Characterization of meningococcal polysaccharides by optical mixing spectroscopy. II. Effects of temperature, EDTA, and ionic strength on aggregation of group C polysaccharides in solution

✍ Scribed by S. Fujime; F. C. Chen; B. Chu; T. Y. Liu

• Publisher: Wiley (John Wiley & Sons)
• Year: 1977
• Tongue: English
• Weight: 802 KB
• Volume: 16
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1977.360160502

✦ Synopsis

Abstract

We have studied the effects of temperature, EDTA, and ionic strength on C‐polysaccharides in solution by examining the details of the time‐correlation function using a 96‐channel single‐clipped photon correlation spectrometer. Our linewidth results have shown that the C‐polysaccharides in buffer solution form aggregates of very broad distributions. Thus, fractionation by gel‐filtration chromatography is only mildly effective. Although the aggregate sizes seem to remain relatively constant from 4 to 25°C, a fraction of those aggregates break up to form smaller fragments or monomers at higher temperatures. However, the dissolution‐association process is quite slow and takes days even at room temperatures before the equilibrium is reached. We have also shown that by adding an excess amoutn of EDTA, the aggregates can be broken up. Again the dramatic changes occur only at short delay times suggesting that a protion of the larger aggregates remains. Finally, the amount and size of aggregates depend upon the ionic strength which exhibit a maximum ΓT/sin^2^ (θ/2) around 0.1–0.2 M KCl.

If the activities of polysaccharides in solution depend upon molecular size, the standard techniques such as gel‐permeation chromatography and ultracentrifugation cannot properly characterize the detailed size distribution. Quasielastic laser light scattering can provide us with a qualitative model. The quantitative details must necessarily await more extensive investigations using a combination of the techniques and better fractionation procedures in an appropriate buffer solution.