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This work describes the synthesis of sebacic acid capped silver nanoparticles (SA-AgNPs) by the wet chemical method for the detection of l -Histidine in blood serum and urine samples. The synthesized SA-AgNPs were characterized by several techniques. The obtained particles were spherical in shape and the average diameter was calculated by HR-TEM images to be 11 nm. Moreover, the synthesized SA-AgNPs were stable for more than 3 months in solution. The synthesized SA-AgNPs showed the surface plasmon resonance (SPR) band at 420 nm. Interestingly, after the addition of 18.1 μM of l -Histidine into the SA-AgNPs solution, the SPR band absorbance decreased and the colour of the solution changed from brown to colourless. Based on the changes in the SPR band, we calculated the lowest detection limit to be 122 nM. The observed colour shift and spectral changes were due to the aggregation of SA-AgNPs induced by l -Histidine via hydrogen bonding interaction. Additionally, a possible mechanism is discussed. Furthermore, a 268-fold excess of common interferences did not interfere with the detection of 18.1 μM of l -Histidine. We successfully applied the SA-AgNPs probe for the detection of l -Histidine in blood serum and urine samples. Further, we validated our system with the HPLC technique. Importantly, we prepared a portable smartphone aided paper-based kit for on-site monitoring of l -Histidine. We strongly hope that this facile synthesis of SA-AgNPs and the portable paper-based kit will represent a step forward in the field of biosensing and materials science.

L-Histidine (L-His) is an essential amino acid, which is used to synthesize proteins and enzymes. The concentration of L-His in the body is controlled to regulate tissue growth and repair of tissues. In this study, a rapid and sensitive method was developed for colorimetric L-his detection using Cu2+ ions to inhibit the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system. H2O2 can oxidize TMB to oxTMB in the presence of copper, and the change in color from colorless (TMB) to blue (oxTMB) is similar to that observed in the presence of peroxidase. However, because the imidazole ring and carboxyl group of L-His can coordinate with Cu2+ ions to form stable L-His–Cu2+ complexes, the color of the TMB–H2O2 solution remains unchanged after the addition of L-His. Therefore, because L-His effectively hinders the colorimetric reaction of TMB with H2O2, this assay can be used to quantitatively determine the concentration of L-His in samples. Under optimized conditions, our colorimetric sensor exhibited two linear ranges of 60 nM to 1 μM and 1 μM to 1 mM for L-His detection and a detection limit of 50 nM (S/N = 3); furthermore, the assay can be performed within 20 min. Moreover, the proposed assay was used to determine the concentration of L-His in urine samples, suggesting that this convenient and label-free colorimetric method presents promising applications in bioanalytical chemistry and clinical diagnosis.

Radiation-induced cardiopulmonary injuries are the most common and intractable side effects that are entwined with radiotherapy for thorax cancers. However, the therapeutic options for such complications have yielded disappointing results in clinical applications. Here, we reported that gut microbiota-derived l-Histidine and its secondary metabolite imidazole propionate (ImP) fought against radiation-induced cardiopulmonary injury in an entiric flora-dependent manner in mouse models. Local chest irradiation decreased the level of l-Histidine in fecal pellets, which was increased following fecal microbiota transplantation. l-Histidine replenishment via an oral route retarded the pathological process of lung and heart tissues and improved lung respiratory and heart systolic function following radiation exposure. l-Histidine preserved the gut bacterial taxonomic proportions shifted by total chest irradiation but failed to perform radioprotection in gut microbiota-deleted mice. ImP, the downstream metabolite of l-Histidine, accumulated in peripheral blood and lung tissues following l-Histidine replenishment and protected against radiation-induced lung and heart toxicity. Orally gavaged ImP could not enter into the circulatory system in mice through an antibiotic cocktail treatment. Importantly, ImP inhibited pyroptosis to nudge lung cell proliferation after radiation challenge. Together, our findings pave a novel method of protection against cardiopulmonary complications intertwined with radiotherapy in pre-clinical settings and underpin the idea that gut microbiota-produced l-Histidine and ImP are promising radioprotective agents.

