High throughput screening of monoamine oxidase (MAO-N-D5) substrate selectivity and rapid kinetic model generation

Full kinetic models provide insight into enzyme mechanism and kinetics and also support bioconversion process design and feasibility assessment. Previously we have established automated microwell methods for rapid data collection and hybrid kinetic modelling techniques for quantification of kinetic constants. In this work these methods are applied to explore the substrate selectivity and kinetics of monoamine oxidase, MAO-N-D5, from Aspergillus niger. In particular we examine the MAO-N-D5 variant Ile246Met/Asn336Ser/Met348Lys/Thr384Asn to allow the oxidation of secondary amines Initial screening showed that MAO-N-D5 enabled the selective oxidation of secondary amines in 8 and 9 carbon rings, as well as primary ethyl and propyl amines attached to secondary amines of indolines and pyrrolidines. Subsequently we developed a first kinetic model for the MAO-N-D5 enzyme based on the ping-pong bi-bi mechanism (similar to that for the human MAO-A enzyme). The full set of kinetic parameters were then established for three MAO-N-D5 substrates namely; 3-azabicyclo[3,3,0]octane, 1-(2 amino ethyl) pyrrolidine and 3-(2,3-dihydro-1H-indole-1-yl)propan-1-amine. The models for each amine substrate showed excellent agreement with experimentally determined progress curves over a range of operating conditions. They indicated that in each case amine inhibition was the main determinant of overall reaction rate rather than oxygen or imine (product) inhibition. From the perspective of larger scale bioconversion process design, the models indicated the need for fed-batch addition of the amine substrate and to increase the dissolved oxygen levels in order to maximize bioconversion process productivity

Test of the quantumness of atom-atom correlations in a bosonic gas

It is shown how the quantumness of atom-atom correlations in a trapped bosonic gas can be made observable. Application of continuous feedback control of the center of mass of the atomic cloud is shown to generate oscillations of the spatial extension of the cloud, whose amplitude can be directly used as a characterization of atom-atom correlations. Feedback parameters can be chosen such that the violation of a Schwarz inequality for atom-atom correlations can be tested at noise levels much higher than the standard quantum limit

Bosons in Disordered Optical Potentials

In this work we systematically investigate the condensate properties, superfluid properties and quantum phase transitions in interacting Bose gases trapped in disordered optical potentials. We numerically solve the Bose-Hubbard Hamiltonian exactly for different: (a) types of disorder, (b) disorder strengths, and (c) interatomic interactions. The three types of disorder studied are: quasiperiodic disorder, uniform random disorder and random speckle-type disorder. We find that the Bose glass, as identified by Fisher et al [Phys. Rev. B {\bf 40}, 546 (1989)], contains a normal condensate component and we show how the three different factors listed above affect it.Comment: 4 pages, 4 figures (low res) v2 Title,Abstract,Introduction: changes; Figure 3: Add label to axi

2,3-Dihydroxyisovalerate production by Klebsiella pneumoniae

2,3-Dihydroxyisovalerate is an intermediate of valine and leucine biosynthesis pathway; however, no natural microorganism has been found yet that can accumulate this compound. Klebsiella pneumoniae is a useful bacterium that can be used as a workhorse for the production of a range of industrially desirable chemicals. Dihydroxy acid dehydratase, encoded by the ilvD gene, catalyzes the reaction of 2-ketoisovalerate formation from 2,3-dihydroxyisovalerate. In this study, an ilvD disrupted strain was constructed which resulted in the inability to synthesize 2-ketoisovalerate, yet accumulate 2,3-dihydroxyisovalerate in its culture broth. 2,3-Butanediol is the main metabolite of K. pneumoniae and its synthesis pathway and the branched-chain amino acid synthesis pathway share the same step of the α-acetolactate synthesis. By knocking out the budA gene, carbon flow into the branched-chain amino acid synthesis pathway was upregulated, which resulted in a distinct increase in 2,3-dihydroxyisovalerate levels. Lactic acid was identified as a by-product of the process and by blocking the lactic acid synthesis pathway, a further increase in 2,3-dihydroxyisovalerate levels was obtained. The culture parameters of 2,3-dihydroxyisovalerate fermentation were optimized, which include acidic pH and medium level oxygen supplementation to favor 2,3-dihydroxyisovalerate synthesis. At optimal conditions (pH 6.5, 400 rpm), 36.5 g/L of 2,3-dihydroxyisovalerate was produced in fed-batch fermentation over 45 h, with a conversion ratio of 0.49 mol/mol glucose. Thus, a biological route of 2,3-dihydroxyisovalerate production with high conversion ratio and final titer was developed, providing a basis for an industrial process.Key Points• A biological route of 2,3-dihydroxyisovalerate production was setup.• Disruption of budA causes 2,3-dihydroxuisovalerate accumulation in K. pneumoniae.• Disruption of ilvD prevents 2,3-dihydroxyisovalerate reuse by the cell.• 36.5 g/L of 2,3-dihydroxyisovalerate was obtained in fed-batch fermentation

Redirection of the central metabolism of Klebsiella pneumoniae towards dihydroxyacetone production

