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*Institution: UNIVERSITY OF PITTSBURGH* Sign In as Member / Individual
</cgi/login?uri=%2Fmisc%2Fiforc.shtml>

	*Information for Authors*

/Revised January 2008/
PDF of Information for Authors <http://www.pnas.org/misc/iforc.pdf>

------------------------------------------------------------------------
	
down <#purpose> 	 *PURPOSE AND SCOPE <#purpose>*

down <#editorial>	 *EDITORIAL POLICIES <#editorial>*

    * PNAS Submission Guidelines <#submission>
    * Journal Policies <#policies>

	
*Forms and Details for Submission*

	
down <#procedures> 	 *PROCEDURES FOR SUBMITTING MANUSCRIPTS <#procedures>*

	
	

    * Contact Information <#procedures>
    * Publication Charges <#charges>
    * Manuscript Preparation <#prep>
    * Language-Editing Services <#les>
    * Submitting Manuscripts <#online>
    * Digital Figures <#digital>
    * Tables <#tables>

	

    * Supporting Information <#si>
    * Use of URLs in Text <#url>
    * Journal Cover Figures <#cover>
    * Manuscript Length <#length>
    * Manuscript Format <#format>
    * Abbreviations and Symbols <#abbreviations>

------------------------------------------------------------------------
<#top> 	

*PURPOSE AND SCOPE*

The /Proceedings of the National Academy of Sciences USA/ (PNAS)
publishes research reports, commentaries, perspectives, and colloquium
papers. In accordance with the guiding principles established by George
Ellery Hale in 1914, PNAS publishes brief first announcements of Academy
members' and foreign associates' (hereafter referred to as members) more
important contributions to research and of work that appears to a member
to be of particular importance. PNAS is a general science journal with a
broad scientific audience. All papers should be intelligible to this
audience.

	* Research Reports* <http://www.pnas.org/search.dtl> describe the
results of original research of exceptional importance.  

* Feature Articles*
<http://www.pnas.org/cgi/collection/feature_articles?ck=nck> are
in-depth research reports with exceptional breadth and are written at
the invitation of the Editorial Board.
 
*Commentaries* <http://www.pnas.org/commentary.shtml> call attention to
papers of particular note and are written at the invitation of the
Editorial Board.
 
*Perspectives* <http://www.pnas.org/perspective.shtml> present a
viewpoint on an important area of research and are written at the
invitation of the Editorial Board. Perspectives focus on a specific
field or subfield within a larger discipline and discuss current
advances and future directions. Perspectives are of broad interest for
nonspecialists and may add personal insight to a field.
 
*Colloquium Papers* <http://www.pnas.org/misc/colloquia.shtml> are
reports of scientific colloquia held under Academy auspices.

*Letters * <http://www.pnas.org/cgi/reprint/0709174104v1>are brief
online-only comments that contribute to the discussion of a PNAS
research article published within the last 3 months. Letters may not
include requests to cite the letter writer?s work, accusations of
misconduct, or personal comments to an author. Letters are limited to
250 words and no more than five references.

------------------------------------------------------------------------
<#top> 	*EDITORIAL POLICIES*
PNAS Submission Guidelines <#submission> | Journal Policies <#policies>


<#editorial> 	*PNAS Submission Guidelines*

The standard mode of transmitting manuscripts is for authors to submit
them directly to PNAS. Authors must recommend three appropriate
Editorial Board members, three NAS members who are expert in the paper?s
scientific area, and five qualified referees. The Board may choose
someone who is or is not on that list or may reject the paper without
further review. A directory of PNAS member editors and their research
interests is available at http://nrc88.nas.edu/pnas%5Fsearch. The editor
may obtain reviews of the paper from at least two qualified referees,
each from a different institution and not from the authors?
institutions. For direct submission papers, the PNAS Office will invite
the referees, secure the reviews, and forward them to the editor for a
decision. The PNAS Office will also secure any revisions and subsequent
reviews. The name of the editor, who may remain anonymous to the author
until the paper is accepted, will be published in PNAS as editor of the
article. Papers submitted directly are published as ??Edited by?? the
responsible editor and have an additional identifying footnote.

