Structural characterization and angiotensin-converting enzyme (ACE) inhibitory mechanism of Stropharia rugosoannulata mushroom peptides prepared by ultrasound

To reveal the structural characteristics and angiotensin-converting enzyme (ACE) inhibition mechanism of Stropharia rugosoannulata mushroom peptides prepared by multifrequency ultrasound, the peptide distribution, amino acid sequence composition characteristics, formation pathway, and ACE inhibition mechanism of S. rugosoannulata mushroom peptides were studied. It was found that the peptides in S. rugosoannulata mushroom samples treated by multifrequency ultrasound (probe ultrasound and bath ultrasound mode) were mainly octapeptides, nonapeptides, and decapeptides. Hydrophobic amino acids were the primary amino acids in the peptides prepared by ultrasound, and the amino acid dissociation of the peptide bonds at the C-terminal under the action of ultrasound was performed mainly to produce hydrophobic amino acids. Pro and Val (PV), Arg and Pro (RP), Pro and Leu (PL), and Asp (D) combined with hydrophobic amino acids were the characteristic amino acid sequence basis of the active peptides of the S. rugosoannulata mushroom. The docking results of active peptides and ACE showed that hydrogen bond interaction remained the primary mode of interaction between ACE and peptides prepared by ultrasound. The peptides can bind to the amino acid residues in the ACE active pocket, zinc ions, or key amino acids in the domain, and this results in inhibition of ACE activity. Cation–pi interactions also played an important role in the binding of mushroom peptides to ACE. This study explains the structural characteristics and ACE inhibition mechanism used by S. rugosoannulata mushroom peptides prepared by ultrasound, and it will provide a reference for the development and application of S. rugosoannulata mushroom peptides.     

Surface-initiated addition polymerization of norbornene by a Pd(II) catalyst bearing acetylacetone ligand on the glass slide

A Pd catalyst bearing acetylacetone ligand [(CH₃CO)₂CHPdCl₂] was covalently attracted onto the surface of glass slides, and then these Pd-terminated glass slides were immersed into a toluene solution of norbornene (NB) to produce a vinyl-type addition polynorbornene (PNB) layer on the surface of glass slides. It was found that the contract angles of the PNB-terminated glass slides surface increased with the increasing of polymerization time, and the thickness of the PNB layers were approximately 0-44.0 μm when the polymerization time was 0.5-24 h. The researching on etching also has been operated.     

Six new photolabile linkers for solid phase synthesis. 2. Coupling of various building blocks and photolytic cleavage

Photolabile linkers are very useful in the generation of combinatorial libraries as they offer compound cleavage under mild conditions directly into a solvent suitable for biological testing. Six new photolabile linkers have been developed which allow coupling of building blocks with a carboxy, amino, hydroxy and sulfonyl group. Photolytic cleavage of these building blocks will give libraries with carboxy, amido, methylamido, amino, ureido, hydroxy, aminocarbonyloxy and aminosulfonyl terminal groups. Coupling conditions for these reactions were elucidated and the photolytic cleavage reaction was studied.     

Chemical synthesis of TASP arrays and their application in protein design

A combinatorial synthesis of de novo proteins is described. The concept of template-assembled synthetic proteins (TASP) has been adapted to an orthogonal assembly of small libraries of purified peptide building blocks. It is combined with the spot synthesis of peptides which is exploited to array cyclic decapeptide templates on cellulose membranes. A cleavable linker on the cellulose allows control of the synthesis. The hydrophilic proteins are constructed by successive cleavage of orthogonal protecting groups on the template, followed by coupling of amphipathic helices in a predefined orientation and finally by incorporation of a cofactor. Libraries of peptides with variation of the amino acids expected to be close to the cofactor were coupled to the cellulose-bound template in all combinations, yielding up to 500 variants of a protein. Cofactors have been inserted either at non-covalent binding sites as heme and Cu2+ or by covalent modification of amino acids as Ru-bipyridine or flavin. The proteins were screened by recording their UV-vis spectra directly on the solid support. The properties screened include the redox potential of heme proteins, charge transfer bands indicating the ligation of Cu-centers, enzymatic activity, and folding stability. Synthesis of the best hits as soluble variants was used for detailed characterization. Iterative improvement in a second screening cycle was efficient in finding novel copper proteins. We discuss the prospects of synthesizing proteins by extending the concept to beta-sandwich proteins and construction of efficient peptide libraries with computer-supported design, as well as the possible usage of improved solid phase materials.     

