Effect of cyclodextrins on the physicochemical properties of chlorophyll a in aqueous solution.
The interactions between chlorophyll a and two beta-cyclodextrins, that have the same cavity size but different substituents, were studied in aqueous solutions. These supramolecular host-guest complexes were examined by a combination of UV/vis absorption, circular dichroism, NMR, and steady-state and time-resolved fluorescence measurements. The results indicate that all cyclodextrins solubilize the pigment mainly in monomeric form in water. The pigment forms 1:1 complexes with the heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and 1:2 complexes with the hydroxypropyl-beta-cyclodextrin. In such complexes the methyl groups of the cyclodextrin inner cavity are involved in the interaction with the pigment as evidenced by NMR measurements. We also measured the luminescence of singlet oxygen photosensitized by chlorophyll a in the inclusion complexes.
Dentuto
Pasquale L
PL
Dipartimento di Chimica, Università di Bari, Via Orabona 4, 70126 Bari, Italy.
Catucci
Lucia
L
Cosma
Pinalysa
P
Fini
Paola
P
Agostiano
Angela
A
D'Accolti
Lucia
L
Trevithick-Sutton
Colleen C
CC
Foote
Christopher S
CS
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D002942:Circular Dichroism; D049449:Luminescence; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010100:Oxygen / Q000737:chemistry; D010777:Photochemistry; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry*
D012996:Solutions; D047392:beta-Cyclodextrins; D014867:Water; D002734:Chlorophyll; D010100:Oxygen; D000077194:Chlorophyll A