Figure 4: Correlation in accuracy of SERS with ELISA sensor for the extracellular detection of stress-proteins, HSP70 (left) and RAD54 (right). Both techniques show good correlation (r2) in the levels of stress-proteins measured after exposing yeast to incremental doses of toxins, H2O2 and U.V. The inset shows the standard curves (amount in ng/ml vs. intensity) used to compare the sensitivity of the two techniques, measuring the pure proteins in solution. SERS intensity (×106) is measured at 1390 cm-1 and the ELISA intensity is measured at 450 nm. 1 ml culture=107 cells. The error-bars represent the S.D. of n=3×2 (three independent experiments done in duplicates).