Synthesis of Biotinylated Galiellalactone Analogues

Two biotinylated derivatives of the fungal metabolite galiellalactone (1) were synthesized in order to facilitate the investigation of the molecular mechanism of action of the galiellalactonoids. Galiellalactone is a STAT3-signaling inhibitor that inhibits growth in vitro as well as in vivo of prostate cancer cells expressing activated STAT3. To provide a suitable point of attachment for biotin, the 8-hydroxymethyl derivative (3) and its 7-phenyl analogue 4 were synthesized by a modified tandem Pd-catalysed carbonylation and intramolecular vinyl allene Diels-Alder procedure previously developed. The two primary alcohols obtained, 3 and 4, were coupled to biotin as the 6-aminohexanoic acid amide, activated as the acid chloride, yielding the derivatives 5 and 6.

Pressurized Hot Water Extraction of Alkaloids in Goldenseal

A quick, efficient and environmentally beneficial approach for the extraction of alkaloids in goldenseal based on pressurized hot water extraction (PHWE) is presented. PHWE was evaluated following the extraction of hydrastine and berberine which are the two main alkaloids of goldenseal. The effects of temperature and other parameters on extraction yields were monitored by high performance liquid chromatography coupled to diode array detector (HPLC-DAD). The extraction yields were compared to those achieved through reflux and ultrasonic extraction methods. PHWE employed hot water at an optimal temperature of 140℃, a pressure of 50 bars and flow rate of 1 mL.min-1 for extraction experiments conducted in the dynamic mode. Both PHWE and conventional methods achieved comparable extraction yields. Reflux and ultrasonic extractions had procedures that were slower (over 6 h) and employed large quantities (200 mL) of organic solvents. The PHWE method was simple and relatively fast as extraction was achieved in 15 min. At 95% confidence level (n = 3), reflux and ultrasonic methods recorded extraction yields that were not significantly different from that of PHWE. Moreover, PHWE employed a more readily available “green” solvent, (water) to achieve comparable results to those of conventional methods which utilized organic solvents. The percentage relative standard deviations (%RSD) for the extraction yields were less than 3% in all cases indicating the high reproducibility of the method. However, when using PHWE to extract thermally labile analytes like alkaloids, degradation effects also occurred. Increasing the temperatures certainly achieved higher extraction yields but also led to degradation of these thermally labile compounds indicating a necessity for optimization.

Straight and kinked InAs nanowire growth observed in situ by transmission electron microscopy

Live observations of growing nanowires using in situ transmission electron microscopy （TEM） is becoming an increasingly important tool for understanding the dynamic processes occurring during nanowire growth. Here we present observations of growing InAs nanowires, which constitute the first reported in situ growth of a In-V compound in a transmission electron microscope. Real time observations of events taking place over longer growth lengths were possible due to the high growth rates of up to I nm/s that were achieved. Straight growth （mainly in 〈111〉B directions） was observed at uniform temperature and partial pressure while intentional fluctuations in these conditions caused the nanowires to form kinks and change growth direction. The mechanisms behind the kinking are discussed in detail. In situ observations of nanowire kinking has previously only been reported for nonpolar diamond structure type materials （such as Si）, but here we present results for a polar zinc blende structure （InAs）. In this study a closed cell with electron and X-ray transparent a-SiN windows was used in a conventional high resolution transmission electron microscope, enabling high resolution imaging and compositional analysis in between the growth periods.

Compressively-strained GaSb nanowires with core-shell heterostructures

GaSb-based nanowires in a gate-all-around geometry are good candidates for binary p-type transistors,however they require the introduction of compressive strain to enhance the transport properties.Here,we for the first time demonstrate epitaxial GaSb-GaASxSb1-x core-shell nanowires with a compressively strained core.Both axial and hydrostatic strain in GaSb core have been measured by X-ray diffraction(XRD)and Raman scattering,respectively.The optimal sample,almost without plastic relaxation,has an axial strain of-0.88%and a hydrostatic strain of-1.46%,leading to a noticeable effect where the light hole band is calculated to be 33.4 meV above the heavy hole band at the T-point.This valence band feature offers more light holes to contribute the transport process,and thus may provide enhanced hole mobility by reducing both the interband scattering and the hole effective mass.Our results show that lattice-mismatched epitaxial core-shell heterostructures of high quality can also be realized in the promising yet demanding GaSb-based system.