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Why do protein solutions have to be alkalised in biuret test?
Rosetta ab initio prediction and protein-protein interaction fitness helpNaCl role in CTAB - DNA complex in DNA extractionAre There Rules for How Proteins Are Formed?How do I identify the protein with the highest Disulfide bond density? i.e protein with highest ratio of Disulphide bonds per Peptide bond?Amino acid compatibilityMultiple transcripts encoding for one proteinHow much nucleoside triphosphate is required to form one peptide bond during protein synthesis?How would one identify cellular transcription factors associated with a viral protein in a treated cell line?Is the signal peptide always cleaved during protein synthesis in the ER?How to calculate the amount of protein synthesized knowing the amount of essential amino acids ingested?
$begingroup$
I’ve read that CuSO4 solution reacts with peptide bonds that connect amino acids to create a violet colour, but the instructions always tell me to add NaOH solution to the protein solution before I add CuSO4. How is alkalising the protein solution before adding CuSO4 solution an aid to this process?
proteins lab-techniques food-chemistry
edited 38 mins ago
WYSIWYG
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
$endgroup$
add a comment |
$begingroup$
I’ve read that CuSO4 solution reacts with peptide bonds that connect amino acids to create a violet colour, but the instructions always tell me to add NaOH solution to the protein solution before I add CuSO4. How is alkalising the protein solution before adding CuSO4 solution an aid to this process?
proteins lab-techniques food-chemistry
edited 38 mins ago
WYSIWYG
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
$endgroup$
$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago
add a comment |
$begingroup$
I’ve read that CuSO4 solution reacts with peptide bonds that connect amino acids to create a violet colour, but the instructions always tell me to add NaOH solution to the protein solution before I add CuSO4. How is alkalising the protein solution before adding CuSO4 solution an aid to this process?
proteins lab-techniques food-chemistry
edited 38 mins ago
WYSIWYG
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
$endgroup$
I’ve read that CuSO4 solution reacts with peptide bonds that connect amino acids to create a violet colour, but the instructions always tell me to add NaOH solution to the protein solution before I add CuSO4. How is alkalising the protein solution before adding CuSO4 solution an aid to this process?
proteins lab-techniques food-chemistry
proteins lab-techniques food-chemistry
edited 38 mins ago
WYSIWYG
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
edited 38 mins ago
WYSIWYG
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
edited 38 mins ago
WYSIWYG
31.6k750133
edited 38 mins ago
WYSIWYG
31.6k750133
edited 38 mins ago
WYSIWYG
31.6k750133
31.6k750133
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
asked 7 hours ago
Ubaid HassanUbaid Hassan
1313
1313
$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago
add a comment |
$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago
$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago
$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
This is probably to prevent precipitation of copper hydroxide (see Itzhaki & Gill, 1964 - they suggest adding dilute copper sulfate slowly to the NaOH solution to avoid this). If you have the protein already alkalized and ready to react you'll get the color reaction before precipitate forms.
Commercial premixed solutions, like @canadianer mentioned in a comment, have tartrate present to prevent this (Geiger & Bessman, 1972 mention this).
It doesn't seem like it's strictly necessary to add NaOH first, but that's probably the most reliable way to do the assay without using an additional stabilizing agent.
Itzhaki, R. F., & Gill, D. M. (1964). A micro-biuret method for estimating proteins. Analytical biochemistry, 9(4), 401-410.
Geiger, P. J., & Bessman, S. P. (1972). Protein determination by Lowry's method in the presence of sulfhydryl reagents. Analytical biochemistry, 49(2), 467-473.
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
$endgroup$
add a comment |
$begingroup$
You mix those two chemicals to get a Cu(OH) 2 colloid, if you mixed them earlier it would settle down and not form a colorful complex (as efficiently). Base is added first because (i presume) it denaturates the protein which partly unfolds it, allowing copper ions to form complexes along a greater surface, giving clearer results.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
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2 Answers
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2 Answers
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active
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$begingroup$
This is probably to prevent precipitation of copper hydroxide (see Itzhaki & Gill, 1964 - they suggest adding dilute copper sulfate slowly to the NaOH solution to avoid this). If you have the protein already alkalized and ready to react you'll get the color reaction before precipitate forms.
Commercial premixed solutions, like @canadianer mentioned in a comment, have tartrate present to prevent this (Geiger & Bessman, 1972 mention this).
It doesn't seem like it's strictly necessary to add NaOH first, but that's probably the most reliable way to do the assay without using an additional stabilizing agent.
Itzhaki, R. F., & Gill, D. M. (1964). A micro-biuret method for estimating proteins. Analytical biochemistry, 9(4), 401-410.
