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Cadaverine has the potential to become an important platform chemical for the production of nylon. Previously, a system that overexpresses the Klebsiella oxytoca lysine decarboxylase in Escherichia coli was engineered. The system was optimized by codon optimization, and tuning the expression level of the gene by testing various promoters and inducer concentrations. Here, we further improved the system by optimizing the sequence located in the region of the ribosome-binding site in order to enhance translation efficiency. We also identified mutant lysine decarboxylase enzymes that demonstrated enhanced cadaverine-production ability. Together, these modifications increased cadaverine production in the system by 50%, and the system has a yield of 80% from lysine-HCl under the conditions we tested. This is the first time that a system to produce cadaverine using the lysine decarboxylase from K. oxytoca performed at a level that is competitive with the traditional systems using the E. coli lysine decarboxylases in both lab-scale and batch fermentation conditions. [ABSTRACT FROM AUTHOR]

Cadaverine, as a biogenic amine, is an important platform chemical for the production of industrial polymers, such as polyamides, polyurethanes, and nylon. Previous efforts focused on the bio-based production of cadaverine using two lysine decarboxylases of Escherichia coli CadA and LdcC. In this study, we report the biotransformation of cadaverine using a lysine decarboxylase from Klebsiella oxytoca. Codon optimization of the gene encoding this enzyme was carried on for the heterologous expression in E. coli, which led to a system that converted more than 24% lysine-HCl to cadaverine compared to the same system expressing CadA. The system was further optimized by using three different inducible promoters to control the expression of lysine decarboxylase gene of K. oxytoca in E. coli. The final optimized system converted lysine-HCl to cadaverine at a conversion rate of 0.133%/min/g. When the optimized system described above is coupled to an industrial process, the combined process has the potential to produce cadaverine with high conversion efficiency (46%) from sugar. [ABSTRACT FROM AUTHOR]

DELL'ORFANO, J., et al.: The Monolithic Fetal Pacemaker: Prototype Lead Design for Closed Thorax Deployment.Prenatal sudden cardiac death and hydrops fetalis are often due to complete heart block. However, no pacing modality exists for intrauterine application for fetal bradycardia. A prototype lead for a novel fetal pacemaker has been developed and used in a direct pacing model. It has been demonstrated that the lead can be safely and successfully deployed using a hypochondriac and transdiaphragmatic or subxiphoid approach. Pacing with ventricular capture was evident with the widening of QRS duration from50.2 ± 9.8to95.1 ± 12.8 ms (P = 0.0001). Further studies by echocardiogram revealed an increase in the pulse with pacing, confirming pacing. This study documents proof‐of‐concept for closed thorax over‐the‐wire deployment of a novel lead design applicable to fetal pacing. By combining the lead design with microcircuitry and a small power source, it is possible to create a monolithic fetal pacemaker system capable of being deployed in utero. (PACE 2003; 26[Pt. I]:805–811) [ABSTRACT FROM AUTHOR]

Pacemaker electrode surface modification by organosilane and organic self-assembled monolayer strategies creates a possible new variable in pacemaker electrode behavior. Because all of these chemical surface coatings are unstable at extremes of potential. the potential to which the electrode relaxes (between pacing pulses) becomes extremely important. The authors measured this potential for platinum (Pt) and gold (Au) relevant for their use as anode (or cathode) in a bipolar pacing system and from this potential the standard electrode potential, E° was determined. Thirty-Four determinations were made by a null current three-electrode potentiostatic technique of 2.45 mm² plutinum or gold electrodes implanted chronically in blood perfused muscle in a spontaneously breathing rat. Linear voltage sweeps were performed while monitoring current with voltage at null current determined repeatedly at varying scan rates and limits. Electrode potential varied between -388 ± 19 m V (vs Ag/Agt*)for platinum anti -388 ± 55 in V for gold electrodes. Hyteresis was observed in all sweeps (P < 0.008, Fisher's exact) and measured 61 ± 17 m V (anodic) and 25 ± 3 mV (cathodic) with steep dependence on polarity (P < 0.001, t-test). The findings were independent of the materials' electronic work function. E° versus normal hydrogen electrode (NHE) were thus -166 mV (platinum) and -166 mV (gold). Because the most common bipolar system uses platinum as anode, these results arc directly applicable to current pacing technology. Provided low thresholds are achievable with novel surface modified electrodes, the small range of variation of E°, and the particular mean value observed, are both compatible with function, provided care is used during electrode testing to avoid surface disruption. These results are significant also for biosensors that use similar surface modification methodologies. [ABSTRACT FROM AUTHOR]

The monophasic action potential (Franz) catheter is regarded as the criterion standard for high fidelity recording of a class of physiological signals. However, its signal modalation characteristics have never been reported. Broadband impedance spectroscopy was performed in perfused living rat heart in a three-electrode potentiostatic configuration to determine the filtering characteristics of the MAP and model Ag/AgCl electrode-tissue interfaces. The filter transfer function H(f) (attenuation [dB] vs log(f) [log(Hz)l) was derived for the frequency range 10 Hz-106 Hz. As a filter, the MAP interface is characterized by two ranges of filtering behavior. At high frequency the MAP interface is a high-pass filter with pass band frequency 54 kHz-549 kHz (median 321 kHz) and with --3 dB cutoff points ranging from 10 kHz to 302 kHz. In this high frequency range the transfer function is characterized by decreasing attenuation per decade. However, in the lower frequency range relevant to physiological signals (the monophasic action potential, 0.1-40 Hz), it is a severely attenuating nondiodic high-pass filter element with an average attenuation of 16.87 dB relative to passband. In this physiological range, rolloff is nonlinear with increasing attenuation per decade. While the MAP electrode and model Ag/AgCl electrodes are high-pass filters with robust transfer functions for high frequency signals in the living heart, the attenuation of signals in a frequency range relevant to in vivo physiological recording imparts extreme attenuation that may distort physiological signals unpredictably. This disadvantage may be mitigated by amplitude scaling to a calibrated pure tone signal within the physiological frequency band to recover a reproducible signal. [ABSTRACT FROM AUTHOR]

The article highlights the feasibility of manipulating biological systems to produce new fuels that support the existing transportation infrastructure in the U.S. According to the author, enthusiasm for bioethanol as an additive for petroleum-derived fuels has been driven in part by mandates in many countries to use bioethanol and by an abundant supply of corn in the U.S. He added that butanol has been generally considered a better alternative fuel than ethanol. Moreover, isoprenoid biosynthesis offers an even richer source of next-generation biofuels.