As the first section in the body of your paper, the introduction sets the stage for your project. In convincing readers that your research project is important and relevant, it serves many roles, including:

  • introducing your general area of research
  • describing key elements of this area that are relevant to your project
  • showing how your work fits into and adds to previous work in this area
  • and summarizing the contribution(s) of your findings to this area.

This sounds like a lot, but because you will write your Introduction after you have written your Methods, Results, and Discussion sections, you should already be well versed in this information by the time you start writing it. Let’s start by taking a look at a sample introduction.


From “Heterogeneous heck catalysis with palladium-grafted molecular sieves” (Mehnert, Weaver, and Ying 1998):

Recently discovered hexagonally packed mesoporous molecular sieves1 (designated MCM-41) are of great interest to catalysis because their large and uniform pore sizes (20-100 Å) allow sterically hindered molecules facile diffusion to their internal active sites. These nanostructured materials have a well-defined cylindrical pore structure and ultrahigh surface areas of up to 1200 m2/g, which make them excellent supports for a new generation of heterogeneous catalysts.2 This research focuses on the synthesis and application of modified mesoporous materials3,4 that have an active species attached to the framework via host-guest interactions, creating discrete and uniform sites on the inner walls of the porous systems. Due to their large pore sizes (>20 Å), these molecular sieves are of particular interest for catalysis involving bulky substrates, which have been a challenge for zeolitic materials due to their pore opening restrictions (4-12 Å). We have focused our attention on carbon-carbon coupling reactions (Heck catalysis)5 whereby palladium is used for the olefination of aryl halides with vinyl substrates, forming bulky coupling products. Heck catalysis is one of the most versatile tools in modern synthetic chemistry and has great potential for future industrial applications. Although recent advances in homogeneous6 and heterogeneous7 Heck catalysis have attracted considerable attention, these catalysts currently suffer from several drawbacks, such as low turnover numbers (TON) and limited lifetime.8

Herein we report the synthesis and characterization of palladium-grafted mesoporous materials, designated Pd-TMS11, and their evaluation as heterogeneous catalysts for Heck reactions of activated and nonactivated aryl substrates.


Although this is an especially short introduction, notice that the authors manage to cover each of the bulleted items above. The first paragraph introduces and explains the background topic (hexagonally packed mesoporous molecular seives) and moves into greater detail about Heck catalysis, the subject of the current project. In the second paragraph, the authors summarize exactly what was accomplished in the project (synthesis and characterization of Pd-TMS11) and and convey how it is relevant to Heck catalysis.



Audience and purpose


We’ve already started discussing the general purpose of an Introduction section. Ultimately, your primary goal is to explain why your research is important to and relevant in your field. To accomplish this, scientific writers must situate their project within other work that has led up to the research at hand. This tactic helps draw readers in using information they might already be familiar with and also provides context for why they should be interested in the findings presented within the paper.

To start to understand these purposes, we recommend that you try the practice exercise below.


Practice exercise

Read the following journal article introduction sections. For each, explain in your own words:

A. Why is the current work important?
B. How is the project related to previously published work?

  1. (Adapted from Lee et al. 2009) The Himalayan–Tibetan orogen, formed by the collision of India with Asia, is the most outstanding natural laboratory for studying the complex geologic processes through which collisional orogenesis evolves.1 Before the collision, northward subduction of the Neotethyan oceanic lithosphere under South Asia gave rise to an Chilean/Andean type convergent margin.2 Extensive igneous rocks thus produced in southern Tibet are now exposed as the Linzizong volcanic successions and Gangdese batholith in the Lhasa terrane, north of the Yarlu Tsangpo suture zone (Fig.1). In the terminal stage of this subduction, or its transition to the India–Asia collision, which may have involved attempted continental subduction,3 breakoff of the subducted Neotethyan oceanic slab from the adherent, more buoyant Indian continental lithosphere would have taken place as a result of gravitational resettling and strain localization.1 The timing and consequence of the slab breakoff in the Himalayan–Tibetan evolution have therefore attracted attention, such that it has been proposed as occurring in either the Eocene4,5,6 or the Oligocene–Miocene,5,7,8 corresponding specifically to the Eohimalayan metamorphism and the potassic magmatism in southern Tibet, respectively. By conducting a detailed geochronological study combined with petrochemical analyses, we report here for the first time the temporal–spatial and geochemical systematics of the Linzizong volcanism. The new data identify a significant igneous “flare-up” record in southern Tibet for constraining not only the Neotethyan subduction but also the geodynamic evolution in the region.

