Growth of uniformly aligned ZnO nanowire heterojunction arrays on GaN, AlN, and Al0.5Ga0.5N substrates

Vertically aligned single-crystal ZnO nanorods have been successfully fabricated on semiconducting GaN, Al0.5Ga0.5N, and AlN substrates through a vapor-liquid-solid process. Near-perfect alignment was observed for all substrates without lateral growth. Room-temperature photoluminescence measurements revealed a strong luminescence peak at approximately 378 nm. This work demonstrates the possibility of growing heterojunction arrays of ZnO nanorods on AlxGa1-xN, which has a tunable band gap from 3.44 to 6.20 eV by changing the Al composition from 0 to 1, and opens a new channel for building vertically aligned heterojunction device arrays with tunable optical properties and the realization of a new class of nanoheterojunction devices.     

New efficient synthesis of resorcinylic macrolides via ynolides: establishment of cycloproparadicicol as synthetically feasible preclinical anticancer agent based on Hsp90 as the target

A program currently ongoing in our laboratory envisions natural macrolide radicicol-based inhibitors targeting the molecular chaperone Hsp90. Such inhibitors can be potential anticancer agents due to their ability to induce the breakdown of a variety of oncogenic proteins. In this account, we first concern ourselves with a vastly important total synthesis of such an inhibitor. We accomplished this via a new approach, which we term the "ynolide method", directed to the synthesis of resorcinylic macrolides, including cycloproparadicicol and aigialomycin D. The key features of the syntheses involve cobalt-complexation-promoted ring-closing metathesis (RCM) to generate ynolides, followed by Diels-Alder reaction with dimedone-derived bis-siloxy dienes to elaborate the benzo system. A number of interesting analogues were synthesized using this protocol. They were evaluated for their inhibitory activity against the growth of breast cancer cell line, MCF-7. The potency of their cytotoxicity was found to be consistent with their ability to degrade the oncogenic protein, Her2. From these assays, cycloproparadicicol was identified as a most promising candidate for further development.     

Subfemtomole detection of small molecules with microsphere sensors

We investigated the feasibility of using a silica microsphere sensor for detection of small molecules. Using the silica molecules (60 Da) at the sphere's surface as a model system, we measured the spectral shifts in the whispering-gallery modes (WGMs) when the sphere size was decreased by a hydrofluoric acid (HF) solution. The results demonstrate that our sensor is capable of detecting a 4 pm (or 0.01 layer of silica) decrease in sphere radius, corresponding to a change of 0.4 fmol silica molecule. These results suggest that small molecules can be detected in trace quantities at the surface of an optical microsphere sensor.     

Trypsin catalyzed 16O-to-18O exchange for comparative proteomics: tandem mass spectrometry comparison using MALDI-TOF,ESI-QTOF,and ESI-ion trap mass spectrometers

Quantitative or comparative proteome analysis was initially performed with 2-dimensional gel electrophoresis with the inherent disadvantages of being biased towards certain proteins and being labor intensive. Alternative mass spectrometry-based approaches in conjunction with gel-free protein/peptide separation have been developed in recent years using various stable isotope labeling techniques. Common to all these techniques is the incorporation, biosynthetically or chemically, of a labeling moiety having either a natural isotope distribution of hydrogen, carbon, oxygen, or nitrogen (light form) or being enriched with heavy isotopes like deuterium, (13)C, (18)O, or (15)N, respectively. By mixing equal amounts of a control sample possessing for instance the light form of the label with a heavy-labeled case sample, differentially labeled peptides are detected by mass spectrometric methods and their intensities serve as a means for direct relative protein quantification. While each of the different labeling methods has its advantages and disadvantages, the endoprotease (16)O-to-(18)O catalyzed oxygen exchange at the C-terminal carboxylic acid is extremely promising because of the specificity assured by the enzymatic reaction and the labeling of essentially every protease-derived peptide. We show here that this methodology is applicable to complex biological samples such as a subfraction of human plasma. Furthermore, despite the relatively small mass difference of 4 Da between the two labeled forms, corresponding to the exchange of two oxygen atoms by two (18)O isotopes, it is possible to quantify differentially labeled proteins on an ion trap mass spectrometer with a mass resolution of about 2000 in automated data dependent LC-MS/MS acquisition mode. Post column sample deposition on a MALDI target parallel to on-line ESI-MS/MS enables the analysis of the same compounds by means of ESI- and MALDI-MS/MS. This has the potential to increase the confidence in the quantification results as well as to increase the sequence coverage of potentially interesting proteins by complementary peptide ionization techniques. Additionally the paired y-ion signals in tandem mass spectra of (16)O/(18)O-labeled peptide pairs provide a means to confirm automatic protein identification results or even to assist de novo sequencing of yet unknown proteins.     

