Title
Absolute Configuration Determination of Side Chains of Basic Amino Acid Residues Using Water-Soluble Porphyrins-Based Exciton Chirality Method
Author
Shingo Hattori, Kengo Akagawa, Kazuaki Kudo, Kazuyuki Ishii
Year
2016
Journal
The Journal of Physical Chemistry B
Abstract
We demonstrated that the circular dichroism (CD) exciton chirality method based on the supramolecular interactions of meso-tetra(4-sulfonatophenyl)porphyrin (MTPPS4, M = Zn or H2) was applicable for the determination of the absolute configuration between the side chains of two basic amino acid residues of stable monomeric β-hairpin peptides (tryptophan zipper: Trpzip). When MTPPS4 was added to an aqueous solution containing Trpzip, a bisignate CD signal was detected in the Soret band region in addition to a decrease in absorbance. These spectral changes indicated the formation of a supramolecule consisting of Trpzip and MTPPS4 via electrostatic interactions between the positively charged lysine residue of Trpzip and the negatively charged sulfonate group of MTPPS4. On the basis of the Job plots, the supramolecular structure of Trpzip-ZnTPPS4 is ZnP-Tz-ZnP or ZnP-Tz-ZnP-Tz-ZnP, while that of Trpzip-H2TPPS4 is -(-H2P-Tz-)n- (MPs and Tz denote MTPPS4s and Trpzip, respectively). In order to explain the bisignate CD spectra of the supramolecules, a plausible model, i.e., ZnP-Tz-ZnP, was carefully analyzed by the CD exciton chirality method: two orthogonalized electric transition dipole moments of each MTPPS4 and the effects of free rotation of MTPPS4 around the electrostatic bonding axis were considered. The exciton-coupled CD spectral pattern based on ZnTPPS4 reflected the absolute configuration between the side chains of two lysine residues. Our approach can be used to determine the absolute configuration of side chains of other peptides with two basic amino acid residues in the amino acid sequences.
Full Article
Instrument
J-725
Keywords
Circular dichroism, Absolute configuration, Biochemistry