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Marc Hendrickx - One of the best experts on this subject based on the ideXlab platform.
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influence of thermal processing on hydrolysis and stability of folate poly γ Glutamates in broccoli brassica oleracea var italica carrot daucus carota and tomato lycopersicon esculentum
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ivan Muzira Mukisa, Ann Van Loey, Marc HendrickxAbstract:The folate poly-γ-Glutamate profile, their concentrations, and hydrolysis by endogenous γ-glutamyl hydrolase (GGH) were evaluated in broccoli, carrot and tomato. Further studies on the effect of time and temperature on folate poly-γ-Glutamate hydrolysis and stability were carried out in broccoli since this vegetable showed the highest long-chain and total folate poly-γ-Glutamate concentration. The evolution of l-ascorbic acid, total phenols and Trolox equivalent antioxidant capacity (TEAC) values was evaluated in parallel. Upon thermal inactivation of GGH prior to crushing, it was observed that broccoli, carrot and tomato contained poly-γ-Glutamates with one to seven Glutamate residues but differed in the predominant poly-γ-Glutamates. Crushing of raw broccoli, carrot and tomato resulted in significant poly-γ-Glutamate profile changes in broccoli and carrot (indicating GGH-catalyzed hydrolysis) but not in tomato. In this study, the actual crushing of raw broccoli matrix had a greater effect on folate poly...
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acidification crushing and thermal treatments can influence the profile and stability of folate poly γ Glutamates in broccoli brassica oleracea l var italica
Food Chemistry, 2009Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ann Van Loey, Marc HendrickxAbstract:The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-Glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-Glutamate profile, endogenous folate poly-γ-Glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-Glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoGlutamate, di- and tri-γ-Glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-Glutamates. Regarding folate poly-γ-Glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-Glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoGlutamate content of broccoli.
Ann Wambui Munyaka - One of the best experts on this subject based on the ideXlab platform.
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influence of thermal processing on hydrolysis and stability of folate poly γ Glutamates in broccoli brassica oleracea var italica carrot daucus carota and tomato lycopersicon esculentum
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ivan Muzira Mukisa, Ann Van Loey, Marc HendrickxAbstract:The folate poly-γ-Glutamate profile, their concentrations, and hydrolysis by endogenous γ-glutamyl hydrolase (GGH) were evaluated in broccoli, carrot and tomato. Further studies on the effect of time and temperature on folate poly-γ-Glutamate hydrolysis and stability were carried out in broccoli since this vegetable showed the highest long-chain and total folate poly-γ-Glutamate concentration. The evolution of l-ascorbic acid, total phenols and Trolox equivalent antioxidant capacity (TEAC) values was evaluated in parallel. Upon thermal inactivation of GGH prior to crushing, it was observed that broccoli, carrot and tomato contained poly-γ-Glutamates with one to seven Glutamate residues but differed in the predominant poly-γ-Glutamates. Crushing of raw broccoli, carrot and tomato resulted in significant poly-γ-Glutamate profile changes in broccoli and carrot (indicating GGH-catalyzed hydrolysis) but not in tomato. In this study, the actual crushing of raw broccoli matrix had a greater effect on folate poly...
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acidification crushing and thermal treatments can influence the profile and stability of folate poly γ Glutamates in broccoli brassica oleracea l var italica
Food Chemistry, 2009Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ann Van Loey, Marc HendrickxAbstract:The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-Glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-Glutamate profile, endogenous folate poly-γ-Glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-Glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoGlutamate, di- and tri-γ-Glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-Glutamates. Regarding folate poly-γ-Glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-Glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoGlutamate content of broccoli.
David Attwell - One of the best experts on this subject based on the ideXlab platform.
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Tonic release of Glutamate by a DIDS-sensitive mechanism in rat hippocampal slices
J PHYSIOL-LONDON, 2005Co-Authors: David AttwellAbstract:Tonic release of Glutamate into the extracellular space of the hippocampus and striatum is non-vesicular, and has been attributed largely to a cystine-Glutamate exchanger which is blockable by the Glutamate analogue (S)-4-carboxyphenylglycine (CPG). Tonic Glutamate release may be functionally important: modulation of this release in the striatum has been suggested to underlie relapse in the use of cocaine. We monitored tonic Glutamate release in area CA1 of hippocampal slices by measuring the Glutamate receptor-mediated current evoked in pyramidal cells on block of Na+-dependent Glutamate uptake with DL-threo-beta-benzyloxyaspartate (TBOA). Superfused cystine increased tonic Glutamate release, and this increase was blocked by CPG, but CPG did not affect tonic Glutamate release in the absence of superfused cystine. Tonic Glutamate release was not affected by blocking gap junctional hemichannels with 18 alpha-glycyrrhetinic acid, blocking ATP receptors with pyridoxal-phosphate-6-azophenyl-2,4'-disulphonic acid (PPADS), blocking Ca2+-dependent exocytosis from neurones with Cd2+ or bafilomycin, blocking Ca2+-dependent release from glia with indomethacin, or blocking anion channels with 5-nitro-2-(3-phenylpropyl amino) benzoic acid (NPPB) or tamoxifen. However tonic Glutamate release was reduced by 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS), and was potentiated by inhibiting astrocytic conversion of Glutamate to glutamine with methionine sulfoximine. These data suggest that although cystine-Glutamate exchange is present in the hippocampus; it does not generate significant tonic release of Glutamate when the extracellular [cystine] is at a physiological level, and that tonic Glutamate release is at least partly from astrocytes and is mediated by a DIDS-sensitive mechanism. Theoretical calculations suggest that a significant fraction of tonic Glutamate release in hippocampal slices could occur via diffusion of Glutamate across lipid membranes.
