which appears to be a mixture of A-

which appears to be a mixture of A- and B-type patterns rather than a distinct
crystalline structure (Buleon et al., 1998; Cairns et al., 1997l Imberty et al., 1991;
McPherson & Jane, 1999; Sevenou et al., 2002).
The structure of starch crystalline polymorphs has been studied extensively. Early
work by Wu & Sarko (1978a,b) showed that crystalline amylose forms double helices with
single helix lengths of 2.1 nm (equivalent to double helical pitch of 1.05 nm) with six
glucose residues per single helix pitch. Although these early studies suggested that the
double helices were right-handed, parallel helices, subsequent work showed they may be
left-handed (Oostergetel & van Bruggen, 1993), anti-parallel and left-handed (Eisenhaber
& Schultz, 1992), but most probably, crystalline structure is made up of a hexagonal
arrangement in which left-handed double helices packed in a parallel fashion are combined
with structured water (Gidley, 1989; Imberty & Perez, 1988; Imberty et al, 1988). In
contradiction to these observations, certain authors have proposed that although V-type
amylose complexes may be left-handed, the double helices (A- or B-type polymorphs) may
be right-handed (Veregin et al., 1987).
The double helices within the A- and B-type polymorphic forms are essentially
identical with respect to helical structure (Gidley, 1987; Imberty et al., 1991). However,
the packing of these double helices within the A-type polymorphic (crystalline) structure is
relatively compact with low proportion of structural water, whilst in B-type crystallites the
double helices are less densely packed creating a more open structure and contain a
hydrated helical core (Fig. 1.5). The factor that most likely influences the pattern in plants
is the length of the amylopectin chains, which are shorter in A-type starches. Both amylose
and amylopectin can form crystalline structures. It is assumed that branching points of
amylopectin favor helix formation. However, crystalline structures present in native starch

Kết quả (Việt) 1:

which appears to be a mixture of A- and B-type patterns rather than a distinct crystalline structure (Buleon et al., 1998; Cairns et al., 1997l Imberty et al., 1991; McPherson & Jane, 1999; Sevenou et al., 2002). The structure of starch crystalline polymorphs has been studied extensively. Early work by Wu & Sarko (1978a,b) showed that crystalline amylose forms double helices with single helix lengths of 2.1 nm (equivalent to double helical pitch of 1.05 nm) with six glucose residues per single helix pitch. Although these early studies suggested that the double helices were right-handed, parallel helices, subsequent work showed they may be left-handed (Oostergetel & van Bruggen, 1993), anti-parallel and left-handed (Eisenhaber & Schultz, 1992), but most probably, crystalline structure is made up of a hexagonal arrangement in which left-handed double helices packed in a parallel fashion are combined with structured water (Gidley, 1989; Imberty & Perez, 1988; Imberty et al, 1988). In contradiction to these observations, certain authors have proposed that although V-type amylose complexes may be left-handed, the double helices (A- or B-type polymorphs) may be right-handed (Veregin et al., 1987). The double helices within the A- and B-type polymorphic forms are essentially identical with respect to helical structure (Gidley, 1987; Imberty et al., 1991). However, đóng gói các helices đôi bên trong cấu trúc (tinh thể) A-kiểu bướu là tương đối nhỏ gọn với các tỷ lệ thấp của kết cấu nước, trong khi ở loại B crystallites các đôi helices ít đông đóng gói tạo ra một cấu trúc rộng mở hơn và chứa một ngậm nước cốt lõi xoắn ốc (hình 1.5). Các yếu tố có thể ảnh hưởng đến các mô hình ở thực vật là độ dài của dây chuyền amylopectin, ngắn hơn trong A-kiểu tinh bột. Cả hai amyloza và amylopectin có thể hình thành cấu trúc tinh thể. Người ta cho rằng phân nhánh điểm Amylopectin ưu xoắn hình thành. Tuy nhiên, cấu trúc tinh thể hiện trong bản địa tinh bột