2005 Annual Report
1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter?
The essential nature of genetically coded amino acids containing sulfur (methionine and cysteine) and selenium (selenocysteine) is well established. However, the health promoting effects of non-genetically coded sulfur and selenium amino acids (i.e., amino acid secondary metabolites) is unproven. The lack of conclusive proof is largely due to a lack of data on the levels of these compounds in commonly consumed plant materials. A method, or series of methods, is needed to determine all S and Se amino acids and amino acid secondary metabolites in plant materials. More complete data is needed for methionine and cysteine in the National Nutrient Database for Standard Reference (NNDSR) and a provisional database is needed for selenocysteine, selenomethionine, and selected non-protein, amino acid secondary metabolites.
The research to be undertaken falls under National Program 107 - Human Nutrition and addresses performance goal 3.1.2.B as described in the National Program Action Plan. Goal 3.1.2 is "Food Composition and Consumption: Develop techniques for determining food composition, maintain national food composition databases, monitor the food and nutrient consumption of the U.S. population, and develop and transfer effective nutrition intervention strategies." This project directly addresses Priority Objective B. Develop Analytical Methodology for Nutrients.
The field of nutrition and public health will benefit from a better understanding of the distribution of S and Se in proteins, free amino acids, and amino acid secondary metabolites in foods. New data in the National Nutrient Database will provide the public with accessible information on the S and Se content of foods. There will be improved knowledge of the exchange of S and Se in biological systems. The field of analytical chemistry will have more accurate and comprehensive methods for the determination of S and Se compounds in foods.
2.List the milestones (indicators of progress) from your Project Plan.
Year 1 (FY 2004)
*Initiate development of in-house standards.
*Initiate development of a total sulfur method.
*Initiate development of methods for free amino acids.
*Initiate evaluation of the Cyanogen Bromide (CNBr) method.
Year 2 (FY 2005)
*Continue development of in-house standards.
*Continue development of a total sulfur method.
*Continue development of methods for free amino acids.
*Continue evaluation of the CNBr method.
Year 3 (FY 2006)
*Complete development of in-house standards.
*Complete development of methods for free amino acids.
*Complete evaluation of the CNBr method.
*Initiate development of method for determination of S and Se in proteins.
*Initiate determination of S and Se in foods for database.
Year 4 (FY 2007)
*Complete development of method for determination of S and Se in proteins.
*Continue determination of S and Se in foods for database.
Year 5 (FY 2008)
*Continue analyzing S and Se in foods for database.
4a.What was the single most significant accomplishment this past year?
Data to assign values for the selenomethionine (Semet) content in a new Certified Reference Material- Selenized Yeast(being made available in December 2005 by the National Research Council of Canada)were collaboratively generated by Food Composition Laboratory (FCL). Biological availability, metabolism and potential health benefits of the essential element Se is highly dependent upon its chemical forms in the diet. This element is of critical interest diets augmented with Se have been shown to reduce the risk of prostate cancer. Appropriate standards to assure accuracy of determination of these forms have not previously been available. The candidate Certified Reference Material (CRM) was analyzed using unique FCL methodology to determine Semet in foods by reaction with CNBr, incorporating isotope dilution mass spectrometry with a 74Se labeled Semet. Availability of this CRM with Se species information will greatly assist the general food analysis community to assure accuracy of their results.
4b.List other significant accomplishments, if any.
Developed a routine method for the determination of free sulfur and selenium containing primary and secondary amino acids in foods. Secondary metabolite amino acids are not incorporated into proteins, are precursors for a wide variety of bioactive compounds that have a significant impact on human health, and are not quantified in commonly consumed foods. A method was developed based on a commercial kit (using ethylchloroformate derivatization and gas chromatography) that can determine methionine, cysteine, selenomethionine, selenocysteine, methyl selenocysteine, and alliin (the active sulfur component in garlic). This method will allow us to rapidly survey foods for the free amino acids and establish a database and will allow others to evaluate the efficacy of these compounds in enhancing human health.
4c.List any significant activities that support special target populations.
Initiating development of method for analysis of protein amino acids, using the method above following acid hydrolysis of the protein.
Evaluating pulsed flame photometric detector as a S and Se specific detector for gas chromatography.
5.Describe the major accomplishments over the life of the project, including their predicted or actual impact.
This is the second year of a new project.
The CNBr method was applied to the determination of selenomethionine (Semet) in a variety of wheat flour reference materials from National Institute of Standards and Technology (NIST) (wheat gluten, Durum wheat, hard red spring wheat, and soft winter wheat). Despite total Se concentrations differing by as much as a factor of 45, the Semet content was consistently about 46% of total Se. If this consistency can be confirmed in a variety of wheat cultivars commonly on the market, it will be significantly easier to evaluate total Semet dietary intake by simply measuring total Se content of wheat.
6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
Data from the unique FCL method was used to certify the selenomethionine content in a new Certified Reference Material - Selenized Yeast (Available from the National Research Council of Canada). This CRM is a technology transfer artifact that transfers measurement traceability from highest level metrology practice to routine use by public and private sector laboratories measuring selenomethionine content in foods.
7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Wolf, W.R., Goldschmidt, R.J. 2005. Measurement of selenomethionine by reaction with cyanogen bromide and gas-chromatography-isotope dilution mass spectrometry: comparison of two sample treatments. In: Pittcon, March 2005, Orlando, Florida.
Yang, L., Sturgeon, R.E., Mester, Z., Wolf, W.R., Goldschmidt, R.J. 2004. Determination of selenomethionine in yeast using CNBR derivatization and species specific isotope dilution GC ICP-MS and GC-MS. Journal of Analytical Atomic Spectrometry. 19:1448-1453.