Impaired skin wound healing in the elderly can lead to medical issues and increased mortality. Although l -histidine and l -carnosine are potent anti-aging amino acids, the wound healing effects of these amino acids in aging remain to be elucidated. Here, we investigated the regenerative potential of l -histidine and l -carnosine in in vitro and in vivo aging models. l -histidine (1 mM), l -carnosine (10 mM), or a combination improved proliferation, migration, senescence, and epithelial-mesenchymal transition (EMT) in d -galactose-induced aged keratinocytes. An in vivo mouse aging model was established with injection of d -galactose (s.c. 500 mg/kg) daily for eight weeks. Supplementation with l -histidine (2 g/L), l -carnosine (2 g/L), or a combination improved collagen and wound healing with EMT markers, E-cadherin, N-cadherin, and MMP-2. These effects were concomitant with reduced circulating levels of corticosterone and increased PI3K/Akt phosphorylation. These results suggest that l -histidine and l -carnosine have the potential to facilitate wound healing in aging skin.

The current study investigated the effect of dietary l-histidine and beta-alanine supplementation on growth performance, meat quality, carnosine content, and gene expression of carnosine-related enzymes in broilers. A two-factor design was adopted in this study. A total of 640 1-day-old male broilers were assigned to eight treatments with factorial arrangement containing four levels of l-histidine (0, 650, 1300, or 1950 mg/kg) and two levels of beta-alanine (0 or 1200 mg/kg) supplementation, 0 mg/kg histidine and/or 0 mg/kg were treated as control groups. Each treatment including eight replicates with 10 birds each and the feeding trial lasted for 42 days. Dietary supplementation with l-histidine and beta-alanine did not affect average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) of broilers during the grower (22–42 days) and the entire phase (1–42 days), compared with the control group (p &gt, 0.05). The only exception was a significantly reduced ADG in the 1950 mg/kg l-histidine group in the starter period (1–21 days, p &lt, 0.05). l-Histidine at 1950 mg/kg significantly decreased redness (a*) and yellowness (b*) values of the meat at 45 min postmortem (p &lt, 0.05), whereas it increased b* value and pH in breast muscle at 24 h postmortem. Moreover, dietary supplementation with beta-alanine alone or combination with l-histidine significantly increased ΔpH in breast muscle (p &lt, 0.01). Dietary l-histidine markedly increased total superoxide dismutase activity and total antioxidant capacity (T-AOC) both in breast muscle (p &lt, 0.01) and in plasma (p &lt, 0.01), and it decreased malondialdehyde (MDA) concentration in breast muscle (p &lt, 0.01). Dietary addition of beta-alanine, alone or combination, significantly increased T-AOC in breast muscle (p &lt, 0.01) and markedly decreased MDA content both in breast muscle and in plasma (p &lt, 0.01). Addition of l-histidine and beta-alanine significantly increased muscle peptide (carnosine and anserine) content (p &lt, 0.05) and upregulated the expression of carnosine synthase, transporter of carnosine/ l-histidine, and l-histidine decarboxylase genes (p &lt, 0.05), with greater change occurring in the combination group of 1300 mg/kg l-histidine and 1200 mg/kg beta-alanine. Overall, dietary l-histidine and beta-alanine could improve meat quality and antioxidant capacity, enhance the carnosine and anserine content, and upregulate the gene expression of carnosine synthesis-related enzymes in broilers.

Nutrient restriction is a challenging condition for the mammary glands of dairy cows. In this condition, supplementing amino acids and energy sources might be a good strategy to improve the concentration of one of the most important caseins in bovine milk. Therefore, the objective of this study was to investigate the effects of L-histidine (His) and sodium acetate (Ace) in a nutrient-restricted (NR) immortalized bovine mammary epithelial cell line (MAC-T cells). The treatments for the MAC-T cells are as follows: experiment (1) 0–5% diluted basal medium, experiment (2) supplementation of 0–9.6 mM of His or Ace in NR or normal conditions, experiment (3) supplementation of 0–9.6 mM of Ace plus 0.15 mM of His in NR or normal conditions. The 1% diluted medium showed no significant effect on the cell viability with the basal medium, thus, it was selected as the NR condition. The relative expression of β-casein was significantly increased in the NR condition with the inclusion of 0.15 mM His alone or with Ace compared to that in control. The supplementation of Ace increased the β-casein level under normal conditions. However, it did not change the expression of β-casein under the NR condition. The results suggest that His has the potential to increase the β-casein expression under the NR condition.