  2. (Adapted from Kleeman, Riddle, and Jakober 2008) The integrated mass of airborne particles with an aerodynamic diameter smaller than 2.5 μm (fine PM; PM2.5) is statistically associated with excess human mortality (see, for example, refs 1 and 2). Understanding the exact mechanism of injury associated with PM2.5 will likely require further understanding of the particle size distribution shape below 2.5 μm, since changes in aerodynamic diameter in this range strongly influence deposition patterns in the respiratory system (3). Numerous investigators are currently searching for the source(s) of airborne particles whose size and composition cause adverse health effects, so that emissions from these sources can be controlled to protect public health.

    Molecular markers are widely used in particulate matter source apportionment studies because organic compounds exist that are specific to individual sources leading to enhanced resolution (4). Studies on the organic composition of particles emitted to the atmosphere have identified molecular markers for major sources such as motor vehicle exhaust (see, for example, refs 5–8), biomass combustion (see, for example, refs 9–11), food cooking (see, for example, refs 12–15), and so forth. Recent studies have examined the size distribution of molecular marker emissions below a 2.5 μm aerodynamic diameter, with the objective to build a profile library for size-resolved source apportionment calculations (-16-18). Corresponding measurements of ambient molecular marker size distributions at receptor sites during air pollution events are needed to complete the data set needed for these calculations.The Central Valley of California routinely experiences some of the highest PM2.5 concentrations in the United States, rivaling those measured in Los Angeles, where the population is 5 times larger. The most severe PM2.5 episode in recent Central Valley history occurred between December 2000 and January 2001 during the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) (19). Measured PM2.5 concentrations during CRPAQS exceeded 200 μg m−3 (19) (5.7 times the current National Ambient Air Quality Standard of 35 μg m−3) The purpose of the current study is to describe the size distribution of molecular markers during CRPAQS in support of future size-resolved source apportionment studies.

  3. (Adapted from Far and Sczakiel 2003) The increasing use of siRNA to specifically suppress target gene expression in mammalian cells progressively reveals an influence of local target characteristics on the biological effectiveness (1-3). In major part, this is assigned to characteristics of the local folding of target RNA (1-3) and a recent study indicates to some extent a similarity between the site‐dependent biological activity of phosphorothioate‐derived antisense oligonucleotides (asON) and siRNA (3). When taken together, these findings on target structure‐related biological activity of siRNA in mammalian cells, raise two increasingly relevant questions. First, what are the rules governing the structure–function relationship of siRNA and, secondly, can one find ways to distinguish effective and non‐effective siRNA constructs on the basis of target structure analysis. The latter issue guides one to the systematic design of effective siRNA.

    Since siRNA is regarded to be highly sequence‐specific (4), it is reasonable to assume that a recognition step occurs between siRNA and its target sequence. This step might occur between the siRNA double strand and the target or subsequent to a possible preceding dissociation of the siRNA with its antisense strand. The local target RNA segment has to be accessible to intermolecular nucleotide–nucleotide interactions with siRNA or its antisense strand, respectively. There is a need to find a mammalian test system and experimental conditions to study the influence of target structure on the activity of siRNA.

    Here, we used the human gene ICAM‐1/CD54, which is one of the best studied targets for antisense nucleic acids (5,6), and siRNA (3) to investigate the extent of apparent gene expression in relation to local target accessibility. Target gene suppression in this system is reproducible and robust. Regarding RNA folding of the complete ICAM‐1 mRNA, we had access to a highly systematic computational RNA secondary structure analysis (6). Even a less detailed analysis was earlier shown to give rise to results that are highly consistent with structural probing of RNA in the presence of cellular extracts (7), suggesting that the theoretical analysis of target accessibility as performed here and as described recently (6), represents a valid basis to study the relation between accessibility and efficacy of siRNA. However, as an additional measure of the reliability of this kind of computational analysis of target accessibility, we included asON in this study. Furthermore, asON were used here to compare their effectiveness with siRNA on a quantitative level.


Notice that in each of the examples in the Practice Exercise, information begins with more general topics and becomes increasingly specific to the current work. This is because the introduction also begins by addressing a student audience, gradually serving more scientific and expert audiences. The amount of space reserved for the general audience will vary from sometimes just a single sentence to a few paragraphs depending on the primary audience of the journal itself. So how you want to proportion the amount of information for each audience in your own papers for class is mostly up to you (and your professor!) as long as you be sure to include some information directed at each and that it narrows from general to expert throughout.


