RESUMO
A series of monoacylated glycolipids with even-numbered acyl chain lengths ranging from saturated C11 to C15 and an unsaturated C17:1 fatty acid connected by an amide in linkage to the disaccharide head groups maltose, melibiose and lactose were synthesized. The structural polymorphism of the glycolipids was investigated using Fourier-transform infrared spectroscopy and differential scanning calorimetry for the detection of the gel to liquid-crystalline acyl chain melting behaviour and small-angle X-ray scattering for the elucidation of the physical structure of the lipid aggregates. Also, the phase morphology was studied by polarizing microscopy in contact preparations. The data clearly show the existence of uni- and multilamellar structures. Although only one acyl chain is present, there is no evidence for the existence of micelles - of spherical or of cylindrical (H(I)) type - or of interdigitated phases. The preference for lamellar phases seems to be correlated with the intrinsic high conformational order of the amide linkage of these compounds which inhibits the formation of highly curved structures.
Assuntos
Glicolipídeos/química , Glicolipídeos/síntese química , Lactose/química , Maltose/química , Melibiose/química , Acilação , Varredura Diferencial de Calorimetria , Cristalização , Lactose/síntese química , Cristais Líquidos , Maltose/síntese química , Melibiose/síntese química , Microscopia de Polarização , Transição de Fase , Espalhamento a Baixo Ângulo , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Difração de Raios XRESUMO
We synthesised a new glyco-glycero-lipid [1,3-di-O-(beta-D-glucopyranosyl)-2-deoxy-2-amino-N-palmitoyl-sn-glycerol] with a Y-shaped structure bearing two sugar head groups and only one fatty acid chain. Instead of an ester linkage between the glycerol and the fatty acid an amido function was introduced. The mesogenic properties were investigated using polarising microscopy and are discussed with respect to similar compounds. The lyotropism was measured using the contact preparation method and small-angle neutron-scattering.
Assuntos
Glicerol/química , Glicolipídeos/síntese química , Membranas Artificiais , Amidas/química , Carboidratos/química , Ésteres/química , Ácidos Graxos/química , Glicosilação , Fluidez de Membrana , Microscopia de Polarização , Espalhamento de Radiação , Relação Estrutura-Atividade , Água/químicaRESUMO
As part of a series of papers, the influence of carbohydrate headgroups and aliphatic chains on the mesogenic properties of glycolipids was investigated. Alkyl glycosides with different types of aliphatic chains were synthesised. Neutral glycolipids were oxidized to their uronic acid derivatives, using the well established TEMPO-oxidation. For comparison a 6-deoxy-6-amino alkylglucopyranoside was synthesised. In addition, the thermotropic and lyotropic phase behaviour of the synthesised compounds were investigated. The thermotropism was characterised by polarising microscopy, the lyotropism by the contact preparation method.
Assuntos
Glicosídeos/síntese química , Cristalização , Glicosídeos/química , Glicosilação , Microscopia de PolarizaçãoRESUMO
This paper is part in a series of papers, investigating the influence of carbohydrate headgroups on the mesogenic properties of glycolipids. While previous papers focussed on the synthesis and mesogenic properties of the pure compounds, we will discuss here our results obtained with binary mixtures. Mixtures of compounds, one forming a lamellar phase and the other one a columnar phase in their pure state, displayed always an induced cubic phase. The stability of this induced cubic phase depends significantly on the structure of the carbohydrate headgroup of both components. Thus it was possible to derive structure-property relationships by comparison of the phase diagrams that have been obtained, if the carbohydrate headgroup of one component was changed systematically. We observed an interesting effect of galactose headgroups which might be of great biological importance. Furthermore, the observed kind of kinetic of the S(A)-->cub transition might also be of great biological relevance.
Assuntos
Carboidratos/química , Glicolipídeos/química , Cristalização , Diglicerídeos , Galactose , Fosfatidilcolinas , TemperaturaRESUMO
We synthesised glycosyl diacylglycerols bearing unsaturated or chiral methyl branched fatty acid chains. The thermotropism was measured with polarising microscopy and additionally the lyotropism with the contact preparation method. The synthesised compounds displayed thermotropic S(A) (lamellar), cubic and columnar phases and investigation of the lyotropic phase behaviour led to the observation of inverted bicontinuous cubic V(II) phases, lamellar L(alpha) phases and normal bicontinuous cubic V(I) phases. The phases are discussed with respect to the chemical structures that have been varied systematically to derive structure--property relationships.
