Unexpected Raman shift - protein analysis
Hey fellow chemists,
right know I'm facing a problem I can't solve and even the literature doesn't seem to have encountered this problems; hence I'm seeking some of your expertise now.
What have we done:
Raman spectroscopy of soy protein isolate (10 % in water)
Laser: 532 nm
Duration: 10 s, 12 counts
Standardisation of spectrum: via Phenylalanin
The problem: We encounter a unexpected raman shift (compared to literature on Raman spectroscopy performed on either solid or dissolved protein) and can't explain it.
In particular
our disulfid SS conformation peaks are all shifted by roughly -50 cm^(-1) showing up at 450 - 500 cm^(-1)
our Tyrosine and Tryptophane doublet are shifted by roughly -20 cm^(-1) with Trp around 1320cm^(-1) and Tyr around 820 cm^(-1)
We don't suspect any instrumental errors, as a) it was calibrated/ checked recently and b) the Amide peaks show up as expected.
Does anyone here have an idea what could cause the problem and/ or ideas about how to revolve it?
Thanks in advance!
Best,
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