Effects Of Inhibitory Amino Acids Research Articles

The effect of amino acid addition in CeO2-based slurry on SiO2/Si3N4 CMP: Removal rate selectivity, morphology, and mechanism research

The continuous reduction in feature size of integrated circuits has raised stricter material removal selectivity and surface quality requirements for the chemical mechanical polishing (CMP) process of shallow trench isolation (STI). To reduce surface defects, small-sized CeO2 abrasives are introduced into the CMP of STI. We investigated the impacts of three amino acids and their composites added to a 50 nm-sized CeO2 dispersion (pH maintained at 5) on the polishing of silicon dioxide and silicon nitride. The promoting or inhibitory effects of amino acids first increased and then decreased with increasing concentration. When 0.02 M lysine and 0.02 M glutamic acid were added to 0.5 wt% CeO2 dispersion, the best effect was achieved. At this time, the material removal rate (MRR) of SiO2 and Si3N4 were 2993.4 Å/min and 137.2 Å/min, respectively, with surface roughness of 0.108 nm and 0.142 nm in the 5 μm × 5 μm region. This study shows that amino acids promote the MRR of SiO2 primarily by enhancing the reactivity of Ce4+ by complexing with carboxyl groups. In contrast, amino acids inhibit the MRR of Si3N4 primarily by forming strong hydrogen bonds between the amino group and its surface, resulting in surface adsorption and suppressing the hydrolysis reaction. The CMP mechanisms of the three amino acids are similar, and the differences in their effects are mainly due to the varying numbers of amino and carboxyl groups they carry. The adsorption of three amino acids on SiO2 and Si3N4 surfaces was simulated by Materials Studio software, and the results were consistent with the experimental results. Finally, this paper explained the mechanism of action of amino acids at the microscopic level and provided some guidance on improving the performance of CeO2 slurry.

Addition of amino acids modulates the in vitro digestibility of corn starch

The addition of amino acids (AAs) including glycine (Gly), lysine (Lys) and glutamic acid (Glu) with different concentrations on starch morphological, physicochemical and in vitro digestion properties were studied. While AAs showed no effects on neither morphology nor crystalline characters, they all significantly influenced the starch relative crystallinity and swelling capacity in an order of Glu > Lys > Gly. For all samples, both fastly- and slowly- digestible starch fractions (SF and SS) were observed. While Glu and Gly increased SF content with a faster digestion rate, they reduced SS content with a slower digestion rate. On contrary, Lys reduced SF content and the digestion rate of SS. The inhibitory effects of AAs on starch retrogradation and enzyme activities, the acidic environment and Maillard reaction between starch phosphate monoester and Lys are responsible for altered starch digestibility. This study betters our understanding concerning how AAs interactions affect starch functional properties.

Natural Hydrophilic Amino Acids as Environment-Friendly Gas Hydrate Inhibitors for Carbon Capture and Sequestration

Carbon capture and sequestration using gas hydrates are receiving a great deal of attention as clean processes since hydrates produce water as a major byproduct. The formation of hydrates in pipelines for CO2 transport and oil/gas production systems is also of great importance due to safety and cost issues. The use of chemical additives is necessary to optimize operating temperature and pressure conditions for the proper control and management of hydrate formation. Accordingly, their potential environmental impacts have led to the surging demand for eco-friendly hydrate additives. Amino acids have been recognized as a promising class of hydrate inhibitors as they interact with water via hydrogen-bonding and electrostatic interactions. However, insufficient inhibitory effects of amino acids and low solubility in liquid water have been considered to limit their applications. In this work, we report the effective use of hydrophilic amino acids as promising inhibitors for CO2 hydrates. Superior inhibitory efficiency of l-serine is achieved by its hydroxy group, which lowers the water activity through hydrogen bonding, thus shifting hydrate formation conditions to lower-temperature and higher-pressure regions. When added at 0.1 mol %, l-serine retards hydrate formation kinetics primarily by disrupting the water hydrogen-bond network. The thermodynamic inhibitory effect of l-proline even exceeds that of methanol due to its abnormally high hydrophilicity originating from the unique structural characteristics, and it works at high concentrations as a dual-function inhibitor affecting both phase equilibria and formation kinetics. The use of amino acids is highly preferred as they are natural and biodegradable substances, and therefore the potential environmental risk can be minimized. The corrosion issue often caused by the use of salts can also be neglected. The high solubility of hydrophilic amino acids allows them to be applied for a wide range of temperature and pressure conditions required for carbon capture and sequestration processes using gas hydrates.