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effect of acute exposure to ammonia on Glutamate transport in glial cells isolated from the salamander retina
Journal of Neurophysiology, 2001Co-Authors: Dominic Mort, Paikan Marcaggi, James Grant, David AttwellAbstract:A rise of brain ammonia level, as occurs in liver failure, initially increases Glutamate accumulation in neurons and glial cells. We investigated the effect of acute exposure to ammonia on glutamat...
Claudio Grosman - One of the best experts on this subject based on the ideXlab platform.
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side chain conformation at the selectivity filter shapes the permeation free energy landscape of an ion channel
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Tyler J Harpole, Claudio GrosmanAbstract:On the basis of single-channel currents recorded from the muscle nicotinic acetylcholine receptor (AChR), we have recently hypothesized that the conformation adopted by the Glutamate side chains at the first turn of the pore-lining α-helices is a key determinant of the rate of ion permeation. In this paper, we set out to test these ideas within a framework of atomic detail and stereochemical rigor by conducting all-atom molecular dynamics and Brownian dynamics simulations on an extensively validated model of the open-channel muscle AChR. Our simulations provided ample support to the notion that the different rotamers of these Glutamates partition into two classes that differ markedly in their ability to catalyze ion conduction, and that the conformations of the four wild-type Glutamates are such that two of them “fall” in each rotamer class. Moreover, the simulations allowed us to identify the mm (χ1 ≅ –60°; χ2 ≅ –60°) and tp (χ1 ≅ 180°; χ2 ≅ +60°) rotamers as the likely conduction-catalyzing conformations of the AChR’s selectivity-filter Glutamates. More generally, our work shows an example of how experimental benchmarks can guide molecular simulations into providing a type of structural and mechanistic insight that seems otherwise unattainable.
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the ring of Glutamates in the charge selectivity filter region of the nicotinic receptor forms a system of unanticipated complexity
Biophysical Journal, 2012Co-Authors: Gisela D Cymes, Claudio GrosmanAbstract:Of all the rings of ionizable side chains that decorate the permeation pathway of nicotinic-type receptors (AChRs), the ring of Glutamates at the intracellular end of M2 (the “intermediate ring”) is, by far, the one that lowers the energetic cost of cation permeation the most. Although these Glutamates have received much attention, several properties of this ring (such as the pH insensitivity) have remained unexplained, especially when compared to the properties of similar rings in CNG, Nav and Cav channels. To gain a more detailed understanding of this “catalytic” site, we performed a thorough mutational analysis of the intermediate ring of the muscle AChR (which consists of four Glutamates and one glutamine) using single-channel electrophysiology. Our results indicate that the commonly held idea that each Glutamate represents a negative charge and that each additional charge makes an incremental contribution to the single-channel conductance is incorrect: for example, we found that (in the wild-type channel) only two, not all four, of the Glutamates contribute to the single-channel conductance. And, in mutant muscle AChRs bearing five Glutamates in the ring (and thus mimicking the non-muscle type), only three Glutamates (not five) contribute to the conductance. Our data point to a model of unanticipated complexity in which the conformational dynamics of the Glutamate side chains (rather than their acid-base properties) in the ambivalent environment afforded by the membrane-water interface play a fundamental role in determining the amplitude of unitary currents.
Patrick Verlinde - One of the best experts on this subject based on the ideXlab platform.
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influence of thermal processing on hydrolysis and stability of folate poly γ Glutamates in broccoli brassica oleracea var italica carrot daucus carota and tomato lycopersicon esculentum
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ivan Muzira Mukisa, Ann Van Loey, Marc HendrickxAbstract:The folate poly-γ-Glutamate profile, their concentrations, and hydrolysis by endogenous γ-glutamyl hydrolase (GGH) were evaluated in broccoli, carrot and tomato. Further studies on the effect of time and temperature on folate poly-γ-Glutamate hydrolysis and stability were carried out in broccoli since this vegetable showed the highest long-chain and total folate poly-γ-Glutamate concentration. The evolution of l-ascorbic acid, total phenols and Trolox equivalent antioxidant capacity (TEAC) values was evaluated in parallel. Upon thermal inactivation of GGH prior to crushing, it was observed that broccoli, carrot and tomato contained poly-γ-Glutamates with one to seven Glutamate residues but differed in the predominant poly-γ-Glutamates. Crushing of raw broccoli, carrot and tomato resulted in significant poly-γ-Glutamate profile changes in broccoli and carrot (indicating GGH-catalyzed hydrolysis) but not in tomato. In this study, the actual crushing of raw broccoli matrix had a greater effect on folate poly...
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acidification crushing and thermal treatments can influence the profile and stability of folate poly γ Glutamates in broccoli brassica oleracea l var italica
Food Chemistry, 2009Co-Authors: Ann Wambui Munyaka, Patrick Verlinde, Ann Van Loey, Marc HendrickxAbstract:The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-Glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-Glutamate profile, endogenous folate poly-γ-Glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-Glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoGlutamate, di- and tri-γ-Glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-Glutamates. Regarding folate poly-γ-Glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-Glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoGlutamate content of broccoli.
