High-level theoretical study of the evolution of abundances and interconversion of glycine conformers

The relative conformer energies of glycine are evaluated by using a focal point analysis expressed as（HF→MP2→MP3→CCSD→CCSD（T））.The conformer abundances at various temperatures（298–500 K） are calculated based on the relative energies and Boltzmann statistical thermostatistical analysis with and without considering internal hindered rotations.A comparison between the available Raman spectrum and the electron momentum spectrum confirms that the influence of rigid-rotor hindered rotation on the conformational proportions of glycine is considerable,especially for the IIIp structure.The conformational interconversions are discussed.It is found that with increasing temperature,the mole fraction of IIn keeps constant and Ip structure can convert into IVn and IIIp,leading to the decrease in the weight of Ip and the increase in the weights of IVn and IIIp conformers,which is in accordance with experimental observations.

Understanding the Conformational Interconversions of a Polymer Chain in a Liquid Environment at the Single-molecule Level

The conformational interconversions of polymer chains have been of great interest as a basic scientific issue.Single-molecule force spectroscopy(SMFS)is a powerful tool for molecular manipulation,which enables experimental studies on the single-chain behaviors of polymers.The SMFS results show that an individual polymer chain in a liquid environment may have similar properties to an ideal chain,which contradicts the traditional theoretical view.Herein,by taking into account the collisions of solvent molecules,the conformational interconversions of a single polymer chain in a liquid environment have been analyzed.The conformational interconversion frequency of a carbon-carbon bond of an alkane chain can be estimated by establishing the relationship between the internal rotation barriers of small molecules(monomers)and the corresponding macromolecules.Since the time scale of conformational interconversions of the polymer backbone is much shorter than that of SMFS experiments,most polymers with C-C backbones behave as ideal chains in liquid environments.

Electro-selective interconversion of living cationic and radical polymerizations

Orchestrating conflicting polymerization mechanisms in a single polymerization process through one external stimulus is a prerequisite to achieve in-situ selective synthesis of different monomers. Here we report an electrochemically controlled mechanism transformation that enables selective activation of living cationic or radical polymerization via an alternating voltage and dual electrocatalysts. Using identical mixed-monomer condition, a variety of desired block copolymer structures, including diblock, multiblock, random, and tapered copolymers can be obtained by simply varying the periods or phases of the alternating potential. Moreover, merging this electro-interconverted polymerization with a flow-chemistry technique can streamline preparation of functional polymer materials with complex multiblock structure. This study would offer a new vision on large-scale electrochemical synthesis of sequence-defined polymers.

二丙酮果糖-3-酮肟及苯甲酰腙的合成

本文通过1,2:4,5-二-O-异亚丙基-β-D-赤式-2,3-己二酮-2,6-吡喃糖(1)分别与羟胺和苯甲酰肼缩合,得到了肟(2)和腙(3)。由元素分析,IR,~1H,^(13)C-NMR谱证实了其结构并说明了2的构型及3的互变异构体。

Determination of Inorganic Antimony Species Conversions during Its Speciation Analysis in Soil Using Isotope Dilution Techniques

A new method was developed in this work to account for inorganic Sb species interconversion during soil sample preparation and subsequent separation steps. The Sb(III) and Sb(V) concentrations at each investigated step in the analytical procedure were determined using species specific spikes (121Sb(III) with 81.18% and 123Sb(V) with 74.04% enrichment). The spiking of these enriched isotopes species solutions was done separately before soil sample extraction and before HPLC separation. Simply by subtracting the final concentration of each species done by on-line isotope dilution (ID) from its concentration at different stages of the analytical procedure done by species specific ID, the influence of each step on species transformation can be estimated. After optimization, the extraction procedure for inorganic Sb species 6% Sb(III) (1.3 RSD, n = 3) and 43.2% Sb(V) (2.9% RSD, n = 3) as percent of total Sb were detected in the examined soil sample using online ID. Using the above described methodology we found that there was no reduction of Sb(V) to Sb(III) during sample preparation or species separation. While about 9.3% of extractable Sb (4.6% of total) was converted from Sb(III) to Sb(V) during the extraction step, no conversion during HPLC separation step was observed. By compensating for Sb(III) transformation during the sample preparation step;the extractable Sb(III) and Sb(V) as percent of total Sb yielded 10.6% and 38.7%, respectively.

Alternative models of cancer stem cells: The stemness phenotype model, 10 years later

The classical cancer stem cell(CSCs)theory proposed the existence of a rare but constant subpopulation of CSCs.In this model cancer cells are organized hierarchically and are responsible for tumor resistance and tumor relapse.Thus,eliminating CSCs will eventually lead to cure of cancer.This simplistic model has been challenged by experimental data.In 2010 we proposed a novel and controversial alternative model of CSC biology(the Stemness Phenotype Model,SPM).The SPM proposed a non-hierarchical model of cancer biology in which there is no specific subpopulation of CSCs in tumors.Instead,cancer cells are highly plastic in term of stemness and CSCs and non-CSCs can interconvert into each other depending on the microenvironment.This model predicts the existence of cancer cells ranging from a pure CSC phenotype to pure non-CSC phenotype and that survival of a single cell can originate a new tumor.During the past 10 years,a plethora of experimental evidence in a variety of cancer types has shown that cancer cells are indeed extremely plastic and able to interconvert into cells with different stemness phenotype.In this review we will(1)briefly describe the cumulative evidence from our laboratory and others supporting the SPM;(2)the implications of the SPM in translational oncology;and(3)discuss potential strategies to develop more effective therapeutic regimens for cancer treatment.

