Scope and limitations of ruthenium-catalyzed metathesis of simple polymer-bound alkenes

2001 ◽  
Vol 79 (5-6) ◽  
pp. 1049-1057 ◽  
Author(s):  
Peter G Breed ◽  
James A Ramsden ◽  
John M Brown
Keyword(s):  
Primary Alcohol ◽  
Butyl Ester ◽  
Operating Conditions ◽  
Allyl Ether ◽  
Side Chain ◽  
Ether Linkage ◽  
First Case ◽  
Gel Phase ◽  
Reduced Mobility ◽  
C Nmr

Synthetic procedures for the preparation of two types of functional resin are described, both based on 2% cross-linked polystyrene with a high density (>60%) of side-chains and terminated by a primary alcohol. In the first case the C11 side-chain is linked to the polymer through a sulfide, and in the second an ether linkage is employed to incorporate a (CH2CH2O)4 unit. In both cases the resins have 13C NMR spectra that are informative in the chain terminus region without special operating conditions. Model intermolecular metathesis reactions were carried out on allylcarbamic acid tert-butyl ester and various alkenes with Grubbs' catalyst. On the basis of these experiments, gel-phase metathesis was successfully demonstrated between a polymer-bound allyl ether and simple symmetrical disubstituted alkenes, monitoring the extent of reaction by 13C NMR. These reactions did not go to completion even with recycling and some evidence for competing interchain metathesis is presented, based on the increased broadening and reduced mobility of the ensuing polymer.Key words: alkene metathesis, ruthenium, gel-phase, 13C NMR.

The enzymic degradation of lignin by white-rot fungi

1983 ◽  
Vol 300 (1100) ◽  
pp. 293-303 ◽  
Keyword(s):  
Primary Alcohol ◽  
White Rot Fungi ◽  
Alcohol Oxidase ◽  
High Oxygen ◽  
White Rot ◽  
Side Chain ◽  
Ether Linkage ◽  
Ether Bond ◽  
Phenolic Group ◽  
Oxygen Concentrations

A possible pathway for the depolymerization of lignin is presented. The ether bond is the principal bond resulting in the polymerization of the phenylpropanoid precursors. The ether bond is very stable and unlikely to be degraded during the initial steps of depolymerization of lignin outside of the cell. Chemical analysis of the breakdown products suggests that the main reactions leading to the depolymerization are the cleavage of the aryl-α-carbon bond or the bond between the α- and β-carbons of the alkyl side chain. Physiological experiments show that high oxygen concentrations stimulate the rate of breakdown of lignin; this could be the result of the activation of an enzyme with low affinity for oxygen such as laccase or polyphenol oxidase. It is also possible that high oxygen concentrations result in the appearance of free radicals of oxygen in the assay system. It is proposed that laccase in the presence of hydroxyl radicals has the capacity to act as an exoligninase, removing aryl monomers that contain a free phenolic group. The mechanism of depolymerization of derivatives in which the phenolic group actually participates in an ether linkage is less clear. This may be achieved through the action of an extracellular alcohol oxidase that converts the primary alcohol to an aldehyde, resulting in the cleavage of the αC-βC bond. This enzyme may be considered an endoligninase.

Assemblies of D-peptides for Targeting Cell Nucleolus

2019 ◽  
Author(s):  
Huaimin Wang ◽  
Zhaoqianqi Feng ◽  
Weiyi Tan ◽  
Bing Xu
Keyword(s):  
Particle Morphology ◽  
Side Chain ◽  
Mechanism Study ◽  
Structural Analogue ◽  
Hydrophobic Residues ◽  
Subcellular Organelles ◽  
First Case ◽  
New Strategy ◽  
Peptide Derivative ◽  
Peptide Nanoparticles

<p>Selectively targeting cell nucleolus remains a challenge. Here we report the first case that D-peptides form membraneless molecular condensates with RNA for targeting cell nucleolus. A D-peptide derivative, enriched with lysine and hydrophobic residues, self-assembles to form nanoparticles, which enter cells through clathrin dependent endocytosis and mainly accumulate at cell nucleolus. Structural analogue of the D-peptide reveals that particle morphology of the assemblies, which depends on the side chain modification, favors the cellular uptake. Contrasting to those of the D-peptide, the assemblies of the corresponding L-enantiomer largely localize in cell lysosomes. Preliminary mechanism study suggests that the D-peptide nanoparticles interact with RNA to form membraneless condensates in the nucleolus, which further induces DNA damage and results in cell death. This work illustrates a new strategy for rationally designing supramolecular assemblies of D-peptides for targeting subcellular organelles.</p>