D-Serine inhibits the attachment and biofilm formation of methicillin-resistant Staphylococcus aureus

IntroductionAlthough therapeutic agents for methicillin-resistant Staphylococcus aureus (MRSA) are clinically available, MRSA infection is still a life-threatening disease. Bacterial attachment and biofilm formation contribute significantly to the initiation of MRSA infection. Controlling MRSA’s attachment and biofilm formation might reduce the frequency of MRSA infection. According to recent data, some amino acids can reduce MRSA’s attachment on plates; however, their precise inhibitory mechanisms remain unclear. Therefore, we explored the effect of the amino acids on bacterial adhesion and biofilm formation in vitro and in vivo MRSA infection models. MethodsWe tested the inhibitory effect of amino acids on MRSA and Escherichia coli (E. coli) in the attachment assay. Moreover, we evaluated the therapeutic potential of amino acids on the in vivo catheter infection model. ResultsAmong the amino acids, D-Serine (D-Ser) was found to reduce MRSA’s ability to attach on plate assay. The proliferation of MRSA was not affected by the addition of D-Ser; thus, D-Ser likely only played a role in preventing attachment and biofilm formation. Then, we analyzed the expression of genes related to attachment and biofilm formation. D-Ser was found to reduce the expressions of AgrA, SarS, IcaA, DltD, and SdrD. Moreover, the polyvinyl chloride catheters treated with D-Ser had fewer MRSA colonies. D-Ser treatment also reduced the severity of infection in the catheter-induced peritonitis model. Moreover, D-Ser reduced the attachment ability of E. coli. ConclusionD-Ser inhibits the attachment and biofilm formation of MRSA by reducing the expression of the related genes. Also, the administration of D-Ser reduces the severity of catheter infection in the mouse model. Therefore, D-Ser may be a promising therapeutic option for MRSA as well as E. coli infection.

Metabolite Regulatory Interactions Control Plant Respiratory Metabolism via Target of Rapamycin (TOR) Kinase Activation.

Respiration rate measurements provide an important readout of energy expenditure and mitochondrial activity in plant cells during the night. As plants inhabit a changing environment, regulatory mechanisms must ensure that respiratory metabolism rapidly and effectively adjusts to the metabolic and environmental conditions of the cell. Using a high-throughput approach, we have directly identified specific metabolites that exert transcriptional, translational, and posttranslational control over the nighttime O2 consumption rate (RN) in mature leaves of Arabidopsis (Arabidopsis thaliana). Multi-hour RN measurements following leaf disc exposure to a wide array of primary carbon metabolites (carbohydrates, amino acids, and organic acids) identified phosphoenolpyruvate (PEP), Pro, and Ala as the most potent stimulators of plant leaf RN Using metabolite combinations, we discovered metabolite-metabolite regulatory interactions controlling RN Many amino acids, as well as Glc analogs, were found to potently inhibit the RN stimulation by Pro and Ala but not PEP. The inhibitory effects of amino acids on Pro- and Ala-stimulated RN were mitigated by inhibition of the Target of Rapamycin (TOR) kinase signaling pathway. Supporting the involvement of TOR, these inhibitory amino acids were also shown to be activators of TOR kinase. This work provides direct evidence that the TOR signaling pathway in plants responds to amino acid levels by eliciting regulatory effects on respiratory energy metabolism at night, uniting a hallmark mechanism of TOR regulation across eukaryotes.

Amino Acids Inhibitory Effects and Mechanism on 2-Amino-1-Methyl-6-Phenylimidazo [4,5-b]Pyridine (PhIP) Formationin the Maillard Reaction Model Systems.

