Discerning terminal glycosylation with the naked eye
نویسنده
چکیده
J U N E 1 , 2 0 0 7 / A N A LY T I C A L C H E M I S T R Y 3 9 5 3 Werner Hug and colleagues at the University of Fribourg (Switzerland) have tested the limits of their newly designed Raman optical activity (ROA) spectrometer by determining the absolute configuration of (R)-[H1, H2, H3]-neopentane. This molecule has a very subtle chirality, which is determined solely by substitution of deuterium at three of its five carbons. ROA is akin to CD spectroscopy in that it compares how beams of oppositely polarized light react with a molecule. The difference is that CD measures the absorption of that light, whereas ROA assesses the Raman scattering. Both techniques give information about molecular structure, but an ROA spectrum contains more bands and thus more information about fine structural details, such as stereochemistry. ROA has been used to study proteins from intact viruses, but Hug and coworkers wanted to push the boundary of what was possible with this technology by moving to the other end of the molecular size spectrum. To do this, they synthesized [H1, H2, H3]-neopentane. The researchers first computed ROA spectra for each of the nine potential rotamers for both the (R) and (S) configurations of the molecule. The spectra for each enantiomer were combined to give an average predicted spectrum; it was then compared to the experimental spectrum of their sample. In the end, the molecule was determined to be in the (R) configuration. The authors note that now that the absolute configuration of (R)-[H1, H2, H3]-neopentane has been determined, the stereochemistry of just about any molecule should be accessible by ROA. (Nature 2007, 446, 526–529) Absolute configuration of a barely chiral molecule
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