[Demelerlab] updates to the UltraScan SOMO residue definitions

[Mattia Rocco]

Hello Jason,

I have started the coding for your residues, and I have a few questions 
for you.

1-In using the Durchschlag's values (I assume the Prog. Coll. Polym. 
Sci. 1994 paper), did you correct them for 20 °C? Because most are for 
25 °C. I just need to know it, because all values in US-SOMO are at 20 
°C.

2-I had no problems for Ornithine, which is a shorter version of 
Lysine... ;-) But I would need the real name for "Phi 5", and I don't 
see any N-Me Cha in the PDBs that Bo sent me. Is that the "XXX" residue? 
In that case, we need to pick a better three-characters name for it... 
;-)

3-In those PDBs, there is "SAR", so I believe a proper psv should be 
computed also for this residue. If you have glycine, then the "SAR" 
residue should be changed to "GLY". Since US-SOMO somo.residue files are 
then distributed to the community, they should contain properly coded 
residues... ;-)

Best - Mattia

Il 2023-07-10 20:21 Jason Zhu ha scritto:

> Hi Mattia, Emre, and Borries,
> 
> You should be able to use the following values for the non-canonical 
> amino acids in the meantime. I assumed (-H2O) in determining the MW and 
> partial specific volumes for the 2 non-canonical amino acids based on 
> Helmut Durchschlang's papers.
> 
> Ornithine:
> MW (g/mol): 114.2
> Partial Specific Volume (mL/g): 0.7795446
> 
> N-Methyl cyclohexylalanine (N-Me Cha):
> MW (g/mol): 167.3
> Partial Specific Volume (mL/g): 0.90342716
> 
> I would use the N-Me Cha values for Phi 5. For SAR at residue 13, I 
> would use the MW and PSV for glycine instead. The analog that I based 
> my NMR PDB model off of (PDB ID: 5v63) had sarcosine (N-methylglycine) 
> where I have glycine.
> 
> Hope that helps and please let me know if there's anything else you 
> need!
> Jason
> 
> On Mon, Jul 10, 2023 at 9:37 AM Mattia Rocco <mattia.rocco at quipo.it> 
> wrote:
> 
> Hello Bo,
> 
> nice to read from you! I am currently away, I will be back in Genova a 
> week from today, and I'll have a look at this residue coding task. I do 
> not expect it to be difficult, especially if calculations of the psv of 
> the non-coded residues are already available. In the meantime, you and 
> your collaborators can use the approximate method, just enter the 
> correct global psv and MW in the appropriate fields (Emre can point 
> them out to you).
> 
> Take care - Mattia
> 
> Il 2023-07-09 23:52 Borries Demeler ha scritto:
> 
> Hi Mattia and Emre:
> We are working with the Nowick group from UCalifornia, Irvine, to study 
> synthetic amyloid peptide mimics which include several non-canonical 
> amino acids. Loading Xray and NMR generated PDBs into SOMO causes 
> several errors due to these discrepancies:
> 
> Encountered the following warnings with your PDB structure:
> 
> Chain B Molecule 1 Residue ORN 1: Non-coded residue.
> 
> Chain B Molecule 1 Residue PHI 5: Non-coded residue.
> 
> Chain B Molecule 1 Residue ORN 9: Non-coded residue.
> 
> Chain B Molecule 1 Residue SAR 13: Non-coded residue.
> 
> ...and various downstream issues with chain breaks resulting from these 
> unknown residues. I suspect that due to the small size of these 
> peptides we want to be as accurate as possible to represent the 
> residues correctly, since they are likely extending into the solvent 
> interface. Of great interest in amyloid research is the structure & 
> function of small soluble oligomers, so this is what we are trying to 
> investigate by AUC, NMR and X-ray, and being able to simulate expected 
> oligomers by US-SOMO would be a great plus.
> 
> Can you please update the residue definition list for US-SOMO so these 
> AAs are properly recognized? I think this would be a great and novel 
> use of US-SOMO!
> 
> I have attached a number of PDB files from oligomeric structures of one 
> of these peptides derived from NMR and Xray that were generated by 
> Jason Zhu (Cc'ed) from James Nowick's lab, and since I am no expert in 
> PDB formats, perhaps you and Jason can collaborate to get the residues 
> added, and allow us to load them correctly?
> 
> We would be happy to include you in the manuscript author list for your 
> help with the simulation. The s, D and frictional ratios would be 
> directly compared with AUC data. Also, James has already worked out the 
> partial specific volumes for these non-canonical amino acids using 
> Helmut Durchschlag's papers. He can provide you with these values.
> 
> Thanks so much, -Borries
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