Molecule from hell

The first biologically functional chimeric DNA molecules constructed in vitro were assembled from parts of different plasmids in 1973 by Stanley Cohen, Annie Chang, Herbert Boyer, and Robert Helling. These plasmids were used to transform recipient E. coli cells transformation means the uptake and repli-... 

The nature of the final state depends upon the energy, hv, of the exciting photons. In X-ray photoelectron spectroscopy (XPS) the exciting photons are provided by sources such as A1 Ka (1,486 eV) or Mg Ka (1,253 eV) and excitation of the core electrons of the molecules is observed. In UV photoelectron spectroscopy (UPS), Hel (21.2eV) or Hell (40.8 eV) radiation is used and excitation from the valence region of the neutral molecule is observed. XPS and UPS are surface-sensitive techniques, which are capable of providing extremely useful information on the chemical nature of a surface or interface and, in the case of the XPS, the conformational state of the molecules at the surface [64]. 

Figure 5.25 Shapes of spectrometer functions measured for two sectors of a double sector CMA. The individual symbols characterize data points from experiments performed at different kinetic energies between 5.64 eV (Hel light and 3af ionization in the nitrogen molecule) and 28.68 eV (Hell light with 5p ionization in xenon). The individual spectra have been normalized to the same height and fwhm value in order to obtain a common...

The Hell-Volhard-Zelinskii reaction involves formation of an intermediate acid bromide enol, with loss of stereochemical configuration at the chirality center. Bromination of (/ )-2-phenylpropanoic acid can occur from either face of the enol double bond, producing racemic 2-bromo-2-phenylpropanoic acid. If the molecule had a chirality center that didn t take part in enolization (Problem 22.33), the product would be optically active. 

Escape from conformational hell. RNA molecules in general, and ribozymes in particular, are notorious for the formation of multiple conformations, usually one active species and numerous inactive conformers. This makes both the prediction and experimental determination of biologically-relevant three dimensional structures very difficult. We devoted considerable effort to the identification of specific misfolded structures and to redesign of the ribozyme so as to minimize their formation. 

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