Multiple 1,2,3-thiadiazoles

A series of compounds 3a-d,i-n with two or three 1,2,3-thiadiazole rings, useful for photocrosslinking processes, was prepared from the di- or triketones 1a-d,i-n via the corresponding hydrazones 2a-d,i-n by applying the Hurd-Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g , was elaborated for the olefinic system 3h.     

Analysis of enkephalins, beta-endorphins and small peptides in their sequences by highly sensitive high-performance liquid chromatography with electrochemical detection: implications in opioid peptide metabolism

Sensitivity in the 10-100 pg range for enkephalins, beta-endorphin, tyrosine (T), 12 tyrosylglycine (T-G) and tyrosylglycylglycine (T-G-G) was attained by using a high-performance liquid chromatographic (HPLC) method with electrochemical detection which is at least 100 times more sensitive than HPLC with UV detection. The chromatographic conditions on a reversed-phase C18 silica column were 50 mM sodium phosphate buffer (pH 2.1) (A) in acetonitrile-methanol (1:1) (B), isocratic mixture, flow-rate 0.6-1 ml/min, UV detection at 205 nm, electrochemical oxidation potential + 1.25 V. The separation of T, T-G and T-G-G was obtained by using 10% B while the separation of the pentapeptide, enkephalins required 40% B. Separation of enkephalins from beta-endorphin was attained at a shorter retention times did not exceed 15 min. This method can be used to determine tissue levels and pharmacodynamics of enkephalins and beta-endorphin. A highly specific measurement of the different enzymes involved in the metabolism of enkephalin has been achieved.     

Metal-Assisted Oxidative Cyclization of Arylamidrazones I. Synthesis of 3-Acetyl-1,4-dihydro-1-phenyl-1,2,4-benzotriazine

Summary. In the presence of RuCl₃, N-phenylamidrazone underwent oxidative cyclization into 1,4-dihydro-1-phenyl-1,2,4-benzotriazine, the structure of which is established by spectral and X-ray diffraction data.     

Brownian Motion and Ornstein–Uhlenbeck Processes in Planar Shape Space

We discuss Brownian motion and Ornstein–Uhlenbeck processes specified directly in planar shape space. In particular, we obtain the drift and diffusion coefficients of Brownian motion in terms of Kendall shape variables and Goodall–Mardia polar shape variables. Stochastic differential equations are given and the stationary distributions are obtained. By adding in extra drift to a reference figure, Ornstein–Uhlenbeck processes can be studied, for example with stationary distribution given by the complex Watson distribution. The triangle case is studied in particular detail, and some simulations given. Connections with existing work are made, in particular with the diffusion of Euclidean shape. We explore statistical inference for the parameters in the model with an application to cell shape modelling.      

Turbulent heat transfer and fluid flow of alumina nanofluid inside three-lobed twisted tube

Turbulent flow characteristics and heat transfer applications of a twisted heat exchanger with 3-lobed cross section along with Y-tape insert are numerically studied. The working fluids for the simulations are pure water and water–Al₂O₃ nanofluid using two-phase mixture model. The study is carried out for various nanofluid volume fractions of 0.01, 0.02 and 0.03 with Reynolds number in the range of 5000–20,000. The effect of nanoparticles in heat transfer augmentation for smooth and lobed tubes is discussed based on presenting the highest thermal performance, which is a relation between heat transfer rate and pressure loss. Results show that implementing the twisted tube with Y-tape insert enhances the heat transfer more than the twisted tube. Relative Nusselt numbers for twisted tubes decrease with Reynolds number in comparison with the plain tube. Turbulent intensity, swirl number and tangential velocity of twisted tube with insert are higher than empty twisted tube indicating that inserting the Y-tape intensifies the turbulence and disturbs the fluid flow further. On the other hand, although the twisted tube increases the pressure drop more than plain tube, the case with Y-tape drastically increases the friction factor. So, the thermal performance of twisted tube with insert is lower than empty twisted tube. Adding nanoparticles to the base fluid has different influence on the investigated cases. It augments the relative Nusselt number inside plain tube and empty twisted tube with slight increment in friction factor. Increasing the nanoparticles concentration enhances the heat transfer rates for these cases while it does not increase the relative Nusselt number inside twisted tube with Y-tape insert at high Reynolds number and nanoparticle concentration. Moreover, it can be found that twisted tube with or without Y-tape insert is more efficient at low Reynolds number in comparison with the plain tube.

