The design and synthesis of protein-like polymers is a fundamental challenge in materials science. A biomimetic approach is to explore the impact of monomer sequence on non-natural polymer structure and function. We present the aqueous self-assembly of two peptoid polymers into extremely thin two-dimensional (2D) crystalline sheets directed by periodic amphiphilicity, electrostatic recognition and aromatic interactions. Peptoids are sequence-specific, oligo-N-substituted glycine polymers designed to mimic the structure and functionality of proteins. Mixing a 1:1 ratio of two oppositely charged peptoid 36mers of a specific sequence in aqueous solution results in the formation of giant, free-floating sheets with only 2.7 nm thickness. Direct visualization of aligned individual peptoid chains in the sheet structure was achieved using aberration-corrected transmission electron microscopy. Specific binding of a protein to ligand-functionalized sheets was also demonstrated. The synthetic flexibility and biocompatibility of peptoids provide a flexible and robust platform for integrating functionality into defined 2D nanostructures.

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Two-dimensional nanomaterials play a critical role in biology (e.g., lipid bilayers) and electronics (e.g., graphene) but are difficult to directly synthesize with a high level of precision. Peptoid nanosheet bilayers are a versatile synthetic platform for constructing multifunctional, precisely ordered two-dimensional nanostructures. Here we show that nanosheet formation occurs through an unusual monolayer intermediate at the air-water interface. Lateral compression of a self-assembled peptoid monolayer beyond a critical collapse pressure results in the irreversible production of nanosheets. An unusual thermodynamic cycle is employed on a preparative scale, where mechanical energy is used to buckle an intermediate monolayer into a more stable nanosheet. Detailed physical studies of the monolayer-compression mechanism revealed a simple preparative technique to produce nanosheets in 95% overall yield by cyclical monolayer compressions in a rotating closed vial. Compression of monolayers into stable, free-floating products may be a general and preparative approach to access 2D nanomaterials.

BackgroundThe emergence of dengue throughout the tropical world is affecting an increasing proportion of adult cases. The clinical features of dengue in different age groups have not been well examined, especially in the context of early clinical diagnosis.Methodology/Principal FindingsWe structured a prospective study of adults (≥18 years of age) presenting with acute febrile illness within 72 hours from illness onset upon informed consent. Patients were followed up over a 3–4 week period to determine the clinical outcome. A total of 2,129 adults were enrolled in the study, of which 250 (11.7%) had dengue. Differences in the rates of dengue-associated symptoms resulted in high sensitivities when the WHO 1997 or 2009 classification schemes for probable dengue fever were applied to the cohort. However, when the cases were stratified into age groups, fewer older adults reported symptoms such as myalgia, arthralgia, retro-orbital pain and mucosal bleeding, resulting in reduced sensitivity of the WHO classification schemes. On the other hand, the risks of severe dengue and hospitalization were not diminshed in older adults, indicating that this group of patients can benefit from early diagnosis, especially when an antiviral drug becomes available. Our data also suggests that older adults who present with fever and leukopenia should be tested for dengue, even in the absence of other symptoms.ConclusionEarly clinical diagnosis based on previously defined symptoms that are associated with dengue, even when used in the schematics of both the WHO 1997 and 2009 classifications, is difficult in older adults.

Studies on serotype-specific features of dengue and disease severity on adults are limited. We prospectively recruited adult febrile patients without alternate diagnosis to dengue from April 2005 to December 2011. Outcomes were defined using both the World Health Organization (WHO) 1997 and 2009 criteria; Dengue hemorrhagic fever (DHF) and severe dengue (SD). Infecting serotype was identified in 469 dengue-confirmed patients comprising 22.0% dengue virus serotype 1 (DENV-1), 57.1% DENV-2, 17.1% DENV-3, and 3.8% DENV-4. Cases infected with DENV-1 were more likely to present with red eyes whereas presence of joint pain and lower platelet count was associated with DENV-2 cases. After adjusting for potential confounders, DENV-1 was associated with both DHF (adjusted Relative Risk [aRR] = 1.74) and SD (aRR = 2.1) whereas DENV-2 had a lower risk of DHF (aRR = 0.5). DENV-1 genotype 1 and DENV-2 cosmopolitan were the predominant genotypes identified. Infecting dengue serotype and possibly genotype may play an important role in disease severity among adult dengue patients in Singapore.

Ink-jet printing of thermoelectric nanomaterials is successfully used to fabricate flexible thin film TE devices for power generation and cooling.

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