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Developing innovative tools that facilitate the understanding of sophisticated biological systems has been one of the Holy Grails in the physical and biological sciences. In this Commentary, we discuss recent advances, opportunities, and challenges in the use of nanomaterials as a precision tool for biology and medicine. [ABSTRACT FROM AUTHOR]

We investigate the collective dynamics of comblike polymers displaying nanosegregation in side groups and main-chain rich domains, where side groups and backbones are dynamically equivalent. Neutron spin-echo experiments on poly(alkylene oxide)s with increasing side-group length have been focused on the decay of inter- and intradomain correlations and are complemented with molecular dynamics simulations on a coarse-grained model. In general, a good qualitative agreement between simulation and experiment is found. The collective times at inter- and intradomain levels converge with decreasing temperature, implying a common glass transition, and separate at high temperatures, revealing an increasing role of connectivity. The features of collective relaxations--regarding stretching, characteristic time, and temperature dependence--are independent of branching. The standard stretching for side-group motions and the closeness of collective and self-motions show that the anomalies exhibited by dynamically asymmetric comblike macromolecules disappear. [ABSTRACT FROM AUTHOR]

We developed a simple method to pattern self-assembled monolayers of tetrazole triethoxylsilane with a variety of different molecules by photochemical microcontact printing. Under irradiation, tetrazoles form highly reactive nitrile imines, which react with alkenes, alkynes, and thiols. The covalent linkage to the surface could be unambiguously demonstrated by fluorescence microscopy, because the reaction product is fluorescent in contrast to tetrazole. The modified surfaces were further analyzed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic force microscopy (AFM), and contact angle goniometry. Protein-repellent micropatterns, a biotin-streptavidin array, and structured polymer brushes could be fabricated with this straightforward method for surface functionalization. [ABSTRACT FROM AUTHOR]

The notions of a reaction path and a reaction coordinate are central to chemistry as they provide low-dimensional descriptions of complex molecular processes. Here we discuss how to define, compute, and use the reaction paths for chemical transformations in molecules that are subjected to mechanical stress and thus driven toward regions of conformational space that are otherwise inaccessible both in computational studies and in reality. We further show that the circuitous nature of mechanochemical pathways often makes their one-dimensional description impossible and describe how multidimensional effects can be detected experimentally. [ABSTRACT FROM AUTHOR]

Women made many early and outstandingcontributions to X-ray crystallography at a time when they were excludedfrom most other branches of physical science. The etiology of thisbright spot in the social evolution of science is sought in earlychildhood education, especially the Froebel kindergarten that wasrooted in symmetry and lattice building exercises. This connectionis explored through the formative educational experiences of eightcrystallographers that are compared with those of eight astronomers.Associations with Froebel’s pedagogy are ubiquitous in thebiographies of the crystallographers and wholly absent in the biographiesof astronomers. Creating a more democratic scientific enterprise requiresunderstanding the mechanisms for increasing the participation of membersof unrepresented genders and ethnicities. Some of these mechanismsmay be found in history. One of the crystallographers profiled, IsabelEllie Knaggs (1893–1981), made a major contribution to theX-ray analysis of organic compounds by establishing that carbon atomsin isolated molecules adopt tetrahedral coordination geometries. Thisdetermination was a capstone on the stereochemistry of the preceding50 years. Another scientist, working independently, exclusively claimedthis discovery. Thus, while studying the general disenfranchisementof women in science, a particular injustice not heretofore recognizedcame into focus. [ABSTRACT FROM AUTHOR]

In a recent article by the authors, the suggestion was made that arrow pushing, a widely used tool in organic chemistry, could also be profitably employed in the teaching of introductory inorganic chemistry. A number of relatively simple reactions were used to illustrate this thesis, raising the question whether the same approach might rationalize a broader range of main-group element reactions that are commonly included in descriptive inorganic texts. This question is answered here in the affirmative, based on analyses of six reactions (in a nod to Alice in Wonderland) that to the uninitiated would appear puzzling to near-impenetrable as exercises in arrow pushing. The examples chosen strongly suggest that the arrow-pushing approach is applicable to the great majority of reactions involving molecular p-block compounds. [ABSTRACT FROM AUTHOR]

