Symmetric Substitution Research Articles

Spectroscopic properties of diketopyrrolopyrrole derivatives with long alkyl chains

The diketopyrrolopyrrole derivatives with long alkyl chains were synthesised and spectrally characterised. Experimental spectroscopic techniques were supplemented by the DFT calculations of equilibrium geometries, normal mode frequencies and time-dependent DFT simulated UV–vis spectra. Comparison between the symmetrical and unsymmetrical substitution of alkyl chains resulted in some changes like bathochromic shift of absorption, excitation and emission spectra, significant reduction of molar absorption coefficient in UV–vis range, increase of fluorescence quantum yield, and slight increase of fluorescence lifetimes. The influence of the length of the alkyl chain on the properties of material was also discussed. The experimental spectroscopic data together with the calculated results show that presence of the alkyl substituent at the nitrogen atom influences more on the properties of the investigated DPPs than the length of attached chain.

Thermoresponsive Corannulene

We demonstrate herein that corannulene, a bowl‐shaped polycyclic aromatic hydrocarbon, can assemble into larger supramolecular structures in water through a change in the solution temperature. This property is invoked through a simple five‐fold symmetric substitution of the corannulene nucleus with triethylene glycol units. Interestingly, an increase in the solution temperature, which triggers the assembly process, also enhances the fluorescence emission properties of the assembled materials. Although the emission remains very weak in solution, bright green luminescence can be observed in the fibrilar form. This unexpected and interesting behavior indicates that the corannulene nucleus presents a new motif for the design of aggregation‐induced emission (AIE) based luminogens. To the best of our knowledge, this is the first report of a thermoresponsive nonplanar polycyclic hydrocarbon derivative that can respond to a thermal trigger and assemble into larger emissive structures.

Blurred Boundaries: A Flexible Approach for Segmentation Applied to the Car Market

Prominent features of differentiated product markets are segmentation and product proliferation that blurs the boundaries between segments. I develop a tractable demand model,the Ordered Nested Logit, which allows for over lap between neighboring segments.I apply the model to the automobile market where segments are ordered from small to luxury. I find that consumers, when substituting outside their vehicle segment, are more likely to switch to a neighboring segment. Accounting for such a symmetric substitution matters when evaluating the impact of new product introduction or studying the effect of subsidies on fuel-efficient cars.

Structure-activity relationship of the inhibitory effects of flavonoids on nitric oxide production in RAW264.7 cells

We isolated flavonoids from herbal specimens from the Tibetan region (Sophora yunnanensis and Rhodiola sacra) that suppress nitric oxide (NO) production in macrophages stimulated by lipopolysaccharide and interferon-γ. The isolated flavonoids carry symmetric substitutions in the B ring (R3′=R5′). We analyzed the quantitative structure-activity relationship of the inhibitory activity by comparative molecular field analysis (CoMFA) using this series of flavonoids. Use of flavonoids with symmetrical substitutions in the B ring made it simpler to align molecules because it was not necessary to consider a huge number of combinations due to the B-ring conformation. The CoMFA model, whose cross-validated q2 value was 0.705, suggested the existence of a hydroxy group at the 5-position, the choice of the A/C-ring scaffold (chromane or chromene) and electrostatic field around the B ring are important for NO inhibitory activity. Flavonoids synthesized based on the CoMFA model exhibited significant inhibitory potential against NO production, validating the predictive capability of the CoMFA model.

