scholarly journals An eight-state molecular sequential switch featuring a dual single-bond rotation photoreaction

2021 ◽  
Author(s):  
Aaron Gerwien ◽  
Benjamin Jehle ◽  
Marvin Irmler ◽  
Peter Mayer ◽  
Henry Dube
Keyword(s):  
Molecular Weight ◽  
Strong Increase ◽  
Switching Function ◽  
Single Bond ◽  
Step Cycle ◽  
Covalent Bonds ◽  
Bond Rotation ◽  
Switch Architecture ◽  
Fundamental Limit ◽  
Essential Problem

Typical photowitches interconvert between two different states by simple isomerization reactions, which represents a fundamental limit for applications. To expand the switching capacity usually different photoswitches have to be linked together leading to strong increase in molecular weight, diminished switching function, and less precision and selectivity of switching events. Herein we present an approach for solving this essential problem with a different photoswitching concept. A basic molecular switch architecture provides precision photoswitching between eight different states via controlled rotations around three adjacent covalent bonds. All eight states can be populated one after another in an eight-step cycle by alternating between photochemical Hula-Twist isomerizations and thermal single bond rotations. By simply changing solvent and temperature the same switch can also undergo a different cycle instead interconverting just five isomers in a selective sequence. This behavior is enabled through the discovery of an unprecedented photoreaction, a one photon dual single bond rotation.

scholarly journals Active and Unidirectional Acceleration of Biaryl Rotation by a Molecular Motor

2019 ◽  
Author(s):  
Edgar Uhl ◽  
Peter Mayer ◽  
Henry Dube
Keyword(s):  
Potential Energy ◽  
Motor Unit ◽  
Rate Constants ◽  
Molecular Motors ◽  
Molecular Motor ◽  
Molecular Machine ◽  
Single Bond ◽  
Bond Rotation ◽  
Immense Potential

Light driven molecular motors possess immense potential as central driving units for future nanotechnology. Integration into larger molecular setups and transduction of their mechanical motions represents the current frontier of research. Here we report on an integrated molecular machine setup allowing to transmit potential energy from a motor unit unto a remote receiving entity. The setup consists of a motor unit connected covalently to a distant and sterically strongly encumbered biaryl receiver. By action of the motor unit single bond rotation of the receiver is strongly accelerated and forced to proceed unidirectionally. The transmitted potential energy is directly measured as the extent to which energy degeneration is lifted in the thermal atropisomerization of this biaryl. Energy degeneracy is reduced by as much as 2.3 kcal/mol and rate accelerations up to 2x10<sup>5</sup> fold in terms of rate constants are achieved.<br><b></b>

scholarly journals The composition of peptidochitodextrins from sarcophagid puparial cases

1971 ◽  
Vol 125 (3) ◽  
pp. 703-716 ◽  
Author(s):  
H. Lipke ◽  
T. Geoghegan
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Protein Complex ◽  
Covalent Bonds ◽  
Aromatic Residues ◽  
Similar Molecular Weight ◽  
X Ray ◽  
Molecular Weights ◽  
Physical Interactions ◽  
The Stability

1. N-Bromosuccinimide cleaved proteins and pigments from fly puparia, increasing the chitin:protein ratio from 0.5 to 1.5. The product afforded subfractions (ratio 5:1) of molecular weights of 1200 and 1600 devoid of aromatic residues and N-terminal β-alanine, direct aryl links between polysaccharide chains being discounted. 2. The chitin–protein complex decreased in molecular weight when treated with Pronase, which suggested polypeptide bridges within the native chitin micelle. The limit dextrins generated by chitinase were mixtures of unsubstituted dextrins and peptidylated oligosaccharides, with the former predominating. 3. Peptidochitodextrins of similar molecular weight but markedly different solubility were prepared, which were indistinguishable with respect to amino acid, glucosamine, acetyl, X-ray or infrared characteristics. It is suggested that physical interactions contribute to the stability of the integument in addition to the covalent bonds that form during sclerotization.

