Design of Turn-On Near-Infrared Fluorescent Probes for Highly Sensitive and Selective Monitoring of Biopolymers

Simple, sensitive, and selective detection of specific biopolymers is critical in a broad range of biomedical and technological areas. We present a design of turn-on near-infrared (NIR) fluorescent probes with intrinsically high signal-to-background ratio. The fluorescent signal generation mechanism is based on the aggregation/de-aggregation of phthalocyanine chromophores controlled by selective binding of small-molecule “anchor” groups to a specific binding site of a target biopolymer. As a proof-of-concept, we demonstrate a design of a sensor for EGFR tyrosine kinase—an important target in cancer research. The universality of the fluorescent signal generation mechanism, as well as the dependence of the response selectivity on the choice of the small-molecule “anchor” group, make it possible to use this approach to design reliable turn-on NIR fluorescent sensors for detecting specific protein targets present in the low-nanomolar concentration range.     

Selective Encapsulation and Sequential Release of Guests Within a Self‐Sorting Mixture of Three Tetrahedral Cages

A mixture of two triamines, one diamine, 2‐formylpyridine and a Zn^II salt was found to self‐sort, cleanly producing a mixture of three different tetrahedral cages. Each cage bound one of three guests selectively. These guests could be released in a specific sequence following the addition of 4‐methoxyaniline, which reacted with the cages, opening each in turn and releasing its guest. The system here described thus behaved in an organized way in three distinct contexts: cage formation, guest encapsulation, and guest release. Such behavior could be used in the context of a more complex system, where released guests serve as signals to other chemical actors.     

Quantitative Protein Corona Composition and Dynamics on Carbon Nanotubes in Biological Environments

When nanoparticles enter biological environments, proteins adsorb to form the “protein corona” which alters nanoparticle biodistribution and toxicity. Herein, we measure protein corona formation on DNA-functionalized single-walled carbon nanotubes (ssDNA-SWCNTs), a nanoparticle used widely for sensing and delivery, in blood plasma and cerebrospinal fluid. We characterize corona composition by mass spectrometry, revealing high-abundance corona proteins involved in lipid binding, complement activation, and coagulation. We investigate roles of electrostatic and entropic interactions driving selective corona formation. Lastly, we study real-time protein binding on ssDNA-SWCNTs, obtaining agreement between enriched proteins binding strongly and depleted proteins binding marginally, while highlighting cooperative adsorption mechanisms. Knowledge of protein corona composition, formation mechanisms, and dynamics informs nanoparticle translation from in vitro design to in vivo application.     

Factors Associated With Mathematics Achievement and Participation in Advanced Mathematics Courses: An Examination of Gender Differences From an International Perspective

This paper reports results of an exploratory study examining factors that might be associated with achievement in mathematics and participation in advanced mathematics courses in Canada, Norway, and the United States of America (USA). These factors, which were not directly related to schooling accounted for large degrees of variability, 24% to 39%, in mathematics achievement scores. Confidence in mathematics was the strongest predictor of achievement for students from Canada and Norway, whereas for the students from the USA, parents' highest education level was the highest predictor of achievement. Student home environment related variables were stronger predictors of achievement for females than for males in all three countries. The participation in advanced mathematics courses could be predicted with 72% to 76% accuracy by the same variables. In all of the three countries, the strongest predictors of participation in advanced mathematics courses were students' attitudes toward mathematics. Parents' education level, a socioeconomic related variable, was one of the strongest predictors of participation for Canadian female students and all students from the USA.     

A cotangent bundle slice theorem

This article concerns cotangent-lifted Lie group actions; our goal is to find local and “semi-global” normal forms for these and associated structures. Our main result is a constructive cotangent bundle slice theorem that extends the Hamiltonian slice theorem of Marle [C.-M. Marle, Modèle d'action hamiltonienne d'un groupe de Lie sur une variété symplectique, Rendiconti del Seminario Matematico, Università e Politecnico, Torino 43 (2) (1985) 227-251] and Guillemin and Sternberg [V. Guillemin, S. Sternberg, A normal form for the moment map, in: S. Sternberg (Ed.), Differential Geometric Methods in Mathematical Physics, in: Mathematical Physics Studies, vol. 6, D. Reidel, 1984]. The result applies to all proper cotangent-lifted actions, around points with fully-isotropic momentum values.We also present a “tangent-level” commuting reduction result and use it to characterise the symplectic normal space of any cotangent-lifted action. In two special cases, we arrive at splittings of the symplectic normal space. One of these cases is when the configuration isotropy group is contained in the momentum isotropy group; in this case, our splitting generalises that given for free actions by Montgomery et al. [R. Montgomery, J.E. Marsden, T.S. Ratiu, Gauged Lie-Poisson structures, Cont. Math. AMS 128 (1984) 101-114]. The other case includes all relative equilibria of simple mechanical systems. In both of these special cases, the new splitting leads to a refinement of the so-called reconstruction equations or bundle equations [J.-P. Ortega, Symmetry, reduction, and stability in Hamiltonian systems, PhD thesis, University of California, Santa Cruz, 1998; J.-P. Ortega, T.S. Ratiu, A symplectic slice theorem, Lett. Math. Phys. 59 (1) (2002) 81-93; M. Roberts, C. Wulff, J.S.W. Lamb, Hamiltonian systems near relative equilibria, J. Differential Equations 179 (2) (2002) 562-604]. We also note cotangent-bundle-specific local normal forms for symplectic reduced spaces.     