Newly emerged xanthone derivativeshave attracted considerableinterests as a novel class of potent α-glucosidase inhibitors.To provide insights into the inhibitory and binding mechanisms ofxanthone-based inhibitors toward α-glucosidase, we carried outexperimental and theoretical studies on two typical xanthone derivatives,i.e., 1,3,7-trihydroxyxanthone and 1,3-dihydroxybenzoxanthone. Theresults indicate that these two xanthone derivatives belong to noncompetitiveinhibitors and induce a loss in the α-helix content of the secondarystructure of α-glucosidase. Docking simulation revealed theexistence of multiple binding modes, in which polyhydroxyl groupsand expanded aromatic rings acted as two key pharmacophores to formH-bonding and π–π stacking interactions with α-glucosidase.The fact that 1,3,7-tridroxyxanthone and 1,3-dihydroxybenzoxanthoneexhibited significant synergetic inhibition to α-glucosidasestrongly suggests that both xanthone derivatives simultaneously bindto the distinct noncompetitive sites of yeast’s α-glucosidase.On the basis of the plausible binding clues, synergetic inhibitioncan be developed to be a promising strategy to achieve enhanced inhibitoryactivities. [ABSTRACT FROM AUTHOR]

Solid state nuclear magnetic resonance (NMR) measurements at low temperatures have been common in physical sciences for many years and are becoming increasingly important in studies of biomolecular systems. This Account reviews a diverse set of projects from my laboratory, dating back to the early 1990s, that illustrate the motivations for low-temperature solid state NMR, the types of information that are available from the measurements, and likely directions for future research. These projects include NMR studies of both physical and biological systems, performed at low (cooled with nitrogen, down to 77 K) and ultralow (cooled with helium, below 77 K) temperatures, and performed with and without magic-angle spinning (MAS). [ABSTRACT FROM AUTHOR]

The article examines how bulk material property can be directly influenced by molecular surface chemistry. While showing how surface chemistry and self-assembled monolayers (SAMs) control the macroscopic properties of materials requires specialized instrumentation, the article demonstrates how students can directly measure a macroscopic property. The method involves the flotation of glass coverslips on water to alter the glass' terminal surface groups.

Gentle manipulation of micrometer-sized dielectric objectswithoptical forces has found many applications in both life and physicalsciences. To further extend optical trapping toward the true nanometerscale, we present an original approach combining self-induced backaction (SIBA) trapping with the latest advances in nanoscale plasmon engineering.The designed resonant trap, formed by a rectangular plasmonic nanopore,is successfully tested on 22 nm polystyrene beads, showing both single-and double-bead trapping events. The mechanism responsible for thehigher stability of the double-bead trapping is discussed, in lightof the statistical analysis of the experimental data and numericalcalculations. Furthermore, we propose a figure of merit that we useto quantify the achieved trapping efficiency and compare it to prioroptical nanotweezers. Our approach may open new routes toward ultra-accurateimmobilization and arrangement of nanoscale objects, such as biomolecules. [ABSTRACT FROM AUTHOR]

The article focuses on the important aspects of effective core potential's (ECP's) theoretical background. It mentions that ECP has two main branches such as the model potential (MP) and pseudopotential (PP) approach. It states that in molecular quantum chemistry and solid state physics, ECP approach change from semiempirical approach to ab initio, with independent ECP development. However, ECP method became quantum chemistry's workhorse due to the lack of competitive alternative approaches.

