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Protein conformation from electron spin relaxation data.   总被引:5,自引:4,他引:1       下载免费PDF全文
Electron spin relaxation data from five ferric proteins are analyzed in terms of the fractal model of protein structures. Details of this model are presented. The results lead to a characterization of protein structures by a single parameter, the fractal dimension, d. This structural parameter is shown to determine the temperature dependence of the Raman electron spin relaxation rate, which varies as T3 + 2d. Computations of d are made using x-ray data for 17 proteins. The results range from d = 1.76 for lysozyme to d = 1.34 for ferredoxin. These values are compared with values of d obtained from the present electron spin relaxation data on five ferric proteins. Typical results are d = 1.34 +/- 0.06 from relaxation data and 1.34 +/- 0.05 from x-ray data for ferredoxin; d = 1.67 +/- 0.03 from relaxation data and 1.66 +/- 0.05 from x-ray data for ferricytochrome c. The data thus support the theoretical model. Applications of this spin resonance technique to the study of changes in protein conformation are discussed.  相似文献   

4.
Twenty species of Pselaphinae are newly recorded from New Brunswick, Canada. This brings the total number of species known from the province to 36. Thirteen of these species are newly recorded for the Maritime provinces of Canada. Dalmosella tenuis Casey and Brachygluta luniger (LeConte) are newly recorded for Canada. Collection and habitat data are presented for these species.  相似文献   

5.
The testes of Drosophila melanogaster provide an important model for the study of stem cell maintenance and differentiation, meiosis, and soma-germline interactions. Testes are typically isolated from adult males 0-3 days after eclosion from the pupal case. The testes of wild-type flies are easily distinguished from other tissues because they are yellow, but the testes of white mutant flies, a common genetic background for laboratory experiments are similar in both shape and color to the fly gut. Performing dissection on a glass microscope slide with a black background makes identifying the testes considerably easier. Testes are removed from the flies using dissecting needles. Compared to protocols that use forceps for testes dissection, our method is far quicker, allowing a well-practiced individual to dissect testes from 200-300 wild-type flies per hour, yielding 400-600 testes. Testes from white flies or from mutants that reduce testes size are harder to dissect and typically yield 200-400 testes per hour.  相似文献   

6.
Extinction rates for terrestrial rodent species from palaeontological sites in the Meade Basin of southwestern Kansas and an archaeological site in New Mexico are compared with extinction rates for modern rodents from locations affected by anthropogenic activities. Background extinction rates are defined as global extinctions occurring over proscribed intervals in the absence of significant environmental perturbations. Background rates for the Meade Basin are estimated at 0–~1.0 E/MSY (extinctions per million species years). Elevated rates from 1.4 to 6.25 E/MSY are associated with volcanic events and Late Pleistocene environmental change. These rates are considerably less than those for rodent extinction rates promoted by human activities during the Holocene, the latter ranging from 42.3 to 50,000 E/MSY.  相似文献   

7.
Webster RP  Demerchant I 《ZooKeys》2012,(186):263-271
Five species of Oxyporinae: Oxyporus occipitalis Fauvel, Oxyporus quinquemaculatus LeConte, Oxyporus major Gravenhorst, Oxyporus rufipennis LeConte, and Oxyporus stygicus Say, are newly recorded from New Brunswick, bringing the number of Oxyporinae known from the province to eight. The first documented records from New Brunswick are provided for Oxyporus kiteleyi reported by Majka et al. (2011). Oxyporus occipitalis and Oxyporus major are newly reported for the Maritime provinces of Canada. Collection and habitat data are presented for all these species.  相似文献   

8.
从形态、解剖、化学等方面对采自陕西秦岭的树花属地衣进行了研究,共报道该属地衣8种。其中,美国树花R.americana和粗糙树花R.aspera为中国新记录种。从形态、解剖和化学方面对两个新记录种作了详细的描述,并提供了外部形态照片。  相似文献   

