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l-tyrosine

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https://www.readbyqxmd.com/read/29215606/cognitive-and-mood-effects-of-a-nutrient-enriched-breakfast-bar-in-healthy-adults-a-randomised-double-blind-placebo-controlled-parallel-groups-study
#1
David O Kennedy, Emma L Wightman, Joanne Forster, Julie Khan, Crystal F Haskell-Ramsay, Philippa A Jackson
OBJECTIVES: Few previous studies have assessed the effects of concomitant administration of multiple potentially psychoactive nutrients. METHODS: 95 healthy adult participants consumed either a nutrient enriched breakfast bar (containing α-Linolenic acid, l-tyrosine, l-theanine, vitamins, minerals and 21.5 mg of caffeine) or an isocaloric, macronutrient matched control bar for 56 days. Cognitive function and mood were assessed pre-dose and at 40- and 160-min post-dose on the 1st and 56th day of the intervention period...
December 7, 2017: Nutrients
https://www.readbyqxmd.com/read/29213160/isotope-effects-in-mechanistic-studies-of-l-tyrosine-halogen-derivatives-hydroxylation-catalyzed-by-tyrosinase
#2
Małgorzata Pająk, Marianna Kańska
The kinetic (KIE) and solvent (SIE) isotope effect methods were used to investigate the mechanism of enzymatic hydroxylation of halogenated derivatives of l-tyrosine to l-DOPA catalyzed by the enzyme tyrosinase (EC 1.14.18.1). The values of deuterium KIE and SIE were obtained using the non-competitive method with spectrophotometric measurements. The Lineweaver-Burk plots were used for determination of the inhibition mode of 3'-iodo-l-tyrosine. Based upon kinetic effects values the mechanism of action of enzyme tyrosinase was proposed...
2017: Journal of Radioanalytical and Nuclear Chemistry
https://www.readbyqxmd.com/read/29196539/biochemical-and-structural-analysis-of-substrate-specificity-of-a-phenylalanine-ammonia-lyase
#3
Se-Young Jun, Steven A Sattler, Gabriel S Cortez, Wilfred Vermerris, Scott E Sattler, ChulHee Kang
Phenylalanine ammonia-lyase (PAL) is the first enzyme of the general phenylpropanoid pathway catalyzing the nonoxidative elimination of ammonia from L-phenylalanine to give trans-cinnamate. In monocots, PAL also displays tyrosine ammonia lyase activity (TAL), leading to the formation of p-coumaric acid. The catalytic mechanism and substrate-specificity of a major PAL from Sorghum bicolor (SbPAL1), a strategic plant for bioenergy production, were deduced from crystal structures, molecular docking, site-directed mutagenesis, and kinetic and thermodynamic analyses...
December 1, 2017: Plant Physiology
https://www.readbyqxmd.com/read/29183854/serine-51-residue-of-citrobacter-freundii-tyrosine-phenol-lyase-assists-in-c-%C3%AE-proton-abstraction-and-transfer-in-the-reaction-with-substrate
#4
Maria V Barbolina, Vitalia V Kulikova, Marina A Tsvetikova, Natalia V Anufrieva, Svetlana V Revtovich, Robert S Phillips, Paul D Gollnick, Tatyana V Demidkina, Nicolai G Faleev
In the spatial structure of tyrosine phenol-lyase, the Ser51 residue is located in the active site of the enzyme. The replacement of Ser51 with Ala by site-directed mutagenesis led to a decrease of the kcat/Km parameter for reactions with l-tyrosine and 3-fluoro-l-tyrosine by three orders of magnitude, compared to wild type enzyme. For the elimination reactions of S-alkylcysteines, the values of kcat/Km decreased by an average of two orders of magnitude. The results of spectral studies of the mutant enzyme gave evidence for a considerable change of the chiral properties of the active site as a result of the replacement...
November 25, 2017: Biochimie
https://www.readbyqxmd.com/read/29173147/recent-developments-of-18f-fet-pet-in-neuro-oncology
#5
Barbara Muoio, Luca Giovanella, Giorgio Treglia
From the past decade to date several studies about O-(2-[18F]fluoroethyl)-L-tyrosine (18F-FET) positron emission tomography (PET) in brain tumours have been published in the literature. Objective The aim of this narrative review is to summarize the recent developments and the current role of 18F-FET PET in brain tumours according to recent literature data. Methods Main findings from selected recently published and relevant articles on the role of 18F-FET PET in neuro-oncology were described. Results 18F-FET PET may be useful in the differential diagnosis between brain tumours and non-neoplastic lesions and between low-grade and high-grade gliomas...
