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Zusammenfassung Nach Bestrahlung mit UV- und ge-, wöhnlichem Licht entstehen in Dünnschichtchromatogrammen von Tyrosin, Thyronin und ihren Jodderivaten wie auch Dopa und Dopamin dunkle Flecken an den entsprechenden Stellen dieser Substanzen. UV-Licht ist für das Auftreten der Pigmente verantwortlich, welche melaninähnliche Polymere zu sein scheinen. 相似文献
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Krantz ID McCallum J DeScipio C Kaur M Gillis LA Yaeger D Jukofsky L Wasserman N Bottani A Morris CA Nowaczyk MJ Toriello H Bamshad MJ Carey JC Rappaport E Kawauchi S Lander AD Calof AL Li HH Devoto M Jackson LG 《Nature genetics》2004,36(6):631-635
Cornelia de Lange syndrome (CdLS; OMIM 122470) is a dominantly inherited multisystem developmental disorder characterized by growth and cognitive retardation; abnormalities of the upper limbs; gastroesophageal dysfunction; cardiac, ophthalmologic and genitourinary anomalies; hirsutism; and characteristic facial features. Genital anomalies, pyloric stenosis, congenital diaphragmatic hernias, cardiac septal defects, hearing loss and autistic and self-injurious tendencies also frequently occur. Prevalence is estimated to be as high as 1 in 10,000 (ref. 4). We carried out genome-wide linkage exclusion analysis in 12 families with CdLS and identified four candidate regions, of which chromosome 5p13.1 gave the highest multipoint lod score of 2.7. This information, together with the previous identification of a child with CdLS with a de novo t(5;13)(p13.1;q12.1) translocation, allowed delineation of a 1.1-Mb critical region on chromosome 5 for the gene mutated in CdLS. We identified mutations in one gene in this region, which we named NIPBL, in four sporadic and two familial cases of CdLS. We characterized the genomic structure of NIPBL and found that it is widely expressed in fetal and adult tissues. The fly homolog of NIPBL, Nipped-B, facilitates enhancer-promoter communication and regulates Notch signaling and other developmental pathways in Drosophila melanogaster. 相似文献
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Elliot JL Ates A Babcock BA Bosh AS Buie MW Clancy KB Dunham EW Eikenberry SS Hall DT Kern SD Leggett SK Levine SE Moon DS Olkin CB Osip DJ Pasachoff JM Penprase BE Person MJ Qu S Rayner JT Roberts LC Salyk CV Souza SP Stone RC Taylor BW Tholen DJ Thomas-Osip JE Ticehurst DR Wasserman LH 《Nature》2003,424(6945):165-168
Stellar occultations--the passing of a relatively nearby body in front of a background star--can be used to probe the atmosphere of the closer body with a spatial resolution of a few kilometres (ref. 1). Such observations can yield the scale height, temperature profile, and other information about the structure of the occulting atmosphere. Occultation data acquired for Pluto's atmosphere in 1988 revealed a nearly isothermal atmosphere above a radius of approximately 1,215 km. Below this level, the data could be interpreted as indicating either an extinction layer or the onset of a large thermal gradient, calling into question the fundamental structure of this atmosphere. Another question is to what extent Pluto's atmosphere might be collapsing as it recedes from the Sun (passing perihelion in 1989 in its 248-year orbital period), owing to the extreme sensitivity of the equilibrium surface pressure to the surface temperature. Here we report observations at a variety of visible and infrared wavelengths of an occultation of a star by Pluto in August 2002. These data reveal evidence for extinction in Pluto's atmosphere and show that it has indeed changed, having expanded rather than collapsed, since 1988. 相似文献
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Influence of a knot on the strength of a polymer strand. 总被引:3,自引:0,他引:3
Many experiments have been done to determine the relative strengths of different knots, and these show that the break in a knotted rope almost invariably occurs at the point just outside the 'entrance' to the knot. The influence of knots on the properties of polymers has become of great interest, in part because of their effect on mechanical properties. Knot theory applied to the topology of macromolecules indicates that the simple trefoil or 'overhand' knot is likely to be present in any long polymer strand. Fragments of DNA have been observed to contain such knots in experiments and computer simulations. Here we use ab initio computational methods to investigate the effect of a trefoil knot on the breaking strength of a polymer strand. We find that the knot weakens the strand significantly, and that, like a knotted rope, it breaks under tension at the entrance to the knot. 相似文献
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The helical repeat of double-stranded DNA varies as a function of catenation and supercoiling 总被引:8,自引:0,他引:8
DNA in the cell is intertwined at several levels: one polynucleotide strand wraps helically around its complement and the double helix is in turn coiled in space. The higher-order intertwining most often takes the form of supercoiling of the helix axis, but can also be observed as the wrapping of one DNA duplex around another, as in catenation. We have investigated the relationship between intertwining at these three levels, the double helix, supercoiling, and catenation, using an approach that relies on comparative measurements of DNA linking numbers by gel electrophoresis. The method determines both the handedness of DNA catenanes and the change in helical repeat that accompanies catenation-induced supercoiling. For multiply-linked catenated rings of 3.5 kilobase pairs (kb), we conclude that the double helix unwinds by two-thirds of a turn for every right-handed supercoil involved in linking the two circles. Altering the geometry of the catenanes by linking rings of dissimilar size changes the effect of catenation on helical and superhelical parameters. Our experiments used intact DNA rings, but we note that linear DNA molecules, by virtue of their subdivision into closed loops or domains in vivo, can intertwine in the same ways. 相似文献
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R. H. Wasserman J. -P. Bonjour H. Fleisch 《Cellular and molecular life sciences : CMLS》1973,29(9):1110-1111
Résumé Une proportion non négligeable de disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) et de disodium dichloromethylenediphosphonate (Cl2MDP) peut être absorbée au niveau de l'ileum de poulet. L'absorption du Cl2MDP est significativement supérieure à celle de l'EHDP.
Acknowledgements. We thank MissLinda Senior for her skillful technical assistance. This work has been supported by the Procter and Gambel Company, by the US National Institute of Health (Grant No. AM 07256) and by the Swiss National Research Fund (Grant No. 3.326.70 Sr). R. H. W. was supported, in part, by the John Simon Guggenheim Foundation. 相似文献
Acknowledgements. We thank MissLinda Senior for her skillful technical assistance. This work has been supported by the Procter and Gambel Company, by the US National Institute of Health (Grant No. AM 07256) and by the Swiss National Research Fund (Grant No. 3.326.70 Sr). R. H. W. was supported, in part, by the John Simon Guggenheim Foundation. 相似文献
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