Genealogies of mouse inbred strains

The mouse is a prime organism of choice for modelling human disease. Over 450 inbred strains of mice have been described, providing a wealth of different genotypes and phenotypes for genetic and other studies. As new strains are generated and others become extinct, it is useful to review periodically what strains are available and how they are related to each other, particularly in the light of available DNA polymorphism data from microsatellite and other markers. We describe the origins and relationships of inbred mouse strains, 90 years after the generation of the first inbred strain. Given the large collection of inbred strains available, and that published information on these strains is incomplete, we propose that all genealogical and genetic data on inbred strains be submitted to a common electronic database to ensure this valuable information resource is preserved and used efficiently.     

Human chromosome 11 DNA sequence and analysis including novel gene identification

Chromosome 11, although average in size, is one of the most gene- and disease-rich chromosomes in the human genome. Initial gene annotation indicates an average gene density of 11.6 genes per megabase, including 1,524 protein-coding genes, some of which were identified using novel methods, and 765 pseudogenes. One-quarter of the protein-coding genes shows overlap with other genes. Of the 856 olfactory receptor genes in the human genome, more than 40% are located in 28 single- and multi-gene clusters along this chromosome. Out of the 171 disorders currently attributed to the chromosome, 86 remain for which the underlying molecular basis is not yet known, including several mendelian traits, cancer and susceptibility loci. The high-quality data presented here--nearly 134.5 million base pairs representing 99.8% coverage of the euchromatic sequence--provide scientists with a solid foundation for understanding the genetic basis of these disorders and other biological phenomena.     

Quantum-enhanced positioning and clock synchronization

A wide variety of positioning and ranging procedures are based on repeatedly sending electromagnetic pulses through space and measuring their time of arrival. The accuracy of such procedures is classically limited by the available power and bandwidth. Quantum entanglement and squeezing have been exploited in the context of interferometry, frequency measurements, lithography and algorithms. Here we report that quantum entanglement and squeezing can also be employed to overcome the classical limits in procedures such as positioning systems, clock synchronization and ranging. Our use of frequency-entangled pulses to construct quantum versions of these protocols results in enhanced accuracy compared with their classical analogues. We describe in detail the problem of establishing a position with respect to a fixed array of reference points.     

Probing the penicillin sidechain selectivity of recombinant deacetoxycephalosporin C synthase

Deacetoxycephalosporin C synthase from Streptomyces clavuligerus catalyses the conversion of the five-membered penicillin ring to the unsaturated six-membered cephem ring of deacetoxycephalosporin C. The effects on enzyme activity of the penicillin substrate sidechain and various cofactors were investigated using a continuous spectrophotometric assay. The conversion of penicillin G to phenylacetyl-7-aminodeacetoxycephalo sporanic acid (G-7-ADCA) was confirmed, and further details of the reaction were elucidated. The conversion of ampicillin to cephalexin was faster than that of acetyl-6-APA to acetyl-7-ADCA kcat = 0.120 +/- 0.001 s(-1) versus 0.035 +/- 0.001 s(-1), but they had similar Km values: 4.86 +/- 0.12 and 3.28 +/- 0.26 mM, respectively. Amoxycillin and penicillin V were also converted at low levels. Conversion was not detected for penicillanate, 6-aminopenicillanate, carbenicillin, temocillin, ticarcillin or benzylpenicilloic acid, suggesting that the enzyme has a relatively strict selectivity for the sidechain of the penicillin substrate.     

Role of metal-reducing bacteria in arsenic release from Bengal delta sediments

The contamination of ground waters, abstracted for drinking and irrigation, by sediment-derived arsenic threatens the health of tens of millions of people worldwide, most notably in Bangladesh and West Bengal. Despite the calamitous effects on human health arising from the extensive use of arsenic-enriched ground waters in these regions, the mechanisms of arsenic release from sediments remain poorly characterized and are topics of intense international debate. We use a microscosm-based approach to investigate these mechanisms: techniques of microbiology and molecular ecology are used in combination with aqueous and solid phase speciation analysis of arsenic. Here we show that anaerobic metal-reducing bacteria can play a key role in the mobilization of arsenic in sediments collected from a contaminated aquifer in West Bengal. We also show that, for the sediments in this study, arsenic release took place after Fe(III) reduction, rather than occurring simultaneously. Identification of the critical factors controlling the biogeochemical cycling of arsenic is one important contribution to fully informing the development of effective strategies to manage these and other similar arsenic-rich ground waters worldwide.     

论科学的“起源”

从文明史中最令人困惑的问题-关于人类认知能力是否存在内存统一性及人类文明多样性的原因-入手,演讲者通过古代巴比伦、中国和希腊人关于天空的认识和研究,试图对科学的“起源”这一不可能有确定答案的历史命题展开理论叙述。演讲者认为,复杂的经济、技术和政治结构对人类认知自然的模式产生了巨大的影响。在巴比伦、中国和希腊,无论就所从事的研究的本质,还是就研究者所在的的社会与文化制度,科学的发展是很不相同的,在有些情况下在研究与制度之间显露出一定的关联。同时,那些行千差万别但都可能被认为对研究发展起到一定作用的因素之间的张力是十分重要的,其后果是没有一个因素是全然有助于发展的;每个体系的先进与落后以一种惊人的方式成为另一个的镜象。从一方面讲,国家的支持和制度的建立为研究带来了巨大的好处,为特殊专业训练的研究者组成的可观队伍提供了稳定的职位,然而这样的制度也可能抑制创新。另一方面,没有这些制度,个人可以远为自由地选择自己的研究项目,当然没有稳定的职业。在希腊与这种不稳定的竞争导致对假设的根本审查,但就像肯定要抑制一致意见的形成一样,一个由个人努力联合起来表现出的优势,同一个本来就是统一的研究纲领还是不能相比的。希腊智慧的光辉给人以深刻印象,在天文观测上持久不断的努力则使中国赢得易如反掌。