November 23, 2017: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/29164132/conserved-molecular-mechanism-of-tyra-dehydrogenase-substrate-specificity-underlying-alternative-tyrosine-biosynthetic-pathways-in-plants-and-microbes
#6
Craig A Schenck, Yusen Men, Hiroshi A Maeda
L-Tyrosine (Tyr) is an aromatic amino acid synthesized de novo in plants and microbes. In animals, Tyr must be obtained through their diet or synthesized from L-phenylalanine. In addition to protein synthesis, Tyr serves as the precursor of neurotransmitters (e.g., dopamine and epinephrine) in animals and of numerous plant natural products, which serve essential functions in both plants and humans (e.g., vitamin E and morphine). Tyr is synthesized via two alternative routes mediated by a TyrA family enzyme, prephenate, or arogenate dehydrogenase (PDH/TyrAp or ADH/TyrAa), typically found in microbes and plants, respectively...
2017: Frontiers in Molecular Biosciences
https://www.readbyqxmd.com/read/29159062/evaluation-of-factors-influencing-18f-fet-uptake-in-the-brain
#7
Antoine Verger, Carina Stegmayr, Norbert Galldiks, Axel Van Der Gucht, Philipp Lohmann, Gabriele Stoffels, Nadim J Shah, Gereon R Fink, Simon B Eickhoff, Eric Guedj, Karl-Josef Langen
PET using the amino-acid O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) is gaining increasing interest for brain tumour management. Semi-quantitative analysis of tracer uptake in brain tumours is based on the standardized uptake value (SUV) and the tumour-to-brain ratio (TBR). The aim of this study was to explore physiological factors that might influence the relationship of SUV of 18F-FET uptake in various brain areas, and thus affect quantification of 18F-FET uptake in brain tumours. Negative 18F-FET PET scans of 107 subjects, showing an inconspicuous brain distribution of 18F-FET, were evaluated retrospectively...
2018: NeuroImage: Clinical
https://www.readbyqxmd.com/read/29141443/effects-of-wavelength-fluence-and-dose-on-fragmentation-pathways-and-photoproduct-ion-yield-in-213%C3%A2-nm-and-266%C3%A2-nm-ultraviolet-photodissociation-experiments
#8
Simon Becher, Bernhard Spengler, Sven Heiles
Ultraviolet photodissociation tandem mass spectrometry is a powerful tool to investigate the structure of biomolecules, due to its ability to generate rich fragmentation patterns or bond selective cleavage, as a function of used laser wavelength, laser fluence, dose (number of accumulated laser pulses), and available chromophores. Herein, we report first results obtained with a newly developed two-wavelength (266 nm and 213 nm) ultraviolet photodissociation setup coupled to a Fourier-transform ion cyclotron resonance mass spectrometer...
January 1, 2017: European Journal of Mass Spectrometry
https://www.readbyqxmd.com/read/29134667/synthesis-and-carbonic-anhydrase-inhibition-of-tetrabromo-chalcone-derivatives
#9
Umit M Kocyigit, Yakup Budak, Fikret Eligüzel, Parham Taslimi, Deryanur Kılıç, İlhami Gulçin, Mustafa Ceylan
In the present study, human carbonic anhydrase (hCA) enzyme was purified and characterized from fresh blood human red cells by Sepharose-4B-l-tyrosine-sulfanilamide affinity gel chromatography. Secondly, a series of new tetrabromo chalcone derivatives containing 4,7-methanoisoindol-1,3-dione (2a-i) were synthesized from the addition of Br2 to related chalcone derivatives (1a-i). The structures of the new molecules (2a-i) were confirmed by means of (1) H NMR, (13) C NMR and elemental analysis. Finally, the inhibitory effects of 2a-i on CA activities were investigated using the esterase method under in vitro conditions...
November 14, 2017: Archiv der Pharmazie
https://www.readbyqxmd.com/read/29131471/the-toxicological-effects-of-some-avermectins-on-goat-liver-carbonic-anhydrase-enzyme
#10
Cuneyt Caglayan, İlhami Gulcin
Avermectins are used worldwide as antiparasitic drugs in the field of veterinary medicine and as agricultural pesticides and insecticides. Carbonic anhydrase (CA, E.C. 4.2.1.1) is a zinc-containing metalloenzyme that catalyzes the reversible hydration of carbon dioxide (CO2 ) to yield protons (H(+) ) and bicarbonate (HCO3(-) ). In this study, some avermectins, including abamectin, doramectin, eprinomectin, and moxidectin, were investigated for in vitro inhibitory effects on the CA enzyme purified from goat liver, which was purified (125...
