Preparation of Amphiphilic Janus Nanoparticles in Studying their Unique Chiroptical Properties and Enantiomeric Selectivity

Janus nanoparticles have been an interesting topic due to their dual functionality by the segregation of surface ligands, whereas chiral nanostructures have been attracting extensive interest in recent years primarily because of the unique materials properties that can be exploited for diverse applications. My research focus was based on chirality originated from the structural asymmetry of Janus nanoparticles and study the enantiomeric selectivity of these nanoparticles.Gold Janus nanoparticles functionalized with hexanethiolates and 3-mercapto-1,2-propanediol segregated on the two hemispheres, self-assembled into vesicle-like, hollow nanostructures in both water or organic media, and exhibited apparent plasmonic circular dichroism (PCD) absorption in the visible range. The PCD signals were found to become intensified with increasing coverage of the 3-mercapto-1,2-propanediol ligands on the nanoparticle surface, which was attributed to the dipolar property of the structurally asymmetrical Janus nanoparticles. Theoretical simulations based on first principles calculations showed that when the nanoparticle dipoles self-assembled onto the surface of a hollow sphere, a vertex was formed which gave rise to the unique chiral characteristics. The resulting chiral nanoparticle vesicles could be exploited for the separation of optical enantiomers, as manifested in the selective identification and separation of D-alanine from the L-isomer.The enantiomeric selectivity of Janus nanoparticles protected by hexanethiolates and 3-mercapto-1,2-propanediol was further studied using D,L-cysteine as the molecular probe. Experimental results demonstrate that D-cysteine was the preferred enantiomers entrapped within the nanoparticle emulsions, where the ensuing ligand exchange reaction was initially confined to the hydrophilic face of the Janus nanoparticles. This suggests that with a deliberate control of the reaction time, chiral Janus nanoparticles could be readily prepared by ligand exchange reactions even with a racemic mixture of ligands.In a different study, gold Janus nanoparticles functionalized with poly(ethylene glycol) (PEG) ligands hexanethiolates was synthesized. Due to specific interaction of PEG with alkali metal ions, the Janus nanoparticles exhibited marked conformational changes forming organized ensembles in the presence of Na+ and K+, as manifested in dynamic light scattering, UV-vis absorption and TEM measurements, whereas no apparent variation was observed with bulk-exchange nanoparticles where the two types of capping ligands were homogeneously mixed on the nanoparticle surface or nanoparticles capped with the PEG ligands alone. The ion complexation was further probed in NMR measurements. Results from this study indicate that select doping of alkali metal ions into PEG-functionalized nanoparticles may be used for controlled assembly of the Janus nanoparticles.In addition to Janus nanoparticles with segregated ligands, Janus Cu1.75S-Au nanostructure was synthesized using Langmuir-Blodgett method at room temperature through ion exchange of gold atoms onto Cu1.75S nanoparticles. Positive chiroptical response arose around 600 nm closed to gold SPR absorption region, whereas the Cu1.75S nanoparticles shown no chiroptical response. Upon etching away the Cu1.75S, the deposited gold nanostructure shown weak positive chiroptical response at the same region, indicating chiral origin was due to the asymmetric deposition of gold atoms. In addition, the chiroptical signal of asymmetric gold nanostructure was enhanced upon the formation of Cu1.75S-Au hybrid nanostructure

A mutation in the interferon regulatory element of HBV may influence the response of interferon treatment in chronic hepatitis B patients

<p>Abstract</p> <p>Background</p> <p>A functional interferon regulatory element (IRE) has been found in the EnhI/X promoter region of hepatitis B virus (HBV) genome. The purpose of this study is to compare the gene order of responder and non-responder to interferon therapy in patients with chronic hepatitis B (CHB), so as to evaluate the relationship between IRE mutation and the response to interferon treatment for CHB patients.</p> <p>Results</p> <p>Synthetic therapeutic effect is divided into complete response (CR), partial response (PR) and non-response (NR). Among the 62 cases included in this study, 40 cases (64.5%) were in the response group (CR and PR) and 22 (35.5%) cases were in the NR group. Wild type sequence of HBV IRE TTTCACTTTC were found in 35 cases (56.5%), and five different IRE gene sequences. included TTTtACTTTC, TTTCAtTTTC, TTTtAtTTTC, TTTtACTTTt and cTTtACcTTC, were found in 22 cases (35.5%), 1 case (1.6%), 1 case (1.6%), 2 cases (3.2%) and 1 case (1.6%) respectively. There were 41.9%cases (26/62) with forth base C→T mutation, consisted of 32.5% (13/40) cases in response group and 59.1% (13/22) cases in NR group. Among the 35 cases with IRE sequences, there were 67.5% (27/40) cases in response group and 36.4% (8/22) in NR group, and the difference in IRE sequences between two groups was statistic significantly (P = 0.027). The result suggested that there is likely relationship between the forth base mutation (C→T) of IRE region and the response of HBV to Interferon therapy, and this mutation may partially decrease the inhibition effect of interferon on HBV.</p> <p>Conclusion</p> <p>The forth base C→T mutation in IRE element of HBV may partially influence the response of Interferon treatment in CHB patients.</p

Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media.

Hydrogen evolution reaction is an important process in electrochemical energy technologies. Herein, ruthenium and nitrogen codoped carbon nanowires are prepared as effective hydrogen evolution catalysts. The catalytic performance is markedly better than that of commercial platinum catalyst, with an overpotential of only -12 mV to reach the current density of 10 mV cm-2 in 1 M KOH and -47 mV in 0.1 M KOH. Comparisons with control experiments suggest that the remarkable activity is mainly ascribed to individual ruthenium atoms embedded within the carbon matrix, with minimal contributions from ruthenium nanoparticles. Consistent results are obtained in first-principles calculations, where RuCxNy moieties are found to show a much lower hydrogen binding energy than ruthenium nanoparticles, and a lower kinetic barrier for water dissociation than platinum. Among these, RuC2N2 stands out as the most active catalytic center, where both ruthenium and adjacent carbon atoms are the possible active sites

Plasmoid ejection and secondary current sheet generation from magnetic reconnection in laser-plasma interaction

Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson {\it et al.} [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fan-like electron outflow region including three well-collimated electron jets appears. The ($>1$ MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS