Loss of IGF2 imprinting: a potential marker of colorectal cancer risk   总被引：1，自引：0，他引：1  

Cui H  Cruz-Correa M  Giardiello FM  Hutcheon DF  Kafonek DR  Brandenburg S  Wu Y  He X  Powe NR  Feinberg AP 《Science (New York, N.Y.)》2003,299(5613):1753-1755

Loss of imprinting (LOI), an epigenetic alteration affecting the insulin-like growth factor II gene (IGF2), is found in normal colonic mucosa of about 30% of colorectal cancer (CRC) patients, but it is found in only 10% of healthy individuals. In a pilot study to investigate the utility of LOI as a marker of CRC risk, we evaluated 172 patients at a colonoscopy clinic. The adjusted odds ratio for LOI in lymphocytes was 5.15 for patients with a positive family history [95% confidence interval (95% CI), 1.70 to 16.96; probability P = 0.002], 3.46 for patients with adenomas (95% CI, 1.14 to 11.37; P = 0.026), and 21.7 for patients with CRC (95% CI, 3.48 to 153.6; P = 0.0005). LOI can be assayed with a DNA-based blood test, and it may be a valuable predictive marker of an individual's risk for CRC.  相似文献   

Comment on "Little evidence for developmental plasticity of adult hematopoietic stem cells"     

Theise ND  Krause DS  Sharkis S 《Science (New York, N.Y.)》2003,299(5611):1317; author reply 1317

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Acetabularia chloroplast DNA: electron microscopic visualization   总被引：2，自引：0，他引：2  

B R Green  H Burton 《Science (New York, N.Y.)》1970,168(934):981-982

Isolated chloroplasts of Acetabularia mediterranea, lysed by osmotic shock in a protein monolayer, released large amounts of supercoiled DNA. In some cases, the DNA radiated in large loops from centers of organization. The amount of DNA per chloroplast may be similar to that of a bacterium.  相似文献   

Generation of a large combinatorial library of the immunoglobulin repertoire in phage lambda   总被引：77，自引：0，他引：77  

W D Huse  L Sastry  S A Iverson  A S Kang  M Alting-Mees  D R Burton  S J Benkovic  R A Lerner 《Science (New York, N.Y.)》1989,246(4935):1275-1281

A novel bacteriophage lambda vector system was used to express in Escherichia coli a combinatorial library of Fab fragments of the mouse antibody repertoire. The system allows rapid and easy identification of monoclonal Fab fragments in a form suitable for genetic manipulation. It was possible to generate, in 2 weeks, large numbers of monoclonal Fab fragments against a transition state analog hapten. The methods described may supersede present-day hybridoma technology and facilitate the production of catalytic and other antibodies.  相似文献   

Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein     

Kochendoerfer GG  Chen SY  Mao F  Cressman S  Traviglia S  Shao H  Hunter CL  Low DW  Cagle EN  Carnevali M  Gueriguian V  Keogh PJ  Porter H  Stratton SM  Wiedeke MC  Wilken J  Tang J  Levy JJ  Miranda LP  Crnogorac MM  Kalbag S  Botti P  Schindler-Horvat J  Savatski L  Adamson JW  Kung A  Kent SB  Bradburne JA 《Science (New York, N.Y.)》2003,299(5608):884-887

We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.  相似文献   

Microfluidic bubble logic     

Prakash M  Gershenfeld N 《Science (New York, N.Y.)》2007,315(5813):832-835

We demonstrate universal computation in an all-fluidic two-phase microfluidic system. Nonlinearity is introduced into an otherwise linear, reversible, low-Reynolds number flow via bubble-to-bubble hydrodynamic interactions. A bubble traveling in a channel represents a bit, providing us with the capability to simultaneously transport materials and perform logical control operations. We demonstrate bubble logic AND/OR/NOT gates, a toggle flip-flop, a ripple counter, timing restoration, a ring oscillator, and an electro-bubble modulator. These show the nonlinearity, gain, bistability, synchronization, cascadability, feedback, and programmability required for scalable universal computation. With increasing complexity in large-scale microfluidic processors, bubble logic provides an on-chip process control mechanism integrating chemistry and computation.  相似文献   

CO2-forced climate and vegetation instability during Late Paleozoic deglaciation     

Montañez IP  Tabor NJ  Niemeier D  Dimichele WA  Frank TD  Fielding CR  Isbell JL  Birgenheier LP  Rygel MC 《Science (New York, N.Y.)》2007,315(5808):87-91

The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.  相似文献   

Comment on "Avian extinction and mammalian introductions on oceanic islands"     

Didham RK  Ewers RM  Gemmell NJ 《Science (New York, N.Y.)》2005,307(5714):1412; author reply 1412

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Pattern in escalations in insurgent and terrorist activity     

Johnson N  Carran S  Botner J  Fontaine K  Laxague N  Nuetzel P  Turnley J  Tivnan B 《Science (New York, N.Y.)》2011,333(6038):81-84

In military planning, it is important to be able to estimate not only the number of fatalities but how often attacks that result in fatalities will take place. We uncovered a simple dynamical pattern that may be used to estimate the escalation rate and timing of fatal attacks. The time difference between fatal attacks by insurgent groups within individual provinces in both Afghanistan and Iraq, and by terrorist groups operating worldwide, gives a potent indicator of the later pace of lethal activity.  相似文献   

Structural basis of a phototropin light switch     

Harper SM  Neil LC  Gardner KH 《Science (New York, N.Y.)》2003,301(5639):1541-1544

Phototropins are light-activated kinases important for plant responses to blue light. Light initiates signaling in these proteins by generating a covalent protein-flavin mononucleotide (FMN) adduct within sensory Per-ARNT-Sim (PAS) domains. We characterized the light-dependent changes of a phototropin PAS domain by solution nuclear magnetic resonance spectroscopy and found that an alpha helix located outside the canonical domain plays a key role in this activation process. Although this helix associates with the PAS core in the dark, photoinduced changes in the domain structure disrupt this interaction. We propose that this mechanism couples light-dependent bond formation to kinase activation and identifies a signaling pathway conserved among PAS domains.  相似文献