Jason Walther

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Contact Information

Jason Walther

Research Interests

The goal of metabolic flux analysis (MFA) is the quantitative determination of all intracellular fluxes in a system of interest. Results are obtained by introducing a labeled substrate (usually a labeled carbon source) into a cell culture, measuring relative labeling in metabolic byproducts, and computationally processing these measurements to arrive at fluxes.
Nonstationary metabolic flux analysis (NMFA) is similar to MFA with the provision that metabolite labeling is sampled and measured before the system reaches an isotopic steady state. NMFA, though computationally more complex, claims several advantages over its stationary analog. First, the amount of prohibitively expensive labeled substrate required for an experiment is greatly reduced. Second, the duration of such an experiment is considerably shortened, adding credibility to the metabolic steady-state assumption necessary for all flux analyses. Third, nonstationary flux analysis allows the pool sizes of metabolites, including intracellular intermediates, to be estimated in addition to the fluxes themselves.
I am working with the theoretical, computational, and experimental aspects of NMFA. In particular, I have developed computational tools for MFA tracer evaluation, I have created a rapid sampling apparatus for automated sampling and quenching, and I have used MFA to study metabolism in the oleaginous yeast Yarrowia lipolytica.


2010 Ph.D. Chemical Engineering, Massachusetts Institute of Technology
2004 M.Eng. Chemical Engineering, Stanford University
2004 B.S. Chemical Engineering, Stanford University


Metallo CM*, Walther JL*, and Stephanopoulos G. Evaluation of 13C isotopic tracers for metabolic flux analysis in mammalian cells. 2009. J Biotechnol 144(3):167-174.
Young JD*, Walther JL*, Antoniewicz MR, Yoo H, and Stephanopoulos G. An elementary metabolite unit (EMU) based method of nonstationary flux analysis. 2007. Biotechnol Bioeng 99(3):686-699.
Styczynski MP, Moxley JF, Tong LV, Walther JL, Jensen KL, and Stephanopoulos, G. Systematic identification of conserved metabolites in GC/MS data for metabolomics and biomarker discovery. 2007. Anal Chem 79(3):966-973.
Meyer TW, Peattie JW, Miller JD, Dinh DC, Recht NS, Walther JL, and Hostetter TH. Increasing the clearance of protein-bound solutes by addition of a sorbent to the dialysate. 2007. J Am Soc Nephrol 18(3):868-874.
Walther JL, Bartlett DW, Chew W, Robertson CR, Hostetter TH, and Meyer TW. 2006. Downloadable computer models for renal replacement therapy. Kidney Int 69(6):1056-1063.
Meyer TW, Walther JL, Pagtalunan ME, Martinez AW, Torkamani A, Fong PD, Recht NS, Robertson CR, and Hostetter TH. The clearance of protein-bound solutes by hemofiltration and hemodiafiltration. 2005. Kidney Int 68(2):867-877.
*These authors contributed equally to the work