Test yourself

Read the following Introduction section adapted from Varanka, Hjort, and Luoto (2014). For each numbered section (1 – 7), decide if the passage is directed at mostly a student, scientific, or expert audience. Briefly explain why you made each choice.

(1) Each catchment forms a unique combination of landscape characteristics which all have their impact on water quality in rivers. Therefore, water quality is the result of countless landscape factors, which are either natural or anthropogenic in origin or the interaction of these two factors. The importance of human activities, especially in the form of land use, is generally studied and recognized.1,2,3 (2) For example, agriculture can decrease water quality directly by nutrient leaching.4 Human activities can also change catchment characteristics and affect water quality indirectly. In areas affected by agriculture this can be seen among other things as reduced water infiltration ability of soil.5

(3) The influence of natural originated landscape factors on water quality has also been widely studied. Geomorphological characteristics such as slope or elevation6,7,8 as well as the cover of soil or bedrock9,10,11 or all of these in a multivariate setting, have been found to affect water quality.8,11 As these features interact in complex ways, also with land use factors, it is crucial to understand their effects on water quality. Some controlling factors can be managed and others cannot12 or management differs from others. (4) For example, many watercourses in high-latitude regions are naturally acidic because of thick peat deposits4 and the draining of these soils has increased problems caused by acidification. In these circumstances, restoration actions should be selected by taking into account both the natural and anthropogenic factors affecting water quality. In addition, soil and other natural catchment characteristics often guide land use activities in a certain area. (5) Therefore, it is important to explore the role of these natural attributes on water quality in a more detailed manner. This might improve our understanding of the relationship between catchment characteristics and water quality as well as to optimize and implement the most applicable restoration actions.

(6) Owing to the European Union (EU) Water Framework Directive, established in 2000 aiming to achieve good surface water status by the year 2015,11 member states have been forced to pay increasing attention to the condition and status of water systems.13,14,15,16 Geographic information system (GIS)-based methods combined with statistical analyses and modelling are widely used and effective approaches when studying water systems.14,17 (7) These methods enable investigation of the multi-scale relationship between environment and water quality and forecasting possible changes in the future. One potential method in this field is the non-metric multidimensional scaling (NMDS) method, which is commonly used by ecologists.18,19 NMDS is a data reduction technique,20 and it has been considered as a flexible tool complementing other study methods.21


  1. Student
  2. Student/Scientific
  3. Scientific
  4. Expert
  5. Expert
  6. Expert
  7. Expert


When addressing your changing audiences, you are also moving to accomplish various specific purposes. You will learn how to accomplish each of these moves in detail in our section on Organization, below. But it is important to keep in mind that who your target reader is, what they know, and what they are interested in knowing changes throughout your Introduction (as well as throughout your paper).


Purposes within the Introduction and the audiences each commonly addresses*
Purpose Audience
Introduce the area of research Student
Explain the importance of the research area Scientific
Highlight relevant, precedent works Expert
Justify the need for the current work Expert
Introduce the current work Expert

* Adapted from Robinson et al. (2008)


These specific audiences and purposes are not set in stone, but they serve as a good guideline for most journal-article-style papers you will write in your career. As always, both factors will depend largely on your topic and the journal in which you publish.



Style and conventions


Setting the context with literature works


One of the most important parts of the introduction is using previously published works to situate your project in scientific context. The more general information at the beginning of your introduction can be derived from other scientific works such as textbooks (which do not need to be cited). Depending on your topic, data from a governmental organization or from documents like patents and permits can be appropriate, too. But most of the background for your topic should almost always come from peer-reviewed, primary research articles.


To utilize information from these sources, you need to be able to paraphrase. This means that instead of directly quoting a paper or document, which can take up a lot of valuable space, scientists use their own words to convey only the most important pieces of information.


Tips for good paraphrasing

  • Pick out only the most important piece(s) of information from the passage and make note of them.
  • When you take notes, avoid copying the text verbatim. Using your own words in your notes will help you paraphrase the ideas when you write your own paper.
  • Be sure that you’re not only changing the (non-critical) words the original author used but also the sentence structure. Minor alterations to another’s statement, even with a citation, is still plagiarism.
  • Cite it. Even when it’s paraphrased, the idea/information is not your own.


