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1.
Marjorie A. Hoy J. J. Rob Groot Hugo E. van de Baan 《Entomologia Experimentalis et Applicata》1985,37(1):17-31
Aerial dispersal of the phytoseiid Metaseiulus occidentalis (Nesbitt) was evaluated as a component in managing pesticide-resistant populations established in California almond orchards. Peak dispersal occurred in late July and early August during 1982 and 1983. Most predators (and spider mites) left the orchards on the prevailing winds from the northwest. Within the orchard, the prevailing winds had less influence, and dispersal was usually random. Both spider mites and predators dispersed randomly with regard to height from the almond trees, but data obtained during one 24-h interval suggest they do not disperse randomly throughout the day. Most aerial movements occurred between 16–22 h when relative humidity and wind speeds increased and temperatures decreased. Spider mites and predators were trapped on panels located 200 m from the orchard. A survey of carbaryl resistance levels in M. occidentalis collected from almond orchards surrounding the release sites indicates that carbaryl-resistant M. occidentalis dispersed at least 800 m between 1981–83. However, growers wishing to use the resistant strains should release them in their orchards as natural dispersal appears to be too slow. Migration of native M. occidentalis into the release sites appeared to be sufficiently rare that dilution of carbaryl-resistant populations was minimal during a 2–4 year period.
Résumé La dispersion aérienne du phytoseïdae, M. occidentalis (Nesbitt), a été estimée comme élément de la lutte contre les populations résistantes aux insecticides établies dans les vergers de Californie. La dispersion maximale s'est produite fin juillet et début a oût en 1982 et 1983. La plupart des prédateurs (et des acariens) quittent les vergers avec les vents dominants du nordouest. Dans le verger, les vents dominants sont moins importants et la dispersion est généralement au hasard. Tant les acariens que les prédateurs se dispersaient au hasard par rapport à la taille des amandiers, mais les relevés sur 24 heures laissent supposer qu'il n'y a pas une distribution aléatoire pendant la journée. La plupart des mouvements aériens se produisirent entre 16 et 22 heures quand HR et vitesse du vent augmentaient et température diminuait. Les acariens et prédateurs ont été piégés sur des panneaux à 200 m du verger.相似文献
2.
Burak Erman 《Proteins》2013,81(7):1097-1101
Fluctuations of the distance between a pair of residues i and j may be correlated with the fluctuations of the distance between another pair k and l. In this case, information may be transmitted among these four residues. Allosteric activity is postulated to proceed through such correlated paths. In this short communication a fast method for calculating correlations among all possible pairs ij and kl leading to a pathway of correlated residues of a protein is proposed. The method is based on the alpha carbon centered Gaussian Network Model. The model is applied to Glutamine Amidotransferase and pathways of allosteric activity are identified and compared with literature. Proteins 2013; 81:1097–1101. © 2013 Wiley Periodicals, Inc. 相似文献
3.
Jianbo Zhang Qiuguo Fu Haiyan Wang Juying Li Wei Wang Zhen Yang Sufen Zhang Qingfu Ye Chao Li Zhong Li 《Chirality》2013,25(11):686-691
For a novel potential commercial chiral pesticide, an independent study on the fate characteristics and residues of each stereoisomer is essential if the application rates for the pesticide and human exposure are to be reduced. The absorption and translocation behavior of a chiral insecticide, cycloxaprid, in plants treated by root immersion and blade smearing was studied using 14C‐labeling tracer techniques. With the root treatment, total absorption of (1R;8S)‐cycloxaprid (RS) (12.39%) was much greater than that of (1S;8R)‐cycloxaprid (SR) (3.31%) at 192 h after treatment (HAT). The mass concentrations ( RS / SR ) of cycloxaprid in the roots, cotyledons, leaf 1, leaf 2, and leaf 3 were 37.0/16.8, 8.3/2.8, 11.7/6.5, 5.1/4.8, and 8.0/4.7 mg kg‐1 (fresh weight), respectively, at 192 HAT at an initial concentration 1.6 mg kg‐1. With the foliar application treatment, no significant difference was observed between the total absorption of RS (3.11%) and SR (4.03%) at the end of the treatment. Both acropetal and basipetal transport of absorbed 14C occurred and more than 71.83% of absorbed RS and 82.42% of SR remained in the treated leaf. Stereoselective absorption was observed during root uptake but not during foliar absorption. Chirality 25:686–691, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
4.
