Joseph Uknalis, Biologist
. . . focused on improving resolution and enhancing our understanding of problems in agriculture and food safety . . .
Surface of a microbe, E. coli
Fluorescence from cantaloupe
Corn starch granules
The Microscopic Imaging facility at the Eastern Regional Research Center is one of several groups in Core Technologies currently administered by the Office of the Center Director. The facility has a distinguished record of research support extending over the Center's fifty years of operation; early results obtained with our first electron microscope on the basic structure and composition of cattle hide and leather collagen and bovine milk helped earn an international reputation for ERRC research programs, and recently, major investments in shared modern imaging instruments, ensure continued improvement in resolving important agricultural and food safety problems at the Center through multi-disciplinary research.
The mission of the facility is to provide research support, collaboration and training in modern integrated imaging to a diverse scientific staff. Four sophisticated microscope systems are used in coordinated studies aimed at, for example, analyses of the intricate molecular structure of new and improved food products, or quantitative and qualitative assessments of the efficacy of food sanitizing procedures and detailed correlations of microscopic changes in structural organization with desirable functional properties through interdisciplinary studies in engineering of agricultural products and materials. Through collaboration, systematic efforts are made to develop new and improved methods of microscopic imaging to help resolve important problems concerning the special aspects of agricultural commodities and food safety, raised through the objectives of CRIS projects and other ARS and extramural research programs.
This microscope is the fourth generation of transmission electron microscope employed at the Center since its founding in 1940. It continues a tradition of supporting a broad range of research projects requiring high spatial resolution (1-2 nanometers) in bright field images of agricultural biopolymers and ultra-thin sections of diverse agricultural materials and products of food safety procedures and treatments. The microscope features high vacuum and low, electron-dose operation for optimal performance at cryogenic temperatures (~-160 C). When used in conjunction with a Model 626 Cryo-transfer System supported by a Model 655 Dry Pumping Station, it can be used to visualize the micro- and nanostructure of thin, rapidly frozen samples under functional, hydrated conditions. An Ultracut S cryo-ultramicrotome is used for conventional thin sections or in conjunction with the cryostage for low temperature applications of frozen ultra-thin sections of bulk samples.
This revolutionary, new and versatile instrument, installed late in 2003, is the third generation of scanning electron microscope used at the Center. It incorporates a Schottky field emission gun which provides a small, bright probe size, high stability and low energy spread for extremely high resolution when operated in the conventional high vacuum mode. A unique system of pressure limiting apertures and patented gaseous secondary electron detector enables high resolution imaging of wet, fully-hydrated, cooled specimens and materials, and a high performance vacuum system allows imaging over a broad range of controlled pressures up to about 50 Torr in the specimen chamber. Sequential images of structural features during processes under wetting or drying conditions can be obtained through flexible and easy to use, mouse driven application software.
This compact and powerful, high resolution microscope brings a novel technology to ERRC. It has been operated for four years mainly as an Atomic Force Microscope in the patented TappingMode? on naturally hydrated agricultural and food safety samples or materials in a fluid cell, but accessories include multiple scanner heads and components that support a full range of scanning probes for study of surface characteristics of soft food materials, commodities and food safety systems such as topography, adhesion, elasticity, electrical and magnetic fields, etc. in contact and non-contact modes, scanning tunneling and many other operational modes that can provide unique information.
This modern optical microscope system represents another new technology at ERRC. It can be used as an imaging spectrophotometer utilizing three visible light lasers to excite fluorescence and reflection and four flexible channels of detection to gather convoluted sets of optical 'sections' into three-dimensional images. Extremely high quality lenses provide a range of magnifications and support high resolution imaging into the sub-micrometer range under native conditions for analysis of agricultural commodities, foods and food-safety treatments and processes.