This study was to investigate the inhibitory effects of amino acids (AAs) on the formation of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) and to evaluate the inhibition mechanism of PhIP in Maillard model systems. Different AAs were individually added into model systems heat-treated at 180 °C/1 h. The PhIP, phenylacetaldehyde (PheAce), and pyrazines derivatives were determined using HPLC and GC-MS. AAs significantly reduced (P < 0.05) PhIP levels in a dose-dependent response, ranking as: Trp = Lys > Pro > Leu > Met > Val > Ile > Thr > Phe > Asp, at the highest molar ratio. The PheAce content was gradually reduced with increasing AAs levels, suggesting that AAs may inhibit PhIP formation through scavenging the available PheAce. A correlation between PhIP inhibition and PheAce-scavenging activity of AAs was observed when PheAce and AAs were heated. The variety and quantity of pyrazines formed are highly depending on the type of AAs.

Dissolution behavior of co-amorphous amino acid-indomethacin mixtures: The ability of amino acids to stabilize the supersaturated state of indomethacin

Arginine, phenylalanine, and tryptophan have been previously shown to improve the solid-state stability of amorphous indomethacin. The present study investigates the ability of these amino acids to prolong the supersaturation of indomethacin in both aqueous and biorelevant conditions either when freely in solution or when formulated as co-amorphous mixtures.The co-amorphous amino acid-indomethacin mixtures (molar ratio 1:1) and amorphous indomethacin were prepared by cryomilling. Dissolution and precipitation tests were performed in buffer solutions (pH 5 and 6.5) and in Fed and Fasted State Simulated Intestinal Fluids (FeSSIF and FaSSIF, respectively). Precipitation tests were conducted with the solvent shift method. The supersaturation stability of indomethacin and the precipitation inhibitory effect of amino acids were evaluated by calculating the supersaturation factor and the excipient gain factor, respectively.Biorelevant media exerted a significant effect on indomethacin solubility but had little effect on the supersaturation stability. Arginine had the most significant impact on the dissolution properties of indomethacin, but also phenylalanine and tryptophan stabilized supersaturation in some media when formulated as co-amorphous mixtures with indomethacin. Only arginine stabilized supersaturation without co-amorphization, an effect only observed in media of pH 6.5. The unique behavior of the arginine-indomethacin mixture was further demonstrated by the abrupt formation of a precipitate, when an excess physical mixture of arginine and indomethacin was added to FeSSIF (pH 6.5). The solid-state investigation of this precipitate indicated that it probably consisted of crystalline arginine-indomethacin salt with possibly some residual crystalline starting materials.

Umami taste receptor functions as an amino acid sensor via Gαs subunit in N1E‐115 neuroblastoma cells

The sensing of the nutritional level of the body fluid is pivotal for maintaining homeostasis in animals. However, it is not yet understood how the cells detect nutritional levels. In the present study, we examined the function of umami taste receptor, which has a dimeric protein structure composed of Tas1r1 and Tas1r3, as amino acid sensor in the cells. We found that deprivation of amino acids induced neurite outgrowth in N1E-115 cells. The neurite outgrowth was inhibited by almost all of the amino acids tested. To investigate the involvement of the umami taste receptor, siRNA against each of Tas1r1 or Tas1r3 was administered, resulting in suppression of the inhibitory effects of amino acids on neurite outgrowth. In addition, inosine 5'-monophosphate, which potentiates the response to amino acids in the taste cells, enhanced the inhibitory effect of glutamine on neurite outgrowth. These results suggest that Tas1r1 + 3 functions as an amino acid sensor in N1E-115 cells. Because glutamine increased intracellular cAMP concentration, we investigated the involvement of the Gαs subunit of the heterotrimeric G protein in signal transduction. The treatments to inhibit the Gαs subunit significantly suppressed the increase of intracellular cAMP concentration induced by glutamine and the inhibitory effect of amino acids on neurite outgrowth. In addition, the reagents for increasing intracellular cAMP concentration inhibited neurite outgrowth induced by deprivation of amino acids. We concluded that Tas1r1 + 3 functions as an amino acid sensor and activates the intracellular signaling pathway through the Gαs subunit in N1E-115 cells.

