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51.
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A double helix B-type geometry based on high-resolution proton NMR of single-helical DNA fragments: d(TA)5 x d(TA)5. 总被引:2,自引:2,他引:0
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J R Mellema P N van Kampen C N Carlson H E Bosshard C Altona 《Nucleic acids research》1983,11(9):2893-2905
A single-helical B-type geometry is presented based on 1H NMR observations on d(TATA) and several other small single-helical DNA fragments. The structure is extended to one complete turn of double-helical DNA and its characteristics are compared with other known B-type structures. 相似文献
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Alkaline borohydride degradation of blood group H substance 总被引:5,自引:0,他引:5
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In an isometric tetanus in frog's sartorius muscle tension approaches the plateau exponentially with rate constant α. α a depends on sarcomere length, s, and temperature, T, according to the Arrhenius equation See PDF for Equation for temperatures between 1 and 20°C and for sarcomere lengths 2.0–2.8 µm. The energy of activation, E, does not vary significantly with s; E = 13.9 ± 2.4 kcal/mole. A(s) decreases monotonically with s; A(2.1 µm) is about three times greater than A(2.8 µm). Late in relaxation active tension approaches zero exponentially with rate constant r. r decreases exponentially with increasing duration of tetanus, D, from r0 in a twitch to r∞ for large D. The rate constant for decrease of r with D increases with s and with T. r0 and r∞ obey the Arrhenius equation and decrease with increasing s. 相似文献
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Peripheral nerve interactions and regenerative phenomena were studied in newt forelimbs fused end to end. After simple fusion, one or two spikelike structures regenerated at the plane of fusion in 88% of the cases. When one of the limbs was denervated at the time of fusion, no regeneration occurred from the plane of fusion. If the limbs were fused and one was amputated at the shoulder more than 10 days after fusion, regeneration from the amputation surface did not occur. When the limbs were reamputated 30 days later, regeneration of left limbs from the proximodistally reversed right limb stumps followed. If one of the limbs was denervated at the time of fusion, and amputation was subsequently carried out through the formerly denervated limb, regeneration always took place after the first amputation. On the basis of these results it is postulated that when regenerating nerves of opposite proximodistal polarity meet head-on, the majority of fibers, at least, do not grow into territories occupied by the other nerve. These results have also demonstrated that full limb regeneration can occur at a greater distance from the midline than the end of a normal limb. These experiments also provide a technique for artificially elongating peripheral nerves. 相似文献
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