scholarly journals Helix-Sense-Selective Polymerization of Phenylacetylenes Having a Porphyrin and a Zinc-Porphyrin Group: One-Handed Helical Arrangement of Porphyrin Pendants

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 274 ◽  
Author(s):  
Masahiro Teraguchi ◽  
Nobuyuki Nahata ◽  
Takahiro Nishimura ◽  
Toshiki Aoki ◽  
Takashi Kaneko
Keyword(s):  
Main Chain ◽  
Helical Structure ◽  
Spatial Arrangement ◽  
Catalyst System ◽  
Cd Spectra ◽  
Absorption Region ◽  
Zinc Porphyrin ◽  
Stacking Effect ◽  
The One ◽  
Porphyrin Moiety

: Newly synthesized two kinds of achiral phenylacetylenes having a free-base- or a zinc-porphyrin (1 and Zn1, respectively) were polymerized by using a chiral rhodium catalyst system, Rh+(nbd)[(η6-C6H5)B–(C6H5)3] catalyst and (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA, respectively) cocatalyst. Poly(1) and poly(Zn1) in THF showed a Cotton signal at the absorption region of the porphyrin and the main chain in the circular dichroism (CD) spectra. This result suggests that poly(1) and poly(Zn1) exist in a conformation with an excess of one-handed helix sense and the porphyrin moiety arranged in chiral helical fashion. The one-handed helical structure of poly(1) could be sustained in a mixture of THF/HMPA (10/2, v/v) due to stabilizing by stacking effect of porphyrin moieties along the main chain. This is the first example about helix-sense-selective polymerization by using Rh+(nbd)[(η6-C6H5)B–(C6H5)3] catalyst. Additionally, poly(Zn1) showed about 10 times larger CD intensity in comparison with poly(1). This result suggests the regularity of arrangement of the porphyrin in poly(Zn1) is higher compared with poly(1). Spatial arrangement of porphyrins was achieved by utilizing a one-handed helical poly(phenylacetylenes) as a template.

scholarly journals Helix-sense-selective Polymerization of 3,5-bis(hydroxymethyl)phenylacetylene Rigidly Bearing Galvinoxyl Residues and Their Chiroptical Properties

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1877 ◽  
Author(s):  
Shi ◽  
Wang ◽  
Teraguchi ◽  
Aoki ◽  
Kaneko
Keyword(s):  
Main Chain ◽  
Helical Structure ◽  
Intramolecular Hydrogen Bonding ◽  
Catalyst System ◽  
Static Stability ◽  
Cotton Effect ◽  
Helical Conformation ◽  
Cd Spectra ◽  
Cotton Effects ◽  
Intramolecular Hydrogen

Four kinds of newly synthesized achiral phenylacetylenes bearing a phenylhydrogalvinoxyl residue at 4-position were polymerized by using a chiral rhodium catalyst system, [Rh(nbd)B(C6H5)4] or [Rh(nbd)Cl]2 catalysts in the presence of chiral (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA) cocatalysts. Poly(m-HGDHPA) and poly(m-HGTHPA) in THF showed Cotton signals at the absorption regions of the main chain and hydrogalvinoxyl in the circular dichroism (CD) spectra. It indicated that excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization (HSSP) under the asymmetric conditions despite the achiral monomer, and the hydrogalvinoxyl moieties were also arranged to form one-handed helical structure. However, there was no Cotton effect for poly(p-HGDHPA) and poly(p-HGTHPA) because the intramolecular hydrogen bonding did not act well to stabilize the helical conformation. The hydrogalvinoxyl units of poly(m-HGDHPA) and poly(m-HGTHPA) were converted to the corresponding galvinoxyl radicals after treatment with PbO2. In the CD spectra of the polyradicals, the Cotton effects decreased depending on their static stability of helical conformation, suggesting that reversal conformation of the polymer chain arose.

Effect of polymerization degree of oligogalacturonates and D-galacturonans on their circular dichroic spectra

1979 ◽  
Vol 44 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Slavomír Bystrický ◽  
Rudolf Kohn ◽  
Tibor Sticzay
Keyword(s):  
Physicochemical Properties ◽  
Aqueous Solutions ◽  
Helical Structure ◽  
Monomeric Unit ◽  
Polymerization Degree ◽  
Cd Spectra ◽  
Circular Dichroic

The CD spectra of aqueous solutions of homopolymeric sodium oligogalacturonates and D-galacturonans of polymerization degree n = 1-64, as well as lower calcium oligogalacturonates (n = 1-5) were measured. Chiroptic properties were correlated with the polymerization degree in terms of optical superposition of monomeric unit increments. Interpretation of obtained data, respecting further physicochemical properties entitles to conclude that the conformation of macromolecules of D-galacturonan in solution is close to helical structure.

