Polypeptides, azobenzene groups

A detailed investigation of photochromism, conformation and CD properties was carried out in recent years on poly(L-glutamic acid) having various contents of azobenzene groups in the side chains. In trimethylphosphate (TMP), the azo-polypeptides exhibited the a-helix CD pattern. In water at acid pH, the polymers containing 16 mol % and 21 mol % azobenzene groups adopted the a-helix structure while a P-structure was present in a 36 mol % azo-polypeptide. 

The exploitation of the ,Z-isomerization of the azoaromatic group for conformational problems was first studied in the 1960s. Goodman and Fabca synthesized copolypeptides of L-p-(phenylazo)phenylalanine with y-benzyl-L-glutamate. They found that photoisomerization of the azobenzene group in synthetic polypeptides resulted in changes in the ORD spectra due to changes in the conformation. 

These polypeptides exhibited photochromic behavior associated with the photoisomerization of their azobenzene moieties, as discussed in Section 13.1 (Figure 1). At room temperature, in the dark, azo groups exist in the more stable trans config-... 

Analogous membranes have been prepared from poly(L-glutamic acid) containing about 14 mol % azobenzene-sulfonate groups in the side chains (Scheme 3, Structure IV). 25 109 The polypeptide was adsorbed onto a porous support and the hydro-... 

Light-induced transformations from one structure to another have been studied with many modified polypeptides [13, 14] bearing pendant photochromic groups such as azobenzene or spiropyran groups. Typical examples are the modified poly(L-glutamic acids) PGA-1 and PGA-2 presented in Chart 5.5. 

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