The organic compounds from biochar play a role of hormone analogs, stimulating the expression of metabolites by controlling related gene and protein. In this experiment, we reported the L-histidine biosysthesis was promoted by biochar treatment in E. coli unlike genetic engineering of the traditional method. The related results indicated the most optimal concentration was found to be 3%, and 7% is the lethal dose. E. coli was inhibited in the high-concentration treatment. On the other hand, docking technology was usually used as drug screening, basing on Lock-and-key model of protein in order to better understand mechanisms. So the organic compounds of biochar from GC-MS analysis that acted as ligands were connected to HisG protein controlling L-histidine biosysthesis in E. coli. The result showed that the three organic molecules interacted with HisG protein by hydrogen bond. So we considered that these three compounds play regulatory roles in L-histidine biosysthesis, and the hisG gene expression fully supports this conclusion.

The electrochemical oxidation of CA19-9 tagged with L-Histidine (CA199-His) was investigated for the first time with screen-printed electrodes (DS) modified with graphene oxide (DS/GO) or thermally reduced graphene oxide (DS/TRGO). Successive cyclic voltammograms (CV) measurements performed with bare and DS/TRGO electrodes proved that the intensity of the oxidation peak (I peak) is time-dependent. In fact, the oxidation signal increased over time, reached a maximum and then decreased due to the saturation of the surface with CA199-His molecules. The interaction of CA199-His with GO, TRGO, or graphite was additionally studied by isothermal calorimetry, a useful tool for accessing information regarding the biomolecule adsorption on graphene surface. The adsorption of CA199-His on TRGO was generating a higher heat, suggesting quantitative and efficient interactions. At the same time, in the case of TRGO, the saturation was not reached, indicating the existence of more free binding sites than in the case of GO and graphite. As such, the carbohydrate marker CA199-His showed a higher affinity for the TRGO surface than for the graphite or GO surfaces. The lack of saturation in the case of TRGO may indicate a continuous structural modification of the antigen when interacting with the graphene surface.

A new chelating agent, L-histidine-modified silica from rice husk (LHSRH), was prepared to increase the adsorption capacity and selectivity for Pb(II). LHSRH was synthesized by immobilizing L-histidine on silica from rice husk (RH) modified with 3-aminopropyltrimethoxysilane (APTMS). Silica from rice husk (SRH) was synthesized via precipitation process by adding hydrochloric acid solution to rice husk ash (RHA). The RHA was subsequently destructed with sodium hydroxide and heated to obtain sodium silicate (Na 2 SiO 3 ). SRH was characterized by Fourier transform infrared spectroscopy and x-ray diffraction. The LHSRH was used further to adsorp Pb(II) metal ion. The pH range, amount of adsorbent, and adsorption time were optimized by response surface methodology. The optimum condition for the adsorption of Pb(II) was pH 5, an amount of adsorbent 0.1 g; and adsorption time 15 minutes. The adsorption capacity for Pb(II) ion was found to be 62.5 mg/g. The adsorption behavior of the matrix followed the Langmuir’s model.

Background In the l-histidine (His) biosynthetic pathway of Escherichia coli, the first key enzyme, ATP-phosphoribosyltransferase (ATP-PRT, HisG), is subject to different types of inhibition. Eliminating the feedback inhibition of HisG by the His end product is an important step that enables the oversynthesis of His in breeding strains. However, the previously reported feedback inhibition-resistant mutant enzyme from E. coli, HisGE271K, is inhibited by purine nucleotides, particularly ADP and AMP, via competitive inhibition with its ATP substrate. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR), which is formed not only during His biosynthesis but also during de novo purine biosynthesis, acts as a natural analog of AMP and substitutes for it in some enzymatic reactions. We hypothesized that AICAR could control its own formation, particularly through the His biosynthetic pathway, by negatively influencing HisG enzymatic activity, which would make preventing ATP-PRT transferase inhibition by AICAR crucial for His overproduction. Results For the first time, both the native E. coli HisG and the previously described feedback-resistant mutant HisGE271K enzymes were shown to be sensitive to inhibition by AICAR, a structural analog of AMP. To circumvent the negative effect that AICAR has on His synthesis, we constructed the new His-producing strain EA83 and demonstrated its improved histidine production. This increased production was particularly associated with the improved conversion of AICAR to ATP due to purH and purA gene overexpression; additionally, the PitA-dependent phosphate/metal (Me2+-Pi) transport system was modified by a pitA gene deletion. This His-producing strain unexpectedly exhibited decreased alkaline phosphatase activity at low Pi concentrations. AICAR was consequently hypothesized inhibit the two-component PhoBR system, which controls Pho regulon gene expression. Conclusions Inhibition of a key enzyme in the His biosynthetic pathway, HisG, by AICAR, which is formed in this pathway, generates a serious bottleneck during His production. The constructed His-producing strain demonstrated the enhanced expression of genes that encode enzymes involved in the metabolism of AICAR to ATP, which is a substrate of HisG, and thus led to improved His accumulation. Electronic supplementary material The online version of this article (10.1186/s12934-018-0890-2) contains supplementary material, which is available to authorized users.

