Photo-thermally Switchable Peptide Nanostructures towards Modulating Catalytic Hydrolase Activity

Nanoscale ◽  
2021 ◽  
Author(s):  
Ashmeet Singh ◽  
Jojo P Joseph ◽  
Deepika Gupta ◽  
Chirag Miglani ◽  
Nimisha A Mavlankar ◽  
...  
Keyword(s):  
Hydrolase Activity ◽  
Catalytic Activities ◽  
Adverse Condition ◽  
Functional Peptides ◽  
The Stability

Enzymes are the most efficient catalysts in nature that possess an impressive range of catalytic activities albeit limited by the stability in adverse condition. Functional peptides have emerged as alternative...

Study on Alkylation of Catechol with Ethanol by Al-P-Ti-O Oxides

2012 ◽  
Vol 599 ◽  
pp. 114-117 ◽  
Author(s):  
Xiao Mei Zhu ◽  
Bing Sun ◽  
Cheng Huo
Keyword(s):  
Citric Acid ◽  
Surface Area ◽  
Vapour Phase ◽  
Cane Sugar ◽  
Precipitation Method ◽  
Title Reaction ◽  
Catalytic Activities ◽  
P Content ◽  
The Stability ◽  
Ti Content

Vapour-phase alkylation of catechol with ethanol has been investigated over Al-P-Ti-O oxides prepared by non-uniform precipitation method. The catalytic activities decrease with the increase of P content. The catalytic activities increase with increasing Ti content, while the selectivity to guathol decreases. The results of XRD characterization demonstrate that the increase of titanium and the addition of additive affects the structure of the catalysts. The addition of additive (cane sugar or citric acid) decrease the catalytic activities of the catalysts, while increase the stability of the catalyst. Both the conversion of catechol and the selectivity to guathol decrease by the addition of additive, and the C-alkylation products increase obviously. The results indicate that the appropriate pores and surface area are enough for the title reaction, lager pore and higher surface area are favorable to C-alkylation products and stability of catalyst.

scholarly journals On the Stability of Water Oxidation Catalysts: Challenges and Prospects

2012 ◽  
Vol 65 (6) ◽  
pp. 638 ◽  
Author(s):  
Alex Izgorodin ◽  
Orawan Winther-Jensen ◽  
Douglas R. MacFarlane
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Commercial Application ◽  
Significant Progress ◽  
Oxidation Catalysts ◽  
Research Focus ◽  
Catalytic Activities ◽  
The Stability ◽  
Stability Of Water

Future requirements for water splitting technologies need highly efficient water oxidation catalysts that are sufficiently stable for operation over many years. Recent research has achieved significant progress in improving the electro-catalytic activities of these catalysts. However, there has not been a strong research focus on their long-term mechanical and chemical stability, yet this is critical for commercial application. In this paper we discuss some of the chemical and thermodynamic challenges confronting this goal, as well as some of the strategies that are available to overcome them. The challenge becomes even greater in the area of photo-active electromaterials; fortunately some of the same strategies may allow progress in this area also.

scholarly journals Peptidoglycan Cross-Linking Activity of L,D-Transpeptidases from Clostridium difficile and Inactivation of These Enzymes by β-Lactams

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Laetitia Sütterlin ◽  
Zainab Edoo ◽  
Jean-Emmanuel Hugonnet ◽  
Jean-Luc Mainardi ◽  
Michel Arthur
Keyword(s):  
Mass Spectrometry ◽  
Clostridium Difficile ◽  
Cross Linking ◽  
Content Type ◽  
Catalytic Activities ◽  
Cross Links ◽  
Covalent Adducts ◽  
The Stability ◽  
Hydrolysis Of ◽  
Insight Into

