A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding
Analytical Biochemistry, 1976 · paper · Biomedicine
Describes a protein assay based on Coomassie Brilliant Blue G-250 binding to protein, which shifts the dye's absorption peak from 465 to 595 nm. It is rapid and reproducible, with little interference from most common reagents except large amounts of detergents.
1 finding
Wording The text cites Table 1 for 'The small effects due to Tris, acetic acid, 2-mercaptoethanol, sucrose, glycerol, EDTA', but Table 1 has no acetic acid row. The table's Acetone (0.069) and 5% Phenol (0.046) rows are not mentioned in the text.
- p. 5 Results, Interference by nonprotein components
The small effects due to Tris, acetic acid, 2-mercaptoethanol, sucrose, glycerol, EDTA
- p. 6 Table 1, Substance column
Acetone
- p. 6 Table 1
2 M Tris
- p. 5 Interference by nonprotein components
Tris, acetic acid, 2-mercaptoethanol
Only the authors can say what is right here.
Judge's note: Page 5 and page 6 images checked. Table 1 lists KCl, NaCl, MgCl2, Tris, EDTA, (NH4)2SO4, glycerol, 2-mercaptoethanol, sucrose, ethanol, acetone, phenol, Triton X-100, SDS and Hemosol. There is no acetic acid. 'Acetic acid' may be a slip for 'acetone', or a row may be missing. Only the author can say which.
Second check: another model agreed
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6 minor (typos and the like; most checked by the judge only)
Reference or label The ethanol concentration in the final reagent is labelled "4.7% (w/v) ethanol", but the recipe (50 ml of 95% ethanol diluted to 1 liter) gives about 4.75% on a volume/volume basis.
- p. 2 Methods, Preparation of protein reagent
4.7% (w/v) ethanol
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: the density of ethanol (about 0.79 g/ml) and the reading of '95% ethanol' as v/v. Page 2 crop confirms the recipe and the '(w/v)' label. 50*0.95/1000 = 4.75% v/v, which matches the printed 4.7%. On a w/v basis it would be about 3.75%. The (w/v) label looks like it was carried over from the dye and phosphoric acid entries. The number is fine; the unit label is likely wrong.
Second check: another model agreed
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Wording Cuvette binding is said to cause 'less than 1% error, as indicated by the standard deviation of triplicate assays in the reproducibility section', but that section reports 'a standard deviation of 1.2% of mean value'.
- p. 6 Paragraph after Table 1
i.e., less than 1% error, as indicated by the stand- ard deviation of triplicate assays in the reproducibility section
- p. 3 Results, Reproducibility, sensitivity, and linearity
gives a standard devia- tion of 1.2% of mean value for the assay
- p. 6 Paragraph after Table 1 (cuvette binding)
less than 1% error, as indicated by the stand- ard deviation of triplicate assays in the reproducibility section
- p. 3 Results, Reproducibility, sensitivity, and linearity
Statistical analysis gives a standard devia- tion of 1.2% of mean value for the assay.
Only the authors can say what is right here.
Judge's note: Page 3 and page 6 images checked. The cited evidence (SD 1.2%) is above the 1% claimed. The binding error could be a smaller part of the total SD, but no analysis separating it out is given. The authors should clarify what the <1% figure rests on.
Second check: another model agreed
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Typo Singular subject takes a plural verb: "Even the modified procedure for eliminating problems with the Lowry and biuret assays (10,11) present problems".
- p. 1 Introduction
Even the modified procedure for eliminating problems with the Lowry and biuret assays (10,11) present problems
Judge's note: Page 1 image shows exactly this wording. Two methods are cited and the sentence ends with "the modified procedures", so the subject should be "procedures" (or the verb "presents"). This is a grammar slip.
Second check: none (judge only)
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Typo Typo: 'either mathematically of spectrophotometrically' should read 'either mathematically or spectrophotometrically'.
- p. 5 Results, Interference by nonprotein components
either mathematically of spectrophotometrically
Judge's note: Page 5 image shows 'of'; this is not an extraction artefact.
Second check: none (judge only)
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Typo The chemical formula is printed as 'Soak cuvettes in 0.1 M HCL.' instead of HCl.
- p. 6 Cuvette cleaning, Method 2
0.1 M HCL
- p. 6 Cuvette cleaning, Method 2
Soak cuvettes in 0.1 M HCL.
Judge's note: Page 6 image shows a capital L. Table 1 on the same page uses the correct case for KCl, NaCl and MgCl2.
Second check: none (judge only)
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Typo Subject–verb disagreement: 'the following directions for cleaning the blue complex from cuvettes is included' (should be 'are included').
- p. 6 Paragraph before cleaning methods
directions for cleaning the blue complex from cuvettes is included
Judge's note: Page 6 image confirms the wording.
Second check: none (judge only)