In the title salt, C6H10N3O2 +·I−, the cation is protonated at the imidazole ring and the amine group and deprotonated at the carboxylate group. The crystal packing features N—H...O and N—H...I hydrogen bonds.

This paper presents the results of two separate experiments, each involving 75 chickens of Cobb 500 provenience, divided into three experimental groups. During the last three weeks of fattening, chickens were fed finisher diets supplemented with amino acids β-alanine (0%, 0.5% and 1%) and L-histidine (0%, 0.3% and 0.5%) in different portions. After chickens have been slaughtered, 10 samples of breast tissue were taken from each group for carnosine content determination in muscle tissue and lipid oxidation expressed as TBARS. Analysis of THE results referring to carnosine concentration in breast muscle proved that supplementation of 0.5% L-histidine affected the carnosine concentration increase in breast muscles from 941.58 µg/g of tissue (H1) to 1186.06 µg/g of tissue (H3), while supplementation of 1% β-alanine influenced the increase in carnosine concentration from 756.15 µg/g of tissue (A1) to 911.01 µg/g of tissue (A3). Supplementation of amino acids did not have effects on TBARS values, but oxidation values decreased along with the supplementation of higher amounts of amino acids to diets, which was particularly expressed in samples stored for 60 days at -20°C. The experimental group H3 (0.5% L-histidine) exhibited 30.54% lower value of lipid oxidation than the control one H1 (0% L-histidine), while the group with 1% β-alanine (A3) had lipid oxidation value by 17.65% lower than the control group A1 (0% β- alanine).

The aim of this research was to investigate the deposition of carnosine in broiler muscles by feeding treatments comprising β-alanine, L- histidine, and magnesium oxide in various concentrations. The research was carried out on 120 Cobb 500 broilers divided into four groups. From weeks four to six, broilers were fed finisher mixtures as follows: P1, control group ; P2, 0.5% β-alanine + 0.24% MgO ; P3, 0.25% L- histidine + 0.24% MgO ; and P4, 0.20% β- alanine + 0.10% L- histidine + 0.24% MgO. This paper presents the weights of broilers and their carcasses, portions of main parts of carcasses, technological quality of breast muscles, and concentrations of carnosine in breast and thigh muscles. The following traits of muscle tissue quality were measured: initial and final pH value (45 min after slaughtering pH1, and 24 h after cooling pH2), drip loss, color (Minolta colorimeter, expressed as CIE L*, CIE a*, and CIE b* values), meat softness, and cooking loss. Data on relative concentration of protein carbonyl (nmol/mg protein) in the muscles of breasts and thighs and levels of thiobarbituric acid-reactive substances (TBARS) in fresh and frozen breasts muscles (nmol/mg of tissue) are presented. Statistical analysis proved that feeding treatments had an effect on the live weight of broilers in the 4th, 5th, and 6th weeks of fattening (P

Neurological, neurodegenerative, and psychiatric disorders represent a serious burden because of their increasing prevalence, risk of disability, and the lack of effective causal/disease-modifying treatments. There is a growing body of evidence indicating potentially favourable effects of carnosine, which is an over-the-counter food supplement, in peripheral tissues. Although most studies to date have focused on the role of carnosine in metabolic and cardiovascular disorders, the physiological presence of this di-peptide and its analogues in the brain together with their ability to cross the blood-brain barrier as well as evidence from in vitro, animal, and human studies suggest carnosine as a promising therapeutic target in brain disorders. In this review, we aim to provide a comprehensive overview of the role of carnosine in neurological, neurodevelopmental, neurodegenerative, and psychiatric disorders, summarizing current evidence from cell, animal, and human cross-sectional, longitudinal studies, and randomized controlled trials.

