Characterization and Structure Elucidation of Binary Zr:Ti MEL Structure; Simultaneous Photodegradation/Removal of Organic–Inorganic Pollutants

The preparation of a series of different Ti/Zr MEL structure was performed successfully. Full characterization of the prepared materials was done using XRD, IR, DR, and SEM. The results show that the prepared materials contain only one crystalline phase (ZSM-11). The affinity of Zr to form the crystalline phase alone in a binary Zr/Ti synthesizing mixture was approved by SEM and elemental analysis results. The percentage of each active site was calculated. DR spectra were deconvoluted, and three active sites were supposed and quantified (tetragonal, octahedral, and crystalline). The mutual effect of ions (lead, copper, cobalt, and nickel) and methylene blue dye on the removal efficiency with and without ultraviolet irradiation was examined and fully characterized. The ions largely influence the photodegradation process, and a mechanism was formulated. Meanwhile, the presence of dye showed a negligible effect on the removal of ions.

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Multi-active Site Dynamics on a Molecular Cr/Co/Se Cluster Catalyst

10.26434/chemrxiv-2022-zkfsp ◽

2022 ◽

Author(s):

Jonathan Kephart ◽

Benjamin Mitchell ◽

Werner Kaminsky ◽

Alexandra Velian

Keyword(s):

Structural Analysis ◽

Active Site ◽

Resting State ◽

Active Sites ◽

Stepwise Mechanism ◽

Nitrene Transfer ◽

Catalytic Intermediates ◽

Edge Site ◽

Catalytically Active

This study provides detailed insights into the interconnected reactivity of the three catalytically active sites of an atomically precise nanocluster Cr3(py)3Co6Se8L6 (Cr3(py)3, L = Ph2PNTol–, Ph = phenyl, Tol = 4-tolyl). Catalytic and stoichiometric studies into tosyl azide activation and carbodiimide formation enabled the isolation and crystallographic characterization of key metal-nitrenoid catalytic intermediates, including the tris(nitrenoid) cluster Cr3(NTs)3, the catalytic resting state Cr3(NTs)3(CNtBu)3, and the mono(nitrenoid) cluster Cr3(NTs)(CNtBu)2. Nitrene transfer proceeds via a stepwise mechanism, with the three active sites engaging sequentially to produce carbodiimide. Comparative structural analysis and CNtBu bind-ing studies reveal that the chemical state of neighboring active sites regulates the affinity for substrates of an individual Cr-nitrenoid edge site, intertwining their reactivity through the inorganic support.

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Synthesis, Characterization and Biological Activates Studies of some New Derivatives From 2-aminoo-5-mercapto-1, 3, 4-thiadiazole

Baghdad Science Journal ◽

10.21123/bsj.15.1.48-56 ◽

2018 ◽

Vol 15 (1) ◽

pp. 48-56

Author(s):

Baghdad Science Journal

Keyword(s):

Active Sites ◽

Acetyl Chloride ◽

Azo Compounds ◽

Thiazole Ring ◽

Diazonium Salts ◽

Material Base ◽

Anhydrous Sodium Carbonate ◽

Full Characterization ◽

Ft Ir

In this work, thiadiazole derivatives were prepared by taking advantage of active sites in (2-amino-5-mercapto-1, 3, 4-thiadiazole) as a starting material base. The main heterocyclic compounds (1, 3, 4-thiadiazole, oxazole) etc, 2-amino-5-mercapto-1,3,4-thiadiazole compound (1) was prepared by cyclic closure of thiosemicarbazide compound with anhydrous sodium carbonate and carbon disulfide. Oxidation of (1) via hydrogen peroxide, to have (2) which was treated with chloro acetyl chloride to get (3). Preparation of thiazole ring (4) was from reacting of (3) with thiourea. Synthesis of diazonium salts (5) from compound (4) using sodium nitrite and HCl. Compound (5) reacted with different ester compounds to prepare a new azo compounds (6–8).Compound (3) reacts with viruses secondary amine to prepare compound (9–11). Full characterization of the synthesized compounds was done by using spectroscopic analysis such as FT-IR, 1H-NMR and C.H.N.S. technique.

