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Though significant advances are made in the arena of single-cell electroanalysis, quantification of intracellular amino acids of human cells remains unsolved. Exemplified by l-histidine (l-His), this issue is addressed by a practical electrochemical nanotool synergizing the highly accessible nanopipette with commercially available synthetic DNAzyme. The fabricated nanotools are screened before operation of a single-use manner, and the l-His-provoked cleavage of the DNA molecules can be sensibly transduced by the ionic current rectification response, the intrinsic property of nanopipette governed by its interior surface charges. Regional distribution of cytosolic l-His level in human cells is electrochemically quantified for the first time, and time-dependent drug treatment effects are further revealed. This work unveils the possibility of electrochemistry for quantification of cytosolic amino acids of a spatial- and time-based manner and ultimately enables a better understanding of amino acid-involved events in living cells., (© 2021 Wiley-VCH GmbH.)

Perovskite solar cells have been proven to enhance cell characteristics by introducing passivation materials that suppress defect formation. Defect states between the electron transport layer and the absorption layer reduce electron extraction and carrier transport capabilities, leading to a significant decline in device performance and stability, as well as an increased probability of non-radiative recombination. This study proposes the use of an amino acid (L-Histidine) self-assembled monolayer material between the transport layer and the perovskite absorption layer. Surface analysis revealed that the introduction of L-Histidine improved both the uniformity and roughness of the perovskite film surface. X-ray photoelectron spectroscopic analysis showed a reduction in oxygen vacancies in the lattice and an increase in Ti4+, indicating that L-Histidine successfully passivated trap states at the perovskite and TiO2 electron transport layer interface. In terms of device performance, the introduction of L-Histidine significantly improved the fill factor (FF) because the reduction in interface defects could suppress charge accumulation and reduce device hysteresis. The FF of large-area solar modules (25 cm2) with L-Histidine increased from 55% to 73%, and the power conversion efficiency (PCE) reached 16.5%. After 500 h of aging tests, the PCE still maintained 91% of its original efficiency. This study demonstrates the significant impact of L-Histidine on transport properties and showcases its potential for application in the development of large-area perovskite module processes. [ABSTRACT FROM AUTHOR]

The amino acid L-histidine, which has an imidazole ring, was investigated as a corrosion inhibitor for AISI 1018 carbon steel in chloride solution based on the effectiveness of inhibitors containing imidazole in their composition. A neutral environment was chosen for this study due to the scarcity of research on this amino acid in this environment type. Concentrations of 250, 500, and 1000 ppm were evaluated. Various methods were used to determine inhibition effectiveness, including mass loss, open circuit potential, linear potentiodynamic polarization, and electrochemical impedance spectroscopy. For mass loss, the inhibition efficiency varied from 83 to 88% according to the increase in concentration. For the electrochemical tests, the efficiency variation ranged from 62 to 90% with increasing amino acid concentration. Furthermore, a simulation analysis using quantum chemical calculations within the scope of Density Functional Theory (DFT) revealed that histidine's nucleophilic character is crucial for its corrosion inhibitory capacity in an aqueous medium at pH 7. The inhibition efficiency increased with increasing concentration in a neutral medium, following the Langmuir isotherm for the adsorption of L-histidine. Additional studies were carried out using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA). Analysis of the substrate surface by scanning electron microscopy (SEM) showed greater preservation with the addition of L-histidine, confirming its adsorption on the steel. Atomic Force Microscopy (AFM) also demonstrated an improvement in surface roughness in the presence of amino acids compared to the medium without an inhibitor. [ABSTRACT FROM AUTHOR]

The analysis of dietary supplements is far less regulated than pharmaceuticals, leading to potential quality issues. Considering their positive effect, many athletes consume supplements containing l-histidine and β-alanine. A new microfluidic method for the determination of l-histidine and β-alanine in dietary supplement formulations has been developed. For the first time, capacitively coupled contactless conductivity detection was employed for the microchip electrophoresis of amino acids in real samples. A linear relationship between detector response and concentration was observed in the range of 10–100 µmol L–1 for l-histidine (R2 = 0.9968) and β-alanine (R2 = 0.9954), while achieved limits of detection (3 × S/N ratio) were 4.2 µmol L–1 and 5.2 µmol L–1, respectively. The accuracy of the method was confirmed using recovery experiments as well as CE-UV-VIS and HPLC-UV-VIS techniques. The developed method allows unambiguous identification of amino acids in native form without chemical derivatization and with the possibility of simultaneous analysis of amino acids with metal cations. [ABSTRACT FROM AUTHOR]