Increasing the free spectral range of silica waveguide rings for filter applications

Ring resonators are promising building blocks for developing compact optical filters with arbitrary functions; however, a major challenge for planar waveguide filter implementations is to overcome the limited free spectral range (FSR) for a given core-to-cladding refractive-index difference (D) while maintaining low loss and a large range of coupling ratios. The loss and coupling of rings operating in the whispering-gallery-mode regime were investigated by use of Ge-doped silica waveguides with a low refractive-index difference (D=0.75%) . A FSR of 12 GHz with a loss of 0.36 dB/cm was demonstrated with coupling ratios of 30% (41% optimum).     

Facile synthesis of novel amino acid-like building blocks by N-alkylation of heterocyclic carboxylates with N-Boc-3-iodoazetidine

Molecular Diversity - An efficient protocol providing easy access to highly functionalized heterocyclic compounds as novel organic building blocks was developed by coupling alkyl pyrazole-,...     

Library generation through successive substitution of trichlorotriazine

Summary The decreasing reactivity of tri-, di- and monochlorotriazine was utilized for the solid-phase construction of a combinatorial library with three randomized positions, using 20 amino acids and 50 amines as building blocks. The first chlorine atom was selectively substituted by coupling a large excess of trichlorotriazine to the support-bound amino acid, thus avoiding simultaneous substitution of the second chlorine. The second and third diversity positions were selectively introduced by coupling amines at different temperatures. Mixtures of model compounds were synthesized and analyzed, showing the correct representation of all expected components. A library composed of 12 000 compounds was generated using this method.     

Enzymolysis kinetics and activities of ACE inhibitory peptides from wheat germ protein prepared with SFP ultrasound-assisted processing

There is a great demand for developing efficient enzymolysis methods in order to increase the enzymolysis efficiencies and activities of angiotensin converting enzyme (ACE) inhibitory peptides from wheat germ protein. The enzymolysis kinetics, ACE inhibitory activity of peptide and conversion rate of protein were studied using sweep frequency and pulsed (SFP) ultrasound-assisted enzymolysis and the results were compared with traditional enzymolysis. The studied factors were enzymolysis time and substrate concentration. By considering the activity of ACE inhibitory peptide and operation cost, the recommended conditions of SFP ultrasound-assisted enzymolysis were enzymolysis time of 120 min and substrate concentration of 24.0 g/L, which gave high conversion rates of protein (60.7%) and ACE inhibitory activity of peptide (65.9%). Compared to traditional enzymolysis, SFP ultrasound-assisted enzymolysis significantly increased the initial reaction rate (V) by 60.0% at substrate concentration of 24.0 g/L, increased the apparent breakdown rate constant (k(A)) by 66.7%, decreased the apparent constant (K(M)) by 6.9%, and raised the conversion rate of protein by 35.5% and ACE inhibitory activity of peptides by 35.6% under the recommended conditions. It has been concluded that SFP ultrasound can remarkably raise the enzymolysis efficiency and activity of ACE inhibitory peptides from wheat germ protein.     

Microwave-enhanced transition metal-catalyzed decoration of 2(1H)-pyrazinone scaffolds

The 2(1H)-pyrazinones have been demonstrated to be versatile building blocks for the synthesis of biologically active compounds. Here, an efficient method is described for the decoration of these interesting scaffolds. Microwave-assisted palladium catalyzed reactions allow the easy introduction of different substituents at the C3- and even at the rather unreactive C5-position of the pyrazinones. Stille, Suzuki, Heck, Sonogashira reactions, in addition to reductive dechlorinations, and cyanation reactions are investigated.     

A novel approach to chemical microarray using ketone-modified macromolecular scaffolds: Application in micro cell-adhesion assay

This paper describes a novel strategy for the preparation of chemical microarrays using macro-molecular scaffolds. The macromolecular scaffolds are first functionalized with ketone groups and compounds of interest containing an aminooxy group are conjugated onto the ketone-modified scaffolds through a chemoselective oxime ligation. The conjugate mixtures are then spotted directly onto a plastic or glass surface to form compound microarrays. Because a constant amount of scaffold is used in the presence of excess compound in the ligation reaction, the amount of compound actually immobilized per microarray spot is constant and dependent on the scaffold concentration. Using this approach, 60 different peptides were ligated to human serum albumin or agarose scaffolds, and the peptide conjugates subsequently printed on glass or polystyrene surface to form microarrays. These peptide microarrays were subsequently evaluated and optimized for binding of Jurkat leukemic cancer cells.     

