Changes in the Protein Profile of Streptomyces griseus during a Cycloheximide Fermentation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75202/1/j.1749-6632.1987.tb23846.x.pd

Screening and Separation of Β-Lactam Antibiotics Using Protein-engineered Enzymes a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75463/1/j.1749-6632.1990.tb18182.x.pd

Middle and posterior cardiac veins: An underused option for ventricular pacing

Tarrasó, Olga;Fuente Fuente, Carlos;Reventós, Manue

Millimetre-long transport of photogenerated carriers in topological insulators.

Excitons are spin integer particles that are predicted to condense into a coherent quantum state at sufficiently low temperature. Here by using photocurrent imaging we report experimental evidence of formation and efficient transport of non-equilibrium excitons in Bi2-xSbxSe3 nanoribbons. The photocurrent distributions are independent of electric field, indicating that photoexcited electrons and holes form excitons. Remarkably, these excitons can transport over hundreds of micrometers along the topological insulator (TI) nanoribbons before recombination at up to 40 K. The macroscopic transport distance, combined with short carrier lifetime obtained from transient photocurrent measurements, indicates an exciton diffusion coefficient at least 36 m2 s-1, which corresponds to a mobility of 6 × 104 m2 V-1 s-1 at 7 K and is four order of magnitude higher than the value reported for free carriers in TIs. The observation of highly dissipationless exciton transport implies the formation of superfluid-like exciton condensate at the surface of TIs

Hydrogen peroxide production using chemically treated Pichia pastoris cells

A new method has been developed to prepare intact cell systems to produce hydrogen peroxide (H2O2) using methylotrophic yeast Pichia pastoris. The high alcohol oxidase (EC 1.1.3.13; AOXase) content in the living P. pastoris cells is always associated with high activity of catalase (about 200- to 400-fold higher than that of AOXase) to protect the cells from oxidative damage from H2O2. To obtain catalasefree intact cells, a combination of a cationic detergent, cetyldimethylbenzyl-ammonium chloride (Cation M2), to permeabilize the cell membrane and a ctalase inhibitor, sodium azide, was used to selectively release and inactivate the cellular catalase. This chemical treatment released more than 50% of the cellular protein including the inactivated catalase, thus increasing more than twofold the specific cellular AOXase activity. In addition, the cells were made more permeable to the reacting substrates. Using chemically treated P. pastoris YB4290 cells, 10 m of H2O2 was produced from 10 m methanol (Tris-HCl buffer, pH 7.5) in 4 h at 15[deg]C. In the presence of pure oxygen instead of air, 50-80 m of H2O2 was produced in 3 h at a maximum rate of 2.6 g-1 (dry cell wt.) h-1. The cells maintained half of the initial enzyme activity after five repeated-batch experiments at 15[deg]C.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31849/1/0000798.pd

Schottky Electric Field Induced Circular Photogalvanic Effect in Cd3As2 Nanobelts

Dirac semimetals are expected to forbid the manifestation of the circular photogalvanic effect (CPGE) because of their crystal inversion symmetry. Here, we report the observation of the CPGE in Cd3As2 nanobelt field effect transistors, when the photoexcitation is focused in the vicinity of the metal contacts up to room temperature. We attribute the CPGE to the Schottky electric field induced symmetry breaking, which results in the photocurrent modulation by circularly polarized photoexcitation via spin-momentum locking. The hypothesis is supported by a suite of experiments including spatially and angularly resolved helicity dependent photocurrent, Kelvin probe force microscopy, and gate voltage dependence. First principles calculations confirmed a topological phase transition upon field induced structural distortion. This work provides key insights on the electrically controlled helicity dependent optoelectronics in Dirac materials

Effects of extractive fermentation on butyric acid production by Clostridium acetobutylicum

The addition of an oleyl alcohol extractant to a batch fermentation of glucose by Clostridium acetobutylicum resulted in a concentration profile that was distinctly different from the non-extractive control fermentation. The concentration of butyric acid increased and subsequently decreased in the control fermentation. The concentration of butyric acid increased but did not subsequently decrease in the oleyl alcohol extractive fermentation. The production of butyric acid was found to have been prolonged into the solventogenic phase in the oleyl alcohol extractive fermentation. Butyric acid was continually replenished from glucose while it was being converted to butanol. Supplementation of exogenous acetic and butyric acids, the metabolic uncoupler carbonyl cyanide 3-chlorophenylhydrazone, or decanol to the oleyl alcohol extractive fermentation helped to reinstate the normal butyric acid concentration profile. These findings are discussed with respect to the effects of these additives on the ΔpH of C. acetobutylicum and its importance with regard to the production of butyric acid.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46760/1/253_2004_Article_BF00903771.pd

Protein release from Escherichia coli cells permeabilized with guanidine–HCl and Triton X100

An important factor complicating the recovery of recombinant proteins from Escherichia coli is their intracellular location. An alternative to the commonly used method of releasing these proteins by mechanical disruption is to chemically permeabilize the cells. The objective of this research was to characterize the protein release kinetics of a permeabilization process using guanidine–HCl and Triton X100. The protein release rate and yield were determined as a function of the guanidine and Triton concentrations. The initial release rate increased monotonically with increasing concentrations of Triton and guanidine whereas the release yield varied in a complex manner. Electron microscopy indicated that the permeabilization process involves a solubilization of the inner membrane and molecular alteration of the outer wall. Some advantages of this process over mechanical disruption include avoiding extensive fragmentation of the cells and retainment of nucleic acids inside the cell structure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37899/1/260330712_ftp.pd