Effects of inhibitory amino acids on expression of GABAA Rα and glycine Rα1 in hypoxic rat cortical neurons during development

Recent studies suggest that GABA and glycine are protective to mature but toxic to immature cortical neurons during prolonged hypoxia. Since the action of these inhibitory amino acids is mediated by GABA and glycine receptors, the expression of these receptors is a critical factor in determining neuronal response to GABAA and glycine in hypoxia. Therefore, we asked whether in rat cortical neurons, 1) hypoxia alters the expression of the GABA and glycine receptors; 2) inhibitory amino acids change the course of GABA and glycine receptor expression; and 3) there are any differences between the immature and mature neurons. In cultured rat cortical neurons from day 4 (fourdays in vitro or DIV 4) to day 20 (DIV 20), we observed that 1) GABAARα and GlyRα1 underwent differential changes in expression during the development in vitro; 2) hypoxia for 3days decreased GABAARα and GlyRα1 density in the neurons in-between DIV 4 and DIV 20, but did not induce a major change in immature (DIV 4) and mature (DIV 20) neurons; 3) during normoxia GABA, glycine and taurine decreased GABAARα and GlyRα1 density in the immature neurons, but had a tendency to increase the density in the mature neurons, except for taurine; 4) under hypoxia, all these amino acids decreased GABAARα and GlyRα1 density in most groups of the immature neurons with a slight effect on the mature neurons; and 5) δ-opioid receptor activation with DADLE increased GABAARα and GlyRα1 density in both the immature and mature neurons under normoxia and in the mature neurons under hypoxic condition. These data suggest that inhibitory amino acids differentially regulate the expression of GABAA and glycine receptors in rat cortical neurons under normoxic and hypoxic conditions with major differences between the immature and mature neurons.

Amino acids exhibit anti-inflammatory effects in human monocytic leukemia cell line, THP-1 cells

The elemental diet is one of the effective therapies for inflammatory bowel disease. However, the mechanism remains unclear, and there have never been reports about the inhibitory effects of amino acids in human monocytes/macrophages. We investigated the inhibitory effects of amino acids on cytokine production or expression of adhesion molecules that are involved in inflammatory diseases, in human monocytes/macrophages. We examined the inhibitory effects of cysteine, histidine or glycine on the induction of nuclear factor-κB (NF-κB) activation, expression of intracellular adhesion molecule-1 (ICAM-1, CD54) and production of interleukin-8 (IL-8) in THP-1 cells, a human monocytic leukemia cell line, and peripheral blood mononuclear cells (PBMCs) stimulated with tumor necrosis factor-α (TNF-α). Cysteine, histidine and glycine significantly reduced the activation of NF-κB in THP-1 cells stimulated with TNF-α. In addition, cysteine and histidine significantly inhibited the expression of ICAM-1 and production of IL-8 in THP-1 cells and PBMCs. Our results suggest that cysteine and histidine exhibit anti-inflammatory effects in THP-1 cells, and may be responsible for the efficacy of treatment in inflammatory bowel diseases.

Unique Roles of Acidic Amino Acids in Phase Transformation of Calcium Phosphates

Although phase transformation is suggested as a key step in biomineralization, the chemical scenario about how organic molecules mediate inorganic phase transformations is still unclear. The inhibitory effect of amino acids on hydroxyapatite (HAP, the main inorganic component of biological hard tissues such as bone and enamel) formation was concluded by the previous biomimetic modeling based upon direct solution crystallization. Here we demonstrate that acidic amino acids, Asp and Glu, could promote HAP crystallization from its precursor crystal, brushite (DCPD). However, such a promotion effect could not be observed when the nonacidic amino acids were applied in the transformation-based HAP formation. We found that the specific modification of acidic amino acid on crystal-solution interfaces played a key role in the phase transition. The distinct properties between DCPD and HAP in the solution resulted in an interfacial energy barrier to suppress the spontaneous formation of HAP phase on DCPD phase. Different from the other amino acids, the carboxylate-rich amino acids, Asp and Glu, could modify the interfacial characteristics of these two calcium phosphate crystals to make them similar to each other. The experiments confirmed that the involvement of Asp or Glu reduced the interfacial energy barrier between DCPD and HAP, leading to a trigger effect on the phase transformation. An in-depth understanding about the unique roles of acidic amino acids may contribute to understanding phase transformation controls druing biomineralization.