WOS: 000312984800009, Among different adsorbents, a new support for immobilized metal affinity chromatography was used for lysozyme separation from egg white. For this purpose, acrylamide, bisacrylamide, bentonite, and L-histidine in the presence of an initiator (azobisisobutyronitrile, AIBN) were mixed and bentonite-acrylamide-histidine microcomposites were prepared by bulk polymerization. Characterization studies were performed by SEM, FT-IR, XRD, and BET. Specific surface area of the bentonite and BABH microcomposite was found to be 33.4 and 1.42 m2/g, respectively. Cu2+ ions (20 mu mol/g) were chelated on these bentonite-acrylamide-histidine (50 mu mol/g L-histidine incorporation) microcomposites. The lysozyme adsorption capacity of the Cu2+ ions chelated microcomposites increased the lysozyme adsorption up to 100 mg/g while the lysozyme adsorption capacity of the bentonite-acrylamide-histidine was 24 mg/g. More than 89% of the adsorbed lysozyme was desorbed in 1 h in the desorption medium containing 1.0 M NaCl. Bentonite-acrylamide-histidine-Cu(II) was used for the purification of lysozyme from chicken egg white. The purity of lysozyme was estimated by SDS-PAGE. Specific activity of the purified lysozyme was found as 50,000 U/mg using Micrococcus lysodeikticus as substrate. The new metal-chelate affinity microcomposites were suitable for repeated use for five cycles without a noticeable loss of capacity., Research Fund of Cumhuriyet University, This work was supported by The Research Fund of Cumhuriyet University.

In this study, the stable conformers of neutral anserine were searched by molecular dynamics simulations and energy minimization calculations using the MM2 force field. Thermochemical calculations at B3LYP/6-31G(d) level of theory followed these preliminary calculations. The results confirmed that neutral anserine has quite a flexible structure and many stable gauche and trans conformers at room temperature. Nevertheless, two are considerably more favourable in energy than the others and expected to dominate the gas-phase and matrix IR spectra of the molecule. The corresponding structural and vibrational spectral data for these two conformers of neutral anserine, whose relative stabilities were also examined by high-accuracy energy calculations carried out using G3MP2B3 method, and for the most stable conformer of anserine in zwitterion form were calculated at B3LYP/6-311++G(d,p) level of theory. The calculated harmonic force constants were refined using the Scaled Quantum Mechanical Force Field (SQM-FF) method and then used to produce the refined wavenumbers, potential energy distributions (PEDs) and IR and Raman intensities. These refined data together with the scaled harmonic wavenumbers obtained using another method, Dual Scale factors (DS), enabled us to correctly analyse the observed IR and Raman spectra of anserine and revealed the effects of conformation and zwitterionic tautomerism on its structural and vibrational spectral data. (C) 2016 Elsevier B.V. All rights reserved.

In this study based on vibrational spectroscopic measurements and Density Functional Theory (OFF), we aimed for a reliable interpretation of the IR and Raman spectra recorded for anserine in the solid phase and water (H2O) and heavy water (D2O) solutions. Initial DFT calculations at the B3LYP/6-31G(d) searched possible conformers of the anserine zwitterion using a systematic conformational search. The corresponding equilibrium geometrical parameters and vibrational spectral data were determined for each of the stable conformers (in water) by the geometry optimization and hessian calculations performed at the same level of theory using the polarized continuum model (PCM). The same calculations were repeated to determine the most energetically preferred dimer structure for the molecule and the associated geometry, force field and vibrational spectral data. The harmonic force constants obtained from these calculations were scaled by the Scaled Quantum Mechanical Force Field (SQM) method and then used in the calculation of the refined wavenumbers, potential energy distributions, IR and Raman intensities. These refined theoretical data, which confirm the zwitterion structure for anserine in the solid phase or aqueous solvents, revealed the remarkable effects of intermolecular hydrogen bonding on the structural properties and observed IR and Raman spectra of this molecule. (C) 2015 Elsevier B.V. All rights reserved.

