Design and synthesis of alpha-helical peptides and mimetics

The alpha-helix is the most abundant secondary structural element in proteins and is an important structural domain for mediating protein-protein and protein-nucleic acid interactions. Strategies for the rational design and synthesis of alpha-helix mimetics have not matured as well as other secondary structure mimetics such as strands and turns. This perspective will focus on developments in the design, synthesis and applications of alpha-helices and mimetics, particularly in the last 5 years. Examples where synthetic compounds have delivered promising biological results will be highlighted as well as opportunities for the design of mimetics of the type I alpha-helical antifreeze proteins.     

Comparison of HDS of Dibenzothiophene and HDN of Quinoline Over Supported MO and CoMo Nitrided and Sulfided Catalysts

Catalytic activities of sulfided and nitrided forms of alumina supported molybdenum as well as cobalt-molybdenum catalysts were compared in the reactions of hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of quinoline. Effect of catalyst composition as well as of the method of its activation on the reaction pathways and catalyst selectivity is discussed.     

Spectroscopy and photophysics of methylphenylsiloxaneand diphenylsiloxane-based molecules and polymers

Spectroscopy and photophysics of various types of methylphenylsiloxane- and diphenylsiloxane-based oligomers and polymers are reviewed. The molecules treated here include homopolymers such as poly(methylphenylsiloxane) and copolymers such as poly(dimethylsiloxane-codiphenylsiloxane) as well as related oligomers or molecules such as diphenyltetramethyldisiloxane. These polymers and oligomers normally exhibit monomer fluorescence in fluid solution at temperatures near room temperature, and the monomer fluorescence and phosphorescence in rigid matrices at 77 K. In addition to these emissions, the excimer fluorescence is often observed depending on the molecular structure of the siloxanes. These emission properties are rationalized based on the molecular structure and kinetics of the excimer formation processes as well as on the flexibility of the Si-O-Si bonds.     

Preparation and application of cellular and nanoporous carbides

A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review.     

Structure and properties of single complex macromolecules and of related bulk systems

Structure and dynamics of complex macromolecules in computer simulated systems is analyzed. The algorithm based on cooperative molecular rearrangements is applied to various macromolecular structures represented in a simplified form on the lattice. Various macromolecular architectures such as linear chains, stars, dendrimers, bottle‐brush polymers as well as cyclic chains and catenane are considered both as single molecules and as dense systems corresponding to polymer melts. A broad range of structural parameters characteristic for each system is taken into account. In some cases, the simulation results are compared with the behavior of real systems in which the structure and dynamics has been studied by X‐ray scattering and mechanical spectroscopy, respectively.     

Transformations of chromanol and tocopherol and synthesis of ascorbate conjugates

α-Tocopherol and as a model compound pentamethylchromanol could be transferred into simple and more complex 5a-ether derivatives including galactopyranose as well as ascorbic acid conjugates. Following elaboration of a glucopyranoside spacer element this could be used for tethering the vitamin E and the vitamin C components to give novel conjugates for subsequent biostudies concerning their proposed synergism of antioxidant properties in tissues.     

Glycolate and Thioglycolate Complexes of Rhenium and Their Oxidative Elimination of Ethylene and of Glycol

Selenium dioxide and osmium tetroxide are effective reagents and catalysts for olefin oxidation, although, owing to their toxicity, reservations remain as to their applicability.^[1] We are therefore seeking more easily handled metal oxides that are soluble in organic solvents and that are as effective as osmium tetroxide in carrying out stereospecific cis hydroxylation of olefins. The rhenium(VII ) oxide 1 , which has meanwhile become readily accessible, is a favorable candidate.^[2]     

负载型碱催化剂的制备及其在酯交换和醇、胺羰化反应中应用

以三乙胺和甲醇钠为活性碱组分,以Ａ,Ｘ和Ｙ型分子筛及硅胶和有机高聚物担体为载体制备了负载型碱性催化剂。考察了催化剂在甲醇和二乙胺羰化以及酯交换反应中的活性,并考察了催化剂制备过程中多种因素对活性的影响,结果表明,在催化剂制备过程中,溶剂和制备方法对催化剂活性的影响较大,而载体粒度的影响较小,在适当的条件下,上述载体能较好地负载有机碱三乙胺和甲醇钠,所得负载型碱性催化剂在环氧丙烷作用下具有较高的甲醇和二乙胺羰化催化活性及酯交换催化活性。     