November 13, 2017: Journal of Biochemical and Molecular Toxicology
https://www.readbyqxmd.com/read/29121440/d-tyrosine-negatively-regulates-melanin-synthesis-by-competitively-inhibiting-tyrosinase-activity
#11
Jisu Park, Hyejung Jung, Kyuri Kim, Kyung-Min Lim, Ji-Young Kim, Eek-Hoon Jho, Eok-Soo Oh
Although L-tyrosine is well known for its melanogenic effect, the contribution of D-tyrosine to melanin synthesis was previously unexplored. Here, we reveal that, unlike L-tyrosine, D-tyrosine dose-dependently reduced the melanin contents of human MNT-1 melanoma cells and primary human melanocytes. In addition, 500 μM of D-tyrosine completely inhibited 10 μM L-tyrosine-induced melanogenesis, and both in vitro assays and L-DOPA staining MNT-1 cells showed that tyrosinase activity is reduced by D-tyrosine treatment...
November 9, 2017: Pigment Cell & Melanoma Research
https://www.readbyqxmd.com/read/29120077/self-assembled-nanomicelles-as-mri-blood-pool-contrast-agent
#12
Andrej Babic, Vassily Vorobiev, Celine Xayaphoummine, Gaelle Lapicorey, Anne-Sophie Chauvin, Lothar Helm, Eric Allémann
Gadolinium-loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd-complexes. Their size and stealth properties are fundamental for their long blood residence time opening the possibility for use as blood-pool contrast agents. Using L-tyrosine as a three-functional scaffold we synthesized a nanostructure building block 8. The double C18 aliphatic chain on one side, Gd-DO3A with access to bulk water in the center and 2 kDa PEG on the hydrophilic side gave the amphiphilic properties required for the core-shell nanomicellar architecture...
November 9, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29117379/inhibitory-effect-of-indole-analogs-against-paenibacillus-larvae-the-causal-agent-of-american-foulbrood-disease
#13
Israel Alvarado, Joseph W Margotta, Mai M Aoki, Fernando Flores, Fresia Agudelo, Guillermo Michel, Michelle M Elekonich, Ernesto Abel-Santos
Paenibacillus larvae, a Gram-positive bacterium, causes American foulbrood (AFB) in honey bee larvae (Apis mellifera Linnaeus [Hymenoptera: Apidae]). P. larvae spores exit dormancy in the gut of bee larvae, the germinated cells proliferate, and ultimately bacteremia kills the host. Hence, spore germination is a required step for establishing AFB disease. We previously found that P. larvae spores germinate in response to l-tyrosine plus uric acid in vitro. Additionally, we determined that indole and phenol blocked spore germination...
September 1, 2017: Journal of Insect Science
https://www.readbyqxmd.com/read/29097931/uptake-of-18-f-fet-and-18-f-fch-in-human-glioblastoma-t98g-cell-line-after-irradiation-with-photons-or-carbon-ions
#14
Francesca Pasi, Marco Giovanni Persico, Federica Eleonora Buroni, Carlo Aprile, Marina Hodolic, Franco Corbella, Rosanna Nano, Angelica Facoetti, Lorenzo Lodola
The differential diagnosis between recurrence of gliomas or brain metastases and this phenomenon is important in order to choose the best therapy and predict the prognosis but is still a big problem for physicians. The new emerging MRI, CT, and PET diagnostic modalities still lack sufficient accuracy. Radiolabeled choline and amino acids have been reported to show great tumor specificity. We studied the uptake kinetics of [(18)F]fluoromethyl-choline (FCH) and O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) by the T98G human glioblastoma cells from 20 to 120 min after irradiation either with photons at 2-10-20 Gy or with carbon ions at 2 Gy (at the National Centre for Oncological Hadrontherapy (CNAO), Pavia, Italy)...
2017: Contrast Media & Molecular Imaging
https://www.readbyqxmd.com/read/29081262/virtual-identification-of-novel-ppar%C3%AE-%C3%AE-dual-agonists-by-scaffold-hopping-of-saroglitazar
#15
Wen-Qing Jia, Zhi Jing, Xin Liu, Xiao-Yan Feng, Ya-Ya Liu, Shu-Qing Wang, Wei-Ren Xu, Jian-Wen Liu, Xian-Chao Cheng
The thiazolidinedione class PPARγ agonists as antidiabetic agents are restricted in clinical use because of the side effects such as edema, weight gain, and heart failure. The single and selective agonism of PPARγ is the main cause of side effects. The multi-target cooperative PPARα/γ dual agonist development is a hot topic in the antidiabetic medicinal chemistry field. Saroglitazar is the first approved PPARα/γ dual agonist, available in India for the treatment of diabetic dyslipidemia. It got rid of these side effects...