The amino acid L-histidine, which has an imidazole ring, was investigated as a corrosion inhibitor for AISI 1018 carbon steel in chloride solution based on the effectiveness of inhibitors containing imidazole in their composition. A neutral environment was chosen for this study due to the scarcity of research on this amino acid in this environment type. Concentrations of 250, 500, and 1000 ppm were evaluated. Various methods were used to determine inhibition effectiveness, including mass loss, open circuit potential, linear potentiodynamic polarization, and electrochemical impedance spectroscopy. For mass loss, the inhibition efficiency varied from 83 to 88% according to the increase in concentration. For the electrochemical tests, the efficiency variation ranged from 62 to 90% with increasing amino acid concentration. Furthermore, a simulation analysis using quantum chemical calculations within the scope of Density Functional Theory (DFT) revealed that histidine’s nucleophilic character is crucial for its corrosion inhibitory capacity in an aqueous medium at pH 7. The inhibition efficiency increased with increasing concentration in a neutral medium, following the Langmuir isotherm for the adsorption of L-histidine. Additional studies were carried out using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA). Analysis of the substrate surface by scanning electron microscopy (SEM) showed greater preservation with the addition of L-histidine, confirming its adsorption on the steel. Atomic Force Microscopy (AFM) also demonstrated an improvement in surface roughness in the presence of amino acids compared to the medium without an inhibitor.

This paper presents the results of a study of the process of stabilization of zinc silicate nanoparticles using the amino acid L-histidine. Zinc acetate was used as a precursor, sodium silicate was used as a precipitant, and the amino acid L -histidine acted as a stabilizer. Synthesis was carried out by chemical precipitation in an aqueous medium. A simultaneous thermal analysis was carried out, as a result of which it was found that the addition of an amino acid to nanosized zinc silicate has a great influence on the crystal structure and thermal transitions for this material. Next, the X-ray phase analysis was carried out, which showed that of zinc silicate particles have an amorphous structure and are in a nanoscale state. At the next stage of the work, the process of interaction of an amino acid with a zinc silicate particle was studied by IR spectroscopy. The results of the study showed that stabilization of particles is accompanied by the formation of a chemical bond between silicon in the zinc silicate molecule and the amino group in the L -histidine molecule.

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The adsorption isotherms of L-histidine on MKN-SWCNT-S1 CNTs from aqueous solution at temperatures of 25, 35, 45, 55, 65 and 80 °C were interpreted within the framework of the single-layer cluster adsorption model. A new approach to determine the equilibrium parameters of the cluster adsorption isotherm equation and sorbate structure on CNTs, as well as a nonlinear modelling method, was applied. To confirm the cluster nature of amino acid adsorption on CNTs, the clustering criterion proposed in the previous work was applied, and the cluster structure was evaluated, which is significant for the application of CNTs in biomedicine. The found equilibrium parameters of adsorption were applied to the determination of thermodynamic characteristics of adsorption (changes in Gibbs energy, enthalpy and entropy) of L-histidine on CNTs and the character of adsorption was analysed. [Display omitted] • The adsorption isotherms of L-histidine on CNTs were interpreted within the framework of the cluster adsorption model. • The cluster character of L-histidine adsorption on CNTs was proved. • The parameters of adsorption isotherms and the structure of histidine clusters on CNTs were determined. • The linearisation method was applied to determine the parameters of adsorption isotherms. • The found isotherms parameters were applied to the determination of thermodynamic characteristics of adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improved mechanistic understanding of the interactions in aqueous protein solutions. • Rapid and resource-efficient identification of potential excipient mixtures by methodical selection. • Correlation between charge & side chain length of the amino acid and the respective influence on the protein stability. • Ratio/molalities of excipients as decisive factor in design of aqueous protein formulations. • Potential of transferability of excipient mixture choice to different proteins. Still today, high-concentration protein formulations are often developed based on high-throughput experimental screening approaches. Although likely delivering working formulations, these approaches do not lead to a deep/mechanistic understanding of the protein phase behavior in solution. Within this work, we thus optimized and enhanced a recent approach for an initial low effort selection of potential excipients and excipient mixtures to be used in high-concentration protein formulations. This approach considers both: molecular interactions and thermodynamic determinants to access the phase behavior of the proteins in solution, as well as pharmaceutical engineering boundaries (such as osmotic pressure and osmolality) to deliver on optimal formulation conditions. Water activity coefficient γ W -calculations (used to describe the protein environment in solution), unfolding temperature (conformational stability) and protein-protein interactions (colloidal stability) are used as determinants. Amino acids (20 proteinogenic amino acids), selected amino acid mixtures, as well as mixtures of amino acids and trehalose (l -arginine-trehalose; l -histidine-trehalose) are considered as model excipients. The approach is extends by studying the long-term stability of the predicted formulation conditions for a γ-globulin from human blood and denosumab. The results reveal, that by combining protein-specific experiments as well as model-based studies for the selection of excipient mixtures in high concentration protein formulations, the effort as well as the resource requirements can be reduced significantly. [ABSTRACT FROM AUTHOR]

