Placement of oppositely charged aminoacids at a polypeptide termini determines the voltage-controlled braking of polymer transport through nanometer-scale pores

Protein and solid-state nanometer-scale pores are being developed for the detection, analysis, and manipulation of single molecules. In the simplest embodiment, the entry of a molecule into a nanopore causes a reduction in the latter's ionic conductance. The ionic current blockade depth and residence time have been shown to provide detailed information on the size, adsorbed charge, and other properties of molecules. Here we describe the use of the nanopore formed by Staphylococcus aureus alpha-hemolysin and polypeptides with oppositely charged segments at the N- and C-termini to increase both the polypeptide capture rate and mean residence time of them in the pore, regardless of the polarity of the applied electrostatic potential. The technique provides the means to improve the signal to noise of single molecule nanopore-based measurements

Dendrimers in Nanoscale Confinement: The Interplay between Conformational Change and Nanopore Entrance

Hyperbranched dendrimers are nanocarriers for drugs, imaging agents, and catalysts. Their nanoscale confinement is of fundamental interest and occurs when dendrimers with bioactive payload block or pass biological nanochannels or when catalysts are entrapped in inorganic nanoporous support scaffolds. The molecular process of confinement and its effect on dendrimer conformations are, however, poorly understood. Here, we use single-molecule nanopore measurements and molecular dynamics simulations to establish an atomically detailed model of pore dendrimer interactions. We discover and explain that electrophoretic migration of polycationic PAMAM dendrimers into confined space is not dictated by the diameter of the branched molecules but by their size and generation-dependent compressibility. Differences in structural flexibility also rationalize the apparent anomaly that the experimental nanopore current read-out depends in nonlinear fashion on dendrimer size. Nanoscale confinement is inferred to reduce the protonation of the polycationic structures. Our model can likely be expanded to other dendrimers and be applied to improve the analysis of biophysical experiments, rationally design functional materials such as nanoporous filtration devices or nanoscale drug carriers that effectively pass biological pores

Recent Progress in Wafer-Fused VCSELs Emitting in the 1550-nm Band

Record-high fundamental mode output power of 1.5 mW at 100 degrees C is achieved with InAlGaAs-InP/AlGaAs-GaAs 1550 nm wavelength vertical cavity surface emitting lasers (VCSELs) produced by a modified wafer fusion technique. A broad wavelength setting on the same wafer in a spectral range of 40 nm is demonstrated with these devices. This performance positions wafer-fused 1550 nm VCSELs as prime candidates for many applications in photonics, including air-space fiber-optic communications and WDM-PON as well as in spectroscopy and sensing

1.3µm-wavelength phase-locked VCSEL arrays incorporating patterned tunnel junction

We report the fabrication and the performance of phase-locked VCSEL arrays emitting near 1310 nm wavelength. The arrays were fabricated using double wafer fusion by patterning a tunnel junction layer, which serves to define the individual single mode array elements. Phase-locking in both one-dimensional and two-dimensional array configurations was confirmed by means of far field and spectral measurements as well as theoretical modeling. CW output powers of more than 12 mW were achieved. (C) 2009 Optical Society of Americ

85 W VECSEL output at 1270 nm with conversion efficiency of 59 %

We report on 1270 nm vertical-external-cavity surface-emitting lasers (VECSELs) with up to 59% conversion efficiency and maximum output power of 8.5 W (pump limited), at 5 degrees C heat sink temperature. These VECSELs comprised wafer-fused gain mirrors in the flip-chip (thin-disk) heat dissipation scheme. The reflected pump light from the gain mirror surface was found to depend considerably on temperature and pump power. (C) 2015 Optical Society of Americ

High Fundamental Mode Power, High Speed InAlGaAs/AlGaAs 1310 and 1550-nm Wafer-Fused VCSELs

InAlGaAs/AlGaAs-based wafer-fused long-wavelength VCSELs with tunnel junction injection emitting in the 1310 nm and 1550 nm bands show high single-mode output and high speed modulation capabilities of 10 Gbps. Fundamental emission close to 6 mW at room temperature and 2.5 mW at 80 degrees C for both 1310 nm and 1550 nm devices is demonstrated for the first time. (C)2008 Optical Society of Americ