PNAS Formatting Requirements: Complete Author Guide

PNAS requires an abstract and also requires a separate Significance Statement. Both are mandatory for Research Articles.

Abstract:

• Word limit: 250 words maximum

• Purpose: Explain to the general reader the major contributions of the article

• Citations: If the abstract cites references, they are given in full within the abstract itself (PNAS's templates allow up to three) and also cited in the text

• Content: Should cover the motivation, approach, key results, and implications

Significance Statement:

• Word limit: 120 words maximum

• Audience: Written for a broad scientific audience, including scientists outside your field

• Jargon: Avoid field-specific terminology. If a term wouldn't be understood by a physicist reading a biology paper, rewrite it.

• Position: Published with the article, separate from the abstract

The Significance Statement is unique to PNAS and is one of the most common sources of revision requests. Editors take it seriously because it is the part of the package written for readers outside your specialty.

A good Significance Statement explains what the problem is, why it matters, and what your paper changes. It shouldn't just restate the abstract in simpler terms. Think of it as a pitch to someone at a different department's seminar.

Bad example: "We studied the role of protein X in disease Y and found it interacts with protein Z."

Better example: "Patients with disease Y have no targeted therapies. We identify a previously unknown interaction between proteins X and Z that can be blocked by existing drugs, opening a treatment path for the 200,000 patients diagnosed annually."

PNAS's author page states no figure cap, but figures consume page space: the preferred length is 6 pages (12 maximum), and PNAS may ask authors to shorten manuscripts that exceed the stated length requirement. In practice, most Research Articles have 4-6 figures.

Figure specifications:

Table formatting:

• Tables count toward the page limit

• Ensure the table is in an editable Word, RTF, or LaTeX format

• Include a brief title (above) and footnotes (below) the table

• Avoid multipart tables (Table 1A, Table 1B)

Color charges: PNAS's publication charges page lists no separate charge for color figures.

PNAS uses a numbered citation system, but with a distinctive format that differs from most biomedical journals.

In-text citations: References are numbered in the order they appear in the text. PNAS's author page and templates do not spell out the in-text marker (parentheses or superscript), so copy a recent PNAS article or the PNAS template when you apply final formatting.

Reference list format:

1. A. B. Smith, C. D. Jones, E. F. Williams, Title of article in sentence case. Proc. Natl. Acad. Sci. U.S.A. 120, 1234-1240 (2023).

Key formatting details:

• Author names: Initials first, then last name (e.g., "A. B. Smith")

• If there are more than five authors, list the first author's name followed by et al.

• Journal names use MEDLINE/PubMed abbreviations (or the full title for journals not indexed in MEDLINE)

• No issue numbers

• Page range followed by year in parentheses

• Provide DOI numbers if volume numbers are not available

PNAS self-citation note: When citing PNAS itself, use "Proc. Natl. Acad. Sci. U.S.A." as the abbreviation. Some reference managers default to "PNAS" which isn't the standard abbreviation for the reference list.

There's no formal reference cap, but Research Articles typically have 30-50 references. The page limit naturally constrains reference list length.

The SI Appendix is where PNAS authors put all the data that doesn't fit in the 6-page main article. PNAS publishes it online with the paper, as provided by the authors, without editing or typesetting.

SI Appendix structure:

1. SI Methods: Extended experimental procedures

1. SI Figures (Fig. S1, Fig. S2, etc.): Additional data and controls

1. SI Tables (Table S1, Table S2, etc.): Extended data tables

1. Datasets: Large datasets uploaded as separate files

1. Movies: Video files uploaded separately

SI formatting rules:

• The SI Appendix must be compiled into a single PDF for review

• It should have its own cover page with the article title (the PNAS SI template reads "Supporting Information for" followed by the title)

• Figures and tables are numbered with the "S" prefix (Fig. S1, Table S1)

• The main text must stand on its own without the SI

• For Brief Reports, SI is limited to extended methods, essential supporting datasets, and videos (no additional tables or figures)

Practical strategy: Given PNAS's tight page limit, the SI Appendix is essential. Most successful PNAS papers have a substantial SI that contains extended methods, additional experiments, and detailed statistical analyses. The main article tells the story. The SI proves it.

Dataset deposition: PNAS requires that all data underlying the paper be available in a public repository upon publication. Datasets must be deposited in an approved database before publication, with accession numbers provided for inclusion in the published article, and datasets must be cited in the references.

PNAS has specific requirements that many other journals don't:

Author contributions statement: Mandatory. Must specify what each author did, using designations such as designed research, performed research, contributed new reagents or analytic tools, analyzed data, and wrote the paper. PNAS takes the published contributions from the submission system, not from the manuscript file, and its Word template also has an Author Contributions line on the title page, so keep the two consistent. Example: "Author contributions: A.B.S. designed research; C.D.J. performed research; E.F.W. analyzed data; and A.B.S. wrote the paper."

Article classification: At submission, you must select a PNAS classification for your article:

• Physical Sciences (with subcategories like Applied Mathematics, Chemistry, Physics)

• Biological Sciences (with subcategories like Biochemistry, Cell Biology, Neuroscience)

• Social Sciences (with subcategories like Economics, Psychology, Political Sciences)

Select both a major and a minor classification category; dual classifications between major categories are permitted.

Article type designation: Research Articles can be designated as either "Direct Submission" or "Contributed." Contributed articles are submitted by NAS members and follow a different review process. Most authors submit through the Direct Submission track.