Academy members who have told authors they are willing to oversee the
review process have 48 hours from the time of submission to alert the
PNAS Office to their request. During this period the PNAS Office will
contact the member to confirm. Authors should coordinate submission to
ensure the member is available. The Board cannot guarantee that the
member will be assigned the manuscript or that it will be sent for review.

An Academy member may ??communicate?? for others up to two manuscripts
per year that are within the member?s area of expertise. Before
submission to PNAS, the member obtains reviews of the paper from at
least two qualified referees, each from a different institution and not
from the authors? or member's institutions. Referees should be asked to
evaluate revised manuscripts to ensure that their concerns have been
adequately addressed. The names and contact information, including
e-mails, of referees who reviewed the paper, along with the reviews and
the authors? response, must be included. Reviews must be submitted on
the PNAS review form, and the identity of the referees must not be
revealed to the authors. The member must include a brief statement
endorsing publication in PNAS along with all of the referee reports
received. Members should follow National Science Foundation (NSF)
guidelines to avoid conflict of interest between referees and authors
(see Section /iii/). Members must verify that referees are free of
conflicts of interest, or must disclose any conflicts and explain their
choice of referees. These papers are published as ??Communicated by??
the responsible editor.

An Academy member may submit up to four of his or her own manuscripts
for publication per year. Members must secure the comments of at least
two qualified referees. Referees should be asked to evaluate revised
manuscripts to ensure that their concerns have been adequately
addressed. Members? submissions must be accompanied by the names and
contact information, including e-mails, of knowledgeable colleagues who
reviewed the paper, along with all of the reviews received, the authors?
response, and a brief statement endorsing publication in PNAS. Reviews
must be on the PNAS review form and should not be from the authors? own
institution. Members should follow NSF guidelines to avoid conflict of
interest between referees and authors (see Section /iii/). Members must
verify that referees are free of conflicts of interest, or must disclose
any conflicts and explain their choice of referees. The Academy member
must be a corresponding author on the paper. These papers are published
as ??Contributed by?? the responsible editor.

All manuscripts are evaluated by the Editorial Board. The Board may
reject manuscripts without further review or may subject manuscripts to
review and reject those that do not meet PNAS standards. Manuscripts
rejected by one member cannot be resubmitted through another member or
as a direct submission. When revisions are requested prior to final
decision, revised papers must be received within 2 months or they will
be treated as new submissions.

------------------------------------------------------------------------
<#editorial> 	

*Journal Policies*

/(i)/ Articles are considered provided they have not been *Published
Previously* or concurrently submitted for publication elsewhere. Related
manuscripts that are in press or submitted elsewhere must be included
with your PNAS submission.

Figures or tables that have been published elsewhere must be identified,
and permission of the copyright holder for /both/ the print and the
online editions of the journal must be provided (see
www.pnas.org/misc/permissions_letter.rtf
<http://www.pnas.org/misc/permissions_letter.rtf>).

/(ii)/ *Authorship* should be limited to those who have contributed
substantially to the work. The corresponding author must have obtained
permission from all authors for the submission of each version of the
paper and for any change in authorship.

All collaborators share some degree of responsibility for any paper they
coauthor. Some coauthors have responsibility for the entire paper as an
accurate, verifiable report of the research. These include coauthors who
are accountable for the integrity of the data reported in the paper,
carry out the analysis, write the manuscript, present major findings at
conferences, or provide scientific leadership to junior colleagues.
Coauthors who make specific, limited contributions to a paper are
responsible for their contributions but may have only limited
responsibility for other results. While not all coauthors may be
familiar with all aspects of the research presented in their paper, all
collaborators should have in place an appropriate process for reviewing
the accuracy of the reported results.

Authors must indicate their specific contributions to the published
work. This information will be published as a footnote to the paper.
Examples of designations include:

    * Designed research
    * Performed research
    * Contributed new reagents or analytic tools
    * Analyzed data
    * Wrote the paper

An author may list more than one contribution, and more than one author
may have contributed to the same aspect of the work.

