Conformations of signal peptides induced by lipids suggest initial steps in protein export   总被引：21，自引：0，他引：21  

M S Briggs  D G Cornell  R A Dluhy  L M Gierasch 《Science (New York, N.Y.)》1986,233(4760):206-208

Despite the requirement for a functional signal sequence in protein export, little is known of the conformational properties and membrane interactions of these highly hydrophobic amino terminal extensions on nearly all exported proteins. The Escherichia coli lambda phage receptor signal sequence was studied in phospholipid monolayers by circular dichroism and Fourier transform infrared spectroscopy; the signal peptide was shown to prefer an alpha-helical conformation when inserted into the lipid phase. However, interaction with the lipid surface without insertion induced the signal sequence, which is unstructured in bulk aqueous solution, to adopt a beta structure. These observations are combined in a model for the initial steps in signal sequence-membrane interaction in vivo.  相似文献   

INSECT TRANSMISSION EXPERIMENTS WITH HERPESENCEPHALITIS VIRUS     

Simmons JS  Kelser RA  Cornell VH 《Science (New York, N.Y.)》1933,78(2020):243-246

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Impacts of atmospheric anthropogenic nitrogen on the open ocean   总被引：3，自引：0，他引：3  

Duce RA  LaRoche J  Altieri K  Arrigo KR  Baker AR  Capone DG  Cornell S  Dentener F  Galloway J  Ganeshram RS  Geider RJ  Jickells T  Kuypers MM  Langlois R  Liss PS  Liu SM  Middelburg JJ  Moore CM  Nickovic S  Oschlies A  Pedersen T  Prospero J  Schlitzer R  Seitzinger S  Sorensen LL  Uematsu M  Ulloa O  Voss M  Ward B  Zamora L 《Science (New York, N.Y.)》2008,320(5878):893-897

Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to approximately 1.6 teragrams of nitrous oxide (N2O) per year. Although approximately 10% of the ocean's drawdown of atmospheric anthropogenic carbon dioxide may result from this atmospheric nitrogen fertilization, leading to a decrease in radiative forcing, up to about two-thirds of this amount may be offset by the increase in N2O emissions. The effects of increasing atmospheric nitrogen deposition are expected to continue to grow in the future.  相似文献   

Maximum parasitism rates and successful biological control     

Hawkins BA  Cornell HV 《Science (New York, N.Y.)》1994,266(5192):1886

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Cortisol stimulates intestinal fluid uptake in Atlantic salmon (Salmo salar) in the post-smolt stage     

Sean C. Cornell  David M. Portesi  Philip A. Veillette  Kristina Sundell  Jennifer L. Specker 《Fish physiology and biochemistry》1994,13(3):183-190

The fluid uptake rate of the posterior intestine of salmonids increases during the parr-smolt transformation. Intestinal fluid uptake in post-smolt Atlantic salmon was investigated after treatment with cortisol and growth hormone (GH), alone or together. Two replicate experiments were conducted in August 1991 and August 1992. Cortisol was emulsified in vegetable shortening and vegetable oil (1:1) and implanted into the peritoneal cavity. GH was administered as intraperitoneal injections in a saline vehicle on days 0 and 2. On days 5 and 6, plasma cortisol levels, gill Na⁺,K⁺-ATPase activity, andin vitro measurements of fluid transport rate (J_v) across the posterior intestine were measured. Implants of cortisol elevated the plasma cortisol levels within a physiological range, and resulted in elevated gill Na⁺,K⁺-ATPase activity, as expected. The fluid uptake rate across the posterior intestine was roughly doubled by cortisol treatment. GH treatment did not affect intestinal fluid transport, gill Na⁺,K⁺-ATPase activity, or plasma cortisol concentrations. The seawater-adapting increase in the rate of fluid uptake by the posterior intestine of smolting salmon is probably stimulated by elevated plasma cortisol concentrations.  相似文献   

Disentangling the drivers of β diversity along latitudinal and elevational gradients     

