Lab Report Writing Guidelines
by Dr. Justin Maresh, DePaul University

General

In this laboratory course, your lab reports will follow the form and style of a formal scientific paper suitable for submission to a professional journal. A good paper is an organized description of hypotheses, methods, data, and conclusions designed to inform the reader while providing sufficient detail for the reader to critically evaluate the quality of the work Without a paper documenting a research effort, the work done is not truly science.1 Without peer review and criticism scientific knowledge has little authority. Without a detailed paper, peer review is not possible. Critical examination of a peer's work requires carefully presented data and independent replication. Detailed published methods, help others replicate the work. Detailed explanations for how results were interpreted, allow others to reach different conclusions that may have been overlooked by the authors. For scientific knowledge to exist, scientists must be able to write clearly, precisely, and include sufficient detail.

Before you begin writing, always read the assignment and the Grading Rubric to make sure that you are including everything that is required. Once you have finished your report, compare it to the Grading Rubric again. Completeness is the most important thing to remember when writing your reports. In this course, it is not uncommon to leave lab with poor the data cannot be interpreted. It is understood that an experiment may not work well when you are doing it for the first time. Because of this, the penalty for an "incorrect" result is minor. However, if all your figures are missing labels and your Discussion fails to state whether or not your effort achieved the purpose of the lab, your total score will drop a full letter grade!

Department of Chemistry and Biochemistry considers the ACS Style Guide 2 to be the ultimate authority for the details of report writing. The ebook in PDF format is available on the D2L course site and at http://j.mp/acsstyleDPU. All advice in this document is consistent with the guidelines in that book.

Content of reports

Scientific papers are intentionally formulaic to facilitate the transfer of information to the reader. They consist of seven critical sections:  Abstract, Introduction, Experimental Procedures, Results, Discussion, Acknowledgements, and References. Within these sections, scientists have evolved reliable formulas to promote efficient communication. These are described in the corresponding sections of this document.

General formatting for reports

Models of reports

In this course, you will be held to similar standards that scientists hold their colleagues when submitting a research report for publication. The basis for your writing style will be the norms of the published literature for the course topic. You are encouraged to use peruse articles from recent issues of the journal listed in the table below to get a feeling for the requirements and learn by example.

Courses

Topic

Journal

Notes

CHE 13X

General chemistry

Journal of the American Chemical Society

Consult your course specific writing guidelines before this guide as there may be minor differences.

CHE 23X

Organic chemistry

Journal of Organic Chemistry

CHE 34X

Biochemistry

Biochemistry

 

References

  1. Whitesides G.M. (2004) Whitesides' Group: Writing a Paper. Adv. Mater. 16(15):1375-1377. DOI: 10.1002/adma.200400767
  2. Coghill A.M., Garson L.R.The ACS Style Guide: Effective Communication of Scientific Information. American Chemical Society: Washington DC, 2006. DOI: 10.1021/bk-2006-STYG
  3. Whitesides G.M. (2004) Whitesides' Group: Writing a Paper. Adv. Mater. 16(15):1375-1377. DOI: 10.1002/adma.200400767
  4. Kamat P., Schatz G.C. (2013) How to Make Your Next Paper Scientifically Effective". J. Phys. Chem. Lett. 4 (9): 1578–1581. DOI: 10.1021/jz4006916

 

Writing an Abstract

An abstract should be a specific summary of the paper or report. An abstract should be written in such a way that any reader who is not familiar with the topic will be able to understand and appreciate the main points of the study.

Content of an abstract

It should provide a brief summary of each of the main sections of the paper:

Style of an abstract

 

 

Writing an Introduction

The introduction section is the beginning of the body of your lab report. It is meant to provide an outline and purpose for the experiment that prepares the reader with the context to understand the experiments that will follow. This section should give the reader a detailed background on the "what" and "why" of the experiment, and put the experiment into a broader context. This context should be beyond this lab course and should not refer to the course itself, your instructors, or other students. Before writing your own introduction, you should review the examples below and try to find the parts described in a recent research paper from the journal Biochemistry.