It may be observed that, when dew drops form, although they may be positioned randomly on flat leaves, they tend to accumulate at the pointed ends of thin, slightly conical growths. We discuss here the basic physics leading to this phenomenon. [ABSTRACT FROM AUTHOR]

Dinucleoside 5',5'-polyphosphates (N(p) nN) play important roles in biological processes and have been developed into drugs. However, their synthesis still remains a challenge. Here we report a rapid and general approach to the synthesis of dinucleoside 5',5'-polyphosphates by coupling highly reactive nucleoside 5'-monophosphate-N-methylimida-zolium salts donors with nucleoside 5'-mono-, -di-, and -triphosphate acceptors. [ABSTRACT FROM AUTHOR]

The article discusses the aspects of a program in which college teachers develop and enforce hands-on, experiments related to polymers to support a standard prescribed for high school chemistry course and a middle school elective course. It states that feedback-oriented and interactive experimentation design are emphasized as significant elements to the success of the program. Moreover, it notes that experiments have been conducted in two immensely different institutions.

The article focuses on the new instructional model called Argument-Driven Inquiry (ADI) that can be utilized for laboratory course in undergraduate college chemistry. It states that the ADI is created to offer students with a chance to develop their own method to gather data, to conduct investigations, and use data to answer research questions. Moreover, it notes that the model presents a detailed semester pacing schedule for general chemistry I laboratories.

The article discusses the tools used at nanohub.urg Web site for making electronic structure calculations and displays the results into a package. It states that the package can be used as part of an upper-level quantum chemistry course that is mainly directed at undergraduate engineering students. Moreover, the students were given assignments to help them gain practice with computational chemistry software.

The article discusses the factors to consider on how to implement the activity model of inquiry in the general chemistry classroom and how undergraduate students perceived scientific inquiry. It states that students are asked to react to essay and a pre-and post questionnaire designed to evaluate primitive and informed views of nature of science. Moreover, it notes that the three components of scientific literacy include basic content, the process, and the socio-cultural premises.

Clusters of tetracene molecules with different numbers of attached (Ar)N, (Ne)N and (H2)N particles (N = 1-2000) are assembled inside superfluid He nanodroplets and studied via laser-induced fluorescence. The frequency shift of the fluorescence spectrum of the tetracene molecules is studied as a function of cluster size and pickup order of tetracene and cluster species. For (Ar)N and (Ne)N clusters, our results indicate that the tetracene molecules reside inside the clusters when tetracene is captured by the He nanodroplet before the cluster species; conversely, the tetracene molecules stay on the surface of the clusters when tetracene is captured after the cluster species. In the case of (H2)N clusters, however, tetracene molecules reside inside the (H2)N clusters irrespective of the pickup order. We conclude that (Ar)N and (Ne)N clusters are rigid at T = 0.38 K, while (H2)N clusters of up to N = 2000 remain fluxional at the same temperature. The results may also indicate the occurrence of heterogeneous nucleation of the (H2)N clusters, which is induced by the interaction with tetracene chromophore molecules. [ABSTRACT FROM AUTHOR]

Computer simulations and experiments have been performed to quantify the effects of nozzle shape and skimmer placement on high-density supersonic jets. It is shown that the on axis beam intensity achieved is much higher than intensity achieved using standard sonic nozzles. Changes in skimmer design and positioning are required to allow this intense jet to propagate in a typical supersonic beam setup. [ABSTRACT FROM AUTHOR]

We present an ab initio study of the effect of spin-orbit coupling on the dynamical properties of the Tl-(0001 ) surface as well as on the electron-phonon interaction at the surface. The calculations based on density-functional theory were carried out using a linear response approach and a mixed-basis pseudopotentia] method. It is shown that the spin-orbit effects on the phonon spectrum and the electron-phonon interaction at the Fermi level of the surface are weak but conspire to a reduction in the electron-phonon coupling. [ABSTRACT FROM AUTHOR]

