Based Mimics

Peptoid-Based Mimics of Lung Surfactant Proteins... 

Recently, peptoid-based mimics of both SP-C and SP-B have been designed to adopt helical secondary structures, and also mimic (to varying degrees) the sequence patterning of hydrophobic and polar residues found in the natural surfactant proteins. Peptoid-based SP-C mimics of up to 22 monomers in length, were synthesized and characterized by in vitro experimental methods [67, 68] (Fig. 1.8). The secondary structure of all molecules was assessed by circular dichroism and found to be helical. The surface activities of these peptoids, in comparison to the actual SP peptides described above, were characterized by surfactometry using... 

Any artificial rotaxane-based mimic of the natural ATP synthase motor must bear a chiral element that helps to define the direction of rotation. Chirality can, of course, be implemented in such molecules by adding chiral groups as the stoppers or the wheel. Rotaxanes with cyclodextrins as the wheels have been described [11], and rotaxanes with glucose-containing stoppers are known [14]. Rotaxanes with elements of planar chirality have also been realized [15]. 

SCHEME 14.20 Solid-phase synthesis of glycopeptide-based mimics. 

It must be said that this level of activity is surprising, especially against amide bonds, and intensive efforts to repeat the results are under way. If confirmed this work will be seen as an important advance the design stage may be complex, but with modem synthetic methods peptides of this sort of size are quite reasonable synthetic targets. A practical limitation, as always with enzyme-based mimics, is that - at this stage of development at least - complete success simply means doing a reaction as well as an available natural catalyst. 

While some functional hydrolytic models of NHase have been obtained with cobalt mimics of NHase, to our knowledge catalytic nitrile hydrolysis has not been observed with iron-based mimics (14). In order to achieve hydrolysis of nitriles, the iron center must be able to function as a Lewis acid to coordinate the nitrile and polarize the carbon nitrogen triple bond or bind water and lower its pKa. In either event, an accessible coordination site on iron is required. 

Yu T, Zeng Y, Chen J, Li Y-Y, Yang G, Li Y (2013) Exceptional dendrimer-based mimics of diiron hydrogenase for the photochemical production of hydrogen. Angew Chem Int Ed 52 (21) 5631-5635. doi 10.1002/anie.201301289... 

Gauter-Fleckenstein B, Fleckenstein K, Owzar K et al. (2007) Comparison of two Mn porphyrin-based mimics of superoxide dismutase in pulmonary radioprotection. Free Radic Biol Med 44 982-989... 

Manual control of the operation of a sulphonation plant can be supplemented by computer-based data logging. Such systems are non-interactive in that analogue and digital signals from the plant are fed to the computer/data logging system, but information is not fed back. Consequently, the status of pumps etc. and other data can be displayed on the screen-based mimics, reports can be printed and the data obtained can be manipulated to show trends or used in other off-line computer programs. 

Gas-phase spectroscopy of neutral molecules, as opposed to ions, usually involves the use of supersonic molecular beams [1 ]. For smaller compounds this can be achieved by seeding in the inert drive gas. This limitation excludes the study of neutral nucleosides or larger compounds while even some of the bare nucleobases, such as guanine, cannot be sufficiently heated without thermal degradation. Some work with bases and base mimics has been done in seeded beams [5-10]. Larger compounds can now be vaporized successfully by pulsed laser desorption, followed by entrainment in a supersonic jet [11-14]. This experimental advance has opened up the field of study of nucleobases and nucleosides in isolation in the gas phase, especially by IR spectroscopy. The cooling in molecular beams makes this approach particularly attractive for spectroscopy. Although temperatures are not as low as in ion traps or helium droplets, molecular beams can achieve internal temperatures typically of the order of 10-20 K, which provides very useful optical resolution. 

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