Figure 1.
Total RSH and GSH content in E. coli overexpressing GSH biosynthesis genes.
Cellular RSH (after 4 h IPTG induction, A) and GSH levels (B) after 4 h (white) or 16 h (striped) IPTG induction were determined in E. coli AG1 (wt), AG1/pCA24NgshA (gshA) and AG1/pCA24NgshB (gshB) cells (n = 3). *p<0.05; **p<0.005.
Figure 2.
Fluorescence assessment in E. coli overexpressing gshA or gshB genes.
UV light-exposed cell pellets of E. coli AG1/pCA24NgshA (A) or AG1/pCA24NgshB (B) that were untreated (1) or exposed to CdCl2 (2), K2TeO3 (3) or CdCl2/K2TeO3 (4).
Table 1.
Cd and Te content of E. coli expressing gshA or gshB genes.
Figure 3.
Fluorescence microscopy of E. coli exposed to Cd and Te salts.
E. coli AG1/pCA24NgshA treated with CdCl2 and K2TeO3 was analyzed by epifluorescence microscopy. Circles indicate structures where fluorescence is accumulated. A, left image: phase contrast (PC); central image: monochromatic fluorescence (F) after excitation using UV-DAPI/FITC filter; right image: merge. B, left image: magnification phase contrast (PC); left image: merge. C, fluorescence microscopy under UV light exposure.
Figure 4.
Particle purification and size determination.
A, UV-exposed cell suspensions of E. coli AG1/pCA24NgshA, untreated or exposed to CdCl2 or CdCl2/K2TeO3 (from left to right). B, purified fractions exposed to UV light. C and D, DLS particle size determination of fluorescent samples from cells exposed to CdCl2 or CdCl2/K2TeO3, respectively.
Table 2.
Elemental analysis of purified nano-sized structures.
Figure 5.
Absorbance and fluorescence spectra of purified NPs.
A, absorption spectra of NPs from unexposed (solid black line), exposed to CdCl2 (dashed grey line) or CdCl2/K2TeO3 (dashed black line) cells. B and C, emission spectra of NPs from cells exposed to CdCl2 or CdCl2/K2TeO3, respectively.
Figure 6.
XRD pattern of biosynthesized CdTe QDs.
CdTe NPs were purified from E. coli gshA cells as described in Methods and the presence of crystalline structures analyzed by XRD.
Figure 7.
FTIR spectroscopy of GSH (A), chemically synthesized (B) and biosynthesized (C) CdTe-GSH QDs.
Biological CdTe NPs where purified as described in Methods and chemical, biocompatible CdTe QDs where synthesized as described [19]. FTIR spectroscopy spectra were recorded and compared with a GSH standard.
Figure 8.
Effect of temperature, microaerophilic conditions and citrate on E. coli fluorescence.
UV-exposed E. coli AG1/pCA24NgshA cells previously incubated under NP biosynthesis conditions with some modifications: 1, control (37°C); 2, increased incubation temperature (42°C); 3, reducing agent (citrate buffer pH 7.0); 4, microaerophilic conditions.