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Characterization of the Interaction between the Nuclease and Reverse Transcriptase Activity of the Yeast Telomerase Complex

Molecular and Cellular Biology ◽

10.1128/mcb.20.18.6806-6815.2000 ◽

2000 ◽

Vol 20 (18) ◽

pp. 6806-6815 ◽

Cited By ~ 21

Author(s):

Hongwu Niu ◽

Jinqiang Xia ◽

Neal F. Lue

Keyword(s):

Reverse Transcriptase ◽

Active Site ◽

Active Sites ◽

Biochemical Properties ◽

Reverse Transcriptase Activity ◽

Transcriptase Activity ◽

Yeast Telomerase ◽

Enzyme Cleavage ◽

Enzyme Cleavage Site

ABSTRACT Telomerase is a ribonucleoprotein that mediates extension of the dG-rich strand of telomeres in most eukaryotes. Like telomerase derived from ciliated protozoa, yeast telomerase is found to possess a tightly associated endonuclease activity that copurifies with the polymerization activity over different affinity-chromatographic steps. As is the case for ciliate telomerase, primers containing sequences that are not complementary to the RNA template can be efficiently cleaved by the yeast enzyme. More interestingly, we found that for the yeast enzyme, cleavage site selection is not stringent, since blocking cleavage at one site by the introduction of a nonhydrolyzable linkage can lead to the utilization of other sites. In addition, the reverse transcriptase activity of yeast telomerase can extend either the 5′- or 3′-end fragment following cleavage. Two general models that are consistent with the biochemical properties of the enzyme are presented: one model postulates two distinct active sites for the nuclease and reverse transcriptase, and the other invokes a multimeric enzyme with each protomer containing a single active site capable of mediating both cleavage and extension.

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Characterization of Pic, a Secreted Protease ofShigella flexneri and EnteroaggregativeEscherichia coli

Infection and Immunity ◽

10.1128/iai.67.11.5587-5596.1999 ◽

1999 ◽

Vol 67 (11) ◽

pp. 5587-5596 ◽

Cited By ~ 219

Author(s):

Ian R. Henderson ◽

John Czeczulin ◽

Carlos Eslava ◽

Fernando Noriega ◽

James P. Nataro

Keyword(s):

Active Site ◽

Serine Proteases ◽

Active Sites ◽

Culture Supernatant ◽

Shigella Flexneri ◽

Secreted Protein ◽

Mature Protein ◽

Precursor Molecule ◽

Multifunctional Protein

ABSTRACT We have identified and characterized a secreted protein, designated Pic, which is encoded on the chromosomes of enteroaggregativeEscherichia coli (EAEC) 042 and Shigella flexneri 2457T. The product of the pic gene is synthesized as a 146.5-kDa precursor molecule which is processed at the N and C termini during secretion, allowing the release of a mature protein (109.8 kDa) into the culture supernatant. The deduced amino acid sequence of Pic shows high homology to autotransporter proteins, particularly a subgroup termed the SPATEs (serine protease autotransporters of the Enterobacteriaceae). Present in all members of this subgroup is a motif similar to the active sites of certain serine proteases. Pic catalyzes gelatin degradation, which can be abolished by disruption of the predicted proteolytic active site. Functional analysis of the Pic protein implicates this factor in mucinase activity, serum resistance, and hemagglutination. Our data suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.

