Microwave-assisted guanidinylation in solid phase peptide synthesis: comparison of various reagents

The guanidinylation of a peptide chain on a polymeric support under microwave conditions using derivatives of thioureas—S-alkylisothioureas, pyrazole-carboxamidine, and guanidine as guanidinylating reagents is described. The best results are obtained with N,N′-di-Z-S-methylisothiourea and N,N′-di-Z(2-Cl)-S-methylisothiourea. It is found that guanidinylation with reagents containing Boc groups is accompanied by side reactions.     

Verteprofin conjugated to gold nanoparticles for fluorescent cellular bioimaging and X-ray mediated photodynamic therapy

Microchimica Acta - Photodynamic therapy (PDT) uses photosensitizers, light and molecular oxygen to generate cytotoxic reactive oxygen species. Its effectiveness is limited to <1 cm...     

Boronated (co)polystyrene: monomer reactivity ratios,thermal behavior and flammability

Chemical modification based on incorporation of flame retardants (FR) into the polymer backbone was used in order to reduce polystyrene flammability. Boronated styrenes such as 4‐vinylphenylboronic acid (StB(OH)₂) and 6‐methyl‐2‐(4‐vinylphenyl)‐1,3,6,2‐dioxazaborocane‐4,8‐dione (StBcyclo) were applied as reactive FR. Homo‐ and copolymers of boronated styrenes and styrene (St) were synthesized with different feed ratios using free radical polymerization. It yielded in series of (co)polymers with various amounts of StB(OH)₂ and StBcyclo (5–20% mol/mol of St). Copolymer compositions were determined by ¹H NMR. The relative reactivity ratios of system St‐StBcyclo were determined by applying the Jaacks method. Glass transition temperature and thermal stability of obtained (co)polymers were determined from DSC and TGA analysis, respectively. The pyrolysis combustion flow calorimeter was applied as a tool for assessing the flammability of the synthesized (co)polymers. Copyright © 2014 John Wiley & Sons, Ltd.     

Spectroscopy and photophysics of dimethyl-substituted alloxazines

We have calculated the electronic structure and absorption spectra from the ground state and the first triplet excited state for five dimethylalloxazines, using the TD-DFT approach. The results of the calculations were correlated to experimental spectral and photophysical data, including the transient spectra reported here containing triplet–triplet absorption data, using the proximity effect theory to explain the variations of the ISC rates with the substitution pattern and solvent. Additionally, singlet oxygen yields were measured for these compounds, demonstrating their high efficiency as singlet oxygen photosensitizers.     

Synthesis, thermal stabilities, and anisotropic properties of some new isoflavone-based esters 7-decanoyloxy-3-(4'-substitutedphenyl)-4H-1-benzopyran-4-ones

A series of new isoflavonic esters 7-decanoyloxy-3-(4'-substitutedphenyl)-4H-1-benzopyran-4-ones containing a heterocycle in their central core with one flexible alkyl chain and various substituents, R (where R = F, Cl, Br, CH₃, OCH₃, or H) at 4'-position at one end, have successfully been synthesised, isolated, and characterised. The physical properties of title compounds were studied using spectroscopic techniques (Fourier transform infrared, ¹H and ¹³C nuclear magnetic resonance). The liquid crystalline properties and the textures of these compounds along with their thermal stabilities were investigated via polarising optical microscopy and differential scanning calorimetry. All the compounds except the member without the substituent were enantiotropic mesogens exhibiting smectic A and/or nematic phases. The layer periodicities in relation to different phases were substantiated by X-ray diffraction wherein the molecules within the SmA phase were found to be intercalated. The structural changes that resulted in a variation of transition temperature as well as the electronic polarisability of the respective compounds are also discussed.     

On Some Concepts of Generalized Differentials

In this paper, we study some concepts of generalized differentials for set-valued maps and introduce some new ones. In particular we first focus on the concept of Generalized Differential Quotients, briefly GDQs. It is shown that minimal GDQs are unique for scalar single-valued functions, then GDQs are compared with contingent and Dini derivatives, finally some other results characterizing GDQs are given. A new definition of generalized differentiation theory is presented, namely weak GDQs that are a modification of GDQs. We clarify the relationships with other concepts of generalized differentiability: Clarke generalized Jacobians, path-integral generalized differentials and Warga derivate containers. Finally, some applications of GDQs end the paper.      

2,2′‐Isopropyl­idene­diphenol

The planar benzene rings in the title compound, C₁₅H₁₆O₂, are inclined at an angle of 82.61 (9)° to one another. There are two intra­molecular hydrogen bonds of types O—H⋯π and C—H⋯O. The mol­ecules are linked by strong O—H⋯O hydrogen bonds into a one‐dimensional network, which is compared with that of related compounds.     

Synthesis and antiviral properties of aza-analogues of ganciclovir derived from 5,5-bis(hydroxymethyl)pyrrolidin-2-one

Novel aza-analogues of ganciclovir were obtained from 1,5,5-tris(pivaloyloxymethyl)pyrrolidin-2-one by a one-pot base silylation/nucleoside coupling procedure. The compounds were evaluated for, but found to be devoid of, antiviral activity in vitro.     

Types of reasoning required in university exams in mathematics

Empirical research shows that students often use reasoning founded on copying algorithms or recalling facts (imitative reasoning) when solving mathematical tasks. Research also indicate that a focus on this type of reasoning might weaken the students’ understanding of the underlying mathematical concepts. It is therefore important to study the types of reasoning students have to perform in order to solve exam tasks and pass exams. The purpose of this study is to examine what types of reasoning students taking introductory calculus courses are required to perform. Tasks from 16 exams produced at four different Swedish universities were analyzed and sorted into task classes. The analysis resulted in several examples of tasks demanding different types of mathematical reasoning. The results also show that about 70% of the tasks were solvable by imitative reasoning and that 15 of the exams could be passed using only imitative reasoning.