From i-doc to VR experience: New forms of user engagement in immersive digital documentaries

2020 ◽  
Vol 17 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Florian Mundhenke
Keyword(s):  
User Experience ◽  
Digital Storytelling ◽  
Computer Game ◽  
Spatial Arrangement ◽  
The Other ◽  
User Engagement ◽  
Audience Research ◽  
Head Mounted Displays ◽  
Digital Formats ◽  
The One

Audience research proves that possibilities of interaction in i-docs are often not fulfilled by the user, who is not really part of a ‘work in progress’ (as intended by the makers). With the shift and development of new digital formats (360-degree-films, nonfictional VR experiences, AR apps), the question of the possible interactive potential should be addressed once again. Since VR projects are fully immersive (mostly using head-mounted displays), there is no possible distraction from outside on the one hand. On the other hand, there is a shift from the computer game style aesthetic of early i-docs, with their pure spatial arrangement of events, to a more inclusive digital storytelling modality with the user experiencing his own world-building. This will be discussed with taking into consideration the non-fictional VR experience as a mode of actively combining immersion and storytelling for a satisfactory user experience. Afterwards two very different examples of nonfictional VR production will be presented, and their modalities will be briefly touched; the utilized approach and its user response will be discussed. A look at the future of possible developments concludes the essay.

scholarly journals Side chain to main chain hydrogen bonds stabilize a polyglutamine helix in the activation domain of a transcription factor

2018 ◽  
Author(s):  
Albert Escobedo ◽  
Busra Topal ◽  
Micha Ben Achim Kunze ◽  
Juan Aranda ◽  
Giulio Chiesa ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Hydrogen Bonds ◽  
Transcriptional Activity ◽  
Main Chain ◽  
Muscular Atrophy ◽  
Helical Structure ◽  
Structural Basis ◽  
Tract Length ◽  
Spinobulbar Muscular Atrophy ◽  
Polyq Tract

Polyglutamine (polyQ) tracts are regions of low sequence complexity of variable length found in more than one hundred human proteins. These tracts are frequent in activation domains of transcription factors and their length often correlates with transcriptional activity. In addition, in nine proteins, tract elongation beyond specific thresholds causes polyQ disorders. To study the structural basis of the association between tract length, transcriptional activity and disease, here we addressed how the conformation of the polyQ tract of the androgen receptor (AR), a transcription factor associated with the polyQ disease spinobulbar muscular atrophy (SBMA), depends on its length. We found that the tract folds into a helical structure stabilized by unconventional hydrogen bonds between glutamine side chains and main chain carbonyl groups. These bonds are bifurcate with the conventional main chain to main chain hydrogen bonds stabilizing α-helices. In addition, since tract elongation provides additional interactions, the helicity of the polyQ tract directly correlates with its length. These findings suggest a plausible rationale for the association between polyQ tract length and AR transcriptional activity and have implications for establishing the mechanistic basis of SBMA.

Construction of polyphosphoesters with the main chain of rigid backbones and stereostructures via organocatalyzed ring-opening polymerization

2020 ◽  
Vol 11 (20) ◽  
pp. 3475-3480
Author(s):  
Yu-Jia Zheng ◽  
Guan-Wen Yang ◽  
Bo Li ◽  
Guang-Peng Wu
Keyword(s):  
Ring Opening ◽  
Main Chain ◽  
Catalyst System ◽  
Ring Opening Polymerization ◽  
System P ◽  
Organic Catalyst

A highly stereoregular polyphosphoester with a rigid cyclohexylene structure in the main chain was constructed via ring-opening polymerization (ROP) in the presence of an organic catalyst system.

Intramolecular photoinduced processes of newly synthesized dual zinc porphyrin-fullerene triad with flexible linkers

2006 ◽  
Vol 10 (12) ◽  
pp. 1380-1391 ◽  
Author(s):  
Mohamed E. El-Khouly ◽  
Jun Hasegawa ◽  
Atsuya Momotake ◽  
Mikio Sasaki ◽  
Yasuyuki Araki ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Photophysical Properties ◽  
Ion Pair ◽  
Reaction Centre ◽  
Polar Solvents ◽  
Time Resolved ◽  
Zinc Porphyrin ◽  
Photosynthetic Antenna ◽  
Porphyrin Moiety ◽  
Photoinduced Processes

Zinc porphyrin-fullerene-zinc porphyrin triad, in which two zinc porphyrin ( ZnP ) moieties and a fullerene ( C 60) moiety are linked by flexible bonds and which is intended to be a working model of the photosynthetic antenna-reaction centre, has been newly synthesized. Its photophysical properties have been investigated by both time-resolved emission and transient absorption techniques. Excitation of the zinc porphyrin moiety of the triad induced charge separation, generating the radical ion pair, in which the electron localizes on the C 60 moiety and the hole localizes on the zinc porphyrin moiety. In polar solvents, the charge-separated states decayed with lifetimes of 300-600 ns returning to the ground state. Compared with ZnP - C 60 dyad, ZnP - C 60- ZnP triad showed longer lifetimes for the radical ion pair due to the conformation of the two ZnP moieties. The effects of the coordinating reagents on the zinc atom have been studied, with the expectation of conformational change of the two ZnP moieties with respect to C 60.

