Microscopy -- Introduction

Biochemical analysis is frequently accompanied by microscopic examination of tisse , cell or organelle preparations. Such examinations are used in many different applications; for example, to evaluate the integrity of samples during an experiment, to map the fine details of the spatial distribution of macromolecules within cells, or to directly measure biochemical events within living tissues.

There are two fundamentally different types of microscope; the light microscope and the electron microscope.Light microscopes use a series of glass lenses to focus light in order to form an image whereas electron microscopes are electromagnetic lenses to focus a beam of electrons. Light microscopes are able to magnify to a maximum of approximately 1500 times whereas electron microscopes are capable of magnifying a maximum of approximately 200000times.

Magnification is not, however, the best measure of a microscope. Rather resolution, the ability to distinguish between two closely spaced points in a specimen, is much more reliable estimate of a microscope’s utility. Light microscopes have a resolution limit of about 0.5 micrometres (um) for routine analysis. In contrast, electron microscopes have a resolutions of up to 1 nanometre (nm). Both living and dead specimens are viewed with an electron microscope, and often in real color, whereas only dead ones are viewed with an electron microscope, and never in real color. Recent advancements have improved upon the 0.2um resolution limit of the lgith microscope for some special applications.

Applications of the microscope in biochemtry may be relatively simple and routine; for example, a quick check of the status of a cell preparation or of cells growing in tissue culture. Here, a simple bench-top