The dynamics of carbon-carbon single bond rotation in acyclic alcohols

1974 ◽  
Vol 15 (6) ◽  
pp. 547-550 ◽  
Author(s):  
C.Hackett Bushweller ◽  
Steven Hoogasian ◽  
Warren G. Anderson
Keyword(s):  
Single Bond ◽  
Bond Rotation

A fluorescent probe for hypochlorite based on the modulation of the unique rotation of the N–N single bond in acetohydrazide

2015 ◽  
Vol 51 (52) ◽  
pp. 10435-10438 ◽  
Author(s):  
Lingliang Long ◽  
Yanjun Wu ◽  
Lin Wang ◽  
Aihua Gong ◽  
Feilong Hu ◽  
...  
Keyword(s):  
Fluorescent Probe ◽  
Single Bond ◽  
Signaling Mechanism ◽  
Bond Rotation

A fluorescent probe for hypochlorite was developed based on a novel signaling mechanism of modulating the N–N bond rotation in acetohydrazide.

Molecular Beam and ab Initio Studies of Photoactive Yellow Protein Chromophores: Influence of the Thioester Functionality and Single Bond Rotation

2014 ◽  
Vol 118 (43) ◽  
pp. 12395-12403 ◽  
Author(s):  
Eric M. M. Tan ◽  
Saeed Amirjalayer ◽  
Paul Mazzella ◽  
Bert H. Bakker ◽  
Jan H. van Maarseveen ◽  
...  
Keyword(s):  
Ab Initio ◽  
Molecular Beam ◽  
Photoactive Yellow Protein ◽  
Single Bond ◽  
Bond Rotation

Glycosylation of plasma proteins with [U-14C]gIucose in vivo

1982 ◽  
Vol 60 (10) ◽  
pp. 942-951
Author(s):  
Rudolf Vrba ◽  
Stephen P. Adams
Keyword(s):  
Molecular Weight ◽  
Body Weight ◽  
Sialic Acid ◽  
Plasma Proteins ◽  
Gel Filtration ◽  
Specific Radioactivity ◽  
Apparent Molecular Weight ◽  
Covalent Bonds ◽  
High Specific Radioactivity

Within 1–12 h after subcutaneous injection of [U-14C]glucose, significant amounts of 14C attached by stable (probably covalent) bonds were found in plasma proteins of rats. More than 30% of 14C of [U-14C]glucose injected per 1 g body weight was incorporated into proteins contained in 1 mL of plasma. Less than 5% of 14C of the [14C]glucose-labelled plasma proteins was soluble in cold dilute perchloric acid, whereas more than 80% of 14C in the [14C]glucose-labelled plasma proteins was soluble in 50% saturated solutions of ammonium sulfate. From [U-14C]glucose-labelled plasma proteins, approximately 50% of the incorporated 14C was recovered in carbohydrate moieties (sialic acid, 8–12%; mannose and galactose, 15–31%; hexosamines, 8–14%) and the rest of the 14C (42–64%) was recovered from protein residue. Gel-filtration and electrophoresis profiles of distribution of 14C in [U-14C]leucine-labelled plasma proteins were very similar to those of [U-14C]glucose-labelled plasma proteins; a relatively high specific radioactivity was observed in fractions having an apparent molecular weight of 105 × 103 or its multiples (220 × 103 and 520 × 103). However, about 99% of the incorporated 14C was recovered from the protein residue of [14C]leucine-labelled plasma proteins, whereas only traces of 14C were found in the carbohydrate moieties. [U-14C]Alanine is also a relatively poor precursor of 14C for incorporation into carbohydrate moieties of plasma proteins as compared with [U-14C]glucose.

scholarly journals Kinetics and Thermodynamics of Ultrasound-Assisted Depolymerization of κ-Carrageenan

2016 ◽  
Vol 11 (1) ◽  
pp. 48 ◽  
Author(s):  
Ratnawati Ratnawati ◽  
Aji Prasetyaningrum ◽  
Dyah Hesti Wardhani
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Chain Scission ◽  
Number Average Molecular Weight ◽  
Covalent Bonds ◽  
Exponential Factor ◽  
Kinetics And Thermodynamics ◽  
Thermal Depolymerization ◽  
Ultrasound Assisted ◽  
Kinetics Of