Modification of V2O5-WO3/TiO2 Catalysts Supported on SiC Filter for NO Reduction at Low Temperature

2007 ◽  
Vol 124-126 ◽  
pp. 1713-1716 ◽  
Author(s):  
Youn Gae Kim ◽  
Joo Hong Choi ◽  
Liang Yu ◽  
Young Cheoul Bak
Keyword(s):  
No Reduction ◽  
Catalyst System ◽  
Ceramic Filter ◽  
Commercial Catalyst ◽  
Scr Catalyst ◽  
Catalytic Filter ◽  
Temperature Window ◽  
Face Velocity ◽  
The One ◽  
Optimum Working

The catalytic filter, a ceramic filter supported SCR catalyst, is a promising material for treating particulates and NOX simultaneously. Recently, it is found that a SiC filter supported V2O5- WO3-TiO2 [commercial catalyst system] shows a reasonable SCR activity around 320 °C [1]. In order to improve its catalytic activity at low temperatures, the effects of Pt and MnOX addition on the catalytic filter are investigated. The macro-porous TiO2 film was firstly coated on the pore surface of SiC filter element using the solution composed of the preformed TiO2 particles (P25). Catalytic filters were prepared by the impregnation of TiO2 coated-SiC filter in the solution containing the catalyst components. The MnOX-added catalytic filter showed very wide temperature window from 150-340 °C, providing NX slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s. Pt added-catalytic filter shifted the optimum working temperature towards the lower temperatures (180-240 °C) compared to the one without Pt (280-330 °C). It is understood that MnOX in the catalyst system roles as the main catalyst component while Pt rose as a electron modification additive.

Bi(TFA)3 immobilized in [nbpy]FeCl4: An efficient catalyst system for the one-pot synthesis of 4,6-diarylpyrimidin-2(1H)-ones

2006 ◽  
Vol 7 (9) ◽  
pp. 713-716 ◽  
Author(s):  
Ahmad R. Khosropour ◽  
Iraj Mohammadpoor-Baltork ◽  
Hamid Ghorbankhani
Keyword(s):  
Catalyst System ◽  
One Pot ◽  
Efficient Catalyst ◽  
One Pot Synthesis ◽  
The One

scholarly journals Telomerization of Vinyl Chloride with Chloroform Initiated by Ferrous Chloride-Dimethylacetamide under Ultrasonic Conditions

2015 ◽  
Vol 2015 ◽  
pp. 1-4
Author(s):  
Hua Qian ◽  
Hengdao Quan
Keyword(s):  
Reaction Time ◽  
Vinyl Chloride ◽  
Ultrasonic Irradiation ◽  
Catalyst System ◽  
Ferrous Chloride ◽  
Efficient Catalyst ◽  
The One ◽  
Ultrasonic Conditions

Telomerization of vinyl chloride with chloroform was investigated using ferrous chloride-dimethylacetamide system, and 42.1% yield, more than four times the one reported before, was achieved. The addition of ultrasound further improved the reaction and yield was raised to 51.9% with trace byproducts at highly reduced reaction time and temperature. Ferrous chloride-dimethylacetamide under ultrasonic irradiation acts as a very efficient catalyst system for the 1 : 1 telomerization.

Solution Conformation of Konjac Glucomannan Single Helix

2011 ◽  
Vol 197-198 ◽  
pp. 96-104 ◽  
Author(s):  
Chao Wang ◽  
Yu Zhang ◽  
Hong Xia Huang ◽  
Mao Bin Chen ◽  
Dong Sheng Li
Keyword(s):  
Congo Red ◽  
Helical Structure ◽  
Konjac Glucomannan ◽  
Helical Conformation ◽  
Urea Solution ◽  
Cd Spectra ◽  
Solution Conformation ◽  
Random Coils ◽  
The Stability ◽  
Single Helix

The possibility of the existence of konjac glucomannan (KGM) single helix in dilute solution was discussed finely by ultraviolet-visible spectrophotometer (UV-Vis) with Congo red complex, viscosimetry and circular dichroism (CD). KGM bound to Congo red and the λmaxcharacteristic shifted markedly to longer wavelength (514 nm) in 0.25 M aq NaOH. The shifts of λmaxand intrinsic viscosity were also compared in different mediums, such as different concentrations of KGM, NaOH, urea solutions or temperatures. The results indicated that KGM had an ordered, single-helical conformation in neutral, slight NaOH (<0.15 M) and urea (<3.0 M) solutions or at a moderate temperature (T<55ºС ), while it was transformed disorder, random coils in high NaOH (>0.45 M), urea (>4.0 M) solutions or at a high temperature (T>60ºС ). So it can be conclude that the outside factors play an important role on the stability of the single-helix conformation for KGM solution. The induced CD spectra by Congo red and the CD spectra of KGM in aqueous and urea solution indicated further that KGM had a single-helical structure. The new conclusion laid the foundation of determining helical radius, pitch and length of KGM in the future studies.

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