ABOUT SCIENTIFIC WRITING



ABOUT SCIENTIFIC WRITING: Materials & methods and Introduction Sections

You will be writing a lab report in the style of a scientific literature article. These are papers that scientists write, review and publish to present the results of their experiments to other scientists. There is an expected and accepted format and writing style for these papers, and if you were to submit a paper for publication in any other format, it would not be considered for review or printing in a journal. As you are learning to be a scientist, it is important that you be able to understand the important literature and learn to communicate your findings to the scientific community acceptably.

Like the format of all scientific papers, your lab report will consist of 5 sections (in this order): abstract, introduction, materials & methods, results, discussion; plus a list of literature cited. It is suggested that as you begin to write, you approach your report in the following order: materials & methods, introduction, results, discussion, abstract. Here are some hints on the first two sections you should approach:

Materials & Methods

This section will include information on HOW you did your experiments. DO NOT include in this section: WHY you did something; or what you expected to find; or any discussion of what you found – just HOW you did it!

This will not be a list of steps or “recipe,” as your lab handouts have been. Rather, this is written as a narrative in the passive voice; that is you don’t say “I measured 100 mL of water.” Instead write “100 mL of water was measured.” See Appendix 1 for an example of a procedure from my research lab, and how the student rewrote the directions for the purposes of publication. For your paper, you will need to rewrite the step-by-step directions in your lab handout in narrative form, including the most pertinent information, so someone else could repeat your method.

Note that you don’t have to mention all the instruments or equipment you used, unless it is something unusual. Common lab equipment that other scientists are expected to understand are: beakers, flasks, graduated cylinders, glass pipettes, micropipettors, weigh boats or papers, balances. Brands and models of major instrumentation should be noted. Also note that journals usually require that brands and lots of reagents and chemicals used are noted. (You won’t have to do that for your lab reports, because we prepared the reagents for you, so you don’t know the brands and lot numbers from each bottle. We will provide you with recipes of solutions that you’ve used, however, if they’re not already in your handouts.)

Introduction

This section focuses on WHY you did your experiments. It should contain a brief background on the main topic of your experiments, including some information on what other researchers have discovered that laid the background for how you came up with your hypothesis; a statement of your hypothesis; and sometimes a brief statement on what and how you will do your measurements to accept or reject your hypothesis.

Appendix 2 has an outline of what my student presented in her introduction on why we extracted flavonoid phytoestrogens from herbal supplements that we’re in the process of writing up for publication.

Another example is based on one of the experiments your group might have done in lab this week: Testing the peroxidase near the stem of the celery vs. the tip of the celery stalk. For this experiment, your introduction might include what peroxidase enzyme is (what reaction it catalyzes); why it’s beneficial to the plant to have peroxidase enzyme; another researcher’s experiment that was published where more peroxidase enzyme was found near the stem of a carrot vs. the tip of the carrot; your hypothesis that the same would be true for peroxidase in celery; and mention that you used electrophoresis and nitrocellulose “stamping” techniques to examine your hypothesis.

When you mention the work of others, you MUST cite their publications. The format for literature citations differs for different fields. For example, in chemistry, each citation is numbered and superscripted within the text (e.g., “Smith1 found peroxidase enzyme in carrot stems”), then in the Literature Cited section, a list of all citations is numbered, with the first being Smith’s paper in our example. In biology, however, numbers are not usually placed within the text. Rather, the author’s name and the date of publication, or sometimes the date of publication alone are placed in parentheses within the text (e.g., “Smith (1998) found peroxidase enzyme in carrot stems” OR “Earlier research (Smith, 1998) found peroxidase enzyme in carrot stems”). Then, in the Literature Cited section, the citations are placed in alphabetical order according to the authors’ last names.

The format for literature citations you will use for your paper is the following:

Author’s Last Name, Author’s Initials. Year of publication. Title of publication. Journal Name, Edition: page numbers.

Example:

Smith, JB. 1998. Peroxidase Enzyme in Carrots. Journal of Enzymology, 14:145-150.

If there is more than one author:

Smith, JB, R Jones, BL Williams. Peroxidase…

Note that few punctuation marks are used in the names; this is to save space in printing.

If you use websites as references, you should include the http address, any title that is available for the article used, and the date you used the website.

Information regarding the Results, Discussion, and Abstract sections will follow by early next week.

Appendix 1: Extraction of Flavonoid Phytoestrogens from Herbal Supplements (from the method of Francke & Custer (1994)):

Directions

Open 2-4 capsules of supplement, or grind 2-4 pills in a mortar and pestle.

Weigh 1 g of powder from each.

Make up extraction solution: 77 mL ethanol + 5 g BHT + 7.29 g HCl (to make 2 M HCl solution) in 100 mL.

Mix each 1 g sample with 10.0 mL extraction solution.

Sonicate each solution 10 minutes (Branson 3200 sonicator).

Reflux 2 hours in a distillation apparatus.

Cool to room temperature.

Pour into 15 mL centrifuge tube.

Centrifuge at about 2200 rpm (850xg) for 15 minutes (Sorvall T 6000 D centrifuge).

Decant supernatant; store at –4oC until use.

Before analysis, pass solution through 45 micron syringe filter.

Materials & Methods in Paper to be sent for Publication

Flavonoids within the supplements were extracted according to the method of Francke & Custer (1994): 1 g of each supplement (2-4 capsules or pills) was mixed with 10 mL 77% ethanol solution (containing 0.05% BHT in 2M HCl. This mixture was sonicated approx. 10 min (Branson 3200 sonicator), then refluxed 2 h. Following cooling to room temperature, the mixture was centrifuged gently (850xg; Sorvall T 6000D) for 15 mins. The supernatant was collected and stored at -4oC until analysis, and thawed extracts were filtered through 0.45 μ syringe filters at the time of analysis.

Appendix 2: Outline of Introduction to the Publication “Analysis of Flavonoids in Botanical and Ephedra-Containing Dietary Supplements”

What are flavonoids?

Where are they found?

Chemical structure

Physiological effects of flavonoids

To the reproductive system

In cancer

Herbal supplements

What are they?

How are they used?

Lack of FDA regulation

Ephedra-containing supplements

Hypothesis paragraph:

Because herbal supplements are derived from plant material, and supplement production is not regulated for purity or activity, supplements may contain other compounds in addition to their proclaimed active ingredient. Among these unexpected compounds are bioflavonoids, which by virtue of their estrogenicity, may impact consumer health. This is especially important for botanical supplements marketed as weight-loss aids which are among the top-selling herbal products in the United States. Several months prior to the FDA’s 2004 ruling on ephedra, a study was undertaken to use high performance liquid chromatography to analyze 19 dietary supplements, including 10 ephedra-containing supplements, for the presence and concentrations of five flavonoids (biochanin A, daidzein, formononetin, genistein and quercetin).

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