAdoH-1-5'-P is more similar to the isoelectronic base InoH-1-than to Ado-5'-P, although the resemblance is not so close as in the CydH-1---UrdH-1-case. The structures of these complexes are discussed on the basis of their vibrational spectra and similarities in the spectra of related compounds. It is concluded that the CH3Hg(II) binds to the amino nitrogen at high pH with both cytidine and Ado-5'-P. In neutral solution with excess CH3Hg(II), metalation occurs on the amino groups, on the ring, and also on the ribose.     

Nickel(II) binding to glycylglycyl-L-tyrosine-N-methyl amide, a peptide mimicking the NH2-terminal nickel(II)-binding site of dog serum albumin: a 1H- and 13C-nuclear magnetic resonance investigation

The nonspecificity of dog serum albumin (DSA) for Ni(II) is mimicked by the simplest tripeptide, glycylglycyl-L-tyrosine-N-methyl amide, which forms a planar complex at high pH. In this study, the 1H and 13C nuclear magnetic resonance (nmr) spectra of the free and complexed peptide are reported. As the pH is increased for the free peptide, the deprotonation of the terminal amino group (pKa = 7.94) is reflected most strongly by the chemical shift changes of the NH2-terminal -CH2CO- unit. Large upfield and downfield shifts for the tyrosine C xi, C epsilon and C gamma carbon resonances occur on the ionization of the phenolic hydroxyl group. The planar Ni(II) complex is in slow exchange on the nmr time scale and is of 1:1 stoichiometry. The greater chemical shift changes on Ni(II) coordination are observed from the protons nearest the peptide and amino nitrogens:amide CH3 (-0.704), Tyr(3) alpha-CH (-0.667), Gly(1) alpha-CH2 (-0.382), and Gly(2) alpha-CH2 (-0.519, -0.487). In the 13C spectrum, the Gly(1) C alpha (+7.58) is most affected. The Ni(II) ion is therefore at the center of four coordinating nitrogens. Changes in the coupling constants for the Tyr(3) -CH-CH2- moiety suggests a mainly gauche conformation with the tyrosyl ring positioned above the plane of coordination and a weak bonding interaction with the Ni(II) ion is indicated. These results provide structural information regarding the reduced affinity of DSA for Ni(II).     

Studies of copper(II) binding to glycylglycyl-L-tyrosine-N-methyl amide, a peptide mimicking the NH2-terminal copper(II)-binding site of dog serum albumin by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy

Unlike human serum albumin (HSA), dog serum albumin (DSA) does not possess the characteristics of the specific first binding site for Cu(II). In DSA, the important histidine residue in the third position, responsible for the Cu(II)-binding specificity in HSA, is replaced by a tyrosine residue. In order to study the influence of the tyrosine residue in the third position of DSA, a simple model of the NH2-terminal native sequence tripeptide of DSA, glycylglycyl-L-tyrosine-N-methylamide (GGTNMA) was synthesized and its Cu(II)-binding properties studied by analytical potentiometry, spectrophotometry, CD, and NMR spectroscopy. The species analysis indicated the existence of five mono-complexes at different protonation states: MHA, MA, MH-1A, MH-2A, MH-3A, and only one bis-complex MH-2A-2. The complexing ability of GGTNMA to Cu(II) was found to be weaker than that of the Cu(II) binding peptide models of HSA. The visible absorption spectra of Cu(II)-GGTNMA complexes are similar to those observed in the case of DSA-Cu(II) complexes. The weaker binding and the spectral properties of Cu(II)-GGTNMA complexes are consistent with less specific Cu(II)-binding properties of the peptide of this sequence similar to what was noted with DSA. CD results are in excellent agreement with species analysis and visible spectra where it is clearly evident that Cu(II) binds to GGTNMA starting from the alpha-NH2 group and step by step to deprotonated amide nitrogens as the pH is raised. The absence of any charge transfer band around 400 nm strongly indicates that Cu(II) does not bind to the phenolate group. Furthermore, NMR results are consistent with the noninvolvement of the tyrosine residue of GGTNMA in Cu(II) complexation. Thus, it is clear that the low Cu(II)-binding affinity of DSA is due to the genetic substitution of tyrosine for histidine at the NH2-terminal region of the protein.