A simple expression for the asymptotic exchange energy of heteronuclear dimers is derived from the surface integral method. A five-dimensional hypersurface, consisting of all spherical surfaces centered at the nucleus of the atom with higher ionization energy, more appropriate for the case where the two atoms have different ionization energies, is used in the surface integral. All integrals are carried out analytically. Compared with the exchange energy of Smirnov and Chibisov, which is also obtained from the surface integral method with a hypersurface consisting of all infinite planes perpendicular to the internuclear axis, the present result is much simpler. The exchange energies of alkali hydrides are computed as an illustration. It is shown that the present method and the method of Smirnov and Chibisov are complementary to each other. [ABSTRACT FROM AUTHOR]

The utility of a continuous beam of He droplets for the assembly and surface deposition of AgN clusters, (N) ~ 300-6000, is studied with transmission electron microscopy. Images of the clusters on amorphous carbon substrates obtained at short deposition times have provided for a measure of the size distribution of the metal clusters. The average sizes of the deposited clusters are in good agreement with an energy balance based estimate of AgN cluster growth in He droplets. Measurements of the deposition rate indicate that upon impact with the surface the He-embedded cluster is attached with high probability. The stability of the deposited clusters on the substrate is discussed. [ABSTRACT FROM AUTHOR]

F1-ATPase is the catalytic domain of F1Fo-ATP synthase and consists of a hexameric arrangement of three noncatalytic α and three catalytic ß subunits. We have used unbiased molecular dynamics simulations with a total simulation time of 900 ns to investigate the dynamic relaxation properties of isolated β-subunits as a step toward explaining the function of the integral F1 unit To this end, we simulated the open (βE) and the closed (βTP) conformations under unbiased conditions for up to 120 ns each using several samples. The simulations confirm that nucleotide-free ßE retains its open configuration over the course of the simulations. The same is true when the neighboring α subunits are included. The nucleotide-depleted as well as the nucleotide-bound isolated ßTP subunits show a significant trend toward the open conformation during our simulations, with one trajectory per case opening completely. Hence, our simulations suggest that the equilibrium conformation of a nudeotide-free β-subunit is the open conformation and that the transition from the closed to the open conformation can occur on a time scale of a few tens of nanoseconds. [ABSTRACT FROM AUTHOR]

Recent experiments (Wang et al., 2010) have found evidence of phase transitions of gases adsorbed on a single carbon nanotube. In order to understand the observations, we have carried out classical grand canonical Monte Carlo simulations of this system, for the cases of Ar and Kr on zigzag and armchair nanotubes with radius R > 0.7 nm. The calculated behavior resembles the experimental results in the case of Ar. However, the prominent, ordered phase found for Kr in both simulations and (classical) energy minimization calculations differs from that deduced from the experimental data. A tentative explanation of the apparent discrepancy is that the experiments involve a nanotube of rather large radius (>1.5 nm). [ABSTRACT FROM AUTHOR]

A stochastic theory is formulated for the sticking probability of a projectile scattered from a surface. The theory is then explored by applying it to a generalized Langevin equation model of the scattering dynamics. The theory succeeds in describing the known features of trapping on surfaces. At low energies sticking will occur only if there is an attractive interaction between the projectile and the surface. The probability of sticking at low energies is greater the lower the temperature and the deeper the attractive well of the particle as it approaches the surface. The sticking probability in the absence of horizontal friction tends to be lower as the stillness of the surface increases. However, in the presence of horizontal friction, increased stiffness may lead to an increase in the sticking coefficient. A cos2(θi) scaling is found only in the absence of corrugation and horizontal friction. The theory is then applied successfully to describe experimentally measured sticking probabilities for the scattering of Xe on a Pt(111) surface. [ABSTRACT FROM AUTHOR]

