Non-natural ligands

The generation of BBP variants with novel binding specificities for fluorescein or digoxigenin, respectively, has demonstrated for the first time that a lipocalin can be tailored to recognize non-natural ligands. In order to illustrate the anti-body-like binding function of the engineered lipocalins, this new class of proteins was termed anticalins [40]. 

A collection of non-natural ligands - synthesized independently in various laboratories - has demonstrated an immense chemical production effort in search of specific modulators of the immune system with significantly reduced... 

Figure 8. Natural, non-natural and synthetic ligands for ERft, PPARy, and FXR receptors.

Apart from a comparison of the cis and trans dichloro complexes and a comparison of dichloro with chloroaquo species, little has been done to study the effect of the non-amine, monodentate non-participating ligands upon the lability of Rum complexes. Where studied, cis-dichlorotetra-(amine) complexes are considerably more labile than their trans isomers but there are insufficient data at this time to say whether there is any great sensitivity of lability to the nature of the tetraamine ligand in such systems. The extremely low reactivity of irans-[Ru(cyclam)Cl2]+ (the rate constant for Cl- exchange is reported293 to be 3 x 10 7s 1 at 102 °C) seems to be an exception that is, as yet, unexplained. Some relevant data are collected in Table 11. 

---