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NMR Solution Structure of C-terminally amidated, Full-length Human Galanin
SOLUTION NMR
NMR Experiment
Experiment
Type
Sample Contents
Solvent
Ionic Strength
pH
Pressure
Temperature (K)
Spectrometer
1
1H 1D NMR Spectrum
0.5 mM hGal(1-30)NH2, 4.14 mM [U-2H] sodium acetate, 5.86 mM [U-2H] acetic acid
95% H2O/5% D2O
sample was dissolved in 10 mM sodium acetate-d3/acetic acid-d4 buffer at pH 4.6; no additional additives were present. mM
4.6
1 atm
298
Bruker AVANCE III 600
2
2D 1H-1H COSY
0.5 mM hGal(1-30)NH2, 4.14 mM [U-2H] sodium acetate, 5.86 mM [U-2H] acetic acid
95% H2O/5% D2O
sample was dissolved in 10 mM sodium acetate-d3/acetic acid-d4 buffer at pH 4.6; no additional additives were present. mM
4.6
1 atm
298
Bruker AVANCE III 600
3
2D 1H-1H TOCSY
0.5 mM hGal(1-30)NH2, 4.14 mM [U-2H] sodium acetate, 5.86 mM [U-2H] acetic acid
95% H2O/5% D2O
sample was dissolved in 10 mM sodium acetate-d3/acetic acid-d4 buffer at pH 4.6; no additional additives were present. mM
4.6
1 atm
298
Bruker AVANCE III 600
4
2D 1H-1H ROESY
0.5 mM hGal(1-30)NH2, 4.14 mM [U-2H] sodium acetate, 5.86 mM [U-2H] acetic acid
95% H2O/5% D2O
sample was dissolved in 10 mM sodium acetate-d3/acetic acid-d4 buffer at pH 4.6; no additional additives were present. mM
4.6
1 atm
298
Bruker AVANCE III 600
NMR Spectrometer Information
Spectrometer
Manufacturer
Model
Field Strength
1
Bruker
AVANCE III
600
NMR Refinement
Method
Details
Software
simulated annealing
CNS
NMR Ensemble Information
Conformer Selection Criteria
structures with the lowest energy
Conformers Calculated Total Number
1000
Conformers Submitted Total Number
25
Representative Model
1 (lowest energy)
Additional NMR Experimental Information
Details
The authors state the following regarding the geometric deviations with this ensemble: With most of the hydrogen bonds in the N-terminus of the peptide bifurcated, or even more, they are confident that the ensemble represents the time-averaged structure of a peptide that is rapidly interconverting turns of alpha, 310-, and pi-helix. Their shift assignments were largely unambiguous and can be found in BMRB entry 31032. The "irregular helix restraints" used (and described in the manuscript and its references) were employed to allow the ensemble to sample multiple arrangements during simulated annealing. By definition, this ensemble existing as an average will display a significant degree of geometric irregularity, particularly with regard the backbone and sidechain outliers as compared to statistical norms. Further, the clashscore level is quite high. This appears to be a consequence of the very high density of ROE-derived distance restraints in the N-terminus of the peptide, which were maximally relaxed to account for any uncertainty in their measurement throughout several rounds of validation and re-calculation. Tight sidechain packing and compression seems to be the dictated outcome of our data. Much of their study is concerned with compact hydrophobic packing in this sequence - this full-length peptide is indeed much more rigid across the stretch of residues it shares with fragment peptides described in entries 7S3O, 7S3Q, and 7S3R. Together with the compactness of the region of the sequence, the clashes appear to be a consequence of several averaged, coiling, helical conformers all existing on the NMR timescale. This is discussed at further length in the citation affiliated with this deposition