von Dr. Tiziana Masullo
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| [1.] Tim/Fragment 012 01 - Diskussion Zuletzt bearbeitet: 2014-10-25 06:42:18 Hindemith | BauernOpfer, Fragment, Gesichtet, Nienhaus 2006, SMWFragment, Schutzlevel sysop, Tim |
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| Untersuchte Arbeit: Seite: 12, Zeilen: 1-2, 3-15 |
Quelle: Nienhaus 2006 Seite(n): 4213, 4215, 4216, Zeilen: 4213: r.col: 17 ff.; 4215: r.col.: 8 ff.; 4216: l.col. 1 ff. |
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| [At pH ˃ 10, a red-]shifted [sic] emerged, with absorbance and emission peaks displaced by 18 and 10 nm to the red, respectively. At pH ˂ 4 and pH ˃ 12 the protein was thermodynamically unstable.
[...] In analogy to wild-type AvGFP, the AsGFP499 protein showed two bands in the UV/visible spectrum over a wide pH range. Although initially debated (Voityuk et al., 1998), there is now general agreement that the A and B bands are associated with the neutral and anionic states of chromophore (Tsien, 1998). In AsGFP499, the two bands were similar in area in the entire pH range in which the protein was stable; and remarkably, the protonated form of the chromophore became more dominant with increasing pH. In the structure of AsGFP499, amino acid Glu212 is shown to be hydrogen bonded to the chromophore heterocycle and not connected to the phenolic oxygen at all. Therefore, proton transfer between the chromophore and Glu212 cannot take place. In addition to hydrogen bonds to two water molecules, the Tyr64 phenol oxygen is connected to the Ser143 hydroxyl via a short hydrogen bond, which in turn is hydrogen bonded to Asp158. |
At pH . 10, a red-shifted form emerges, with absorbance and emission peaks displaced by 18 and 10 nm to the red, respectively (Fig. 2 D).
[page 4215] In analogy to wild-type avGFP, the asFP499 protein shows two bands in the UV/visible spectrum over a wide pH range (Fig. 4). Although initially debated (51,52), there is now general agreement that the A and B bands are associated with the neutral and anionic states of chromophore (9). [...] [...] In asFP499, the two bands are similar in area in the entire pH range in which the protein is stable (Fig. 4); and remarkably, the protonated form of the chromophore becomes more dominant with increasing pH. In the structure of asFP499, amino acid Glu212 (corresponding to Glu222 in avGFP) is shown to be hydrogen bonded to the chromophore heterocycle and not connected to the phenolic oxygen at all. Therefore, proton transfer between the chromophore and Glu212 cannot take place. However, the structure in Fig. 1 C suggests an alternative explanation for the appearance of the two conformations. In addition to hydrogen bonds to two water molecules, the Tyr64 phenol oxygen is connected to the [page 4216] Ser143 hydroxyl via a short hydrogen bond (2.5 A° ), which in turn is hydrogen bonded to Asp158 (2.7 A° ). 9. Tsien, R. Y. 1998. The green fluorescent protein. Annu. Rev. Biochem. 67:509–544. 51. Weber, W., V. Helms, J. A. McCammon, and P. W. Langhoff. 1999. Shedding light on the dark and weakly fluorescent states of green fluorescent proteins. Proc. Natl. Acad. Sci. USA. 96:6177–6182. 52. Voityuk, A. A., M. E. Michel-Beyerle, and N. Ro¨sch. 1998. Quantum chemical modeling of structure and absorption spectra of the chromophore in green fluorescent proteins. Chem. Phys. 231:13–25. |
The source is given on the previous page. The reader may assume that the work of Nienhaus et al. (2006) is described in the first two paragraphs, but not that this is done in the words of Nienhaus et al. (2006). The last documented paragraph however is not written in the descriptive past tense but rather makes factual statements, such that the reader has no way of knowing that he is reading the words of Nienhaus et al. (2006). |
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Letzte Bearbeitung dieser Seite: durch Benutzer:Hindemith, Zeitstempel: 20141025064242