bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid Crystals Formed from Specific Supramolecular Interactions
Authors: Bruce Duncan W. 
Published: February 2012

Abstract
This chapter presents a critical overview of the use of specific, supramolecular interactions to induce liquid‐crystalline behavior where the presence of these interactions leads either to the induction of liquid crystallinity where this was not observed in the components separately, or to the modification of liquid crystal properties beyond that normally found in mixture systems. The chapter begins by accepting and discussing the fact that any observation of liquid‐crystalline behavior is a supramolecular phenomenon that depends on the presence of anisotropic dispersion forces. Some specific aspects to illustrate the point, for example, the induction of chiral phases from achiral components, are given. The main part of the chapter then discusses mesophase induction through quadrupolar interactions, charge transfer, hydrogen bonding, and halogen bonding, selecting examples of each to illustrate both the breadth of materials realized under each heading and also some of the issues that are important in the different approaches.
Self‐Assembly of Polymers into Soft Nanoparticles and Nanocapsules
Authors: Tang Jianbin , Zhu Dingcheng , Shen Youqing 
Published: February 2012

AbstractThe self‐assembly mechanisms of copolymers into nanostructures and their applications in nanomedicines have attracted increasing attention recently. The basis of the various aspects of this research area is the correlation of the polymer structures to the type and structural parameters of the nanostructures formed, which are the keys for researchers to design needed nanostructures for applications such as drug delivery. Along this line, this chapter briefly summarizes the principles of formation, theoretical predications of structural parameters, and the basic experimental aspects in preparation and characterization, as well as recent progress and applications of polymer micelles and vesicles in nanomedicine.
Replication Processes—From Autocatalysis to Systems Chemistry
Authors: Huck Jürgen , Philp Douglas 
Published: February 2012

AbstractChemical systems capable of templating and catalyzing their own synthesis — known as replicating systems — have started to appear in the chemical literature over the last 25 years. In a biological context, these systems represent a link with the origin of life, and their behavior could perhaps provide a model for prebiotic chemical evolution. For the synthetic chemist, they represent the ultimate synthetic machine, capable of directing the formation of a large number of identical copies of themselves from a single template molecule. One of the driving forces in this research area has been recognizing the important role that replication plays in biology and attempting to answer a fundamental question — “Is the structural complexity of nucleic acids necessary to store and transmit information at a molecular level”? In addition, the concept of a chemical template that is capable of making billions of exact copies of itself, given appropriate starting materials, is a highly attractive one for the emerging field of systems chemistry. The development of a detailed understanding of the behavior of replicating systems has important perspectives for both biology and chemistry.
Artificial Enzyme Mimics
Authors: Geibel Barbara , Merschky Michael , Rether Carolin , Schmuck Carsten 
Published: February 2012

AbstractEnzymes are among the most effective catalysts known so far both in terms of their efficiency as well as selectivity. They can achieve rate accelerations of up to a factor of 1011and more, and sometimes react exclusively with only one single stereoisomer of a substrate if required. Enzymes make use of various different mechanisms of catalysis such as transition‐state binding, acid–base catalysis, nucleophilic catalysis, entropic control of reactions, and so on, with roughly half the known enzymes using metal ions while the other half solely relies on organic functional groups. Owing to these fascinating features of enzymes, chemists have tried to mimic enzymes early on developing artificial enzyme models. Over the years, a multitude of functional artificial enzyme models for very different types and classes of enzymes were developed, some closely mimicking the mode of action of their natural counterparts whereas others just adopt some general features found in enzymes. We briefly discuss some selected examples of artificial enzyme mimics in this review. Of course, the following examples are only a few picked out of a great variety. We do not attempt to provide a complete overview in respect to enzymes that are mimicked or models that were developed, but rather focus on the different approaches and concepts used to imitate an enzyme. The choice of examples is purely reflecting our personal preferences and is not implied to indicate that any work not mentioned is less interesting.We have arranged the examples of enzyme mimics and presented roughly according to their increasing chemical and structural complexity, starting with simple metal complexes (Section 1), then discussing cyclodextrin and related enzyme mimics (Section 2) before focusing on polymer‐ and dendrimer‐derived systems (Section 3). Miniproteins and oligopeptides with defined structures are then discussed (Section 4) before we end with a brief description of catalytic antibodies (Section 5).
Reaction Networks
Authors: Dadon Zehavit , Wagner Nathaniel , Cohen‐Luria Rivka , Ashkenasy Gonen 
Published: February 2012

