You're Visitor
The Electron Microscopy Laboratory has existed in the Department of
Biology at NCC since 1970. The first instrument obtained in that year, which is still
operational, was a Hitachi HS-8-2 Transmission Electron Microscope (TEM). The instrument
was obtained through a vocational education (VEA) grant which led to the development of a
course in Transmission Electron Microscopy (BIO 221) by Dr. James Averett. Dr. Averett
initially offered faculty instruction in the use of the TEM followed by offering the
course to students for the first time in the spring 1979 semester. Prof. Stephen Beck, the
current course coordinator, has been teaching the course since the spring 1986 semester.
In 1995, a Philips EM-300 (TEM), was donated to NCC by the EMSL corporation. Installation
is expected in the spring 1996 semester for use in the future BIO 221 courses.
Recently (April, 1992), the department was fortunate to acquire a new, state-of-the-art,
Scanning Electron Microscope (SEM), a Hitachi S-2400, through a matching National Science Foundation,
Instrumentation for Laboratory Improvement (ILI) grant, coauthored by Prof. Beck and
Dr. Baruch May. As a result of the new SEM, Prof. Beck has developed a course in Scanning
Electron Microscopy (BIO 222) which has been offered and run very successfully numerous
times, beginning with the 1992 summer session. Another aspect of the grant project has
been the integration of electron microscopy into the biology department curriculum.
Currently, the integration process is well underway, with Prof. Beck providing guided
tours of the facility to many departmental classes at all levels. Prof. Beck also provides
tours to area middle schools and high schools. The final aspect of the grant project
involves the development of an A.S. program in Electron Microscopy/Biological Research
Technology which is being coordinated by Prof. Beck and Dr. Patricia Cassin.
Since courses in electron microscopy are generally available only at the
graduate level, our students are provided with a unique opportunity to view cellular
structure at the molecular level, and from an understanding of molecular structure, to
better comprehend biological function/processes. Both TEM and SEM courses are taught with
a theoretical and "hands-on", skills emphasis. This approach provides students
who complete the courses, the competence to function as technicians in an electron
microscopy biological research laboratory.
Both instruments (TEM/SEM) utilize a high voltage generated electron beam and
electromagnetic lenses, to focus the beam, in order to yield high resolution, detailed
images at the near atomic/molecular level.
Since the mid 1950's, with the refinement of biological specimen preparatory techniques,
the TEM has revolutionized the way biologists view and understand the cell. The word
"Transmission" indicates that the electron beam passes through the specimen such
as light passes through the specimen in a light microscope. In order that the electron
beam pass through the specimen, the samples must be cut ultrathin, less than 1/10,000 of a
millimeter, using a diamond or glass fracture knife and a precision machine called an
ultramicrotome. The specimens are stained using heavy metals in order to generate contrast
on the TEM fluorescent viewing screen. The techniques of specimen preparation are tedious
with the utmost of care taken to avoid contamination. In the BIO 221 course, students
acquire these skills and put them to use on their required projects.
In the mid 1960's, the SEM became available commercially. Using a beam of electrons which
scans the surface of a specimen, the SEM produces an indirect image of the surface based
on specimen topography/relief, on a cathode ray tube (TV monitor). Interaction of the
primary electron beam with the specimen surface causes the generation of what are known as
secondary electrons (and other energetic phenomena), or the signal. The secondary electron
signal is collected and channeled to the viewing CRT in order to form a point by point
image. The generation of contrast (dark vs. light vs. gray areas) is based on specimen
surface topography. High areas of relief are contacted most directly by the primary
electron beam and produce greater signal, therefore appearing brighter than low areas of
relief, which appear darker on the viewing screen. Due to an extremely high depth of field
in the SEM, the high resolution images appear virtually three-dimensional.
Specimen preparation for SEM is generally less involved than for TEM. Since the electron
beam does not have to pass through the specimen in SEM, there is no need for ultrathin
sectioning. Larger samples can be used which are often coated with metals such as gold,
since biological samples are mainly insulators. The extremely thin gold coating is
provided to enhance conductivity and produce a greater signal. Our BIO 222 course involves
SEM specimen preparatory techniques and instruction on the proper usage of the SEM to
yield a required SEM portfolio of a variety of biological and other samples.
The main limitation to using TEM/SEM for imaging biological samples is that both
microscopes operate only in a vacuum environment. This means that any biological samples
observed must be dead. A biologist would certainly prefer to observe living processes at
this molecular level. Since the samples must be observed under a vacuum, chemical fixation
must be performed to kill and preserve the cells in as "near to life" conditions
as possible.
Although living samples cannot be studied, the ability to observe the cell through this
"molecular window" has had a profound effect on the field of biology. Biological
publications at all levels contain numerous electron photomicrographs in support of
various ideas.
With organizations such as the National Science
Foundation stressing support for two-year colleges and stimulating students with
innovative, "hands-on" laboratory courses, the future of electron microscopy at
NCC seems bright. Current plans include writing additional equipment grants for upgrading
the facility with a modern TEM and an X-ray analysis and digital computerized imaging,
archiving and analysis attachment to the SEM. The immediate future plan involves the
development of a SUNY registered program, similar to programs which exist at two-year
colleges in California (San Joaquin Delta College) and Wisconsin (Madison Area Technical
College).
TRANSMISSION
ELECTRON MICROSCOPY (BIO. 221)
SCANNING ELECTRON MICROSCOPY (BIO. 222)
Complete Course Descriptions and Current Semester Offerings Can Also Be Accessed
From The NCC HomePage.
For Additional Information, You Can Contact Prof.
Stephen Beck by email or
telephone (516) 572-7829.