WOS: 000232393700017 Poly(2-hydroxyethyl methacrylate-co-N-methacryloly-L-histidinemethylester) poly(HEMA-MAH) microspheres was prepared via suspension polymerization. L-Histidine groups of the poly(HEMA-MAH) microspheres were then chelated with Ni(II) ions (poly(HEMA-MAH)-Ni(II)). Urease immobilization onto the poly(HEMA-MAH) and poly(HEMA-MAH)-Ni(II) microspheres from aqueous solutions was investigated in a batch system. The amount of immobilized urease on the poly(HEMA-MAH) and poly(REMA-MAH)-Ni(II) was 47.8 and 66.1 mg/g support, respectively. The values of Michaelis constants K-m for both immobilized urease preparations were significant higher than free enzyme, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for both immobilized urease preparations compared to free enzyme. However, the urease-immobilized onto the poly(HEMA-MAH)-Ni(II) resulted in an increase in enzyme stability with time. Optimum operational temperature for both immobilized preparations was 5.0 degrees C higher than that of the free enzyme and the temperature profiles of the immobilized preparations were significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed on the poly(HEMA-MAH) and poly(HEMA-MAH)-Ni(II) microspheres without loss of adsorption capacity or enzymic activity. Finally, a packed bed enzyme-reactor with/urease-immobilized poly(HEMA-MAH)-Ni(II) microspheres, were used for degradation of urea in the continuous operation mode. The enzyme-reactor operated continuously at 35 degrees C for 40 h without significant loss of performance. (c) 2005 Elsevier Ltd. All rights reserved.

The aim of the investigation was to determine influence of L-histidine dietary supplementation (P1 0.0%, P2 0.1%, P3 0.2% and P4 0.3%), hybrid line (Cobb 500 and Hubbard Classic) and gender on meat quality and carnosine concentration in chicken breast and thigh muscles. The research was carried out on 184 one day old broiler chickens as 4x2x2 factorial design. Chicken live weight, carcass weight, dressing percentage, absolute and relative shares of main body parts in the carcass, pHi, pHu, colour, drip loss, cooking loss and share force of breast muscle, and carnosine concentration in breast and thigh muscles were determined. L-histidine dietary supplementation significantly affected live weight, carcass weight, weight of drumsticks and thighs, backs and wings, share of back and the CIE a* value (P

Ozalp, Veli Cengiz/0000-0002-7659-5990 WOS:000324564400001 PubMed: 23959148 A novel core shell beaded chromatographic materials was prepared by grafting of glycidyl methacrylate (GMA) on to the surface of poly(hydoxypropyl methacrylate/ethyleneglycol dimethacrylate), p(HPMA/EGDMA) beads via surface-initiated atom transfer radical polymerization (SI-ATRP). For grafting GMA, p(HPMA/EGDMA) beads were first modified with an ATRP initiator. A reaction with 2-bromo-2-methylpropionyl bromide of the hydroxyl groups of the beads led to ATRP initiator-covered surfaces. The grafted p(GMA) fibrous chains on the beads were decorated with two different ligands (i.e., Protein L and L-histidine) for separation of Immunoglobulin's (Igs) from aqueous solution in batch system. The maximum Igs adsorptions on the p(HPMA/EGDMA)-g-p(GMA)-Protein L and p(HPMA/EGDMA)-g-p(GMA)-L-histidine affinity beads were found to be 81.8 and 112.3 mg/g at pH 7.5 and 5.5, respectively. The purity of Igs from human serum was analyzed by HPLC. The Protein L immobilized affinity beads provided purity about 98%. The novel core shell polymeric beads decorated with Protein L showed a good selectivity for Igs molecules from diluted human serum. Adsorption studies of Igs onto Protein L and L-histidine immobilized affinity beads were also carried out in a continuous system. (C) 2013 Elsevier B.V. All rights reserved.

