Date: Mon, 9 Mar 2026 18:34:30 +0000
Dear AMMRL Members,
In addition to the expected COSY cross‑peak, I’m observing
several additional signals associated with glucose C4 in the 13C dimension.
These peaks appear consistently and do not resemble common artifacts, so I
am interested in what underlying mechanisms might generate them.
If anyone has encountered similar features or has suggestions on possible
origins, I would greatly appreciate your insights.
Best regards,
Weixing
[cid:image004.png_at_01DCAFC7.517EF620]
> From: main_at_ammrl.groups.io On Behalf Of Zhang, Weixing via groups.io
> Sent: Tuesday, March 3, 2026 8:50 PM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] : Puzzle of glucose HSQC
Dear Clemens and Ivan,
Thank you for your explanation regarding the extra peaks and the glucose spectra.
In TopSpin, I used SR = 0 to set the chemical shift in my spectrum, which
is not referenced to TSP or DSS.
The alpha C6 also shows an additional peak, which I believe is similarly related
to the alpha C5 proton, but this extra peak is absent in C6-deuterated glucose.
Best regards,
Weixing
[cid:image005.png_at_01DCAFC7.517EF620]
> From: main_at_ammrl.groups.io On Behalf Of Vuckovic, Ivan, Ph.D. via groups.io
> Sent: Tuesday, March 3, 2026 6:59 PM
> To: main_at_ammrl.groups.io<mailto:main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] : Puzzle of glucose HSQC
Hi Weixing,
I agree with Clemens — those are indeed HSQC-COSY artifacts, and the
additional peaks correspond to correlations of C-3 and C-5 with proton H-4.
However, the chemical shifts of H-3 and H-5 in your spectrum differ noticeably
from the literature values (HMDB and BMRB). What are your experimental conditions
(solvent, pH, temperature), and what reference you used for chemical shift calibration?
Your resolution in the F1 dimension is remarkable — the HSQC correlation
peaks of C-3 and C-5 are clearly resolved, which is not the case in database spectra.
For reference, I am attaching a full assignment of glucose HSQC spectra, along
with additional examples of HSQC-COSY artifacts.
Best regards,
iv
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