The method of local increments is used in connection with an embedded cluster approach and wave function based quantum chemical ab initio methods to describe the adsorption of a single CO molecule on the MgO(001) surface. The first step in this approach is a conventional Hartree-Fock calculation. The occupied orbitals are then localized by means of the Foster-Boys localization procedure, and the full system is decomposed into several "subunits" that consist of the orbitals localized at the CO molecule and at the Mg and O atoms of the MgO cluster. The correlation energy is expanded into a series of local n-body increments that are evaluated separately and independently. In this way, big savings in computer time can be achieved because (a) the treatment of a large system is replaced with a series of much faster calculations for small subsystems and (b) the big basis sets necessary for describing dispersion effects are only needed for the atoms in the respective subsystem while all other atoms can be treated by medium size Hartree-Fock type basis sets. The coupled electron pair approach, CEPA, an approximate coupled cluster method, is used to calculate the correlation energies of the various subsystems. For the vertical adsorption of CO on top a Mg atom of the MgO(001 ) surface with the C atom toward Mg, the individual one- and two-body increments are calculated as functions of the CO-MgO separation and a full potential energy curve is constructed from them. A very shallow minimum with an adsorption energy of 0.016 eV at a Mg-C distance of 3.04 Å is found at the Hartree -Fock level, while inclusion of correlation (dispersion) effects shortens the Mg-C distance to 2.59 Å and yields a much larger adsorption energy of 0.124 eV. This is in very good agreement with the best experimental value of 0.14 eV. The basis set superposition error, BSSE, was fully corrected for by the counterpoise method and the bonding mechanism was analyzed at the Hartree-Fock level by means of the constrained space orbital variation, CSOV, analysis. [ABSTRACT FROM AUTHOR]

We develop a model, based on pairwise additive He-Mg and He-O interactions, for the potential energy of He adsorbates above a rigid MgO(100) surface. The attractive long-range He-Mg and He-O interactions are assumed to have the form C6/r6 with the C6 coefficients determined from atomic data within the context of the Slater-Kirkwood approximation. The repulsive short-range He-Mg and He-O interactions are assumed to have the form Cp/rp, with the exponent p and the Cp coefficients taken as adjustable parameters. We find that for p = 9, the Cp coefficients can be chosen so that the laterally averaged He-MgO(100) pairwise additive interaction supports low-lying selective adsorption states, some of whose energies agree very well with the states' apparent energies inferred from experimental measurements. However, for realistic values of the adjustable parameters that define our model, the lateral corrugation of the model pairwise additive He-MgO(100) potential energy surface far exceeds the corrugation that has been inferred both from experimental measurements and from density functional calculations of the short-range He-MgO(100) interaction. [ABSTRACT FROM AUTHOR]

There have been a few experimental reports of self-assembled adlayers of bis-fullerene molecules on solid substrates. Most of these studies suggest the adsorbate molecules are lying down on the surface, with the fullerene moieties almost close packed. However, very little theoretical work has been carried out on such systems, and little is known about the roles played by different parts of the potential energy in driving the self-assembly. We carry out a Temperature Replica Exchange Monte Carlo study here of two representative bis-fullerene molecules on a metal substrate. We use a coarse-grained model potential energy function, in which certain parameters can be varied within the range of their experimental uncertainty. The molecules investigated consist of two fullerene moieties bonded by a rigid bridging group. In particular, the effect of the strength of the fullerene interaction EFG with the substrate (nominally Au(111)) has been investigated in detail. To ensure efficient sampling of the rugged potential energy surfaces encountered in the simulations, we utilize replica exchange techniques. These enable us to construct free energy landscapes for the system. We find that for relatively low values of EFG the molecules form standing-up adlayers. By contrast, for higher values of EFG lying-down adlayers dominate. For one molecule, two different crystalline adlayer morphologies have been identified. The detailed structure of the lying-down layer is a function of the temperature and of the group used to bridge the fullerene moieties. [ABSTRACT FROM AUTHOR]

The use of damping functions to correct the multipole expansion at short-range is explored. Damping functions for the terms in the multipole expansion can be determined ab initio as a linear combination of analytic functions of the separation between sites, but there are additional short-range terms that have different angular dependence. The approach provides a detailed ab initio description of the penetration energy correction to the multipole expansion in an easily comprehensible form. [ABSTRACT FROM AUTHOR]

