Each frame on this page can be independently resized. This page uses JavaScript to simulate the radiolabeling kinetics of intermediates of the pathway of 3-dimethylsulfoniopropionate (DMSP) in Enteromorpha intestinalis. The assumptions of the simulation are summarized in the metabolic shown above (top left frame). The pathway receives radioisotope label from the precursor, [35S]-methionine (Met), supplied at a high specific activity (10,000 nCi.nmol-1; P1) at zero time to Enteromorpha fronds. Of the 5.0 nmol.gfw-1 of [35S]-methionine supplied, 8.6% (0.43 nmol.gfw-1; P3) was assumed to be as methionine sulfoxide and not absorbed. The image shown above illustrates the Visual Basic version of this same model, and its graphical ouput, using the same default values of pool sizes, fluxes, specific activity and times as specified in the lower right frame. Definitions of the variables are given in the upper right frame.
The JavaScript language is supported by both Netscape Navigator and Microsoft Internet Explorer 3.0 or above. If you are using a JavaScript-compatible browser, try varying the pool sizes and fluxes (lower right frame) to determine how this influences the labeling patterns. Note than when the rate of synthesis exceeds the rate of utilization, the pool will expand with time. When the rate of utilization exceeds the rate of synthesis, the pool will deplete with time. If a pool becomes zero during the time-course, the simulation will terminate before completion! A key variable for adjustment is the value of k, which determines the rate of uptake of the exogenously supplied precursor. As k is increased, so is the rate of uptake of methionine.
Starting values should be in numerical format, and should not exceed 6 characters in length. Errors resulting in script termination will occur when values are entered as text rather than in numerical format. Upon encountering such errors it may be necessary to "Refresh" the page.
After entering starting values (inputs), click the Calculate button. Simulated values will then be displayed in the text boxes below the "Calculate" button. The Calculate button can be reused repetitively after modifying input values.
With certain browsers (e.g. Internet Explorer 3.0), the computed values of radioactivity in each pool and pool sizes displayed in the text boxes (lower right frame) are double-precision floating-point (e.g. 0.019995 may be displayed as 1.9995E-02). Thus, it may be necessary to use your mouse to highlight certain text boxes to view the full double-precision floating-point notations for values suspected to be less than 0.1.