The reactions of ruthenium(II)-arene complex [Ru-II(eta(6)-p-cym)(pydc)Cl] (where p-cym = p-isopropyl toluene, pydc = 2,3-pyridinedicarboxylato) with biologically nitrogen-donor nucleophiles, such as guanosine-5'-monophosphate (5'-GMP), guanosine (Guo) and L-histidine (L-His) were studied by UV-Vis spectrophotometry and H-1 NMR spectroscopy. The reactions were studied at pH 2.5 and at 7.2. All reactions were followed under pseudo-first order conditions with large excess of the nucleophiles. The selected nucleophiles have a high affinity for Ru(II)-arene complex. The reactivity of the used ligands follow the same order at both pH values: Guo gt 5'-GMP gt L-His, while the reactions at pH 7.2 are always faster. The negative entropies of activation (Delta S-not equal) support an associative mode of activation. However, the rate constants obtained by H-1 NMR at 295 K in D2O follow the same order of the ligand reactivity. The hydrolysis of the [Ru-II(eta(6)-p-cym)(pydc)Cl] complex was very fast and completed by the time the first spectrum was measured. Addition of excess of NaCl to equilibrium solutions reversed the hydrolysis. (C) 2011 Elsevier Ltd. All rights reserved.

Copper toxicity is a critical issue in the development of copper-based catalysts for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions for applications in living systems. The effects and related toxicity of copper on mammalian cells are dependent on the ligand environment. Copper complexes can be highly toxic, can induce changes in cellular metabolism, and can be rapidly taken up by cells, all of which can affect their ability to function as catalysts for CuAAC in living systems. Herein, we have evaluated the effects of a number of copper complexes that are typically used to catalyze CuAAC reactions on four human cell lines by measuring mitochondrial activity based on the metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to study toxicity, inductively coupled plasma mass spectrometry to study cellular uptake, and coherent anti-Stokes Raman scattering (CARS) microscopy to study effects on lipid metabolism. We find that ligand environment around copper influences all three parameters. Interestingly, for the Cu(II)-bis-l-histidine complex (Cu(his) 2), cellular uptake and metabolic changes are observed with no toxicity after 72 h at micromolar concentrations. Furthermore, we show that under conditions where other copper complexes kill human hepatoma cells, Cu(I)-l-histidine is an effective catalyst for CuAAC labeling of live cells following metabolic incorporation of an alkyne-labeled sugar (Ac 4ManNAl) into glycosylated proteins expressed on the cell surface. This result suggests that Cu(his) 2 or derivatives thereof have potential for in vivo applications where toxicity as well as catalytic activity are critical factors for successful bioconjugation reactions. © 2011 American Chemical Society.

Bacterial strains (120) were isolated from fresh, spoiled, VP-packed and MAP-packed herring. Identified bacterial strains were investigated for their abilities to produce biogenic amines in histidine, lysine and ornithine decarboxylase broth by a rapid high-performance liquid chromatography (HPLC) method. The microflora of fresh herring was dominantly Pseudomonas (30%), Enterobacteriaceae (23.2%), Vibrio (13.3%) and Moraxella (13.3%) but, the microflora of herring stored in VP and MAP was dominated by species belonging to Vibrio (23.3%) and Moraxella (20%), which indicates that these packaging systems prevented the growth of Pseudomonas and Enterobacteriaceae. In a laboratory medium containing amino acid (histidine, ornithine and lysine), most of bacterial strains produced histamine, putrescine and cadaverine. The highest histidine decarboxylase activities were observed in Klebsiella oxytoca, Hafnia alvei and Proteus vulgaris which produced 396, 232 and 54 mg histamine/L, respectively in histidine-enriched broth. The accumulation of cadaverine by Klebsiella oxytoca and Hafnia alvei was 325 and 208 mg/l, respectively. All strains isolated produced putrescine in an ornithine-enriched broth, ranging from 3 to 249 mg/l. The production of putrescine by Klebsiella oxytoca and Hafnia alvei was 249 and 195 mg/l, respectively. Moraxella spp and Acinetobacter spp did not produce histamine which indicates they did not have histidine decarboxylase activity. © Springer-Verlag 2005.

The killing of Escherichia coli cells by H2O2 is higher when exposure to the oxidant is performed in a complete culture medium, as compared to saline. Whereas MgSO4, CaCl2, thiamine or glucose, added separately or in combination with the saline, had no effect on the cytotoxic response to H2O2, the cytotoxicity appeared highly dependent upon the presence of the casamino acids in the incubation medium. One of these amino acids, histidine, was found to greatly augment the toxicity of H2O2 in E. coli. This effect of histidine was also observed in mammalian cells. In fact, both the cytoxicity and the DNA damage produced by H2O2 in Chinese hamster ovary (CHO) cells were significantly increased by this amino acid.

