Fabrication of doxorubicin functionalized gold nanorod probes for combined cancer imaging and drug delivery

A novel strategy was utilized to develop a stable probe based on thiolated poly(ethylene glycol) (SH-PEG) and polyacrylic acid (PAA) functionalized gold nanorods (GNRs), following the attachment of an anti-cancer drug, doxorubicin (DOX), to obtain PAA-PEG-GNRs@DOX assemblies. Importantly, the obtained probe as a novel drug-delivery and fluorescent imaging agent for simultaneous imaging of and drug delivery to prostate cancer cells has also been demonstrated. In addition to designing PAA-PEG-GNRs that passively target tumor cells for cancer-fighting drug therapy, GNRs are also regarded as hyperthermia agents for photokilling cancer cells, so that the tumor would be attacked on two fronts simultaneously.     

A new conformer of indium germanate InGe3O7.5(en): conformational polymorphism in germanate family

A new conformer of indium germanate InGe(3)O(7.5)(en) (denoted as δ-type), constructed with the flexible unit of In(2)Ge(6)O(15)N(2) was successfully prepared through a solvothermal method. The crystal data for the δ-type InGe(3)O(7.5)(en) are listed as follows: triclinic, space group P-1 (No.2), a = 7.826(4) ?, b = 8.287(3) ?, c = 9.224(4) ?, α = 71.887(17)°, β = 85.343(18)°, γ = 63.734(12)°, V = 508.64 ?(3), Z = 2. Four relevant conformers of indium germanate are compared with each other. The conformational polymorphism in the germanate family is reported for the first time.     

Through-space charge-transfer emitting biphenyls containing a boryl and an amino group at the o,o'-positions

A new class of organoboron compounds containing a boryl and an amino group at the o,o'-positions of biphenyls display bright through-space intramolecular charge transfer fluorescence owing to the close contact between the boryl and the amino groups. Binding of the fluoride ions results in the remarkable blue shift and color change of the fluorescence, enabling colorimetric and ratiometric fluoride ion sensing.     

Ir(I)-catalyzed enantioselective secondary sp3 C-H bond activation of 2-(alkylamino)pyridines with alkenes

A cationic Ir(I)-tolBINAP complex catalyzed an enantioselective C-C bond formation initiated by secondary sp(3) C-H bond cleavage adjacent to a nitrogen atom. The reaction of 2-(alkylamino)pyridines with various alkenes gave chiral amines in good yields with high enantiomeric excesses.     

Rubesanolides A and B: diterpenoids from Isodon rubescens

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.     

Predicting Fixation Tendencies of the H3N2 Influenza Virus by Free Energy Calculation

Influenza virus evolves to escape from immune system antibodies that bind to it. We used free energy calculations with Einstein crystals as reference states to calculate the difference of antibody binding free energy (ΔΔG) induced by amino acid substitution at each position in epitope B of the H3N2 influenza hemagglutinin, the key target for antibody. A substitution with positive ΔΔG value decreases the antibody binding constant. On average an uncharged to charged amino acid substitution generates the highest ΔΔG values. Also on average, substitutions between small amino acids generate ΔΔG values near to zero. The 21 sites in epitope B have varying expected free energy differences for a random substitution. Historical amino acid substitutions in epitope B for the A/Aichi/2/1968 strain of influenza A show that most fixed and temporarily circulating substitutions generate positive ΔΔG values. We propose that the observed pattern of H3N2 virus evolution is affected by the free energy landscape, the mapping from the free energy landscape to virus fitness landscape, and random genetic drift of the virus. Monte Carlo simulations of virus evolution are presented to support this view.     

Accurate analysis of trace pentachlorophenol in textiles by isotope dilution liquid chromatography-mass spectrometry

A highly accurate method for measuring pentachlorophenol (PCP) concentrations in textile samples was developed. This highly accurate method for the analysis of textile samples is valuable, given the inherent challenges associated with the complexity of the sample matrix. This method can be applied to certify the concentration of pentachlorophenol in textile CRMs. A measurement procedure based on isotope dilution liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed. Samples were pretreated with acid and then with n-hexane. Excellent precision was obtained. The validated concentration ranges for the method were 1.0-50 ng/g, the LOD was 1.0 ng/g, and the LOQ was 5.0 ng/g. The precision of this method is in the range of 0.80-1.40%. The method can trace to mass.     

