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Frequently Asked Questions about PNAS Plus and Significance Statements

1. What is a Significance Statement?

The Significance Statement is distinct in purpose from the abstract. The goal of the Significance Statement is to allow readers from many fields of science to understand why a paper is important. The statement should be no longer than 120 words and written at a level understandable to an undergraduate-educated scientist outside their field of specialty. The statement should provide enough context for the paper’s implications to be clear to readers. The statement should not contain references and should avoid numbers, measurements, and acronyms unless necessary. It will be considered for appropriateness by the paper’s reviewers as part of the editorial process. The Significance Statement will appear in the paper itself. For PNAS Plus papers only, a collection of such statements will appear in the print issue of the journal. Please see the editorial at: http://www.danielhellerman.com/cgi/doi/10.1073/pnas.1212313109. Below are sample Significance Statements as a guide:

Cobalt-dithiolene complexes for the photocatalytic and electrocatalytic reduction of protons in aqueous solutions

William R. McNamara, Zhiji Han, Chih-Juo (Madeline) Yin, William W. Brennessel, Patrick L. Holland, and Richard Eisenberg [Abstract]

Conversion of solar energy into chemically stored energy via artificial photosynthesis (AP) represents a promising approach to providing renewable energy. Systems for AP are generally designed to split water photochemically, reducing aqueous protons to hydrogen fuel and oxidizing water to oxygen. Focusing separately on the reductive and oxidative sides of water splitting facilitates this goal, and a current focus is to have both photosensitizer and catalyst components made only of earth-abundant elements. In this paper, cobalt-dithiolene complexes are found to be active for the catalytic reduction of protons in aqueous organic media, both photochemically with visible light and electrochemically. These promising new catalysts contain redox active ligands, enabling the two-electron reduction of protons to hydrogen.

Domain–domain interactions in full-length p53 and a specific DNA complex probed by methyl NMR spectroscopy

Michal Bista, Stefan M. Freund, and Alan R. Fersht [Abstract]
The structures of many complex proteins cannot be directly solved at high resolution because they do not crystallize and are too large for complete NMR studies. One solution is to solve the structures of the isolated smaller folded constituents at high resolution and arrange them into the overall structure determined at low resolution using electron microscopy. But there is room for error in fitting the components. This study shows how a specialized NMR method can determine the interfaces that interact between components and aid in the overall fitting. We use the study to resolve two conflicting structural models of the tumor suppressor p53, one of which was proposed from electron microscopy, and the other from a combination of methods, in favor of the latter.

S-nitrosylation of AMPA receptor GluA1 regulates phosphorylation, single channel conductance, and endocytosis

Balakrishnan Selvakumar, Meagan A. Jenkins, Natasha K. Hussain, Richard L. Huganir, Stephen F. Traynelis, and Solomon H. Snyder [Abstract]
Synaptic signaling by glutamate, the principal neurotransmitter of the brain, is mediated by two principal receptor subtypes designated NMDA and AMPA. NMDA transmission is thought to modulate AMPA receptors to convey the plasticity underlying learning and memory. AMPA receptors are phosphorylated at a specific serine, which enhances receptor function. We demonstrate that nitric oxide, generated in response to NMDA signaling “nitrosylates” AMPA receptors, augmenting their function. Modulation of cross-talk between the two receptors by nitric oxide implies that drugs impacting nitric oxide may beneficially influence synaptic plasticity.

Signatures of founder effects, admixture, and selection in the Ashkenazi Jewish population

Steven M. Bray, Jennifer G. Mulle, Anne F. Dodd, Ann E. Pulver, Stephen Wooding, and Stephen T. Warren [Abstract]
Ashkenazi Jews (AJ) are known to have originated from the Middle East, migrating into Europe by the 10th century. AJ have long been considered a genetic isolate, based upon cultural practices and demographic history. Prior studies have reflected a genomic architecture consistent with this view. However, these studies have limited data, often examining only a few markers. Using a genome-wide approach, we surveyed 732,000 variants in 471 unrelated AJ individuals. While we find genomic characteristics consistent with a genetic isolate, we also find greater genetic diversity and European admixture than previous studies. Thus, the AJ genome likely arose from a distinct Middle Eastern population migrating into and mating with Europeans that has been further influenced by genetic drift or randomness following population bottlenecks.

Starch grain and phytolith evidence for early ninth millennium B.P. maize from the Central Balsas River Valley, Mexico

Dolores R. Piperno, Anthony J. Ranere, Irene Holst, Jose Iriarte, and Ruth Dickau [Abstract]
The cultural achievements of peoples who lived in the lowland Neotropical forest before European arrival were long underappreciated, partly because humid tropical environments are inimical to the preservation of organic plant fossils traditionally used to document the origins of agriculture. Arguments about the domestication of maize are a case in point, as excellent preservation in the semiarid highlands of Mexico once pointed to maize’s origins there. In this paper, plant microfossils (phytoliths and starch grains) from stone tools used to process plants provide evidence for the initial domestication of maize by 9,000 years ago in tropical lowland Mexico. The evidence further supports early and independent emergences of agriculture in the Neotropical forest based on plants still consumed worldwide.

Classic Period collapse of the Central Maya Lowlands: Insights about human–environment relationships for sustainability

B. L. Turner II and Jeremy A. Sabloff [Abstract]
The collapse of Classic Period Lowland Maya about CE 950 and the long-term abandonment of much of the interior of the Maya realm have long been controversial. With the emergence of new paleoenvironmental evidence, the role of climate change in the collapse and abandonment has been reintroduced. Provisioning a large and densely populated interior realm required the construction and maintenance over millennia of a capital- and labor-intensive, infrastructure-rich landscape, generating environmental stressors. These conditions were amplified in the 10th century by extreme aridity and a shift in the flow of trade that circumvented the interior lowlands, rendering infrastructure maintenance difficult. The collapse and abandonment were the products of interactive societal and environmental factors best understood in terms of complex system behavior.

2. Is PNAS Plus a separate journal?

No, PNAS Plus is a type of research article. These research reports appear in an expanded online format up to 10 pages in length and may include supporting information (SI).

3. Are PNAS Plus articles peer-reviewed?

Yes, these articles—the full article and the Significance Statement—follow the same review process as either Contributed or Direct Submissions.

4. Who can submit PNAS Plus articles?

All authors.

5. If my paper is overlong, can I switch to PNAS Plus?

No, authors must choose at initial submission whether to submit in the PNAS Plus format. Manuscripts rejected as one submission type cannot be resubmitted as another.

6. How much does it cost to publish a PNAS Plus article?

The current costs for PNAS Plus articles are listed on our Information for Authors.


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