/(iii)/ All authors, members, referees, and editors must disclose any
association that poses a *Conflict of Interest* in connection with the
manuscript. Authors must acknowledge all funding sources supporting the
work. Editors should follow NSF guidelines
<http://www.nsf.gov/attachments/108276/public/Conflict_of_Interest_Information.pdf>
to avoid conflict of interest between referees and authors
(www.nsf.gov/attachments/108276/public/Conflict_of_Interest_Information.pdf
<http://www.nsf.gov/attachments/108276/public/Conflict_of_Interest_Information.pdf>).
Recent collaborators, defined as people who have coauthored a paper with
the author or member within the past 48 months, should be excluded as
referees. Please see www.pnas.org/misc/coi.shtml
<http://www.pnas.org/misc/coi.shtml> for details.

/(iv)/ A completed form assigning *Copyright*
<http://www.pnas.org/misc/copyright.pdf> to the National Academy of
Sciences must be submitted to the PNAS office before the paper can be
published. This and other forms are available at www.pnas.org
<http://www.pnas.org>.

/(v)/ The Academy may distribute *Embargoed* copies of an accepted
article to the press prior to publication. Embargoes expire at 5:00 p.m.
Eastern time on the Monday before publication. Authors may talk freely
with the press about their work but should coordinate with the PNAS News
Office so that reporters are aware of PNAS policy. If you plan on
presenting your embargoed paper at a conference prior to publication,
please contact the PNAS News Office immediately at 202-334-1310 or
PNASnews@nas.edu <mailto:PNASnews@nas.edu>.

/(vi)/ Research involving *Human and Animal Subjects *must have been
approved by the author?s institutional review board. Authors must
include in the /Methods/ section a brief statement identifying the
institutional and/or licensing committee approving the experiments. For
experiments involving human subjects, authors must also include a
statement confirming that informed consent was obtained from all
subjects. All experiments involving human subjects must have been
conducted according to the principles expressed in the Declaration of
Helsinki <http://www.wma.net/e/policy/b3.htm>.

/(vii)/ For research using *Recombinant DNA*, physical and biological
containment must conform to National Institutes of Health
<http://www.nih.gov> guidelines or those of a corresponding agency.

/(viii)/ *Materials and Data Availability*. To allow others to replicate
and build on work published in PNAS, authors must make materials, data,
and associated protocols available to readers. Authors must disclose
upon submission of the manuscript any restrictions on the availability
of materials or information.

Authors must make *Unique Materials* (e.g., cloned DNAs; antibodies;
bacterial, animal, or plant cells; viruses; and computer programs)
promptly available on request by qualified researchers for their own
use. Failure to comply will preclude future publication in the journal.
It is reasonable for authors to charge a modest amount to cover the cost
of preparing and shipping the requested material. Contact pnas@nas.edu
<mailto:pnas@nas.edu> if you have difficulty obtaining materials.

*Plasmids:* Authors are encouraged to deposit plasmid constructs in a
public repository such as Addgene (www.addgene.org)
<http://www.addgene.org/pgvec1>.

*Databases:* Before publication, authors must deposit large data sets
(including microarray data, protein or nucleic acid sequences, and
atomic coordinates for macromolecular structures) in an approved
database and provide an accession number for inclusion in the published
paper. When no public repository exists, authors must provide the data
as Supporting Information online or, in special circumstances when this
is not possible, on the author?s institutional web site, provided that a
copy of the data is provided to PNAS.

*/Characterization of Chemical Compounds:/ *Authors must provide
sufficient information to establish the identity of a new compound and
its purity. Sufficient experimental details must be included to allow
other researchers to reproduce the synthesis. Characterization data and
experimental details must be included either in the text or the
Supporting Information.

/*Protein and Nucleic Acid Sequences:*/ Authors must deposit data in a
publicly available database such GenBank/EMBL/DNA Data Bank of Japan
<http://www.ncbi.nlm.nih.gov/Genbank> or Swiss-Prot
<http://www.expasy.org/sprot/>.

/*Structural Studies:*/ Authors of papers describing new structure
determinations must submit to the Protein Data Bank
<http://www.rcsb.org/pdb/> at the Research Collaboratory for Structural
Bioinformatics <http://www.rcsb.org> or its equivalent all structural
data required to validate the discussion, including x-ray amplitudes,
structure factor files, and the derived atomic coordinates. For nuclear
magnetic resonance structures, data deposited should include resonance
assignments and all restraints used in structure determination and the
derived atomic coordinates for both an individual structure and a family
of acceptable structures. Articles must include literature references
for all coordinate data sets as well as data set identification. Authors
must agree to release the coordinates when the article is published.