Research on spatiotemporal spread of avian influenza A(H7N9) virus based on discrete geographic information

Objective: To establish a dynamic spatiotemporal spread modes of influenza A (H7N9) virus by using discrete geographic information and explore the spatiotemporal transmission of the virus. Methods: The gene sequences of H7N9 virus isolated from human in China, which were available from Global Initiative on Sharing Avian Influenza Data (GISAID), were used in alignment by using software BioEdit 7.0. Spatiotemporal spread model of H7N9 virus was established in a Bayesian statistical framework by using software BEAST 1.8.2. The symmetric substitution model and Bayesian stochastic search variable selection (BSSVS) were used to infer and verify the historical transmission route of H7N9 virus. Finally the spatiotemporal transmission route was presented by Google Earth software. Results: The transmission of avian influenza A (H7N9) virus originated in Shanghai and Hangzhou, and can be dated back to October 2012. In March and April 2013, it began to spread to the neighboring provinces. The transmission speed up in August and September and affected more than ten geographic positions within 3 months. Conclusion: Based on gene sequences and spatial geographic information, the transmission route of H7N9 virus was traced, which would support the avian influenza prevention and control as well as avian influenza virus tracing.

Two new threitol orsellinates from a sea mud-derived fungus, Ascotricha sp. ZJ-M-5

Two new d-threitol orsellinates (1–2) were isolated from the EtOAc extract of a sea mud-derived fungus, Ascotricha sp. ZJ-M-5, cultured in Czapek Dox broth. These two compounds featured in the symmetrical substitution of orsellinic acid or acetic acid, which was established on the basis of 1D and 2D NMR experiments. The characteristic optical rotations enabled the assignment of the absolute configuration.

Development of macaronic Hindi-English 'Hinglish' text message content for a coronary heart disease secondary prevention programme.

Coronary heart disease (CHD) is a leading cause of morbidity and mortality in India. Text message based prevention programs have demonstrated reduction in cardiovascular risk factors among patients with CHD in selected populations. Customisation is important as behaviour change is influenced by culture and linguistic context. To customise a mobile phone text message program supporting behaviour and treatment adherence in CHD for delivery in North India. We used an iterative process with mixed methods involving three phases: (1) Initial translation, (2) Review and incorporation of feedback including review by cardiologists in India to assess alignment with local guidelines and by consumers on perceived utility and clarity and (3) Pilot testing of message management software. Messages were translated in three ways: symmetrical translation, asymmetrical translation and substitution. Feedback from cardiologists and 25 patients was incorporated to develop the final bank. Patients reported Hinglish messages were easy to understand (93%) and useful (78%). The software located in Australia successfully delivered messages to participants based in Delhi-surrounds (India). Our process for customisation of a text message program considered cultural, linguistic and the medical context of potential participants. This is important in optimising intervention fidelity across populations enabling examination of the generalisability of text message programs across populations. We also demonstrated the customised program was acceptable to patients in India and that a centralised cross-country delivery model was feasible. This process could be used as a guide for other groups seeking to customise their programs. TEXTMEDS Australia (Parent study)-ACTRN 12613000793718.

Electronic and optical properties of hexathiapentacene in the gas and crystal phases

Using density functional theory (DFT) and its time-dependent (TD) extension, the electronic and optical properties of the hexathiapentacene (HTP) molecule, a derivative of pentacene (PNT) obtained by symmetric substitution of the six central H atoms with S atoms, are investigated for its gas and solid phases. For the molecular structure, all-electron calculations are performed using a Gaussian localized orbital basis set in conjunction with the Becke three-parameter Lee-Yang-Parr (B3LYP) hybrid exchange-correlation functional. Electron affinities, ionization energies, quasiparticle energy gaps, optical absorption spectra, and exciton binding energies are calculated and compared with the corresponding results for PNT, as well as with the available experimental data. The DFT and TDDFT results are also validated by performing many-body perturbation theory calculations within the $GW$ and Bethe-Salpeter equation formalisms. The functionalization with S atoms induces an increase of both ionization energies and electron affinities, a sizable reduction of the fundamental electronic gap, and a redshift of the optical absorption onset. Notably, the intensity of the first absorption peak of HTP falling in the visible region is found to be nearly tripled with respect to the pure PNT molecule. For the crystal structures, pseudopotential calculations are adopted using a plane-wave basis set together with the Perdew-Burke-Ernzerhof exchange-correlation functional empirically corrected in order to take dispersive interactions into account. The electronic excitations are also obtained within a perturbative B3LYP scheme. A comparative analysis is carried out between the ground-state and excited-state properties of crystalline HTP and PNT linking to the findings obtained for the isolated molecules.