Structure and mechanism of the deposition of multilayers of polyelectrolytes and nanoparticles

MD simulation of the layer-by-layer assembly of polyelectrolytes (PEs) and nanoparticles (NPs) revealed that the assembly process is electrostatically driven with alternating charge reversal and an overcompensation mechanism. Layers were observed to grow in the lateral direction as well as in a direction normal to the surface. Weakly adsorbed PE molecules were observed to desorb from the flat and NP surfaces. Those molecules are attracted by suspended NPs in solution. PE molecules do not only pull NPs toward the surface but bridge NPs both in solution and on the surface, forming agglomerates and islands. The first double layer differs in structure from the second double layer as a result of strong adsorption of the PE molecules to the rigid surface.     

Synthesis and Optical and Redox Properties of Symmetric and Asymmetric BODIPYs

Herein, we present the synthetic route and the photophysical, electrochemical as well as laser properties of novel red‐emitting boron‐dipyrromethenes (BODIPYs) bearing arylethyne moieties. Such functionality is added along the main axis of the chromophore leading to single‐ and double‐substituted derivatives. The relationship between the dye structure and the lasing properties is studied in detail with the help of the photophysical and electrochemical properties as well as quantum mechanical simulations. The asymmetric substitution of the parent dye induces inhomogeneities in the charge distribution, which leads to an overall loss of the fluorescence capacity, mainly in polar media. Such non‐radiative deactivation processes can be softened by decreasing the electron‐donor ability of the substituent or even avoided by symmetrical substitution. Thus, grafting of the arylethyne moieties at the longitudinal axis of the indacene core results in an effective strategy to develop red‐edge BODIPYs with highly efficient and photostable laser emission.     

Identification and properties of the 1La and 1Lb states of pyranine

The spectroscopic locations of the 1La and 1Lb electronic states of pyranine (1-hydroxy-3,6,8-pyrenetrisulfonic acid, commonly referred to as HPTS), as well as several related compounds, are found using magnetic circular dichroism spectroscopy as well as absorption and fluorescence spectroscopies. These electronic states have been discussed in connection with the photoacid properties of HPTS. Polarization selective fluorescence spectroscopy is used to identify the transition dipole directions of the electronic states of the compounds studied. The issue of the origin for the changes in vibronic structure of HPTS in different solvents is addressed. It is demonstrated that a Brownian oscillator model, in which the strength of the coupling of the electronic states to the solvent changes with solvent, is sufficient to reproduce the trends in the shapes of the vibronic structure.     

Synthesis and Applications of Peptides and Peptidomimetics in Drug Discovery

Peptides are described as naturally occurring short chains of amino acids and offer great potential as therapeutic agents because of their target selectivity, safe, and well tolerable. Hence, there is an increased interest in peptides in pharmaceutical research and development and approximately more than 170 peptide therapeutics are currently being evaluated in clinical trials and many are being used as therapeutic drugs for various diseases including COVID-19. The present Review article focuses on recent progress in peptide drug discovery and advancements in synthetic methodologies to enhance their stability and physiological activity of peptides and as well peptidomimetics.     

Simultaneous spectrophotometric determination of molybdenum and selenium,and of molybdenum and tellurium

A method is reported for the extraction of molybdenum-phenylfluorone by chloroform. The extraction is complete whether perchlorate ions are present or not but the extractions in the presence of perchlorate ions gave a somewhat more sensitive procedure for the spectrophotometric determination of molybdenum in the solvent phase as the molybdenum-phenylfluorone complex.A procedure is reported for the simultaneous determination of molybdenum and selenium, and molybdenum and tellurium. The method involves first the formation and solvent extraction of the molybdenum-phenylfluorone complex by chloroform in the presence of perchlorate ions, followed by determination of selenium in the remaining aqueous phase as selenium-diethyldithiocarbamate complex after solvent extraction with 2-ethyl-1-hexanol in the presence of perchlorate ions. A similar procedure is reported for the simultaneous determination of molybdenum and tellurium except that in the determination of molybdenum, the phenylfluorone complex is extracted by chloroform in the absence of perchlorate ions. Tellurium is determined in the remaining aqueous phase as tellurium-diethyldithiocarbamate complex after solvent extraction by 2-ethyl-1-hexanol solvent extraction in the presence of perchlorate ions.     