AbstractThe study of synthetic molecular networks is of fundamental importance for understanding the organizational principles of biological systems. An important family of the nonenzymatic systems uses template‐directed catalysis as a means of wiring the network components and controlling their dynamics and replication. As such, these networks have received considerable attention with respect to possible scenarios in the origins of life and early molecular evolution. In this review, we summarize recent studies aimed at the design and functional analysis of peptide‐based replicating networks. Design of the networks, by simultaneous implementation of autocatalysis and cross‐catalysis, is first explained. It is followed by detailing how one can simulate the complex networks' kinetics, and how it is possible to manipulate the catalytic processes and thus to control the entire network topology. At the end, we discuss the relevancy of these findings to the study of biochemical networks, such as RNA networks.
Reactivity in Nanoscale Vessels
Authors: Breiner Boris , Nitschke Jonathan R. 
Published: February 2012

Abstract
Reactivity in nanoscale vessels is based on host–guest chemistry, the “chemistry of the inner phase.” This term was coined by Cram to describe the mechanical entrapment of molecules within other molecules, and the new reactivity patterns that could be observed on this encapsulation. He quickly realized that encapsulated molecules showed behavior that was different from what was known about them in solution and concluded that molecules (“guests”) that were trapped inside another molecule (“host”) were in essence in a different state of matter. The field of host–guest chemistry has expanded drastically since his initial findings, and new reactions within the confines of a host are discovered at an ever‐increasing rate. We will try to put relevant findings into order, in an attempt to highlight common themes and to illustrate general trends.
Reactions in Dynamic Self‐Assemblies
Authors: Moulin E. , Giuseppone N. 
Published: February 2012

Abstract
The dynamic processes in self‐assemblies are involved in numerous domains that span throughout the modern aspects of chemical sciences, going from fundamental investigations into the origin of life to the most striking technological applications in medicine or electronics. This chapter aims at providing the reader with a brief overview of the concepts that link chemical reactivity with dynamic templates and catalysts made of large supramolecular assemblies. Specifically, we discuss kinetic and thermodynamic aspects of selected examples depending on (i) the nature of the matrix — that is, micelles, vesicles, liquid crystals, and gels; (ii) the nature of their constituents — that is, surfactants, block copolymers, bioactive macromolecules; and (iii) the nature of the chemical transformations that are performed — that is, reaction of small organic molecules, biomolecules, polymerizations, nanoparticle formation, and also reactions that involve the constituents of the matrix themselves as observed, for instance, in self‐reproducing systems. In each section, we combine original papers that paved the field together with more recent works of particular interest; several reviews are also referenced to help in accessing a more comprehensive literature.
Membrane Transport
Authors: Quesada Roberto 
Published: February 2012

AbstractMembranes are not permeable to charged species, and facilitated ion transport is an essential cell function. Natural ion channels are mainly complex transmembrane proteins, and insights into the structure of these proteins have provided valuable hints for the design of synthetic ion transport mechanisms. Development of new transmembrane transporters has potential applications in medicinal chemistry (antibiotics, channel replacement therapies, and drug delivery) as well as cell biology research, catalysis, or sensing. In this article, synthetic model systems for the facilitated ion translocation in lipid bilayers are presented. Examples of ion channels, both unimolecular and self‐assembled channels as well as ion carriers provide an overview of successful designs and combinations of ion receptor interactions used to facilitate transmembrane transport.
Supramolecular Approaches to Medicinal Chemistry
Authors: Biros Shannon , Hof Fraser 
Published: February 2012

AbstractThis chapter describes how the central concept of molecular recognition links the distinct pursuits of supramolecular chemistry and drug development. Topics covered include the use of enzyme inhibitors as tools for measuring the strengths of weak interactions, the use of drug targets as templates for the formation of their own inhibitors (bothin situtemplated synthesis and dynamic combinatorial chemistry (DCC)), and the use of traditionally supramolecular scaffolds for the recognition of large protein surfaces.
Atomic Force Microscopy Measurements of Supramolecular Interactions
Authors: Song Bo , Schönherr Holger 
Published: February 2012

Abstract
Atomic force microscopy‐based single‐molecule force spectroscopy (SMFS) has matured in the past decade to become a reliable method to probe the rupture of individual supramolecular bonds and to analyze the strength of noncovalent interactions in a wide range of conditions. SMFS undoubtedly also has a major impact on the biophysical field, an area of research that will be excluded from our discussion. Instead, we focus attention on synthetic supramolecular systems. In this chapter, we summarize the fundamental experimental setup and design, discuss strategies to identify single‐molecule events, provide some rudimentary theory, and finally illustrate the power of the methodology by discussing selected examples. The examples encompass a broad range of interaction types, and hence interaction strengths and typical time scales, including hydrogen bonding, host–guest interactions, π–π interactions, hydrophobic interactions, and metal–ligand coordination. The force data for simple, binary complexes receive similar attention as highly complex supramolecular systems with multiple bond switches in parallel or in series. Finally, we mention areas of potential further development.
Two‐Dimensional Supramolecular Chemistry
Authors: Phillips Anna G. , Beton Peter H. , Champness Neil R. 
Published: February 2012