The adsorption and decomposition of methanol on the Rh(100) surface

The adsorption and decomposition of methanol on the Rh(100) surface have been studied using high-resolution electron energy loss spectroscopy and thermal desorption mass spectrometry. Below 200 K, methanol is molecularly adsorbed and bonds to the surface via the oxygen atom. At 200–220 K, a saturated methanol layer undergoes two competing reactions: desorption and OH bond cleavage to form an O-bonded methoxy species. The methoxy species is stable to approximately 250 K. Between 250 and 320 K, a fraction of the methoxy species decomposes to form coadsorbed CO and hydrogen adatoms while the remainder recombines with hydrogen adatoms to desorb as molecular methanol. The hydrogen adatoms remaining on the surface desorb as H₂ between 270 and 400 K, and the CO desorbs between 450 and 550 K. Following a saturation exposure, approximately 0.2 monolayers of methanol decompose to eventually yield CO and H₂ as desorption products. These results are compared to the chemistry of methanol on other metal surfaces.     

Endpoint Estimates for Hardy Operator＇s Conjugate Operator with Power Weight on n-Dimensional Space

In this paper, we establish two integral inequalities for Hardy operator＇s conjugate operator at the endpoint on n-dimensional space. The operator Hn is bounded from Lxα1 （Gn） to Lxβq （Gn） with the bound explicitly worked out and the similar result holds for Hn＊.     

Imaging Sequences for Hyperpolarized Solids

Hyperpolarization is one of the approaches to enhance Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) signal by increasing the population difference between the nuclear spin states. Imaging hyperpolarized solids opens up extensive possibilities, yet is challenging to perform. The highly populated state is normally not replenishable to the initial polarization level by spin-lattice relaxation, which regular MRI sequences rely on. This makes it necessary to carefully “budget” the polarization to optimize the image quality. In this paper, we present a theoretical framework to address such challenge under the assumption of either variable flip angles or a constant flip angle. In addition, we analyze the gradient arrangement to perform fast imaging to overcome intrinsic short decoherence in solids. Hyperpolarized diamonds imaging is demonstrated as a prototypical platform to test the theory.     

Secondary metabolites from Andrographis paniculata

Two new flavonoid glycosides, 5-hydroxy-7,8-dimethoxy (2R)-flavanone-5-O-beta-D-glucopyranoside (1) and 5-hydroxy-7,8,2',5'-tetramethoxy-flavone-5-O-beta-D-glucopyranoside (2), and a new diterpenoid, andrographic acid (3), along with andrographidine A (4) were isolated from Andrographis paniculata, and their structures were determined on the basis of physicochemical and spectroscopic analysis. Compound 3 was evaluated for cytotoxicity to KB cells along with andrographolide, isoandrographolide, neoandrographolide and 14-deoxy-11,12-didehydroandrographolide obtained from A. paniculata in the present study. Cytotoxicity was observed for andrographolide and isoandrographolide with ED50 values of 6.5 and 5.1 microg/ml, respectively.