Aromatic side-chain contribution to far-ultraviolet circular dichroism of helical peptides and its effect on measurement of helix propensities

Biochemistry ◽  
1993 ◽  
Vol 32 (21) ◽  
pp. 5560-5565 ◽  
Author(s):  
Avijit Chakrabartty ◽  
Tanja Kortemme ◽  
S. Padmanabhan ◽  
Robert L. Baldwin
Keyword(s):  
Circular Dichroism ◽  
Side Chain ◽  
Aromatic Side Chain ◽  
Helical Peptides ◽  
Far Ultraviolet ◽  
Circular Dichroïsm

scholarly journals A circular-dichroism study of epidermolytic toxins A and B from Staphylococcus aureus

1982 ◽  
Vol 203 (3) ◽  
pp. 775-778 ◽  
Author(s):  
C J Bailey ◽  
S R Martin ◽  
P M Bayley
Keyword(s):  
Staphylococcus Aureus ◽  
Circular Dichroism ◽  
Alpha Helix ◽  
Side Chain ◽  
Initial Increase ◽  
Beta Sheet ◽  
Circular Dichroism Spectra ◽  
Aromatic Side Chain ◽  
Circular Dichroïsm

The far-u.v. circular-dichroism spectra of the two epidermolytic toxins was analysed into fractional contributions of 0.09 helix and 0.46 beta-sheet to each toxin structure. Trifluoroethanol perturbation caused an initial increase in dichroic absorption at 205 nm and then a change characterized as a beta-sheet-to-alpha-helix transition. The intense near-u.v. spectra suggested that the toxins have unusually rigid, though different, aromatic-side-chain arrangements.

scholarly journals The Role of Heme Chirality in the Circular Dichroism of Heme Proteins

2014 ◽  
Vol 69 (7) ◽  
pp. 313-325 ◽  
Author(s):  
Robert W. Woody ◽  
Gennaro Pescitelli
Keyword(s):  
Circular Dichroism ◽  
Density Functional ◽  
Sperm Whale ◽  
Dominant Factor ◽  
Side Chain ◽  
Aromatic Side Chain ◽  
Peptide Backbone ◽  
Rotational Strength ◽  
Torsional Angles ◽  
Circular Dichroïsm

The rotational strength (R) of the Soret transition in sperm-whale myoglobin (SW Mb), the hemoglobin from Chironomus thummi thummi (CTT Hb), and human hemoglobin (hHb) has been calculated using 20 high-resolution (< 1:5 Å) crystal structures. The intrinsic rotational strength due to heme non-planarity was calculated using π-electron theory and time-dependent density functional theory (TDDFT). Calculations on model protoporphyrins with a planar nucleus and with various torsional angles for the 2- and 4-vinyl substituents showed maximum R of ±0.70 Debye-Bohr magneton (1 DBM = 0.9273 · 10-38 cgs units). Viewing the heme so that the 2- and 4-vinyls are in a counterclockwise relationship, if a vinyl points toward the viewer, it contributes positively to R. Calculations of the intrinsic R for explicit heme geometries of SW Mb, CTT Hb, and hHb gave averages of 0.40±0.09, ±0:44±0.04, and +0.32±0.11 DBM, respectively. Coupling of the Soret transition with aromatic side-chain and peptide backbone transitions was also considered. For SW Mb, the magnitudes of the contributions decreased in the order Rint > Raro > Rpep. For CTT Hb and hHB, the orders were, respectively, Rint > Rpep > Raro and Rint > Raro ≈ Rpep. Human Hb ɑ chains showed the same trend as CTT Hb. Only in the hHb β chains did Raro predominate, with the order Raro > Rint > Rpep. The total predicted Rtot for SW Mb, CTT Hb, and hHb averaged +0.77±0.10 (0.56 - 0.80), -0.37±0.12 (-0.5), and +0.31±0.17 DBM (0.23 - 0.50), respectively. (Values in parentheses are experimental values.) Thus, contrary to the currently accepted view, coupling with aromatic side-chain or peptide transitions is not the dominant factor in the Soret circular dichroism (CD) of these proteins. The Soret CD is dominated by intrinsic CD of the heme chromophore, of which vinyl torsion is the major determinant. This result suggests an explanation for the large effect of heme isomerism on the Soret CD of Mb and Hb. Rotation about the ɑ-γ axis may be associated with large changes in vinyl torsion and thus substantially alter the intrinsic CD, even reversing its sign.

Stabilizing Interactions between Aromatic and Basic Side Chains in α-Helical Peptides and Proteins. Tyrosine Effects on Helix Circular Dichroism

2002 ◽  
Vol 124 (43) ◽  
pp. 12706-12714 ◽  
Author(s):  
Charles D. Andrew ◽  
Samita Bhattacharjee ◽  
Nicoleta Kokkoni ◽  
Jonathan D. Hirst ◽  
Gareth R. Jones ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Side Chains ◽  
Helical Peptides ◽  
Circular Dichroïsm
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