Polydispersity glycoproteins

Kanno, C., Shimizu, M. and Yamauchi, K. 1977. Polydispersity and heterogeneity of the soluble glycoprotein isolated from bovine milk fat globule membrane. Agr. Biol. Chem. (Japan) 41, 83-87. 

A direct procedure for handling non-ideal, polydisperse distributions has now been derived, and has been applied, after making certain assumptions, with some success to discrete distributions of molecular weights for bronchial mucins. Assuming that the observed polydispersity of a cystic fibrosis glycoprotein (CF PHI) was due entirely to variation in the numbers of mucin basic units, it was possible to obtain representations of the observed solute distributions by using a three-component, non-ideal fit (see Fig. 13), based... 

Figure 3. Schematic representation of the cell surfaces of Leishmania sp. A) Promastigote. Only the major cell surface molecules are depicted approximate copy numbers per cell are indicated in parentheses. The cell surface contains several abundant CPI anchored proteins (gp63, PPG), the polydisperse lipophosphoglycans (LPG) and the low-molecular-mass glycoinositolphospholipids (GIPLs). B) Amastigote. The LPG and the major surface glycoprotein is greatly down-regulated and the plasma membrane contains a number of glycosphingolipids. ...

The Debye equation is based on the following physical description of the sample. This is a monodisperse solution of identical particles, which are in random orientations relative to the incident primary beam, and act as independent entities (i.e. there are no interparticle spatial correlations). The above derivation has presumed also that the particles are in vacuo. If they are in solution, they are required to form a two-phase system of solute and solvent. In biology, this corresponds to dilute solutions of pure proteins or glycoproteins in a low-salt buffer. Complications arise in the case of polyionic macromolecules in low-salt buffers, such as nucleic acids. Here, interparticle correlation effects can readily occur and the macromolecule is surrounded by an ion-cloud of opposite charge (i.e. a three-phase system). Other complications can arise in the cases of polydisperse distributions of macromolecules, oligomerization or dissociation phenomena, and conformational changes. Different formuhsms have to be derived for the analyses of these systems. 

Polymer populations in which all chains have identical masses are termed monodisperse. Proteins and DNA of the same type are necessarily monodisperse, as they are coded for precise monomer sequences. In general, however, polymer populations contain a wide distribution of masses. Such populations are termed polydisperse. While most synthetically produced polymers are polydisperse, many biopolymers are also produced in polydisperse populations for example, a variety of polysaccharides, glycoproteins, etc. 

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