Oxygen mimics

Wilmot et al. (1999) have reported high resolution crystal structures of three species relevant to understanding the chemistry of the oxidative half cycle of amine oxidases, (i) anaerobic substrate-reduced ECAO, (ii) anaerobic substrate-reduced ECAO with bound nitric oxide (an oxygen mimic) and (iii) ECAO reacted aerobically with substrate to reach an equilibrium turnover state, then cryo-trapped. In all these species, product aldehyde remains bound at the back of the substrate binding pocket and this seems to be crucial in allowing build up of intermediates. 

HIV-1 protease (HIV-1 PR) Non-peptide, C2-symmetric cyclic urea derivatives were designed de novo to fit the HlV-i PR active site. These novel, conformationally-constrained inhibitors feature a diol functionality that interacts with the catalytic aspartates while an urea oxygen mimics a structural water mediating substrate interactions with the enzyme flap. The required absolute configuration at four chiral centers was correctly predicted. Potent, bioavailable clinical candidates emerged from this work. i37 ... 

These membranes mimic natural photosynthesis except that the electrons are directed to form hydrogen. Several sensitizers and catalysts are needed to complete the cycle, but progress is being made. Various siagle-stage schemes, ia which hydrogen and oxygen are produced separately, have been studied, and the thermodynamic feasibiHty of the chemistry has been experimentally demonstrated. 

Furthermore, the GPO procedure can also be used for a preparative synthesis of the corresponding phosphorothioate (37), phosphoramidate (38), and methylene phosphonate (39) analogs of (25) (Figure 10.20) from suitable diol precursors [106] to be used as aldolase substrates [102]. In fact, such isosteric replacements of the phosphate ester oxygen were found to be tolerable by a number of class I and class II aldolases, and only some specific enzymes failed to accept the less polar phosphonate (39) [107]. Thus, sugar phosphonates (e.g. (71)/(72)) that mimic metabolic intermediates but are hydrolytically stable to phosphatase degradation can be rapidly synthesized (Figure 10.28). 

A potential major benefit of a cyclohexene-based template was the capacity to mimic more closely the putative transition state sialosyl cation by the placement of a double bond in the correct position. While the ring conformation in Neu5Ac2en 4 is very similar to the sialosyl cation transition state 5, these two stracmres are essentially isomers due to the fact that the double bond is either between the ring oxygen and C-2 in 5 or C-2 and C-3 in 4. The synthesis and biological evaluation of... 

The 3D structure of the 2,3-diphosphoglycerate (DPG) complex of hemoglobin (Hb) served to derive simple aromatic dialdehydes that mimic the function of DPG as an allosteric modulator of the oxygen affinity of Hb. Some of the resulting compounds were as active and even more active than DPG, the natural ligand [1-3]. 

In an attempt to design the p-turn-peptide-mimics, aspartic acid (an amino acid also known as aspartate) and lysine (an amino acid especially found in gelatin and casein) were attached to each amine group of 1,3-diaminoada-mantane in the form of amide bonds. The term p-turn refers to a peptide chain that forms a tight loop such that the carbonyl oxygen of one residue is hydrogen... 

Studies on the autoxidation of carotenoids in liposomal suspensions have also been performed since liposomes can mimic the environment of carotenoids in vivo. Kim et al. have studied the autoxidation of lycopene (Kim et al. 2001), -carotene (Kim 2004), and phytofluene (Kim et al. 2005) in liposomal suspensions and identified oxygenated cleavage compounds. The stability to oxidation at room temperature of various carotenoids has also been studied when incorporated in pig liver microsomes (Socaciu et al. 2000), and taking into account membrane dynamics. After 3 h of reaction, P-carotene and lycopene had completely degraded, whereas the xanthophylls tested were shown to be more stable. 

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