scholarly journals The Mechanism of the Tyrosine Transporter TyrP Supports a Proton Motive Tyrosine Decarboxylation Pathway in Lactobacillus brevis

2006 ◽  
Vol 188 (6) ◽  
pp. 2198-2206 ◽  
Author(s):  
Wout A. M. Wolken ◽  
Patrick M. Lucas ◽  
Aline Lonvaud-Funel ◽  
Juke S. Lolkema
Keyword(s):  
Phenyl Ring ◽  
Lactobacillus Brevis ◽  
Proton Motive Force ◽  
Proton Pumping ◽  
Hydroxyl Group ◽  
Transporter Gene ◽  
Tyrosine Decarboxylase ◽  
Rate Analysis ◽  
Substrate Analogues ◽  
Decarboxylation Reaction

ABSTRACT The tyrosine decarboxylase operon of Lactobacillus brevis IOEB9809 contains, adjacent to the tyrosine decarboxylase gene, a gene for TyrP, a putative tyrosine transporter. The two genes potentially form a proton motive tyrosine decarboxylation pathway. The putative tyrosine transporter gene of L. brevis was expressed in Lactococcus lactis and functionally characterized using right-side-out membranes. The transporter very efficiently catalyzes homologous tyrosine-tyrosine exchange and heterologous exchange between tyrosine and its decarboxylation product tyramine. Tyrosine-tyramine exchange was shown to be electrogenic. In addition to the exchange mode, the transporter catalyzes tyrosine uniport but at a much lower rate. Analysis of the substrate specificity of the transporter by use of a set of 19 different tyrosine substrate analogues showed that the main interactions between the protein and the substrates involve the amino group and the phenyl ring with the para hydroxyl group. The carboxylate group that is removed in the decarboxylation reaction does not seem to contribute to the affinity of the protein for the substrates significantly. The properties of the TyrP protein are those typical for precursor-product exchangers that operate in proton motive decarboxylation pathways. It is proposed that tyrosine decarboxylation in L. brevis results in proton motive force generation by an indirect proton pumping mechanism.

scholarly journals Complexation of Cu(BF4)2 with 3-hydroxyflavone in acetonitrile: quantum chemical calculation

2018 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Phenyl Ring ◽  
Fluorine Atom ◽  
Quantum Chemical Study ◽  
Hydroxyl Group ◽  
Chemical Calculation ◽  
Intramolecular Hydrogen

In the article the results of the quantum chemical study of copper (II) solvato-complexes with acetonitrile (AN), tetrafluoroborate anion (BF4–) and 3-hydroxyflavone (flv) of the composition [Cu(AN)6]2+, [Cu(BF4)(AN)5]+, [Cu(flv)(AN)5]2+, [Cu(flv)(BF4)(AN)4]+ are presented. Calculations were done using density function theory (DFT) on the M06-2X/6-311++G(d,p) level of theory. Obtained results were interpreted in terms of complexes geometry and topology of electron density distribution using non-covalent interactions (NCI) approach. It was shown that flv molecule is a monodentate ligand in copper (II) complexes and coordinates central atom via carbonyl oxygen. Intramolecular hydrogen bond that exists in an isolated flv molecule was found to be broken upon [Cu(flv)(AN)5]2+ complex formation. In [Cu(flv)(AN)5]2+ complex, a significant rotation of phenyl ring over the planar chromone fragment was spotted as a consequence of intramolecular hydrogen bond breaking. Upon inclusion of BF4– anion to the first solvation shell of Cu2+, an intracomplex hydrogen bond was formed between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion. NCI analysis had shown that a hydrogen bond between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion is significantly stronger than intramolecular hydrogen bond in an isolated flv molecule. In addition, flexible phenyl ring of flv molecule in [Cu(flv)(BF4)(AN)4]+ complex was found to be internally stabilized by the weak van der Waals attraction between oxygen atoms of chromone ring and phenyl hydrogens. These evidences led to a conclusion that [Cu(flv)(BF4)(AN)4]+ complex is more stable, comparing to the in [Cu(flv)(AN)5]2+ complex.

