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991.
DNA barcoding, as a tool for species discrimination, has been used efficiently in animals, algae and fungi, but there are still debates on which DNA region(s) can be used as the standard barcode(s) for land plants. Gymnosperms, especially conifers, are important components of forests, and there is an urgent need for them to be identified through DNA barcoding because of their high frequency of collection in the field. However, the feasibility of DNA barcoding in gymnosperms has not been examined based on a dense species sampling. Here we selected seven candidate DNA barcodes from the plastome (matK, rbcL, rpoB, rpoC1, atpF-atpH, psbA-trnH, and psbK-psbI) to evaluate their suitability in Picea (spruce). The results showed that none of them or their different combinations has sufficient resolution for spruce species, although matK+rbcL might be used as a two-locus barcode. The low efficiency of these candidate barcodes in Picea might be caused by the paternal inheritance of the chloroplast genome, long generation time, recent radiation, and frequent inter-specific hybridization aided by wind pollination. Some of these factors could also be responsible for the difficulties in barcoding other plant groups. Furthermore, the potential of the nuclear LEAFY gene as a land plant barcode was discussed. 相似文献
992.
Hui Wang Sakesit Chumnarnsilpa Anantasak Loonchanta Qiang Li Yang-Mei Kuan Sylvie Robine M?rten Larsson Ivana Mihalek Leslie D. Burtnick Robert C. Robinson 《The Journal of biological chemistry》2009,284(32):21265-21269
Villin and gelsolin consist of six homologous domains of the gelsolin/cofilin fold (V1–V6 and G1–G6, respectively). Villin differs from gelsolin in possessing at its C terminus an unrelated seventh domain, the villin headpiece. Here, we present the crystal structure of villin domain V6 in an environment in which intact villin would be inactive, in the absence of bound Ca2+ or phosphorylation. The structure of V6 more closely resembles that of the activated form of G6, which contains one bound Ca2+, rather than that of the calcium ion-free form of G6 within intact inactive gelsolin. Strikingly apparent is that the long helix in V6 is straight, as found in the activated form of G6, as opposed to the kinked version in inactive gelsolin. Molecular dynamics calculations suggest that the preferable conformation for this helix in the isolated G6 domain is also straight in the absence of Ca2+ and other gelsolin domains. However, the G6 helix bends in intact calcium ion-free gelsolin to allow interaction with G2 and G4. We suggest that a similar situation exists in villin. Within the intact protein, a bent V6 helix, when triggered by Ca2+, straightens and helps push apart adjacent domains to expose actin-binding sites within the protein. The sixth domain in this superfamily of proteins serves as a keystone that locks together a compact ensemble of domains in an inactive state. Perturbing the keystone initiates reorganization of the structure to reveal previously buried actin-binding sites.Actin is crucial to such processes as cell movement, cell division, and apoptosis, which are regulated by numerous actin-binding proteins, including gelsolin, Arp2/3, and profilin (for review, see Ref. 1). Gelsolin, the most potent actin filament-severing protein known, can bind to, sever, cap, and nucleate actin filaments in a calcium-, pH-, ATP-, and phospholipid-dependent manner (for review, see Ref. 2). Villin, found in microvilli of absorptive epithelium, is a second member of the gelsolin family of actin-binding proteins. In addition to standard gelsolin-type activities, villin is able to bundle actin filaments and is subject to regulation by tyrosine phosphorylation as well as by Ca2+ and phosphatidylinositol 4,5-bisphosphate (for review, see Ref. 3). Many comparisons have been made between gelsolin and villin. The two share 50% amino acid sequence identity and show similar proteolytic cleavage patterns (4). Both contain