ABSTRACT In most bacteria, the essential targets of β-lactam antibiotics are the d , d -transpeptidases that catalyze the last step of peptidoglycan polymerization by forming 4→3 cross-links. The peptidoglycan of Clostridium difficile is unusual since it mainly contains 3→3 cross-links generated by l , d -transpeptidases. To gain insight into the characteristics of C. difficile peptidoglycan cross-linking enzymes, we purified the three putative C. difficile l , d -transpeptidase paralogues Ldt Cd1 , Ldt Cd2 , and Ldt Cd3 , which were previously identified by sequence analysis. The catalytic activities of the three proteins were assayed with a disaccharide-tetrapeptide purified from the C. difficile cell wall. Ldt Cd2 and Ldt Cd3 catalyzed the formation of 3→3 cross-links ( l , d -transpeptidase activity), the hydrolysis of the C-terminal d -Ala residue of the disaccharide-tetrapeptide substrate ( l , d -carboxypeptidase activity), and the exchange of the C-terminal d -Ala for d -Met. Ldt Cd1 displayed only l , d -carboxypeptidase activity. Mass spectrometry analyses indicated that Ldt Cd1 and Ldt Cd2 were acylated by β-lactams belonging to the carbapenem (imipenem, meropenem, and ertapenem), cephalosporin (ceftriaxone), and penicillin (ampicillin) classes. Acylation of Ldt Cd3 by these β-lactams was not detected. The acylation efficacy of Ldt Cd1 and Ldt Cd2 was higher for the carbapenems (480 to 6,600 M −1 s −1 ) than for ampicillin and ceftriaxone (3.9 to 82 M −1 s −1 ). In contrast, the efficacy of the hydrolysis of β-lactams by Ldt Cd1 and Ldt Cd2 was higher for ampicillin and ceftriaxone than for imipenem. These observations indicate that Ldt Cd1 and Ldt Cd2 are inactivated only by β-lactams of the carbapenem class due to a combination of rapid acylation and the stability of the resulting covalent adducts.

scholarly journals Variable effects of maturity-onset-diabetes-of-youth (MODY)-associated glucokinase mutations on substrate interactions and stability of the enzyme

1995 ◽  
Vol 309 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Y Liang ◽  
P Kesavan ◽  
L Q Wang ◽  
K Niswender ◽  
Y Tanizawa ◽  
...  
Keyword(s):  
Atp Binding ◽  
Maturity Onset Diabetes ◽  
Wild Type ◽  
Glutathione S Transferase ◽  
Induced Fit ◽  
Catalytic Activities ◽  
Onset Diabetes ◽  
Kinetic Effects ◽  
The Stability ◽  
Substrate Affinities

Mutations in the human glucokinase (GK) gene are thought to cause maturity-onset diabetes of youth (MODY) by leading to the production of enzymes with reduced catalytic activities and increased glucose Km values. However, in some cases the diabetic phenotype is more severe than might be predicted from these apparent kinetic effects alone. To determine whether these mutations might also effect other characteristics of the enzyme, nine MODY-associated mutants were expressed as fusion proteins with Schistosoma japonicum glutathione S-transferase (GST) and compared with three wild-type human GK isoforms that were also expressed in the same manner. Three GST-GK isoforms (liver 1, liver 2 and islet) were kinetically indistinguishable from each other and from purified rat liver GK. Noteworthy is a glucose-induced fit effect for the interaction of trinitrophenyl (TNP)-ATP with GST-GK, whereby glucose significantly increased the affinity of TNP-ATP binding to GST-GK without changing the stoichiometry of binding. The nine MODY-associated mutations studied either showed diminished catalytic activity, substrate affinities, allosteric regulation, or stability of the fusion enzyme. We conclude that: (1) Gly261 and Lys414 are important for ATP binding; (2) Val203 may be essential for a glucose-induced fit effect; and (3) the stability of fusion protein may be significantly reduced when Glu300 is replaced by Lys. These results suggest that, in addition to effects on the Km and Vmax. of GK, a decrease in the ATP-binding affinity or stability of the mutated enzyme may also contribute to a reduction of GK activity in individuals with GK-MODY. In the B-cell this would have the effect of blunting glucose-stimulated insulin release, thereby contributing to the diabetic phenotype.

scholarly journals New Potential Nonsteroidal Anti-Inflammatory Drugs with Antileukotrienic Effects: Influence on Model Proteins with Catalytic Activity

2002 ◽  
Vol 45 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Miloslava Netopilová ◽  
Jaroslav Dršata ◽  
Martin Beránek ◽  
Vladimír Palička
Keyword(s):  
E Coli ◽  
Catalytic Activities ◽  
Benzoic Acid Derivatives ◽  
Inflammatory Drugs ◽  
Common Problems ◽  
Anti Inflammatory ◽  
The Stability ◽  
And Function ◽  
Gad Activity