Kraft NJ  Comita LS  Chase JM  Sanders NJ  Swenson NG  Crist TO  Stegen JC  Vellend M  Boyle B  Anderson MJ  Cornell HV  Davies KF  Freestone AL  Inouye BD  Harrison SP  Myers JA 《Science (New York, N.Y.)》2011,333(6050):1755-1758

Understanding spatial variation in biodiversity along environmental gradients is a central theme in ecology. Differences in species compositional turnover among sites (β diversity) occurring along gradients are often used to infer variation in the processes structuring communities. Here, we show that sampling alone predicts changes in β diversity caused simply by changes in the sizes of species pools. For example, forest inventories sampled along latitudinal and elevational gradients show the well-documented pattern that β diversity is higher in the tropics and at low elevations. However, after correcting for variation in pooled species richness (γ diversity), these differences in β diversity disappear. Therefore, there is no need to invoke differences in the mechanisms of community assembly in temperate versus tropical systems to explain these global-scale patterns of β diversity.  相似文献   

Comparison of the carbon dioxide laser and the radiofrequency unit for feline onychectomies     

Burns SM  Howerth EW  Rawlings CA  Cornell KK  Radlinsky MG  Mauck JW 《Journal of the American Animal Hospital Association》2010,46(6):375-384

This study compared the collateral tissue damage and incisional bridging with granulation tissue via histopathological examination following feline onychectomy performed by radiofrequency (RF) and carbon dioxide (CO(2)) laser. Two cats were euthanized, and their digits were harvested for histopathological evaluation on days 1, 3, and 7 post-onychectomy. Each digit was evaluated for total lesion width, total necrosis width, and degree of edema, hemorrhage, and inflammation. This study found few significant differences in collateral tissue damage between RF and CO(2) laser, but more incisional bridging by granulation tissue was noted with RF for feline onychectomies. These results indicate that RF for feline onychectomy is a reasonable alternative to CO(2) laser in regard to collateral tissue damage and bridging of the incision by granulation tissue. In addition, RF is not accompanied by the strict safety considerations and initial expense of acquisition of a CO(2) laser.  相似文献   

Comparison and classification of the effects of simple ions and molecules upon the transformation of ferrihydrite into more crystalline products     

Rochelle M. Cornell 《植物养料与土壤学杂志》1987,150(5):304-307

The effects of various simple ions and molecules on the extent and products of the conversion of ferrihydrite into more crystalline products are compared. These ions and molecules can be classified according to how strongly they retard the transformation of ferrihydrite, whether they favour the formation of haematite relative to goethite or whether they retard the formation of goethite more strongly than that of haematite and finally, whether foreign ions can replace a proportion of Fe in the goethite structure. Simple ions and molecules operate through two mechanisms. They adsorb on ferrihydrite and stabilize it and they also act by hindering the nucleation of goethite in solution. Adsorption on ferrihydrite retards the transformation to a far greater extent than does interference in solution.  相似文献   

Pseudopersistent urachus in a baby walrus.     

L H Cornell  B J Golden  K G Osborn 《Journal of the American Veterinary Medical Association》1975,167(7):548-549

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Crystallization of Metal Substituted Ferrihydrites     

Rudolf Giovanoli  Rochelle M. Cornell 《植物养料与土壤学杂志》1992,155(5):455-460

The effects of a series of divalent, first row transition elements, i.e. Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ on the crystallization of ferrihydrite have been compared. With the exception of Mn²⁺, the metal ions considered, stabilized ferrihydrite and enhanced the amount of haematite in the reaction product. The stabilizing ability of these ions could be related to the increase in covalency of these metals along the series. With more than 15 mole% divalent metal ion present, ferrihydrite transformed to a spinel phase by a dissolution/reprecipitation mechanism. These metals can replace some Fe³⁺ in the structures of the crystallization products. Factors that influence the extent of isomorphous substitution are the match between the radii and charges of Fe³⁺ and the substituent ions and also, the congruency of dissolution of the M/ferrihydrite coprecipitate.  相似文献