six similarly folded domains, but villin possesses a seventh domain at its C terminus, the headpiece (HP)2 domain, which folds into a compact structure that introduces a second F-actin-binding site into the protein. Recent studies indicate that villin uses the HP F-actin-binding sites to achieve bundling (5). In an environment devoid of free Ca2+, gelsolin and villin assume inactive conformations. After binding Ca2+, both undergo conformational rearrangements that expose their binding sites for F-actin. In villin, this includes revealing the HP actin-binding site through a “hinge mechanism” (6).Biochemical and structural studies have revealed eight Ca2+-binding sites of two types in gelsolin (for review, see Ref. 7). Each of the six domains contains a complete and evolutionarily conserved site, termed type 2, whereas G1 and G4 provide partial Ca2+ coordination at interfaces with actin through sites termed type 1. Sequential mutagenesis of these sites in villin has identified six functional Ca2+-binding sites (8): two major sites, one each of type 1 and type 2, in V1, plus four type 2 sites in V2–V6. The type 1 site in V1 regulates F-actin-capping and F-actin-severing activities, whereas the lower affinity type 2 site in V1 only affects severing (9). The other four sites are involved in stabilizing villin conformation, but they do not directly influence actin-severing activity. NMR studies of a fragment of villin that consists of V6 and the HP domain have implicated V6 residues Asn647, Asp648, and Glu670 in binding Ca2+ (10). These experiments also revealed the first 80 residues of V6 to undergo significant conformational change as a result of Ca2+ binding.Nanomolar to micromolar concentrations of free Ca2+ govern the actin-binding activities of gelsolin. In contrast, micromolar and millimolar concentrations of calcium ions are required for villin to exhibit capping and severing, respectively. However, after tyrosine phosphorylation, villin can sever actin filaments even at nanomolar Ca2+ concentrations (11). Furthermore, although the actin-severing ability of the N-terminal half of villin is calcium-dependent, that by the N-terminal half of gelsolin is not. In contrast, the binding of G-actin of the C-terminal half of both villin and gelsolin requires Ca2+. Creation of hybrid proteins demonstrated that the domains of villin and gelsolin are not interchangeable (12).Abundant x-ray crystallographic structural information exists for gelsolin, including the calcium ion-free (Ca2+-free), inactive structure of the intact protein (13), the activated N- and C-terminal halves, each in a bimolecular complex with actin (7, 14), and the activated C-terminal half on its own (15, 16). Structural data for intact villin are unavailable and are limited to fragment V1 (17), solved using NMR methods, and the HP domain, solved by NMR and x-ray crystallography (18, 19). NMR experiments also indicate that HP is connected to V6 by a 40-residue disordered linker. As a result, HP has been proposed to bind actin independently of the remainder of the protein (10).In this report, we present the structure of Ca2+-free, isolated villin V6, which exhibits a typical gelsolin domain fold. The long helix in V6 in this structure is straight, unlike the corresponding helix in G6 of intact Ca2+-free gelsolin, which is bent, and only straightens on calcium activation of the intact protein. Hence, V6 appears to be in an active conformation in the absence of Ca2+. Molecular dynamics simulations indicate that the preferred state of the long helix is also straight for isolated G6 in the absence of Ca2+. Furthermore, they suggest a bistable mechanism of helix conformational change regulated by the presence of the remaining domains, by calcium ions, and by other interactants. We therefore propose a mechanism for the gelsolin family proteins whereby Ca2+ triggers the straightening of the domain 6 helix in the native conformation of the inactive proteins to propagate more widespread conformational changes. 相似文献
993.
994.
