scholarly journals Deep Eutectic Solvents as New Reaction Media to Produce Alkyl-Glycosides Using Alpha-Amylase from Thermotoga maritima

2019 ◽  
Vol 20 (21) ◽  
pp. 5439 ◽  
Author(s):  
Alfonso Miranda-Molina ◽  
Wendy Xolalpa ◽  
Simon Strompen ◽  
Rodrigo Arreola-Barroso ◽  
Leticia Olvera ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Thermotoga Maritima ◽  
Variable Temperature ◽  
Deep Eutectic Solvents ◽  
Temperature Limit ◽  
Thermostable Enzyme ◽  
Alkyl Glycosides ◽  
Alcoholysis Reaction ◽  
Reaction Media

Deep Eutectic Solvents (DES) were investigated as new reaction media for the synthesis of alkyl glycosides catalyzed by the thermostable α-amylase from Thermotoga maritima Amy A. The enzyme was almost completely deactivated when assayed in a series of pure DES, but as cosolvents, DES containing alcohols, sugars, and amides as hydrogen-bond donors (HBD) performed best. A choline chloride:urea based DES was further characterized for the alcoholysis reaction using methanol as a nucleophile. As a cosolvent, this DES increased the hydrolytic and alcoholytic activity of the enzyme at low methanol concentrations, even when both activities drastically dropped when methanol concentration was increased. To explain this phenomenon, variable-temperature, circular dichroism characterization of the protein was conducted, finding that above 60 °C, Amy A underwent large conformational changes not observed in aqueous medium. Thus, 60 °C was set as the temperature limit to carry out alcoholysis reactions. Higher DES contents at this temperature had a detrimental but differential effect on hydrolysis and alcoholysis reactions, thus increasing the alcoholyisis/hydrolysis ratio. To the best of our knowledge, this is the first report on the effect of DES and temperature on an enzyme in which structural studies made it possible to establish the temperature limit for a thermostable enzyme in DES.

scholarly journals Variable Temperature Synthesis of Tunable Flame-Generated Carbon Nanoparticles

2021 ◽  
Vol 7 (2) ◽  
pp. 44
Author(s):  
Francesca Picca ◽  
Angela Di Pietro ◽  
Mario Commodo ◽  
Patrizia Minutolo ◽  
Andrea D’Anna
Keyword(s):  
Carbon Nanoparticles ◽  
Variable Temperature ◽  
Flame Temperature ◽  
Cost Effective ◽  
Synthesis Process ◽  
Electrical Mobility ◽  
Material Synthesis ◽  
Online Measurements ◽  
Degree Of Graphitization

In this study, flame-formed carbon nanoparticles of different nanostructures have been produced by changing the flame temperature. Raman spectroscopy has been used for the characterization of the carbon nanoparticles, while the particle size has been obtained by online measurements made by electrical mobility analysis. The results show that, in agreement with recent literature data, a large variety of carbon nanoparticles, with a different degree of graphitization, can be produced by changing the flame temperature. This methodology allows for the synthesis of very small carbon nanoparticles with a size of about 3-4 nm and with different graphitic orders. Under the perspective of the material synthesis process, the variable-temperature flame-synthesis of carbon nanoparticles appears as an attractive procedure for a cost-effective and easily scalable production of highly tunable carbon nanoparticles.

Estimating the shape and size of supramolecular assemblies by variable temperature diffusion ordered spectroscopy

2014 ◽  
Vol 12 (40) ◽  
pp. 7932-7936 ◽  
Author(s):  
Benjamin M. Schulze ◽  
Davita L. Watkins ◽  
Jing Zhang ◽  
Ion Ghiviriga ◽  
Ronald K. Castellano
Keyword(s):  
Self Assembly ◽  
Variable Temperature ◽  
Supramolecular Assemblies ◽  
The Self ◽  
Conjugated Oligomers ◽  
Photovoltaic Devices ◽  
Temperature Diffusion ◽  
Shape And Size