Abstract
Two‐dimensional assembly of molecular assemblies on surfaces represents a significant challenge to chemists, materials scientists, and physicists. Supramolecular chemistry offers many advantageous strategies for the development of such arrays through the use of intermolecular interactions to control the process of molecular organization and self‐assembly. This article reveals how hydrogen bonds, dipole–dipole, van der Waals interactions, and metal–ligand coordination can be used to assemble two‐dimensional arrays on surfaces. Such supramolecular assemblies can be used to trap guest species mimicking host–guest chemistry in the solution phase. By the use of the molecular resolution of scanning‐probe microscopies, particularly scanning tunneling microscopy, the precise arrangement of the supramolecular assemblies can be probed and evaluated including the relative orientation with respect to the surface. The influence of the surface on the self‐assembly process is discussed and it is shown that far from playing a passive role in the self‐assembly process the substrate can strongly influence the supramolecular chemistry observed. Such images provide great insight into the advantages and restrictions of working in two dimensions in comparison to the solution phase or the solid state.
Development and Application of Multiple‐Probe Scanning Probe Microscopes
Authors: Nakayama Tomonobu , Kubo Osamu , Shingaya Yoshitaka , Higuchi Seiji , Hasegawa Tsuyoshi , Jiang Chun‐Sheng , Okuda Taichi , Kuwahara Yuji , Takami Kazuhiro , Aono Masakazu 
Published: February 2012

AbstractIn the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple‐probe scanning probe microscopes (MP‐SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP‐SPM is used not only for observing high‐resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double‐probe STM (DP‐STM) developed by the authors, which was subsequently modified to a triple‐probe STM (TP‐STM), has been used to measure the conductivities of one‐dimensional metal nanowires and carbon nanotubes and also two‐dimensional molecular films. A quadruple‐probe STM (QP‐STM) has also been developed and used to measure the conductivity of two‐dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple‐probe AFM (QP‐AFM) with four conductive tuning‐fork‐type self‐detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general‐purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP‐AFM. These developments and applications of MP‐SPMs are reviewed in this paper.
Validation of the Charcot–Marie–Tooth disease pediatric scale as an outcome measure of disability
Authors: Burns Joshua , Ouvrier Robert , Estilow Tim , Shy Rosemary , Laurá Matilde , Pallant Julie F. , Lek Monkol , Muntoni Francesco , Reilly Mary M. , Pareyson Davide , Acsadi Gyula , Shy Michael E. , Finkel Richard S. 
Published: February 2012

AbstractObjective:Charcot–Marie–Tooth disease (CMT) is a common heritable peripheral neuropathy. There is no treatment for any form of CMT, although clinical trials are increasingly occurring. Patients usually develop symptoms during the first 2 decades of life, but there are no established outcome measures of disease severity or response to treatment. We identified a set of items that represent a range of impairment levels and conducted a series of validation studies to build a patient‐centered multi‐item rating scale of disability for children with CMT.Methods:As part of the Inherited Neuropathies Consortium, patients aged 3 to 20 years with a variety of CMT types were recruited from the USA, United Kingdom, Italy, and Australia. Initial development stages involved definition of the construct, item pool generation, peer review, and pilot testing. Based on data from 172 patients, a series of validation studies were conducted, including item and factor analysis, reliability testing, Rasch modeling, and sensitivity analysis.Results:Seven areas for measurement were identified (strength, dexterity, sensation, gait, balance, power, endurance), and a psychometrically robust 11‐item scale was constructed (CMT Pediatric Scale [CMTPedS]). Rasch analysis supported the viability of the CMTPedS as a unidimensional measure of disability in children with CMT. It showed good overall model fit, no evidence of misfitting items, and no person misfit, and it was well targeted for children with CMT.Interpretation:The CMTPedS is a well‐tolerated outcome measure that can be completed in 25 minutes. It is a reliable, valid, and sensitive global measure of disability for children with CMT from the age of 3 years. ANN NEUROL 2012;
Stroke recurrence in children with congenital heart disease
Authors: Rodan Lance , McCrindle Brian W. , Manlhiot Cedric , MacGregor Daune L. , Askalan Rand , Moharir Mahendra , deVeber Gabrielle 
Published: February 2012