The influence of polymer concentrations on the structure and mechanical properties of porous polycaprolactone-coated hydroxyapatite scaffolds

Polycaprolactone (PCL)-coated porous hydroxyapatite (HA) composite scaffolds were prepared by combining polymer impregnating method with dip-coating method. Three different PCL solution concentrations were used in dip-coating process to improve the mechanical properties of porous HA scaffolds. The results indicated that as the concentration of PCL solution increases the compressive strength significantly increased from 0.09 MPa to 0.51 MPa while the porosity decreased from 90% to 75% for the composite scaffolds. An interlaced structure was found inside the pore wall for all composite scaffolds due to the penetration of PCL. The porous HA/PCL composite scaffolds dip-coated with 10% PCL exhibited optimal combination of mechanical properties and pore interconnectivity, and may be a potential bone candidate for the tissue engineering applications.     

Focused enumeration and assessing the structural diversity of scaffold libraries: conformationally restricted bicyclic secondary diamines

Comprehensive enumeration of conformationally restricted bicyclic secondary diamines (CRDA) was performed within defined structural limits, yielding a library of all theoretically possible compounds of this class, potentially useful as building blocks for drug design. In order to assess structural diversity of the generated library, molecular geometries of the library members were optimized using DFT calculations. It was shown that the distance between the amino groups and their relative orientation in space vary widely over the whole library, which might be beneficial for diversity-oriented conformational restriction approach in drug discovery. There are many representatives of "three-dimensional" scaffolds in the CRDA library. Selected literature data on biological activity of the known CRDA derivatives were discussed, demonstrating utility of the CRDA scaffold hopping in drug design.     

外型和内型C-2位单取代降冰片烯衍生物的核磁共振波谱研究

C-2位单取代降冰片烯衍生物中降冰片烯环存在各向异性,且多数为外型和内型异构体的混合物,导致其结构解析困难.针对这一问题,本文在制备了单一构型的C-2位羧基和羟甲基取代的降冰片烯衍生物的基础上,利用¹H NMR、DEPT135、¹H-¹H COSY、¹H-¹³C HMQC、¹H-¹H NOESY谱和相应的耦合裂分信息,对外型-5-降冰片烯-2-羧酸、内型-5-降冰片烯-2-羧酸、外型-5-降冰片烯-2-甲醇和内型-5-降冰片烯-2-甲醇的¹H和¹³C NMR信号进行归属,并探讨了降冰片烯衍生物的取代基种类及空间构型对¹H NMR化学位移的影响.     

Electric double layer of anisotropic dielectric colloids under electric fields

Anisotropic colloidal particles constitute an important class of building blocks for self-assembly directed by electrical fields. The aggregation of these building blocks is driven by induced dipole moments, which arise from an interplay between dielectric effects and the electric double layer. For particles that are anisotropic in shape, charge distribution, and dielectric properties, calculation of the electric double layer requires coupling of the ionic dynamics to a Poisson solver. We apply recently proposed methods to solve this problem for experimentally employed colloids in static and time-dependent electric fields. This allows us to predict the effects of field strength and frequency on the colloidal properties.     

Preparation and Characterization of Poly(L-lactide-co-glycolide-co-ε-caprolactone)/Nano-biaoactive Glass-Nano-β-tricalcium Phosphate Composite Scaffolds

Abstract

Polymeric/ceramic composite scaffolds that are biocompatible and biodegradable are widely used for tissue engineering applications. In this work a series of poly(L-lactide-co-glycolide-co-ε-caprolactone)/nano-biaoactive glass-nano-β-tricalcium phosphate composite scaffolds were successfully fabricated and the influences of the inorganic content and freezing temperature on the physical properties were studied. The composite scaffolds with various inorganic contents showed an interconnected pore structure with irregular shapes. The composite scaffolds had a porosity that was reduced with increasing inorganic content and decreasing freezing temperature. The incorporation of inorganic fillers and decreasing freezing temperature improved the mechanical properties of the hybrid scaffolds. By appropriate control of these two factors (10.0?wt% content of NBAG and β-TCP with freezing at ?30?°C) a suitable composite scaffold was prepared as a potential bone tissue engineering implant.     

Radioactivity concentration measurement and analysis in construction floor materials of Korea

In this study, the radioactive concentrations contained in samples of commonly used building floor materials were measured. This result can be used as basic information for public health and the environment. Among building floor materials, samples of induction blocks, cement bricks, artificial granite blocks and compact high-pressure blocks were chosen and used. A detailed gamma nuclide analysis was performed with a multichannel analyzer by putting these samples on a high-purity germanium detector which is a semiconductor detector. In order to measure the concentration of radionuclides, a spectrum file was obtained by analyzing the concentration of gamma radionuclides and setting the measurement time as 1000, 4000, 7000 and 10,000?s. According to the study results, K-40, Bi-214, Pb-214, Ra-226 and U-235 were detected in the induction blocks measured at 10,000?s and K-40, Th-230, Bi-214, Pb-214, Ra-226 and Na-22 were detected in the cement bricks measured at 10,000?s. K-40, Bi-214, Pb-214, Th-234, U-235 and Ra-223 were detected in the artificial granite blocks measured at 10,000?s and K-40, Bi-214, Pb-214, Th-234, Ra-226, Ra-223 and Mn-54 were detected in the compact high-pressure blocks. In conclusion, low-level radioactivity was detected in building floor materials, so it is thought that measures to reduce radioactivity and further studies on this will be needed.     