scholarly journals Synthesis and Evaluation of Antioxidant Properties of 2-Substituted Quinazolin-4(3H)-ones

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6585
Author(s):  
Janez Mravljak ◽  
Lara Slavec ◽  
Martina Hrast ◽  
Matej Sova
Keyword(s):  
Antioxidant Activity ◽  
Phenyl Ring ◽  
Biological Activities ◽  
Antioxidant Properties ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Ortho Position ◽  
Dpph Assay ◽  
Metal Chelating ◽  
Methoxy Substituent

Quinazolinones represent an important scaffold in medicinal chemistry with diverse biological activities. Here, two series of 2-substituted quinazolin-4(3H)-ones were synthesized and evaluated for their antioxidant properties using three different methods, namely DPPH, ABTS and TEACCUPRAC, to obtain key information about the structure–antioxidant activity relationships of a diverse set of substituents at position 2 of the main quinazolinone scaffold. Regarding the antioxidant activity, ABTS and TEACCUPRAC assays were more sensitive and gave more reliable results than the DPPH assay. To obtain antioxidant activity of 2-phenylquinazolin-4(3H)-one, the presence of at least one hydroxyl group in addition to the methoxy substituent or the second hydroxyl on the phenyl ring in the ortho or para positions is required. An additional ethylene linker between quinazolinone ring and phenolic substituent, present in the second series (compounds 25a and 25b), leads to increased antioxidant activity. Furthermore, in addition to antioxidant activity, the derivatives with two hydroxyl groups in the ortho position on the phenyl ring exhibited metal-chelating properties. Our study represents a successful use of three different antioxidant activity evaluation methods to define 2-(2,3-dihydroxyphenyl)quinazolin-4(3H)-one 21e as a potent antioxidant with promising metal-chelating properties.

scholarly journals Influence of catecholic ring torsion on hydroxyflavones

2020 ◽  
Vol 13 (1) ◽  
pp. 49-55
Author(s):  
Martin Michalík ◽  
Monika Biela ◽  
Denisa Cagardová ◽  
Vladimír Lukeš
Keyword(s):  
Gas Phase ◽  
Phenyl Ring ◽  
Density Functional ◽  
Hydroxyl Group ◽  
Torsional Deformation ◽  
Functional Theory ◽  
Electron Transitions ◽  
The Density Functional Theory ◽  
Intramolecular Hydrogen ◽  
Theoretical Results

AbstractSystematic quantum chemical investigation of quercetin and selected eight mono- and bihydroxyflavonols is presented. Structural analysis based on the Density Functional Theory showed that the energetically preferred conformation of flavonols substituted at the C5 and C3 atoms by a hydroxyl group is stabilised via intramolecular hydrogen bonds occurring between the (C4)O···HO(3 or 5) atomic pairs. Depending on the hydroxyl group positions, energetically preferred torsional orientation of the phenyl ring with respect to the planar benzo-γ-pyrone moiety changed from 0 to 180 degrees. Gas-phase electron transitions were investigated using the time-dependent DFT treatment. The dependence of maximal wavelengths on the torsional deformation of the phenyl ring is of a similar shape, i.e. minima observed for the perpendicular orientation and maxima for the planar one. Shape and energies of the Highest Occupied (HOMO) and Lowest Unoccupied (LUMO) Molecular Orbitals were compared. The obtained theoretical results were compared with available experimental data.

Competing photodehydration and excited-state intramolecular proton transfer (ESIPT) in adamantyl derivatives of 2-phenylphenols

2011 ◽  
Vol 89 (2) ◽  
pp. 221-234 ◽  
Author(s):  
Nikola Basarić ◽  
Nikola Cindro ◽  
Yunyan Hou ◽  
Ivana Žabčić ◽  
Kata Mlinarić-Majerski ◽  
...  
Keyword(s):  
Excited State ◽  
Carbon Atom ◽  
Proton Transfer ◽  
Phenyl Ring ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Intramolecular Proton Transfer ◽  
Hydroxyl Group ◽  
Quantum Yields

