The atomic force microscope (AFM) is being utilized in even more clever ways to reveal details of molecular structure and function. As an example, Julio Fernandez and Hongbin Li have used the AFM in the force-clamp mode to monitor the folding trajectory of a single protein. They have demonstrated in a unique way in which a single protein behaves when put under tension, and then what happens when the tension is relieved.

Fernandez and Li linked several molecules of ubiquitin, a small protein, together to form a polyubiquitin chain. With one end of the chain attached to a substrate, the tip of a soft cantilever of the AFM attached to a single protein, and from one to nine ubiquitin molecules were picked up.

Whether you encounter electron powder diffraction patterns everyday, or run across them only rarely, interpreting them may require a bit of preparation. But it's easy to lose track of the numbers for your microscope's camera constant, not to mention the bewildering array of lattice parameters and symmetries that one may encounter in the microscope. In that context, we describe overlays you might want to assemble for measuring camera constants, and for recognizing crystal systems most likely to yield electron powder diffraction patterns in your lab. Pulling this out of a drawer and/or computer folder thereafter might help you come up with quick answers, even if you haven't thought about analyzing diffraction data for quite a while.

The late 1940s marked the appearance of the first publications using transmission electron microscopy (TEM) and by 1950, with improved embedding and sectioning methodology, reports began to include mammalian tissues (PubMed). However, 15 years lapsed before morphometry and stereology were integrated into TEM studies (Loud 1965; Elias 1971; Weibel 1969). The utility of a quantitative approach to electron microscopy was obvious, but its popularity has waxed and waned considerably over the last half century; its staunch supporters, however, have stayed the course (Weibel 2001; Diaspro 2004). Early computers, though slow and unreliable, brought some degree of automation to morphometry in the 1980s, but did little to ease tedium or increase accuracy (Caruntu 2002).

In the previous article (part 1), the procedure for setting the computer screen was discussed by using Adobe Gamma in the control panel. Adobe Gamma is also found on the drive where the system is installed. Click on Program Files > Common Files > Adobe > Calibration > Adobe Gamma.cpl. Double click to launch the gamma control wizard. On a Macintosh the Apple Calibration Utility can be used.

The merits of using ink jet printers were also discussed. Merits include low cost (though costs escalate with the purchase of cartridges), high quality prints from any application, and the technology of a fine spray with higher image resolution as opposed to a laser jet printer and Tektronix Phasers (these printers separate images into dots at compromised resolutions).

Bacteria contain a wealth of mechanisms that organize their internal and external components into a highly polar structure, frequently with distinctive shape, and constrain certain metabolic functions to particular parts of the cell. For example, cell division generally takes place at the middle of the cell, and a host of interacting proteins are involved in ensuring that the division site is positioned properly. Thus, in spite of the lingering perception among some scientists that these cells are simply bags of freely diffusing enzymes, there is much to be learned from ultrastructural studies. Light microscopy has given evidence of cytoskeletal components that presumably establish and maintain cell shape and participate in cell division.

Sample preparation for Transmission Electron Microscopy (TEM) is usually performed such that the final sample orientation is either a cross section or a plan view of the bulk material, as shown schematically in Figure 1. The object of any sample preparation technique, for either of these two orientations, is to thin a selected volume of the sample from its initial bulk state to electron transparency, ~ 100nm thick. In doing so, the final sample must be mechanically stable, vacuum compatible, and, most of all, unchanged from the initial bulk material. Many techniques have been used to achieve this goal: cleaving, sawing, mechanical polishing, chemical etching, ion milling, focused ion beam (FIB) milling, and many others.

Confocal Holography is a combination of two well known concepts: confocal microscopy and light (laser) holography. Confocal microscopy places an aperture at a conjugate focus to the specimen focus. This filters any rays that are not on the focus plane, allowing a 3-dimensional image of the specimen to be built up over a set of planes.

Holography is the measurement of both the amplitude and phase characteristics of light. Typically most methods only measure the amplitude of the image. The phenomenon of interference allows the determination of the phase shift for a coherent source as well. The phase information is directly related to the index of refraction of a material, which in turn is a function of the temperature and composition.

Electron microscopy (EM) is an indispensable tool for the study of ultrastructures of biological specimens. Every electron microscopist would like to process biological specimens for either scanning electron microscopy (SEM) or transmission electron microscopy (TEM) in a way that the specimens viewed under the electron microscope resemble those seen in vivo or in vitro under the light microscope. This is, however, often easier said than done because biological tissue processing for EM requires careful attention of the investigator with regard to the numerous processing steps involved in specimen preparation, such as fixation, dehydration, infiltration, embedding, and sectioning.

Salary Surveys always create considerable interest. Although a less formal study was conducted several years ago via the Microscopy Society listserver, the authors are not aware of a complete study since the one conducted by the MSA nearly 20 years ago. The current study followed a format frequently used by Microscopy/Microscopy Education (MME), typically delivered at microscopy-related scientific meetings to gather trends on new and existing instrumentation. It was mailed the middle of 2004 to nearly 15,000 US readers of Microscopy Today. Returns were collected and processed by an independent contractor.

Since we do a lot of small-sample critical-point drying (CPD) for SEM, we assemble our own drying capsules which can be manufactured easily in quantity. Materials' cost at current prices is about $10 for 50 capsules. About 25 capsules can be manufactured in an hour. The completed capsule consists of a small polypropylene chamber with fine-mesh, stainless-steel screen caps at each end that allow easy exchange of solvents. shows the steps ofthe assembly process. The base of one capsule is cut off with a razor blade, the cap of a second capsule, for a bottom (Figure 1a). Chamber length can be 5 to 14mm. One-quarter-inch holes are punched through the center of each cap using a paper punch whose spring/detente has been removed to pass the caps' rim (Figure 1b). A sheet-metal shim punch is used to create 3/8" disks of 60-mesh stainless steel wire cloth.