Below is an example of paraphrasing adapted from He and Klionsky (2009).

Original passage: The ER is the key compartment in the cell to facilitate folding of newly synthesized proteins and initiate the pathway of vesicular movement of membrane and proteins to various organelles and the cell surface. In mammalian cells, the ER also serves as the major intracellular Ca2+ reservoir. A number of ER stress stimuli, for example, expression of aggregate-prone proteins, glucose deprivation (resulting in reduced glycosylation and decreased energy for chaperone activity), hypoxia and oxidative stress (causing decreased disulfide bond formation), and Ca2+ efflux from the ER, lead to the accumulation of unfolded proteins in the ER, which exceeds its folding capacity. An increasing number of studies indicate that autophagy is induced by ER stress in organisms from yeast to mammals. However, the signaling mechanisms linking ER stress to autophagy vary, dependent on the specific stress conditions and the organisms being studied.

Plagiarized version: A key component of the cell is the ER, which takes part in the folding of newly synthesized proteins and initiates the trafficking of membrane and proteins to organelles and to the surface of the cell. In addition, the ER is the primary reservoir for Ca2+ among cells. Unfolded proteins will accumulate in the ER as a result of various stressors including aggregate-prone protein expression, glucose deprivation, hypoxia and oxidative stress, and Ca2+ outflow from the ER, which can lead to autophagy in numerous organisms. The signaling mechanisms that link ER stress to autophagy vary, however, depending on the conditions of the stress and the study.

Appropriately paraphrased version: Although the ER critically folds newly synthesized proteins in the cell, stressors such as oxidative stress and low glucose levels can cause over-accumulation of unfolded proteins. ER stress can in turn cause autophagy through a variety of signaling mechanisms.


Notice that good paraphrasing also helps with conciseness, which you can read more about here.

For more help with paraphrasing, visit our page “How do I find and use the literature?



Focusing on the science, not the scientists


Especially in the literature review portion of the introduction, novice writers have a tendency to discuss the scientists involved and the process of them conducting research, such as in the following paragraph:

Researchers have only studied spin states in quantum dots by measuring the average signal from a large ensemble of electron spins. In contrast, we are aiming in this experiment to conduct a single-shot measurement of the spin orientation (parallel or antiparallel to the field, denoted as spin-↑ and spin-↓, respectively) of a particular electron; we are making only one copy of the electron available, so no averaging is possible. In their 2001 paper, Bing et al. revealed that this spin measurement relies on spin-to-charge conversion, which can be followed by charge measurement in a single-shot mode as shown by Frayche et al. (1998). Figure 1a schematically shows a single electron spin confined in a quantum dot (circle). (Adapted from Elzerman et al. 2004)

However, in the context of a journal article, the research itself is more objective (and important!) than the people conducting it–we leave references to the scientists to the Literature Cited section whenever possible. To focus your paper on the science, be sure to use personal pronouns sparingly and avoid explicit author references (which does not include in-text citations, of course!). Here is an improved version of the excerpt above:

Spin states in quantum dots have only been studie by measuring the average signal from a large ensemble of electron spins. In contrast, the experiment presented here aims to conduct a single-shot measurement of the spin orientation (parallel or antiparallel to the field, denoted as spin-↑ and spin-↓, respectively) of a particular electron; only one copy of the electron is available, so no averaging is possible. The spin measurement relies on spin-to-charge conversion followed by charge measurement in a single-shot mode. Figure 1a schematically shows a single electron spin confined in a quantum dot (circle).


Note: “We” is appropriate in some instances, but not in others. Taking the scientists out of the science helps a statement become more objective, but taking them out of a personal insight or decision can be downright confusing. For example, saying “It was believed that this project was important” isn’t any more objective than saying “We believed that this project was important,” but the latter statement is less awkward and more straightforward.

For more help with maintaining objectivity, see this page.


Test yourself

Re-write the following passages to focus on the science instead of the scientists.