2-Phenylphenol derivatives strategically substituted with a hydroxyadamantyl substituent were synthesized and their photochemical reactivity was investigated. Derivatives 9 and 10 undergo competitive excited-state intramolecular proton transfer (ESIPT) from the phenol to the carbon atom of the adjacent phenyl ring and formal ESPT from the phenol to the hydroxyl group coupled with dehydration. These two processes (both via S1) give rise to two classes of quinone methides (QMs) that revert to starting material or react with nucleophiles, respectively. ESIPT to carbon atoms was studied by performing photolyses in the presence of D2O, whereupon deuterium incorporation to the adjacent phenyl ring was observed ([Formula: see text] = 0.1–0.2). The competing formal ESPT and dehydration takes place with quantum yields that are an order of magnitude lower and was studied by isolation of photomethanolysis products. Derivative 8 did not undergo ESIPT to carbon atom. Owing to the presence of an intramolecular H bond, an efficient ESIPT from the phenol to the hydroxyl group coupled with dehydration gives a QM that efficiently undergoes electrocyclization (overall [Formula: see text] = 0.33), to give chroman 16. In addition, spiro[adamantane-2,9′-(4′-hydroxy)fluorene] (12) undergoes ESIPT, unlike the previously reported unreactive parent 2-hydroxyfluorene. The reactive singlet excited states of the prepared biphenyl and fluorene molecules were characterized by fluorescence spectroscopy, whereas laser flash photolysis (LFP) was performed to characterize the longer lived QM intermediates.

scholarly journals Membrane-Bound ATPase Contributes to Hop Resistance of Lactobacillus brevis

2002 ◽  
Vol 68 (11) ◽  
pp. 5374-5378 ◽  
Author(s):  
Kanta Sakamoto ◽  
H. W. van Veen ◽  
Hiromi Saito ◽  
Hiroshi Kobayashi ◽  
Wil N. Konings
Keyword(s):  
Membrane Proteins ◽  
Atpase Activity ◽  
Lactobacillus Brevis ◽  
Proton Pumping ◽  
Enterococcus Hirae ◽  
Western Blots ◽  
Expression Levels ◽  
Beer Spoilage ◽  
Membrane Bound ◽  
Spoilage Bacterium

ABSTRACT The activity of the membrane-bound H+-ATPase of the beer spoilage bacterium Lactobacillus brevis ABBC45 increased upon adaptation to bacteriostatic hop compounds. The ATPase activity was optimal around pH 5.6 and increased up to fourfold when L. brevis was exposed to 666 μM hop compounds. The extent of activation depended on the concentration of hop compounds and was maximal at the highest concentration tested. The ATPase activity was strongly inhibited by N,N′-dicyclohexylcarbodiimide, a known inhibitor of FoF1-ATPase. Western blots of membrane proteins of L. brevis with antisera raised against the α- and β-subunits of FoF1-ATPase from Enterococcus hirae showed that there was increased expression of the ATPase after hop adaptation. The expression levels, as well as the ATPase activity, decreased to the initial nonadapted levels when the hop-adapted cells were cultured further without hop compounds. These observations strongly indicate that proton pumping by the membrane-bound ATPase contributes considerably to the resistance of L. brevis to hop compounds.

scholarly journals Synthesis, Characterization and Anticonvulsant Potential of 2,5-Disubstituted 1,3,4-Oxadiazole Analogues

2019 ◽  
Vol 31 (6) ◽  
pp. 1389-1397
Author(s):  
RAJNISH KUMAR ◽  
MOHD. MUSTAQEEM ABDULLAH
Keyword(s):  
Animal Model ◽  
Phenyl Ring ◽  
Anticonvulsant Activity ◽  
Hydroxyl Group ◽  
Strong Electron ◽  
Locomotor Behaviour ◽  
Toxicology Study ◽  
Electron Donating Groups ◽  
Weak Electron