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A STUDY ON KINETIC CHARACTERIZATION OF CHANNEL-BLOCKING MUTANTS IN BRADYRHIZOBIUM JAPONICUM UTILIZATION A

10.36106/ijar/0104723 ◽

2021 ◽

pp. 49-52

Author(s):

Anand Shanker Singh ◽

G. Radhika ◽

R. Praveen Kumar ◽

Debarshi Jana

Keyword(s):

Active Site ◽

Bradyrhizobium Japonicum ◽

Kinetic Data ◽

Active Sites ◽

Substrate Channeling ◽

Site Analysis ◽

Proline Utilization ◽

Channel Blocking ◽

Proline Utilization A

Proline utilization A (PutA) from Bradyrhizobium japonicum (BjPutA) is a bifunctional avoenzyme that catalyzes the oxidation of proline to glutamate using fused proline dehydrogenase (PRODH) and ∆1-pyrroline-5-carboxylate dehydrogenase (P5CDH) domains. Recent crystal structures and kinetic data suggest an intramolecular channel connects the two active sites, promoting substrate channeling of the intermediate P5C from the PRODH domain to the P5CDH domain. In this work several mutations were made along the channel in an effort to block passage of P5C to the second active site. Analysis of several site-specic mutants in the substrate channel of BjPutA revealed an important role for D779 in the channeling path. BjPutA mutants D779Y and D779W signicantly decreased the overall PRODH-P5CDH channeling reaction indicating that bulky mutations at residue D779 impede travel of P5C through the channel. Interestingly, D779Y and D779W also exhibited lower P5CDH activity, suggesting that exogenous P5C must enter the channel upstream of D779. Replacing D779 with a smaller residue (D779A) had no effect on the catalytic and channeling properties of BjPutA showing that the carboxylate group of D779 is not essential for channeling. An identical mutation at D778 (D778Y) did not impact BjPutA channeling activity. Thus, D779 is optimally orientated so that replacement with the larger side chains of Tyr/Trp blocks P5C movment through the channel. The kinetic data reveal not only that bulky mutations at residue D779 hinder passage of P5C to the second active site, but also P5C must use the channel to efciently access the P5CDH domain. Moreover, these mutants may be used to learn more about the hydrolysis event that is thought to take place within the channel

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Development of c-type lectin oriented surfaces for high avidity glycoconjugates: towards mimicking multivalent interactions on the cell surface

10.1101/780452 ◽

2019 ◽

Cited By ~ 2

Author(s):

Vanessa Porkolab ◽

Carlo Pifferi ◽

Ieva Sutkeviciute ◽

Stefania Ordanini ◽

Marwa Taouai ◽

...

Keyword(s):

Active Sites ◽

Direct Interaction ◽

High Avidity ◽

Binding Properties ◽

Binding Partner ◽

Full Characterization ◽

Wide Range ◽

Multivalent Interactions ◽

Binding Mechanisms

ABSTRACTMultivalent interactions between complex carbohydrates and oligomeric C-type lectins govern a wide range of immune responses. Up to date, standard SPR (surface plasmon resonance) competitive assays have largely been to evaluate binding properties from monosaccharide units (low affinity, mM) to multivalent elemental antagonists (moderate affinity, µM). Herein, we report typical case-studies of SPR competitive assays showing that they underestimate the potency of glycoclusters to inhibit the interaction between DC-SIGN and immobilized glycoconjugates. This paper describes the design and implementation of a SPR direct interaction over DC-SIGN oriented surfaces, extendable to other C-type lectin surfaces as such Langerin. This setup provides a microscopic overview of intrinsic avidity generation emanating simultaneously from multivalent glycoclusters and from DC-SIGN tetramers that are organized in nanoclusters on the cell membrane. For this purpose, covalent biospecific capture of DC-SIGN via StreptagII /StrepTactin interaction offers the preservation of tetrameric DC-SIGN and the accessibility/functionality of all active sites. From the tested glycoclusters libraries, we demonstrated that the scaffold architecture, the valency and the glycomimetic-based ligand are crucial to reach nanomolar affinities for DC-SIGN. The glycocluster 3.D illustrates the tightest binding partner in this set for a DC-SIGN surface (Kd= 18 nM). Moreover, the selectivity at monovalent scale of glycomimetic D can be easily analyzed at multivalent scale comparing its binding over different C-type lectin immobilized surfaces. This approach may give rise to novel insights into the multivalent binding mechanisms responsible to avidity and make a major contribution to the full characterization of the binding potency of promising specific and multivalent immunomodulators.