<p>The ultrasound-assisted depolymerization of κ-carrageenan has been studied at various temperatures and times. The κ-carrageenan with initial molecular weight of 545 kDa was dispersed in water to form a 5 g/L solution, which was then depolymerized in an ultrasound device at various temperatures and times. The viscosity of the solution was measured using Brookfield viscometer, which was then used to find the number-average molecular weight by Mark-Houwink equation. To obtain the kinetics of κ-carrageenan depolymerization, the number-average molecular weight data was treated using midpoint-chain scission kinetics model. The pre-exponential factor and activation energies for the reaction are 2.683×10<sup>-7</sup> mol g<sup>-1</sup> min<sup>-1</sup> and 6.43 kJ mol<sup>-1</sup>, respectively. The limiting molecular weight varies from 160 kDa to 240 kDa, and it is linearly correlated to temperature. The results are compared to the result of thermal depolymerization by calculating the half life. It is revealed that ultrasound assisted depolymerization of κ-carrageenan is faster than thermal depolymerization at temperatures below 72.2°C. Compared to thermal depolymerization, the ultrasound-assisted process has lower values of E<sub>a</sub>, ΔG<sup>‡</sup>, ΔH<sup>‡</sup>, and ΔS<sup>‡</sup>, which can be attributed to the ultrasonically induced breakage of non-covalent bonds in κ-carrageenan molecules. Copyright © 2016 BCREC GROUP. All rights reserved</p><p><em>Received: 10<sup>th</sup> November 2015; Revised: 18<sup>th</sup> January 2016; Accepted: 19<sup>th</sup> January 2016</em></p><p><strong>How to Cite</strong>: Ratnawati, R., Prasetyaningrum, A., Wardhani, D.H. (2016). Kinetics and Thermodynamics of Ultrasound-Assisted Depolymerization of κ-Carrageenan. <em>Bulletin of Chemical Reaction Engineering &amp; Catalysis</em>, 11(1): 48-58. (doi:10.9767/bcrec.11.1.415.48-58)</p><p><strong>Permalink/DOI</strong>:<a href="/index.php/bcrec/editor/viewMetadata/%20http:/dx.doi.org/10.9767/bcrec.11.1.415.48-58"> http://dx.doi.org/10.9767/bcrec.11.1.415.48-58</a></p><p> </p>

Subunit Structure of Human Factor VIII

1975 ◽  
Author(s):  
J. A. van Mourik ◽  
W. T. LaBruyère ◽  
I. A. Mochtar
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Factor Viii ◽  
Apparent Molecular Weight ◽  
Subunit Structure ◽  
Single Chain ◽  
Covalent Bonds ◽  
Single Polypeptide Chain ◽  
Human Factor Viii ◽  
Low Ionic Strength

Several investigations have shown that factor VIII is a high molecular weight aggregate and that both non-covalent and disulphide bonds contribute to the stabilization of the macromolecular factor VIII aggregate. As shown previously (1) disruption of non-covalent bonds can be accomplished at relatively low ionic strength and neutral pH and results via a series of homologous oligomers (having constant charge/mass ratios) in 2 immunologically non-related subunits. Thus, the generally accepted concept that factor VIII is constructed of identical subunits seems incorrect. For several reasons we assume that the observed fragmentation at low ionic strength is not due to proteolytic breakdown. However, this view is not favoured by the observation that tryptic and plasmic digestion of factor VIII (in aggregated form) results in gel electrophoresis patterns comparable with those obtained of factor VIII after low ionic strength dissociation. Further, evidence will be presented that the assumption that reduction of factor VIII under denaturating conditions results in a single polypeptide chain is also no longer tenable. As far as the reduction of aggregated factor VIII is concerned our observations agree with data from the literature, that is, reduction of factor VIII results in 1 major subunit with an apparent molecular weight of approximately 270.000. However, when factor VIII is first dissociated at low ionic strength followed by reduction, smaller fragments appear in the electrophoresis pattern. Thus, it seems most likely that the apparent single chain subunit is in fact, constructed of smaller non-covalently linked fragments.(1) J. A. van Mourik et al. Thrombosis Research, 4, 155, 1974.

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