Chemical synthesis of nanocrystalline ZrO_2-SnO_2 composite powders

ZrO_2-SnO_2 composite nanoparticles were prepared by heating the hydrateprecursors synthesized by the chemical co-precipitation reaction of ZrOCl_2 and SnCl_4. Theprecursors were examined by differential thermal analysis (DTA) and thermogravimetric analysis(TGA). The composite powder was characterized using X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and desorption isotherm (Barrett-Joyner-Halenda method). The average crystal sizeof the nanoparticle ranges from 15 to 30 nm for the sample containing 5%-25% ZrO_2 (mass fraction).Most of the pores in the ZrO_2-SnO_2 nanoparticles are about 10-20 nm in diameter. The compositepowder is promising for chemical sensors.

Preparation and characterization of calcium aluminate by chemical synthesis

Saturated Ca（OH）2 and AlCl3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 m^2/g. The measurement of hydraulic exotherm revealed that the exothennal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.

Soft chemical synthesis and electrochemical properties of tin oxide-based materials as anodes for lithium ion batteries

A novel soft chemical approach was developed to synthesize tin oxide-based powders. The microstructure, morphology, and electrochemical performance of the materials were investigated by X-ray diffraction, scanning electron microscope and electrochemical methods. The results show that the particles of tin oxide-based materials form an interconnected network structure like mesoporous material. The average size of the particles is about 200 nm. The materials deliver a charge capacity of more than 570 mA·h·g-1. And the capacity loss per cycle is about 0.15% after being cycled for 30 times. The good electrochemical performance indicates that tin oxide-based materials are promising anodes for lithium ion batteries.

Soft chemical synthesis and luminescence properties of red long-lasting phosphors Y_2O_2S:Sm^(3+)

Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy （SEM） results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y202S：Sm3＋ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G5/2 →6H5/2, 4G~/2 →6H7/2, 4G5/2 →6H9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.

Chemical synthesis of magnetic nanocrystals:Recent progress

Colloidal chemical synthesis of various types of magnetic nanocrystals is discussed with regard to recent discoveries. We first outline the chemical preparation of single-component magnetic nanocrystals with controlled size, shape, and uniformity based on several solution-phase methods, especially thermal decomposition and/or reduction method. Then we discuss the synthetic strategies of multi-component nanocrystals incorporating at least one magnetic component by manipulating heterogeneous nucleation and growth process. Toward the end, approaches for preparing hollow/porous magnetic nanocrystals are highlighted. We believe that the summarized chemical synthesis will pave the way for the future development of extraordinary magnetic nanocrystals.

Chemical Synthesis and Magnetic Properties of Nanocrystalline (La_(0.67-X)Gd_X)Sr_(0.33)MnO_3 Using Amorphous Molecular Alloy as Precursors

A new route to synthesize nanosized crystalline of （La0.67-xGdx）Sr0.33MnO3 （X=0.05, 0.10, 0.15, 0.20） perovskite-type complex oxides at calcination temperature of 600-1000℃ using the amorphous molecular alloy as precursors was reported. The precursor could be completely decomposed into complex oxide at temperature below 500℃ according to the TGA and DTA results. XRD demonstrates that the decomposed species is composed of perovskite-type structure at calcination temperature of 600℃ for 2 h. The particle size that depends on the calcination temperature of the precursor is in a range of 30-120 nm as determined by transmission electron microscopy （TEM）. This method is effective and can be easily quantitatively controlled to synthesize nanosized perovskite-type complex oxides. The magnetic properties of （La0.67 xGdx）Sr0.33MnO3 nanocrystalline were preliminary studied.

A FACILE CHEMICAL SYNTHESIS of PENTADEOXYRIBONUCLEOTIDE d-TGGGT via PHOSPHOTRIESTER METHOD

In this paper,we report the chemical synthesis of oligonucleotide d-TGGGT using phosphotriester method.The protected pentamer d-MmtTGibGibGibT(=p-ClC6H_4-O(O)P)was deblocked by treatment with concentrated ammonium hydroxide and 80% acetic acid.The pure d-TGGGT obtained by chromatorgraphy on DEAE-Sephadex A-25 and Q-Sepharose FF could be hydrolyzed completely and confirmed by base ratio.

Chemical synthesis, spectroscopic properties and biochemical evaluation of an adenine nucleotide derivative 2-aminoadenosine 5＇-triphosphate

An adenine nucleotide derivative 2-aminoadenosine 5＇-triphosphate was chemically synthesized through four steps and was characterized with 1H NMR, 31p NMR, 13C NMR, EA and FT-IR. Its ultraviolet and fluorescence properties at various pH values were studied. Two pKa values for the compound were determined by the curves of UV absorption dependency on pH, Which were 0.68 and 4.83, respectively. The values were consistent with those calculated from ACD/Labs software. In addition, hydrolysis of the adenine nucleotide derivative in the catalysis of potato apyrase was studied. The competition of the ATP analogue with ATP for potato apyrase＇ active site was proved to be a sequential reaction mechanism.