9.
The anomuran crabs are among the best known crustacean groups from the Pacific coast. However, this group is poorly known from the Caribbean coast of Costa Rica. In this compilation based on the literature and the collection at the Zoology Museum, Biology School, University of Costa Rica, we report the presence of 114 species of the Infraorder Anomura for Costa Rica, 20 species from the Caribbean, 96 species from the Pacific (two are present on both coasts). Twenty-nine species are new reports for Costa Rica, 15 from the Caribbean coast (74% of the total of species from that coast) and 14 from the Pacific (15% of the total from the Pacific). The range often species is extended to Costa Rica, siete from the Caribbean and three from the Pacific. Six species are reported for the first time from Cocos Island, where there are also four endemic species.  相似文献   

10.
A classification scheme for those population models which allow variation in development rates is proposed, based on two ways of modifying standard age-structured models. The resulting classes of models are termed development index models and sojourn time models. General formulations for the two classes of models are developed from two basic balance equations, and numerous specific models from the literature are shown to fit into the scheme. Concepts from competing risks theory are shown to be important in understanding the interplay between mortality and maturation. Relationships among the classes are investigated both for the most general forms of the models and for the simpler forms often used. The scheme can provide guidance in developing appropriate insect population models for specific modelling situations.Contribution 3878871  相似文献   

11.
Wang YG  Lin X  Zhu M 《Biometrics》2005,61(3):684-691
Robust methods are useful in making reliable statistical inferences when there are small deviations from the model assumptions. The widely used method of the generalized estimating equations can be "robustified" by replacing the standardized residuals with the M-residuals. If the Pearson residuals are assumed to be unbiased from zero, parameter estimators from the robust approach are asymptotically biased when error distributions are not symmetric. We propose a distribution-free method for correcting this bias. Our extensive numerical studies show that the proposed method can reduce the bias substantially. Examples are given for illustration.  相似文献   

12.
The commercial exploitation of seaweeds for use as food and for the production of agar, alginate and carrageenan is outlined. The quantities of seaweed harvested for each purpose are tabulated and discussed. Seaweeds for food are derived chiefly from China, Japan and Korea, with almost 94% obtained by cultivation. Alginophytes are collected in 15 countries but six of these account for more than 80% of the total harvest; all are from natural stocks except for a large quantity of Laminaria cultivated in China. Natural carrageenophytes, from 12 countries, now account for only 20% of the total harvest; the remainder is cultivated Eucheuma species, 99% of which is produced in only two countries, the Philippines and Indonesia. Of the four categories of commercial resources of seaweeds considered, agarophytes are spread more evenly over a greater number of countries; they come from 20 countries and only five of these are minor contributors to the total. Gelidium species are particularly important because of the high quality agar they yield; their distribution and location are discussed.  相似文献   

13.
Thirteen species of Tenebrionidae are newly reported for New Brunswick, Canada. Paratenetus punctatus Spinola, Pseudocistela brevis (Say), Mycetochara foveata (LeConte), and Xylopinus aenescens LeConte are recorded for the first time from the Maritime provinces. Platydema excavatum (Say) is removed from the faunal list of New Brunswick, and the presence of Platydema americanum Laporte and Brullé for the province is confirmed. This brings the total number of species of Tenebrionidae known from New Brunswick to 42. Two species of Zopheridae, Bitoma crenata Fabricius and Synchita fuliginosa Melsheimer, are newly recorded for New Brunswick, bringing the number of species known from the province to four. Bitoma crenata is new to the Maritime provinces. Collection and habitat data are presented for these species.  相似文献   

14.
Summary Distance sampling is a widely used methodology for assessing animal abundance. A key requirement of distance sampling is that samplers (lines or points) are placed according to a randomized design, which ensures that samplers are positioned independently of animals. Often samplers are placed along linear features such as roads, so that bias is expected if animals are not uniformly distributed with respect to distance from the linear feature. We present an approach for analyzing distance data from a survey when the samplers are points placed along a linear feature. Based on results from a simulation study and from a survey of Irish hares in Northern Ireland conducted from roads, we conclude that large bias may result if the position of samplers is not randomized, and analysis methods fail to account for nonuniformity.  相似文献   

