RESUMO
A synthetic perfluoroalkyl-tagged lactosyl glycolipid has been shown to form lipid microdomains in fluid phospholipid bilayers. When embedded in the membranes of phospholipid vesicles, this glycolipid was trans-sialylated by soluble T. cruzi trans-sialidase (TcTS) to give a perfluoroalkyl-tagged glycolipid that displayed the ganglioside GM3 epitope, with up to 35% trans-sialylation from fetuin after 18 h. Following sialylation, vesicles bearing this Neu5Ac(α2-3)Gal(ß1-4)Glc sequence in their "glycocalyx" were recognised and agglomerated by the lectin M. amurensis leukoagglutinin. Monitoring TcTS-mediated trans-sialylation by HPLC over the first 6 h revealed that enzymatic transformation of bilayer-embedded substrate was much slower than that of a soluble lactosyl substrate. Furthermore, clustering of the lactose-capped glycolipid into "acceptor" microdomains did not increase the rate of sialic acid transfer from fetuin by soluble TcTS, instead producing slight inhibition.
Assuntos
Glicoproteínas/metabolismo , Lactose/química , Lipídeos/química , Microdomínios da Membrana/química , Neuraminidase/metabolismo , Ácidos Siálicos/química , Trypanosoma cruzi/enzimologia , Sítios de Ligação , Microdomínios da Membrana/enzimologia , Modelos Moleculares , Estrutura MolecularRESUMO
Molecular gels are formed by the self-assembly of low-molecular weight compounds by weak non-covalent interactions and thus, they may be easily disassembled in response to external stimuli. Chemically sensitive gels can be prepared by introducing in the molecular design functional groups that may interact either by covalent or non-covalent forces with other molecules present in the medium. Functional molecular gels have been reported that are sensitive to acids, bases, ions, redox-active compounds, neutral species, reactive compounds and enzymes. Here we present a broad revision of the different chemical inputs that can be used to tune gel properties through some appealing application-based selected examples.
RESUMO
The free energy of complexation of supramolecular complexes containing phenol-carbamate H-bonds is an additive function of the number of H-bonds, with a constant increment of 6 kJ mol(-1) per interaction in carbon tetrachloride.
