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Adenylate kinase (AK) mediates the reversible transfer of phosphate groups between the adenylate nucleotides and contributes to the maintenance of their constant cellular level, necessary for energy metabolism and nucleic acid synthesis. The AK were purified from crude extracts of two sulfate-reducing bacteria (SRB), Desulfovibrio (D.) gigas NCIB 9332 and Desulfovibrio desulfuricans ATCC 27774, and biochemically and spectroscopically characterised in the native and fully cobalt- or zinc-substituted forms. These are the first reported adenylate kinases that bind either zinc or cobalt and are related to the subgroup of metal-containing AK found, in most cases, in Gram-positive bacteria. The electronic absorption spectrum is consistent with tetrahedral coordinated cobalt, predominantly via sulfur ligands, and is supported by EPR. The involvement of three cysteines in cobalt or zinc coordination was confirmed by chemical methods. Extended X-ray absorption fine structure (EXAFS) indicate that cobalt or zinc are bound by three cysteine residues and one histidine in the metal-binding site of the ``LID'' domain. The sequence (129)Cys-X(5)-His-X(15)-Cys-X(2)-Cys of the AK from D. gigas is involved in metal coordination and represents a new type of binding motif that differs from other known zinc-binding sites of AK. Cobalt and zinc play a structural role in stabilizing the LID domain. (C) 2008 Elsevier Inc. All rights reserved.

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In this letter, we report for the first time the use of a sheet of cellulose-fiber-based paper as the dielectric layer used in oxide-based semiconductor thin-film field-effect transis- tors (FETs). In this new approach, we are using the cellulose– fiber-based paper in an “interstrate” structure since the device is built on both sides of the cellulose sheet. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (> 30 cm2/Vs), drain–source current on/off modulation ratio of approximately 104, near-zero threshold voltage, enhance- ment n-type operation, and subthreshold gate voltage swing of 0.8 V/decade. The cellulose-fiber-based paper FETs’ character- istics have been measured in air ambient conditions and present good stability, after two months of being processed. The obtained results outpace those of amorphous Si thin-film transistors (TFTs) and rival with the same oxide-based TFTs produced on either glass or crystalline silicon substrates. The compatibility of these devices with large-scale/large-area deposition techniques and low– cost substrates as well as their very low operating bias delin- eates this as a promising approach to attain high-performance disposable electronics like paper displays, smart labels, smart packaging, RFID, and point-of-care systems for self-analysis in bioapplications, among others.

Two different ultrasonic energy sources, the sonoreactor and the ultrasonic probe, are compared for enzymatic digestion of proteins for protein identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDl-TOF-MS) using the peptide mass fingerprint (PMF) procedure. Variables such as (i) trypsin/protein ratio; (ii) sonication time; (iii) ultrasound amplitude; and (iv) protein concentration are studied and compared. As a general rule, the trypsin/protein ratio and the minimum protein concentration successfully digested are similar with both ultrasonic energy sources. Results showed that the time needed to digest proteins was shorter with the ultrasonic probe, 60 s versus 120 s, for the same amplitude of sonication, 50%. However, lower standard deviations and cleaner MALDI-TOF-MS spectra were obtained with the sonoreactor. In addition, the sonoreactor device provided higher sample throughput (6 samples for the sonoreactor versus 1 sample for the ultrasonic probe) and easier sample handling for lower sample volumes (25 mu l). Finally, a comparison of both methodologies for the specific identification of the adenylylsulphate reductase alfa subunit from a complex protein mixture from Desulfovibrio desulfuricans ATCC 27774 was done as a proof of the procedure. (c) 2007 Elsevier B.V. All rights reserved.

A biosensor for amperometric determination of nitrite was developed using cytochrome c nitrite reductase (ccNiR) from Desulfovibrio desulfuricans immobilized and electrically connected on a glassy carbon electrode by entrapment into redox active [ZnCr-AQS] layered double hydroxide containing anthraquinone-2-sulfonate (AQS). The transduction step corresponded to the electro-enzymatic reduction of nitrite by immobilized AQS molecules at -0.6 V. The biosensor showed a fast response to nitrite (5 s) with a linear range between 0.015 and 2.35 mu M, a sensitivity of 1.8 A M-1 cm(-2) and a detection limit of 4 nM. The apparent Michaelis-Menten constant (K-M(app)) M was 7.5 mu M. (c) 2007 Elsevier B.V. All rights reserved.

Three ultrasonic energy sources were studied to speed up the sample treatment for in-solution protein identification by peptide mass fingerprint using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Protein reduction, alkylation, and enzymatic digestion steps were done in 15 min. Nine proteins, including zinc resistance-associated protein precursor from Desulfovibrio desulfuricans strain G20 and split-soret cytochrome c from D. desulfuricans ATCC27774 were successfully identified with the new protocol.