15.
Using genetic markers in phycological research   总被引:2,自引:1,他引:1  
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16.
How reliable are dung counts for estimating elephant numbers?   总被引:4,自引:0,他引:4  
Dung counts are the most commonly used techniques for estimating elephant numbers in forests, yet there is considerable scepticism concerning their accuracy. Published accounts of dung counts show that they give estimates similar to those from other methods for vertebrates ranging in size from lizards to elephants. For ungulates, macropods and elephants there are strong correlations between estimates from dung counts and other methods. Thus, dung counts are as accurate or inaccurate as other methods for estimating vertebrate numbers, including elephants. Dung counts for elephants give estimates that are as precise as, and sometimes more precise than, those from aerial surveys of elephants. This is because the variance in dung density is usually low and results in a lower than expected variance for the final elephant estimate when combined with the variances of defecation and decay rates. Dung counts may be more appropriate than aerial surveys for monitoring small or declining elephant populations.  相似文献   

17.
Mitton JB  Pierce BA 《Genetics》1980,95(4):1043-1054
Estimation of the distribution of the level of individual heterozygosity within natural populations is explored with both Monte-Carlo simulation studies and data from natural populations. Simulations indicate that heterozygosities estimated from as few as a dozen randomly chosen loci may, to some degree, reflect (r = 0.35) heterozygosity determined by 100 independent loci. The shape of the expected distribution of heterozygosity is heavily dependent upon levels of heterozygosity at the loci. Complete genetic data for 12 loci from 997 Fundulus heteroclitus are used to describe the distributions of heterozygosity for different localities, for age classes and for sexes. The distributions deviate from normality. Distributions from different localities are not different, but the distributions are heterogeneous among age classes at one of two localities and are heterogeneous between the sexes.  相似文献   

18.
利用生物信息学方法,对GeneBank中截至2006年9月收录的全部来源于山羊基因的共计637条表达序列标签(EST)进行了综合及分类分析。结果显示,在来源于绒山羊含毛囊皮肤的392条EST序列中有48条为编码角蛋白或角蛋白关联蛋白的基因;在乳腺来源的245条EST中则无此类基因,而是如免疫球蛋白基因、维生素转运蛋白基因、MHC等诸多种类基因,以免疫和酶类居多。两类不同组织来源的FST相应基因相似之处最显著的是编码核糖体蛋白的基因,其中含毛囊皮肤组织的EST中有15.1%,乳腺组织为21.6%,并且有两种不同组织来源的EST组成的26条基序(contigs)中,编码核糖体蛋白的有17条,高达65.4%。  相似文献   

19.
The Tripterygiidae of New Caledonia are revised and their zoogeographical relationships discussed. A total of 27 species is recognized from the territory; three species are recorded from New Caledonia for the first time [Enneapterygius howensis Fricke, 1997; Enneapterygius rhabdotus Fricke, 1994; Helcogramma trigloides (Bleeker, 1858)]. From Grande Terre, 26 species are known, with four species recorded for the first time. Seven species occur at the Ile des Pins (all new records); from the Chesterfield Islands, six species of tripterygiid fishes have been recorded; and from the Loyalty Islands, 17 species are known, with three species recorded from the island group for the first time: 15 species from Ouvéa, 11 species from Lifou (eight new records) and five species from Maré (three new records).  相似文献   

20.
Eight species of Lycidae are newly recorded from New Brunswick, Canada, bringing the total number of species known from the province to 16. The first documented records from New Brunswick are provided for Greenarius thoracicus (Randall) Erotides scuptilis (Say), and Calopteron terminale (Say) reported by Majka et al. (2011). Eropterus arculus Green, Lopheros crenatus (Germar), and Calochromus perfacetus (Say) are reported for the first time in the Maritime provinces. Collection data, habitat data, and distribution maps are presented for all these species.  相似文献   

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