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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | REPLICATION of the Escherichia coli K-12 chromosome, as shown by genetic and biochemical analysis in vivo, begins at a unique site (oriC) and proceeds bidirectionally1–3. The DNA fragment containing oriC has been isolated by its ability to confer autonomous replication on plasmids or phage whose own replication origin ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Two classes of supercoiled, oriC template DNA were examined. One, pSY317, is a 13.5-kilobase (kb) plasmid which contains a 5.6-kb EcoRI, oriC fragment (from pSY221)5 and a 7.9-kb EcoRI kanamycin-resistance fragment (from pML21)18. The oriC plasmid contains oriC intact, together with extensive flanking sequences. The se... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | replicative intermediates of pSY317 and M13oriC26 appeared in every case as theta-like structures (see Fig. 2). 中文
Fig. 1. Time course of oriC plasmid in dnaA-complementing conditions. Reactions were performed as described previously17 in a 250 μl volume containing 40 mM HEPES pH 7.6, 2 mM ATP, 0.5 mM each of GTP, UTP... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | contaminating RNA and either relaxed with SalI endonuclease (given by K. Burtis) in the presence of ethidium bromide31 (a), or restricted to completion with SalI endonuclease in 10 mM Tris-HCl pH 8.0, 10 mM MgSO4 and 100 mM NaCl at 37°C for 30 min (b). DNA was then spread on to parlodion-coated grids by the formamide t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | intermediates, it is clear that for most of them, replication proceeds bidirectionally. Inspection of the less extensively replicated molecules reveals that initiation occurs at or near oriC. Thus, we have shown that in these conditions, replication of the oriC plasmid pSY317 proceeds bidirectionally from a start in th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (Fig. 5). These findings and similar results for pSY317 (data not shown) confirm that the “eye” and “Y” forms (molecules with a single fork) are replication intermediates. 中文
Fig. 4. Replication of M13oriC26 DNA initiates at oriC and progresses bidirectionally. Reactions were performed as described in Fig. 1 legend in... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The minimal oriC sequence is ~30% of the genome length from one end of M13oriC26 DNA linearized by EcoRI endonuclease (Fig. 4). Recombinant M13 phage DNAs from which oriC has been deleted do not replicate from oriC either in vitro or in vivo17,28. Molecules aligned in Fig. 4 with the longer replicated segment to the ri... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | of the two replication forks or in chain terminations by ddTTP. In this regard, examination of the replicative intermediates of phage λ and F plasmids, which are known to replicate bidirectionally, also reveals molecules that replicate unidirectionally29,30. 中文
The bidirectional replication of M13oriC26, a template int... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Hiraga, S. Proc. Natl. Acad. Sci. U.S.A. 73, 198-202 (1976).
Yasuda, S. & Hirota, Y. Proc. Natl. Acad. Sci. U.S.A. 74, 5458-5462 (1977).
von Meyenburg, K., Hansen, F. G., Nielsen, L. D. & Riise, E. Molec. gen. Genet. 160, 287-295 (1978).
Miki, T., Hiraga, S., Nagata, T. & Yura, T. Proc. Natl. Acad. Sci. U.S.A. 75, 5099... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Eichenlaub, R., Figurski, D. & Helinski, D. R. Proc. Natl. Acad. Sci. U.S.A. 74, 1138-1141 (1977).
Schnöss, M. & Inman, R. B. J. Molec. Biol. 51, 61-73 (1970).
Shortle, D. & Nathans, D. Proc. Natl. Acad. Sci. U.S.A. 75, 2170-2174 (1978).
大肠杆菌染色体起始位点的酶促复制是双向进行的
卡古尼等
编者按
在本文中,分子生物学家阿瑟·科恩伯格与其在加州斯坦福大学的同事对细菌基因组的复制方式提出了新的观点... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 使用从野生型细胞中分离到的酶组分(组分II)[17]所产生的复制中间体在观察到的分子形式中占10%~20%,这一比例与未受抑制的对照反应中的模板分子含量一致。环状DNA分子或单位长度的线性片段与一段DNA片段重叠的偶然排列可能形成与真正的复制中间体类似的结构,不过这种情况发生的概率很低。pSY317和M13oriC26质粒的环状复制中间体在每个实验中都呈现出θ样的结构(见图2)。 英文
图1. 在dnaA互补条件下,含有oriC位点的质粒复制随时间变化的曲线。反应按照之前文献报道的条件进行[17]。反应体积为250 μl,含有40 mM pH 7.6的HEPES,2 mM ATP,GTP、UTP和CTP各0.5 mM,43 mM磷... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 对较短的复制分子的观察表明,复制起始于oriC位点或oriC位点附近的区域。因此我们已经证明了,在这些条件下,含有oriC位点的pSY317质粒的复制起始于oriC位点并且是双向进行的。 英文
图3. pSY317质粒的复制从oriC位点起始并双向进行。使用50 μM ddTTP来制备复制中间体,纯化后使用SalI内切酶消化使之线性化(如图2注所述)。然后随机选取这些复制中间体进行拍照。通过惠普9864A数字转换板测量单个分子未复制的片段和复制后的两个片段的长度,计算复制片段的平均值,将每一部分换算成总长度的百分比,然后,对这些分子进行分析(使用惠普9810A计算机)。只有那些两个复制片段的长度相同(±5%),并且分子总长度与预期... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 在126个分子中有4个似乎并不是从oriC位点起始复制的,我们未分析这些分子。
英文
在我们分析的126个M13oriC26复制中间体中,有4个分子被判定为不是从oriC位点起始复制的,因为它们的复制片段在测量误差范围内(基因组长度的5%,图4)没有与oriC位点重合。这一差异可能是由于复制的异常起始或者双链模板的不正常断裂导致的。对于一些分子的两条DNA模板链来说,双向复制过程似乎是不对称的甚至可能是单向的,这有可能是由于两个复制叉的启动是不同步的或由于ddTTP对链延伸的终止不是同时的。就这一点而言,在对λ噬菌体和F质粒(已知它们的复制是双向进行的)的复制中间体进行分析时,也发现了一些单向复制的分子[29,30]。 英文
M... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The palaeotemperature equation of Epstein et al.1 relates the oxygen-isotope composition of mollusc carbonate shells to the temperature in which it has been deposited. This equation has been applied extensively to derive palaeotemperatures and other palaeoenvironmental parameters for the Pleistocene epoch, based on the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | almost always significantly higher than those observed in the water in which they were collected12–18. It has been proposed that these nonequilibrium isotopic compositions are caused by introduction of metabolic CO2 into the carbonate skeletons, a phenomenon that has been reported in other carbonate depositing organism... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | made using control groups for which the isotopic composition was determined separately. Each experiment lasted roughly 2 weeks; the range of experimental temperatures was between 14 and 30°C, and in each run there were 2 or 3 different temperatures. Because only individuals that went through gametogenic reproduction we... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 1. The isotopic temperature calculated from the oxygen-isotope composition of the shell carbonate of the foraminifer G. sacculifer according to the modified equation of Epstein et al.1 plotted against the actual temperature in which the foraminifers were cultured. The dashed line represents the ideal fit between t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | †The Hebrew University of Jerusalem, Department of Geology, Jerusalem, Israel
Received 14 December 1981; accepted 15 March 1982.
References:
Epstein, S., Buchsbaum, R., Lowenstam, H. A. & Urey, H. C. Bull. Geol. Soc. Am. 64, 1315-1326 (1953).
Emiliani, C. Am. J. Sci. 252, 149-158 (1954); J. Geol. 63, 538-578 (1955).
... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Shackelton, N. J. Colloqu. Int. Cent. Natn. Rech. Scient. No. 219, 203-209 (1973).
Epstein, S. & Mayeda, T. Geochim. Cosmochim. Acta 4, 213-224 (1953).
Craig. H. Proc. Spoleto Conf. on Stable Isotopes in Oceanographic Studies and Paleotemperatures Vol. 3 (ed. Tongiorgi, E.) (1965).
培养条件下温度对浮游有孔虫中氧同位素分馏的控制
埃雷兹,卢斯
编者按
长... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
根据如下方程计算同位素温度,该方程是经克雷格[28]改进后的爱泼斯坦等人[1]的方程:
pt=16.9 – 4.2 (δ18Oc – δ18Ow) + 0.13 (δ18Oc – δ18Ow)2
其中,pt为同位素温度,δ18Oc和δ18Ow分别为碳酸盐和海水的同位素组成。 英文
同位素温度和实际的培养温度比较见图1,两者之间存在高度吻合。利用线性回归得到的最佳拟合线具有如下参数:
t=–0.07 + 1.01pt
其中t和pt分别为实际温度和同位素温度。该线性回归方程的相关系数(r)等于0.95。理想状态下,截距和斜率应分别为0.0和1.0。这里我们得到的值(–0.07和1.01)与理想状态几乎一致,在测定14~30°C的古... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Examination of homologies between retroviral oncogenes and transforming sequences defined by transfection reveals that the human bladder carcinoma (EJ) oncogene is homologous to the Harvey sarcoma virus oncogene (ras). Structural analysis limits the region of homology to a 3.0-kilobase SacI fragment of the EJ oncogene.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The two classes of oncogenes have many properties in common, the most striking of which is the apparent origin of both types of genes from normally benign, cellular genetic elements. Because of this and other parallels, we undertook a search to determine whether the two groups of genes shared any members in common. Suc... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 1, lanes b, d-g and i). Figure 1c shows detection of the human homologue of the v-abl probe; lanes d-g show an analysis of DNAs of mouse cells transfected with four different human oncogenes. None of the DNAs contains any fragments beyond those present in the untransfected mouse control (lane a). We concluded that none... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Figure 2 shows a further Southern blot analysis of DNAs that were prepared from several cell lines derived by transfection of NIH 3T3 cells with DNAs of human tumour cell lines. The probe used was the rat cellular homologue of Harvey sarcoma virus, c-Ha-ras1, given by R. Ellis and E. Scolnick16,17. A novel fragment of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | SW-2-1 is a secondary transfected cell line derived from human colon carcinoma cell line, SW-480 (refs 10, 35); HL60-1-9 is a secondary transfected cell line derived from human leukaemia cell line, HL60 (refs 10, 36); B104-1-1 is a secondary transfected cell line derived from rat neuroblastoma cell line, B104 (refs 7, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 3. Analysis of DNAs from EJ and T24 transfectants using the c-Ha-ras1 and EJ oncogene probes. DNAs were digested with endonuclease BamHI (A, C) or EcoRI (B, D) and analysed as described in Fig. 1 legend. The filters shown A and B were incubated with 5×106 c.p.m. of c-Ha-ras1 DNA probe (2×108c.p.m. μg–1) and expose... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | human fragment present in resulting tertiary transfectants was the 6.6-kb BamHI fragment bearing the EJ oncogene. The three DNAs of the tertiary transfectants were analysed after EcoRI cleavage as it was thought they might have lost some BamHI sites during the second transfection. The DNAs of the three transfectants (F... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Endonuclease-cleaved Φ631 DNA was immobilized on a cellulose nitrate filter and probed with the c-Ha-ras1 sequences. Figure 4a indicates that homology between c-Ha-ras1 and the EJ clone is limited to the 6.6-kb BamHI fragment of the bladder carcinoma oncogene; lane b further reduces the domain of homology between the t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Taken together, these results indicate that the EJ bladder oncogene is closely linked to the human homologue of the rat c-Ha-ras1 sequences. Although the limits of the c-Ha-rasl structural sequences have been well defined16,17,20, the corresponding sequences of the EJ gene have not yet been mapped. Thus, the data above... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | probes, prepared as described in Fig. 1 legend, were annealed to the immobilized RNAs41. Bands which represent sequences homologous to the probes were visualized by autoradiography. Molecular weights were determined by comparison with markers obtained from in vitro run-off transcription of the adenovirus late promoter4... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | lower signal intensity on autoradiography (Fig. 5). This must reflect the relatively lower affinity of the rat probe for human transcripts present in the EJ transfectants. Thus, we conclude that the two probes both detect RNAs transcribed largely, if not entirely, from the human EJ oncogene template. 中文
A similar, if n... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The present work has several other implications. Perhaps the most apparent is that a single proto-oncogene can be activated by different molecular processes. The c-Ha-ras1 oncogene of the rat became activated via its affiliation with retrovirus sequences, forming the chimaeric Harvey sarcoma virus21,25. As demonstrated... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | small portion of which has been studied experimentally. 中文
Second, we have suggested that the precursor of the EJ oncogene, now identified as c-Ha-ras1, represents a preferred target for activation during bladder carcinogenesis18. It seems unlikely that the bladder urothelium was the site of acquisition of the ras gene... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Hopkins, N., Besmer, P., DeLeo, A. B. & Law, L. W. Proc. Natl. Acad. Sci. U.S.A. 78, 7555-7559 (1981).
Lane, M. A., Sainten, A. & Cooper, G. M. Proc. Natl. Acad. Sci. U.S.A. 78, 5185-5189 (1981).
Murray, M. J. et al. Cell 25, 355-361 (1981).
Krontiris, T. G. & Cooper, G. M. Proc. Natl. Acad. Sci. U.S.A. 78, 1181-1184 (... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Rapp, V. R., Nowinski, R. C., Reznikoff, C. A. & Heidelberger, C. Virology 65, 329-409 (1975).
Giard, D. J. et al. J. Natl. Cancer Inst. 51, 1417-1421 (1973).
Leibovitz, A. et al. Cancer Res. 36, 4562-4569 (1976).
Collins, E. J., Gallo, R. C. & Gallagher, R. E. Nature 270, 347-349 (1977).
Schubert, D. et al. Nature 249... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
表1. 癌基因探针
* 王和巴尔的摩,论文撰写中;† 范德伍德,个人交流;‡ v-表示病毒基因,c-表示细胞基因。
英文
我们使用每个逆转录病毒相关onc基因探针在众多转染子中逐个搜索新的交叉反应片段。比如,图1显示了用v-abl探针进行的分析:泳道a表示用v-abl探针在未转染的小鼠成纤维细胞NIH 3T3细胞DNA中检测到的内源性小鼠序列。这些28 kb、10 kb、6 kb的背景条带在所有的转染子DNA中都能找到(图1,泳道b、d~g和i)。图1c为使用v-abl探针对人类同源基因的检测结果;泳道d~g为四种不同的人类癌基因转染的小鼠细胞DNA的分析结果。结果显示这些DNA仅含有未转染的对照小鼠中含有的DNA片段(泳... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 而未转染的小鼠细胞DNA(图3A,泳道a)不存在任何新片段。由于在转染过程中发生了重排,不同转染子的DNA在被BamHI消化以后得到了大小不同的新片段。我们注意到T24人膀胱癌癌基因与EJ膀胱癌癌基因高度相关[18,19]。图3A,泳道m显示了一个含有T24癌基因的小鼠转染子DNA中也含有能与探针反应的新片段。 英文
图3. 用c-Ha-rasl和EJ癌基因探针分析EJ和T24转染子的DNA。DNA用核酸内切酶BamHI (A,C)或者EcoRI (B,D)酶切,并用图1注所述的方法进行分析。A和B所示的滤膜与5×106 c.p.m.的c-Ha-ras1 DNA探针(2×108 c.p.m. μg–1)温育并曝光进行放射自显影16... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 图4的左右泳道的比较证实了病毒探针及c-Ha-ras1与EJ癌基因DNA的同一片段发生了交叉杂交反应。SacI+KpnI或SacI+XbaI的双酶切结果(图4g,i)显示,v-Ha-ras同源片段跨过了图4上方所示的KpnI和XbaI酶切位点。c-Ha-ras1探针的反应活性主要位于上述酶切反应形成的两个片段中较大的那个(图4c,e)。推断出的EJ癌基因与v-Ha-ras及c-Ha-ras1探针之间的序列比对结果显示在图4的上方。从本研究以及先前的数据[16,17]推断出的转录方向在图谱上是从右到左的。 英文
图4. EJ癌基因物理图谱及c-Ha-ras l和v-Ha-ras (BS-9)的比对。用多种限制性内切酶对EJ-Char... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 我们认为这不太可能,因为使用的大鼠c-Ha-ras1探针的放射性比活度比人类EJ探针高出三倍,但是在放射自显影图像上其信号强度却低3~4倍(图5)。这可能反映了大鼠探针对EJ转染子中存在的人类转录物的亲和力相对较低。因此,我们得出结论:这两个探针都检测到的RNA大部分(即便不是全部)是由人类EJ癌基因模板转录出来的。 英文
研究c-Ha-ras1基因及RNA的同行们也发现了类似的(即便不是相同的)一对转录物[22]。因为EJ以及c-Ha-ras1同源的5.1 kb的转录单元均位于6.6 kb的BamHI片段内部,所以我们认为这两个基因就是同一个基因,而不是相邻的两个基因。与这种结构同源性一致的是其功能的相似性,即二者都能诱导成纤维细... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(毛晨晖 翻译;彭小忠 审稿)