Content of an introduction

As with most parts of a scientific paper, the introduction is highly formulaic. Broadly it contains two parts: the background and description of the experiment. Although there is some variation, most Introductions include all the points listed below in the approximate order shown. The first three points are background and the final three points pertain to the experiment.

Style of an introduction

Analysis of a sample Introduction from Biochemistry

This Introduction is much longer and more detailed than anything we will expect from you. However, it illustrates the above principles. It opens with the broader context (understanding HIV-1 PR is important for the development of therapies for HIV) in present tense with cited references as superscript numbers. In this example, limited past tense is used to give context to a specific subject. Throughout this example, I will omit extraneous text with an ellipsis (...).

The human immunodeficiency virus type 1 protease (HIV-1 PR) mediates the processing of the Gag and Gag-Pol polyproteins into mature structural and functional proteins essential for assembly and maturation into infective progeny virus.1-4 The HIV-1 genome encodes a single copy of the 99-amino acid protease. PR is translated in the pol open-reading frame and catalyzes its own release at its termini (autoprocessing) from the Gag-Pol polyprotein via transient dimerization (Figure 1A).1-3 ... The active site of the mature PR dimer has been the subject of intervention strategies for almost 25 years since its discovery, and clinical protease inhibitors form a crucial part of combination antiretroviral therapy.5-6

Next the authors present a brief review of the current state of knowledge. Note that the authors generally use present tense passive voice, but switch to past tense first person to describe their team's specific results.

However, the short replication cycle (1.2 days7) of HIV-1, together with the error-prone reverse transcriptase, contributes to the rapidly evolving selection of mutations in PR leading to drug resistance. Major and accessory mutations involving 37 of the 99 PR residues contribute resistance to clinical protease inhibitors in current use by several mechanisms.8,9 We recently characterized an extreme multidrug resistant clinical isolate of PR... We proposed that mutations at or near these sites, which significantly limit autoproteolysis, can prolong the lifetime of mature PR20, thereby compensating for its reduced catalytic activity during the viral replication cycle.26

The authors finish the current state of knowledge summary with an unanswered question followed by more background related to that question.

However, to the best of our knowledge, molecular mechanisms of drug resistance pertaining to autoprocessing, a pivotal step in PR regulation, have not been thoroughly explored. We recently characterized an extreme multidrug resistant clinical isolate...

In the last paragraph, the objective is stated. It is easy to identify by the use of "Here we" in the last paragraph.

Here we address the effects of clustered drug resistance mutations on a comprehensive set of properties, for the first time, such as the dimer dissociation constant (K dimer), kinetic parameters (k cat/K m and K i), thermal stability in the absence and presence of protease inhibitor, Gag processing, autoproteolysis, and autoprocessing governing PR function.

Finally, the experiment that will be described is explained.

Initially, we substituted all PR20 clusters (or cassettes) into PR and its precursor mimetic and, conversely, all PR clusters into PR20 and its corresponding precursor and examined the effect of these mutations on the mature protease. Kinetic parameters of PR-mediated hydrolysis of synthetic substrates were compared with the rate and order of Gag processing. Subsequently...

 

Analysis of a student sample Introduction

Read this complete sample Introduction written by a past student. Identify the (a) broader context, (b) current state of knowledge, (c) background of methods, (d) unanswered question, (e) objective of study, and (f) experiment. Mouse over each sentence to see if you are correct.

