RESUMO
Mutant human serum albumins accelerated the photocyclodimerization of 2-anthracenecarboxylate to afford chiral cyclodimers in 75-85% enantiomeric excesses, revealing that the mutations to impair non-productive sites 1 and/or 2 enhanced the substrate binding to site 3 without seriously damaging its inherently high photochirogenic ability.
Assuntos
Antracenos/metabolismo , Ácidos Carboxílicos/metabolismo , Albumina Sérica/genética , Albumina Sérica/metabolismo , Antracenos/química , Sítios de Ligação , Ácidos Carboxílicos/química , Ciclização , Dimerização , Humanos , Mutação , Processos Fotoquímicos , EstereoisomerismoRESUMO
The mechanism for the high enantiomeric excess (ee) (80-90%) observed in the photocyclodimerization of 2-anthracenecarboxylate (AC) in the chiral binding sites of human serum albumin (HSA) was studied using fluorescence anisotropy. A long rotational correlation time of 36 ns was observed for the excited states of the ACs bound to the HSA site responsible for the high ee, suggesting that the ACs have restricted rotational mobility in this site. The ACs in this site have the same prochiral face protected by the protein, and this protection is responsible for the high ee observed. These insights provide a strategy for the rational design of supramolecular photochirogenic systems.
Assuntos
Antracenos/química , Ácidos Carboxílicos/química , Albumina Sérica/química , Anisotropia , Ciclização , Dimerização , Fluorescência , Humanos , Estrutura Molecular , Processos Fotoquímicos , Estereoisomerismo , Fatores de TempoRESUMO
Cimicifugoside, a triterpenoid isolated from Cimicifuga simplex, which has been used as a traditional Chinese medicine due to its anti-inflammatory, analgesic or anti-pyretic action, was examined for inhibition of nucleoside transport and synergistic potentiation of methotrexate cytotoxicity. Cimicifugoside inhibited uptake of uridine, thymidine and adenosine in human leukemia U937 cells with the low nanomolar IC(50) values, but did not affect that of uracil, leucine or 2-deoxyglucose at