PubMed · 16488732
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Erle H Austin. 2006. Invited commentary.. https://doi.org/10.1016/j.athoracsur.2005.12.045
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This study addresses some microbial inactivation phenomena induced by high pressure CO2 over micro-organisms and enzymes. The activity of four selected enzymes was measured before and after treatment with CO2 under pressure in both buffer solutions and natural cellular environment (E. coli cells and tomato paste). Results are reported for acid phosphatase, alkaline phosphatase, ATPase, and pectinase at different conditions of temperature, CO2 pressure, and treatment time (32-40 degrees C, 85-150 bar, 30-70 min). The results obtained show that the high pressure CO2 treatment induces an inactivation of cellular enzymatic activity higher than the one caused on the same enzymes in solution. However, the measured activity difference is not caused by a damage at the enzymes molecular level but is a consequence of the permeabilization of the cellular envelopes which leads to a release of unmodified enzymes from the cells with simultaneous drop of enzymatic cellular activity. The reported data suggest that the bacterial cell death is probably due not to a selective effect of high pressure CO2 treatment but to simultaneous detrimental action of CO2 on cellular membrane and cell wall.
A series of neutral Ni(II)-salicylaldiminato complexes substituted with perfluorooctyl- and trifluoromethyl groups, [Ni{kappa(2)-N,O-6-C(H)==NAr-2,4-R'(2)C(6)H(2)O}(Me)(pyridine)] (6 a: Ar=2,6-{4-(F(17)C(8))C(6)H(4)}(2)C(6)H(3), R'=I; 6 b: Ar=2,6-{4-(F(3)C)C(6)H(4)}(2)C(6)H(3), R'=I; 6 c: Ar=2,6-{3,5-(F(3)C)(2)C(6)H(3)}(2)C(6)H(3), R'=3,5-(F(3)C)(2)C(6)H(3); 6 d: Ar=2,6-{4-(F(17)C(8))C(6)H(4)}(2)C(6)H(3), R'=3,5-(F(3)C)(2)C(6)H(3); 6 e: Ar=2,6-{3,5-(F(3)C)(2)C(6)H(3)}(2)C(6)H(3), R'=I) were studied as catalyst precursors for ethylene polymerisation in supercritical CO(2). Catalyst precursors 6 a and 6 c, which are soluble in scCO(2), afford the highest polymer yields, corresponding to 2 x 10(3) turnovers. Semicrystalline polyethylene (M(n) typically 10(4) g mol(-1)) is obtained with variable degrees of branching (11 to 24 branches per 1000 carbon atoms, predominantly Me branches) and crystallinities (54 to 21 %), depending on the substitution pattern of the catalyst.
Electron transfer in biological molecules provides both insight and inspiration for developing chemical systems having similar functionality. Photosynthesis is an example of an integrated system in which light harvesting, photoinduced charge separation, and catalysis combine to carry out two thermodynamically demanding processes, the oxidation of water and the reduction of carbon dioxide. The development of artificial photosynthetic systems for solar energy conversion requires a fundamental understanding of electron-transfer reactions between organic molecules. Since these reactions most often involve single-electron transfers, the spin dynamics of photogenerated radical ion pairs provide important information on how the rates and efficiencies of these reactions depend on molecular structure. Given this knowledge, the design and synthesis of large integrated structures to carry out artificial photosynthesis is moving forward. An important approach to achieving this goal is the development of small, functional building blocks, having a minimum number of covalent bonds, which also have the appropriate molecular recognition sites to facilitate self-assembly into a complete, functional artificial photosynthetic system.