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31.
Colin A Malcolm Badria El Sayed Ahmed Babiker Romain Girod Didier Fontenille Bart GJ Knols Abdel Hameed Nugud Mark Q Benedict 《Malaria journal》2009,8(Z2):S9
The selection of suitable field sites for integrated control of Anopheles mosquitoes using the sterile insect technique (SIT) requires consideration of the full gamut of factors facing most proposed control strategies, but four criteria identify an ideal site: 1) a single malaria vector, 2) an unstructured, relatively low density target population, 3) isolation of the target population and 4) actual or potential malaria incidence. Such a site can exist in a diverse range of situations or can be created. Two contrasting SIT field sites are examined here: the desert-flanked Dongola Reach of the Nile River in Northern State, Sudan, where malaria is endemic, and the island of La Reunion, where autochthonous malaria is rare but risk is persistent. The single malaria-transmitting vector at both sites is Anopheles arabiensis. In Sudan, the target area is a narrow 500 km corridor stretching from the rocky terrain at the Fourth Cataract - just above the new Merowe Dam, to the northernmost edge of the species range, close to Egypt. Vector distribution and temporal changes in density depend on the Nile level, ambient temperature and human activities. On La Reunion, the An. arabiensis population is coastal, limited and divided into three areas by altitude and exposure to the trade winds on the east coast. Mosquito vectors for other diseases are an issue at both sites, but of primary importance on La Reunion due to the recent chikungunya epidemic. The similarities and differences between these two sites in terms of suitability are discussed in the context of area-wide integrated vector management incorporating the SIT. 相似文献
32.
Badria B El Sayed Colin A Malcolm Ahmed Babiker Elfatih M Malik Mohammed AH El Tayeb Nageeb S Saeed Abdel Hameed D Nugud Bart GJ Knols 《Malaria journal》2009,8(Z2):S3
The global malaria situation, especially in Africa, and the problems frequently encountered in chemical control of vectors such as insecticide resistance, emphasize the urgency of research, development and implementation of new vector control technologies that are applicable at regional and local levels. The successful application of the sterile insect technique (SIT) for the control of the New World screwworm Cochliomyia hominivorax and several species of fruit flies has given impetus to the use of this method for suppression or elimination of malaria vectors in some areas of Africa including Northern State of Sudan. The research and development phase of the Northern State feasibility study has been started. Sudanese stakeholders are working side-by-side with the International Atomic Energy Agency in the activities of this important phase. Several ethical, legal and social issues associated with this approach arose during this phase of the project. They need to be seriously considered and handled with care. In this paper, these issues are described, and the current and proposed activities to overcome potential hurdles to ensure success of the project are listed. 相似文献
33.
Background
Many studies have suggested that variability in the attractiveness of humans to host-seeking mosquitoes is caused by differences in the make-up of body emanations, and olfactory signals in particular. Most investigations have either been laboratory-based, utilising odour obtained from sections of the body, or have been done in the field with sampling methods that do not discriminate between visual, physical and chemical cues of the host. Accordingly, evidence for differential attractiveness based on body emanations remains sparse in spite of the far-reaching epidemiological implications of this phenomenon. 相似文献34.
Flow birefringence and extinction angles have been measured for HMG 14 complexes with nucleosome core particles from chicken erythrocytes under cooperative "tight" binding conditions, and for the uncomplexed core particles used in the preparations. Results are interpreted using optical models for the observed DNA anisotropy, and are compared to recent small angle neutron scattering results. (19) The studies effectively rule out highly distorted DNA conformations and configurations in which DNA ends are unwound and extended. It is concluded that the most likely conformation of the complex is one in which the DNA superhelix is radially increased, either uniformly or bilaterally, with the DNA ends remaining tightly bound to the particle. This conformation does not require large changes in spatial relationships between the DNA ends compared to the uncomplexed core as would accompany, for example, significant unwinding of the ends. However, it may lead to more subtle but possibly highly significant differences in the angles at which the DNA exits the core particle. 相似文献
35.
36.
X-ray structure of the nucleosome core particle 总被引:2,自引:0,他引:2
Two monoclinic crystal forms (P2(1),C2) of chicken erythrocyte nucleosomes have been under study in this laboratory. The x-ray structure of the P2(1) crystal form has been solved to 15 A resolution. The B-DNA superhelix has a relatively uniform curvature, with only several local distortions observed in the superhelix. The individual histone domains have been localized and specific contacts between each histone and the DNA can be observed. Histone contacts to the inner surface of the DNA superhelix occur predominantly at the minor groove sites. Most of the histone core is contained within the inner surface of the superhelical DNA, except for part of H2A which extends between the DNA gyres near the terminus of the DNA. No part of H2A blocks the DNA terminus or would prevent a smooth exit of the DNA into the linker region. A similar extension of a portion of histone H4 between the DNA gyres occurs close to the dyad axis. Both unique nucleosomes in the P2(1) asymmetric unit demonstrate good dyad symmetry and are similar to each other throughout the histone core and DNA regions. 相似文献
37.
