Electrochemical Studies of Bismuth/L-Cysteine and Bismuth/L-Glutathione Interactions in Aqueous Buffers
Bibliographic record
Abstract
Introduction Previous studies (1-3) in this laboratory have involved electrochemical studies of the interaction of Zn(II) ions with L-cysteine in an attempt to more fully characterize the formation of “zinc finger” proteins (4). This interaction can be investigated both by the effect of Zn(II) addition upon the oxidation of the thiol group of L-cysteine, and by the effect of L-cysteine addition upon the reduction potential of Zn(II). In particular, the addition of L-cysteine to ZnSO 4 dissolved in pH 7.4 MOPS buffer results in a large negative shift in the reduction potential for Zn(II) ions (2). This behavior is clear evidence for the formation of a Zn 2+ : Cysteine complex. In the present study, we have extended this work to the interaction of bismuth(III) with L-cysteine and with glutathione, prompted by the significance of such interactions in human biochemistry (5-7). Experimental L-Cysteine, L-glutathione, and MOPS (3-(N-morpholino)propanesulfonic acid) were obtained from Sigma-Aldrich Corporation, and bismuth(III) nitrate was obtained from Baker. Electrochemical experiments were carried out under nitrogen using a Gamry Instruments Interface 1000 potentiostat and Gamry Framework software. Working electrodes were obtained from BASi (Glassy carbon, 3.0 mm diameter; platinum 1.6 mm) and eDAQ (gold, 1.0 mm diameter). Potentials were measured with respect to a silver/silver chloride saturated KCl reference electrode (BASi). Results and Discussion It has been found that Bi(NO 3 ) 3 is only slightly soluble in pH 7.4 MOPS buffer due to probable formation of hydroxyl complexes (8). It is, however, possible to observe small currents for deposition and subsequent stripping of bismuth at gold and glassy carbon in this solution. Upon addition of 1:1 bismuth(III):L-cysteine, the solution appearance changed from cloudy to clear, and voltammetric currents increased substantially, indicating a strong interaction between bismuth(III) and L-cysteine. In addition, a negative voltammetric shift for the bismuth reduction potential was observed, as was the case for the zinc(II):L-cysteine interaction (2). Further additions of L-cysteine were found to produce additional negative shifts for bismuth(III) reduction. Similar behavior for L-glutathione was observed. MALDI-TOF spectra for the 1:2 Bi(III):L-glutathione and similar complexes in aqueous solutions have been reported (9) and provide supporting evidence for the electrochemical results in the present study. A similar spectrum for the 1:2 Bi(III):L-glutathione complex in pH 7.4 MOPS buffer has been obtained in the present work. References G. T. Cheek and M. A. Worosz, ECS Transactions , 2016 , 72(27) , 1-8. M. Y. Doan, M. A. Worosz, and G.T. Cheek, ECS Transactions , 2017 , 77(11) , 1537-1544. G. T. Cheek, M. A. Worosz, M. Y. Doan, and D. C. Clark , ECS Transactions 2017 , 80 ( 10 ), 1159-1166. C.K. Mathews, K.E. Van Holde, D.R. Appling, and S. J. Anthony-Cahill, Biochemistry , 4 th Edition , Pearson Canada, Toronto, 2013 . G. G. Briand and N. Burford, Chem. Rev., 1999, 99, 2601-2657. R. Ge and H. Sun, Acc. Chem. Res., 2007, 40 , 267-274. Y. Hong, Y.-T Lai, G. C-F Chan, and H. Sun , PNAS, 2015, 112(11) , 3211–3216 . J. Kragten, L. G. Decnop-Weever, and P. Gründler, Talanta , 1993 , 40(4) , 485-490. N. Burford, M. D. Eelman, D. E. Mahony, and M. Morash , Chem. Commun. , 2003 , 146–147.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".