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81.
Synthesis and characterization of 8-methoxy-2'- deoxyadenosine-containing oligonucleotides to probe the syn glycosidic conformation of 2'-deoxyadenosine within DNA. 下载免费PDF全文
The synthesis of 8-methoxy-2'-deoxyadenosine (moA) protected at N6 as an N,N-dimethylformamidine derivative and incorporation of the modified nucleoside into oligodeoxynucleotides via the phosphoramidite method are described. UV thermal denaturation studies were conducted on duplexes containing moA:G, moA:C and moA:T base pairs to determine the thermodynamic stability of duplexes containing moA relative to their adenosine (A)-containing counterparts. In the case of moA:G base pairs the effect of moA substitution is sequence dependent. In A:G mismatch-containing sequences, which have been shown by structural characterization to have a syn conformational preference at the glycosidic bond of A, moA substitution results in stabilization of the duplex. In contrast, in sequences where the A in the A:G mismatch has been shown to prefer the anti conformation moA substitution is destabilizing to the duplex. Thus moA may be a useful probe for investigating the conformational preferences of the N-glycosidic bond of adenosine within DNA. In addition, moA nucleoside is more resistant to acid-catalyzed depurination than previously described 8-bromo-2'-deoxyadenosine, allowing for facile incorporation into oligonucleotides via automated solid phase DNA synthesis. 相似文献
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Dietrich Burkhardt 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1972,81(2):203-214
Summary The mass response (ERG) of the compound eye of the Malaysian stalked-eye flyCyrtodiopsis dalmanni was recorded by means of conventional electrophysiological techniques. The ERG consists of a positive on-effect, a sustained negative potential during illumination and a negative off-effect, it resembles that ofCalliphora as described by Autrum (1950). As compared with data derived fromCalliphora under identical conditions the eye ofCyrtodiopsis is more sensitive to weak stimuli and shows considerable adaptation. The spectral response curve reveals peaks at 360 nm, around 450 nm and around 490 nm. Above 550 nm the response curve rises steeply, even with stimuli above 700 nm reactions may be elicited. Most probably this effect is caused by weak absorption of long wavelength radiation in the screening pigments.With simple techniques it is fairly easy to record impulse activity from single units of the optic tract within the eye-stalk. This makesCyrtodiopsis a favorable object for experimental studies on data processing in insect optic centers.The characteristics of the diopsid eye are discussed in context with the environmental conditions in the biotop.I would like to thank the colleagues at the University of Malaya, Kuala Lumpur, Malaysia, for help and hospitality.The investigations were supported by a grant from the Sonderforschungsbereich Vergleichende Sinnes- und Nervenphysiologie at the University of Frankfurt (Main). 相似文献
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H. Cottier F. Meister A. Zimmermann R. Kraft A. Burkhardt P. Gehr G. Poretti 《Radiation and environmental biophysics》1987,26(4):275-282
Summary Large lung sections of humans of advanced adult age revealed a markedly nonuniform retention pattern of dense anthracotic particle aggregates, with an impressive accumulation of this material along pulmonary lymphatics, i.e. the deep (peribronchial), septal (perivenous) and superficial (pleural) networks. Conversely, the alveolar parenchyme contained only occasional, small aggregates of macrophages heavily loaded with carbon, representing little more than 2% of this material in lung tissue. Although translocation kinetics of anthracotic particles cannot readily be compared to those of highly toxic -emitting, poorly soluble radionuclides such as239PuO2, lymphatic drainage of the latter over the years may also be expected to lead to a concentration of radioactive material along lymph vessels. Since human data on the effects of inhaled239PuO2 are virtually lacking, the above distribution pattern is apt to help in identifying cells and other tissue components most heavily at risk. Findings are also relevant to the problem of hot spot formation in vivo and its possible sequelae. The latter are briefly discussed with regard to both stochastic and non-stochastic effects.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday 相似文献
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Association of ribosomal subunits is an essential reaction during the initiation phase of protein synthesis. Optimal conditions for 70S formation in vitro were determined to 20 mM Mg2+ and 30 mM K+. Under these conditions, the association reaction proceeds with first order kinetics, suggesting a conformational change to be the rate-limiting step. 70S formation separates into two sub-reactions, the adaptation of the ribosomal subunits to the association conditions and the association step itself. The activation energy of the process was determined to 78 kJ/mol and revealed to be required exclusively for the adaptation of the small subunit, rather than the large subunit or the association step. The presence of mRNA [poly(U)] together with cognate AcPhe-tRNA, accelerates the association rate significantly, forming a well-defined 70S peak in sucrose gradient profiles. mRNA alone provokes an equivalent acceleration, however, the resulting 70S couple impresses as an ill-defined, broad peak, probably indicating the readiness of the ribosome for tRNA binding, upon which the ribosome flips into a defined state. 相似文献