Improved Diazo-Transfer Reaction for DNA-Encoded Chemistry and Its Potential Application for Macrocyclic DEL-Libraries

DNA-encoded libraries (DEL) are increasingly being used to identify new starting points for medicinal chemistry in drug discovery. Herein, we discuss the development of methods that allow the conversion of both primary amines and anilines, attached to DNA, to their corresponding azides in excellent yields. The scope of these diazo-transfer reactions was investigated, and a proof-of-concept has been devised to allow for the synthesis of macrocycles on DNA.     

Do students really understand what an ordinary differential equation is?

Differential equations (DEs) are important in mathematics as well as in science and the social sciences. Thus, the study of DEs has been included in various courses in different departments in higher education. The importance of DEs has attracted the attention of many researchers who have generally focussed on the content and instruction of DEs. However, DEs are complex issues that students may find difficulty to understand. The limited research in this literature points to the need for more studies on students’ conceptions, and understanding of DEs and their basic concepts. The objective of this study is to fill this need by revealing the understanding, difficulties and weaknesses of the students who are successful in algebraic solutions, in relation to the concepts of DEs and their solutions. For this purpose, 77 students were asked 13 DE questions (6 of them about algebraic solution, and the rest about interpreting DEs and their solutions). From an analysis of the students’ answers, it was concluded that the students who were quite successful in algebraic solutions, indeed did not fully understand the related concepts, and they had serious difficulties in relation to these concepts.     

Organic vapor sensing properties and characterization of α-naphthylmethacrylate LB thin films

Determination of organic vapor sensing properties of α-Naphthylmethacrylate (α-NMA) monomer based Langmuir-Blodgett (LB) thin films was aimed in this study. LB thin film fabrication was performed on quartz glass and quartz crystal substrates in order to investigate the characterization and organic vapor properties of α-NMA materials by using UV-Visible, Atomic Force Microscopy (AFM) and Quartz Crystal Microbalance (QCM) techniques. π-A isotherm graph was taken and a suitable surface pressure value were primarily determined as 13?mN m^?1 for successful α-NMA LB thin film fabrication. Transfer ratio value was found to be ≥ 0.93 for quartz glass and quartz crystal substrates. The typical frequency shift per layer was obtained as 16.93?Hz/layer and the deposited mass onto a quartz crystal was calculated as 271.30?ng/layer (1.02?ng mm^?2). The sensing responses of α-NMA LB films against dichloromethane, chloroform, toluene and m-xylene were measured by QCM system. Dichloromethane created the maximum shift in the resonance frequency than other organic vapors used in this study. Results exhibited that α-NMA LB thin films were potential candidates for organic vapor sensing applications, especially high sensitive detection of dichloromethane at room temperature.     

Canal Surfaces with Quaternions

Quaternions are more usable than three Euler angles in the three dimensional Euclidean space. Thus, many laws in different fields can be given by the quaternions. In this study, we show that canal surfaces and tube surfaces can be obtained by the quaternion product and by the matrix representation. Also, we show that the equation of canal surface given by the different frames of its spine curve can be obtained by the same unit quaternion. In addition, these surfaces are obtained by the homothetic motion. Then, we give some results.     

Synthesis of two calix[4]arene diamide derivatives for extraction of chromium(VI)

The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonylmethoxy-26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The ¹H and ¹³C NMR, data showed that the synthesized compounds exist in the cone conformation. The complexing properties of these compounds toward Cr₂O₇²⁻/HCr₂O₇⁻ anions are also studied. It has been observed that receptors 5 and 6 are better extractant than the compounds 3 and 4. The protonated alkyl ammonium form of 5 and 6 is an effective extractant for transferring HCr₂O₇⁻/Cr₂O₇²⁻ anions from an aqueous phase into a dichloromethane layer.     