Synthesis and Properties of Ruthenium-Coordinated Block Copolymers of 2-Vinylpyridine and Carbazole Derivatives

ABA triblock copolymers consisting of different carbazole-containing blocks and ruthenium complexes were designed with respect to their energy-transfer behavior. The number of 2-vinylpyridine (2VP) units in a polymer chain was tailored from 0 to 20 to observe the size effect of the metal complex as a luminophore or as a luminescence quencher. Photoluminescence and optical absorption measurements as well as the intermolecular energy transfer in the block copolymers were studied. Evidence is provided for a fast energy transfer from carbazole to the ruthenium-coordinated 2VP.     

Synthesis and autoconversions of furanthiols and -selenols

Furanthiols and selenols have been synthesized by a modified procedure via organolithium derivatives, with the formation of trimethylsilyl ethers as intermediate products. It has been shown that the thiols as well as the selonols undergo autoconversions when standing in air and in the presence of triethylamine with the formation of furylthio-(seleno)-substituted thio-(seleno)-butyrolactones.Institute of Organic Chemistry, Irkutsk 664033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 891–895, July, 1994. Original article submitted June 2, 1994.     

Infrared and Raman imaging of biological and biomimetic samples

Established methods for imaging of biological or biomimetic samples, such as fluorescence and optical microscopy, magnetic resonance imaging (MRI), X-ray tomography or positron emission tomography (PET) are currently complemented by infrared (both near-IR and mid-IR) as well as Raman spectroscopic imaging, whether it be on a microscopic or macroscopic scale. These vibrational spectroscopic techniques provide a wealth of information without a priori knowledge of either the spectral data or the composition of the sample. Infrared radiation does not harm the organism, no electric potential needs to be applied, and the measurements are not influenced by electromagnetic fields. In addition, no extrinsic labeling or staining, which may perturb the system under investigation, has to be added. The immense volume of information contained in spectroscopic images requires multivariate analysis methodologies in order to effectively mine the chemical and spatial information contained within the data as well as to analyze a time-series of images in order to reveal the origin of a chemical or biochemical process. The promise and limitations of this new analytical tool are surveyed in this review.     

柔红霉素和阿霉素自旋标记衍生物的合成与抗肿瘤活性

合成了5个新的柔红霉素及阿霉素的氮氧自由基自旋标记衍生物(5_9),经元素分析,IR,MS和ESR分析确证了其组成和结构,并对它们进行了抑制小鼠白血病P388、小鼠黑色素癌B16、人胃腺癌MGC和人肝癌SMMC7721细胞的体外筛选.初步药理试验表明,化合物5_9对4种瘤株均有一定的抑制活性,其中化合物9的活性与阿霉素相当.     

Enzymatic oligomerization and polymerization of arylamines: state of the art and perspectives

The literature concerning the oxidative oligomerization and polymerization of various arylamines, e.g., aniline, substituted anilines, aminonaphthalene and its derivatives, catalyzed by oxidoreductases, such as laccases and peroxidases, in aqueous, organic, and mixed aqueous organic monophasic or biphasic media, is reviewed. An overview of template-free as well as template-assisted enzymatic syntheses of oligomers and polymers of arylamines is given. Special attention is paid to mechanistic aspects of these biocatalytic processes. Because of the nontoxicity of oxidoreductases and their high catalytic efficiency, as well as high selectivity of enzymatic oligomerizations/polymerizations under mild conditions—using mainly water as a solvent and often resulting in minimal byproduct formation—enzymatic oligomerizations and polymerizations of arylamines are environmentally friendly and significantly contribute to a “green” chemistry of conducting and redox-active oligomers and polymers. Current and potential future applications of enzymatic polymerization processes and enzymatically synthesized oligo/polyarylamines are discussed.