Red to Near-Infrared Isoindole BODIPY Fluorophores: Synthesis, Crystal Structures, and Spectroscopic and Electrochemical Properties.

A series of high-performance fluorophores named isoindole boron dipyrromethenes (BODIPYs) containing either symmetrical or unsymmetrical alkyl substitution patterns on pyrrole rings were synthesized by an efficient process and were characterized by X-ray diffraction and spectroscopic and electrochemical analyses. Most of these dyes show strong, sharp absorption and bright fluorescence emission in the red to near-infrared (NIR) region (up to 805 nm in acetonitrile). Pyrrolic alkyl substitutions lead to increases in the HOMO and LUMO energy levels and an overall decrease in the energy band gaps of the dye. Among the 23 isoindole BODIPY dyes synthesized, solvent-dependent fluorescence emission and lifetime decay were only observed for those containing a 3-methyl substituent on the uncoordinated pyrrole ring, whereas little variation in the fluorescence intensity was observed for the rest of the dyes upon changing the polarity of the solvent. These resultant dyes can be further functionalized via the Knoevenagel condensation on the α-methyl substituent of the chromophore to install a variety of functionalities, including a dimethylamine group demonstrated in this work. This dimethylamine-functionalized isoindole BODIPY shows weak fluorescence at 805 nm in acetonitrile and a ratiometric "turn-on" NIR fluorescence response to decreasing pH.

Matrix group structure and Markov invariants in the strand symmetric phylogenetic substitution model.

We consider the continuous-time presentation of the strand symmetric phylogenetic substitution model (in which rate parameters are unchanged under nucleotide permutations given by Watson-Crick base conjugation). Algebraic analysis of the model's underlying structure as a matrix group leads to a change of basis where the rate generator matrix is given by a two-part block decomposition. We apply representation theoretic techniques and, for any (fixed) number of phylogenetic taxa L and polynomial degree D of interest, provide the means to classify and enumerate the associated Markov invariants. In particular, in the quadratic and cubic cases we prove there are precisely [Formula: see text] and [Formula: see text] linearly independent Markov invariants, respectively. Additionally, we give the explicit polynomial forms of the Markov invariants for (i) the quadratic case with any number of taxa L, and (ii) the cubic case in the special case of a three-taxon phylogenetic tree. We close by showing our results are of practical interest since the quadratic Markov invariants provide independent estimates of phylogenetic distances based on (i) substitution rates within Watson-Crick conjugate pairs, and (ii) substitution rates across conjugate base pairs.

Aggregation-induced emission type thermally activated delayed fluorescent materials for high efficiency in non-doped organic light-emitting diodes

Aggregation-induced emission (AIE) type thermally activated delayed fluorescent (TADF) emitters were developed by asymmetric substitution of donor moieties to a diphenylsulfone acceptor. The AIE properties of the TADF emitters increased the quantum efficiency of the non-doped TADF devices and asymmetric substitution was more effective than symmetric substitution to enhance the quantum efficiency of the non-doped devices.

Dipole Moment Effect of Cyano-Substituted Spirofluorenes on Charge Storage for Organic Transistor Memory

As a fascinating information storage device, organic transistor memory based on molecular charge storage elements (MCSEs) has attracted great research interest. However, the charge storage mechanism of MCSEs is ambiguous due to their complex charge dynamic behaviors. Herein, the dipole moment effects on the charge trapping process and the performance of transistor memory are revealed based on cruciform spiro[fluorene-9,9′-xanthene] (SFXs), incorporating cyano moieties, as the typical electron-withdrawing substitution. The characterization of electrostatic potential (ESP) calculation, UV–vis, photoluminescence, and crystallography of SFXs shows the SFXs MCSEs with weaker dipole moment through symmetrical substitution. A series of prototype transistor memories based on SFXs exhibit an erasable type feature with smart photoresponsive behavior. The weaker dipole moment ones possess larger memory window (∼40 V), higher charge trapping density (>1 × 1013 cm–2), and higher programming speed (1014–1011 cm–2 s–1)....

