1. Steve Kregel Garand Group-UW Madison 6/17/2014
Glucose Spectroscopy in the Gas Phase with Cryogenic Ion Vibrational Spectroscopy
Steve Kregel
Garand Group-UW Madison
6/17/2014

2. Background and Motivation
Sugar mixtures extracted from glycoproteins are very complex
All hexoses yield the same information via mass spectrometry
Typically separated with HPLC to determine isomeric ratio
Slow
Requires significant molecular modifications
Gas phase spectroscopy could potentially identify isomeric mixtures without separation
Alley, William R. Jr.; Mann, Benjamin F.; Novotny, Milos V.; Chemical Reviews 2013,

3. Instrumental Setup-CIVS
3) Remove untagged ions from TOF path
1) ESI sugar solution with ~1mM NaCl
ISOMER BURNING LASER!
2) Trap ions and attach D2 tag
4) Excite vibrational modes and remove tag
5) Acquire MS of detagged ions

4. Glucose Background Anomeric ratio is 44% α and 56% β in solution phase
Interconverts through ring opening deprotonation mechanism at C1
Requires solvent to interconvert
α and β anomers must be considered distinct species in gas phase
Multiple Na+ binding sites possible - yields a distribution of conformers
Fishman, P.H. and Bailey, J. Martyn. American Journal of Physiology Vol. 226, No.4 April 1974

5. Experimental and Calculated Spectrum of Sodiated Glucose
72% α0 (+0cm-1)
9% α1 (+717cm-1)
9% α2 (+731cm-1)
5% β0 (+370cm-1)
Spectrum possibly saturated
Isomer Burning to deconvolute
Many Conformers present, will be hard to do with multiple sugars
All calculations were done at the cam-B3LYP/6-311+G(d,p) level
5% β1 (+504cm-1)

6. Glucose-6-Phosphate Background
Addition of a phosphate group greatly expands the PES
Anomeric conversion IS possible in gas phase due to the dual acid- base nature of the phosphate group
α and β G6P cannot be considered separately
Naturally charged, requires no Na+ atom to become an ion
Phosphate group can move to lowest energy position before cryogenic trap
Implies that only a single conformer should be present

7. Phosphorylation Simplifies the Spectrum…
Lack of shoulders, fewer peaks

8. … But it’s Still Complicated
α-G6P (+0 cm-1)
β-G6P (+324 cm-1)
Best Match (+1555 cm-1)

9. Conclusions
Gas phase spectroscopy has the potential to identify mixtures of hexoses
Multiple (Na-Glucose)+ conformers complicate the spectrum
Could lead to difficulty in creating a hexose spectral library
G6P is likely not in its low energy conformation

10. Acknowledgements Etienne Garand Brett Marsh Erin Duffy Jon Voss
Jia Zhou