*/Functional Magnetic Resonance Imaging (fMRI) Studies:/* Authors should
deposit data with the fMRI Data Center <http://www.fmridc.org/> or other
suitable public repositories.	

*/Genomic and Proteomic Studies:/* Authors of papers that include
genomic, proteomic, or other high-throughput data are required to submit
their data to the NCBI gene expression and hybridization array data
repository (GEO, www.ncbi.nlm.nih.gov/geo
<http://www.ncbi.nlm.nih.gov/geo>) or equivalent publicly accessible
database and must provide the accession number. Access to the
information in the database must be available at the time of
publication. Submitted data should follow the MIAME checklist (for more
information, see www.mged.org/Workgroups/MIAME/miame_checklist.html
<http://www.mged.org/Workgroups/MIAME/miame_checklist.html>).

/(ix)/ *Figure Preparation:* No specific feature within an image may be
enhanced, obscured, moved, removed, or introduced. The grouping or
consolidation of images from multiple sources must be made explicit by
the arrangement of the figure and in the figure legend. Adjustments of
brightness, contrast, or color balance are acceptable if they are
applied to the whole image and if they do not obscure, eliminate, or
misrepresent any information present in the original, including
backgrounds. Questions about images raised during image screening will
be referred to the editors, who may request the original data from the
authors for comparison with the prepared figures. If the original data
cannot be produced, the manuscript may be rejected. Cases of deliberate
misrepresentation of data will result in rejection of the paper and will
be reported to the corresponding author's home institution or funding
agency.

/(x)/ *Supporting Information:* Supporting Information enhances papers
in PNAS by providing additional substantive material, but the print
version of the paper must stand on its own merits. Supporting
Information is reviewed along with the paper and must be approved by the
editors and referees. Instead of appearing in the printed version of the
journal, Supporting Information is posted on the PNAS web site
<http://www.pnas.org/> at the time of publication. Supporting
Information is referred to in the text and cannot be altered by authors
after acceptance.

Supporting Information may take the form of supplemental figures,
tables, datasets, derivations, and videos. Authors should express their
interest in their cover letter to include Supporting Information with
their paper. In addition, editors may suggest that part of the submitted
data could be more suitably presented online only to save journal space
and to focus the article.

/(xi)/ *PNAS Early Edition:* PNAS articles are published daily online
before print at www.pnas.org in PNAS Early Edition
<http://www.pnas.org/papbyrecent.shtml>. Papers may be published online
1 to 4 weeks before they appear in print. Authors who return proofs
quickly and keep changes to a minimum get maximum publication speed. A
paper in Early Edition is the publication of record. The official
publication date is posted with the article online.

/(xii)/ *Errata:* PNAS publishes corrections for errors, made by the
journal or authors, of a scientific nature that do not alter the overall
basic results or conclusions of a published article. PNAS publishes
retractions for major errors that may call into question the source of
the data or the validity of the results and conclusions of an article.
Errata are published at the discretion of the editors and appear as
formal printed and online notices in the journal.

------------------------------------------------------------------------
<#top> 	

*PROCEDURES FOR SUBMITTING MANUSCRIPTS*

*Contact Information*

PNAS, 500 Fifth Street, NW, NAS 340, Washington, DC 20001 USA. Phone
1-202-334-2679, fax 1-202-334-2739, e-mail pnas@nas.edu
<mailto:pnas@nas.edu>.

Courier or express mail: PNAS, 2101 Constitution Avenue, NW, NAS 340,
Washington, DC 20418 USA.

------------------------------------------------------------------------
<#top> 	

*Publication Charges*

*/Page charges/*
PNAS depends, in part, on the payment of page charges for its operation.
Payment of the page charge of $70 per printed page will be assessed from
all authors who have funds available for that purpose. Authors will be
charged for extensive alterations on proofs. Payment of $250 per article
will be assessed for Supporting Information. Authors of research
articles may pay a surcharge of $1,200 to make their paper freely
available through the PNAS open access option. If your institution has a
Site License, the open access surcharge is $850. All articles are free
online after 6 months. Articles are accepted or rejected for publication
and published solely on the basis of merit.