     

One-Pot Chemical Protein Synthesis Utilizing Fmoc-Masked Selenazolidine to Address the Redox Functionality of Human Selenoprotein F**

Human SELENOF is an endoplasmic reticulum (ER) selenoprotein that contains the redox active motif CXU (C is cysteine and U is selenocysteine), resembling the redox motif of thiol-disulfide oxidoreductases (CXXC). Like other selenoproteins, the challenge in accessing SELENOF has somewhat limited its full biological characterization thus far. Here we present the one-pot chemical synthesis of the thioredoxin-like domain of SELENOF, highlighted by the use of Fmoc-protected selenazolidine, native chemical ligations and deselenization reactions. The redox potential of the CXU motif, together with insulin turbidimetric assay suggested that SELENOF may catalyze the reduction of disulfides in misfolded proteins. Furthermore, we demonstrate that SELENOF is not a protein disulfide isomerase (PDI)-like enzyme, as it did not enhance the folding of the two protein models; bovine pancreatic trypsin inhibitor and hirudin. These studies suggest that SELENOF may be responsible for reducing the non-native disulfide bonds of misfolded glycoproteins as part of the quality control system in the ER.     

Synthesis and characterization of organosoluble polyamides from quinoxaline based diamine

<正>Aromatic/aliphatic polyamides were synthesized from a diamine monomer,2,3-bis-p-aminophenylquinoxaline (Ⅳ),based on quinoxaline and various dicarboxylic acids of aliphatic,aromatic and heterocyclic.The diamine and polyamides were characterized by elemental analysis,FTIR and ~1H-NMR.The solubility of the polyamides was affected by the quinoxaline and heterocyclic groups in the polymer chain.They were all soluble in common organic solvents such as dimethylsulfoxide(DMSO),N,N-dimethylformamide(DMF) and N-methylpyrolidone(NMP).The polyamides showed inherent viscosity in the range of 0.25-0.3 dL/g in DMSO at 25℃and good thermal stability with the char yields in the range of 65%-82%at 600℃in nitrogen.     

Ruthenium(II) 2,2′-bipyridine complexes incorporating substituted phenylazo-(2-(phenylthio))phenylmethine ancillary ligands. Synthesis,crystal structure,spectroscopic and redox properties

Abstract  

Five ruthenium complexes bearing phenylazo-(2-(phenylthio))phenylmethine ligands of the general type trans-[Ru^II(bpy)(L)(Cl)₂] (C1–C5) {L = YC₆H₄N=NC(COCH₃)=NC₆H₄(2-SC₆H₅), H (L1), Cl (L2), OCH₃ (L3), Br (L4), or NO₂ (L5)} have been synthesized. The crystal structure of trans-[Ru(bpy)(L1)(Cl)₂] (C1) is reported and shows no direct metal–S interaction. The complexes have been characterized through spectroscopic (IR, UV/vis and NMR) and electrochemical (CV) techniques. The electrochemical parameters (E _L(L)) of the azoimine ligands are reported.     

Blood compatible carbon nanotubes--nano-based neoproteoglycans

Although nanotechnology has provided a rich variety of nanomaterials (1-100 nm) for in vivo medical applications, the blood compatibility of all these nanobiomaterials is still largely unexamined. Here, we report the preparation of blood-compatible carbon nanotubes (CNTs) that potentially represent the building blocks for nanodevices having in vivo applications. Activated partial thromboplastin time (APTT) and thromboelastography (TEG) studies prove that heparinization can significantly enhance the blood compatibility of nanomaterials.