We present potential energy curves calculated at the CCSD(T) level of theory for Ga+-RG and In+ -RG complexes (RG = He-Rn). Spectroscopic parameters have been derived from these potentials and compared to previously calculated parameters for the Al+-RG and Tl+-RG complexes. Additionally, for some cases, we compare these parameters with those obtained from electronic spectroscopic studies on excited states of the neutral species, arising from atomic-based d ← p excitations. The Ga+-RG and In+-RG potentials have also been used to calculate the transport coefficients for M+ traveling through a bath of RG atoms. [ABSTRACT FROM AUTHOR]

It is shown that a commensurate square monolayer solid of Kr/NaCl(001) can be stabilized with a model incorporating a rather large energy corrugation amplitude. Then a square bilayer is formed under a compression and preempts the formation of an incommensurate triangular monolayer lattice. The lattice dynamics of the commensurate monolayer may be complex, because the modeling admits the possibility that it has a (2 x 2) unit cell with four Kr atoms. [ABSTRACT FROM AUTHOR]

Published as part of the Crystal Growth & Design10th Anniversary Perspective. [ABSTRACT FROM AUTHOR]

The article presents an analytical chemistry experiment to explore liquid sequential injection chromatography (SIC) to teach fundamentals of separation methods. Liquid SIC is a novel analytical method developed from sequential injection analysis (SIA) to carry out multianalyte determinations and chromatographic separations. Details on mobile phase and sample preparation as well as hazards are discussed.

The article discusses the application of a microscale plastic equipment to chemical kinetics in the general chemistry laboratory. It discusses the use of the potassium iodine hydrogen peroxide iodine-clock reaction. The iodine-clock reaction contains two reactions including oxidation and reduction. The application of micropipets is discussed.

The article proposes a systematic approach to estimate the concentration of the chemical species in multi-equilibrium systems. It notes that the numerical calculation of chemical equilibrium problems is a basic skill required by chemistry students and is considered critical value in a wide range of areas in relation to chemistry. It displays a simple way of applying such calculations with the aid of a spreadsheet analysis tool.

A novel methodology to characterize gasoline and diesel streams into the molecular level is developed on the basis of molecular type homologous series (MTHS) matrix framework (Chem. Eng. Sci. 2005, 60, 6702−6717). The method comprises the enhancements of both representation matrix construction and transformation methodology of bulk properties into molecular composition. To improve the accuracy and adequacy of the representation model, different strategies are set up separately for gasoline and diesel streams for the consideration of isomers. By introducing statistical distribution and applying extensive bulk properties, the transformation approach is revolutionized to increase the usability, and tackle the challenge of possibly achieving significantly different molecular compositions from the same bulk properties of refining streams by existing transformation approaches. The proposed method is verified with both gasoline and diesel streams, and the results show a good agreement with measured data. [ABSTRACT FROM AUTHOR]

The development of protein-based materials with diverse mechanical properties will facilitate the realization of a broad range of potential applications. The recombinant Drosophila melanogastertranscription factor Ultrabithorax self-assembles under mild conditions in aqueous buffers into extremely extensible materials. By controlling fiber diameter, both the mechanism of extension and the magnitude of the mechanical properties can be varied. Narrow Ultrabithorax fibers (diameter 15 μm) reflects the increase in breaking strain with increasing diameter, apparently due to a change in structure. The breaking stress/strain of the widest fibers resembles that of natural elastin. Intermediate fibers display mixed properties. Fiber bundles retain the mechanical properties of individual fibers but can withstand much larger forces. Controlling fiber size and generating fiber superstructures is a facile way to manipulate the mechanical characteristics of protein fibers and rationally engineer macroscale protein-based materials with desirable properties. [ABSTRACT FROM AUTHOR]

The article focuses on linking art and chemistry for nonmajors and instrumental analysis students through the combination of literature and instrumental methods with focus in X-ray fluorescence (XRF) spectroscopy. It relates that undergraduate curriculum is slow in adopting XRF experiments despite the advances in its technique. It also presents the importance of XRF and its mapping ability to artwork as highlighted in a study on the analysis of an artwork by Vincent van Gogh.