As an important amino acid in the body, L-histidine participates in various physiological processes. Therefore, it is of great necessity to establish a rapid and effective method for L-histidine sensing, especially in blood and urine. In this work, a fluorescence sensor for detection of L-histidine was successfully developed using Cu-MOFs/Fe 3 + sensor. Cu-MOFs with blue emission served as the identification unit and signal source, and Fe 3 + played the role of "quencher" in this system. Fe 3 + induced the fluorescence quenching of Cu-MOFs to form Cu-MOFs/Fe 3 + sensor due to the effect of photoinduced electron transfer (PET). After the addition of L-histidine, Fe 3 + was captured by L-histidine to form L-histidine-Fe 3 + complex, which inhibited the PET effect from Cu-MOFs to Fe 3 + , resulting in the fluorescence recovery of Cu-MOFs. With such a design, L-histidine detection was realized with a wide linear range from 1 μ M to 190 μ M. The limit of detection (LOD) was calculated as low as 0.156 μ M. In addition, successful detection of L-histidine in blood serum with high selectivity and sensitivity indicated the real applications and potential diagnostic value of Cu-MOFs/Fe 3 + system. Cu-MOFs were successfully synthesized using hydrothermal method, the CuO was used as metal centers and NH2-BDC was served as stereoscopic ligand. The Cu-MOFs/Fe3+ probe for L-histidine sensing was prepared by mixing Fe3+ with Cu-MOFs in aqueous solution. In this system, Fe3+ acted as a fluorescence "quencher" and reduced the fluorescence of Cu-MOFs via photo-induced electron transfer (PET) between Cu-MOFs and Fe3+. After the addition of L-histidine, the fluorescence of Cu-MOFs recovered due to the strong chelation between Fe3+. [ABSTRACT FROM AUTHOR]

• Turbidity and particle diameter of myosin decreased with Arg/His. • The hydrophobicity of myosin containing Arg/His increased after two-step heating. • Positively charged Arg theoretically was bound to negatively charged myosin. • R-group of Arg/His might interact with unfolding aromatic residue of myosin. • Arg showed a higher ability on suppressing myosin aggregation than that of His. This research focused on the effects of l -arginine (l -Arg) and l -histidine (l -His) on the heat-induced aggregation of fish myosin. l -Arg/ l -His increased the pH of the myosin solution from 6.82 to 8.74 and 7.24, respectively, and decreased the turbidity, aggregate size, shear modulus, and breaking force. The incorporation of l -Arg/ l -His decreased the surface hydrophobicity during setting, but increased it during the two-step heating. The heat-induced aggregation of myosin was suppressed by both amino acids, with the inhibitory effect being greater for l -Arg than l -His. On one hand, the change in the pH played a critical role in suppressing the heat-induced aggregation of myosin. On the other hand, the characteristics of l -Arg/ l -His themselves, such as net charges and particular R-groups, were another main contributor to aggregation suppression. Particularly, l -Arg/ l -His could interact with exposed aromatic residues of myosin, and the interactions may dominate and overwhelm the burial of aromatic residues during two-step heating. [ABSTRACT FROM AUTHOR]

In this study, the influence of Na content of dry-cured beef by partial replacement with KCl, L-lysine, and L-histidine was investigated during processing. Dry-cured beef aged over 57 days, compared to control groups (100% NaCl), salt substituted groups (SS, 39.7% of NaCl, 51.3% of KCl and a blend of 7% L-lysine and 2% L-histidine); had a significant impact on the proteolysis index and total free amino acids, lower activities, and gene levels of cathepsin B and L, as well as reduced contents of protein carbonyls and thiol group. The present study provides a successful strategy for improvement of the perceived saltiness and inhibition of the bitterness, while exhibiting no significant negative effects on color or textural properties. [ABSTRACT FROM AUTHOR]

