Interactions of chlorophyll a with synthesized peptide in aqueous solution.
The interactions between chlorophyll a and synthesized peptides have been studied using optical spectroscopy. Three 30-residue peptides are designed and synthesized: an amphiphilic peptide without histidine (L), an amphiphilic peptide with histidine (L/H) and a hydrophilic peptide (K/E). These peptide properties thereby allow us to examine the effect of the peptide hydrophobicity and/or histidine residue on pigment-peptide interactions. On mixing with peptides, chlorophyll a has a main absorption band in the Qy region with the maximum at 672 nm. For all three peptides, fluorescence patterns show that at a low concentration of the peptide (0.05 mM) in aqueous solution, the energy is transferred among various forms of the pigment. Only peptide L/H at high concentration (0.5 mM) in solution retains the Qy band of chlorophyll a at 672 nm, and the emission is that typically seen for the monomeric form of the pigment. The aggregation of chlorophyll a is suppressed most strongly in the presence of the peptides L/H. The results suggest that chlorophyll a is ligated to a histidine residue, located in the hydrophobic region of the peptides L/H, and in surrounded or shielded by the peptide alpha-helixes.
Dudkowiak
A
A
National Institute for Advanced Interdisciplinary Research, AIST/MITI, Ibaraki, Japan.
Nakamura
C
C
Arai
T
T
Miyake
J
J
D000595:Amino Acid Sequence; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D000077194:Chlorophyll A; D002942:Circular Dichroism; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014867:Water
D010455:Peptides; D012996:Solutions; D014867:Water; D002734:Chlorophyll; D000077194:Chlorophyll A