	*/Color charges/*
Payment by authors of the following additional costs is expected: $325
for each color figure or table; $150 for each replacement or deletion of
a color figure or table. A single figure is defined as original art that
can be processed as a unit and printed on one page without intervening
type. Requests for waiver of charges should be submitted to pnas@nas.edu
<mailto:pnas@nas.edu>.
------------------------------------------------------------------------
  	

* MANUSCRIPT PREPARATION*

<#top> 	*Language-Editing Services *

Prior to submission, authors who believe their manuscripts would benefit
from professional editing are encouraged to use a language-editing
service (see list at www.pnas.org/misc/language-editing.shtml
<http://www.pnas.org/misc/language-editing.shtml>). PNAS does not take
responsibility for or endorse these services, and their use has no
bearing on acceptance of a manuscript for publication.


<#top> 	*Submitting Manuscripts*

Authors submitting via direct manuscript submission may submit Adobe
Acrobat PDFs of their papers at www.PNAScentral.org
<http://www.pnascentral.org/>. Source files are required for all other
submissions, including revisions. Members communicating or contributing
papers should also submit via the web. If you are unable to submit
online, please contact the PNAS Office. Corresponding authors of
communicated and contributed papers will be provided a URL for file
submission after the member has initiated the process by providing his
or her endorsement and copies of the reviews received. Supporting
Information may also be submitted online.


<#top> 	*Digital Figures*

Only TIFF, EPS, and high-resolution PDF for Macintosh or PC are allowed
for figures that will appear in the print journal. (See /Supporting
Information <#si>/ below for online-only material.) Color images must be
in RGB (red, green, blue) mode. Include the font files for any text. PC
or Macintosh versions of Adobe PostScript fonts
<http://cjs.cadmus.com/da/guidelines.asp#fonts> must be used (no system
"bitmap" fonts). Images must be final size, preferably 1 column width
(8.7 cm). Figures wider than 1 column should be between 10.5 and 18.0 cm
wide. Numbers, letters, and symbols should be no smaller than 6 points
(2 mm) and no larger than 12 points (6 mm) after reduction and must be
consistent. Composite figures must be preassembled. Figures must be
submitted as separate files, not embedded in manuscript text. See
www.pnas.org/misc/digitalart.pdf
<http://www.pnas.org/misc/digitalart.pdf> or contact
pnasdigart@cadmus.com <mailto:pnasdigart@cadmus.com>.


<#top> 	

*Tables*

Each table should have a brief title, be on a separate page, and be
double-spaced.


<#top> 	*Supporting Information*

The print version of the paper must stand on its own without the
Supporting Information. Refer to Supporting Information in the
manuscript at an appropriate point in the text. Number supporting
figures and tables to follow all figures and tables in the main text.

Authors who place detailed materials and methods in Supporting
Information must provide sufficient detail in the print edition methods
to enable a reader to follow the logic of the procedures and results and
also must reference the online methods. If a paper is fundamentally a
study of a new method or technique, then the methods must be described
completely in the print edition.

Use the following file formats
<http://cjs.cadmus.com/da/applications.asp> for Supporting Information
only:

    * *Text:* Use Word, WordPerfect, or RTF files (PDFs are acceptable
      for LaTeX files).
    * *Figures:* Provide a brief legend for each figure in a Word,
      WordPerfect, or RTF file. Provide figure images in JPEG, GIF, or
      PDF files; do not save figure numbers, legends, or author names as
      part of the image.  File sizes should not exceed 5 MB. Images
      should not exceed 500 pixels per inch in width or height.
    * *Tables:* Supply Word, Excel, HTML, or PDF files (one table per
      file). Include the table title and legend in the table file. Do
      not use tabs or spaces to separate columns in Word or WordPerfect
      tables.
    * *Movies:* Supply QuickTime-formatted files (with a .mov file name
      extension) or MPEG files, and submit a brief legend for each movie
      in a Word, WordPerfect, or RTF file. All movies should be
      submitted at the desired reproduction size and length. To avoid
      excessive delays in downloading the files, movies should be no
      more than 10 MB in size. 