Young GW Hoofring SA Mamula MJ Doyle HA Bunick GJ Hu Y Aswad DW 《The Journal of biological chemistry》2005,280(28):26094-26098
Protein L-isoaspartyl methyltransferase (PIMT) has been implicated in the repair or metabolism of proteins containing atypical L-isoaspartyl peptide bonds. The repair hypothesis is supported by previous studies demonstrating in vitro repair of isoaspartyl peptides via formation of a succinimide intermediate. Utilization of this mechanism in vivo predicts that PIMT modification sites should exhibit significant racemization as a side reaction to the main repair pathway. We therefore studied the D/L ratio of aspartic acid at specific sites in histone H2B, a known target of PIMT in vivo. Using H2B from canine brain, we found that Asp25 (the major PIMT target site in H2B) was significantly racemized, exhibiting d/l ratios as high as 0.12, whereas Asp51, a comparison site, exhibited negligible racemization (D/L < or = 0.01). Racemization of Asp25 was independent of animal age over the range of 2-15 years. Using H2B from 2-3-week mouse brain, we found a similar D/L ratio (0.14) at Asp25 in wild type mice, but substantially less racemization (D/L = 0.035) at Asp25 in PIMT-deficient mice. These findings suggest that PIMT functions in the repair, rather than the metabolic turnover, of isoaspartyl proteins in vivo. Because PIMT has numerous substrates in cells, these findings also suggest that D-aspartate may be more common in cellular proteins than hitherto imagined and that its occurrence, in some proteins at least, is independent of animal age. 相似文献
38.
Structure of the nucleosome core particle at 8 A resolution 总被引:1,自引:0,他引:1
The x-ray crystallographic structure of the nucleosome core particle has been determined using 8 A resolution diffraction data. The particle has a mean diameter of 106 A and a maximum thickness of 65 A in the superhelical axis direction. The longest chord through the histone core measures 85 A and is in a non-axial direction. The 1.87 turn superhelix consists of B-DNA with about 78 base pairs or 7.6 helical repeats per superhelical turn. The mean DNA helical repeat contains 10.2 +/- 0.05 base pairs and spans 35 A, slightly more than standard B-DNA. The superhelix varies several Angstroms in radius and pitch, and has three distinct domains of curvature (with radii of curvature of 60, 45 and 51 A). These regions are separated by localized sharper bends +/- 10 and +/- 40 base pairs from the center of the particle, resulting in an overall radius of curvature about 43 A. Compression of superhelical DNA grooves on the inner surface and expansion on the outer surface can be seen throughout the DNA electron density. This density has been fit with a double helical ribbon model providing groove width estimates of 12 +/- 1 A inside vs. 19 +/- 1 A outside for the major groove, and 8 +/- 1 A inside vs. 13 +/- 1 A outside for the minor groove. The histone core is primarily contained within the bounds defined by the superhelical DNA, contacting the DNA where the phosphate backbone faces in toward the core. Possible extensions of density between the gyres have been located, but these are below the significance level of the electron density map. In cross-section, a tripartite organization of the histone octamer is apparent, with the tetramer occupying the central region and the dimers at the extremes. Several extensions of histone density are present which form contacts between nucleosomes in the crystal, perhaps representing flexible or "tail" histone regions. The radius of gyration of the histone portion of the electron density is calculated to be 30.4 A (in reasonable agreement with solution scattering values), and the histone core volume in the map is 93% of its theoretical volume. 相似文献
39.
D E Timm H A Mueller P Bhanumoorthy J M Harp G J Bunick 《Structure (London, England : 1993)》1999,7(9):1023-1033
BACKGROUND: Fumarylacetoacetate hydrolase (FAH) catalyzes the final step of tyrosine and phenylalanine catabolism, the hydrolytic cleavage of a carbon-carbon bond in fumarylacetoacetate, to yield fumarate and acetoacetate. FAH has no known sequence homologs and functions by an unknown mechanism. Carbon-carbon hydrolysis reactions are essential for the human metabolism of aromatic amino acids. FAH deficiency causes the fatal metabolic disease hereditary tyrosinemia type I. Carbon-carbon bond hydrolysis is also important in the microbial metabolism of aromatic compounds as part of the global carbon cycle. RESULTS: The FAH crystal structure has been determined by rapid, automated analysis of multiwavelength anomalous diffraction data. The FAH polypeptide folds into a 120-residue N-terminal domain and a 300-residue C-terminal domain. The C-terminal domain defines an unusual beta-strand topology and a novel 'mixed beta-sandwich roll' structure. The structure of FAH complexed with its physiological products was also determined. This structure reveals fumarate binding near the entrance to the active site and acetoacetate binding to an octahedrally coordinated calcium ion located in close proximity to a Glu-His dyad. CONCLUSIONS: FAH represents the first structure of a hydrolase that acts specifically on carbon-carbon bonds. FAH also defines a new class of metalloenzymes characterized by a unique alpha/beta fold. A mechanism involving a Glu-His-water catalytic triad is suggested based on structural observations, sequence conservation and mutational analysis. The histidine imidazole group is proposed to function as a general base. The Ca(2+) is proposed to function in binding substrate, activating the nucleophile and stabilizing a carbanion leaving group. An oxyanion hole formed from sidechains is proposed to stabilize a tetrahedral alkoxide transition state. The proton transferred to the carbanion leaving group is proposed to originate from a lysine sidechain. The results also reveal the molecular basis for mutations causing the hereditary tyrosinemia type 1. 相似文献
40.
Virginie Lopez Rascol Anthony Levasseur Olivier Chabrol Simona Grusea Philippe Gouret Etienne GJ Danchin Pierre Pontarotti 《BMC bioinformatics》2009,10(1):284