  1. In 2001, Terjakin et al.26 identified pre-MS star, before its recent eruption, in L1630 as the exciting source of a chain of extended emission nebulosity that appears to terminate at a shock-excited Herbig–Haro object (HH 23). (Adapted from Elzerman et al. 2004)
  2. However, the Government Accountability Office has determined that CMT inversions do not adequately describe the spatial extent of rupture because they assume a point source, causing  tsunami forecasts to be inaccurate for coastal communities at risk. (Adapted from Wei et al. 2014)
  3. Numerous groups, including Stepho & Cartwright (1982), have used condensation of a dipyrromethane with an aldehyde in a MacDonald-type 2+2 condensation, as illustrated in Scheme 1, to prepare a wide range of meso-substituted trans-porphyrins.14 (Adapted from Littler et al. 1999)
  4. We have recently reported the mitogenic effect on the liver of acute exposure to lead nitrate.11 (Adapted from Ledda-Columbano et al. 1983)
  5. Hence, it is possible for us to control their electronic and optical properties and in particular, the absorption and/or emission wavelengths by modifying their composition or sizes [21–23].(Adapted from Neubauer et al. 2015)
  6. Since xylitol is transformed into xylulose 5-phosphate in the cells, we suggest that glucose acts on glucose-responsive genes in the liver, and probably adipocytes, through the nonoxidative branch of the pentose phosphate pathway.(Adapted from Doiron et al. 1996)


  1. Before its recent eruption, the pre-MS star in L1630 had been identified as the exciting source of a chain of extended emission nebulosity that appears to terminate at a shock-excited Herbig–Haro object (HH 23).26
  2. However, since they assume a point source, CMT inversions do not adequately describe the spatial extent of rupture, causing tsunami forecasts to be inaccurate for coastal communities at risk (Govnment Accountability Office, 2006).
  3. Condensation of a dipyrromethane with an aldehyde in a MacDonald-type 2+2 condensation,13 as illustrated in Scheme 1, has been used to prepare a wide range of meso-substituted trans-porphyrins.14
  4. Correct as is–the authors are referring to their own previously published work, so it is acceptable to use “we” or “our.”
  5. Hence, it is possible to control their electronic and optical properties and in particular, the absorption and/or emission wavelengths by modifying their composition or sizes [21–23].
  6. Correct as is–the authors are presenting a hypothesis, which is by nature a subjective remark, so the use of “we” is acceptable.



Writing fluidly


Using linking words and phrases can be most helpful in the introduction because you want to connect a variety of ideas together in a way that leads your reader from general topics all the way to your own project. When used correctly, these types of phrases will allow your introduction to lead readers fluidly through the story of the scientific process.


Examples of using connecting words to create fluidity

For example, increased cholesterol is known to suppress Na permeability of membranes containing high cholesterol (40%), but to enhance it in cholesterol-poor membranes (5%).5  Moreover, recent evidence from model membranes demonstrates that various physical properties of cholesterol-poor membranes. (Adapted from Ridsdale et al. 2006)

More recently, experiments have been carried out to study the behavior of turbidity currents in channel bends. (Adapted from Weill et al. 2014)

Furthermore, CuO nanoparticles enhance the catalytic activity and selectivity of ZnO in hydration and dehydration reactions and hydrogenation reactions such as methanol synthesis [12]. (Adapted from Subhan et al. 2015)


The toxicity of the hydroxybenzoate PSTs (GC toxins) is not well known; however, radioreceptor binding studies using rat brain synaptosomes enriched for sodium channels showed high affinity binding in previous studies [15]. (Adapted from Costa, Robertson, and Quilliam 2015)

It is possible that the various methods probe different physical interfacial domains within the soil, although studies have not specifically examined this phenomenon in detail. (Adapted from Costanza-Robinson and Brusseau 2002)


While concise linkages like “thus” and “however” aid sentence flow, many types of transitional statements are wordy and don’t contribute much meaning to your statement. Try to avoid using superfluous linking phrases similar to those in the table below.


Transitional phrases to avoid
  • “actually”
  • “it is interesting to note that”
  • “it was discovered that”
  • “these results show that”
  • “as already stated”
  • “as shown in previous studies”
  • “it is important to realize”
  • “note that”
  • “in conclusion”
  • “it has been found that”
  • “it has been long known that”
  • “it may be said that”
  • “it was demonstrated that”
  • “it is worth mentioning at this point that”



Parallelism, or parallel structure, is another great strategy for creating fluidity. Parallelism helps ideas flow smoothly and helps readers form connections and/or distinctions between these ideas using precise sentence structure. Below is an example of using parallel structure to make especially clear comparisons between different conditions:

Under dry conditions the principal controls on evapotranspiration are plant-available water and canopy resistance. Under wet conditions the dominant controls are advection, net radiation, and turbulent transport. Under intermediate conditions the relative importance of these factors varies depending on climate, soil, and vegetation. (Adapted from Zhang, Dawes, and Walker 2001)

We can also utilize the word “respectively” to connect even larger groups of ideas together concisely.

a. The FcH+/FcH oxidation potential was negatively shifted by 110 mV upon addition of an excess of pyridine, moved in the negative direction by 140 mV with excess imidazole addition, or, with the addition of excess 2-methylimidazole, shifted negatively by 150 mV. (Adapted from Vecchi et al. 2015)

b. The FcH+/FcH oxidation potential was negatively shifted by 110, 140, or 150 mV upon addition of an excess of pyridine, imidazole or 2-methylimidazole, respectively.