<#top> 	*Use of URLs in Text*

As a publisher, PNAS must be able to archive the data essential to a
published article. Where such archiving is not possible, deposition of
data in public databases, such as GenBank, ArrayExpress, Protein Data
Bank, Unidata, and others outlined in the Information for Authors, is
acceptable.

Only links to web sites that are permanent public repositories, such as
self-perpetuating online resources funded by government, academia, and
industry, are permitted. Links to an author?s personal web page are not
acceptable. The PNAS copyright policy allows authors to post their PNAS
paper on their home page after the paper is published in PNAS.


<#top> 	*Journal Cover Figures*

Authors are invited to submit scientifically interesting and visually
arresting cover images. To view examples of cover art, please visit the
PNAS cover archive at www.pnas.org/coverarchive
<http://www.pnas.org/coverarchive>. Illustrations need not be reprinted
in the article but should be representative of the work. Images should
be original, and copyright will transfer to PNAS. Include a brief
lay-language caption (50-60 words) and credit information (e.g.,
Photograph courtesy of...). Images should be 21.5 cm wide by 22.5 cm
high. Files should be EPS or TIFF and should be in CMYK (cyan, magenta,
yellow, black) color mode. Cover figure files may be submitted online
when the paper is submitted or may be sent by e-mail to
PNAScovers@nas.edu <mailto:PNAScovers@nas.edu>. Send large files on
CD-ROM by courier to the PNAS Office or contact PNAS for FTP
instructions. Submissions provided outside the online submission system
should include manuscript number, author name, phone, and e-mail.
Illustrations will not be returned unless requested.

<#top> 	*Manuscript Length*

PNAS generally uses a two-column format averaging 67 characters,
including spaces, per line. All manuscripts submitted for 2008
publication and beyond must include the full title for each cited
article. The character count limit will increase from 47,000 to 49,000,
and the page formatting will be modified slightly to accommodate this
change. The maximum length of a research article remains six printed
pages, including all text, spaces, and the number of characters
displaced by figures, tables, and equations. The total number of
characters equals:

    * The number of characters /including / spaces in the text (include
      all parts except tables), *plus*
    * The height in cm of each figure at desired printed size x 180 for
      a one-column figure or x 360 for a two-column figure, *plus*
    * The height in number of lines of each table x 60 for a one-column
      table or x 120 for a two-column table, *plus*
    * A 120-character allowance for the space above and below each
      single column of a figure, table, or equation, *plus*
    * An additional 60 characters for each one-column line of equation.
    * A table that has lines with more than 60 characters plus spaces or
      a figure that is wider than 8.7 cm takes up /two/ columns in width.

If the word processing program character count /excludes/ spaces, add
the word count to the character count to obtain a character count that
includes spaces.

Authors will be responsible for additional charges incurred due to
shortening overlong papers in proof.

------------------------------------------------------------------------
<#top> 	*Manuscript Format*
Manuscript Order <#order> | Nomenclature and Style <#nomenclature> |
Abbreviations and Symbols <#abbreviations>


<#format> 	

*Manuscript Order*

The standard order of sections in the manuscript file is: title page,
abstract, introduction, results, discussion, materials and methods,
acknowledgments, references, figure legends, and tables. Number all
pages starting with the title page as page 1.

*Title Page.* Include the following information on this page:

    * *Classification:* Select a major (Physical, Social, or Biological
      Sciences) and a minor category from the following. Dual
      classifications are permitted /between/ major categories and in
      exceptional cases, subject to Editorial Board approval, /within/ a
      major category.

          o PHYSICAL SCIENCES: Applied Mathematics, Applied Physical
            Sciences, Astronomy, Chemistry, Computer Sciences,
            Engineering, Environmental Sciences, Geology, Geophysics,
            Mathematics, Physics, Statistics, and Sustainability Science.

          o SOCIAL SCIENCES: Anthropology, Economic Sciences,
            Environmental Sciences, Political Sciences, Psychology,
            Social Sciences, and Sustainability Science.

          o BIOLOGICAL SCIENCES: Agricultural Sciences, Anthropology,
            Applied Biological Sciences, Biochemistry, Biophysics, Cell
            Biology, Developmental Biology, Ecology, Environmental
            Sciences, Evolution, Genetics, Immunology, Medical Sciences,
            Microbiology, Neuroscience, Pharmacology, Physiology, Plant
            Biology, Population Biology, Psychology, and Sustainability
            Science.

