Förster Resonance Energy Transfer between Core/Shell Quantum Dots and Bacteriorhodopsin

An energy transfer relationship between core-shell CdSe/ZnS quantum dots (QDs) and the optical protein bacteriorhodopsin (bR) is shown, demonstrating a distance-dependent energy transfer with 88.2% and 51.1% of the QD energy being transferred to the bR monomer at separation distances of 3.5 nm and 8.5 nm, respectively. Fluorescence lifetime measurements isolate nonradiative energy transfer, other than optical absorptive mechanisms, with the effective QD excited state lifetime reducing from 18.0 ns to 13.3 ns with bR integration, demonstrating the Förster resonance energy transfer contributes to 26.1% of the transferred QD energy at the 3.5 nm separation distance. The established direct energy transfer mechanism holds the potential to enhance the bR spectral range and sensitivity of energies that the protein can utilize, increasing its subsequent photocurrent generation, a significant potential expansion of the applicability of bR in solar cell, biosensing, biocomputing, optoelectronic, and imaging technologies

Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions

Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications

Bacteriorhodopsin protein hybrids for chemical and biological sensing

Bacteriorhodopsin (bR), an optoelectric protein found in Halobacterium salinarum, has the potential for use in protein hybrid sensing systems. Bacteriorhodopsin has no intrinsic sensing properties, however molecular and chemical tools permit production of bR protein hybrids with transducing and sensing properties. As a proof of concept, a maltose binding protein-bacteriorhodopsin ([MBP]-bR) hybrid was developed. It was proposed that the energy associated with target molecule binding, maltose, to the hybrid sensor protein would provide a means to directly modulate the electrical output from the MBP-bR bio-nanosensor platform. The bR protein hybrid is produced by linkage between bR (principal component of purified purple membrane [PM]) and MBP, which was produced by use of a plasmid expression vector system in Escherichia coli and purified utilizing an amylose affinity column. These proteins were chemically linked using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), which facilitates formation of an amide bond between a primary carboxylic acid and a primary amine. The presence of novel protein hybrids after chemical linkage was analyzed by SDSPAGE. Soluble proteins (MBP-only derivatives and unlinked MBP) were separated from insoluble proteins (PM derivatives and unlinked PM) using size exclusion chromatography. The putatively identified MBP-bR protein hybrid, in addition to unlinked bR, was collected. This sample was normalized for bR concentration to native PM and both were deposited onto indium tin oxide (ITO) coated glass slides by electrophoretic sedimentation. The photoresponse of both samples, activated using 100 Watt tungsten lamp at 10 cm distance, were equal at 175 mV. Testing of deposited PM with 1 mM sucrose or 1 mM maltose showed no change in the photoresponse of the xiv material, however addition of 1 mM maltose to the deposited MBP-bR linked hybrid material elicited a 57% decrease in photoresponse indicating a positive response for targeting of maltose. This chemically linked MBP-bR hybrid protein, with bacteriorhodopsin, as a photoresponsive transducing substrate, shows promise for creation of a universal sensing array by attachment of other pertinent sensing materials, in lieu of the maltose binding protein utilized. This strategy would allow significant reduction in sensor size, while increasing responsiveness and sensitivity at nano and picomolar levels

DNA Persistence in a Sink Drain Environment.

Biofilms are organized structures composed mainly of cells and extracellular polymeric substances produced by the constituent microorganisms. Ubiquitous in nature, biofilms have an innate ability to capture and retain passing material and may therefore act as natural collectors of contaminants or signatures of upstream activities. To determine the persistence and detectability of DNA passing through a sink drain environment, Bacillus anthracis strain Ames35 was cultured (6.35 x 107 CFU/mL), sterilized, and disposed of by addition to a sink drain apparatus with an established biofilm. The sink drain apparatus was sampled before and for several days after the addition of the sterilized B. anthracis culture to detect the presence of B. anthracis DNA. Multiple PCR primer pairs were used to screen for chromosomal and plasmid DNA with primers targeting shorter sequences showing greater amplification efficiency and success. PCR amplification and detection of target sequences indicate persistence of chromosomal DNA and plasmid DNA in the biofilm for 5 or more and 14 or more days, respectively

Closed loop optimal control enabled micro-force sensors

This paper presents a closed loop optimal control enabled force sensing technology in micromanipulation and microassembly. The developed micro-force sensor is based on a cantilevered beam structure with piezoelectric polyvinylidene fluoride (PVDF) actuating/sensing layers symmetrically bonded over its entire surfaces. In this type sensors, when an external load is applied, the deformed PVDF sensing layer detects the force signal and feed it through a Linear Quadratic Regulator (LQR) optimal servoed controller to the PVDF actuating layer, as a result, a closed feedback loop can be formed when a balance force is generated by the actuating layer within the sensor to balance the externally applied load, making the moving tip of the highly sensitive sensor remain in its equilibrium position. Once balanced, the sensor stiffness is virtually improved, so that accurate motion control of the moving part of the sensor can be attained. Furthermore, the applied force can also be achieved from the balance force in real time. This closed loop optimal control enabled force sensors can greatly enlarge the dynamic range of the micro-force sensor and will enhance manipulability during micromanipulation/microassembly when the sensor is mounted to the end-effector. © 2005 IEEE.Link_to_subscribed_fulltex

Development of pneumatic end effector for micro robotic manipulators

In this paper, a micro pneumatic end-effector for micromanipulation and microassembly with in-situ PVDF sensing is designed and calibrated. The micro pneumatic end-effector system consists of a DC micro-diaphragm pump and compressor, two regions of flexible latex tubes with different parameters and different function such as microtool and air channel. Effectively controlling the suction force and pressure are critical for the performance of the micro-pneumatic end-effector for micromanipulation and microassembly. The force sensing model was developed for the pneumatic end-effector system. An effective calibration method is proposed and its results verify the behavior of the developed pneumatic end-effector system. Ultimately the technology will provide a critical and major step towards the development of automated manufacturing process for batch assembly of micro devices, and also enhance micromanipulation. © 2005 IEEE.Link_to_subscribed_fulltex

Digital capillary electrophoresis gel image from LabChip GX acquired using HT DNA Hi Sens(itivity) Reagent Kit.

<p>Sample wells contain, from left to right: LabChip GX Ladder, No-Template Control, Control Isolated <i>Bacillus anthracis</i> strain Ames35 DNA, Day 1 Autoclaved Sample prior to disposal, Day 1 Bleached Sample prior to disposal, 6-round 1 testing samples (Day 2, Day 3, Day 5, Day 6, Day 10 & Day 14 Samples.), and 4-round 2 testing samples (Day 3, Day 11, Day 21 & Day 22 Samples). Duplicate PCR amplification sample data for each time point obtained, but not shown.</p