In Human Endothelial Cells Amino Acids Inhibit Insulin-induced Akt and ERK1/2 Phosphorylation by an mTOR-dependent Mechanism

In several cellular systems, amino acids synergize with insulin in promoting protein synthesis through the activation of the protein kinases p70/S6-K and PHAS-1. Such activations are mediated by the upstream kinase: mammalian target of rapamycin (mTor). In this work we have investigated the intracellular pathways involved in insulin-induced and amino acid-induced p70/S6-K activations in human endothelial cells. In human umbilical vein endothelial cells, insulin induces the phosphorylation of p70/S6-K at 5 minutes decreasing thereafter, whereas amino acids alone or associated with insulin phosphorylate p70/S6-K at all the time points analyzed (60 minutes). Insulin and amino acids phosphorylate p70/S6-K by mTor-dependent and phosphotidylinositol 3-kinase-dependent mechanisms, whereas the mitogen-activated protein kinase pathway is involved only when p70/S6-K is activated by insulin. Insulin induces the phosphorylation of Akt and extracellular signal-regulated protein kinase (ERK) 1/2, whereas amino acids did not. Moreover, amino acids suppress the phosphorylations induced by insulin. The inhibitory effects of amino acids are reverted by the mTor inhibitor rapamycin. Insulin-induced phosphorylation of Akt (at 15 and 30 minutes) is not accompanied by the phosphorylation of the downstream kinase p70/S6-K, indicating the existence of a negative feedback at this level. Our data demonstrate that at the level of human endothelial cells, amino acids synergize with insulin in the phosphorylation of the kinase that lies downstream mTor, as p70/S6-K, whereas they inhibit the upstream kinases Akt and extracellular signal-regulated protein kinase 1/2 when activated by insulin, by an mTor-dependent mechanism.

A capillary electrophoresis detection scheme for underivatized amino acids based on luminol–BrO − chemiluminescence system

A novel chemiluminescence (CL) detection scheme has been developed for detecting underivatized amino acids following capillary electrophoresis (CE) separation. This detection was based on the inhibitory effect of amino acids on the CL reaction between luminol and BrO − in alkaline aqueous solution. Detection of amino acids was accomplished with a borate-based background electrolyte at pH 9.2. The luminol was used as a component of the separation carrier electrolyte. Parameters affecting CE–CL separation and detection, such as the pH value, the concentration of electrolyte and CL reagent on the resolution were optimized. The relative standard deviation for the analysis of amino acids was less than 1.5% for the migration time and 4% for the peak height. The mass limits of detection were from 7 to 144 fmol for the 7 amino acids. This method has been applied of 7 amino acids in amino acid injection.

Inhibitory effect of amino acids on Al pitting corrosion in 0.1m NaCl

The effect of some α-amino acids on the inhibition of pitting corrosion of Al in 0.1m NaCl solution was studied by the potentiodynamic technique. All inhibitors used shift the pitting potential (Ep) and the protection potential (Epp) towards more noble values. The order of effectiveness of the inhibitors was arginine>histidine>glutamine>asparagine>alanine>glycine. The adsorption of amino acids on platinum was investigated by cyclic voltammetry using a flow cell technique. The results confirm that the inhibition efficiency of the amino acids studied is due to their adsorption on the metal surface. Variation in inhibition efficiency with the structure of the compounds was interpreted in terms of the number of adsorption active centres in the molecule, the molecular size and the mode of adsorption.

What is the relationship between the metabolism of preimplantation embryos and their developmental competence?

What is the relationship between the metabolism of preimplantation embryos and their developmental competence?

Effects of inhibitory amino acids on the frequency components in sympathetic nerve discharge

The effects of the GABA antagonist picrotoxin and the glycine antagonist strychnine on the frequency components in sympathetic inferior cardiac nerve activity were observed. Picrotoxin (0.03–1.0 mg/kg) increased power in the 10-Hz component of sympathetic activity and produced a dramatic shift in the rhythm to higher frequencies. Only small changes were noted in the 2- to 6-Hz component. Strychnine produced a small generalized increase in power in both frequency bands in sympathetic activity. These data suggest that GABA may play an important role in the generation and maintenance of the 10-Hz rhythm in sympathetic activity while glycine likely inhibits activity at a site of convergence of the two rhythms in sympathetic activity.

GABA as an inhibitory transmitter in the pigeon isthmo-tectal pathway

In the present investigation, the effects of inhibitory amino acids and their antagonists were tested on isthmo-tectal projection in the pigeon. The majority of superficial tectal cells are inhibited following stimulation of the parvocellular division of nucleus isthmi. A smaller portion of tectal cells showed excitatory responses followed by an inhibitory period. Both inhibitory mechanisms are blocked by the specific γ-aminobutyric acid (GABA)-antagonist bicuculline but not by strychnine. Our results support the idea that GABA acts as an inhibitory neurotransmitter in the pigeon isthmo-tectal pathways.