A new series of compounds in which benzimidazole, oxadiazole and quinoline were incorporated, was synthesized and investigated for their anticonvulsant activity. Some of the newly synthesized compounds have shown good anticonvulsant activity. Significant anticonvulsant potency of the prepared derivatives has been evaluated by minimal electroshock and subcutaneous pentylenetetrazole animal model methods. The structure of synthesized compounds indicated that the introduction of strong electron donating groups like methoxy, amino and hydroxyl group and weak electron withdrawing halogen at phenyl ring attached to 1,3,4-oxadiazole moiety causes improvement in anticonvulsant activity. Locomotor behaviour was evaluated by actophotometer and toxicology study was also performed to evaluate their significance as required anticonvulsant compounds.

scholarly journals Atomistic Insight into the Role of Threonine 127 in the Functional Mechanism of Channelrhodopsin-2

2019 ◽  
Vol 9 (22) ◽  
pp. 4905 ◽  
Author(s):  
David Ehrenberg ◽  
Nils Krause ◽  
Mattia Saita ◽  
Christian Bamann ◽  
Rajiv K. Kar ◽  
...  
Keyword(s):  
Schiff Base ◽  
Absorption Maximum ◽  
Light Adaptation ◽  
Resonance Raman Spectroscopy ◽  
Proton Pumping ◽  
Hydroxyl Group ◽  
Visible Absorption ◽  
Dark Light ◽  
Hydrogen Bonded

Channelrhodopsins (ChRs) belong to the unique class of light-gated ion channels. The structure of channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) has been resolved, but the mechanistic link between light-induced isomerization of the chromophore retinal and channel gating remains elusive. Replacements of residues C128 and D156 (DC gate) resulted in drastic effects in channel closure. T127 is localized close to the retinal Schiff base and links the DC gate to the Schiff base. The homologous residue in bacteriorhodopsin (T89) has been shown to be crucial for the visible absorption maximum and dark–light adaptation, suggesting an interaction with the retinylidene chromophore, but the replacement had little effect on photocycle kinetics and proton pumping activity. Here, we show that the T127A and T127S variants of CrChR2 leave the visible absorption maximum unaffected. We inferred from hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and resonance Raman spectroscopy that the hydroxylic side chain of T127 is hydrogen-bonded to E123 and the latter is hydrogen-bonded to the retinal Schiff base. The C=N–H vibration of the Schiff base in the T127A variant was 1674 cm−1, the highest among all rhodopsins reported to date. We also found heterogeneity in the Schiff base ground state vibrational properties due to different rotamer conformations of E123. The photoreaction of T127A is characterized by a long-lived P2380 state during which the Schiff base is deprotonated. The conservative replacement of T127S hardly affected the photocycle kinetics. Thus, we inferred that the hydroxyl group at position 127 is part of the proton transfer pathway from D156 to the Schiff base during rise of the P3530 intermediate. This finding provides molecular reasons for the evolutionary conservation of the chemically homologous residues threonine, serine, and cysteine at this position in all channelrhodopsins known so far.

Structure-activity relationships of anti-tyrosinase and antioxidant activities of cinnamic acid and its derivatives

2021 ◽  
Author(s):  
Jianmin Chen ◽  
Mengnan Ran ◽  
Meixia Wang ◽  
Xinying Liu ◽  
Siwan Liu ◽  
...  
Keyword(s):  
Cinnamic Acid ◽  
Phenyl Ring ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Structure Activity Relationships ◽  
Structure Activity ◽  
Ic50 Value

Abstract The related structure-activity relationships (SARs) of cinnamic acid and its derivates have not been studied in details yet. Herein, anti-tyrosinase and antioxidant activities of 18 compounds were evaluated. The results demonstrated that the substituents on the phenyl ring of cinnamic acid led to the enhancement of the inhibition on monophenolase and the weakening of the inhibition on diphenolase. Among these tested compounds, 9 was firstly discovered as a tyrosinase inhibitor in a reversible competitive manner with IC50 value of 68.6 ± 4.2 μM. Docking results demonstrated 9 located into the catalytic center of tyrosinase. Antioxidant assay indicated that only one hydroxyl group on the phenyl ring was not enough to possess the radical scavenging activity, and the number of hydroxyl groups may be more important. This study will be helpful for development of new cinnamic acid derivates as tyrosinase inhibitors and antioxidants with higher efficacy.

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