Circular consecutive choosability of k‐choosable graphs

Let S(r) denote a circle of circumference r. The circular consecutive choosability ch_cc(G) of a graph G is the least real number t such that for any r≥χ_c(G), if each vertex v is assigned a closed interval L(v) of length t on S(r), then there is a circular r‐coloring f of G such that f(v)∈L(v). We investigate, for a graph, the relations between its circular consecutive choosability and choosability. It is proved that for any positive integer k, if a graph G is k‐choosable, then ch_cc(G)?k + 1 ? 1/k; moreover, the bound is sharp for k≥3. For k = 2, it is proved that if G is 2‐choosable then ch_cc(G)?2, while the equality holds if and only if G contains a cycle. In addition, we prove that there exist circular consecutive 2‐choosable graphs which are not 2‐choosable. In particular, it is shown that ch_cc(G) = 2 holds for all cycles and for K_{2, n} with n≥2. On the other hand, we prove that ch_cc(G)>2 holds for many generalized theta graphs. © 2011 Wiley Periodicals, Inc. J Graph Theory 67: 178‐197, 2011     

The penalized Fischer-Burmeister SOC complementarity function

In this paper, we study the properties of the penalized Fischer-Burmeister (FB) second-order cone (SOC) complementarity function. We show that the function possesses similar desirable properties of the FB SOC complementarity function for local convergence; for example, with the function the second-order cone complementarity problem (SOCCP) can be reformulated as a (strongly) semismooth system of equations, and the corresponding nonsmooth Newton method has local quadratic convergence without strict complementarity of solutions. In addition, the penalized FB merit function has bounded level sets under a rather weak condition which can be satisfied by strictly feasible monotone SOCCPs or SOCCPs with the Cartesian R ₀₁-property, although it is not continuously differentiable. Numerical results are included to illustrate the theoretical considerations.     

Hydrogen exchange mass spectrometry of bacteriorhodopsin reveals light-induced changes in the structural dynamics of a biomolecular machine

Many proteins act as molecular machines that are fuelled by a nonthermal energy source. Examples include transmembrane pumps and stator-rotor complexes. These systems undergo cyclic motions (CMs) that are being driven along a well-defined conformational trajectory. Superimposed on these CMs are thermal fluctuations (TFs) that are coupled to stochastic motions of the solvent. Here we explore whether the TFs of a molecular machine are affected by the occurrence of CMs. Bacteriorhodopsin (BR) is a light-driven proton pump that serves as a model system in this study. The function of BR is based on a photocycle that involves trans/cis isomerization of a retinal chromophore, as well as motions of transmembrane helices. Hydrogen/deuterium exchange (HDX) mass spectrometry was used to monitor the TFs of BR, focusing on the monomeric form of the protein. Comparative HDX studies were conducted under illumination and in the dark. The HDX kinetics of BR are dramatically accelerated in the presence of light. The isotope exchange rates and the number of backbone amides involved in EX2 opening transitions increase roughly 2-fold upon illumination. In contrast, light/dark control experiments on retinal-free protein produced no discernible differences. It can be concluded that the extent of TFs in BR strongly depends on photon-driven CMs. The light-induced differences in HDX behavior are ascribed to protein destabilization. Specifically, the thermodynamic stability of the dark-adapted protein is estimated to be 5.5 kJ mol(-1) under the conditions of our work. This value represents the free energy difference between the folded state F and a significantly unfolded conformer U. Illumination reduces the stability of F by 2.2 kJ mol(-1). Mechanical agitation caused by isomerization of the chromophore is transferred to the surrounding protein scaffold, and subsequently, the energy dissipates into the solvent. Light-induced retinal motions therefore act analogously to an internal heat source that promotes the occurrence of TFs. Overall, our data highlight the potential of HDX methods for probing the structural dynamics of molecular machines under "engine on" and "engine off" conditions.