Progress in Chemical Synthesis of Peptides and Proteins

For the proteins that cannot be expressed exactly by cell expression technology (e.g., proteins with multiple posttranslational modifications or toxic proteins), chemical synthesis is an important substitute. Given the limited peptide length offered by solid-phase peptide synthesis invented by Professor Merrifield, peptide ligation plays a key role in long peptide or protein synthesis by ligating two small peptides to a long one. Moreover, high-molecular-weight proteins must be synthesized using two or more peptide ligation steps, and sequential peptide ligation is such an efficient way. In this paper, we reviewed the development of chemical protein synthesis, including solid-phase peptide synthesis, chemical ligation, and sequential chemical ligation. © 2017, The Author(s).

Simple chemical synthesis and isotropic negative thermal expansion in MHfF_(6)(M=Ca,Mn,Fe,and Co)

The rapid progress of modern technologies has accelerated the prominence of thermal expansion mismatch between materials,and tunable thermal expansion materials will be a powerful safeguard against this challenge.Here,isotropic MHfF_(6)(M=Ca,Mn,Fe,and Co)compounds with tunable thermal expansion have been produced via a low-cost synthetic method and investigated.By utilizing temperature dependent X-ray diffraction(XRD)and Raman spectroscopy,combined with first principles calculations,it was revealed that the transverse thermal vibrations of the F atoms are dominated by low-frequency phonons with negative Grüneisen parameters and are therefore the origin of the negative thermal expansion(NTE).Very interestingly,with the increase of the M atomic number,the metal…F atomic linkages become stiffer,reducing the number of vibrational modes with negative Grüneisen parameters,so that the strong NTE can be gradually adjusted to moderate NTE and to near zero thermal expansion.The present study achieves the tunable thermal expansion in a new compound family and shed light on the internal mechanism from the perspective of lattice vibrational dynamics.

Chemical Synthesis of an Octasaccharide Derivative Related to Group B Streptococcus Cell-Wall Polysaccharide

Group B Streptococcus(GBS)is the major pathogen that causes invasive infectious diseases in neonates and infants.The develop-ment of preventive and therapeutic strategies against GBS infection has been becoming the most pressing subject worldwide.Group B carbohydrate(GBC),the group B-specific polysaccharide that distinguishes GBS with other streptococci species,has been identified as an attractive antigen for diagnosis and vaccine development because of its highly conservative tetra-antennary structure.In this paper,a highly convergent[3+5]glycosylation strategy for efficient synthesis of an octasaccharide derivative related to GBC oligo-saccharide unitⅡhas been developed.In this synthesis,each glycosylation reaction was efficiently constructed with glycosyl im-idates,especially trifluoroacetimidate,as donors,and each glycosidic bond was stereoselectively controlled via the neighboring group participation effect of acyl group on the 2-O-position of imidate donors or the solvent effect of Et_(2)O.Furthermore,the ami-noethylphosphate group was smoothly installed on the 6-O-position of D-glucitoll residue using the phosphoramidite method.After global deprotection,the target octasaccharide was successfully obtained from o-glucitol in 29 steps with an overall yield of 1.37%.The free amino group installed on the aminoethylphosphate spacer of the target molecule enables its modification with functional-ized biomolecules for further biological studies.

Research Progress on Synthesis of Superoxide Dismutase Mimics

Research on the synthesis of superoxide dismutase mimics by chemical and biologi-cal synthetic methods were reviewed.The advantages and limitations were analyzed.A prospect for the future development of superoxide dismutase mimics is proposed.

Chemical synthesis of a cyclotide via intramolecular cyclization of peptide O-esters

Cyclotides constitute a fascinating family of circular proteins containing ca.30 amino acid residues.They have a unique cyclic cysteine knot topology and exhibit remarkable thermal,chemical and enzymatic stabilities.These characteristics enable them to have a range of biological activities and promising pharmaceutical and agricultural applications.Here,we present a practical strategy for the chemical synthesis of cyclotides through the intramolecular ligation of fully unprotected peptide O-esters.This strategy involves the mild Fmoc solid-phase peptide synthesis of the peptide O-ester backbone,the head-to-tail cyclization of the cyclotide backbone by native chemical ligation,and the oxidative refolding to yield the natural knot protein.The simplicity and high efficiency of the strategy can be employed in the synthesis of artificial cyclotides for pharmaceutical applications.

Chemical Synthesis Residual Pyrolysis and Combustion: Kinetics and Evolved Gases Investigated by TG-FTIR

Chemical synthetic residual is one of the solid wastes generated from pharmaceutical industry.The pyrolysis and combustion characteristics of chemical synthesis residual were investigated using a thermogravimetric analyser coupled with Fourier transform infrared spectroscopy(TG-FTIR)in this study.The processes of pyrolysis and combustion can be divided into three stages.The average weight loss rate of pyrolysis process at low temperature was higher than that of combustion.The kinetic parameters of chemical synthesis residual during pyrolysis and combustion were calculated based on the TG results.Acetic acid and 4-aminophenol were the main evolved matter observed in the pyrolysis process.The emission characteristics of combustion at low temperature were similar to that of the pyrolysis,while CO2 was found as the major gaseous product at high temperature.A high temperature about 850°C is needed to make sure the complete combustion of chemical synthesis residual.

