Differential binding preference of methylpheophorbide a and its diboronated derivatives to albumin and low density lipoproteins.
The tetrapyrrolic macrocycle and the functional groups at its periphery allow for a variety of modifications aimed at multifunctional therapeutic compounds. In particular, conjugation of boron polyhedra yields dual efficacy antitumor photo/ radiosensitizers. Structural optimization of these agents presumes the identification of macromolecules that bind and transport boronated tetrapyrroles. Using spectroscopic methods we demonstrated that methylpheophorbide a forms complexes with serum albumin and low density lipoproteins (LDL) whereas two diboronated derivatives, 13(2),17(3)-[di(o-carboran-1-yl)methoxycarbonyl]pheophorbide a and 13(2),17(3)-[di(1-carba-closo-dodecaboran-1-yl)methoxycarbonyl]pheophorbide a, were capable of binding to LDL but not to albumin. Molecular modeling showed a mode of interaction of methylpheophorbide a with the amino acid residues in the albumin's hemin binding site. In contrast, for diboronated derivatives such interactions are sterically hindered by boron polyhedra, in line with experimentally determined lack of complex formation with albumin. These data strongly suggest that LDL might be the preferred carrier for polycarborane containing methylpheophorbide a derivatives.
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russian Federation. golovinagalina@yandex.ru
Galina V
GV
Golovina
Georgy N
GN
Rychkov
Valentina A
VA
Ol'shevskaya
Andrei V
AV
Zaitsev
Valery N
VN
Kalinin
Vladimir A
VA
Kuzmin
Alexander A
AA
Shtil
D001665:Binding Sites / Q000187:drug effects; D001896:Boron Compounds / Q000737:chemistry / Q000494:pharmacology*; D002734:Chlorophyll / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008077:Lipoproteins, LDL / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D012709:Serum Albumin / Q000737:chemistry*
D001896:Boron Compounds; D008077:Lipoproteins, LDL; D012709:Serum Albumin; D002734:Chlorophyll