Methods for identifying and measuring S-nitrosothiol bonds in heme-containing cells and molecules
The invention provides a method of detecting an S-nitrosothiol in a sample which includes treating the sample with a transition metal such as copper (I) and cysteine in the presence of a substance capable of blocking interactions between iron-containing compounds and NO and detecting the generated NO.
1. A method of measuring an S-nitrosothiol in an S-nitrosothiol-containing sample comprising the steps of:
obtaining a test sample;
reacting said test sample with cysteine and a non-iron transition metal under anaerobic conditions in a purge vessel;
providing at least one chemical species which prevents binding of NO to iron containing substances; and
analyzing said purge vessel output for NO generated from S-nitrosothiol, wherein the level of said NO is compared with the level of NO generated from an otherwise identical control sample or with the level of NO from a standard sample, thereby measuring S-nitrosothiol in a test sample.
2. The method of claim 1 , wherein said reaction occurs at a temperature of about 40° C. to about 80° C. and a pH above about 5.0.
3. The method of claim 2 , wherein said reaction occurs at a temperature of about 45° C. to about 60° C. and a pH of about 6.0 to about 7.0.
4. The method of claim 1 , wherein the concentration of said non-iron transition metal is from about 0.1 μM to about to 10.0 μM.
5. The method of claim 1 , wherein said transition metal is Cu(I).
6. The method of claim 5 , wherein said Cu(I) is selected from the group consisting of CuCl, CuI, or CuBr.
7. The method of claim 1 , wherein said cysteine concentration is from about 0.1 mM to about 10 mM.
8. The method of claim 1 , wherein said purge vessel is purged with at least one gas.
9. The method of claim 8 , wherein said at least one gas comprises an inert gas.
10. The method of claim 9 , wherein said inert gas is helium.
11. The method of claim 9 , further comprising a carbon monoxide gas free of metal carbonyls.
12. The method of claim 1 , wherein said analysis for NO is a chemiluminescence analysis.
13. The method claim 1 , wherein said sample is obtained from a subject selected from the group consisting of animals, mammals, humans, tissue culture, and cell culture.
14. The method of claim 13 , wherein said sample is selected from the group of consisting of blood, sweat, tears, urine, feces, plasma, amniotic fluid, airway lining fluid/bronchoalveolar lavages, cerebrospinal fluid, joint fluid, pleural fluid, peritoneal fluid, cervical fluid, semen, tissue, cells, and derivatives, fractions, extracts, and isolates thereof.
15. The method of claim 14 , wherein said sample, or derivative, fraction, extract or isolate thereof comprises proteins.
16. The method of claim 15 , wherein said protein is an S-nitrosothiol protein.
17. The method of claim 16 , wherein said S-nitrosothiol protein is a heme-containing protein.
18. The method of claim 17 , wherein said heme-containing protein is hemoglobin.
19. The method of claim 14 , wherein said sample is blood, further wherein an aliquot of said sample is also subjected to at least one additional assay which measures properties of blood relevant to hemoglobin allostery.
20. The method of claim 19 , wherein said at least one additional assay measures partial oxygen pressure or partial carbon dioxide pressure.
21. The method of claim 14 , wherein said cell is a red blood cell.
22. The method of claim 13 , wherein said subject is a human.