ESR and EPR spectrometry Protein crystallization

ESR and EPR spectrometry. Portable ESR/EPR spectrometer Model. 8400 incorporates a compact ... a digital plotter. Micro-Now. 406. Thermal analysis...
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SEM The DSM 982 Gemini scanning elec­ tron microscope is designed to pro­ vide high resolution at low beam en­ ergies for surface imaging and analysis in materials science and bio­ logical applications. The microscope has guaranteed resolution as low as 1 nm at 30 keV electron beam energy and 4 nm at 1 keV. To achieve high resolution at low beam energy, the electron optical column design includes a beam booster system and an objective lens that combines electrostatic and elec­ tromagnetic lenses. The design mini­ mizes the required electron beam diameter and stabilizes high beam currents. The microscope uses a Schottky field emission gun source and a secondary electron detector. The DSM 982 Gemini contains a large sample chamber with a motor­ ized stage that accommodates sam-

INSTRUMENTATION Low-temperature FT-IR An upgrade for the Model 2000-A MultiMode FT-IR system extends the operating temperature range for transmission, spec­ ular reflectance, and large-angle reflec­ tance IR spectroscopy down to -170 °C. The system now operates at temperatures ranging from -170 °C to 900 °C and at pressures from high vacuum to 2000 psi for all spectroscopic modes. Applications for the system include studies of surface coatings, polymers, and solid-gas reac­

tions. Aabspec • 401 Laser diffraction LS200 Series automated laser diffraction particle size analyzer has a dynamic size distribution range of 0.04 pm-2 mm. The analyzer measures the entire range in a single run without the need for changing optics or instrument settings, and data can be acquired from up to 116 size channels. Options include a dry powder module, a 434 A

pies up to 150 mm in diameter and can be tilted up to 50°. Typical analyt­ ical working distances of < 10 mm with a detection angle of 35° are pos­ sible. The microscope, which is con­ trolled by a multiprocessor computer system with an interactive user inter­ face for instrument setup and image processing, contains 4 MB of inte­ grated image storage with a maxi­ mum resolution of 2048 χ 2048

pixels. Zeiss • 402

hazardous fluids module for low-flashpoint solvents, and a microvolume module that accommodates samples of 1-50 mg and uses diluent volumes of 12 mL. Coulter

• 403

contains a 6-L batch extractor vessel that can be configured for either up- or down-flow separations. The system also includes two separation vessels. One separates gas from larger and less soluble molecules in the solute; the other separates lighter molecules and decontaminates the gas. Options for the PDU include a magnetic drive mixer module for continuous extrac­ tion of liquids, a countercurrent col­ umn for processes such as the deacidification of fatty oils, and a solvent modifier addition system for process methods development. Pressure

Products • 405 ESR and EPR spectrometry Portable ESR/EPR spectrometer Model 8400 incorporates a compact electromag­ net and performs autotuning of field pa­ rameters. The spectrometer, designed for field applications such as dosimetry and process control, can also be used for the detection of free-radical intermediates in semiconductors and radiation damage studies in living tissues and organic mate­ rials. A dedicated software package pro­ vides data manipulation and mathematical modeling functions and outputs results to a digital plotter. Micro-Now • 406

Thermal analysis

The HP 7686 PrepStation automatically dispenses, dilutes, heats, and evaporates samples prior to HPLC, GC, or MS analy­ sis. The optional SPE module performs extractions and filtrations, and both the basic and SPE systems include a barcode reader and Windows-based operating soft­ ware. The system can be integrated with the 1050 series of HPLC autosamplers or the 5890 Series II gas chromatograph, or used as a stand-alone system. Hewlett

The PL-STA simultaneous thermal ana­ lyzer performs thermogravimetric and quantitative heat flux differential scanning calorimetry on a single sample. The ana­ lyzer operates in the temperature range of -125-1640 °C. The combination of tech­ niques can be used for the interpretation of complex reactions or applications in which a secondary reaction takes place. The PL-STA has a low swept volume for enhanced sensitivity in evolved gas analy­ sis and can be used for hyphenated tech­ niques with MS and FT-IR spectrometry.

Packard • 404

Polymer Laboratories • 407

Sample preparation

Process-scale SFE

Protein crystallization

Process development unit (PDU) for SFE is designed to operate at pres­ sures of 450-700 bar and temperatures of 50-110 °C with a maximum flow rate of 1.5 kg/min at 700 bar. The PDU

The Robotic Protein Crystallization Sys­ tem II prepares protein crystals by the hanging-drop and sitting-drop techniques. A liquid-level sensor determines the sur­ face level of the protein solution, and up to

Analytical Chemistry, Vol. 66, No. 7, April 1, 1994