Single chain fragment variables (ScFvs) have been extensively employed in studying the protein-protein interactions. ScFvs derived from phage display libraries have an additional advantage of being generated against a native antigen, circumventing loss of information on conformational epitopes. In the present study, an attempt has been made to elucidate human chorionic gonadotropin (hCG)-luteinizing hormone (LH) receptor interactions by using a neutral and two inhibitory ScFvs against hCG. The objective was to dock a computationally derived model of these ScFvs onto the crystal structure of hCG and understand the differential roles of the mapped epitopes in hCG-LH receptor interactions. An anti-hCG ScFv, whose epitope was mapped previously using biochemical tools, served as the positive control for assessing the quality of docking analysis. To evaluate the role of specific side chains at the hCG-ScFv interface, binding free energy as well as residue interaction energies of complexes in solution were calculated using molecular mechanics Poisson-Boltzmann/surface area method after performing the molecular dynamic simulations on the selected hCG-ScFv models and validated using biochemical and SPR analysis. The robustness of these calculations was demonstrated by comparing the theoretically determined binding energies with the experimentally obtained kinetic parameters for hCG-ScFv complexes. Superimposition of hCG-ScFv model onto a model of hCG complexed with the 51-266 residues of LH receptor revealed importance of the residues previously thought to be unimportant for hormone binding and response. This analysis provides an alternate tool for understanding the structure-function analysis of ligand-receptor interactions. 相似文献
5.
农药的轭合与结合态残留 总被引：2，自引：0，他引：2
随着科技水平的不断提高,人们对农药残留影响生态环境的认识不断在更新和完善。农药的轭合与结合残留是在标记农药的出现和高精度分析仪器和技术得到应用后被发现和认识的。国外在这方面的研究开展得较早,工作也较 相似文献
6.
Conformational studies of the peptides constructed from achiral amino acid residues Aib and Delta(Z)Phe (I) Ac-Aib-Delta(Z)Phe-NHMe (II), and Ac-(Aib-Delta(Z)Phe)(3)-NHMe; peptides III-VI having L-Leu or D-Leu at either the N- or the C-terminal position and of peptides VII-X having Leu residues in different enantiomeric combinations at both the N- and the C-terminal positions in peptide II have been studied to design the peptide with the required helical sense. Peptide II, as expected, adopts degenerate left- and right-handed helical structures. It has been shown that the peptides IV and VI having D-Leu at either the N or the C terminus can be realized in the right-handed helical structure with the phi,psi values of -20 degrees and -60 degrees for the Aib/Delta(Z)Phe residues. L-Leu and D- Leu at both the terminals in peptides VII and VIII, respectively, have hardly any effect as both the left- and the right-handed structures are found to be degenerate. Peptides III and IX can be realized in right- and left-handed helical structures, respectively, in solvents of low polarity whereas peptides V and X are predicted to be in the right-handed helical structures stabilized by carbonyl-carbonyl interactions without the formation of hydrogen bonds. The conformational states with the phi,psi values of 0 degrees and -85 degrees in peptide V are characterized by rise per residue of 2.03 A, rotation per residue of 117.5 degrees , and 3.06 residues per turn. In all peptides having Leu residue at the N terminus, the methyl moiety of the acetyl group is involved in the CH/pi interactions with the Cepsilon--Cdelta edge of the aromatic ring of Delta(Z)Phe (3) and the amino group NH of Delta(Z)Phe is involved in the NH/pi interactions with its own aromatic ring. The CH(3) groups of the Aib residues are also involved in CH/pi interactions with the i + 1th and i + 3th Delta(Z)Phe's aromatic side chains. 相似文献
7.
Long YQ Guo R Luo JH Yang D Roller PP 《Biochemical and biophysical research communications》2003,310(2):334-340
Without the presence of a phosphotyrosyl group, a phage library derived non-phosphorylated cyclic peptide ligand of Grb2-SH2 domain attributed its high affinity and specificity to well-defined and highly favored interactions of its structural elements with the binding pocket of the protein. We have disclosed a significant compensatory role of the Glu(2-) sidechain for the absence of the phosphate functionality on Tyr(0) in the peptide ligand, cyclo(CH(2)CO-Glu(2-)-Leu-Tyr(0)-Glu-Asn-Val-Gly-Met(5+)-Tyr-Cys)-amide (termed G1TE). In this study, we report the importance of hydrophobic residue at the Tyr+5 site in G1TE. Both acidic and basic amino acid substitutes are disfavored at this position, and replacement of Met with beta-tert-butyl-Ala was found to improve the antagonist properties. Besides, the polarity of the cyclization linkage was implicated as important in stabilizing the favored binding conformation. Oxidation of the thioether linkage into sulfoxide facilitated the binding to Grb2-SH2 markedly. Simultaneous modification of the three distant sites within G1TE provided the best agent with an IC(50) of 220 nM, which is among the most potent non-phosphorous- and non-phosphotyrosine-mimic containing Grb2-SH2 domain inhibitors yet reported. This potent peptidomimetic provides a novel template for the development of chemotherapeutic agents for the treatment of erbB2-related cancer. Biological assays on G1TE(Gla(2-)) in which the original residue of Glu(2-) was substituted by gamma-carboxyglutamic acid (Gla) indicated that it could inhibit the interaction between activated GF receptor and Grb2 protein in cell homogenates of MDA-MB-453 breast cancer cells at the 2 microM level. More significantly, both G1TE(Gla(2-)) alone and the conjugate of G1TE(Gla(2-)) with a peptide carrier can effectively inhibit intracellular association of erbB2 and Grb2 in the same cell lines with IC(50) of 50 and 2 microM, respectively. 相似文献
8.