Who’s Who?: Direct Belief and Symmetrical Substitution

According to Jonathan Berg’s Theory of Direct Belief, a belief about some individual is an unmediated dyadic relation between the believer and that individual. Berg’s thesis incorporates a Millian account of proper names, and invokes conversational implicature to explain well-known anti-substitution intuitions. In this critical note, I present a puzzle for the Theory of Direct Belief involving symmetrical substitution in false identity belief reports.

Polybenzimidazole-based polymeric ionic liquids (PILs): Effects of ‘substitution asymmetry’ on CO2 permeation properties

Polymeric Ionic Liquids (PILs) are being considered as promising membrane materials for CO2 separation. Present work aims at investigating effects substitution asymmetry on imidazole moiety of two structurally different polybenzimidazoles (PBI-BuI and PBI-HFA) on physical, gas sorption and transport properties of the resulting film forming PILs possessing symmetric substitution, while keeping one of the N-substituent as methyl group. PILs were obtained with high degree of substitution. The halide anion of these PILs was exchanged with BF4¯, Tf2N¯ and HFB¯ anions. Effects of substituents, cationic backbone and type of anions on gas permeation properties of PILs using pure gases (He, H2, N2 and CO2) were examined at 20atm upstream pressure and correlated with their physical properties. Combination of typical ionic liquid character (effective towards enhancing CO2 sorption) and looser chain packing (ease in gas diffusion) offered improved CO2 permeation characteristics. As an outcome, some of the PILs exhibited higher CO2 permeation than that of hydrogen, typically known as ‘reverse selectivity’. These asymmetrically substituted PILs enhanced not only the gas permeability, but also selectivity than their symmetrically substituted counterparts.

Genome evolution by transformation, expansion and contraction (GETEC)

We propose here the GETEC (Genome Evolution by Transformation, Expansion and Contraction) model of gene evolution based on substitution, insertion and deletion of genetic motifs. The GETEC model unifies two classes of evolution models: models of substitution, insertion and deletion of nucleotides as function of time (Lèbre and Michel, 2010) and sequence length (Lèbre and Michel, 2012), and models of symmetric substitution of genetic motifs as function of time (Benard and Michel, 2011). Evolution of genetic motifs based on substitution, insertion and deletion is modeled by a differential equation whose analytical solutions give an expression of the genetic motif occurrence probabilities as a function of time or sequence length, as well as in direct time direction (past–present) or inverse time direction (present–past). Evolution models with “substitution only”, i.e. without insertion and deletion, and with “insertion and deletion only”, i.e. without substitution, are particular cases of the GETEC model. We have also developed a research software for computing the analytical solutions of the GETEC model. It is freely accessible at http://icube-bioinfo.u-strasbg.fr/webMathematica/GETEC/ or via the web site http://dpt-info.u-strasbg.fr/∼michel/.

Hiding Messages using Musical Notes: A Fuzzy Logic Approach

“Music can be used as a communicable language”. Musical symbols and musical notes have been used as codes and ciphers from early days. The art of encrypting messages using music is termed as Musical cryptography and it uses predefined set of notes and set of rules for composing musical pieces which in turn are musical cryptograms. Traditional algorithms applied to musical cryptography used simple substitution cipher which merely produced good musical sequences. To overcome this problem a fuzzy logic based algorithm for musical cryptography is proposed in this paper. The paper proposes a symmetric key substitution cipher which uses one of the n candidate notes to encrypt a particular character. The application of fuzzy logic in musical cryptography produces acceptable musical sequences which are hard to be suspected as cipher.