Geiger, P. J., & Bessman, S. P. (1972). Protein determination by Lowry's method in the presence of sulfhydryl reagents. Analytical biochemistry, 49(2), 467-473.
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
$endgroup$
add a comment |
$begingroup$
This is probably to prevent precipitation of copper hydroxide (see Itzhaki & Gill, 1964 - they suggest adding dilute copper sulfate slowly to the NaOH solution to avoid this). If you have the protein already alkalized and ready to react you'll get the color reaction before precipitate forms.
Commercial premixed solutions, like @canadianer mentioned in a comment, have tartrate present to prevent this (Geiger & Bessman, 1972 mention this).
It doesn't seem like it's strictly necessary to add NaOH first, but that's probably the most reliable way to do the assay without using an additional stabilizing agent.
Itzhaki, R. F., & Gill, D. M. (1964). A micro-biuret method for estimating proteins. Analytical biochemistry, 9(4), 401-410.
Geiger, P. J., & Bessman, S. P. (1972). Protein determination by Lowry's method in the presence of sulfhydryl reagents. Analytical biochemistry, 49(2), 467-473.
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
$endgroup$
add a comment |
$begingroup$
This is probably to prevent precipitation of copper hydroxide (see Itzhaki & Gill, 1964 - they suggest adding dilute copper sulfate slowly to the NaOH solution to avoid this). If you have the protein already alkalized and ready to react you'll get the color reaction before precipitate forms.
Commercial premixed solutions, like @canadianer mentioned in a comment, have tartrate present to prevent this (Geiger & Bessman, 1972 mention this).
It doesn't seem like it's strictly necessary to add NaOH first, but that's probably the most reliable way to do the assay without using an additional stabilizing agent.
Itzhaki, R. F., & Gill, D. M. (1964). A micro-biuret method for estimating proteins. Analytical biochemistry, 9(4), 401-410.
Geiger, P. J., & Bessman, S. P. (1972). Protein determination by Lowry's method in the presence of sulfhydryl reagents. Analytical biochemistry, 49(2), 467-473.
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
$endgroup$
This is probably to prevent precipitation of copper hydroxide (see Itzhaki & Gill, 1964 - they suggest adding dilute copper sulfate slowly to the NaOH solution to avoid this). If you have the protein already alkalized and ready to react you'll get the color reaction before precipitate forms.
Commercial premixed solutions, like @canadianer mentioned in a comment, have tartrate present to prevent this (Geiger & Bessman, 1972 mention this).
It doesn't seem like it's strictly necessary to add NaOH first, but that's probably the most reliable way to do the assay without using an additional stabilizing agent.
Itzhaki, R. F., & Gill, D. M. (1964). A micro-biuret method for estimating proteins. Analytical biochemistry, 9(4), 401-410.
Geiger, P. J., & Bessman, S. P. (1972). Protein determination by Lowry's method in the presence of sulfhydryl reagents. Analytical biochemistry, 49(2), 467-473.
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
answered 7 hours ago
Bryan Krause♦Bryan Krause
20.3k33358
20.3k33358
add a comment |
add a comment |
$begingroup$
You mix those two chemicals to get a Cu(OH) 2 colloid, if you mixed them earlier it would settle down and not form a colorful complex (as efficiently). Base is added first because (i presume) it denaturates the protein which partly unfolds it, allowing copper ions to form complexes along a greater surface, giving clearer results.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
You mix those two chemicals to get a Cu(OH) 2 colloid, if you mixed them earlier it would settle down and not form a colorful complex (as efficiently). Base is added first because (i presume) it denaturates the protein which partly unfolds it, allowing copper ions to form complexes along a greater surface, giving clearer results.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
You mix those two chemicals to get a Cu(OH) 2 colloid, if you mixed them earlier it would settle down and not form a colorful complex (as efficiently). Base is added first because (i presume) it denaturates the protein which partly unfolds it, allowing copper ions to form complexes along a greater surface, giving clearer results.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
You mix those two chemicals to get a Cu(OH) 2 colloid, if you mixed them earlier it would settle down and not form a colorful complex (as efficiently). Base is added first because (i presume) it denaturates the protein which partly unfolds it, allowing copper ions to form complexes along a greater surface, giving clearer results.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 6 hours ago
Francis L.Francis L.
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered 6 hours ago
Francis L.Francis L.
1012
answered 6 hours ago
Francis L.Francis L.
1012
1012
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Francis L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
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$begingroup$
The directions explicitly state to add the sodium hydroxide before the copper sulfate? I've never done the biuret test myself, but I can't imagine it would make a difference. Commercially available biuret reagents are sold as premixed solutions.
$endgroup$
– canadianer
7 hours ago