Disulfides conformational transitions

In the following discussion, specimens are identified by the catalyst precursor concentrations used in the derivatization step. The feature filling images shown in Figure 2.35 [343] reveal several distinct shape transitions and related phenomena. The acceleration of the deposition rate provided by the disulfide (or thiolate) catalysts is evident from the decrease in the feature filling time from ri200 s for a specimen derivatized in 0.5 pmol L 1 SPS to 40 s for derivatization in 500 pmol L-1 SPS. For the specimens derivatized in 0.5 pmol L 1 S P S, deposition proceeds conformally and... 

This transition to the activated conformation of the receptor involves relative movements of the inner and outer parts of the 3-sandwich, which compose the core of the a subunit (see Figs. 11.4-11.6), around the cys-loop disulfide bond, as shown in Fig. 11.9. 

At elevated temperatures the RNase molecule undergoes a transition from a folded to an unfolded state (5). This can be shown by optical and viscosity measurements. The transition temperature depends on pH and ionic strength. Above this temperature the tertiary structure is destroyed but the covalent disulfide bonds remain intact. The unfolding is reversible since on lowering the temperature the native conformation is regained. 

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