Metal‐Free Reagent Dependent SS and CC Homocoupling of α‐Enolic Dithioesters at Room Temperature: Direct Access to Fully Substituted Symmetrical Thiophenes via Chemoselective Paal–Knorr Approach

AbstractAn unprecedented metal‐free oxidative homodimerization of α‐enolic dithioesters has been achieved for the first time at room temperature within 5–10 min. Molecular iodine promotes the SS coupling leading to S,S′‐bis(dithioacetals), while N‐chlorosuccinimide facilitates CC coupling to give α,α′‐bis(β‐oxo dithioesters) in good to excellent yields. Furthermore, the newly generated α,α′‐bis(β‐oxo dithioesters) have been directly employed in the synthesis of fully substituted thiophenes with a unique symmetrical substitution pattern in a one‐pot, two‐step reaction sequence.magnified image

Mitigation of Surface Aggregation in Modified Phthalocyanines as Potential Photo Sensitizers

ABSTRACTImportant to the development of dye-sensitized solar cells is the longevity and photo-conversion efficiency of the dye. To improve cost effectiveness, dyes of superior thermal and chemical stability are desirable to extend device performance. In this study, we examine a series of peripherally fluorinated Zinc-Phthalocyanines (FxZnPc). Introduction of chemically inert fluorine and isopropyl fluoroalkyl groups on the periphery of the Pc improve the dye stability and allow for tunable photo-physical properties. Additionally, introduction of the bulky isopropyl fluoroalkyl groups help mitigate molecular aggregation in thin films which is known to be detrimental to maintaining the desired photo-physical properties of the surface coating. Using molecular dynamics and first principles modeling, various substituent effects on surface adhesion and aggregation over TiO2 surfaces are characterized for both symmetric and asymmetric substitution.

Phylogeography of the current rabies viruses in Indonesia.

Rabies is a major fatal zoonotic disease in Indonesia. This study was conducted to determine the recent dynamics of rabies virus (RABV) in various areas and animal species throughout Indonesia. A total of 27 brain samples collected from rabid animals of various species in Bali, Sumatra, Kalimantan, Sulawesi, Java, and Flores in 2008 to 2010 were investigated. The cDNA of the nucleoprotein gene from each sample was generated and amplified by one-step reverse transcription-PCR, after which the products were sequenced and analyzed. The symmetric substitution model of a Bayesian stochastic search variable selection extension of the discrete phylogeographic model of the social network was applied in BEAST ver. 1.7.5 software. The spatial dispersal was visualized in Cartographica using Spatial Phylogenetic Reconstruction of Evolutionary Dynamics. We demonstrated inter-island introduction and reintroduction, and dog was found to be the only source of infection of other animals. Ancestors of Indonesian RABVs originated in Java and its descendants were transmitted to Kalimantan, then further to Sumatra, Flores, and Bali. The Flores descendent was subsequently transmitted to Sulawesi and back to Kalimantan. The viruses found in various animal species were transmitted by the dog.

Design of chemically stable, potent, and efficacious MDM2 inhibitors that exploit the retro-mannich ring-opening-cyclization reaction mechanism in spiro-oxindoles.

Inhibition of the MDM2–p53 protein–protein interaction is being actively pursued as a new anticancer therapeutic strategy, and spiro-oxindoles have been designed as a class of potent and efficacious small-molecule inhibitors of this interaction (MDM2 inhibitors). Our previous study showed that some of our first-generation spiro-oxindoles undergo a reversible ring-opening-cyclization reaction that, from a single compound in protic solution, results in an equilibrium mixture of four diastereoisomers. By exploiting the ring-opening-cyclization reaction mechanism, we have designed and synthesized a series of second-generation spiro-oxindoles with symmetrical pyrrolidine C2 substitution. These compounds undergo a rapid and irreversible conversion to a single, stable diastereoisomer. Our study has yielded compound 31 (MI-1061), which binds to MDM2 with Ki = 0.16 nM, shows excellent chemical stability, and achieves tumor regression in the SJSA-1 xenograft tumor model in mice.