Reported is characterization of the self-assembly of π-conjugated oligomers, molecules studied recently in photovoltaic devices, using variable temperature diffusion ordered spectroscopy; the approach has allowed estimation of assembly size, shape, and molecularity.

scholarly journals Characterization of Functional Hepatitis C Virus Envelope Glycoproteins

2004 ◽  
Vol 78 (6) ◽  
pp. 2994-3002 ◽  
Author(s):  
Anne Op De Beeck ◽  
Cécile Voisset ◽  
Birke Bartosch ◽  
Yann Ciczora ◽  
Laurence Cocquerel ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Conformational Changes ◽  
Structural Changes ◽  
Envelope Proteins ◽  
Viral Envelope ◽  
Envelope Glycoproteins ◽  
Functional Envelope

ABSTRACT Hepatitis C virus (HCV) encodes two envelope glycoproteins, E1 and E2, that assemble as a noncovalent heterodimer which is mainly retained in the endoplasmic reticulum. Because assembly into particles and secretion from the cell lead to structural changes in viral envelope proteins, characterization of the proteins associated with the virion is necessary in order to better understand how they mature to be functional in virus entry. There is currently no efficient and reliable cell culture system to amplify HCV, and the envelope glycoproteins associated with the virion have therefore not been characterized yet. Recently, infectious pseudotype particles that are assembled by displaying unmodified HCV envelope glycoproteins on retroviral core particles have been successfully generated. Because HCV pseudotype particles contain fully functional envelope glycoproteins, these envelope proteins, or at least a fraction of them, should be in a mature conformation similar to that on the native HCV particles. In this study, we used conformation-dependent monoclonal antibodies to characterize the envelope glycoproteins associated with HCV pseudotype particles. We showed that the functional unit is a noncovalent E1E2 heterodimer containing complex or hybrid type glycans. We did not observe any evidence of maturation by a cellular endoprotease during the transport of these envelope glycoproteins through the secretory pathway. These envelope glycoproteins were recognized by a panel of conformation-dependent monoclonal antibodies as well as by CD81, a molecule involved in HCV entry. The functional envelope glycoproteins associated with HCV pseudotype particles were also shown to be sensitive to low-pH treatment. Such conformational changes are likely necessary to initiate fusion.

scholarly journals Discovery and Characterization of a Novel CD4-Binding Adnectin with Potent Anti-HIV Activity

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
David Wensel ◽  
Yongnian Sun ◽  
Zhufang Li ◽  
Sharon Zhang ◽  
Caryn Picarillo ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Viral Entry ◽  
High Affinity ◽  
Glycosylation Sites ◽  
Spectrum Activity ◽  
Anti Hiv ◽  
Hiv 1 ◽  
Broad Spectrum Activity

ABSTRACT A novel fibronectin-based protein (Adnectin) HIV-1 inhibitor was generated using in vitro selection. This inhibitor binds to human CD4 with a high affinity (3.9 nM) and inhibits viral entry at a step after CD4 engagement and preceding membrane fusion. The progenitor sequence of this novel inhibitor was selected from a library of trillions of Adnectin variants using mRNA display and then further optimized for improved antiviral and physical properties. The final optimized inhibitor exhibited full potency against a panel of 124 envelope (gp160) proteins spanning 11 subtypes, indicating broad-spectrum activity. Resistance profiling studies showed that this inhibitor required 30 passages (151 days) in culture to acquire sufficient resistance to result in viral titer breakthrough. Resistance mapped to the loss of multiple potential N-linked glycosylation sites in gp120, suggesting that inhibition is due to steric hindrance of CD4-binding-induced conformational changes.

Synthesis and characterization of novel ternary deep eutectic solvents

2014 ◽  
Vol 25 (1) ◽  
pp. 104-106 ◽  
Author(s):  
Yu-Ting Liu ◽  
Yan-An Chen ◽  
Yan-Jun Xing
Keyword(s):  
Deep Eutectic Solvents ◽  
Synthesis And Characterization
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