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In our publication [Opt. Express, 20(19), 22285-22313 (2013)] a coding error caused an incorrect value of absorptivity to be used for tyrosine. Tables showing the corrected results are shown.
© 2014 Optical Society of America
There was a typographical error in the middle expression of Eq. (2) in [1] which should have been
The expression on the right was correct, as were the other equations in the text. This typographical error did not affect the computer code or calculated results.A coding error caused the absorptivity of tryptophan to be used for both tryptophan and tyrosine in the calculated results in [1]. The effects of this error were largest in the proteins, especially in bovine serum albumin, where the corrected fluorescence cross section is 57% smaller than the value given in [1]. Another coding error caused the contribution of phenylalanine to the imaginary component of the refractive index of the two albumins to be approximately three-fold too high. This second error caused relatively minor changes because, even in ovalbumin where the effect of the error was largest, the contribution of phenylalanine to the absorption is only 2.7% at 266-nm, and is negligible at 280 nm and 355 nm. These coding errors were corrected. The corrected results are shown in four tables. Tables 1 and 2 , for 266-nm and 280-nm excitation, respectively, show calculated contributions of the various substances to the imaginary part of the refractive index for E. coli, Bacillus vegetative cells and Bacillus spores. Tables 1 and 2 each combine values that were changed from the values in Tables 2, 3 and 4 of [1]. Molecules with contributions to mi that are smaller than 10−6 at both excitation wavelengths (266 nm and 280 nm) were omitted. Table 3 shows the contributions to mi for ovalbumin and bovine serum albumin. This table combines values that changed from those in Tables 5 and 6 in [1]. Table 4 shows the modeled results which replace those shown in Table 7 of [1]. There were no changes in Tables 1 or 8 in [1], or in the 355-nm-excited fluorescence.
Table 1. A combination of the corrected values for 266-nm excitation in Tables 2, 3 and 4 of Ref [1]. Each column provides the contributions to the imaginary component of the refractive index (mi) and the percent contribution in parentheses. Molecules with contributions to mi less than 10−6 at 266-nm were omitted because those magnitudes are negligible.
Table 2. As in Table 1 above except that the excitation wavelength is 280-nm.
Table 3. Corrected modeled mi values for Tables 5 and 6 from [1].
Table 4. Corrected modeled mi values for Table 7 in [1].
For the spores, the ratios of the modeled to measured fluorescence cross sections, using modeled values from Table 4 here and measured values in Table 7 from [1], are: 16 for the 266-nm excited, dry, modeled Bacillus and measured B. subtilis; 27 for the modeled Bacillus (266-nm-excited, dry) to measured B. globigii (266-nm excited, aqueous suspension); 70 for the modeled Bacillus (266-nm excited, dry) to the measured B. subtilis (270-nm-excited, dry); and 15 for the modeled Bacillus (266-nm excited, dry) to the measured B. subtilis (270-nm excited, wet). The ratio of the modeled Bacillus (280-nm excited, dry) to measured Bacillus was 29 for B. subtilis, 51 for B. thuringiensis (both excited at 280 nm) and 61 for B. globigii excited by a broadband source from 270 to 290 nm.
For the vegetative cells, the ratios of the modeled to measured fluorescence cross sections, using modeled values from Table 4 and measured values from Table 7 of [1], are: 1.3 for the 266-nm-excited vegetative Bacillus (model) to B. subtilis (measured); 2.0 for the 280-nm-excited vegetative Bacillus (model) to M. luteus (measured); and 0.56 for the 266-nm excited E. coli (model) to P. agglomerans (measured).
For the proteins, the ratios of the modeled to measured fluorescence cross sections, using modeled values from Table 4 and measured values from Table 7 in [1] are 0.3 for ovalbumin and 0.35 for bovine serum albumin.
Changes in subsection 5.1: The ratios of modeled to measured fluorescence cross sections range from 0.56 to 2.0 for vegetative cells, including ratios for both 266 and 280 nm, and from 0.3 to 0.35 for the two albumins. Changes in subsection 5.2: The modeled fluorescence cross sections of spores excited at 266- or 280-nm are 15 to 70 times larger than the measured cross sections in Table 7 of [1]. Changes in section 7: Fluorescence cross sections modeled using these concentrations and optical properties were within a factor of 2 when compared with measured cross sections for vegetative cells excited by light in the 266- to 280-nm range, and were approximately one third of the measured values for the proteins. Even though the 266- to 280-nm region is the wavelength band in which the most reliable information is available for the main fluorophores and their concentrations in these biological particles, in the case of spores excited at 266 to 280 nm the model values were 15 to 70 times larger than the measured values.