    * *Title: *Titles should be no more than three typeset lines
      (generally 135 characters including spaces) and should be
      comprehensible for a broad scientific audience.
    * *Author affiliation:* Include department, institution, and
      complete address, with the ZIP/postal code, for each author. If
      there are authors with different affiliations, use superscripts to
      match authors with institutions.
    * *Corresponding author:* The name, complete address, telephone and
      fax numbers, and e-mail address of the author to whom
      correspondence and proofs should be sent. Mailing and e-mail
      addresses will appear in print and online.
    * *Manuscript information:* The number of text pages (including
      references and figure legends), of figures, and of tables.
    * *Abbreviations:* Define nonstandard abbreviations where first
      mentioned in text.
    * *Data deposition footnote:* Supply all database accession numbers
      and/or codes.

*Abstract*/./ Provide an abstract of no more than 250 words on page 2 of
the manuscript. Abstracts should explain to the general reader the major
contributions of the article. References in the abstract must be cited
in full within the abstract itself.
 
*Text*/./ Describe procedures in sufficient detail so that the work can
be repeated. Methods must be presented after Results and Discussion.
Follow the spelling and usage given in /Webster's Third New
International Dictionary/ or the /Random House Dictionary of the English
Language/. Avoid laboratory jargon. Correct chemical names should be
given, and strains of organisms should be specified. Trade names should
be identified by an initial capital letter with the remainder of the
name lowercase. Names of suppliers of uncommon reagents or instruments
should be provided. Use Système International (SI) units and symbols
whenever possible.
 
*Footnotes*/./ Use symbols in the order *, dagger , Dagger , §, ¶,
par-bars , **, dagger dagger , Dagger Dagger , §§, ¶¶.
 
*Acknowledgments*/./ List acknowledgments and funding sources.
 
*References*/./ References must be in PNAS style. Only published or
in-press papers and books may be cited in the reference list.
Unpublished abstracts of papers presented at meetings are not permitted.
References should be cited in numerical order as they appear in text.
Because tables and figures will be inserted in the text where first
cited, references in these sections should be numbered accordingly.
*Manuscripts must include the full title for each cited article. *
Authors must translate foreign language titles into English, with a
notation of the original language. All authors (unless there are more
than five) should be named in the citation. If there are more than five,
list the first author's name followed by /et al/. Provide inclusive page
ranges for journal articles and book chapters. Databases are cited in
the text or as footnotes.

The corresponding author must be prepared to provide a signed
authorization for the citation of unpublished data and personal
communications.
 
Journal articles are cited as follows:
 
10.  Neuhaus J-M, Sitcher L, Meins F, Jr, Boller T (1991) A short
C-terminal
       sequence is necessary and sufficient for the targeting of chitinases
       to the plant vacuole. /Proc Natl Acad Sci USA/ 88:10362-10366.
 
For correct abbreviations of journal titles, refer to /Chemical
Abstracts Service Source Index/ (CASSI).
 
Articles or chapters in books are cited as follows:
 
14.   Hill AVS (1991) in /Molecular Evolution of the Major
Histocompatibility
       Complex/, eds Klein J, Klein D (Springer, Heidelberg), pp 403-420.
 
*Figure Legends*/./ Provide these separately from figures. For figures
with multiple panels, the first sentence of the legend should be a brief
overview of the entire figure.


<#format> 	*Nomenclature and Style*

International standards on nomenclature should be used. For recommended
abbreviations and symbols, see
www.pnas.org/misc/iforc.shtml#abbreviations
<http://www.pnas.org/misc/iforc.shtml#abbreviations>.


<#format> 	*Abbreviations and Symbols*

Table 1. Standard Abbreviations and Symbols
<http://www.pnas.org/misc/table1.pdf>
Table 2. Abbreviations for units of measurement and physical and
chemical quantities <http://www.pnas.org/misc/Table2.pdf>

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