Functionalization of AlN surface and effect of spacer density on Escherichia coli pili-antibody molecular recognition

The immobilization of antibodies to sensor surfaces is critical in biochemical sensor development. In this study, Jeffamine spacers were employed to tether Escherichia coli K99 pilus antibody to AlN/sapphire surfaces which may allow the antibody to freely reorient and potentially improving the antigen capture efficiency. Spacer density was one of the key parameters to be optimized in studying its effect on the immobilization of antibody. The spacer density was controlled by functionalizing AlN/sapphire surfaces with a mixed (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and trichloro(1H,1H,2H,2H-perfluoroctyl)silane (FAS) self-assembled monolayer (SAM) through a step-wise method. Contact angle measurement and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface coverage of GPTMS and surface chemical composition. Compared to spacer fully covered samples, the capture efficiency was improved by 28% with optimal Jeffamine ED 600 spacer density, which depends on the spacer properties such as the number of monomer units and its size.     

Temperature dependence of electronic coupling through oligo-p-phenyleneethynylene bridges

A series of donor-bridge-acceptor (D-B-A) systems with varying donor-acceptor distances has been studied with respect to the temperature dependence of the triplet excitation energy transfer (TEET) rates. The donor and acceptor, zinc(II) and free-base porphyrin, respectively, were separated by oligo-p-phenyleneethynylene (OPE) bridges, where the number of phenyleneethynylene groups was varied between two and five, giving rise to edge-to-edge separations ranging between 12.7 and 33.4 A. The study was performed in 2-MTHF between room temperature and 80 K. It was found that the distance dependence was exponential, in line with the McConnell model, and the attenuation factor, beta, was temperature dependent. The experimentally determined temperature dependence of beta was evaluated by using a previously derived model for the conformational dependence of the electronic coupling based on results from extensive quantum chemical, DFT and time-dependent DFT (TD-DFT), calculations. Two regimes in the temperature interval could be identified: one high-temperature, low-viscosity regime, and one low-temperature, high-viscosity regime. In the first regime, the temperature dependence of beta was, according to the model, well described by a Boltzmann conformational distribution. In the latter, the molecular motions that govern the electronic coupling are slowed down to the same order of magnitude as the TEET rates. This, in effect, leads to a distortion of the conformational distribution. In the high-temperature regime the model could reproduce the temperature dependence of beta, and the extracted rotational barrier between two neighboring phenyl units of the bridge structure, E(i)=1.1 kJ mol(-1), was in line with previous experimental and theoretical studies. After inclusion of parameters that take the viscosity of the medium into account, successful modeling of the experimentally observed temperature dependence of the distance dependence was achieved over the whole temperature interval.     

Hopeahainol A: an acetylcholinesterase inhibitor from Hopea hainanensis

A phytochemical study of Hopea hainanensis has led to the isolation of three new polyphenols and one known compound. The most important of these compounds are hopeahainols A (2) and B (3), which contain an unprecedented carbon skeleton. The structures were elucidated by analysis of the spectroscopic data including single-crystal X-ray spectroscopy and computational methods. Hopeahainol A was an acetylcholinesterase inhibitor with an IC50 value of 4.33 microM, which is comparable to that of huperzine A, a presently prescribed drug for the treatment of Alzheimer, while other similar structures were inactive. This observation was complemented by a 3D interaction model of the inhibitor with active sites.     

Metabonomics investigation of human urine after ingestion of green tea with gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry and (1)H NMR spectroscopy

A method using gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and (1)H NMR with pattern recognition tools such as principle components analysis (PCA) was used to study the human urinary metabolic profiles after the intake of green tea. From the normalized peak areas obtained from GC/MS and LC/MS and peak heights from (1)H NMR, statistical analyses were used in the identification of potential biomarkers. Metabolic profiling by GC/MS provided a different set of quantitative signatures of metabolites that can be used to characterize the molecular changes in human urine samples. A comparison of normalized metabonomics data for selected metabolites in human urine samples in the presence of potential overlapping peaks after tea ingestion from LC/MS and (1)H NMR showed the reliability of the current approach and method of normalization. The close agreements of LC/MS with (1)H NMR data showed that the effects of ion suppression in LC/MS for early eluting metabolites were not significant. Concurrently, the specificity of detecting the stated metabolites by (1)H NMR and LC/MS was demonstrated. Our data showed that a number of metabolites involved in glucose metabolism, citric acid cycle and amino acid metabolism were affected immediately after the intake of green tea. The proposed approach provided a more comprehensive picture of the metabolic changes after intake of green tea in human urine. The multiple analytical approach together with pattern recognition tools is a useful platform to study metabolic profiles after ingestion of botanicals and medicinal plants.     