ORCID is required for the corresponding author at submission. Do not put ORCIDs in the manuscript file; authors link their ORCID account to their PNAS profile at pnascentral.org.

Title length. PNAS asks for titles under 135 characters that are descriptive and comprehensible to a broad scientific audience, and advises avoiding numbers, acronyms, abbreviations, punctuation, and puns.

Introduction heading. PNAS's recommended manuscript order and its Word template list an Introduction first in the main text, followed by Results, Discussion, and Materials and methods. The template also says not all manuscripts need to follow the standard section order or headings.

Results before Discussion. PNAS's recommended order is Introduction, Results, Discussion, then Materials and methods, acknowledgments and funding sources, references, and figure legends. The Word template says Materials and Methods should appear after the Results and Discussion in most cases.

Affiliations and footnotes. PNAS asks authors to match authors with institutions using superscripts, and to mark in-text footnotes with the symbols *, †, ‡, §, ¶ in that order.

Abbreviations. PNAS asks authors to keep abbreviations accessible to a broad scientific audience and to define abbreviations specific to a particular field at first mention in the text.

Dual classification. Dual classifications are permitted between major categories; within a major category they are allowed only in exceptional cases with Editorial Board approval (PNAS's Word template says they cannot be within the same major classification).

Competing interest statement. Mandatory. Disclosures must be entered directly into the submission system; a link to disclosures hosted on a website is not permissible.

1. Significance Statement is separate from the abstract. Don't combine them. They serve different purposes and appear in different locations on the published page.

1. Plan for the whole article, not just the body text. PNAS sizes a standard 6-page article at about 4,000 words, 50 references, and 4 figures or tables, so references and figures use up the page budget. The SI Appendix is separate.

1. The first submission does not need journal formatting. PNAS's format-neutral policy means the initial manuscript does not have to follow strict journal formatting. Revised submissions are encouraged to follow the formatting guidelines, so apply the template then.

1. In-text footnotes. PNAS asks for in-text footnotes to be marked with symbols (*, †, ‡, §, ¶) in that order.

1. Figure legends. PNAS's documents differ here: the recommended manuscript order lists figure legends after the references, the figure-legend guidance says to include them immediately after the figure is referenced, and the Word template places each legend below its figure on a separate page. Follow the current template when you apply final formatting.

1. Ethics statements. Human and animal research approvals must be identified in the Methods section, with reference or permit numbers where available.

For PNAS-targeted manuscripts, three patterns consistently predict formatting desk-screen failure at Proceedings of the National Academy of Sciences (PNAS). The patterns below are the same ones the journal's handling editors and outside reviewers flag at first-pass triage.

Scope-fit ambiguity in the abstract. PNAS editors move fastest on manuscripts whose contribution is obviously aligned with broad-significance contribution communicable to a multidisciplinary readership. The named failure pattern: Direct Submissions with abstracts that read to the subfield rather than to a multidisciplinary audience get desk-screen rejection within 5-7 days. Check whether your abstract reads to PNAS's scope

Methods package incomplete for the journal's reviewer pool. PNAS reviewers expect specific methodological detail. Papers whose contribution requires specialist translation in the discussion section extend revision rounds. Check if your methods package is reviewer-complete

Reference-list and clean-citation failure mode. PNAS says references must not cite retracted articles except when referring to the retraction. Check whether your reference list is clean against Crossref + Retraction Watch

Manusights submission-corpus signal for Proceedings of the National Academy of Sciences (PNAS). Of the manuscripts our team screened before submission to PNAS and peer venues in 2025, the editorial-culture mismatch most consistent across the cohort is pnas direct submissions face stricter scope-fit screening than nas-member-track contributions. In our analysis of anonymized PNAS-targeted submissions,

For manuscripts targeting PNAS, four patterns generate the most consistent desk-rejection outcomes.

Significance across disciplines not established in the Introduction. PNAS says Research Reports "describe the results of original research of exceptional importance." Editors evaluate whether the Introduction frames the work in terms that a scientist in a different field can understand and appreciate, not just specialists. Manuscripts where the Introduction situates the problem entirely within the author's specialty, without explaining why the finding matters to the broader scientific community, are declined at the desk-review stage.

PNAS letter of submission not tailored to the "exceptional importance" standard. Authors submitting directly (without a member sponsor) should use the cover letter to argue explicitly why the work meets the PNAS standard of exceptional importance. Generic cover letters that describe what the study did without arguing why it is exceptionally important to science broadly are a missed opportunity. Editors use the cover letter to assess whether the authors understand the journal's significance threshold before reading the manuscript.

Significance statement exceeds 120 words or is written in specialist language. PNAS requires a Significance Statement of 120 words or fewer, written in language accessible to a general scientific audience. This statement is used by editors and non-specialist reviewers to evaluate broad significance. Statements that exceed 120 words, use technical jargon without definition, or simply summarize the abstract rather than explaining why the work matters to science broadly are returned for revision. PNAS asks for the significance to be explained at a level understandable to an undergraduate-educated scientist outside their field of specialty.

Direct submission (non-sponsored) without confirming editor availability. Authors submitting directly (without a member sponsor) should suggest appropriate Editorial Board members and NAS members (PNAS asks for at least three of each) and check that they handle the relevant area. A common issue is suggesting a PNAS editor based on name recognition rather than checking their actual handling area. Manuscripts assigned to editors who do not cover the relevant subject area require reassignment, which adds delay.

A PNAS formatting and readiness check evaluates manuscript structure, significance framing, and Significance Statement compliance against these desk-rejection patterns before you submit.

Or see example reports before you finalize.