Conformational transitions measurements

Intrinsic viscosity measurements revealed a conformational transition upon heating from 26 to 40 °C, while the UV absorbance of the solution was insensitive to the change. The entropy parameters for PA were also discussed in light of the Flory-Krigbaum correlation between the second virial coefficient and theta temper-... 

In addition, data on the size, shape and solvation of the polymer particles in aqueous solutions at temperatures below and above the transition phenomena registered by HS-DSC have been obtained [42]. Table 2 shows the results of capillary viscometry and light scattering experiments for the fractions p and s of poly(NVCl-co-NVIAz) synthesized at 65 °C from the feed with the initial molar comonomer ratio equal to 85 15. Since fraction p precipitates from the aqueous solution at temperatures > 34 °C, its intrinsic viscosity can be determined only at 20 °C, whereas for the fraction s such measurements were possible above and below the temperatures of the HS-DSC-registered conformational transition. 

Enthalpy of Conformational Transition of a Protein from Indirect Calorimetric Measurements [8]... 

An improvement is to use a windowed RMSD function as a measure of the rate of conformation change. Specifically, for a given window length (e.g., 10 consecutive trajectory snapshots), the average of the all of the pairwise RMSDs (or alternatively, the average deviation from the average over that interval) is computed as a function of time. This yields a measure of conformational diversity over time, and can more readily reveal conformational transitions. 

Like other macromolecules, RNA is dynamic. The process of folding into a structured RNA involves dynamic rearrangement of RNA helices, and many RNAs function via a series of conformational transitions. Thus, measurement of the dynamics of individual helices will be required to fully understand RNA folding and function. Additionally, dynamic information can also be used to provide information about local structural features. 

Circular dichroism (CD) has been utilized to investigate the effect of saccharides on the conformation of lectins in solution. CD has demonstrated saccharide-induced conformational changes in the lectins from Canavalia ensiformis (7), Dolichos biflorus (8), Ricinus communis (9), and Triticum vulgaris (10). The present study uses circular dichroism to assess the secondary structure of SBA and to measure conformational transitions induced by the saccharides which bind to this lectin. These and previous studies will contribute to a clearer understanding of the unique properties of these sugar-binding proteins. 

Flatmark, T., Stokka, A. J., and Berge, S. V. (2001) Use of Surface Plasmon Resonance for real time measurements ofthe global conformational transition in human phenylalanine hydroxylase in response to substrate binding and catalytic activation, Anal. Biochem. 294, 95-101. 

This behavior can be seen as complementary to another aspect of protein folding the withdrawal of hydrophobic side chains from solvent. The latter minimizes perturbation by burying those portions of the polypeptide for which water is the poorest solvent. The former minimizes perturbation of solvent by what remains exposed. Not all biological macromolecules show so small an effect. Nucleic acids require for their hydration about twice the amount of water required by globular proteins (for heat capacity measurements comparing protein and tRNA, see Rupley and Siemankowski, 1986). It may be signihcant that DNA, with an extensive hydration shell, undergoes facile hydration-dependent conformational transitions, which are not found for proteins. 

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