Background: Klebsiella pneumoniae is a bacterium that can be used as producer for numerous chemicals. Glycerol can be catabolised by K. pneumoniae and dihydroxyacetone is an intermediate of this catabolism pathway. Here dihydroxyacetone and glycerol were produced from glucose by this bacterium based a redirected glycerol catabolism pathway. Results: tpiA, encoding triosephosphate isomerase, was knocked out to block the further catabolism of dihydroxyacetone phosphate in the glycolysis. After overexpression of a Corynebacterium glutamicum dihydroxyacetone phosphate dephosphorylase (hdpA), the engineered strain produced remarkable levels of dihydroxyacetone (7.0 g/L) and glycerol (2.5 g/L) from glucose. Further increase in product formation were obtained by knocking out gapA encoding an iosenzyme of glyceraldehyde 3-phosphate dehydrogenase. There are two dihydroxyacetone kinases in K. pneumoniae. They were both disrupted to prevent an inefficient reaction cycle between dihydroxyacetone phosphate and dihydroxyacetone, and the resulting strains had a distinct improvement in dihydroxyacetone and glycerol production. pH 6.0 and low air supplement were identified as the optimal conditions for dihydroxyacetone and glycerol production by K, pneumoniae ΔtpiA-ΔDHAK-hdpA. In fed batch fermentation 23.9 g/L of dihydroxyacetone and 10.8 g/L of glycerol were produced after 91 h of cultivation, with the total conversion ratio of 0.97 mol/mol glucose. Conclusions: This study provides a novel and highly efficient way of dihydroxyacetone and glycerol production from glucose

Rotating BEC in an optical lattice in Uniformly frustrated Josephson Junction arrays regime: Vortex configuration formulation for ground state

We consider a rotating BEC in an optical lattices in a regime which can be mapped to the Joseohson junction arrays. In this regime, we formulate the ground state energy in terms of vortex configuration. This method give us the vortex lattice in the ground state in a natural way. We apply our result for an approximation scheme of the problem which we suppose that the coupling of the Josephson junctions are uniform. Application of method for ladder case presented and the results compared with Monte-Carlo method numerically.We discuss about restriction of method and suggest improvement for it.Comment: 6 pages, 7 figure

Case Report A Case of Acute Hepatitis E Infection in a Patient with Non-Hodgkin Lymphoma Treated Successfully with Ribavirin

We present the case of a man who, following immunosuppressive treatment for non-Hodgkin lymphoma, became infected with viral hepatitis E. Acute hepatitis E virus infection should be considered in patients with deranged liver function on a background of haematological malignancies or immunosuppression, even without travel to endemic regions. Whilst clearance is usually spontaneous in immune-competent individuals, these at-risk groups may develop a more complicated and protracted disease course. Thus awareness is important as additional treatment with ribavirin or pegylated interferon may be required, as in this case, in order to help achieve eradication

Control of an atom laser using feedback

A generalised method of using feedback to control Bose-Einstein condensates is introduced. The condensates are modelled by the Gross-Pitaevskii equation, so only semiclassical fluctations can be suppressed, and back-action from the measurement is ignored. We show that for any available control, a feedback scheme can be found to reduce the energy while the appropriate moment is still dynamic. We demonstrate these schemes by considering a condensate trapped in a harmonic potential that can be modulated in strength and position. The formalism of our feedback scheme also allows the inclusion of certain types of non-linear controls. If the non-linear interaction between the atoms can be controlled via a Feshbach resonance, we show that the feedback process can operate with a much higher efficiency.Comment: 6 pages, 7 figure

Numerical study of one-dimensional and interacting Bose-Einstein condensates in a random potential

We present a detailed numerical study of the effect of a disordered potential on a confined one-dimensional Bose-Einstein condensate, in the framework of a mean-field description. For repulsive interactions, we consider the Thomas-Fermi and Gaussian limits and for attractive interactions the behavior of soliton solutions. We find that the disorder average spatial extension of the stationary density profile decreases with an increasing strength of the disordered potential both for repulsive and attractive interactions among bosons. In the Thomas Fermi limit, the suppression of transport is accompanied by a strong localization of the bosons around the state k=0 in momentum space. The time dependent density profiles differ considerably in the cases we have considered. For attractive Bose-Einstein condensates, a bright soliton exists with an overall unchanged shape, but a disorder dependent width. For weak disorder, the soliton moves on and for a stronger disorder, it bounces back and forth between high potential barriers.Comment: 13 pages, 13 figures, few typos correcte

Cost-minimization analysis of oral versus intravenous antibiotic treatment for Klebsiella pneumoniae liver abscess

A cost-minimization analysis was conducted for Klebsiella pneumoniae liver abscess (KLA) patients enrolled in a randomized controlled trial which found oral ciprofloxacin to be non-inferior to intravenous (IV) ceftriaxone in terms of clinical outcomes. Healthcare service utilization and cost data were obtained from medical records and estimated from self-reported patient surveys in a non-inferiority trial of oral ciprofloxacin versus IV ceftriaxone administered to 152 hospitalized adults with KLA in Singapore between November 2013 and October 2017. Total costs were evaluated by category and payer, and compared between oral and IV antibiotic groups over the trial period of 12 weeks. Among the subset of 139 patients for whom cost data were collected, average total cost over 12 weeks was $16,378 (95$14,620-$18,136) for the oral ciprofloxacin group and$20,569 (95% CI, $18,296-$22,842) for the IV ceftriaxone group, largely driven by lower average outpatient costs, as the average number of outpatient visits was halved for the oral ciprofloxacin group. There were no other statistically significant differences, either in inpatient costs or in other informal healthcare costs. Oral ciprofloxacin is less costly than IV ceftriaxone in the treatment of Klebsiella liver abscess, largely driven by reduced outpatient service costs.Trial registration: ClinicalTrials.gov Identifier NCT01723150 (7/11/2012)