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Y. Lass S. Akselrod B. Gavish S. Cohen A. Fisher 《Cellular and molecular life sciences : CMLS》1979,35(5):650-652
Summary Time course measurements of the action of muscarinic antagonists were performed in the spontaneously beating carp atrium. Several high affinity drugs, which embody the quinuclidine structure were examined. The structural flexibility of these molecules was reflected in the dissociation of the drugs from the muscarinic receptor. The dissociation of rigid drugs was very much prolonged as compared to flexible drugs of the same affinity.We thank Prof. S. Lifson for helpful discussion and Mrs M. Bendikovsky for technical assistance. This work was supported by a USA-Israel Binational Science Foundation (BSF-Jerusalem) grant to Y. Lass. 相似文献
234.
I. Cohen M. Djaldetti U. Sandbank Ch. Klibansky A. de Vries 《Cellular and molecular life sciences : CMLS》1966,22(10):662-663
Résumé Les lymphocytes de cobayes inoculés avec du venin de serpentEchis colorata, additionné de fluorescéinc, acquièrent une forte fluorescence. Le même effet du venin est observé avec des lymphocytes traités in vitro. Les fractions protéolytiques du venin sont responsables de ce phénomène, alors que la phospholipasc est sans effet. 相似文献
235.
Zusammenfassung Es werden neue Befunde beigebracht, die für die Bildung von Superoxyd-Radikal durch DMPH4, ein biologisch wichtiges Pterinderivat, sprechen.
This work was supported by the Clinical Research Center for Parkinsons and Allied Diseases and USPHS Grant No. NS-05184. 相似文献
This work was supported by the Clinical Research Center for Parkinsons and Allied Diseases and USPHS Grant No. NS-05184. 相似文献
236.
Solar ultraviolet light creates excited electronic states in DNA that can decay to mutagenic photoproducts. This vulnerability is compensated for in all organisms by enzymatic repair of photodamaged DNA. As repair is energetically costly, DNA is intrinsically photostable. Single bases eliminate electronic energy non-radiatively on a subpicosecond timescale, but base stacking and base pairing mediate the decay of excess electronic energy in the double helix in poorly understood ways. In the past, considerable attention has been paid to excited base pairs. Recent reports have suggested that light-triggered motion of a proton in one of the hydrogen bonds of an isolated base pair initiates non-radiative decay to the electronic ground state. Here we show that vertical base stacking, and not base pairing, determines the fate of excited singlet electronic states in single- and double-stranded oligonucleotides composed of adenine (A) and thymine (T) bases. Intrastrand excimer states with lifetimes of 50-150 ps are formed in high yields whenever A is stacked with itself or with T. Excimers limit excitation energy to one strand at a time in the B-form double helix, enabling repair using the undamaged strand as a template. 相似文献
237.
Detachment fronts and the onset of dynamic friction 总被引:2,自引:0,他引:2
The dynamics of friction have been studied for hundreds of years, yet many aspects of these everyday processes are not understood. One such aspect is the onset of frictional motion (slip). First described more than 200 years ago as the transition from static to dynamic friction, the onset of slip is central to fields as diverse as physics, tribology, mechanics of earthquakes and fracture. Here we show that the onset of frictional slip is governed by three different types of coherent crack-like fronts: these are observed by real-time visualization of the net contact area that forms the interface separating two blocks of like material. Two of these fronts, which propagate at subsonic and intersonic velocities, have been the subject of intensive recent interest. We show that a third type of front, which propagates an order of magnitude more slowly, is the dominant mechanism for the rupture of the interface. No overall motion (sliding) of the blocks occurs until either of the slower two fronts traverses the entire interface. 相似文献
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Why so many sperms? An essay on the arithmetic of reproduction 总被引:1,自引:0,他引:1
J Cohen 《Science progress》1969,57(225):23-41
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