Results presented in this study demonstrate an association between the L-Histidine-mediated enhancement of H 2 O 2 -induced cytotoxicity and the formation of DNA double strand breakage (DSB), whereas no relationship exists between the increased cytotoxic response and DNA single strand breakage (SSB). Indeed, the higher lethality and the production of DNA DSB occurred in oxidatively-injured cells regardless of whether the exposure to L-Histidine was performed before or during challenge with the oxidant. In fact, the increased level of DNA SSB detected in cells simultaneously exposed to the oxidant and the amino acid was not observed in cells pre-treated with L-Histidine and then challenged with hydrogen peroxide. Further experiments have demonstrated an association between the kinetics of DNA DSB formation and the enhancement of the cytotoxic response. In conclusion, intracellular L-Histidine seems to mediate the formation of DNA DSB and the increased growth-inhibitory response elicited by the oxidant. In addition, these results suggest that the enhancement of DNA SSB is produced by the extracellular/plasma membrane fraction of the amino acid and not causally related to the L-Histidine-mediated increase of the growth-inhibitory response to H 2 O 2 -treated cells.

Micromolar concentrations of l -histidine increase the cytotoxicity of hydrogen peroxide in a number of cell lines including CHO(hamster), EAHY, McCoy's, U937 and CCRF-CEM (human), Vero (monkey) and SC-1 (mouse). Importantly, these cell lines displayed differentt degrees of sensitivity to H2O2 alone and the extent of enhancement elicited by the amino acid was more pronounced in resistant cell lines. The increased cytotoxicity was invariably associated with the formation of DNA DSBs and a remarkable correlation was found by plotting the level of DNA DSBs against the cytotoxic response. These results strongly support the hypothesis that the mechanism whereby l -histidine increases the toxicity elicited by H2O2 involves the formation of DNA DSBs and are consistent with the possibility that the amino acid might participate in the regulation of the physio-pathological response to oxidative stress in mammals.

Results presented in this study demonstrate that L-glutamine, a competitive inhibitor of L-histidine uptake, inhibits in a concentration-dependent fashion the L-histidine-mediated enhancement of H2O2-induced cytotoxicity. L-Glutamine also prevents the induction of DNA double strand breaks (DSB) but does not affect the enhancing effect of L-histidine on DNA single strand break induction by H2O2. Taken together, these data demonstrate that L-histidine, in order to allow the formation of DNA double strand breakage and increase the toxicity elicited by the oxidant, has to enter the cell. In addition, these results indicate that the enhancement of DNA single strand breakage is a consequence of the action of the amino acid at the extracellular level and/or outer surface of the plasma membrane and does not appear related to the mechanism whereby L-histidine increases the cytotoxic response to H2O2. The latter mechanism very likely involves the formation of DNA DSB.

Mediators of cholera toxin (CT)-induced fluid secretion include 3',5'-adenosine monophosphate (cAMP), prostaglandin E(2) (PGE(2)), and 5-hydroxytryptamine (5-HT). Administration of L-histidine significantly reduced the net secretory response of the small intestine of mice challenged with CT and reduced the capacity of PGE(2) to stimulate Na+ transport in Ussing chambers. We demonstrated that L-histidine chemically modified the structure of PGE(2) but had no direct effect on cAMP or 5-HT. L-Histidine and imidazole reacted with PGE(2) in vitro in cell-free mixtures incubated at 37 degrees C and pH 7.0 under an atmosphere of N(2) with the formation of PGE(2)-imidazole and PGE(2)-histidine covalent adducts. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) analysis of the purified adduct showed that imidazole catalyzed the dehydration of PGE(2). A Michael adduct then was formed between C11 of 11-deoxy-Delta(10) PGE(2) (PGA(2)) and the tau nitrogen in the imidazole ring of L-histidine. Importantly, the isolated PGE(2)-imidazole and PGE(2)-histidine adducts inhibited CT-induced fluid loss and cAMP accumulation in mouse intestinal loops. The protection provided by PGE(2)-imidazole, PGE(2)-histidine, and L-histidine against intestinal fluid loss could provide a basis for future therapy against cholera.