RESUMO
A combined DSC-SAXS approach was employed to study the effects of amylose and phosphate esters on the assembly structures of amylopectin in B-type polymorphic potato tuber starches. Amylose and phosphate levels in the starches were specifically engineered by antisense suppression of the granule bound starch synthase (GBSS) and the glucan water dikinase (GWD), respectively. Joint analysis of the SAXS and DSC data for the engineered starches revealed that the sizes of amylopectin clusters, thickness of crystalline lamellae and the polymorphous structure type remained unchanged. However, differences were found in the structural organization of amylopectin clusters reflected in localization of amylose within these supramolecular structures. Additionally, data for annealed starches shows that investigated potato starches possess different types of amylopectin defects. The relationship between structure of investigated potato starches and their thermodynamic properties was recognized.
Assuntos
Amilopectina/química , Amilopectina/isolamento & purificação , Amilose/química , Amilose/isolamento & purificação , Fosfotransferases (Aceptores Pareados)/metabolismo , Solanum tuberosum/química , Solanum tuberosum/enzimologia , Sintase do Amido/metabolismo , Amilopectina/análise , Amilose/análise , Varredura Diferencial de Calorimetria , Plantas Geneticamente Modificadas , Espalhamento a Baixo Ângulo , Solanum tuberosum/genética , Termodinâmica , Água , Difração de Raios XRESUMO
Structure and thermodynamic properties of native and annealed wheat starches with different amylose content (from 1.5% to 39.5%) have been studied by high-sensitivity differential scanning microcalorimetry (HSDSC), small-angle X-ray diffraction (SAXS), light (LM), and scanning electron microscopy (SEM). Starch morphology, the values of the melting cooperative unit, the thickness of crystalline lamellae and the size of amylopectin clusters as well as thermodynamic parameters characterizing surface of the face side in starch crystals were determined. Some suppositions based on different physical approaches are used for a discussion of the results concerning structural reorganization of starches on different levels of macromolecular organization.
Assuntos
Mutação/genética , Amido/química , Amido/ultraestrutura , Triticum/química , Triticum/genética , Amilose/análise , Varredura Diferencial de Calorimetria , Microscopia Eletrônica de Varredura , Termodinâmica , Triticum/ultraestrutura , Difração de Raios XRESUMO
Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) were used to investigate the internal structure of wheat starch granules with different amylose content. Different approaches were used for treatment (interpretation) of SAXS data to assess the values of structural parameters of amylopectin clusters and the size of crystalline and amorphous lamella in different wheat starches. The average values of the semi-crystalline growth rings thickness in starches have been determined and the relationship between structural characteristics and thermodynamic melting parameters is discussed.