Lamellae amorphous

Figure 4.3 The building block structure of potato amylopectin clusters. Branched building blocks (encircled) are mainly found inside amorphous lamellae (A) of semi-crystalline rings in starch granules. Double helices (symbolized as cylinders) extend from the building blocks into the crystalline lamellae (C). Enlargements of a double helix segment, in which the single strands are parallel and left-handed, and a building block are shown to the right.

Potato starch, and tuberous starch in general, has some unique properties as compared to cereal starches. The most important ones include long amylopectin chains forming hydrated and ordered B-type crystallites and the presence of phosphate esters. The clusters of potato amylopectin are comparatively small, comprising 5-10 short chains. The internal part ofthe clusters is organized into branched building blocks mainly found in the amorphous lamellae of the... 

Assuming random mixing in the amorphous lamellae and the melt, the non-combinatorial free energy change per mole of segments on mixing can be written... 

W. Sieber (Inst, fur Kristallographie und Petrographie, ETH, Zurich) Did you ever examine the behavior on heating of the filtrate from the amorphous lamellae Is it excluded that formation of lamellae and formation of zeolites are independent phenomena ... 

Amylopectin synthesis involves chain elongation followed by branching. Branching occurs in clusters. Twenty to twenty-five chains may be included in a cluster, which is called the crystalline lamellae. About 80%-90% of the chains are involved in clusters [39]. Some of the chains in a cluster may exist as left-handed double stranded helices, which increase the stability of the clusters. Clusters are linked by long B-chains. Most B-chains extend into two to three clusters [39]. Between the clusters is a region with few branches. This region is called the amorphous lamellae. Thus, there is an alternating sequence of crystalline and amorphous lamellae within the amylopectin molecule. 

The semi-crystalline nature of starch is well known and its most important feature is the alternation of long-range molecular order and amorphous regions, defining the corresponding alternation of crystalline and amorphous lamellae [14, 16, 20, 31],... 

Figure 19.2 Stack of repeated crystaUine and amorphous lamellae in blocklet strue ture of starch granules.

Figure 4.17 Representation of the structure of a starch granule. The starch granules (A) are birefringent under polarised light (B). The granules exhibit growth rings (C) which consist of alternating hard semicrystalline (D) and soft amorphous shells (E). The semi-crystalline shell is organised in blocklets composed of stacks of crystalline (F) and amorphous lamellae (C). Amylopectin (H) is responsible for the crystallinity. Amylose (I) and amylose-lipid complexes (J) are not ordered and form amorphous domains (from Ref. [50]).

Figure 6.22 Hierarchical structure of starch, (a) Whole granule (scale pm), (b) Growth rings ( 100s nm), (c) crystalline and amorphous lamellae ( 9 nm) and (d) molecular structure of amylopectin ( A). [Reproduced with permission from T. A. Waigh, Applied Biophysics, John Wiley Sons. Copyri t (2007) John Wiley Sons Limited]...

Figure 5.26 shows the three-dimensional arrangement of starch in the granules the crystalline lamellae with the more linear amylose and the amorphous lamellae with the more branched amylopectin. Synthetic multiblock pol5miers can have similar structures. 

Figure 9.1 A model of starch granule structure (a) single granule, (b) expanded view of internal structure and (c) the cluster structure of amylopectin. Amylopectin is a branched polymer, seen here extending through many crystalline and amorphous lamellae. (Taken from [3] - Reproduced by permission of The Royal Society of Chemistry.)...

Figure 2 Semicrystalline polymer organized into stacks of crystalline and amorphous lamellae.

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