Unspecific and side effects caused by interaction with proteins belong to common problems of many structures synthesized as potential medicaments. Possible in vitro interactions with proteins of a group of phenylsulfonyl benzoic acid derivatives (VÚFB 19363, 19369, 19370, 19371, and 19760) as new potential anti-inflammatory compounds with antileukotrienic activities were studied in the present work. Three purified enzymes were used as model proteins with catalytic activities: Pig heart aspartate aminotransferase (AST, EC 2.6.1.1), alanine aminotransferase (ALT, EC 2.6.1.2), and glutamate decarboxylase (GAD, EC 4.1.1.15) from E. coli. Catalytic activities during incubation of individual compounds (6 x 10-5 M solution to 5 x 10-2 M suspension) at 37 °C with enzymes served as criteria of stability and function of the proteins. No immediate influence of any compound studied on enzyme activities was found. Aminotransferase activities were not affected even during incubation up to 20 d. In the case of GAD, the compounds VÚFB 19369, 19370, 19371, and 19760 had stabilizing influence on GAD activity during incubation at enzyme concentrations of 11.25 and 5.62 mg prot/l. The lack of an immediate effect of compounds and the stability of enzymes during incubation them are favorable and support the prospective of the compounds as potential drugs.

Photo-Induced Chromiumcarbonyl Catalyzed Hydrosilylation of Conjugated Dienes with Triethylsilane: The Solvent Effect

2003 ◽  
Vol 58 (7) ◽  
pp. 644-648 ◽  
Author(s):  
Ceyhan Kayran ◽  
Saim Özkar ◽  
Vagif M. Akhmedov
Keyword(s):  
Catalytic Activity ◽  
Solvent Effect ◽  
Active Catalyst ◽  
Conjugated Dienes ◽  
Catalytic Activities ◽  
Reaction Proceeds ◽  
The Stability ◽  
Reactivity Order ◽  
Sole Product ◽  
Hexane Solution

Photocatalytic hydrosilylation of conjugated dienes (1,3-butadiene, 2-methyl-1,3-butadiene, 2,3- dimethyl-1,3-butadiene, trans-1,3-pentadiene) with triethylsilane was studied by using Cr(CO)5L (L = CO, P(CH3)3, P(OCH3)3, P(C6H5)3, P(C6H11)3, NC5H5) in two very different solvents, toluene and tetrahydrofuran, for comparison with the results found in n-hexane. In toluene, the photocatalytic hydrosilylation yields the same products as those in n-hexane, with the exception of trans- 1,3-pentadiene which gives cis-1-triethylsilyl-2-pentene as the sole product. However, each of the precursor complexes shows different catalytic activities in toluene and n-hexane. The hydrosilylation of 1,3-butadiene in toluene is, in general, significantly faster than that in n-hexane. By using Cr(CO)6, Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3] in toluene, the conversion of triethylsilane increases almost linearly as the reaction proceeds, indicating the stability of the active catalyst throughout the reaction, similar to that in n-hexane. While no hydrosilylation of 1,3-butadiene could be achieved with Cr(CO)5[P(C6H5)3] or Cr(CO)5(NC5H5) in n-hexane, the same precursor complexes appear to be active in toluene, though the conversion occurs at much lower rate compared to that obtained using Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3]. The precursor complex Cr(CO)5[P(C6H11)3] shows catalytic activity neither in toluene nor in n-hexane. No photocatalytic hydrosilylation of 1,3-butadiene with triethylsilane was observed in tetrahydrofuran by using any of the precursor complexes. The relative reactivity of conjugated dienes in the hydrosilylation was investigated by using triethylsilane in the presence of Cr(CO)5[P(OCH3)3] as catalyst in toluene, and the same reactivity order was obtained as in n-hexane solution: 1,3-butadiene > 3-methyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > trans-1,3-pentadiene. For all of the dienes, one obtains higher conversion to hydrosilylated product in toluene than in n-hexane.

scholarly journals Greener and Sustainable Method for Alkene Epoxidations by Polymer-Supported Mo(VI) Catalysts

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Krzysztof Ambroziak ◽  
Rene Mbeleck ◽  
Basu Saha ◽  
David Sherrington
Keyword(s):  
Batch Reactor ◽  
Continuous Process ◽  
Reaction Conditions ◽  
Catalytic Activities ◽  
Tert Butyl Hydroperoxide ◽  
Heterogeneous Polymer ◽  
Terminal Alkene ◽  
Polymer Catalyst ◽  
The Stability ◽  
Epoxidation Of Alkenes

