We describe a mass spectrometry (MS) analytical platform resulting from the novel integration of acoustic droplet ejection (ADE) technology, an open-port interface (OPI), and electrospray ionization ...(ESI)-MS that creates a transformative system enabling high-speed sampling and label-free analysis. The ADE technology delivers nanoliter droplets in a touchless manner with high speed, precision, and accuracy. Subsequent sample dilution within the OPI, in concert with the capabilities of modern ESI-MS, eliminates the laborious sample preparation and method development required in current approaches. This platform is applied to a variety of experiments, including high-throughput (HT) pharmacology screening, label-free in situ enzyme kinetics, in vitro absorption, distribution, metabolism, elimination, pharmacokinetic and biomarker analysis, and HT parallel medicinal chemistry.
X-ray free-electron lasers (XFELs) provide very intense X-ray pulses suitable for macromolecular crystallography. Each X-ray pulse typically lasts for tens of femtoseconds and the interval between ...pulses is many orders of magnitude longer. Here we describe two novel acoustic injection systems that use focused sound waves to eject picoliter to nanoliter crystal-containing droplets out of microplates and into the X-ray pulse from which diffraction data are collected. The on-demand droplet delivery is synchronized to the XFEL pulse scheme, resulting in X-ray pulses intersecting up to 88% of the droplets. We tested several types of samples in a range of crystallization conditions, wherein the overall crystal hit ratio (e.g., fraction of images with observable diffraction patterns) is a function of the microcrystal slurry concentration. Lastly, we report crystal structures from lysozyme, thermolysin, and stachydrine demethylase (Stc2). In addition, samples were screened to demonstrate that these methods can be applied to rare samples
A scanning-force microscope based on a single-beam gradient force optical trap was developed from the conceptual stage to the point where topographic line-scans with lateral resolution approaching 10 ...nm were demonstrated and topographic images at lower resolution but with high force sensitivity could be obtained routinely. In the simplest embodiment of this microscope, known as the optical force microscope (OFM), a dielectric probe particle is trapped in the 3-d potential well formed by a tightly focused laser beam and then scanned over the surface while deflections are monitored using the transmitted beam of the trapping laser. The operating principle of the OFM is essentially the same as the atomic force microscope (AFM) and requires nanometer-level positioning of the probe relative to the sample surface, sensing deflections of the probe within the optical trap, and a feedback loop. A prototype was assembled using the scan control electronics of the AFM and a deflection sensor previously developed in our laboratory. The prototype instrument proved that a resolution well below the theoretical limit of conventional optical microscopy could be achieved. A number of images were collected with the instrument demonstrating force sensitivity in the piconewton range. The low force constant of the optically trapped probe provides high force sensitivity. The ultimate lateral resolution limit due to thermally driven fluctuations approaches the nanometer level. The implementation of high resolution OFM requires the microfabrication of dielectric probes having sharp tips and the development of appropriate means for probe transfer from the substrate (wafer) into the optical trap. Since the maximum trapping force, or escape threshold force, above which the probe escapes from the trap is generally less than 100 pN, very sharp tips (radius of curvature $\sim$1 nm) are required to minimize tip-sample interaction forces. The results obtained so far demonstrate that OFM holds potential in biological imaging. Soft samples can be scanned under physiological conditions with probe particles chemically modified to act as 'handles' for specific molecules. Single receptor-ligand binding events can be studied, or the interaction of membrane proteins with constraints due to cytoskeletal interactions can be imaged on the surface of a living cell.
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