Ultrasonic compatibilization of polyelectrolyte complex based on polysaccharides for biomedical applications

In recent years, there has been an increasing interest in the design of biomaterials for cartilage tissue engineering. This type of materials must meet several requirements. In this study, we apply ultrasound to prepare a compatibilized blend of polyelectrolyte complexes (PEC) based on carboxymethyl cellulose (CMC) and chitosan (CHI), in order to improve stability and mechanical properties through the inter-polymer macroradicals coupling produced by sonochemical reaction. We study the kinetic of the sonochemical degradation of each component in order to optimize the experimental conditions for PEC compatibilization. Scaffolds obtained applying this methodology and scaffolds without ultrasound processing were prepared and their morphology (by scanning electron microscopy), polyelectrolyte interactions (by FTIR), stability and mechanical properties were analyzed. The swelling kinetics was studied and interpreted based on the structural differences between the two kinds of scaffolds. In addition we evaluate the possible in vitro cytotoxicity of the scaffolds using macrophage cells in culture. Our results demonstrate that the ultrasound is a very efficient methodology to compatibilize PEC, exhibiting improved properties compared with the simple mixture of the two polysaccharides. The test with murine macrophage RAW 264.7 cells showed no evince of cytotoxicity, suggesting that PEC biomaterials obtained under ultrasound conditions could be useful in the cartilage tissue engineering field.     

Ultrasound-assisted preparation of ACE inhibitory peptide from milk protein and establishment of its in-situ real-time infrared monitoring model

A scheme for preparing milk ACE inhibitory peptides by in vitro proteolysis and simulated gastrointestinal digestion was constructed. The ultrasonic assisted pretreatment was used to improve the enzymolysis of milk protein. The in-situ real-time infrared was used to establish monitoring model of enzymatic process. Results showed that under the conditions of single frequency 28 kHz, ultrasound time 40 min, ultrasound power density 20 W/L, milk protein concentration 34 g/L, batch ratio 2:4 and initial temperature 30 °C, the ACE inhibition rate of gastric digestion of enzymatic hydrolysate reached 67.20%, which was 22.87% higher than that of non-ultrasound samples. The results of secondary structure studies of proteins showed that after the ultrasonic treatment, the content of α-helix and β-corner reduced, and the content of β-folding and random coil increased. Compared with the control group, the ultrasonic treatment increased surface hydrophobicity and the content of SH while reduced the content of SS in milk protein, thus improving the ACE inhibitory activity of enzymatic hydrolysates. Furthermore, three quantitative prediction models of PLS, iPLS and Si-PLS for ACE inhibition rate of milk protease hydrolysates were established. And all these three different in-situ real-time prediction models had good predictive effect on the ACE inhibition rate of milk proteolysis products and gastrointestinal simulated digestion products.     

Variable orbital coupling in a two-dimensional quantum-dot solid probed on a local scale

The optoelectronic properties of semiconductor quantum-dot (QD) solids depend on the electronic structure of the building blocks and their interactions. Disorder may affect the coupling on a local scale. We have measured the density of states of 2D arrays of PbSe QDs site by site using scanning tunneling spectroscopy. It markedly differs from that of isolated QDs due to electronic coupling in the array. We observe strong local variations in the coupling strength with two prototypical cases: delocalization of the conduction electrons only, and full coupling with both hole and electron delocalization over the QD sites in the array.     

Heavy photon states in photonic chains of resonantly coupled cavities with supermonodispersive microspheres

We propose and demonstrate a "bottom-up" approach to constructing photonic structures for photon manipulation. Supermonodispersive polymer microspheres are used as building blocks and a size uniformity better than 0.05% could be obtained by sorting the spheres using spectroscopic methods. The spheres are positioned in a V groove on a silicon substrate and form a photonic chain with resonant coupling of the optical whispering-gallery modes. Photonic band modes are clearly observed in fluorescence and resonant scattering spectra, and an excellent agreement with a tight-binding model calculation is found. Heavy photon states and a group index as high as 40 are obtained.