1 2+ and Zn 2+ at histidine residues positions 13 and 14. Such binding accelerates the rate of peptide aggregation and the formation of toxic fibrils and plaques.1

2+ binding site which includes 3 histidine residues. 2,3   Theoretical approaches have also been used to give information about the possible coordination intermediates between copper and Aβ peptide. 4

5 In ITC studies, ligand aliquots are injected into a sample of a macromolecule solution of known concentration to determine the heat released upon binding. This is measured indirectly by monitoring the power applied to the sample cell to keep the temperature difference between the sample cell and a reference cell constant. 6   Software has been developed that allows the determination of binding sites, ΔH values and equilibrium binding constants from the raw data generated from ITC experiments.

d) for the binding of Cu 2+ with Aβ is not known at physiological pH. d binding of Cu 2+ to the short Aβ peptide Aβ-(1-16) which contains the first 16 amino acid residues present in the complete peptide. 2+ binding but lacks the sequence critical for aggregation. Cu 2+ is only weakly soluble at physiological pH due to formation of a highly insoluble hydroxide species. 7 Thus, the binding affinity and thermodynamic parameters were measured at pH 5.5 and 6.0 in order to extrapolate thermodynamic parameters at a physiologically relevant pH.


 

Writing an Experimental section

 

Content of an Experimental section

Style of an Experimental section

Below is a student example of a well-written Experimental section:

 

 

Writing a Results and Discussion section

You will write a combined Results and Discussion section. However, you should know the different functions of each part. The two parts do not need to be separated by headings.

Keep you audience in mind when you write. Ostensibly, your audience is a general reader of Biochemistry, however you should also explain what happened with enough detail that your instructor can see that you understand the phenomena at play. 

Figures, tables, and schemes

In general chemistry (CHE 13X) labs and papers in my liberal studies courses, place figures, tables, and schemes after the paragraph in which they are first mentioned.

In my CHE 2XX and 3XX labs, you may simply present figures, tables, and schemes together at the start of the Results and Discussion section. When you submit a manuscript to a journal, you are responsible for the content only, professional layout designers will integrate your text and graphics appropriately to make sure that each graphic is placed where it fits on the page after its first mention in your text. Lab reports in these courses have so many figures and tables that they often break up the text too often. We do not want you spending any time on layout design to deal with this issue. If you prefer to incorporate your figures, tables, and schemes into the report text you will not be penalized.

Text

A. Always begin the text of this section by restating the objective of the experiment and whether or not you successfully achieved that objective.

B. The discussion of each experiment conducted should follow this formula...

  1. Briefly describe what was done
  1. Present the results
  1. Comment on the quality of your results and explain whether quality limits the ability to make a conclusions from it.

C. After discussing each experiment, summarize your discoveries.

D. Conclude by suggesting further work that should be performed.

  1. A great scientist is not someone who knows the right answers, but someone who asks the right questions. Every scientific experiment creates more new questions than answers. These last sentences of your paper set the stage for the next scientific explorations.
  2. If you did not completely accomplish your goals, identify what may have gone wrong, suggest a specific improvement, and explain why your improvement would reduce the effect of the problem you encountered.
  3. If you see no need for improvement, briefly suggest a follow-up experiment that builds on the current work.

 

Appendix A: Data Presentation

Uncertainty
Significant digits
Units
Figure format

Example of a good figure: 


imaginase activity

Figure 2. The initial rate of product formation as a function of imaginase concentration. Product formation was monitored by absorbance at 400 nm at 23 °C in 50 mM pH = 7.0 phosphate buffer. The trendline relationship is y = 5.03 (M·sec-1·mM-1imag) x + 0.0210 (M·sec-1) (R2 = 0.992).


Table format

Below is an example of a perfectly reported table taken from a random article in Biochemistry. Note that one guard digit is included on both the measurement and uncertainty. See above section on Uncertainty for more details.


Table 2. Binding and Antiviral Activities of DV1 and DV1 Dimer a

Analogue

CXCR4 binding (nM) b

antiviral activity using infectious virus assays (μM)

antiviral activity using single-cycle focal infectivity assays (μM)

DV1

43.0  ± 5.0

12.1  ± 3.2

24.03  ± 0.10

DV1 dimer

3.02  ± 0.52

4.4  ± 3.1

10.12  ± 0.49


a. The binding and antiviral activities of DV1 and DV1 dimer are shown by their IC50 values. All data are shown as means ± the standard deviation from at least three independent experiments.
b. 12G5 antibody competition binding assays were used to determine CXCR4 IC50 values. Stably transfected 293 cells were used in the binding experiments. The binding data were analyzed using PRISM (GraphPad Inc., San Diego, CA).


