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71.
Feedback repression is required for mammalian circadian clock function 总被引:13,自引:0,他引:13
Sato TK Yamada RG Ukai H Baggs JE Miraglia LJ Kobayashi TJ Welsh DK Kay SA Ueda HR Hogenesch JB 《Nature genetics》2006,38(3):312-319
72.
Bouvignies G Vallurupalli P Hansen DF Correia BE Lange O Bah A Vernon RM Dahlquist FW Baker D Kay LE 《Nature》2011,477(7362):111-114
Proteins are inherently plastic molecules, whose function often critically depends on excursions between different molecular conformations (conformers). However, a rigorous understanding of the relation between a protein's structure, dynamics and function remains elusive. This is because many of the conformers on its energy landscape are only transiently formed and marginally populated (less than a few per cent of the total number of molecules), so that they cannot be individually characterized by most biophysical tools. Here we study a lysozyme mutant from phage T4 that binds hydrophobic molecules and populates an excited state transiently (about 1?ms) to about 3% at 25?°C (ref. 5). We show that such binding occurs only via the ground state, and present the atomic-level model of the 'invisible', excited state obtained using a combined strategy of relaxation-dispersion NMR (ref. 6) and CS-Rosetta model building that rationalizes this observation. The model was tested using structure-based design calculations identifying point mutants predicted to stabilize the excited state relative to the ground state. In this way a pair of mutations were introduced, inverting the relative populations of the ground and excited states and altering function. Our results suggest a mechanism for the evolution of a protein's function by changing the delicate balance between the states on its energy landscape. More generally, they show that our approach can generate and validate models of excited protein states. 相似文献
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74.
We measured the carotid body volume of rats treated with chronic hypoxia alone and chronic hypoxia together with a single neonatal injection of N-ethyl-N-nitrosourea (10 mg/kg). All the animals so treated showed enlargement of their carotid bodies, but no carotid body chemodectomas occurred. 相似文献
75.
76.
The dietary habits of the early hominids Australopithecus and Paranthropus have long been debated. Robinson argued that the two species differed in the proportions of meat and vegetables consumed. More recently it has been suggested that Paranthropus, with its presumably larger body size, simply processed greater amounts of the same foods eaten by Australopithecus to maintain 'functional equivalence'. Microscopic dental wear patterns are related to the dietary habits of extant mammals, and quantification of these patterns is useful in distinguishing among primates with different diets. Nevertheless, few attempts have been made to use microwear in the reconstruction of early hominid diets, and only very recently has the quantification of such data been initiated. While microwear fabrics can be reduced to individual elements (for example, scratches and pits), there is some disagreement over exactly how they should be defined and measured. Fourier transforms have been applied successfully in the study of a variety of physical and biological patterns, and recently they have been used to characterize and distinguish different tooth wear patterns more objectively. Here we report the first combined use of image processing and other quantitative techniques to analyse the dental microwear of early hominids. Our results suggest that Paranthropus ate substantially more hard food items than Australopithecus. 相似文献
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78.
Zusammenfassung Einfache und schnelle Methode zur Isolierung freier Mäuse-Leberzellen. Freie Hepatozyten (bis 50% des Gewebes) zeigen so aktiven Stoffwechsel.
This work was supported by grant No. CA05172 of the National Cancer Institute, U.S.P.H.S. 相似文献
This work was supported by grant No. CA05172 of the National Cancer Institute, U.S.P.H.S. 相似文献
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80.
Prüfer K Munch K Hellmann I Akagi K Miller JR Walenz B Koren S Sutton G Kodira C Winer R Knight JR Mullikin JC Meader SJ Ponting CP Lunter G Higashino S Hobolth A Dutheil J Karakoç E Alkan C Sajjadian S Catacchio CR Ventura M Marques-Bonet T Eichler EE André C Atencia R Mugisha L Junhold J Patterson N Siebauer M Good JM Fischer A Ptak SE Lachmann M Symer DE Mailund T Schierup MH Andrés AM Kelso J Pääbo S 《Nature》2012,486(7404):527-531
Two African apes are the closest living relatives of humans: the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). Although they are similar in many respects, bonobos and chimpanzees differ strikingly in key social and sexual behaviours, and for some of these traits they show more similarity with humans than with each other. Here we report the sequencing and assembly of the bonobo genome to study its evolutionary relationship with the chimpanzee and human genomes. We find that more than three per cent of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other. These regions allow various aspects of the ancestry of the two ape species to be reconstructed. In addition, many of the regions that overlap genes may eventually help us understand the genetic basis of phenotypes that humans share with one of the two apes to the exclusion of the other. 相似文献