Huijuan Liu Jia Ru Jiuhui Qu Ruihua Dai Zijian Wang Chun Hu 《Bioresource technology》2009,100(12):2995-3002
A new biomimetic absorbent, cellulose acetate (CA) embedded with triolein (CA-triolein), was prepared and applied for the removal of persistent organic pollutants (POPs) from micro-polluted aqueous solution. The comparison of CA-triolein, CA and granular activated carbon (GAC) for dieldrin removal was investigated. Results showed that CA-triolein absorbent gave a lowest residual concentration after 24 h although GAC had high removal rate in the first 4 h adsorption. Then the removal efficiency of mixed POPs (e.g. aldrin, dieldrin, endrin and heptachlor epoxide), absorption isotherm, absorbent regeneration and initial column experiments of CA-triolein were studied in detail. The linear absorption isotherm and the independent absorption in binary isotherm indicated that the selected POPs are mainly absorbed onto CA-triolein absorbent by a partition mechanism. The absorption constant, K, was closely related to the hydrophobic property of the compound. Thermodynamic calculations showed that the absorption was spontaneous, with a high affinity and the absorption was an endothermic reaction. Rinsing with hexane the CA-triolein absorbent can be regenerated after absorption of POPs. No significant decrease in the dieldrin removal efficiency was observed even when the absorption–regeneration process was repeated for five times. The results of initial column experiments showed that the CA-triolein absorbent did not reach the breakthrough point at a breakthrough empty-bed volume (BV) of 3200 when the influent concentration was 1–1.5 μg/L and the empty-bed contact time (EBCT) was 20 min. 相似文献
995.
Kumiko Ogawa Kyoko Nabae Jianqing Wang Kanako Wake So‐ichi Watanabe Mayumi Kawabe Osamu Fujiwara Satoru Takahashi Toshio Ichihara Seiko Tamano Tomoyuki Shirai 《Bioelectromagnetics》2009,30(3):205-212
The present study was designed to evaluate whether gestational exposure to an EMF targeting the head region, similar to that from cellular phones, might affect embryogenesis in rats. A 1.95‐GHz wide‐band code division multiple access (W‐CDMA) signal, which is one applied for the International Mobile Telecommunication 2000 (IMT‐2000) system and used for the freedom of mobile multimedia access (FOMA), was employed for exposure to the heads of four groups of pregnant CD(SD) IGS rats (20 per group) for gestational days 7–17. The exposure was performed for 90 min/day in the morning. The spatial average specific absorption rate (SAR) for individual brains was designed to be 0.67 and 2.0 W/kg with peak brain SARs of 3.1 and 7.0 W/kg for low (group 3) and high (group 4) exposures, respectively, and a whole‐body average SAR less than 0.4 W/kg so as not to cause thermal effects due to temperature elevation. Control and sham exposure groups were also included. At gestational day 20, all dams were killed and fetuses were taken out by cesarean section. There were no differences in maternal body weight gain. No adverse effects of EMF exposure were observed on any reproductive and embryotoxic parameters such as number of live (243–271 fetuses), dead or resorbed embryos, placental weights, sex ratios, weights or external, visceral or skeletal abnormalities of live fetuses. Bioelectromagnetics 30:205–212, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
996.
Drought stress has long been a major constraint in maintaining yield stability of soybean (Glycine max (L.) Merr.) in rainfed ecosystems. The identification of consistent quantitative trait loci (QTL) involving seed yield per plant (YP) and drought susceptibility index (DSI) in a population across different environments would therefore be important in molecular marker-assisted breeding of soybean cultivars suitable for rainfed regions. The YP of a recombinant line population of 184 F2:7:11 lines from a cross of Kefengl and Nannong1138-2 was studied under water-stressed (WS) and well-watered (WW) conditions in field (F) and greenhouse (G) trials, and DSI for yield was calculated in two trials. Nineteen QTLs associated with YP-WS and YP-WW, and 10 QTLs associated with DSI, were identi- fied. Comparison of these QTL locations with previous findings showed that the majority of these regions control one or more traits re- lated to yield and other agronomic traits. One QTL on molecular linkage group (MLG) K for YP-F, and two QTLs on MLG C2 for YP-G, remained constant across different water regimes. The regions on MLG C2 for YP-WW-F and MLG H for YP-WS-F had a pleiotropic effect on DSI-F, and MLG A1 for YP-WS-G had a pleiotropic effect on DSI-G. The identification of consistent QTLs for YP and DSI across different environments will significantly improve the efficiency of selecting for drought tolerance in soybean. 相似文献
997.