The aim of this research was to investigate the deposition of carnosine in broiler muscles by feeding treatments comprising ß-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% ß-alanine + 0.24% MgO; P3, 0.25% L-histidine + 0.24% MgO; and P4, 0.20% ß-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<0.05), as well as on the carcass quality at slaughter (P<0.05; except the portion of wings), pH1 value (P=0.035), CIE a* indicator (P=0.007), drip loss (P= 0.002), and meat texture (P=0.008). Compared to the control group, synthesis and deposition of carnosine were increased in breast muscles in groups P2, P3, and P4 by 7.51%, 10.62%, and 62.93%, respectively, and in thigh muscles by 61.05%, 78.95%, and 89.52%, respectively. It was also confirmed that feeding treatments influenced the level of TBARS in frozen broiler breast muscles (P=0.014). [ABSTRACT FROM AUTHOR]

This work investigated the effect of treatment of soy protein isolate (SPI) with basic amino acids (BAA) (l -Arginine, l -Histidine, and l -Lysine) at different concentrations prior to spray drying on the beany-flavor and functional properties. The results illustrated that the BAA prominently improved the solubility and emulsifying properties of SPI, and reduced the its release of beany-flavor compounds. Additionally, l -Arginine was more effective in increasing the solubility and emulsifying properties of the SPI than l -Histidine and l -Lysine. Notably, 0.3% l -Arginine improved the solubility, emulsifying activity index, emulsifying stability index of the SPI by 43.5%, 64.2% and 45.3% respectively. Through the headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), the 0.3% BAA showed the better mitigation effect on the beany flavor of SPI among three addition concentrations. The increased ζ-potential showed that BAA enhanced the electrostatic repulsion of the SPI, facilitating its dissolution and formation of a more stable emulsion system. Surface hydrophobicity and fluorescence spectral results revealed that BAA enhance the exposure of hydrophobic groups, enhancing the stability of oil-water interface and promoting the interaction between beany-flavor compounds and SPI. These findings lay the theoretical groundwork for further research and application of soy protein. [Display omitted] • Basic amino acids (BAA) increased the solubility of soy protein isolate (SPI). • BAA enhanced the emulsion activity/stability index of SPI. • BAA diminished the release intensity of beany flavor from SPI. • BAA improved the absolute value of potential and surface hydrophobicity of SPI. • BAA reduced the free sulfhydryl groups of SPI. [ABSTRACT FROM AUTHOR]

Four mixed salts of amino acid L-histidine comprising hexafluorosilicate anion have been obtained in form of single crystals. These mixed salts are: orthorhombic 2L-His2+⋅2ClO4-⋅SiF62-⋅2H2O (space group P21212, Z=2, a=10.1549(8) Å, b=14.847(1) Å, c=8.7536(7) Å, which is isostructural with recently published 2L-His2+⋅2BF4-⋅SiF62-⋅2H2O), monoclinic 2L-His2+⋅2Cl-⋅SiF62- (space group C2, Z=2, a=27.037(2) Å, b=6.9849(5) Å, c=5.3630(4) Å, β=91.928(4)°) and isostructural 2L-His2+⋅2Br-⋅SiF62- (space group C2, Z=2, a=27.063(6) Å, b=7.1013(17) Å, c=5.5076(11) Å, β=92.141(11)°), and triclinic 2L-His2+⋅SO42-⋅SiF62-⋅3H2O (space group P1, Z=1, a=8.5005(17) Å, b=8.7896(18) Å, c=9.7286(19) Å, α=71.49(3)°, β=92.141(11)°, γ=86.17(3)°). [ABSTRACT FROM AUTHOR]

The title reactions have been studied spectrophotometrically. A two step consecutive mechanism for the amino acids was found which differs from that of the dipeptides, which follow two parallel paths under identical reaction conditions. In the case of amino acids the first step is ligand dependent, but the second step is a ligand independent chelation step, whereas for dipeptides two parallel ligand dependent paths are observed. A comparison between these closely related systems and the unique findings in their mechanistic behavior is discussed in detail. [ABSTRACT FROM AUTHOR]