Neurone Differentiation in Cell Lineage Mutants of Caenorhabditis elegans
J. G. White et al.
Editor’s Note
The use of the nematode worm Caenorhabditis elegans for studying gene function and development was pioneered by John Sulston. The British biologist developed techniques to study the cell divisi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | dominance of one cell type over another in what is essentially a fused cell, and/or it may reveal the state of commitment of the precursor in wild-type animals. 中文
WE have studied two very similar mutants unc-59 (e1005) and unc-85 (e1414), both of which are variably blocked in some of the later divisions of the lineage... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | P9–P12 lineages, cells lineally equivalent to VC neurones undergo programmed cell death (X), as do cells lineally equivalent to VB neurones derived from P11–P12. Alternative fates are seen for some of the cells derived from the two precursors at the ends of the cord (P1,P12): P1 produces an AVF interneurone instead of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | shown. The horizontal axis is equivalent to the longitudinal axis of the animal (anterior is drawn to the left); the vertical axis has been used simply to separate the neurones into their respective classes. VA neurones , which have anteriorly directed axons, form a regular sequence of regions of motor activity with li... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The post-embryonic development of ventral cord cells was observed in several unc-59 and unc-85 animals. In these mutants, P-cell-derived neuroblasts produced fewer progeny cells than normal (Fig. 1), because some cell divisions failed. The set of affected cells varied between animals. Failures resulted in polyploid cel... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | † The cells lineally equivalent to VC in the P1–P2 and P9–P12 lineages and to VB in the P11–P12 lineages normally undergo programmed cell death1.
‡ Axons failed to grow out of these cells although they had the synaptic contacts characteristic of the cell types indicated.
中文
Table 2. Number of synapses formed by block... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The observation that characteristics of some cell types were expressed normally in the blocked cells implies that the normal complement of wild-type cell divisions is not a necessary prerequisite for the differentiation of these cell types; however, some other cell cycle event (such as DNA replication15) may be require... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | the daughters reiterates the characteristic divisions of the mother in a stem cell manner13, indicating that it has the same state of commitment as its mother cell. These two interpretations are not necessarily incompatible if cells may only express one state of commitment at any time because of an intrinsic mutual exc... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 约翰·萨尔斯顿开创了利用秀丽隐杆线虫来研究基因功能和发育的先河。这位英国生物学家探索出了一套方法来研究动物个体通过细胞分裂实现从受精卵到成体这一转化过程,并得出了每条线虫都经历相同的细胞分裂和分化程序的结论。在本文中,萨尔斯顿和他的同事们描述了两种细胞分裂在特定步骤被阻断的秀丽隐杆线虫的突变体。他们揭示了在这两种突变体中,细胞分裂阻断的细胞仅产生一个子细胞——正常情况下会产生两个子细胞,并且细胞分裂阻断的细胞往往成为神经元。这项研究为阐明细胞命运的调控过程开辟了道路。后来,萨尔斯顿、他的共同作者罗伯特·霍维茨以及线虫研究者西德尼·布伦纳凭借他们在秀丽隐杆线虫方面的工作共享了诺贝尔奖。 英文
秀丽隐杆线虫通过一种基本上程序不变的细胞分... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 图中显示了细胞在腹侧索内延伸的范围和细胞胞体(–●–)、神经肌肉接头(NMJs)(▲▲▲)、神经连合(|→)和突触传入(|←)的位置。水平轴相当于动物的纵轴(头端在左侧);垂直轴用来将神经元划分到它们各自的类型中。VA神经元向前延伸出轴突,形成常规顺序的运动活性区域,它们在相邻的同类细胞间几乎没有重叠。VB神经元也是如此,但是轴突延伸方向朝后。VA神经元通过与轴突相反方向的细胞胞体延伸出来的树突区域接受突触传入信息;VB神经元主要通过细胞胞体接受突触传入。AS运动神经元的轴突通过神经连合延伸至背侧索,支配背部的肌肉。它们在腹侧索有短的树突区域。VD神经元的轴突以间隙连接的方式突然地中止于邻近VD神经元的轴突末端。背侧索的树突区域也是... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 但是,其他的细胞周期事件(比如DNA复制[15])可能是必需的。药物处理[9,10]或者在lin-5突变体中(文献7),细胞分裂在较早时期已经阻断的母细胞是会体现其正常子细胞特征的,但这些情况下往往是多种细胞类型的特征同时出现在同一个多倍体细胞中。这一现象可能是这些超大的,染色体倍数特别多的细胞中的局部分化或者调节元件的过度稀释造成的。细胞分裂被部分阻断的突变体的分离和鉴定可能有助于区分这两种可能性。 英文
