Note that some assignments may refer to the Experimental section by the synonym Methods and Materials.

Content of an Experimental section

Succinctly provide the minimum practical detail that the reader can reproduce your work. Do not rewrite the detailed procedures from the lab manual. See Captions-Methods (Appendix B) for lists of minimum required details for common methods.

Always provide the composition of buffers and other solutions. If a solution is a commercial product with unknown composition, provide identifying product information (see next point).

Names of commercial products and manufacturers should be included only if alternate sources are deemed unsatisfactory for reproducability. By convention, always identify:

• the model and manufacturer for major analytical equipment,
• the name, manufacturer, and version number of major software used to process data.
• the commerical name and manufacturer of proprietary solutions, kits, and other products that cannot be replicated exactly.

UniProt Accession IDs and/or protein IDs (http://www.uniprot.org/) should be provided for all proteins that are purified and/or characterized.

State precautions whenever hazardous materials or dangerous procedures are utilized .

Explain the procedures for data analysis. You must define any non-standard units (e.g. enzyme units), state major equations required for data analysis, and provide the statistical basis of measurements (e.g. "values are the mean of three replicate measurements," "uncertainty is the standard deviation of values").

Do not include background theory.

Do not include experimental results.

• One exception is that synthesis methods conclude with reaction yeilds and characterization data. Use the following typical example as a model.

  The residue was purified by flash chromatography on silica gel (0 → 4% MeOH in DCM) to provide the title compound as a light-yellow oil (288 mg, 1.21 mmol, 69%). ¹H NMR (300 MHz, CDCl₃): δ 7.33–7.26 (m, 6H), 7.25–7.14 (m, 3H), 3.70 (s, 2H), 2.37 (s, 3H), 1.93 (br s, ¹H), 1.02 (d, 2H) . ¹³C{¹H} NMR (76 MHz, CDCl₃): δ 140.7, 140.3, 135.8, 128.9, 128.2, 128.1, 127.5, 126.6, 50.6, 42.2, 20.9. HRMS (ESI) m/z: [M + H]⁺ C₁₇H₂₀N calcd for 238.1590; found, 238.1577.

Style of an Experimental section

Divide the Experimental into separate sub-sections, each of which describes one experimental procedure performed.

Always write methods in the past tense, passive voice.

For solutions, provide the final concentrations of components rather than a full recipe of stock solutions and individual volumes. Only describe a recipe if an alternative method for making the solution will generate different experimental results.

• Correct and preferred: "Reactions were performed at 25 °C in 50 mM Tris-HCl (pH 7.1) with 4.0 μM imiginin, 20 μg/ml imaginase, and either 0 or 150 mM MnCl₂."

• Correct but unnecessary: "Reactions were performed at 25 °C in by mixing 500 μl of 100 mM Tris-HCl (pH 7.1), 10 μl of 400.0 μM imaginin, 100 μl of 200 μg/ml imaginase, and either 0 or 250 μl of 500 mM MnC₂ to a final volume of 1000 μl using buffer to make up the difference."

• Incorrect: "Reactions were performed at 25 °C by mixing 500 μl of 100 mM Tris-HCl (pH 7.1), 10 μl of 400.0 μM imaginin, 100 μl of 200 μg/ml imaginase, and either 0 or 250 μl of 500 mM MnCl₂." This example is ambiguous because it leaves-out the final volume.

Center equations on their own line with an equation number in parentheses to the right.  Visit Data Presentation (Appendix A) for equation style rules. Visit Shortcuts (Appendix E)  to learn how to type equations in Microsoft Equation Editor without using your mouse.

You may use formulas for common inorganic reagents such as NaOH, HCl, H₂SO₄, MgSO₄, etc., and for common organic solvents with very few carbons such as CH₂Cl₂ (dichloromethane) and CHCI₃ (chloroform). Do not use formulas if they are not readily interpretable or if they take as much space as the name itself (e.g., use n-hexane, not CH₃CH₂CH₂CH₂CH₂CH₃).

Quantities are assumed to be representative of a typical experiment/reaction, and three significant digits of precision for quantities is generally sufficient. Higher precision details for specific experiments should be reported as Results or in a Supporting Information section.

Likewise, do not report the uncertainty of quantities, uncertainty of ±1 unit in the last digit is assumed.

Do not begin sentences with numerals, formulas, or abbreviations. The Style Section of this writing guide contains advice for recasting a sentence to avoid this common tendency.

 

Examples