Reversible conformational changes

Figure 17. Molecular motor reverse conformational changes (mechanical energy) stimulated by oxidation or reduction of the polymeric chain, a) reduced chain b) oxidized chain.

Preliminary results using fixed polarizer FT-IRRAS to study the melting and hydration of cadmium arachidate on low area metals show that both irreversible and reversible conformational changes can be... 

Most enzyme powders are prepared by lyophilisation (freeze drying). However, the lyophilization procedure might inactivate the enzyme to some extent. To avoid this and thereby increase the activity of lyophilized enzymes in dry organic solvents, the lyophilization can be carried out in the presence of lyoprotectants such as sorbitol (Dabulis and Klibanov, 1993). The inactivation is believed to be caused at least partly by a reversible conformational change in the enzyme. This process can be reversed and the enzyme reactivated by the addition of small amoimts of water (Dabulis and Klibanov, 1993). 

The reversible conformational change was seen by the disappearance of unresolved magnetic HFS of Mossbauer spectra after the illumination (decrease of spin-lattice relaxation time) and its restoration after the illumination of bleached samples at 77°K by light of 575 nm wavelength. 

Figure 3 Photoresponsive polypeptides showing a reversible conformational change.

Kouns, W. C., Kirchhofer, D., Hadvary, P., Edenhofer, A., Weller, T., Pfenninger, G., Baumgartner, H. R., Jennings, L. K., and Steiner, B. (1992). Reversible conformational changes induced in glycoprotein Ilb-IIIa by a potent and selective peptido-mimetic inhibitor. Blood 80, 2539-2547. 

The titration curve can give no information on the subject of reversible conformational change in insulin because there is extensive pH-dependent association between insulin molecules. The absence of other conformational change is indicated by hydrodynamic measurements of Fredericq (1966). 

HSA exists as a single polypq>tide chain of S8S amino acids. X-Ray crystallographic analysis has confirmed that this chain is folded into thi domains, each of which is seen to exist as two subdomains (13). HSA und oes extrasive, pH dependent, reversible conformational changes (14). The so-called add expansion at low pH is accompanied by loss of a large fraction of a-helical structure. 

It is now well established that the catalytic properties of a wide variety of enzymes remain intact in organic solvents (11-13). These findings imply that proteins may also retain their native struetures when lyophilized and dispersed in organic solvents. Evidence has been obtained that crystallized proteins have essentially the same structure in water and organic solvent (14,15). In the lyophilized state, proteins are also in a nonaqueous environment and it is expected their physico-chemical properties will differ from that in solution, as the dynamic conformational equilibria that exits in solution will be absent. Some physico-chemical studies indicate that the structure of the lyophilized state is very similar to that in solution (16-18), while others indicate that there is some limited but reversible conformational change (19-24). There are likely to be... 

Fig. 3. Photoinduced reversible conformation changes of HEMA-VPy copolymer — CHP complex in water at 30 °C [6]. (O) reduced viscosity of 0.334 dl/g copolymer (HEMA content, 0.62) ( ) absorbance at 404 nm...

Non-reversible adsorption to anti-receptors Reversible conformational change of virus... 

Photoswitchable materials could be important components in molecular-scale electronic devices and several new systems have been reported. There have been other investigations of phototropic systems in which light is used to drive a reversible conformational change " or, in the case of liquid crystals, a phase transformation. Such photosystems are of interest for the engineering of microscopic photoactive devices but the subject is still in its infancy and practical devices remain elusive. Much more subtle is the use of light to trigger a change in... 

O. Pieroni, J. L. Houben, A. Fissi, P. Costantino, and F. Ciardelli, Reversible conformational changes induced by light in poly(L-glutamic acid) with photochromic side chains, J. Am. Chem. Soc. 102, 5913-5915(1980). 

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