Phencyclidine-binding sites in mouse cerebral cortex during development and ageing: effects of inhibitory amino acids

The binding of N-[1-(2- thienyl)cyclohexyl]-[ 3H]piperidine ([ 3H]TCP) to the phencyclidine-binding sites in the N-methyl-D-aspartate (NMDA) receptor complex-associated ion channel was characterized in cerebral cortical membranes from 3-day-old to 24-month-old mice. The binding was saturable, exhibiting only one binding component during the whole life-span studied. The maximal binding capacity B max, calculated per protein content, decreased during postnatal development until 3 months of age, remaining thereafter constant in ageing mice, thus indicating the greatest availability of phencyclidine-binding sites in the immature cerebral cortex. The binding contant K D increased during the first postnatal week, remained thereafter unchanged and increased again during the second year of life, indicating a decreased affinity of these receptor sites for the ligand. The general properties of the binding; potentiation by glutamate and NMDA, as well as by glycine in a strychnine-insensitive manner, prevailed during development and ageing, certain of the effects being however less pronounced in the immature brain. Taurine and β-alanine stimulated TCP binding, acting probably at the glycine modulatory site. The actions of these inhibitory amino acids were weak and inconsistent when compared to that of glycine. Since NMDA receptors have been suggested to be involved in neuronal plasticity and learning and memory processes, these modifications in the properties of cortical phencyclidine-binding sites might be of importance in the regulation of excitatory amino acid functions during development and ageing.

Responsiveness of RNA degradation to amino acids in cultured rat hepatocytes: Comparison with isolated rat hepatocytes

The role of amino acids in the regulation of RNA degradation was investigated in cultured hepatocytes from fed rats previously labeled in vivo with [6-14C]orotic acid. Rates of RNA degradation were determined between 42 and 48 h of culture from the release of radioactive cytidine in the presence of 0.5 mM unlabeled cytidine. The fractional rate was about 4.4 +/- 0.4%/h in the absence of amino acids (0x). The catabolism of RNA was decreased to basal level (1.5 +/- 0.3%/h) by the addition of amino acids at 10 times normal plasma concentration (10x). The inhibition of RNA degradation, expressed as percentage of maximal deprivation-induced response (0x minus 10x), averaged 60% at normal plasma levels of amino acids. The degree of responsiveness was greatly improved as compared to freshly isolated hepatocytes (20%) and was similar to the sensitivity previously observed with perfused livers. In cultured hepatocytes, the sensitivity of RNA degradation to amino acids was not affected by varying the volume of medium from 1 to 4 ml per dish. In freshly isolated hepatocytes, the inhibitory effect of amino acids was not modified by changing the cell density from 0.5 to 5 x 10(6) cells per ml. In the range of normal plasma concentration of amino acids, the low sensitivity of RNA degradation in isolated hepatocytes persisted with inhibition ranging from 10 to 20%. These findings suggest that the control of RNA degradation in both cultured and isolated hepatocytes is not affected by the total quantity of amino acids available in the medium, but their concentration is crucial. Electron microscopy observations and the inhibitory effect of 3-methyl-adenine in cultured rat hepatocytes partially confirmed the role of the lysosomal system in the increase of RNA degradation and its regulation by amino acids.

Inhibitory Effect of Amino Acids and Dipeptides on the Sensitized Photooxidation of Fats

AbstractThe protective effect of amino acids and dipeptides on the singlet molecular oxygen photo‐oxidation of soybean oil and thier FAME was investigated, in homogeneous media and in aqueous emulsions. Soybean oil was chosen as an example of fat due to its particular stability problem. In the presence of 10–100 ppm of the amino acids, photo‐oxidation of the fats in relatively concentrated solutions, was considerably retarded when exposed to visible light, with an added sensitizer. The study indicates that amino acids and peptides, could acd as protective agents against fats photo‐oxidation, specially in foods containing oxidizable non saturated fatty acids, constituted in many cases by emulsions, where fats can simultaneously be disolved with proteineaceous compounds.