Note: Try to only use “respectively” when it is necessary to understand your meaning. Novice writers tend to use it whenever they can, which ultimately detracts from conciseness.


While parallelism and linking words can create fluidity when used properly, their over-use can become repetitive and detract from overall fluidity, too. This is evinced in the following example from Doiron et al. (1996):


However, insulin can be replaced in hepatocytes by transfection of a glucokinase expression vector (13). Furthermore, insulin is not necessary in the glucose-responsive hepatoma cell lines in which glucokinase is replaced by other isoforms of insulin-independent hexokinases (14). However, the pathway by which glucose-6-phosphate activates transcription of the L-PK gene and other glucose-responsive genes remains unknown. In adipocytes, the glucose analogue 2-deoxyglucose (transported in the cell, phosphorylated into 2-deoxyglucose-6-phosphate but was not further metabolized in the Embden Meyerhoff pathway) has been shown to stimulate expression of the fatty acid synthase and acetyl-CoA carboxylase genes (15). Similarly, 2-deoxyglucose can activate the L-PK promoter in the insulinoma cell line INS-1 (16), but not in hepatocyte or hepatoma cells (14). However, the efficiency of 2-deoxyglucose in mimicking the glucose effect in some cells does not signify that the observed induction was mediated by 2-deoxyglucose 6-phosphate itself. Indeed, although its isomerization into fructose-6-phosphate is impossible, 2-deoxyglucose 6-phosphate is partly further metabolized into various compounds (17, 18). Therefore, it does not rule out the involvement of intermediates rising from 2-deoxy-glucose-6-phosphate, especially through the pentose phosphate pathway.


To avoid this kind of repetition, be sure to vary your sentence structure and try to use linking words only where most helpful and appropriate.




Remember how the overall structure of the journal article is like an hourglass? (If not, see “Organization” in our overview of journal articles.) The introduction serves as the top part of the hourglass, starting with broad topics and then narrowing to the scope of the study itself. This organization not only ensures that readers have the foundation of knowledge they will need to understand your project but also is key for drawing in readers with something they are familiar with or already interested in and showing them how this concept connects to your project.


Move structure


The move structure of the introduction always moves from the most general to the most specific information about your project. (In your discussion, you should mirror this pattern so that both the very beginning and very end of your paper connect your project to the greater scientific world.)


Journal Intro MS


1. Describe the background of your study. Throughout Move 1 you should be citing relevant literature. Submoves (i) and (ii)  should only take a sentence or two each, while submove (iii) may consume a couple of paragraphs. Use submove (iii) to situate your specific work within the literature. But remember, this is a very general part of your introduction, so you usually shouldn’t mention your study yet!


Adapted from Puzon et al. (2005)

(i) Chromium is one of the United States’ most important and strategic metals (1). Hexavalent chromium [Cr(VI)] is widely used in industrial processes such as stainless steel manufacturing, chrome plating, leather tanning, wood treatments, dyes, and pigments. (ii) Because of its wide usage, Cr(VI) has been released into the environment in large quantities, posing a severe environmental problem (2). Cr(VI) is a known contaminant at 1036 of the 1591 National Priority List sites in the United States (3). In the environment, Cr(VI) typically forms oxyanions, for example, chromate, at neutral pH, which are highly soluble and mobile in groundwater (4).

(iii) Chromate can readily cross cell membranes (5), and human exposure is a considerable health issue. In the cytoplasm, chromate is converted to reactive Cr(V) and Cr(IV) species as well as stable Cr(III)−DNA adducts, causing mutation and cancer (6). In contrast, the inorganic trivalent chromium [Cr(III)] salts are typically insoluble (7, nontoxic, and even used as food supplements (8). To minimize Cr(VI) contamination, various methods of converting Cr(VI) to less toxic Cr(III) have been investigated, including bioremedia tion. However, identification and understanding of the Cr(III) end-product have largely been ignored.


