Proteins chemical fragmentation

Various methods have been used to determine the redox potentials (Table XI). Very commonly, EPR-monitored chemical redox titration is performed, which can be used to measure the redox potential not only in isolated complexes but also in membrane preparations. In general, there is good agreement between redox potentials determined in membranes, isolated complexes, or isolated Rieske proteins or fragments the only exception is the water-soluble Rieske fragment from spinach bef complex where differences of more than 50 mV have been observed by the same group but using different methods (31). 

The specifically labeled proteins are isolated and subjected to limited proteolytic digestion or chemical fragmentation. The highest (radio)activity fragments... 

More recently, software has been developed that predicts H, C, and N chemical shift values of proteins from either 3D stmcture files, for example, SHIFTS (6), SHIFTX (7), and SPARTA (8), or from the mere amino acid sequence using SHIFTY (9). First results have been reported on the de novo stmcture determination of proteins using fragment-based chemical shift predictions and molecular modeling (10, 11). 

In order to synthesize longer polypeptides and small proteins, the condensation of suitable starting fragments is an essential prerequisite. Since chemical fragment condensations suffer from the danger of enantiomerization, enzymatic ligations are pronoising alternatives (see... 

Which of the chemicals or enzymes normally used for cutting proteins into fragments would be the least useful to you ... 

EmU Fischer achieved the first chemical synthesis of a protein-like fragment in 1907, when he assembled by peptide linkage a chain of 18 amino acids and showed that the chain was degraded by proteases, proteins functioning as enzymes to degrade protein. 

A vital property of these model proteins is that they are more ordered above the transition temperature defined by the binodal or coexistence line in Figure 5.3. The polymer component of this water-polypeptide system becomes more ordered or structured on increased temperature from below to above the transition. This behavior is the inverse of that observed for most systems, as discussed above. In particular, we developed the term inverse temperature transition when the precursor protein and chemical fragmentation products of the mammalian elastic fiber changed from a dissolved state, and therefore when molecules were randomly dispersed in solution, to a state of parallel-aligned twisted filaments as the temperature was raised from below to above the phase transition. - ... 

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