(这两种)突变体中并非所有的晚期细胞分裂都不能进行,那些没有被阻断的细胞同样能够产生正常的细胞。这个发现表明:分裂受阻的前体细胞不能出现某些特定细胞类型的分化特性,不仅仅简单地反映了突变体不能产生这些细胞类型,而且暗示分裂失败可... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | of properties suggested that 4C21.53 was either an undetected pulsar or a member of some new class of objects. This puzzle may be resolved by the discovery and related observations of a fast pulsar, 1937+214, with a period of 1.558 ms in the constellation Vulpecula only a few degrees from the direction to the original ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | After the 1979 pulsar searches, Erickson (personal communication) located a steep-spectrum compact source, 4C21.53E, east of the 4C position by one 4C interferometer lobe (+31.6 s). This observation provided evidence against the superposition hypothesis. Furthermore, Very Large Array (VLA) observations at 5 GHz by one ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 1. Image of extended (north) and compact (south, +) components of 4C21.53W from a 12-h synthesis with the WSRT at 608.5 MHz on 15 January 1982. The synthesized beamwidth shown at the lower left is 31.3×80.4 arc s in RA and Dec, respectively.
中文
Fig. 2. Image of extended (north) and compact (south) components of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Interest in further pulsar searches was rekindled following the discovery of a steep-spectrum component in 4C21.53W at decametric wavelengths4. Momentum for the search increased when the 609-MHz WSRT map was available. A pulsar search sensitive to periods >4 ms was carried out by Boriakoss (personal communication) at t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 3. Interstellar scintillation observation of compact component in 4C21.53W from Arecibo observations on 6 November 1982. Individual spectra were obtained for two polarizations in two 10-MHz bands every 30 s using a 252-channel, 1-bit autocorrelator. Spectra from the two polarization channels were summed and smooth... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | to determine the period derivative at the Arecibo Observatory. A previous estimate of the period derivative8, based on a comparison of measured periods in September and November, has not been substantiated by timing data in November. We suspect that the September measurement was corrupted by sampling errors. Analysis o... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | and gravitational quadrupole radiation are strong functions of the rotation rate, Ω4 and Ω6, respectively9. The minimum energy loss for this pulsar will be the observed radio emission which amounts to 3×1030 erg s–1 assuming a beam solid angle of 1 sr. 中文
The age of this pulsar is puzzling. The maximum spin rate for a ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Two factors lead us to suggest that the pulsar and the H II region are related: (1) The two objects are in the same area of sky in a region of relatively low radio confusion. (2) The brightest part of the H II region and the pulsar are displaced to opposite sides of the near circular, low-level contours of the H II reg... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Rickard, J. J. & Cronyn, W. Astrophys. J. 228, 755 (1979).
Hewish, A. & Okoye, S. E. Nature 207, 55 (1965).
Erickson, W. C., Bull. Am. Astr. Soc. 12, 799 (1980).
Slee, O. B., Austr. J. Phys. Suppl. 36, 1 (1977).
Altenhoff, W. J., Downes, D., Goad, L., Maxwell, A. & Rinehart, R. Astr. Astrophys. Suppl. 1, 419 (1979).
Er... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
1982年1月,韦斯特博克综合孔径射电望远镜(WSRT)在609 MHz对4C21.53W的观测证实了根据80 MHz卡尔哥拉的测量(参考文献5)和5,000 MHz波恩的测量(参考文献6)所推测的位置偏差(图1)。我们怀疑卡尔哥拉测量的位置由陡谱成分主导,波恩测量的位置由延展平谱成分主导。图1中4C21.53W分裂成为两个源,这证实了我们的想法。南边和北边的成分分别被命名为4C21.53W(com)或1937+214和4C21.53W(ext)或1937+215。VLA的短期观测确认了1937+214的位置和陡谱。WSRT于1982年8月在1,415 MHz对4C21.53W进行12小时观测后的合成图清晰地分辨出致密和延展源... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 当阿雷西博望远镜对准ISS调制模式(图3)的峰值处时,在1,400 MHz和430 MHz利用快速信号平均器对几百个脉冲积分就可以稳定地探测到脉冲。这两个波段的波形是相似的。 英文
图4. 信号平均示波器显示的毫秒脉冲星波形。取样间隔是9 μs。包含约6个周期,共9,216 μs。积分持续约75 s。波形包含分开接近180°旋转相位的一个主脉冲和一个间脉冲。脉冲宽度主要来源于信号平均器的测时误差和20 μs的RC时间常数。
英文
首次观测得到如下参数:赤经(1950.0)19时37分28.72秒,赤纬(1950.0)21° 28′01.3′′,太阳系质心系周期0.001 557 807 s(儒略日(JD)244 5282),色... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
我们对阿雷西博天文台员工的支持以及与我们同事许多令人兴奋的讨论表示感谢。本研究由国家科学基金和荷兰射电天文学基金会资助。阿雷西博天文台隶属于国家科学基金资助、康奈尔大学管理的国家天文与电离层研究中心。 英文
(肖莉 周旻辰 翻译;徐仁新 审稿)