Formation of spiro adduct from N-methyl-N-(2,4,6-trinitrophenyl)glycine anion

1989 ◽  
Vol 54 (2) ◽  
pp. 440-445 ◽  
Author(s):  
Vladimír Macháček ◽  
Alexandr Čegan ◽  
Miloš Sedlák ◽  
Vojeslav Štěrba
Keyword(s):  
Nmr Spectroscopy ◽  
Dimethyl Sulfoxide ◽  
Equilibrium Constant ◽  
Mole Fraction ◽  
Nucleophilic Addition ◽  
Adduct Formation ◽  
First Case ◽  
C Nmr

The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in methanol-dimethyl sulfoxide mixtures produces spiro[(3-methyl-5-oxazolidinone)-2,1'-(2',4',6'-trinitrobenzenide)]. The spiro adduct has been identified by means of 1H and 13C NMR spectroscopy. This is the first case when the formation of a Meisenheimer adduct with carboxylate ion is observed. Logarithm of the equilibrium constant of adduct formation increases linearly with the mole fraction of dimethyl sulfoxide in its mixture with methanol.

E-Homolupane Derivatives Substituted in Position 17 and 22a. 1H NMR, 13C NMR and IR Spectra

1995 ◽  
Vol 60 (4) ◽  
pp. 619-635 ◽  
Author(s):  
Václav Křeček ◽  
Stanislav Hilgard ◽  
Miloš Buděšínský ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
2D Nmr ◽  
Coupling Constants ◽  
Side Chain ◽  
Oxidation Reactions ◽  
H Nmr ◽  
Complete Assignment ◽  
Nmr Techniques ◽  
Intramolecular Association ◽  
C Nmr

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1H NMR, 13C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1H and 13C NMR spectra are discussed.

A route to 24-epibrassinolide from ergosterol avoiding the use of osmium tetroxide

1990 ◽  
Vol 55 (11) ◽  
pp. 2738-2755 ◽  
Author(s):  
Václav Černý ◽  
Miloš Buděšínský
Keyword(s):  
Nmr Spectra ◽  
Osmium Tetroxide ◽  
Model Compound ◽  
Side Chain ◽  
C Nmr

A synthesis of (22R,23R)-2α,3α,22,23-tetrahydroxy-5α-ergostan-6-one (V) from the dienone IV via the diepoxide XXII is described. The tetrol V is a key intermediate in the synthesis of 24-epibrassinolide. The reactivity of the side chain was studied on 5α-ergost-22-en-6-one (XIV) as a model compound. 1H and 13C NMR spectra of 24-epibrassinolide derivatives are discussed.

scholarly journals Dynamic aspect of bacteriorhodopsin as viewed from13C NMR: Conformational elucidation, surface dynamics and information transfer from the surface to inner residues

2002 ◽  
Vol 16 (3-4) ◽  
pp. 107-120 ◽  
Author(s):  
H. Saitô ◽  
R. Kawaminami ◽  
M. Tanio ◽  
T. Arakawa ◽  
S. Yamaguchi ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Information Transfer ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Surface Dynamics ◽  
Transmembrane Helices ◽  
Nmr Studies ◽  
Specific Manner ◽  
Local Conformations ◽  
C Nmr

We demonstrate here how dynamic as well as conformational features of bacteriorhodopsin (bR) in purple membrane (PM) as a typical membrane protein are revealed by extensive13C NMR studies on [3-13C]-, [2-13C]-, [1-13C]Ala or [1-13C]Val-labeled bR and a variety of site-directed mutants. A number of13C NMR peaks were well-resolved for [3‒13C]Ala‒ and [1-13C]Val-bR under the condition of fully hydrated PM at ambient temperature and assigned to individual amino-acid residues, initially by regio-specific manner with reference to the data of the conformation-dependent displacements of peaks from model polypeptides and subsequently by site-specific manner with reference to the specifically reduced peak-intensities of site-directed mutant as compared with those of wild type. It is noticeable that the revealed bR structure at ambient temperature by13C NMR is not static as anticipated from the data of diffraction studies at cryo-temperature but is dynamically heterogeneous undergoing motional fluctuations with various frequencies (102–108Hz) depending upon the domains of interest. We further applied this approach to reveal how charged state of surface residues, especially at the side-chain of exracellular Glu residues (Glu 194 and 204), could be transmitted to the inner part of the helices such as Ala 53, 84, and 215 to alter their local conformations of transmembrane helices near at the Schiff base through side-chain interactions. We also analyzed how information of the protonation at Asp 85 from helix C is initially transmitted to helices B (Val 49) and G (Val 213) though modified helix‒helix interactions through the side-chains of Arg 82.

Thyroid Hormone Stereochemistry. II. Molecular Structure of Thyronine HCl Ethyl Ester Monohydrate

1974 ◽  
Vol 52 (17) ◽  
pp. 3042-3047 ◽  
Author(s):  
Arthur Camerman ◽  
Norman Camerman
Keyword(s):  
Ethyl Ester ◽  
Three Dimensional ◽  
Chloride Ion ◽  
Dimensional Structure ◽  
Side Chain ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Ether Linkage ◽  
Cell Dimensions ◽  
Phenyl Rings

The three-dimensional structure of L-thyronine, the non-iodinated physiologically inactive analog of thyroxine, has been determined by single crystal X-ray diffraction and compared to the active thyroid hormones. The compound crystallized as the monohydrate of thyronine hydrochloride ethyl ester in the monoclinic space group P21 with cell dimensions a = 10.502, b = 5.165, c = 17.940 Å, β = 109.74°. The structure was solved by Patterson methods to find the chloride ion and iterative Fourier maps to locate the rest of the atoms. Refinement was by anisotropic full-matrix least squares to convergence at R = 0.048.The two phenyl rings adopt a twisted orientation with respect to each other with angles of −37° and −67° between the plane of the inter-ring ether linkage and the planes of the α- and β-rings, respectively. This orientation differs considerably from that found in the iodinated thyronines. The conformation of the alanine side chain is remarkably similar to that of the alanine in the iodinated thyronines.

scholarly journals Control of Rotary Cranes Using Fuzzy Logic

2003 ◽  
Vol 10 (2) ◽  
pp. 81-95 ◽  
Author(s):  
Amjed A. Al-mousa ◽  
Ali H. Nayfeh ◽  
Pushkin Kachroo
Keyword(s):  
Fuzzy Logic ◽  
Fuzzy Logic Controller ◽  
Fuzzy Inference ◽  
Fuzzy Controller ◽  
Operating Conditions ◽  
Building Construction ◽  
Loop Control ◽  
Industrial Structures ◽  
Inference Engines ◽  
First Case

Rotary cranes (tower cranes) are common industrial structures that are used in building construction, factories, and harbors. These cranes are usually operated manually. With the size of these cranes becoming larger and the motion expected to be faster, the process of controlling them has become difficult without using automatic control methods. In general, the movement of cranes has no prescribed path. Cranes have to be run under different operating conditions, which makes closed-loop control attractive.In this work a fuzzy logic controller is introduced with the idea of “split-horizon”; that is, fuzzy inference engines (FIE) are used for tracking the position and others are used for damping the load oscillations. The controller consists of two independent sub-controllers: radial and rotational. Each of these controllers has two fuzzy inference engines (FIE). Computer simulations are used to verify the performance of the controller. Three simulation cases are presented. In the first case, the crane is operated in the gantry (radial) mode in which the trolley moves along the jib while the jib is fixed. In the second case (rotary mode), the trolley moves along the jib and the jib rotates. In the third case, the trolley and jib are fixed while the load is given an initial disturbance. The results from the simulations show that the fuzzy controller is capable of keeping the load-oscillation angles small throughout the maneuvers while completing the maneuvers in relatively reasonable times.

scholarly journals INVESTIGATION OF MULTI-ZONE MODELS FOR SPARK IGNITION ENGINE FUELED WITH ETHANOL

2021 ◽  
Vol 22 (2) ◽  
pp. 339-351
Author(s):  
A. A. Dare ◽  
Olanrewaju Olatunde ◽  
O. S. Ismail ◽  
A. S. Shote ◽  
O. J. Alamu ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Ignition Time ◽  
High Volume ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Zone Model ◽  
Fuel Blends ◽  
Indicated Mean Effective Pressure ◽  
First Case