Ke Shen Hao-Jie Wang Lin Shao Jin-Ping Shu Guo-Qing Li 《Journal of insect physiology》2009,55(1):78-84
C. kiangsu adults were observed visiting human urine, especially on hot summer days. The main chemicals in fresh human urine include inorganic salts and CO(NH2)2. When human urine was incubated, NH4HCO3 became the richest nitrogenous compound. The phagostimulants, repellents and attractants in urine were identified here. On the filter papers treated with fresh or incubated urine samples, the 5th instar nymphs and the adults started and continued gnawing around the edges, in contrast to the 3rd and the 4th instar nymphs. The consumed areas were dramatically greater on the filters treated with the urine samples incubated for 3-6 days. The feedings of both male and female adults were also stimulated by several urine-borne components such as NaCl, NaH2PO4, Na2SO4, KCl, NH4Cl and NH4HCO3 but not by CO(NH2)2. Among them NaCl was the most powerful phagostimulant. The repelling, or attractive/arresting effects of CO(NH2)2 and NH4HCO3 were also evaluated by a two-choice test. When exposed to water- and CO(NH2)2 solution-immersed filters simultaneously, the adults prefer to stay on water-immersed filter. In contrast, when provided water- and NH4HCO3 solution-treated filters, the adults prefer to stay on NH4HCO3 solution-treated filter. This demonstrated that CO(NH2)2 acted as a repellent and NH4HCO3 as an attractant/arrestant. In the bamboo forest, similar feeding behavior was also elicited by NaCl, NH4HCO3 but not by CO(NH2)2. Comparing to NaCl solution, a mixed solution of NaCl and CO(NH2)2 (1:1) significantly decreased the consumed area of the treated filters whereas a mixed solution of NaCl and NH4HCO3 (1:1) dramatically increased the consumed area. These results demonstrated that the phagostimulatory effect by NaCl was reduced by CO(NH2)2 in fresh urine and was enhanced by NH4HCO3 in incubated urine. 相似文献
998.
The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes. 相似文献
999.
Meng-Shiou?Lee You-Cheng?Hseu Guan-Hua?Lai Wen-Te?Chang Hsi-Jien?Chen Chi-Hung?Huang Meng-Shiunn?Lee Min-Ying?Wang Jung-Yie?Kao Bang-Jau?You Wen-?Hsin?Lin Yi-Yang?LienEmail author Ming-Kuem?LinEmail author 《Microbial cell factories》2011,10(1):56
Background
Chicken anemia virus (CAV), the causative agent chicken anemia, is the only member of the genus Gyrovirus of the Circoviridae family. CAV is an immune suppressive virus and causes anemia, lymph organ atrophy and immunodeficiency. The production and biochemical characterization of VP1 protein and its use in a subunit vaccine or as part of a diagnostic kit would be useful to CAV infection prevention.Results
Significantly increased expression of the recombinant full-length VP1 capsid protein from chicken anemia virus was demonstrated using an E. coli expression system. The VP1 gene was cloned into various different expression vectors and then these were expressed in a number of different E. coli strains. The expression of CAV VP1 in E. coli was significantly increased when VP1 was fused with GST protein rather than a His-tag. By optimizing the various rare amino acid codons within the N-terminus of the VP1 protein, the expression level of the VP1 protein in E. coli BL21(DE3)-pLysS was further increased significantly. The highest protein expression level obtained was 17.5 g/L per liter of bacterial culture after induction with 0.1 mM IPTG for 2 h. After purification by GST affinity chromatography, the purified full-length VP1 protein produced in this way was demonstrated to have good antigenicity and was able to be recognized by CAV-positive chicken serum in an ELISA assay.Conclusions
Purified recombinant VP1 protein with the gene's codons optimized in the N-terminal region has potential as chimeric protein that, when expressed in E. coli, may be useful in the future for the development of subunit vaccines and diagnostic tests.1000.