AbstractObjective:Pediatric arterial ischemic stroke (AIS) carries an important morbidity and mortality burden. Congenital heart disease (CHD) is among the most important risk factors for pediatric AIS. Data on stroke recurrence in childhood CHD are lacking, resulting in uncertainty regarding optimal strategies for preventing recurrence.Methods:In the Canadian Pediatric Ischemic Stroke Registry–Toronto site, we identified children (birth to 18 years) with CHD diagnosed with AIS during 1992–2008. Data were abstracted from both stroke and cardiac surgery databases. Time‐dependent outcomes (death and recurrent stroke) following sentinel stroke were parametrically modeled in competing risk analysis. Factors predicting stroke recurrence in parametric survival models were sought in parametric survival model analyses using backward variable selection of variables.Results:A total of 135 patients (19 with recurrence, 116 without recurrence) were studied. In competing risk analysis, 10 years following sentinel stoke, 27% had experienced a stroke recurrence, 26% had died, and 47% were alive and free from recurrence. Stroke recurrence risk decreased over time from sentinel stroke. Approximately 50% of patients were receiving anticoagulation at recurrence. Significant factors associated with recurrence included the presence of a mechanical valve, prothrombotic condition, and an acute infection at the time of sentinel stroke. Hazard of mortality after recurrence was similar to mortality after sentinel stroke (hazard ratio, 1.3; p = 0.75).Interpretation:Stroke recurrence was relatively common in neonates and children with CHD. Identified groups of patients at increased risk may require more aggressive secondary prophylaxis, especially in the early poststroke period. ANN NEUROL 2012;72:103–111
Rapid synthesis and characterization of chitosan‐g‐poly(D,L‐lactide) copolymers with hydroxyethyl chitosan as a macroinitiator under microwave irradiation
Authors: Luo Binghong , Yang Jing , Zhao Jianhao , Hsu ChungEn , Li Jianhua , Zhou Changren 
Published: February 2012

AbstractHydroxyethyl chitosan (HECS) was first prepared by the reaction of 2‐chloroethanol with chitosan (CS). Then, CS‐g‐poly(D,L‐lactide) (PDLLA) copolymers were synthesized through the ring‐opening polymerization of D,L‐lactide with CS and HECS as the macroinitiators, respectively, under microwave irradiation. The optimal synthesis conditions obtained by an orthogonal experiment were as follows: microwave power = 10 W, temperature = 130°C, irradiation time = 15 min, and catalyst concentration = 0.05 mol %. The reactivity of CS was improved by hydroxyethylation, which contributed to a higher percentage of grafting. Compared with the conventional thermal polymerization, the microwave polymerization method showed a significantly higher polymerization rate and improved efficiency. An enhanced percentage of grafting ranging from 236.25 to 317.50%, and an average degree of polymerization of PDLLA side chains ranging from 13.25 to 24.17 were achieved under microwave irradiation when the value of nD,L‐lactide/nminoglucoside units was increased from 20 : 1 to 40 : 1. The higher percentage of grafting facilitated decreases in the crystallinity and thermal stability of the copolymers, which were attributed to the weakening intramolecular and intermolecular hydrogen bonds of CS. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Structure and molecular dynamics of multilayered polycarbonate/polystyrene films
Authors: Walczak M. , Ciesielski W. , Galeski A. , Potrzebowski M. J. , Regnier G. , Hiltner A. , Baer E. 
Published: February 2012

AbstractMultilayered film polycarbonate/polystyrene (PC/PS) comprising 257 layers with total thickness 125 μm was made by coextrusion process. The nominal thickness of PC layers was 680 nm, and the nominal thickness of PS layers was 290 nm. Additionally, the control samples of PC and PS with the thickness of 125 μm were coextruded in the same way. There was reasonably good correlation between the PC and PS layers real thickness as measured by AFM and the estimated thickness determined from the processing parameters. Significant shift of glass transition temperature is observed in multilayer film: for PS component toward higher temperature while PC still being glassy and for PC toward lower temperature while PS being in rubbery phase. To investigate the amplitude and geometry of fast segmental motions, the LG‐CP NMR technique under fast magic‐angle spinning was used. 2D 13C1H LG‐CP spectra of PC, PS, and PC/PS 70/30 were recorded at various temperatures. Cross sections of aromatic carbons spectra show us the influence of PC on PS and vice versa. It gives us also the information about PS and PC segmental motion as a function of temperature: above the glass transition temperature of PS, the PC component of a multilayer film, although still being in glassy state, becomes more flexible. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012