Biopolymer molecular weights

Small-Angle X-Ray Scattering Measurements of Biopolymer Molecular Weights in Interacting Systems... 

Biopolymer Molecular Weight Maximum Length of Biopolymer... 

At first glance, the contents of Chap. 9 read like a catchall for unrelated topics. In it we examine the intrinsic viscosity of polymer solutions, the diffusion coefficient, the sedimentation coefficient, sedimentation equilibrium, and gel permeation chromatography. While all of these techniques can be related in one way or another to the molecular weight of the polymer, the more fundamental unifying principle which connects these topics is their common dependence on the spatial extension of the molecules. The radius of gyration is the parameter of interest in this context, and the intrinsic viscosity in particular can be interpreted to give a value for this important quantity. The experimental techniques discussed in Chap. 9 have been used extensively in the study of biopolymers. 

Owing to the weak hydrophobicity of the PEO stationary phases and reversibility of the protein adsorption, some advantages of these columns could be expected for the isolation of labile and high-molecular weight biopolymers. Miller et al. [61] found that labile mitochondrial matrix enzymes — ornitine trans-carbomoylase and carbomoyl phosphate synthetase (M = 165 kDa) could be efficiently isolated by means of hydrophobic interaction chromatography from the crude extract. 

With the LC-MS interfaces now available, a wide range of analytes, from low-molecular-weight drugs and metabolites (<1000 Da) to high-molecular-weight biopolymers (>100000 Da), may be studied. 

Note that for the determination of molecular weight, the charge-state distribution is not of great importance as it does not affect the m/z value of the ion involved and thus the calculated molecular weight. If the conformational state of the biopolymer is of interest, however, the distribution of charged states is a fundamental consideration and any parameter likely to change this distribution must be carefully controlled. 

The application areas for LC-MS, as will be illustrated later, are diverse, encompassing both qualitative and quantitative determinations of both high-and low-molecular-weight materials, including synthetic polymers, biopolymers, environmental pollutants, pharmaceutical compounds (drugs and their metabolites) and natural products. In essence, it is used for any compounds which are found in complex matrices for which HPLC is the separation method of choice and where the mass spectrometer provides the necessary selectivity and sensitivity to provide quantitative information and/or it provides structural information that cannot be obtained by using other detectors. 

The polarity and thermal instability of biopolymers, together with the almost exclusive formation of singly charged ions renders APCl an inappropriate ionization technique for their study. Much of the early work involving electrospray ionization, on the other hand, was connected with the analysis of this type of molecule, in particular determining the molecular weight of proteins for which it is particularly effective. 

The molecular weight calculated for gelatin is 333,000g/mol. The value of a given at different temperatures shows that this biopolymer in aqueous solution behaves in a conformation predominantly confined to the rod-like, different as observed by Bohidar 1998. 

With notable exceptions, the application of HPLC to clinical chemistry has not as yet been extensive. This is somewhat surprising in view of the potential the method has for this area. This potential arises, in part, from the fact that HPLC is well suited to the types of substances that must be analyzed in the biomedical field. Ionic, relatively polar species can be directly chromatographed, without the need to make volatile derivatives as in gas chromatography. Typically, columns are operated at room temperature so that thermally labile substances can be separated. Finally, certain modes of HPLC allow fractionation of high molecular weight species, such as biopolymers. 

Silica gels with mean pore diameters of 5-15 nm and surface areas of 150-600 m /g have been preferred for the separation of low molecular weight samples, while silica gels with pore diameters greater than 30 nm are preferred for the separation, of biopolymers to avoid restricting the accessibility of the solutes to the stationary phase [15,16,29,34]. Ideally, the pore size distribution should be narrow and symmetrical about the mean value. Micropores are particularly undesirable as they may give rise to size-exclusion effects or irreversible adsorption due to... 

---