Biopolymer rigidity

Allison, S.A. and McCammon, J.A. (1984) Transport properties of rigid and fiexible macromolecules by Brownian dynamics simulation. Biopolymers 23, 167-187. 

For the case of flexible non-rigid particles, a penetration parameter can be used to take into account the softness of the biopolymer interactions. This parameter is defined as the ratio of the equivalent hard sphere radius to the corresponding radius of gyration (Tanford, 1961) ... 

In equation (5.33), as previously defined, An is the second virial coeffi-cient of the / -biopolymer component on the molal scale (cm mol- ) and RGl is the radius of gyration of the / -biopolymer component. For a flexible polymer chain the value of the penetration parameter y/ lies in the range 0.6-0.7, while for a semi-rigid/worm-like polymer we have y/ - 0.3 (Tanford, 1961). The shorter the polymer chain, the closer is its effective conformation to that of the equivalent hard sphere. 

The major classes of biopolymer, starch and starch blends, polylactic acid (PLA) and aliphatic-aromatic co-polyesters, are now being used in a wide variety of niche applications, particularly for manufacture of rigid and flexible packaging, bags and sacks and foodservice products. However, market volumes for biopolymers remain extremely low compared with standard petrochemical-based plastics. For example, biopolymer consumption accounted for just 0.14% of total thermoplastics consumption in Western Europe for 2005. 

Yathindra N, Sundaralingam M (1973) Correlations between the backbone and side chain conformations in 5 -nucleotides. The concept of a rigid nucleotide conformation. Biopolymers 12 297-314... 

Since food systems usually contain a heterogeneous mixture of proteins and polysaccharides differing in chemical nature, conformation, chain rigidity, size, and shape of molecules, degrees of hydrolysis, denaturation, dissociation and aggregation, information on model systems containing two biopolymers is not sufficient to interpret phase behaviour and functionality of real dispersed food systems. 

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