We are all familiar with the 4 groups of human blood types; 0, A, B, and AB. Each group is characterized by specific molecules on the surface of the red blood cells (RBCs). Recently, Michel Grandbois, Wolfgang Dettmann, Martin Benoit, and Hermann Gaub have modified the atomic force microscope (AFM) to use the different affinities of these molecules to produce an image.

A key step was to specifically functionalize the scanning probe tip of the AFM. What this means is to covalently attach an active molecule to the tip. The active molecule they used was a Iectin derived from the snail Helix pomatia (this is the same snail valued by the French as escargot). This Iectin binds specifically to molecules found on the surface of RBCs in blood group A (N-acetylgalactosamine-terminated glycolipids), but these molecules are not found in blood group O. But if the Iectin was bound directly to the AFM tip, nonspecific adsorption to the specimens would occur.

Why is it that tip convolution effects rotate with the scan angle in a Nanoscope-based AFM (and possibly other systems)? The tip certainly doesn't rotate in its holder as the scan angle is changed! I posed this question on the SPM mailing list, and got several answers in return, but I was still puzzled until I put all of them together and thought a while. However, I may not be the only puzzled soul out there, so let me attempt to summarize what I've come to understand:

A good way to think about this is to consider a righttriangle tip approaching a cube on a surface:

If the tip approaches the cube along the plane of the page screen, the left side of the cube will appear sharp in an AFM image and the right side of the cube will have a slant introduced into it due to a tip convolution effect.

Using illustrations from published technical articles is part of many lectures and presentation citations, and given the availability of flat bed scanners, should be easy to accomplish. The problem that remains is removing halftone patterns and other periodic noise that result from printing and scanning technology. Practically all magazines and newspapers are printed using a regular halftone pattern that uses an array of dots varied in size to produce the visual illusion of continuous gray scale. Color images are usually printed with three, four or even more such patterns using different colored inks and different pattern orientations. Scanning such images into a computer can introduce a further pattern due to the moire interference between the printed pattern and the spacing of the sensors in the scanner. Such patterns are also characteristic of images obtained from single-chip video cameras because of the color filters present in front of the light sensors on the chip.

With the advent of Mohs surgery in the dermatology clinics, making sure the margins are clear of any cancer is of the utmost importance to both patient and dermatopathologist. While the patient is still in the surgery suite, immunohistochemstry staining can be done in the laboratory microwave (Pelco microwave with water load cooler, wattage controller and temperature probe). The immunohistochemistry procedure takes only 25-30 minutes as compared to the more conventional methods that take 2 hours or more.

The microwave needs to be checked for hot spots using the Pelco #36140 microwave bulb array. Make sure the area in which you are going to put your slides has no hot spots, indicated by no illuminating bulbs. Using a Sigma Diagnostics #H6644 Humid Chamber, place a paper towel in the bottom of the chamber and fill with 1/4 inch of water. This is in addition to the water loads used to eliminate hot spots.

“I will be getting my first SEM/EDS shortly, and to obtain the required operating permit from my safety group, I need a written procedure for handling LN2. Specifically I need a written procedure for filling the 3 L dewar on the EDS detector from a 50 L dewar mounted on a cart. I plan to make the transfer by using a lab source of LN2 to pressurize the 50 L dewar and have obtained all the valves and fittings required to do this from another SEM lab. I would appreciate copies of the procedure.”

This question recently posed to the Microscopy List Server unleashed a flurry of comments, not only on the safety of various LN2 procedures but on the safety of other materials as well. Also discussed was the necessity of formal LN2 handling procedures.

To those scientists and researchers who use microscopes with video or digital cameras for the purpose of capture and display, there has always existed a fundamental problem, namely, imaging large tissue samples at high resolution.

For some time, conventional technology has allowed video cameras to be attached to microscopes. The signal generated by these cameras can be captured and saved to a computer's hard drive using a frame grabber. A typical image capture and display resolution is 640 by 480 (307,200) pixels. Although the image produced is ‘good’, it is by no means considered ‘high resolution’. For the sake of discussion, ‘high resolution’ is defined as greater than 1,000 x 1,000 (1,000,000) pixels. High resolution images are essential for medical applications. Today's modern digital cameras can meet or exceed this value. The human eye, if compared to these examples, has the equivalent resolution of greater than 5,000 x 5,000 (25,000,000) pixels.

A scanning chemical microscope utilizing a flat pH sensor has proven effective for analyzing a number of biological specimens including human teeth surfaces, plant leafs, and rice.

The key to this microscope, the “pH imaging sensor”, is an electrochemical semiconductor that can be made to function as an array of point sensors when scanned by backside laser illumination. Measured pH values at each measurement point can be processed into a pH image. So far a resolution of 5 μm with a 0.01 pH sensitivity has been attained by this imaging technology, although most images are made using 100 μm resolution. The time to acquire an image is, of course, dependent on the size of the measured area. For example, a 6.4 mm x 6.4 mm image with a resolution of 100 urn can be acquired in 25 s. Linear pH profiles can also be obtained at a speed of 1 cm/s.

Tens of thousands of Americans suffer from muscular dystrophy (MD), a disease that gradually deteriorates a person's skeletal muscle. While there is no effective cure, scientists know MD is caused by a genetic defect and are searching for treatments that will stop or retard the deterioration of muscle. In June, American and British researchers announced the success of a long-term treatment that repairs the genetic defect in Duchenne muscular dystrophy, the most common childhood form of MD.

Last fall, these researchers injected a short strand of nucleic acid into the shin muscle of a six-week old golden retriever - which had a genetic defect that leads to Duchenne MD in dogs - in order to maintain normal levels of dystrophin, the muscle protein missing in Duchenne MD. Their goal was for the nucleic acid to trigger the dog's system to correct the genetic defect. Eleven months later, the injected muscle continues to show normal levels of dystrophin.