Chemical synthesis of SmCo5/Co magnetic nanocomposites

A three-step chemical synthesis of SmCo5/Co nanocomposites was developed. Firstly, the Co-Sm（OH）3-Ca（OH）2 precursors were prepared by co-precipitation.Secondly, SmCo5 particles were obtained by reductive annealing of the precursors. At last, the SmCo5/Co nanocomposites were achieved by chemical deposition based on SmCo5 particles. The SmCo5/Co nanocomposites contain hard magnetic phase of SmCo5 with about 100 nm in size and soft magnetic phase of Co with about 8 nm in size,exhibiting independent two-phase structure without alloying. Compared to that of single-phase SmCo5 particles, the saturation magnetization of SmCo5/Co nanocomposites is increased by 27.5%. The synthesis provides a new route to fabricate SmCo-based nanocomposites.

Discovery, structure,and chemical synthesis of disulfide-rich peptide toxins and their analogs

Recently, medicinal peptide molecules are of great interest to many international pharmaceutical companies, mainly because of their relatively lower research costs, shorter research cycles, and the greater likelihood of being drugs, when compared with traditional small molecules. Due to the great variety in molecule structures and the diverse biological functions, disulfide-rich peptide toxins have become a shining molecular library for the development of polypeptide drugs. In view of the increasing amount of related publications, here we summarize the discovery, structural elucidation and chemical synthesis of disulfide-rich peptide toxins and their analogs.

Racemic X-ray structure of L-type calcium channel antagonist Calciseptine prepared by total chemical synthesis

Snake toxin Calciseptine as a natural antagonist of L-type calcium channel has potential drug values, but its structural information remains unknown. Here, we report the total chemical synthesis of Calciseptine by using hydrazide based native chemical ligation. The crystal structure of Calciseptine was determined by racemic protein crystallography technique. Compared to the structure of its homologous family protein, we found that Calciseptine is adopting a typical three-finger structure.

Chemical synthesis, structure and magnetic properties of Co nanorods decorated with Fe_3O_4 nanoparticles

Magnetic anisotropic nanocomposites have attracted tremendous interests, due to their unexpected properties originating from the interactions of the interfaces except for the intrinsic features. In this work, we develop a facile solution chemistry synthesis method to prepare the one-dimensional(1 D) Co-Fe3O4 heterostructures with hard magnetic property. Interestingly, the Fe precursor firstly decompose and nucleate individually, and then grow on the surface of the hexagonal closed-packed(hcp) Co nanorods(NRs) upon prolonging heating time at higher temperature, which is different from the general seed-mediated growth model. The distribution density of Fe3O4 nanoparticles(NPs) on the surface of the Co NRs can be varied with the addition of Fe source,modulating the values of coercivity and saturation magnetization for the Co-Fe3O4 heterostructures. The as-synthesized Co-Fe3O4 heterostructures maintain the hard magnetic properties with a coercivity value more than 2.5 kOe as well as a saturation magnetization value up to 128.3 emu g-1, indicating the preservation of the anisotropy of the hcp Co NRs.

Chemical synthesis of a synthetically useful L-galactosaminuronic acid building block

Most bacterial cell surface glycans are structurally unique, and have been considered as ideal target molecules for the developments of detection and diagnosis techniques, as well as vaccines. Chemical synthesis has been a promising approach to prepare well-defined oligosaccharides, facilitating the structure-activity relationship exploration and biomedical applications of bacterial glycans. L-Galactosaminuronic acid is a rare sugar that has been only found in cell surface glycans of gram-negative bacteria. Here, an orthogonally protected L-galactosaminuronic acid building block was designed and chemically synthesized. A synthetic strategy based on glycal addition and TEMPO/BAIB-mediated C6 oxidation served well for the transformation of commercial L-galactose to the corresponding L-galactosaminuronic acid. Notably, the C6 oxidation of the allyl glycoside was more efficient than that of the selenoglycoside. In addition, a balance between the formation of allyl glycoside and the recovery of selenoglycoside was essential to improve efficiency of the NIS/TfOH-catalyzed allylation. This synthetically useful L-galactosaminuronic acid building block will provide a basis for the syntheses of complex bacterial glycans.

Chemical synthesis and structural analysis of guanylate cyclase C agonist linaclotide

Guanylate cyclase C(GC-C) is an important receptor protein expressed by intestinal epithelial cells, and its dysregulation leads to severe intestinal diseases. Linaclotide is a 14-amino acid peptide approved by the FDA for the treatment of irritable bowel syndrome with constipation(IBS-C), which activates guanylate cyclase C to accelerate intestinal transit. Drug molecule design based on structural information plays a crucial role and the activity of linaclotide still need to improve, while the structure of linaclotide remains unknown. In this work, linaclotide and its D-enantiomer were obtained through Fmoc solid phase peptide synthesis method and co-crystalized through racemic crystallization. The crystal structure showed that linaclotide has a tight, three-beta turns structure immobilized by three pairs of disulfide bonds.