Evidence on Human Origins from Haemoglobins of African Apes
M. Goodman et al.
Editor’s Note
Fossil evidence for human antiquity was tempered in the 1970s by comparison of protein sequences, whi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | haemoglobins9,10. To help rectify this situation we report here the rigorously determined α- and β-haemoglobin amino acid sequences not only of chimpanzee (Pan troglodytes) and Gorilla gorilla but also pygmy chimpanzee (Pan paniscus). Our findings favour the explanation of decelerated evolution and point to selection p... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Table 1. Comparison of “clock” dates from different sets of molecular data
Times for the Theria (Metatheria–Eutheria) and Eutheria ancestral nodes for albumin immunological distances are from Sarich and Cronin6 as described in the text of their article; the other divergence times from albumin and transferrin immunologi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 2. a, Amino acid analysis of most important peptides for sequencing pygmy chimpanzee haemoglobin. Tp Arg, tryptical peptides after blocking lysine side chains. Pro Pep., C-terminal peptide after hydrophilic splitting of Asp–Pro bond28. The separation of most peptides was performed by HPLC chromatography. Separatio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | chains as compared with glutamic acid at this position in human, chimpanzee and pygmy chimpanzee chains. Amino acid sequences of γ-haemoglobin chains also point to a Homo–Pan clade distinct from gorilla. There are two non-allelic chains in the hominines, Gγ characterized by glycine at position 136 and Aγ with alanine a... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (that is, 6 NR%), in contrast to much faster rates averaging about 29 NR% for β-haemoglobin sequences and 25 NR% for α-sequences during eutherian phylogeny5. 中文
To highlight the slowness of haemoglobin evolution during the hominine radiation, we can compare hominine with equine rates, taking advantage of the fact that ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | humans suggests that organismal evolution in our earlier ancestors may have depended on amino acid sequence changes in proteins as well as regulatory changes in gene expression. 中文
We thank Drs A. Spiegel, R. Faust and H. Wiesner for the pygmy chimpanzee, chimpanzee and gorilla blood samples, also Dr Gerard Joswiak and... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Goodman, M., Olson, C. B., Beeber, J. E. & Czelusniak, J. Acta Zool. Fenn. 169, 19-35 (1982).
DeJong, W. W. Biochim. Biophys. Acta 251, 217-226 (1971).
Scott, A. F. et al. Am. J. Hum. Genet. 34, 193A (1982).
Mahoney, W. C. & Nute, P. E. Biochemistry 19, 4436-4442 (1980).
Hoyer, B. H., Van de Velde, N. W., Goodman, M. &... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
图1所示为倭黑猩猩的序列,其支持数据在图2中列出。倭黑猩猩的这一序列与黑猩猩和人类都没有区别,与大猩猩只在两个位点有所不同。在位点α23,大猩猩是天冬氨酸,而倭黑猩猩是谷氨酸;β104位点处,大猩猩中是赖氨酸,而倭黑猩猩是精氨酸。当采用最大简约法使用这些序列和其他已知血红蛋白序列一起重建系统发育时,就可以得到相关证据证明在进化关系上黑猩猩属和大猩猩属跟人属聚在人亚科的进化支下,而不是同猩猩属聚在猩猩亚科中。这两个亚科是姊妹群(图3a)。发生在β87(赖氨酸→苏氨酸)和β125(谷氨酸→脯氨酸)两个位点的替换将黑猩猩属、人属和大猩猩属归属到人亚科中。如果考虑到所有相关的氨基酸序列信息,将非洲猿类—人类分支与猩猩所在的分支打断至少... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 在加上大猩猩之前,如果想通过α–血红蛋白序列先将黑猩猩和人类进行聚类,那么需要减少一个NR(图3a)。这是因为处于人类、黑猩猩和倭黑猩猩这一进化链中的α23位点都是谷氨酸,与之相比,处于新大陆的猴、长臂猿、猩猩和大猩猩这一进化链中的相应位点却是天冬氨酸。γ–血红蛋白链的氨基酸序列也表明人属–黑猩猩属进化支与大猩猩不同。人亚科的γ–血红蛋白有两条非等位链,这两条链的特征为:Gγ在位点136处为甘氨酸,Aγ的该位点为丙氨酸。从氨基酸组成数据得出黑猩猩的这两段序列与人类的相一致[17]。相比之下,大猩猩的Aγ(从大猩猩的γ–血红蛋白基因的核苷酸序列推导出来的)[18]在位点104处是精氨酸,而人类和黑猩猩的Aγ链的该位点是赖氨酸。旧大陆猴... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(刘皓芳 翻译;冯兴无 审稿)