2. Identify the gap(s). Now you can introduce your project by identifying a “gap,” or something that remains to be done or learned considering all of the background you just gave in Move 1. We can see a gap statement in context using the same paper we looked at for Move 1:


(Move 2 is in bold)

Chromate can readily cross cell membranes (5), and human exposure is a considerable health issue. In the cytoplasm, chromate is converted to reactive Cr(V) and Cr(IV) species as well as stable Cr(III)−DNA adducts, causing mutation and cancer (6). In contrast, the inorganic trivalent chromium [Cr(III)] salts are typically insoluble (7), nontoxic, and even used as food supplements (8). To minimize Cr(VI) contamination, various methods of converting Cr(VI) to less toxic Cr(III) have been investigated, including bioremedia tion. However, identification and understanding of the Cr(III) end-product have largely been ignored.


A gap might be a lack of understanding about how well a particular instrument works in a certain situation. It could be introducing a new method that needs to be tested. Or it could be that you are studying a whole new organism, system, or part of a process.

In a class, you might not always be studying something brand “new.” But you should still try to come up with something unique about your project, however small. Talk to your professor about what they expect for your “gap statement” if nothing seems to work.


An example gap from Hosaka, Itao, and Kuroda (1995):

“… The relationship between the four damping factors, i.e. internal friction, support loss, airflow force in free space, and squeeze force, has not yet been clarified, so it is not obvious which one is  dominant in actual microsystems.”


Here, the authors signal to us that this is a gap because they use the words “has not yet been clarified.” Other phrases that might help you identify (or form!) a gap statement are:

  • …has/have not been… (studied/reported/elucidated)
  • …is required/needed…
  • …the key question is/remains…
  • …it is important to address…



3. Fill the gap(s). Once you identify the gap in the literature, you must tell your audience how you attempt to at least somewhat address this lack of knowledge or understanding in your project. This is often done in a new paragraph and should be accomplished in one summary statement, such as:

“Therefore, the purpose of this study was to determine the effects of lead on the hepatobiliary system, especially on the liver and on the gallbladder.” (Adapted from Sipos et al. 2003).

You’ll often find that the first sentence of the last paragraph in a paper’s introduction will start somewhat like this, indicating the gap fill.


Some phrases you can use to indicate your gap “fill:”

  • “We therefore analyzed…”
  • “In this study, we investigated…”
  • “Therefore, the goals of this study are…”
  • “In this paper, we report…”


Remember–always keep your voice professional! Colloquial phrases such as “we looked into” or “we checked if” should be avoided when introducing your gap fill.

So let’s look at this idea in context by looking at some examples from a couple of types of papers. The gap statements are underlined; the fills are italicized.


Adapted from Monthioux et al. (2001):

Though ideally expected to be chemically very stable due to the poor reactivity of the basal aromatic plane from which SWNTs are built, the question of whether all the chemicals which are now currently proposed in the literature as purifying, suspending, or grafting agents for SWNTs actually have a limited effect on the SWNT integrity has to be addressed. In this paper, we report the investigation of the effects of some commonly used chemical treatments on SWNT structure by means of high resolution transmission microscopy (HRTEM). We also report the effect on purified SWNTs of an organic solvent, dimethylformamide, used to tentatively prepare SWNT suspension.

Adapted from Zhang, Dawes, and Walker (2001):

Milly’s work recognized the importance of storage capacity of the root zone in controlling evapotranspiration and has the postential for assessing the catchment-scale response of vegetation changes. However, the practical application of this model is limited because of the complex numerical solutions required. The purpose of this paper is to quantify the long-term impact of vegetation changes on mean annual evapotranspiration at catchment scales based on data and parameters that are easily measurable at a regional scale.

Adapted from Lecoanet, Bottero, and Wiesner (2004):

A risk assessment of the potential impacts on health and environment that the production, use, and disposal of nanomaterials may engender requires information concerning both the potential for exposure to a given material and its (once exposed) potential impacts such as toxicity or mutagenicity. In this work, we address the issue of nanomaterial exposure and transport in experiments designed to assess their potential for migration in porous media such as groundwater aquifers and water treatment plant filters. 


In the second and third examples, the gap may be a little less obvious–it doesn’t use any phrases to signal to you that there’s something missing, such as “has not been clarified” or “have not been reported.” But because of the way the paragraph is laid out–following the conventions of our move structures–we can see that the underlined section of text is indeed the missing information in the literature that the group sought to address in their project.


