MultiSig: a new high-precision approach to the analysis of complex biomolecular systems

MultiSig is a newly developed mode of analysis of sedimentation equilibrium (SE) experiments in the analytical ultracentrifuge, having the capability of taking advantage of the remarkable precision (~0.1 % of signal) of the principal optical (fringe) system employed, thus supplanting existing methods of analysis through reducing the ‘noise’ level of certain important parameter estimates by up to orders of magnitude. Long-known limitations of the SE method, arising from lack of knowledge of the true fringe number in fringe optics and from the use of unstable numerical algorithms such as numerical differentiation, have been transcended. An approach to data analysis, akin to ‘spatial filtering’, has been developed, and shown by both simulation and practical application to be a powerful aid to the precision with which near-monodisperse systems can be analysed, potentially yielding information on protein-solvent interaction. For oligo- and poly-disperse systems the information returned includes precise average mass distributions over both cell radial and concentration ranges and mass-frequency histograms at fixed radial positions. The application of MultiSig analysis to various complex heterogenous systems and potentially multiply-interacting carbohydrate oligomers is described

Carbohydrate Self-Association Protein-like Oligomerization of Carbohydrates

Many proteins form noncovalent and thermodynamically reversible oligomers, and the state of self-association can dictate a proteins functionality. DNA-binding proteins are very often dimeric, while other proteins exist as trimers (e.g. chloramphenicol transacetylase), tetramers (e.g. hemoglobin), or higher-order reversible association products (tubulin, viral coat proteins, sickle cell hemoglobin), with clear functional roles that have never been observed for carbohydrates. Although weak self-association in a polysaccharide has been shown, Water-soluble aminocelluloses were prepared by the reaction of tosyl cellulose with an excess of di-or trifunctional amines, namely with tris(2-aminoethyl)amine yielding 6-deoxy-6-(2-(bis(2-aminoethyl)aminoethylamino) (BAEA) cellulose (1-3), as depicted in To ascertain whether the higher-order species are different oligomers, a simple logarithmic relationship between sedimentation coefficient s and molecular weight M can be utilized, namely s % M b or, equivalently, s i /s 1 % (M i /M 1 ) b , where 1 denotes the monomer, i denotes the i th species, and b is a power-law coefficient that depends on the conformation (ca. 0.2 for rods, 0.5 for coils, and 0.7 for spheres). [4] Taking the first observable species in each case as the monomer, all five of the 6-deoxy-6-aminocelluloses follow the power-law relation with b % 0.7, a value consistent wit