The ability to attach fluorescent molecules onto proteins has allowed specific localization of these proteins within living cells. The traditional approach has been to purify the protein of interest then attach a fluorescent (or another useful tag) molecule in vitro, then somehow introduce the labeled protein into the cell. Whereas this and related techniques have been very useful, there are limitations because each of these three steps is often difficult. Wouldn't it be great if we had a “lock and key” system whereby a protein of interest could be modified to be a specific “lock” and a small tsggable molecule (the “key“) could diffuse into the cell and plug specifically into the lock? Albert Griffin, Stephen Adams, and Roger Tsien have developed such a system

We know that material within a cell is “packaged” within the Golgi apparatus. These “packages” (vesicles) bud off from the trans face of the Golgi and proceed to their destination. Just what drives this budding off process is closer to being understood, thanks to a recent report by Steven Jones, Kathryn Howell, John Henley, Hong Cao, and Mark McNwen. They presented morphologic and biochemical evidence that dynamin plays a role in this process.

The dynamins are a family of 100-kD guanosine triphosphatases that are thought to be involved in the budding off of vesicles from the plasma membrane during endocytosis. Whereas some forms of dynamin are restricted to specific cells, such as neurons, the form known as dynamin II (Dyn2) is present in all tissues, including epithelium.

It has been dogma for more than a hundred years that the light microscope cannot resolve structures that are much closer together than the length of the wavelength of light. This limit is on the order of a few hundred nanometers. This rule was “broken” by using the electron beam as the illumination source. The shorter wavelength of the electron beam gave correspondingly better resolution, down in the nanometer range. The rule was “broken” again when non-optical scanning probe microscopes (such as the scanning tunneling and atomic force microscopes) were developed. This technology gave us resolution in the sub-nanometer range, imaging individual atoms and molecules. However, scanning probe microscopes scan the surface of the specimen, excluding what's underneath from our view.

There are scores of microscopes that detect different properties of a specimen. Typically we image ‘visible” properties, but, for example, even the commonly-used atomic force microscope detects physical interactions rather than “visible” characteristics, Mostafa Fatemi and James Greenleaf have introduced the principle of imaging the elastic features of a specimen. This is done with sound waves, but we are not talking about just another acoustic microscope.

The method demonstrated by Fatemi and Greenleaf uses radiation force to image the acoustic response of a specimen to mechanical excitation. The mechanical excitation results from focusing two coaxial and confocal ultrasound beams of slightly different frequencies onto a selected region of the specimen.

There are three ways that objects can react to microwave energy within a microwave cavity:

1. 1. They can absorb microwave enengy. This is the case with all polar molecules (substances with positive and negative ionic poles). Examples include water, alcohols and biological specimens. Objects which absorb microwave energy will get hot as a result. The total amount of microwave absorbing material within the miaowave cavity is called the “load.”

2. 2. They can reflect microwaves. This is the case with metals. The function of the medal walls which make up a microwave cavity is to keep the microwave energy within the cavity. The metal walls themselves will not get hot.

3. 3. They can be “microwave-transparent.” This is the case with many non-polar molecules, such as paraffin and many plastics. Objects which ane microwave transpanent will heet very poorly in a microwave.

The chemical analysis of secretory vesicles has long been limited by the fact that many vesicles are analyzed together, resulting in an averaging of a population. Differences between vesicles within that population could not be detected. Wouldn't it be great if vesicles could be analyzed one at a time? You guessed it, this breakthrough has been recently achieved.

The technique of capillary electrophoresis (CE) was modified by Daniel Chiu, Sheri Lillard, Richard Scheller, Richard Zare, Sandra Rodriguez-Cruz, Evan Williams, Owe Orwar, Mats Sandberg, and Anders Lundqvist so that vesicles could be probed singly.

The atomic force microscope (AFM) is proving to be as much a tool as an imaging device. Recently, Stefan Thalhammer, Robert Stark, Stefan Müller, Johannes Wienberg and Wolfgang M. Heckl have added another useful technique to this repertoire. They demonstrated that the AFM can be used to cut out an identified section of DNA and then extract that section for amplification.

They began by flow sorting chromosomes, and then increased the specific amount of the target DNA with a “pre-set” in situ hybridization with chromosome-specific DMA to provide a specimen rich in chromosome 2. To identify the target area, selected chromosomes were examined with the AFM in the non-contact mode using stiff cantilevers.

When I see a drawing by an earty microcopist, I am often Impressed by the amount of detail they illustrated. I am frequently amazed by the resolution they apparently were able to achieve with primitive (by today's standards) unconected optics. Were their instruments and observational skills realty that good, or were they just lucky, correctly guessing what was beneath their lens? In an amazing pictorial published in the April issue of Scientific American, Brian Ford convincingly answers this question.

Ford describes the controversies surrounding descriptions by Antony van Leeuwenhoek in 1674 and Robert Brown in 1827. Both of these pioneer microscopists were often dismissed by their contemporaries and ignored for many years after their deaths. Leeuwenhoek was considered to be a man of fertile imagination whose observations of “animalcules” in pond slime were not appreciated until the time of Louis Pasteur.

The size and precision af a tissue sample has always been a concern. As it has become possible to analyze smaller and smaller samples with molecular techniques, one must be increasingly concerned that the sample is what we think it is. So how do you dissect out a specific cell or a small group of cells? Whereas several techniques have been suggested, a group at the National Institutes of Health (NIH) have come up with an ingenious solution. Robert Bonner, Michael Emmert-Buck, Kristina Cole, Thomas Pohida, Rodrigo Chuaqui, Seth Goldstein, and Lance Liotta have published a technique they have termed Laser Capture Microdissection (LCM).

With LCM, Bonner et. al. have demonstrated that a specific cell can be identified and transferred to an appropriate container for molecular analysis. Using the polymerase chain reaction (PCR), the genetic material from a single cell can be amplified for analysis. However, data from several cells (about 20) needs to be examined so that variations in the cell cycle, etc., can be averaged.