This research is aimed at investigating the effect of using ethanol (E100) in multi-zone model analysis consisting of multi-combustion chamber zoning cases. The first case considered is a three-zone model that has an unburned zone, burned zone, and transitory zone. The second case model is also three-zone, consisting of an unburned zone and two partitioned burned zones. The burned zone was imagined partitioned into burned zone-1 and burned zone-2 under uneven fuel distribution having different equivalent ratios. The third case is a four-zone model including two regions of burned zone, an unburned zone and a transitory zone, which is unburned burned zone containing a mixture of unburned and burned gases. Arbitrary constants for each of the unburned (CC1) and burned (CC2) Zone leakages in the unburned burned Zone are 0.00025, 0.0005, 0.001, 0.002, 0.005, 0.1 and 0.5. The Mass Fraction Burned (MFB) for zone-1, x1 and burned zone-2, x2 are computed using Partitioned Burnt Zones Ratios (PBZR) of 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 and 8:2. Two equivalent ratios, one for each fuel MFB (?1, ?2), (0.8, 0.6) and (0.6, 0.8) are analyzed using fuel blends of varying percentage. A comparison of values of the three zoning cases is done using peak values from the three-zone models to evaluate the four-zone model. The model was compared with a spark ignition engine (SIE) operating with a premium motor spirit (PMS) serving as baseline. The engine operating conditions were set at an engine speed of 2000 rpm, -35bTDC ignition time, and burn duration at 60 oC. The indicated mean effective pressure (IMEP), thermal efficiency (?), cylinder pressure and emission fraction from the developed models and those of two-zone analysis obtained agreed with literature values. The result showed it is undesirable to have a high volume of burned charge as infiltrate. The three-zone segmented model predicted the highest engine thermal efficiency and peak pressure at mass burn ratio of 7:3. A general reduction in N2 emission was observed for the three-zone transitional and four-zone models. ABSTRAK: Kajian ini menilai kesan etanol (E100) dalam analisis model zon-berbilang yang terdapat pada masalah pengezonan kebuk pembakaran-berbilang. Kes pertama yang diambil kira adalah model tiga-zon yang mempunyai zon tidak terbakar, zon terbakar dan zon peralihan. Model kedua merupakan juga tiga-zon yang terdiri daripada zon tidak-terbakar dan dua zon bahagian yang terbakar. Zon yang terbakar dibahagikan kepada zon-1 terbakar dan zon-2 terbakar di bawah kebakaran tidak sekata yang mempunyai nisbah berlainan. Kes ketiga adalah model zon-keempat termasuk dua kawasan zon terbakar, zon tidak-terbakar dan zon peralihan iaitu zon terbakar tidak-terbakar di mana ia adalah campuran gas terbakar dan tidak-terbakar. Tetapan sebarangan bagi setiap zon kebocoran tidak-terbakar (CC1) dan terbakar (CC2) dalam zon terbakar tidak-terbakar adalah 0.00025, 0.0005, 0.001, 0.002, 0.005, 0.1 dan 0.5. Pecahan Jisim Terbakar (MFB) bagi zon-1, x1 dan zon-2 terbakar, x2 dikira menggunakan Nisbah Zon Bahagian Terbakar (PBZR) sebanyak 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 dan 8:2. Nisbah dua persamaan, setiap satu bahan api MFB adalah (?1, ?2), (0.8, 0.6) dan (0.6, 0.8) dan diuji menggunakan pelbagai peratus bahan api campuran. Nilai perbandingan bagi tiga kes zon dibuat menggunakan nilai puncak dari model tiga-zon bagi menilai model empat-zon. Model ini dibandingkan dengan enjin cucuhan bunga api (SIE) beroperasi dengan motor alkohol premium (PMS) sebagai garis asas. Keadaan operasi enjin adalah dihadkan pada 2000 rpm kelajuan enjin, masa pencucuhan -35bTDC dan tempoh pembakaran pada 60 oC. Tekanan berkesan min tertunjuk (IMEP), kecekapan haba tertunjuk (?), tekanan silinder dan pecahan pengeluaran dari model yang dibangunkan dan analisis dua-zon yang terhasil adalah sama dengan nilai literatur. Dapatan kajian menunjukkan cas terbakar pada isipadu yang banyak adalah tidak diingini sebagai penyerap. Model tiga bahagian zon menunjukkan kecekapan haba enjin tertinggi dan tekanan puncak pada jisim bakar dengan nisbah 7:3. Manakala, pengurangan umum telah diperhatikan pada pengeluaran N2 di peralihan tiga-zon dan model empat zon.

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