TY - JOUR
T1 - Estimation of reactive thiol concentrations in dissolved organic matter and bacterial cell membranes in aquatic systems
AU - Joe-Wong, Claresta
AU - Shoenfelt, Elizabeth
AU - Hauser, Emily J.
AU - Crompton, Nyssa
AU - Myneni, Satish Chandra Babu
PY - 2012/9/18
Y1 - 2012/9/18
N2 - Organic thiols are highly reactive ligands and play an important role in the speciation of several metals and organic pollutants in the environment. Although small thiols can be isolated and their concentrations can be estimated using chromatographic and derivatization techniques, estimating concentrations of thiols associated with biomacromolecules and humic substances has been difficult. Here we present a fluorescence-spectroscopy-based method for estimating thiol concentrations in biomacromolecules and cell membranes using one of the soluble bromobimanes, monobromo(trimethylammonio)bimane (qBBr). The fluorescence of this molecule increases significantly when it binds to a thiol. The change in the sample fluorescence due to thiols reacting with qBBr is used to determine thiol concentration in a sample. Using this method, small thiols such as cysteine and glutathione can be detected in clean solutions down to ∼50 nM without their separation and prior concentration. Thiols associated with dissolved organic matter (DOM) can be detected down to low micromolar concentration, depending on the DOM background fluorescence. The charge on qBBr prevents its rapid diffusion across cell membranes, so qBBr is ideal for estimating thiol concentration at the cell membrane-water interface. This method was successfully used to determine the thiol concentration on the cell envelope of intact Bacillus subtilis to nanomolar concentration without any special sample preparation. Among the chemical species tested for potential interferences (other reduced sulfides methionine and cystine, carboxylate, salt (MgCl2)), carboxylates significantly influenced the absolute fluorescence signal of the thiol-qBBr complex. However, this does not affect the detection of thiols in heterogeneous mixtures using the presented method.
AB - Organic thiols are highly reactive ligands and play an important role in the speciation of several metals and organic pollutants in the environment. Although small thiols can be isolated and their concentrations can be estimated using chromatographic and derivatization techniques, estimating concentrations of thiols associated with biomacromolecules and humic substances has been difficult. Here we present a fluorescence-spectroscopy-based method for estimating thiol concentrations in biomacromolecules and cell membranes using one of the soluble bromobimanes, monobromo(trimethylammonio)bimane (qBBr). The fluorescence of this molecule increases significantly when it binds to a thiol. The change in the sample fluorescence due to thiols reacting with qBBr is used to determine thiol concentration in a sample. Using this method, small thiols such as cysteine and glutathione can be detected in clean solutions down to ∼50 nM without their separation and prior concentration. Thiols associated with dissolved organic matter (DOM) can be detected down to low micromolar concentration, depending on the DOM background fluorescence. The charge on qBBr prevents its rapid diffusion across cell membranes, so qBBr is ideal for estimating thiol concentration at the cell membrane-water interface. This method was successfully used to determine the thiol concentration on the cell envelope of intact Bacillus subtilis to nanomolar concentration without any special sample preparation. Among the chemical species tested for potential interferences (other reduced sulfides methionine and cystine, carboxylate, salt (MgCl2)), carboxylates significantly influenced the absolute fluorescence signal of the thiol-qBBr complex. However, this does not affect the detection of thiols in heterogeneous mixtures using the presented method.
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U2 - 10.1021/es301381n
DO - 10.1021/es301381n
M3 - Article
C2 - 22916681
AN - SCOPUS:84866386276
SN - 0013-936X
VL - 46
SP - 9854
EP - 9861
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 18
ER -