(1R*,2S*,4S*,5R*)-Cyclo­hexane-1,2:4,5-tetra­carb­oxy­lic dianhydride

The title compound, C10H8O6, a promising raw material to obtain colorless polyimides which are applied to microelectronic and optoelectronic devices, adopts a folded conformation in which the dihedral angle between the two anhydro rings is 55.15 (8)°. The central six-membered ring assumes a conformation inter­mediate between boat and twist-boat. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions, forming a layer parallel to the bc plane

(1S*,2S*,4R*,5R*)-Cyclohexane-1,2,4,5-tetracarboxylic acid

The title compound, C10H12O8, a prospective raw material for colourless polyimides which are applied to electronic and microelectronic devices, lies about an inversion centre and the cyclohexane ring adopts a chair conformation. Two crystallographycally independent carboxylic acid groups on adjacent C atoms are in equatorial positions, resulting in a mutually trans conformation. In the crystal, O—H...O hydrogen bonds around an inversion centre and a threefold rotoinversion axis, respectively, form an inversion dimer with an R22(8) motif and a trimer with an R33(12) motif

Alterations of Cellular Physiology in Escherichia coli in Response to Oxidative Phosphorylation Impaired by Defective F(1)-ATPase

The physiological changes in an F(1)-ATPase-defective mutant of Escherichia coli W1485 growing in a glucose-limited chemostat included a decreased growth yield (60%) and increased specific rates of both glucose consumption (168%) and respiration (171%). Flux analysis revealed that the mutant showed approximately twice as much flow in glycolysis but only an 18% increase in the tricarboxylic acid (TCA) cycle, owing to the excretion of acetate, where most of the increased glycolytic flux was directed. Genetic and biochemical analyses of the mutant revealed the downregulation of many TCA cycle enzymes, including citrate synthase, and the upregulation of the pyruvate dehydrogenase complex in both transcription and enzyme activities. These changes seemed to contribute to acetate excretion in the mutant. No transcriptional changes were observed in the glycolytic enzymes, despite the enhanced glycolysis. The most significant alterations were found in the respiratory-chain components. The total activity of NADH dehydrogenases (NDHs) and terminal oxidases increased about twofold in the mutant, which accounted for its higher respiration rate. These changes arose primarily from the increased (3.7-fold) enzyme activity of NDH-2 and an increased amount of cytochrome bd in the mutant. Transcriptional upregulation appeared to be involved in these phenomena. As NDH-2 cannot generate an electrochemical gradient of protons and as cytochrome bd is inferior to cytochrome bo(3) in this ability, the mutant was able to recycle NADH at a higher rate than the parent and avoid generating an excess proton-motive force. We discuss the physiological benefits of the alterations in the mutant