Gold-mediated C-H bond functionalisation

The transition metal-catalysed direct functionalisation of C-H bonds is an increasingly viable alternative to the multi-step strategies traditionally adopted. The use of powerful and environmentally benign gold(I) and gold(III) catalysts in such transformations has highlighted their remarkable reactivity and led to a significant increase in their utilisation. This tutorial review provides an overview of gold-catalysed C-H functionalisation, looking at transformations which rely on the ability of gold to perform C-H activation, as well as those exploiting its potent π-acidity.     

Study of thioflavin-T immobilized in porous silicon and the effect of different organic vapors on the fluorescence lifetime

Steady-state and time-resolved emission techniques have been employed to study the fluorescence properties of thioflavin-T (ThT) adsorbed on oxidized porous silicon (PSi) surfaces, with an average pore size of ～10 nm. We found that the average fluorescence decay time of ThT, when it is adsorbed on the PSi surface, is rather long, τ(av) = 1.3 ns. We attribute this relatively long emission lifetime to the effect of the immobilization of ThT on the PSi surface, which inhibit the rotation of the aniline with respect to the benzothiazole moieties of ThT. We also measured the fluorescence properties of ThT in PSi samples in equilibrium with vapors of several liquids, such as methanol, acetonitrile, and water. We found that the fluorescence intensity drops by a factor of 10, and the average decay time, measured by a time-correlated single-photon counting technique, decreases by a factor of 3. We explain these results in terms of liquid condensation of the vapors in the PSi pores, which leads to partial dissolution of the ThT molecules in the liquid pools.     

Acetone promoted 1,4-migration of an alkoxycarbonyl group on a syn-1,2-diamine

A 2-protected cis-amino mitosene undergoes an irreversible acetone promoted isomerization and converts to the 1-isomer. Kinetic studies and DFT calculations of the reaction are reported. An organocatalytic mechanism is proposed, involving a covalent intermediate formed by reaction of the mitosene and acetone.     

Separation of (<Emphasis Type="Italic">S</Emphasis>)-(−)-3-Methyl-2-pyrrolidinone as an Inclusion Complex with (<Emphasis Type="Italic">R</Emphasis>)-(+)-4,4′,6,6′-Tetrachloro-2,2′-bis(hydroxydiphenylmethyl)-1,1′-biphenyl Host and its X-ray Structural Study

Abstract By inclusion complexation with the chiral host compound (R)-(+)-4,4′,6,6′-tetrachloro-2,2′-bis(hydroxydiphenylmethyl)-1,1′-biphenyl, racemic 3-methyl-2-pyrrolidinone was resolved and its (S)-(−)-enantiomer was isolated as a 1:1 inclusion complex, which crystallises in the orthorhombic crystal system in the space group P2₁2₁2₁ (a = 14.1163(2) ?, b = 14.7140(3) ?, c = 17.2025(3) ?). By the inclusion complexation, the keto–enol equilibrium of the guest was frozen and the keto-form was isolated in a pure form. By X-ray structural study of the complex, the guest molecule included was elucidated to be the keto-form and its absolute configuration was determined to be (S). Index Abstract By inclusion complexation with (R)-(+)-4,4′,6,6′-tetrachloro-2,2′-bis (hydroxydiphenylmethyl)-biphenyl, racemic 3-methyl-2-pyrrolidinone was resolved and its (S)-(−)-enantiomer isolated and in addition the keto–enol equilibrium of the guest was frozen and the keto-form isolated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chemical composition and antibacterial activity of selected essential oils and some of their main compounds

The chemical composition of essential oils of cabreuva (Myrocarpus fastigiatus Allemao, Fabaceae) from Brazil, cedarwood (Juniperus ashei, Cupressaceae) from Texas, Juniper berries (Juniperus communis L., Cupressaceae) and myrrh (Commiphora myrrha (Nees) Engl., Burseraceae) were analyzed using GC/FID and GC/MS. The antimicrobial activity of these essential oils and some of their main compounds were tested against eleven different strains of Gram-positive and Gram-negative bacteria by using agar diffusion and agar serial dilution methods. Animal and plant pathogens, food poisoning and spoilage bacteria were selected. The volatile oils exhibited considerable inhibitory effects against all tested organisms, except Pseudomonas, using both test methods. Higher activity was observed against Gram-positive strains in comparison with Gram-negative bacteria. Cabreuva oil from Brazil showed similar results, but in comparison with the other oils tested, only when higher concentrations of oil were used.