On Thu, 25 Oct 2007, Mark Pfuhl wrote:
> Something completely unrelated:
> I occasionally notice that aliased peaks appear out of nowhere (example
> attached). For my example (simple 15N hsqc, no truly aliased peaks) the edge
> of the spectrum is set to 137.037 ppm (coming straight from Topspin) and yet
> I get a peak clearly on the outside, just beyond 138ppm. When I change the
> boundary manually to 137.0 ppm the peak disappears.
> Do others see this one as well?
Often. I guess Wayne can give chapter & verse, but as I understand it
it's a precision/rounding problem. I guess the 137.037 puts you right on
the edge of the spectrum and might be interpreted as just inside or just
outside the spectrum boundary depending on how the two numbers are
represented. Since the region that analysis contours is blocky, you'll
therefore get the next block's worth of contours beyond the edge of the
data file. There was discussion of making it possible to turn the contour
tiling off for people who really hate it, but I can't remember if it ever
happened.
Brian
--
Dr. Brian O. Smith ---------------------- B Smith at bio gla ac uk
Division of Biochemistry & Molecular Biology,
Institute Biomedical & Life Sciences,
Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK.
Tel: 0141 330 5167/6459/3089 Fax: 0141 330 8640
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