A Thermodynamics Model for the Emergence of a Stripe‐like Binary SAM on a Nanoparticle Surface

It has been under debate if a self‐assembled monolayer (SAM) with two immiscible ligands of different chain lengths and/or bulkiness can form a stripe‐like pattern on a nanoparticle (NP) surface. The entropic gain upon such pattern formation due to difference in chain lengths and/or bulkiness has been proposed as the driving force in literature. Using atomistic discrete molecular dynamics simulations it is shown that stripe‐like pattern could indeed emerge, but only for a subset of binary SAM systems. In addition to entropic contributions, the formation of a striped pattern also strongly depends upon interligand interactions governed by the physicochemical properties of the ligand constituents. Due to the interplay between entropy and enthalpy, a binary SAM system can be categorized into three different types depending on whether and under what condition a striped pattern can emerge. The results help clarify the ongoing debate and our proposed principle can aid in the engineering of novel binary SAMs on a NP surface.     

Molecular Dynamics Study of Radial Corrugation in Carbon Nanotubes

Molecular dynamics simulations of multiwalled carbon nanotubes under hydrostatic pressure are performed to elucidate the novel class of radial buckling in the systems. It is revealed by all-atom simulations that the initial circular cross section transforms into a flower-like wavy configuration at critical pressure on the order of hundreds mega pascals or less. This kind of radial buckling, called radial corrugation, originates from the competition of the three relevant energies in the system: in-plane strain energy, van der Waals interaction energy between adjacent tubes, and out-of-plane bending energy. Their possible consequences for physical properties of carbon nanotubes are also discussed.     

Molecular Understanding and Design of Zwitterionic Materials

Zwitterionic materials have moieties possessing cationic and anionic groups. This molecular structure leads to unique properties that can be the solutions of various application problems. A typical example is that zwitterionic carboxybetaine (CB) and sulfobetaine (SB) materials resist nonspecific protein adsorption in complex media. Considering the vast number of cationic and anionic groups in the current chemical inventory, there are many possible structural variations of zwitterionic materials. The diversified structures provide the possibility to achieve many desired properties and urge a better understanding of zwitterionic materials to provide design principles. Molecular simulations and modeling are a versatile tool to understand the structure–property relationships of materials at the molecular level. This progress report summarizes recent simulation and modeling studies addressing two fundamental questions regarding zwitterionic materials and their applications as biomaterials. First, what are the differences between zwitterionic and nonionic materials? Second, what are the differences among zwitterionic materials? This report also demonstrates a molecular design of new protein‐resistant zwitterionic moieties beyond conventional CB and SB based on design principles developed from these simulation studies.     

Neurological and Epigenetic Implications of Nutritional Deficiencies on Psychopathology: Conceptualization and Review of Evidence

In recent years, a role for epigenetic modifications in the pathophysiology of disease has received significant attention. Many studies are now beginning to explore the gene–environment interactions, which may mediate early-life exposure to risk factors, such as nutritional deficiencies and later development of behavioral problems in children and adults. In this paper, we review the current literature on the role of epigenetics in the development of psychopathology, with a specific focus on the potential for epigenetic modifications to link nutrition and brain development. We propose a conceptual framework whereby epigenetic modifications (e.g., DNA methylation) mediate the link between micro- and macro-nutrient deficiency early in life and brain dysfunction (e.g., structural aberration, neurotransmitter perturbation), which has been linked to development of behavior problems later on in life.     

Real-Time Duplex Applications of Loop-Mediated AMPlification (LAMP) by Assimilating Probes

Isothermal nucleic-acid amplification methods such as Loop-Mediated isothermal AMPlification (LAMP) are increasingly appealing alternatives to PCR for use in portable diagnostic system due to the low cost, weight, and power requirements of the instrumentation. As such, interest in developing new probes and other functionality based on the LAMP reaction has been intense. Here, we report on the development of duplexed LAMP assays for pathogen detection using spectrally unique Assimilating Probes. As proof of principle, we used a reaction for Salmonella enterica as a model coupled with a reaction for λ-phage DNA as an internal control, as well as a duplexed assay to sub-type specific quarantine strains of the bacterial wilt pathogen Ralstonia solanacearum. Detection limits for bacterial DNA analyzed in individual reactions was less than 100 genomic equivalents in all cases, and increased by one to two orders of magnitude when reactions were coupled in duplexed formats. Even so, due to the more robust activity of newly available strand-displacing polymerases, the duplexed assays reported here were more powerful than analogous individual reactions reported only a few years ago, and represent a significant advance for incorporation of internal controls to validate assay results in the field.     

Graphite Oxide and Aromatic Amines: Size Matters

Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”.     

食品药品来源的CFTR氯离子通道抑制剂的研究进展

CFTR氯离子通道是目前国际上新兴的治疗分泌型腹泻的分子药靶,CFTR抑制剂通过阻断离子通道的过度分泌来治疗腹泻症状。由于其抑制剂极为稀少,因此CFTR抑制剂的筛选工作是相关领域中最基础、最关键的环节。天然产物兼具结构和生物活性的多样性,在新药和先导化合物的发现中起着重要作用,是药物开发的主要来源,而食品药品来源的天然产物更因为对人体安全无毒副作用而倍受青睐。食品药品来源的CFTR氯离子通道抑制剂对于CFTR相关的腹泻等疾病的机理研究和治疗具有重要价值,同时也为天然产物资源用于现代药物发现提供了依据。     

Chemical-Shift Perturbations Reflect Bile Acid Binding to Norovirus Coat Protein: Recognition Comes in Different Flavors

Bile acids have been reported as important cofactors promoting human and murine norovirus (NoV) infections in cell culture. The underlying mechanisms are not resolved. Through the use of chemical shift perturbation (CSP) NMR experiments, we identified a low-affinity bile acid binding site of a human GII.4 NoV strain. Long-timescale MD simulations reveal the formation of a ligand-accessible binding pocket of flexible shape, allowing the formation of stable viral coat protein–bile acid complexes in agreement with experimental CSP data. CSP NMR experiments also show that this mode of bile acid binding has a minor influence on the binding of histo-blood group antigens and vice versa. STD NMR experiments probing the binding of bile acids to virus-like particles of seven different strains suggest that low-affinity bile acid binding is a common feature of human NoV and should therefore be important for understanding the role of bile acids as cofactors in NoV infection.     

芳烃与烯烃烷基化反应的催化机理进展

芳烃与烯烃的反应在有机合成中应用广泛。随着环保要求的提高，用于芳烃烷基化反应的传统催化剂逐渐被新型绿色催化剂所替代。近年来研究发现离子液体和分子筛对该反应具有高效催化作用且环境友好。本文探讨了离子液体和分子筛的酸性，总结了相应的的催化机理，对有关实验和理论研究工作进行了分析。同时揭示了离子液体和分子筛的结构对其催化性能的影响，为烷基化反应进一步研究奠定了基础。分析表明离子液体既能作为B酸，也能作为L酸起催化作用；分子筛主要作为B酸起催化作用，同时其催化性能与孔道结构、孔径大小及反应物尺寸密切相关。离子液体的稳定性较差、成本较高，而分子筛失活较快，未来需围绕提高离子液体稳定性、改进其制备方法以降低成本及改善分子筛结构以延长使用周期等方面展开研究。