Constraints on Evolution of Earth’s Mantle from Rare Gas Systematics
C. J. Allègre et al.
Editor’s Note
The motions of tectonic plates are driven by convective circulation of hot sluggish rock in the Earth’s mantle. But geophysicists have long debated whether the circulating cells reach all the way ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | favours whole-mantle convection. 中文
Measurements of isotope ratios in mantle-derived basalts have shown that the mantle is heterogeneous. Based on Sr and Nd isotopic information alone, early studies showed that distinction could be made between a depleted mantle source (that is, the source of mid-ocean ridge basalts (M... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We now report new noble gas measurements on oceanic basalt glasses, and illustrate the importance of these data to the above arguments. Although in recent years several noble gas studies have been carried out on mantle derived rocks (see refs 12, 15–21) this information has not received the attention that it deserves. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | A recent study of xenon isotopes in MORB glasses17 documented a large anomaly in 129Xe/130Xe ratio with respect to the atmosphere. Due to the short half life of extinct 129I, this result clearly shows that the separation between the MORB mantle source and the atmosphere occurred 4,400 Myr ago. While this conclusion req... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | most undegassed mantle. Although helium isotope ratios are often reported as 3He/4He, we tabulate them here as 4He/3He to conform with the convention for other radiogenic isotope systems (that is radiogenic isotope/stable isotope). 中文
The strategy employed in this study was to use the helium isotopes to identify sample... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | All samples have been degassed in several temperature steps. Errors are 2σ. Absolute concentrations are uncertain to ±10%. The sensitivity for He of 2.7×10–11 cm3 mV–1 is calculated by comparison with samples ALV 892-2 and AII 96-18-1 measured by Kurz32 and differs from the value used previously17.
中文
The results pres... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 1 a, 129Xe/130Xe versus 40Ar/36Ar for the oceanic basalt glass data given in Tables 1 and 2. For sample ALV 979 R7 no xenon data were measured. Sample CYP 78-09-15 is not reported because of possible atmospheric contamination. b, 4He/3He versus 40Ar/36Ar for the same samples as in a. Note that the points retain th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | early outgassing17,18. 中文
The results for the Loihi seamount and Hualalai samples require an alternative explanation. Based on the Xe–Ar correlation, the Ar–Sr correlation, the helium isotopic results12,29, and our experimental precautions, we can immediately eliminate surficial contamination processes. We are therefor... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | This has quite important implications for models of mantle structure and evolution. As mentioned earlier, the short half life of extinct 129I (parent of 129Xe) means that any differences in 129Xe/130Xe ratio within the mantle must be at least 4,400 Myr old. Using the 129Xe/130Xe isotopic differences between MORB and th... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | variations, as is shown by the correlation between 40Ar/36Ar and 87Sr/86Sr in Fig. 2. The systematics suggest that the mantle source for MORB is both depleted with respect to Rb/Sr and degassed with respect to noble gases, which is also consistent with a layered mantle. Even though degassing and continent formation may... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Table 2. Xenon isotopic data normalized to 130Xe≡100
中文
Conclusions
The isotopic composition of He, Ar, and Xe in several basalt glasses, from both mid-ocean ridges and the island of Hawaii, require the existence of both a degassed and an undegassed mantle reservoir. The isotopic variations of Ar and Xe, combined wit... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Lupton, J. G. & Craig, H. Earth Planet. Sci. Lett. 26, 133 (1975).
Kurz, M. D. & Jenkins, W. J. Earth Planet. Sci. Lett. 53, 41-54 (1981).
Staudacher, Th. & Allègre, C. J. Earth Planet. Sci. Lett. 60, 389-406 (1982).
Sarda, Ph., Staudacher, Th. & Allègre, C. J. EOS 63, 458 (1982).
Tolstikhin, I. N. in Terrestrial Rare ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 阿莱格尔等
编者按
地幔中炽热且运动缓慢的岩石发生对流,从而驱动板块构造运动。关于对流循环单元是否都是从底部直到顶部贯穿整个地幔,还是对流运动只独立发生在以660~700 km为边界划分的两个不同层位,即上、下地幔中,地球物理学家们为此争论良久。法国地球化学家克洛德·阿莱格尔和他的同事在此文中为两层对流运动理论(本质上跟现在的理论一致)提供了证据。他们在某些火山岩里发现了浓度相对较高的稀有气体,表明这些稀有气体必定来自于一个大的地幔库,且并未在“去气”过程中丢失这些挥发性组分,从而很大程度上保持了与外界的隔离。其后,阿莱格尔曾成为法国一位颇有争议的教育部部长。 英文
对来自洋中脊和夏威夷岛的一组玄武岩玻璃中He、Ar和Xe的同位素组... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 虽然,这个结论几乎不需要假设,但目前的数据还无法用来评估整个地幔的氙同位素特征,因为洋中脊玄武岩地幔只是整个地幔的一部分。起初我们将洋中脊玄武岩玻璃样品组中的变化解释为大气污染[17]。不过这也存在另一种解释,即相当部分的地幔中的氙与大气氙具有相同的同位素组成。实验人员所面临的挑战是如何来区分这两种可能性。 英文
氩同位素中也存在类似情况。对于火成岩,本文采用了前人报道的40Ar/36Ar同位素比值,大概在295.5(大气中的比值)和16,000之间(参考文献25~27)。参考文献18解释了洋中脊玄武岩中40Ar/36Ar比值相对于去气模型的重要性。对低40Ar/36Ar比值解释的争论由来已久[28,29];现今较为一致的观点是:低... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 而大气污染也无法解释40Ar/36Ar和87Sr/86Sr之间显著的负相关关系(图2)。 英文