Protective Effects of Sepia Ink Melanin on Hepatic Tissue in Streptozotocin-Induced Diabetic Mice

Diabetes mellitus(DM)has emerged as a serious public health concern,due to the high morbidity and mortality resulted from its complications,such as diabetic nephropathy,diabetic cardiovascular complication,and diabetic neuropathy,etc.In this study,we investigated the beneficial effects of sepia ink melanin(SIM)on hyperglycaemia and the restoration of diabetic symptoms in streptozotocin(STZ)-induced diabetic model mice.At first,the normal experimental mice were performed with intraperitoneal injection of STZ(40 mg(kg BW)^(−1))(BW,body weight)to attain diabetes and then were treated with different concentrations of SIM(120,240 and 480 mg(kg BW)^(−1))for four weeks.After treatment,significant decrease in gluconeogenesis were determined,accompanied by a notable increase in both glycolysis and oxidative enzyme activities in SIM-treated groups,such as liver marker enzymes in the serum and key antioxidant enzymes in liver.qPCR results revealed the transcriptional alterations in SIM-treated groups.SIM exposure increased the expression levels of several genes related to insulin transduction and PI3K/Akt pathway,including PI3K,Akt,Irs-2,and InsR.Meanwhile,expression levels of Dicarbonyl/l-xylulose reductase(Dcxr)and UDP-glucose dehydrogenase(Ugdh),which are in-volved in pentose-glucuronate interconversion pathway,were also elevated in SIM-treated groups.Furthermore,histological observation results indicated that nuclear deformation and organelle dissolution were improved,thus could enhance the liver function.These results demonstrated that SIM can be effective in ameliorating diabetic symptoms and improving disease management for diabetic patients.

Complicated evolutionary patterns of microRNAs in vertebrates

MicroRNAs (miRNAs) are a class of ～22 nt long endogenous non-coding RNAs that play important regulatory roles in diverse organisms. Up to now, little is known about the evolutionary properties of these crucial regulators. Most miRNAs were thought to be phylogenetically conserved, but recently, a number of poorly-conserved miRNAs have been reported and miRNA innovation is shown to be an ongoing process. In this work, through the characterization of an miRNA super family, we studied the evolutionary patterns of miRNAs in vertebrates. Recently generated miRNAs seem to evolve rapidly during a certain period following their emergence. Multiple lineage-specific expansions were observed. Homolgous premiRNAs may produce mature products from the opposite stem arms following tandem duplications, which may have important contribution to miRNA innovation. Our observations of miRNAs' complicated evolutionary patterns support the notion that these key regulatory molecules may play very active roles in evolution.

Recent advancements in halide perovskite nanomaterials and their optoelectronic applications

Lead halide perovskite nanomaterials are among the forefront of developing materials for energy harvesting and light-emitting applications.Their unique defect tolerance,high photoluminescent quantum yields,and vast synthetic tunability make them attractive for many optoelectronic applications.In this review article,the broad synthetic toolbox of these materials is discussed,including how synthetic conditions can tune the optical properties and dimensionality of the resulting perovskite nanomaterial.Additionally,we discuss the brief history,current state,and bright future of these materials,in tune with their optoelectronic applications,namely in light-emitting diodes,lasing,photovoltaics,photon interconversion applications,and in photodetectors.

Transformations of multilevel coherent states under coherence-preserving operations

Quantum coherence,emerging from the"superposition"of quantum states,is widely used in various information processing tasks.Recently,the resource theory of multilevel quantum coherence is attracting substantial attention.In this paper,we mainly study the transformations of resource pure states via free operations in the theoretical framework for multilevel coherence.We prove that any two multilevel coherent resource pure states can be interconverted with a nonzero probability via a completely positive and trace non-increasing k-coherence-preserving map.Meanwhile,we present the condition of the interconversions of two multilevel coherent resource pure states under k-coherence-preserving operations.In addition,we obtain that in the resource-theoretic framework of multilevel coherence,no resource state is isolated,that is,given a multilevel coherent pure state|ψ>,there exists another multilevel coherent pure state|Φ>and a k-coherence-preserving operation∧k,such that∧k(|Φ>)=|ψ>.

Aggregation of Surface Structure Induced Photoluminescence Enhancement in Atomically Precise Nanoclusters

Although intermolecular aggregation-induced emission(AIE)has been extensively studied in nanocluster science,it remains challenging to activate AIE via intracluster aggregation(i.e.,the aggregation at the single-molecular level).Here,an intracluster AIE system based on the Pt_(1)Ag_(24)(SR)18 nanocluster has been established.Specifically,triggered by the addition of free thiol ligands,the Ag_(2)(SR)_(3)surface motif structures of Pt_(1)Ag_(24)(SR)18 are aggregated to nanocluster poles.