A polybenzimidazole supported Mo(VI) (PBI.Mo) catalyst has been prepared and characterised. The catalytic activities of the PBI.Mo catalyst in epoxidation of alkenes with tert-butyl hydroperoxide (TBHP) as an oxidant have been studied under different reaction conditions in a batch reactor. As alkene representatives we have chosen cyclohexene, limonene, ?-pinene and 1-octene (a less reactive terminal alkene). The order of reactivity of the alkenes was found to be: cyclohexene>limonene>?-pinene>1-octene. The stability of each polymer catalyst was assessed by recycling a sample in batch reaction using conditions that will form the basis of the continuous process. The loss of Mo from each support has been investigated by isolating any residue from the reaction supernatant solutions, following removal of the heterogeneous polymer catalyst, and then using the residues as potential catalysts in epoxidation reactions.

scholarly journals Inactivation of liver S-adenosylhomocysteine hydrolase in vitro of rats treated with erythro-9-(2-hydroxynon-3-yl)adenine

1982 ◽  
Vol 205 (3) ◽  
pp. 585-592 ◽  
Author(s):  
E O Kajander
Keyword(s):  
Adenosine Deaminase ◽  
Hydrolase Activity ◽  
Tissue Preparation ◽  
Adenosylhomocysteine Hydrolase ◽  
Tissue Homogenates ◽  
Liver Homogenates ◽  
The Stability ◽  
And Storage

S-Adenosylhomocysteine hydrolase activity decreased in vitro time-dependently in liver homogenates obtained from rats treated in vivo with erythro-9-(2-hydroxynon-3-yl)adenine, a potent inhibitor of adenosine deaminase. The inhibitor in itself had no effect on the stability of the hydrolase. The inactivation of S-adenosylhomocysteine hydrolase was irreversible, proceeded fairly rapidly at a low temperature (0 degrees C) and showed first-order reaction kinetics. Adenosine was found to accumulate in these tissue homogenates during storage. Several lines of evidence suggest that adenosine caused the observed suicide-like inactivation post mortem. Pre-incubation of purified S-adenosylhomocysteine hydrolase at 0 degrees C with adenosine showed a half-maximal inactivation rate at 33 microM substrate concentration; the rate constant of inactivation was 0.01 min-1. Inactivation during tissue preparation and storage complicates the assay of S-adenosylhomocysteine hydrolase activity in samples that contain an inhibitor of adenosine deaminase. These results also suggest that the decrease of S-adenosylhomocysteine hydrolase activity reported to occur in several disturbances of purine metabolism should be re-examined to exclude the possibility of inactivation of the enzyme in vitro.

High catalytic performance of raspberry-like gold nanoparticles and enhancement of stability by silica coating

RSC Advances ◽  
2015 ◽  
Vol 5 (24) ◽  
pp. 18977-18982 ◽  
Author(s):  
Hien Duy Mai ◽  
Kiouk Seo ◽  
Soon Choi ◽  
Hyojong Yoo
Keyword(s):  
Gold Nanoparticles ◽  
Silica Coating ◽  
Catalytic Performance ◽  
Ethanol Electrooxidation ◽  
Catalytic Activities ◽  
The Stability

Raspberry-like gold nanoparticles (Au RLNPs) show high catalytic activities in the reduction of 4-nitrophenol and ethanol electrooxidation. To improve the stability and applicability of Au RLNPs, silica-coated Au RLNPs were successfully synthesized.

Nitrogen Ligands on Gas-Phase Oxidation Carbonylation of Dimethyl Carbonate

2011 ◽  
Vol 366 ◽  
pp. 347-351
Author(s):  
Rui Li
Keyword(s):  
Dimethyl Carbonate ◽  
Copper Catalyst ◽  
Methanol Conversion ◽  
Nitrogen Ligand ◽  
Catalytic Activities ◽  
Nitrogen Ligands ◽  
Gas Phase Oxidation ◽  
Space Time Yield ◽  
The Stability ◽  
Supported Copper Catalyst

The effects of nitrogen ligands as pyridine, methylpyridine, 2, 2'-bipyridine and ethylenediamine on the activity and stability of the CBAC supported copper catalyst were investigated. The catalytic activities prepared by nitrogen ligand pretreatment descended compared with the unpretreated support catalysts. This probably related to the disfavored effect of the coordination on the catalysts at the gas-solid reaction manner. The catalysts made by pyridine pretreatment and pore modified supports were superior to the catalysts of unmodified CBAC. Methanol conversion, DMC selectivity and the space-time-yield of DMC of the catalysts by HCl, pyridine pretreatment and pore modification were 28.3%, 97.3% and 165.3 g/(kg•h), respectively. Activity test of 30h showed that pyridine pretreatment can prevent the loss of the active component and enhance the stability of the catalysts.

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