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Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE

Biochemical Journal ◽

10.1042/bj20040522 ◽

2004 ◽

Vol 382 (2) ◽

pp. 565-573 ◽

Cited By ~ 15

Author(s):

Guillaume RIVIÈRE ◽

Annie MICHAUD ◽

Laurence DELOFFRE ◽

Franck VANDENBULCKE ◽

Angélique LEVOYE ◽

...

Keyword(s):

Angiotensin Converting Enzyme ◽

Active Site ◽

Active Sites ◽

Chinese Hamster Ovary Cells ◽

Chinese Hamster ◽

Inhibitory Effect ◽

Converting Enzyme ◽

Ovary Cells

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T. tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.

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Characterization of an Abnormal Antithrombin (Milano 2) with Defective Thrombin Binding

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661681 ◽

1986 ◽

Vol 56 (03) ◽

pp. 349-352 ◽

Cited By ~ 2

Author(s):

A Tripodi ◽

A Krachmalnicoff ◽

P M Mannucci

Keyword(s):

Venous Thromboembolism ◽

Active Site ◽

Inhibitory Activity ◽

Antithrombin Iii ◽

Factor Xa ◽

Molecular Defect ◽

Affinity Adsorption ◽

Italian Family ◽

Crossed Immunoelectrophoresis

SummaryFour members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and halfnormal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus’ plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus’ plasma to human α-thrombin immobilized on sepharose beads revealed defective binding of the anti thrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

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A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

10.26434/chemrxiv.10008545.v2 ◽

2020 ◽

Author(s):

Travis Marshall-Roth ◽

Nicole J. Libretto ◽

Alexandra T. Wrobel ◽

Kevin Anderton ◽

Nathan D. Ricke ◽

...

Keyword(s):

Oxygen Reduction ◽

Active Sites ◽

Catalytic Properties ◽

Reduction Reaction ◽

Iron Phthalocyanine ◽

Electrochemical Studies ◽

Onset Potential ◽

Nitrogen Doped Carbon ◽

Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N4 pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N4 catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen2N2)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen2N2)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen2N2)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen2N2)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen2N2)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen2N2)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen2N2)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen2N2)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H2O2 production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen2N2)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.

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A Thorough Theoretical Exploration of Intriguing Characteristics of Cyclo[18]carbon: Geometry, Bonding Nature, Aromaticity, Weak Interaction, Reactivity, Excited States, Vibrations, Molecular Dynamics and Various Molecular Properties

10.26434/chemrxiv.11320130.v1 ◽

2019 ◽

Cited By ~ 2

Author(s):

Tian Lu ◽

Qinxue Chen ◽

Zeyu Liu

Keyword(s):

Molecular Dynamics ◽

Excited States ◽

Electronic Excitation ◽

Ring Structure ◽

Molecular Properties ◽

Molecular Vibration ◽

Full Characterization ◽

Long Time ◽

Almost All

Although cyclo[18]carbon has been theoretically and experimentally investigated since long time ago, only very recently it was prepared and directly observed by means of STM/AFM in condensed phase (Kaiser et al., Science, 365, 1299 (2019)). The unique ring structure and dual 18-center π delocalization feature bring a variety of unusual characteristics and properties to the cyclo[18]carbon, which are quite worth to be explored. In this work, we present an extremely comprehensive and detailed investigation on almost all aspects of the cyclo[18]carbon, including (1) Geometric characteristics (2) Bonding nature (3) Electron delocalization and aromaticity (4) Intermolecular interaction (5) Reactivity (6) Electronic excitation and UV/Vis spectrum (7) Molecular vibration and IR/Raman spectrum (8) Molecular dynamics (9) Response to external field (10) Electron ionization, affinity and accompanied process (11) Various molecular properties. We believe that our full characterization of the cyclo[18]carbon will greatly deepen researchers' understanding of this system, and thereby help them to utilize it in practice and design its various valuable derivatives.

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