The article examines the advances in the synthesis of organoborane polymers for optical, electronic, and sensory applications. The authors report that the first decade of the 21st century has experienced renewed interest and numerous discoveries in the field of main group organometallic chemistry. These developments include the discovery of unusual bonding modes, new materials, and new applications involving Group 14 and Group 15 elements.

A crystallographic study and theoretical analysis of the Si/Ga site preferences in the Gd5GaxSi4-x series is presented. Gd5GaxSi4-x adopt the orthorhombic Gd5Si4-type structure (space group Pnma, Z = 4) with a maximum Ga content near x = 1.00, as determined by single crystal and powder X-ray diffraction. Refinements from single crystal X-ray diffraction studies of the three independent sites for Si/Ga atoms in the asymmetric unit (interslab T1, intraslab T2 and T3) reveal partial mixing of these elements, with a clear preference for Ga substitution at the interslab T1 sites. To investigate site preferences of Si/Ga atoms, first-principles electronic structure calculations were carried out using the Vienna ab initio simulation package (VASP) and the Stuttgart tight-binding, linear-muffin-tin orbital program with the atomic sphere approximation (TB-LMTO-ASA). Analysis of various crystal orbital Hamilton population (COHP) curves provide some further insights into the structural tendencies and indicate the roles of both sizes and electronegativities of Ga and Si toward influencing the observed upper limit in Ga content in Gd5GaxSi4-x. The magnetic properties of two Gd5GaxSi4-x phases are also reported: both show ferromagnetic behavior with Curie temperatures lower than that for Gd5Si4. [ABSTRACT FROM AUTHOR]

Although inorganic halogen gases are believed to play key roles in the chemistry of the lower atmosphere, many of them have not yet been detected or measured in ambient air. This article describes some of the current techniques and future needs for inorganic halogens in air. (To listen to a podcast about this feature, please go to the Analytical Chemistry multimedia page at pubs.acs.org/page/ancham/audio/index.html.) [ABSTRACT FROM AUTHOR]

High-resolution nuclear magnetic resonance spectroscopy (NMR) has the capability of providing often unrivaled detail on molecular structure and dynamics. Through hyperpolarization, a decisive gain in signal strength can be realized, which extends the applicability of NMR to the investigation of rapid processes far from equilibrium. The progress of irreversible chemical and biochemical reactions can be followed by hyperpolarized NMR with relative ease, within an observable window encompassing the subsecond to second time scales. Here, we present a scheme that uses real-time, hyperpolarization enhanced NMR to make temporal correlations accessible in addition to simply monitoring reaction progress. Since nuclear spin states can be preserved even if the spin carrying atoms directly participate in a reaction, it becomes possible to correlate the positions of these atoms between the reactant and the product species, over time. We demonstrate the application of this technique to the Grignard addition of methylmagnesium bromide to 3-methylbenzophenone. The same experiment may be used for the determination of mechanisms and intermediate states in non-equilibrium processes in fields as varied as organic chemistry, enzymology, or protein folding. [ABSTRACT FROM AUTHOR]

Gold nanoparticles bound to substrates exhibit localized surface plasmon resonance (LSPR) in their optical extinction spectra at visible and near-infrared wavelengths. The LSPR wavelength is sensitive to the surrounding refractive index, enabling a simple, label-free immunoassay when capture antibodies are bound to the nanoparticles. Gold bipyramids are nanoparticles with a penta-twinned crystal structure, which have a sharp LSPR because of their high monodispersity. Bipyramid substrates were found to have a refractive index sensitivity ranging from 288 to 381 mn/ RIU (-0.62 to -0.68 eV/RIU), increasing with the nanoparticle size and aspect ratio. In an immunoassay, the bipyramid substrates yielded higher sensitivity than nanorods and nanospheres. An immunoassay sensitivity constant which depends on both the optical properties of the nanoparticle and conjugation chemistry was found to be KLSPR = 0.01 nm∙μm2 for gold bipyramids. [ABSTRACT FROM AUTHOR]