Infrared vacuum-ultraviolet laser pulsed field ionization-photoelectron study of CH3Br+ (X(2)E(3/2))

By preparing methyl bromide (CH3Br) in selected rotational levels of the CH3Br(X(1)A1; v1 = 1) state with infrared (IR) laser excitation prior to vacuum-ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) measurements, we have observed rotationally resolved photoionization transitions to the CH3Br(+)(X(2)E(3/2); v1(+) = 1) state, where v1 and v1(+) are the symmetric C-H stretching vibrational mode for the neutral and cation, respectively. The VUV-PFI-PE origin band for CH3Br(+)(X(2)E(3/2)) has also been measured. The simulation of these IR-VUV-PFI-PE and VUV-PFI-PE spectra have allowed the determination of the v1(+) vibrational frequency (2901.8 +/- 0.5 cm(-1)) and the ionization energies of the origin band (85 028.3 +/- 0.5 cm(-1)) and the v1(+) = 1 <-- v1 = 1 band (84 957.9 +/- 0.5 cm(-1)).     

Site specific self-cleavage of certain assemblies of G-quadruplex

It is demonstrated that certain structural assemblies of G-quadruplex are capable of performing selfcleaving actions in a site specific fashion.     

Inter versus intra-molecular photoinduced charge separation in solid films of donor-acceptor molecules

We report on photoinduced charge separation in solid films of two perylene diimides; intramolecular charge separation and recombination is correlated with a reduction in the yield of long-lived, intermolecular charge-separated species.     

Two highly-connected, chiral, porous coordination polymers featuring novel heptanuclear metal carboxylate clusters

Two novel (3,12)-connected, chiral porous coordination polymers featuring 3D intersecting pore structures, selective sorption and solvothermal resistance properties are constructed by linking 3-connected benzene-1,3,5-tribenzoic acid with two types of 12-connected heptanuclear metal carboxylate clusters.     

Synthesis and spectral studies of organotin(IV) 4-amino-3-alkyl-1,2,4-triazole-5-thionates: in vitro antimicrobial activity

Some di- and triorganotin(IV) triazolates of general formula, R(4-n)SnLn (where n=2; R=Me, n-Bu and Ph; n=1; R=Me, n-Pr, n-Bu and Ph and HL=4-amino-3-methyl-1,2,4-triazole-5-thiol (HL-1); and 4-amino-3-ethyl-1,2,4-triazole-5-thiol (HL-2)) were synthesized by the reaction of R(4-n)SnCln with sodium salt of HL-1 and HL-2. The bonding and coordination behavior in these derivatives have been discussed on the basis of IR and 119Sn M?ssbauer spectroscopic studies in the solid state. Their coordination behavior in solution is discussed by multinuclear (1H, 13C and 119Sn) NMR spectral studies. The IR and 119Sn M?ssbauer spectroscopic studies indicate that the ligands, HL-1 and HL-2 act as a monoanionic bidentate ligand, coordinating through Sexo- and Nring. The distorted skew trapezoidal-bipyramidal and distorted trigonal bipyramidal geometries have been proposed for R2SnL2 and R3SnL, respectively, in the solid state. In vitro antimicrobial screening of some of the newly synthesized derivatives and of some di- and triorganotin(IV) derivatives of 3-amino-1,2,4-triazole-5-thiol (HL-3) and 5-amino-3H-1,3,4-thiadiazole-2-thiol (HL-4) along with two standard drugs such as fluconazole and ciprofloxacin have been carried out against the bacteria, viz. Staphylococcus aureus and Escherichia coli, and against some fungi, viz. Aspergillus fumigatus, Candida albicans, Candida albicans (ATCC 10231), Candida krusei (GO3) and Candida glabrata (HO5) by the filter paper disc method. The studied organotin(IV) compounds show mild antifungal activity as compared to that of fluconazole, however, they show almost insignificant activity against the studied Gram-positive (Staphylococcus aureas) and Gram-negative (Escherichia coli) bacteria as compared to that of standard drug, ciprofloxacin.     

Preemptive multiprocessor order scheduling to minimize total weighted flowtime

Consider m identical machines in parallel, each of which can produce k different product types. There is no setup cost when the machines switch from producing one product type to another. There are n orders each of which requests various quantities of the different product types. All orders are available for processing at time t = 0, and preemption is allowed. Order i has a weight w_i and its completion time is the time when its last requested product type finishes. Our goal is to find a preemptive schedule such that the total weighted completion time ∑_wiCi$\sum w_i{C}_i$ is minimized. We show that this problem is NP-hard even when all jobs have identical weights and there are only two machines. Motivated by the computational complexity of the problem, we propose a simple heuristic and show that it obeys a worst-case bound of 2 − 1/m. Finally, empirical studies show that our heuristic performs very well when compared with a lower bound of the optimal cost.