 References

  1. Croarkin C, Tobias P, editors (2012) Engineering Statistics Handbook. National Institute of Standards and Technology, U.S. Department of Commerce: Washington DC, Section 4.1.4. https://www.itl.nist.gov/div898/handbook/pmd/section1/pmd14.htm (accessed Aug 18, 2018).

 

Appendix B: Minimum Details to Report for Common Methods

The following are the critical details required to replicate common biochemical techniques. At minimum you must include these details in your methods and captions.

  

Appendix C: Citations

When to cite and reference

What to cite

Authoritative scientific knowledge resides in unchanging published peer reviewed documents that anyone can obtain. Therefore,

Instead, you should cite,

How to cite

Bibliographic format

Every journal has its own recommended bibliographic format. For this course, we will use the current format of the journal Biochemistry (n.b. this journal used a different format before 2004).

Article in a scientific journal

Kuo HH, Mauk AJ (2012) Indole peroxygenase activity of indoleamine 2,3-dioxygenase. Proc Natl Acad Sci USA 109: 13966 - 13971.

Article in a popular/ magazine

Manning, R. (May 2004) Super Organics. Wired, pp 176-181.

Article from an online journal

(no DOI exists)

Peacock-Lopez, E. (2007) Exact Solutions of the Quantum Double Square-Well Potential. Chem. Ed. [Online] 11: 383-393. http://chemeducator.org/bibs/0011006/11060380lb.htm (accessed Aug 23, 2007).

Whole book, single author

Chang, R. General Chemistry: The Essential Concepts, 3rd ed.; McGraw-Hill: Boston, 2003.

Edited Book

Gbalint-Kurti, G. G. (2004) Wavepacket Theory of Photodissociation and Reactive Scattering. In Advances in Chemical Physics; eds Rice, S. A. (Wiley: New York) Vol. 128, p 257.

Article from a reference book

Powder Metallurgy. In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., 1982 (Wiley, New York) Vol. 19, pp 28-62.

Web page

National Library of Medicine. Environmental Health and Toxicology: Specialized Information Services. http://sis.nlm.nih.gov/enviro.html (accessed Aug 23, 2008).

  Use Endnote to make citing easy

Endnote is a database in which you can store citation data. It works as a plugin to Microsoft Office. With Endnote you can insert citations into the text of your documents that link to an automatically formatted your References section. You can change the style of your citations and references with a few clicks. If you use Endnote, you can be confident that your references will always be formatted to meet the requirements of your assignment without thinking about it.

 

Appendix D: Scientific Style

Active versus Passive Voice

A sentence is said to be in active voice when the subject of the sentence is the doer of the action indicated by the verb. The subject of an active verb is doing the action of the verb. In passive voice, the subject is the receiver of the action indicated by the verb.

Verb Tense

Using the appropriate verb tense helps to orient the reader as to the nature of the information.

Language and tone
Scientific style

 

References

  1. "mass, verb." The Oxford English Dictionary Online. 2019. https://www-oed-com.ezproxy.depaul.edu/view/Entry/114670?result=7 (accessed 5 Sept 2019).

 

Appendix E: Pro Tips for Microsoft Word

Symbols in MS Word:

Type this

Becomes this

+-

±

>=

\ne or \neq

\mu

μ

\alpha

α

\degc

\times

×

\bullet

·

\lrhar (left right harpoons)

x\bar (overline)

 

Shortcut

Output

Name

Control+@ release, then press <space>

°

Degree symbol

Control+@ release, then press A

Ångstrom symbol

MacOS only: Alt+*

°

Degree symbol

 

Formatting in MS Word
Graphics