Org-3: Test yourself

In the following examples, identify the gap statement. Then, identify the fill. Notice if there are any specific words or phrases used to signal either of these moves.

1. Adapted from Costa, Robertson, and Quilliam (2015):

Paralytic shellfish poisoning occurs worldwide, and harmful algal blooms, including those responsible for PSP, appear to be increasing in frequency and intensity. PSP outbreaks in Portuguese waters have been associated with blooms of Gymnodinium caenatum in the late 1980s to early 1990s, then again after 2005. According to the national monitoring program in Portugal, G. catenatum were not reported along the Portuguese coast during the 10-year period from 1995 to 2005. The aims of this study were to fully characterize the toxin profile of G. catenatum strains isolated from the NW Portuguese coast before and after the 10-year absence of blooms to
determine changes and potential implications for the region. Hydrophilic interaction liquid
chromatography tandem mass spectrometry (HILIC-MS/MS) was utilized to determine the presence of any known and emerging PSTs in sample extracts.

2. Adapted from Littler, Ciringh, and Lindsey (1999):

The exchange process frequently observed in polypyrrane condensations is proposed to occur by the acid-catalyzed fragmentation of a polypyrrane 1 into pyrrolic 2 and azafulvene 3 components.15 As illustrated in Scheme 2, recombination of 2 and 3 can form a new polypyrrane 4 that cannot be formed by direct condensation of the dipyrromethane and aldehyde. Ultimately this process leads to the production of a scrambled mixture of porphyrins. The factors that promote the scrambling process in MacDonald-type 2 + 2 condensations are poorly understood, but suppression of scrambling is essential for preparing large quantities of pure trans-porphyrins. In this paper we describe a study of a wide range of reaction conditions for the 2 + 2 condensation that has led to refined synthetic procedures for the preparation of trans-porphyrins.

3. Adapted from Pukhov and Meyer-ter-Vehn (2002):

In the present paper, we focus on laser wake field acceleration in a new, highly non-linear regime. It occurs for laser pulses shorter than λ(p) but for relativistic intensities high enough to break the plasma wave after the first oscillation. In the present relativistic regime, one should notice that the plama wave fronts are curved and first break new the wave axis and for lower values than the plane-wave limit. This has been studied in 2D geometry in [14-17]. Here, we present 3D PIC simulations of two representative cases. The case (I) is just marginally above and the case (II) is far above the breaking threshold.


Good gap and fill signaling phrases are italicized.


1. Gap statement: “The factors that promote the scrambling process in MacDonald-type 2 + 2 condensations are poorly understood….”

Fill: In this paper we describe a study of a wide range of reaction conditions for the 2 + 2 condensation that has led to refined synthetic procedures for the preparation of trans-porphyrins.”


2. This question is a little trickier! The authors use “In the present paper…,” then, “In the present regime…,” and finally, “Here…,” all of which sound like signaling words for filling the gap. But where is the gap? We have to look closely at what exactly is being said. It is true that the first statement appears to be somewhat of a gap fill, although they haven’t yet given us a gap statement. The authors go on to say “This has been studied in 2D geometry,” which brings us back to move 1(iii), identifying critical evidence from the literature.

Thus, the gap statement is not explicit. It is a combination of stating that this concept has been studied in 2D, followed by announcement that the authors will study it in 3D.
Fill: “Here, we present 3D PIC simulations of two representative cases.”

Although the first sentence (“… we focus on laser wake field acceleration…”) could also be considered part of the fill, because it comes before the gap statement and is also less descriptive, it functions more as an introduction to these moves.


3. Gap statement: “According to the national monitoring program in Portugal, G. catenatum were not reported along the Portuguese coast during the 10-year period from 1995 to 2005.”

Fill: “The aims of this study were to fully characterize the toxin profile of G. catenatum strains isolated from the NW Portuguese coast before and after the 10-year absence of blooms to
determine changes and potential implications for the region.”



Org-4: Practice exercise

Find 3-4 primary research articles (not reviews) from reputable journals in your field. Underline the gap statement and circle the gap fill. Remember that not all papers follow this exact move structure, so if you can’t seem to find either of these moves, you might have to look carefully at different parts of the introduction and ask yourself:

  • What concept are the authors trying to better understand? (This might point to a gap statement.)
  • What did the authors try to accomplish in the paper, in summary? (This might point to a fill.)