图1. a,根据表1和表2中所列大洋玄武岩玻璃相关数据画出的129Xe/130Xe相对于40Ar/36Ar的变化曲线。样品ALV 979 R7的氙同位素数据未予测定。样品CYP 78-09-15的数据并未给出,因为其中可能存在大气污染。b, 4He/3He相对于40Ar/36Ar的变化曲线,所用样品与图a相同。特别要注意数据点在两图中相对位置保持不变。r在图a和b中分别代表(130Xe/36Ar)LOIHI/(130Xe/36Ar)MORB和(3He/36Ar)LOIHI/(3He/36Ar)MORB。它表征了该混合双曲线的曲率(见参考... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 该结论是迄今支持层状地幔最有力的证据之一。考虑到对流的均匀混合效应(见参考文献37),在地质历史上整个地幔的对流将导致氙同位素中的不均一性被破坏,因而这种说法是站不住脚的。对于氩同位素也可得到类似结论,只是由于40K的半衰期较长,且再循环作用对氩的影响更大[18],所以其平均年龄要略高些。 英文
值得注意的是,去气作用与亏损之间(应用时通常指Rb/Sr和Sm/Nd)的关系未必是简单的。虽然稀有气体显示两地幔层(洋中脊玄武岩地幔源区和夏威夷玄武岩地幔源区)与大气的分离发生在至少44亿年前,但Sr和Nd同位素的变化是由于大陆的提取所致,该过程是在随后以不同的速率进行的[7,38]。在现今(近期)地幔混合产生的同位素比值变化范围内,稀有气... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | embodied in the adult. In 1984 Walter Gehring and his colleagues at the University of Basel in Switzerland found a way of identifying the genes in the fruitfly Drosophila that are responsible for the succession of changes. The homoeotic genes, as they are called, are localized on the third chromosome of the fruitfly an... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | structures normally located in a more anterior position. Embryos having a deletion of the entire bithorax complex show a transformation of all the posterior body segments into reiterated segments with structures of the second thoracic segment. Based on the above results and others, Lewis has proposed a model in which s... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Dipterans, with highly diverse segmental structures, might be achieved by duplication and divergence of ancestral genes. According to this model, null mutations in the present set of bithorax complex genes could result in a fly having a more primitive segmental array, that is, with legs on the abdominal segments, or wi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | hybridization conditions we detected many genomic fragments homologous to 903 that gave very strong signals, and many (>50) that were relatively weak. The weak signals were more prominent on the blot hybridized in reduced-stringency conditions (data not shown). A stringent wash of both blots (see Fig. 1 legend) removed... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Methods: Reduced-stringency hybridizations were done as follows. Southern blots31 were prehybridized in 5×SSC, 0.1% bovine serum albumin, 0.1% Ficoll, 0.1% polyvinylpyrollidone, 250 μg ml–1 sonicated, boiled herring sperm DNA, 50 mM NaPO4 pH 7, 0.1% SDS, 43% deionized formamide at 37°C for 2-3 h. The prehybridization b... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | segment primordial. A 0.9-kb XhoI/EcoRI fragment (probe 6), containing a 3′ portion of the ftz transcription unit (A.K., unpublished results), was used as a probe of another Southern blot identical to those used for the five 903 fragments (Fig. 1). In addition to the strong signal contributed by the homologous genomic ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 2. Localization of the H repeat in clones from the Ultrabithorax (Ubx), Antennapedia (Antp) and fushi tarazu (ftz) genes. The overlapping region from the Ubx locus between λ clones 2288 and 2296 (gifts from. P. Spierer) is shown at the top, as well as the BamHI fragment common to both which hybridizes to fragments... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 10 times less intensity to the 3.4-kb and 7.5-kb genomic fragments in the same lane, which carry the ftz and Ubx H repeats respectively. 中文
The cloned regions in Fig. 2 are shown with the same 3R chromosomal orientation: the centromere is to the left, and the telomere to the right. The transcriptional direction of the ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (3) Hybridization of subclones containing the H repeat to Drosophila embryonic tissue sections, to determine whether the transcripts homologous to the subcloned regions were distributed in a segmentally restricted manner, as has been shown for transcripts derived from the homoeotic loci Antp and Ubx16,18,19. 中文
Genomic... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The H repeat lies on a 4.5-kb BamHI/EcoRI fragment for clone 93; this fragment was subcloned into plasmid vector pAT153 and is designated p93. The p93 insert is a single-copy sequence in the Drosophila genome, when tested by genomic Southern blot analysis in stringent hybridization and wash criteria, and derives from t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | (personal communication) and M.S.L. 中文
Fig. 3. In situ hybridization of H repeat clones p93 and p99 to polytene chromosomes. Clones p93 and p99 were nick-translated with biotinylated nucleotide, and hybridized to squashes of Ore-R chromosomes: p93 to a, and p99 to b. The hybridized probes were detected by an immunoper... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Clone 93 is homologous to multiple RNA species during embryonic stages, especially in embryos 6-12 h old (Fig. 4). The largest RNA (5.4 kb) homologous to p93 at the 6-12-h stage is also abundant in late third instar larvae, just before pupation. Clone p99 is homologous to an RNA species of 2.8 kb which is most abundant... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | function of these genes is believed to be required for proper development. Therefore, if the 93 and 99 clones represent other homoeotic selector loci, their transcripts should be restricted during embryonic stages to segments where 93 or 99 expression is required for proper development. 中文
Figure 5 shows that the trans... | 400套付费套装书 |
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