New Soluble Coordination Chain Polymers of Nickel(II) and Copper(II) ions and their Biological Activity

A new tetraoxime ligand, (2E, 3E, 9E, 10E)-1, 4, 8, 11-tetraazacyclotetradecane-2, 3, 9, 10-tetrone tetraoxime has been prepared by the template condensation of 1,3-propanediamine and cyanogen-di-N-oxide, obtained by treating (E, E)-dichloroglyoxime in CH₂Cl₂ with Na₂CO₃ at −10 °C. The coordination chain polymers {[(pnngH₂)₂Ni]_n (5) and [(pncgH₂)₂Cu]_n(6)} of two transition metal ions, [Ni(II) and Cu(II)] with the vic-dioxime ligand have been prepared. The oxime ligand acts as a polydentate ligand bending through nitrogen atoms in the presence of a base, as do most of the vic-dioximes. In the complexes, the chloride ions coordinate to the nickel and copper ions. The structures of these novel vic-dioxime compounds are proposed on the basis of the elemental analyses, molar conductance data, i.r., and U.v.–visible are presented. Elemental analyses indicate a ligand metal ratio of 1:1 in the coordination polymers. Conductivity measurements have shown that mono- and polynuclear complexes are non-electrolytes. In addition, anti-microbial activities of the compounds have been investigated.     

Synthesis and characterization of new azo-linked Schiff bases and their cobalt(II), copper(II) and nickel(II) complexes

Azo compounds were prepared by the reaction between benzenediazonium chloride and 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid monosodium salt under alkaline conditions. Two new azo-linked Schiff base ligands, 4-(3-methoxysalicylidene)-5-hydroxy-6-(2-hydroxyphenylazo)-2,7-naphthalene disulfonic acid disodium salt (H₂L) and 4-(3-methoxysalicylidene)-5-hydroxy-6-(2-hydroxy-4-cholorophenylazo)-2,7-naphthalenedisulfonic acid disodium salt (H₂L¹), have been synthesized. Also, the new Cu^II, Ni^II and Co^II complexes of the azo-linked Schiff base ligands were prepared and characterized by infrared spectra, UV–Vis, ¹H- and ¹³C-n.m.r., attached proton test (APT) and distortionless enhancement by polarization transfer (DEPT) and atomic absorption spectroscopy, mass spectrocopy, elemental analyses, thermogravimetric analysis, conductivity and magnetic measurements. It was determined that the synthesized ligands were comprised of six-membered rings due to intramolecular hydrogen bonding. The results suggested that condensation of the azo-derivative compounds and o-vanillin in a 1:1 molar ratio produces mononuclear Schiff base ligands with an ONO donor set. Preliminary histological studies were made. Magnetic moment studies showed that all complexes have a tetrahedral configuration.     

Spectroscopic and Analytic Properties of New Copper(II) Complex of Antiviral Drug Valacyclovir

The complexation processes between Cu^II and the antiviral drug, valacyclovir hydrochloride (H₂L), were studied under different reaction conditions, using UV-Vis, IR and mass spectra, magnetochemical, thermogravimetric, atomic absorption, conductivity, and elemental analysis data. Using the Job method, the compositions of these complexes were determined. Under the ligand (H₂L) excess (M:L = 1:1–1:10). In aqueous solutions, a binuclear violet complex Cu₂(HL)₂L(H₂O)₄ is formed, with an octahedral structure. Under comparable amounts of the reagents, in MeOH solutions, a green mononuclear complex Cu(H₂L)Cl₂ is formed. Protonation constants of the H₂L, and stability constants of its Cu²⁺ complexes, were determined by potentiometric titration in H₂O media at 25 ± 0.02 °C under a N₂ atmosphere and ionic strength of 0.1 m NaCl. It has been observed that H₂L has three protonation constants. The divalent metal ion Cu²⁺ forms stable 2:1 and 2:2 complexes with H₂L. The antimicrobial activity studies of the valacyclovir and it’s complexes have been studied against some gram positive species: (Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus, Enterococcus faecalis) and gram negative (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Kluyveromyces fragilis, Saccharomyces cerevisiae, Candida albicans) bacteriaz.     

Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method

In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H₂SO₄/HNO₃/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold.