Basic HTML Version
81
2.1. MOLECULAR WEIGHT DISTRIBUTIONS AND
AVERAGES
2.1.1.
Introduction
Most proteins and nucleic acids are biosynthesized to obtain a specific chain
length (and sequence of amino acids and nucleotides, respectively), whereas
synthetic polymers, polysaccharides and a few other biopolymers (including
rubbers, microbial polyesters and lignins) may have variable chain lengths.
The chain length of biopolymers and synthetic polymers has a strong
influence on a variety of biological and technical properties. Examples include:
•
Solubility
•
Solution viscosity
•
Gel formation
•
Film formation and adsorption to surfaces
•
Crystallinity
•
Interactions with other molecules
•
Susceptibility of enzymatic degradation
2.1.2. DP: Degree of polymerization
The term DP is much used in polymer and biopolymer science. If simply
means ‘degree of polymerization’, but is used even if the chain is made by
fragmentation of a longer chain.
Figure: A polymer chain with 24 residues (monomers): DP = 24
2.1.3. Molecular weight
(molar mass)
The molecular weight (M) of a homopolymer (all monomers are identical) is
obviously related to DP through the simple equation:
M
=
DP
⋅
M
0