Nature of the Surface-Exposed Cytochrome-Electrode Interactions in Electroactive Biofilms of Desulfuromonas acetoxidans.

Metal-respiring bacteria are microorganisms capable of oxidizing organic pollutants present in wastewater and transferring the liberated electrons to an electrode. This ability has led to their application as catalysts in bioelectrochemical systems (BESs), a sustainable technology coupling bioremediation to electricity production. Crucial for the functioning of these BESs is a complex protein architecture consisting of several surface-exposed multiheme proteins, called outer membrane cytochromes, wiring the cell metabolism to the electrode. Although the role of these proteins has been increasingly understood, little is known about the protein-electrode interactions and their impact on the performance of BESs. In this study, we used surface-enhanced resonance Raman spectroscopy in combination with electrochemical techniques to unravel the nature of the protein-electrode interaction for the outer membrane cytochrome OmcB from Desulfuromonas acetoxidans (Dace). Comparing the spectroelectrochemical properties of OmcB bound directly to the electrode surface with those of the same protein embedded inside an electroactive biofilm, we have shown that the surface-exposed cytochromes of Dace biofilms are in direct contact with the electrode surface. Even if direct binding causes protein denaturation, the biofilm possesses the ability to minimize the extent of the damage maximizing the amount of cells in direct electrical communication with the electrode.

Voltammetric and surface-enhanced resonance Raman spectroscopic characterization of cytochrome C adsorbed on a 4-mercaptopyridine monolayer on silver electrodes.

To combine voltammetric techniques with surface-enhanced resonance Raman scattering (SERRS), cytochrome c (cyt c) was immobilized on a roughened silver electrode chemically modified with a self-assembled monolayer (SAM) of 4-mercaptopyridine (PySH). All measurements were performed on the same electrode in a homemade spectroelectrochemical cell suitable for such applications. Cyt c on a PySH-SAM shows a quasi-reversible, monoelectronic, adsorption-controlled CV response with a formal reduction potential of -0.061 V (vs SCE), which is comparable to the values found for native cyt c adsorbed on different SAMs. SERRS spectra proved that cyt c adsorbed on a PySH monolayer is present in the native conformer (the B1 state). Voltammetric and SERRS experiments at high ionic strength revealed that the interaction between the SAM and the protein is electrostatic in nature. In conclusion, PySH was found to be suitable for adsorption of cyt c at SERRS-active silver surfaces. In comparison with other SAMs, PySH requires less time (10 min vs 12-18 h) to form a long-time durable and reproducible coating on the roughened electrode surface.

[Is ischemia of the liver, lasting longer than an hour, a severity factor in hepatectomies? Apropos of 19 cases]. / L'ischémie du foie de plus d'une heure est-elle un facteur de gravité des hépatectomies? A propos de 19 cas.

Nineteen hepatic resections with continuous liver ischemia exceeding one hour (60 to 85 min, m = 68 +/- 8 min) are reported. Surgery was undertaken for 15 malignant tumors, mainly metastatic, and 4 benign tumors. In 16 out of 19 cases, a major hepatic resection was necessary to remove massive and central lesions. Vascular clamping was a Pringle maneuver (9 cases), associated with inferior vena cava clamping-complete hepatic vascular exclusion (10 cases). 2050 +/- 2000 ml of packed red cells were infused peroperatively. No operative nor hospital mortality was recorded. Major complications developed in 6 patients: 3 intraperitoneal haemorrhages leading to complementary hemostasis of the raw surface of the liver in the first 24 hours, 1 erosive gastritis, 2 subphrenic abscesses treated by percutaneous drainage. Severe liver failure developed after left trisegmentectomy on a steatotic liver and led to emergency transplantation on the 17th day with success. Except this case, biochemical liver tests demonstrated slight and transitory alteration. Magnetic resonance imaging confirmed the rapidity of the regenerative process and liver biopsies at 6 and 12 months did not show any late changes. There is no relation between the duration of liver ischemia in the limits of this study and post operative morbidity rate, which is more influenced by the magnitude of the resection and the quality of the liver remnant.