The article discusses the laboratory experiment that analyzes the lead content of ancient bronze coins through flame atomic absorption spectroscopy (FAAS) used to teach students on archaeometry and numismatics. The FAAS analysis is chosen despite of its destructive method and acid digestion due to some nondestructive techniques that are based only at surface measurements and destructive analysis made to obtain valuable chemical information. Students were able to experience the laboratory work of quantitative sample, solution preparation, and chemical data collection. The experiment shows the interdisciplinary nature of chemical sciences and the collaboration of two fields, chemistry and archeology, which can lead to more advances.

The article describes the functional groups and the development of functional group tables according to the periodic table. It is said that the tables order the functional groups by the position of their specific atom in the periodic table, indicating the bonding variability of the functional group carbon atom. It is mentioned that the use of classification tables can be viewed as molecular architecture, describing how molecules are designed based on their bonding variability. It is also discussed that students will be able to fully understand organic chemistry through the help of functional group tables.

Influences of periodic mechanical deformation (PMD) on spiral breakup that results from Doppler instability in excitable media are investigated. We present a new effect: a high degree of homogeneous PMD is favored to prevent the low-excitability-induced breakup of spiral waves. The frequency and amplitude of PMD are also significant for achieving this purpose. The underlying mechanism of successful control is also discussed, which is believed to be related to the increase of the minimum temporal period of the meandering spiral when the suitable PMD is applied. [ABSTRACT FROM AUTHOR]

Novel di- and tetraethynylethene (DEE and TEE) compounds functionalized with tetrathiafulvalene (TTF) donor groups and p-nitrophenyl acceptor groups were synthesized by palladium-catalyzed cross-coupling reactions under various conditions. The molecules are strong chromophores and were investigated for their optical properties. Placement of two TTFs and two p-nitrophenyls about a central TEE core provides a molecule with a high third-order optical nonlinearity. The molecules experience reversible oxidations of the TTF units, and the optical properties of the oxidized species were elucidated by spectroelectro-chemistry. The degree of quinoid character of the p-nitrophenyl in the molecules was determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]

1 ,4-Disubstituted 2,3-dioxabicyclo[2.2.2]oct-5-enes were dihydroxylated with osmium tetroxide to yield diols anti to the peroxide linkage in a highly selective manner. Reduction of the peroxide bond furnished cyclohexane-1,2,3,4-tetraols with toxocarol relative stereochemistry in excellent yield. This new methodology was employed to synthesize the natural product (1S,2R,3S,4R,5R)-2-methyl-5-(propan-2- yl)cyclohexane-1,2,3,4-tetrol (1) in a short sequence from (R)-α-phellandrene. Moreover, during the study of the chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols a hitherto unknown rearrangement was discovered which has wide applicability for the synthesis of 1,4-dicarbonyls, including optically enriched synthons. A broad range of mechanistic investigations applicable to this rearrangement are also reported. [ABSTRACT FROM AUTHOR]

The article discusses the characteristics of the cryptophanes, a new source of inspiration for designing molecular cavities. Cryptophanes are considered among the first molecular hosts able to isolate a substrate from neighboring environment, thus defining certain properties related to the inner phase. Since the first synthesis of cryptophane-A in 1981, considerable progress has been made in designing cryptophanes that exhibit selective encapsulation properties toward organic guests.

The article focuses on the significance of the carbon-carbon bonds in organic synthesis. Progress in organic chemistry have clearly established that the development of a reaction is dependent on atom economy and selectivity. The Morita-Baylis-Hillman reaction has appeared as a performant process for the formation of carbon-carbon bonds since it combines two important requirements.