Short range side chain‐backbone hydrogen bonded motifs involving Asn and Gln residues have been identified from a data set of 1370 protein crystal structures (resolution ≤ 1.5 Å). Hydrogen bonds involving residues i ? 5 to i + 5 have been considered. Out of 12,901 Asn residues, 3403 residues (26.4%) participate in such interactions, while out of 10,934 Gln residues, 1780 Gln residues (16.3%) are involved in these motifs. Hydrogen bonded ring sizes (Cn, where n is the number of atoms involved), directionality and internal torsion angles are used to classify motifs. The occurrence of the various motifs in the contexts of protein structure is illustrated. Distinct differences are established between the nature of motifs formed by Asn and Gln residues. For Asn, the most highly populated motifs are the C10 (COδi …NHi + 2), C13 (COδi …NHi + 3) and C17 (NδHi …COi ? 4) structures. In contrast, Gln predominantly forms C16 (COεi …NHi ? 3), C12 (NεHi …COi ? 2), C15 (NεHi …COi ? 3) and C18 (NεHi …COi ? 4) motifs, with only the C18motif being analogous to the Asn C17structure. Specific conformational types are established for the Asn containing motifs, which mimic backbone β‐turns and α‐turns. Histidine residues are shown to serve as a mimic for Asn residues in side chain‐backbone hydrogen bonded ring motifs. Illustrative examples from protein structures are considered. Proteins 2012; © 2011 Wiley Periodicals, Inc. 相似文献
9.
Computational protein structure prediction remains a challenging task in protein bioinformatics. In the recent years, the importance of template-based structure prediction is increasing because of the growing number of protein structures solved by the structural genomics projects. To capitalize the significant efforts and investments paid on the structural genomics projects, it is urgent to establish effective ways to use the solved structures as templates by developing methods for exploiting remotely related proteins that cannot be simply identified by homology. In this work, we examine the effect of using suboptimal alignments in template-based protein structure prediction. We showed that suboptimal alignments are often more accurate than the optimal one, and such accurate suboptimal alignments can occur even at a very low rank of the alignment score. Suboptimal alignments contain a significant number of correct amino acid residue contacts. Moreover, suboptimal alignments can improve template-based models when used as input to Modeller. Finally, we use suboptimal alignments for handling a contact potential in a probabilistic way in a threading program, SUPRB. The probabilistic contacts strategy outperforms the partly thawed approach, which only uses the optimal alignment in defining residue contacts, and also the re-ranking strategy, which uses the contact potential in re-ranking alignments. The comparison with existing methods in the template-recognition test shows that SUPRB is very competitive and outperforms existing methods. 相似文献
10.
Transmembrane beta-barrel (TMB) proteins are embedded in the outer membrane of Gram-negative bacteria, mitochondria, and chloroplasts. The cellular location and functional diversity of beta-barrel outer membrane proteins (omps) makes them an important protein class. At the present time, very few nonhomologous TMB structures have been determined by X-ray diffraction because of the experimental difficulty encountered in crystallizing transmembrane proteins. A novel method using pairwise interstrand residue statistical potentials derived from globular (nonouter membrane) proteins is introduced to predict the supersecondary structure of transmembrane beta-barrel proteins. The algorithm transFold employs a generalized hidden Markov model (i.e., multitape S-attribute grammar) to describe potential beta-barrel supersecondary structures and then computes by dynamic programming the minimum free energy beta-barrel structure. Hence, the approach can be viewed as a \"wrapping\" component that may capture folding processes with an initiation stage followed by progressive interaction of the sequence with the already-formed motifs. This approach differs significantly from others, which use traditional machine learning to solve this problem, because it does not require a training phase on known TMB structures and is the first to explicitly capture and predict long-range interactions. TransFold outperforms previous programs for predicting TMBs on smaller (相似文献