October 28, 2017: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/29080428/enzymatic-syntheses-of-3-halotyramines-selectively-2-h-and-3-h-labeled-in-the-side-chain
#16
Małgorzata Pająk, Marianna Kańska
3'-Halotyramines, stereo-selectively labeled with deuterium and tritium, in the (1R) or (1S) position were synthesized using enzymatic methods. The isotopomers labeled in the (1R) position were synthesized by enzymatic decarboxylation of an appropriate 3'-halo-L-tyrosine in deuterated or tritiated incubation medium. The isotopomers labeled in the (1S) position were synthesized by decarboxylation of an appropriate 3'-halo-L-tyrosine, labeled with deuterium or tritium in the α-position of the side chain.
October 16, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29076908/aids-related-central-nervous-system-toxoplasmosis-with-increased-18f-fluoroethyl-l-tyrosine-amino-acid-pet-uptake-due-to-lat1-2-expression-of-inflammatory-cells
#17
Markus Hutterer, Elisabeth Bumes, Markus J Riemenschneider, Jirka Grosse, Dirk Hellwig, Norbert Galldiks, Karl-Josef Langen, Peter Hau
We report the case of a 40-year-old woman with a progressive right-sided hemiparesis. Standard MRI revealed a contrast-enhancing brain lesion within the left basal ganglia. Ffluoroethyl-L-tyrosine (F-FET) PET showed a distinct tracer uptake (lesion-to-brain ratio [LBR]: LBRmax = 2.03, LBRmean = 1.68) with a significant larger metabolic lesion volume than contrast-enhancement in MRI, indicating cerebral glioma. Surprisingly, histopathologic analysis demonstrated central nervous system toxoplasmosis with pronounced inflammatory reaction (reactive astrogliosis, microglia activation, macrophage, and T-lymphocyte infiltration), which was associated with strong LAT1/LAT2/CD98 expression...
October 26, 2017: Clinical Nuclear Medicine
https://www.readbyqxmd.com/read/29073504/a-highly-versatile-automatized-setup-for-quantitative-measurements-of-phip-enhancements
#18
Alexey S Kiryutin, Grit Sauer, Sara Hadjiali, Alexandra V Yurkovskaya, Hergen Breitzke, Gerd Buntkowsky
The design and application of a versatile and inexpensive experimental extension to NMR spectrometers is described that allows to carry out highly reproducible PHIP experiments directly in the NMR sample tube, i.e. under PASADENA condition, followed by the detection of the NMR spectra of hyperpolarized products with high spectral resolution. Employing this high resolution it is feasible to study kinetic processes in the solution with high accuracy. As a practical example the dissolution of hydrogen gas in the liquid and the PHIP kinetics during the hydrogenation reaction of Fmoc-O-propargyl-l-tyrosine in acetone-d6 are monitored...
October 16, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29064707/l-carnosine-derived-fmoc-tripeptides-forming-ph-sensitive-and-proteolytically-stable-supramolecular-hydrogels
#19
Rita Das Mahapatra, Joykrishna Dey, Richard G Weiss
A series of β-amino acid containing tripeptides has been designed and synthesized in order to develop oligopeptide-based, thermoreversible, pH-sensitive, and proteolytically stable hydrogels. The Fmoc [N-(fluorenyl-9-methoxycarbonyl)]-protected tripeptides were found to produce hydrogels in both pH 7 and 2 buffers at a very low concentration (<0.2% w/v). It has been shown that the Fmoc group plays an important role in the gelation process. Also a dependence of gelation ability on hydrophobicity of the side chain of the Fmoc-protected α-amino acid was observed...
November 3, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29063090/amino-acid-crown-ether-hybrid-materials-how-charge-affects-liquid-crystalline-self-assembly
#20
Korinna Bader, Manuel M Neidhardt, Tobias Wöhrle, Robert Forschner, Angelika Baro, Frank Giesselmann, Sabine Laschat
To probe the influence of electrostatic interactions on the mesomorphic self-assembly and phase behaviour of hybrid liquid crystals a series of crown ether/tyrosine hybrid systems was prepared by Steglich esterification of alkyl N-(tert-butoxycarbonyl)-l-tyrosinates with 4-carboxybenzo[15]crown-5 and 4-carboxybenzo[18]crown-6. The obtained derivatives allowed further manipulations at the NH functional group and complexation of the crown ether unit with NaI to give neutral or charged hybrid materials. All compounds were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) measurements...
November 22, 2017: Soft Matter
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