Density and viscosity experimental data for l-histidine in NaCl aqueous solutions were obtained at different salt and different amino acid concentrations in the range of temperatures between 293.15 and 323.15 K. The results have been correlated and analyzed in order to evaluate the influence of electrolyte concentration and temperature on the volumetric and viscometric properties of the solutions. The apparent molar volumes and the transfer volumes of l-histidine in aqueous NaCl solutions at different salt and amino acid molalities over entire temperature range were calculated from experimental density data. The viscosity experimental data have been analyzed with Jones–Dole equation and the Falkenhagen ( A) and the Jones–Dole coefficient ( B) have been calculated in order to evaluate the interactions occurring in the systems. The B viscosity coefficients were found to be positive for all conditions, showing a kosmotropic effect of solutes, indicating an alignment of zwitterions with ions/water dipoles. A comparison of standard partial molar volumes for some amino acids in water and NaCl aqueous solutions shows that they increase with molecular mass and complexity of the lateral side chain of the amino acid. [ABSTRACT FROM AUTHOR]

l-Histidine chemo- and regioselectively reacts with tertiary cyanopropargylic alcohols (4,4-di-alkyl-4-hydroxybut-2-ynenitriles) under mild conditions (water, 6.4 wt.% NaOH, 5-15 °C, 72-175 h) with the formation of new 'unnatural' amino acids containing an iminodihydrofuran substituent in the amino group (50-70% yields). [ABSTRACT FROM AUTHOR]

The adsorption of amino acids such as l-phenylalanine and l-histidine was carried out on a series of mesoporous carbons obtained with the use ordered silicas KIT-6, SBA-16, SBA-15 as templates and furfuryl alcohol as carbon precursor. Small angle XRD analysis confirmed the ordered mesoporous structures of all materials obtained. They were also characterised by well-developed surface areas and high pore volumes. Adsorption behaviour of amino acids on ordered mesoporous carbons was investigated in potassium phosphate buffer solutions with adjustable l-phenylalanine and l-histidine concentration, ion strength, and pH. The highest sorption capacity towards the amino acids were observed at pH close to the isoelectric point of l-phenylalanine (pI = 5.48) and l-histidine (pI = 7.59). Electrostatic, hydrophobic and steric interactions had very strong effect on the adsorption of amino acids on mesoporous carbons. The amount of l-phenylalanine and l-histidine adsorbed decreased in the following sequence: C > C > C that was strongly related to their structure, surface areas and average pore diameters. [ABSTRACT FROM AUTHOR]

The corrosion inhibition behavior of nitrogen-containing amino acid l-Histidine (LHS) on mild steel in 0.1 M HSO solution in the temperature range of 30-60 °C was studied by weight loss measurements, and potentiodynamic polarization measurements. The effect of the addition of very small concentration of surfactants, sodium dodecyl sulfate (SDS), and cetyltrimethyl ammonium bromide (CTAB), respectively on the corrosion inhibition behavior of LHS was also studied. The surface morphology of the corroded steel samples was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). LHS significantly reduces the corrosion rates of mild steel, with the maximum inhibition efficiency (IE) being 71.09% at 30 °C in the presence of 500 ppm of LHS. The IE of LHS is synergistically increased in the presence of SDS and CTAB. The SEM and AFM photographs show a clearly different surface morphology in the presence of additives. LHS alone and in combination with surfactants obeys Langmuir adsorption isotherm from the fit of the experimental data of all concentration and temperature studied. The calculated thermodynamic parameters for adsorption reveal strong interaction between the inhibitors and the mild steel surface, and suggest physical adsorption. The results obtained by potentiodynamic polarization measurements are consistent with the results of the weight loss measurement. LHS acts more anodic than cathodic inhibitor. [ABSTRACT FROM AUTHOR]

Abstract: Four different mononuclear octahedral Ni(II) complexes with protonated and deprotonated form of the same ligand have been synthesized by controlling reaction conditions and structurally characterized. The complexes are [Ni(HL l-his)(benzoate)(MeOH)] (1), [Ni(HL l-his)(SCN)(MeOH)] (2), [Ni(HL l-his)2] (3) and [Ni(L l-his)(imidazole)2] (4) where H2L l-his is (S)-2-(2-hydroxybenzylamino)-3-(1H-imidazol-4-yl)-propionic acid. The ligand behaves as a monobasic tetradentate ligand in 1 and 2, monobasic tridentate ligand in 3 and dibasic tetradentate ligand in 4. Ni(II) coordinated phenolic proton of the ligand in the complexes 1–2 shows strong intra-molecular H-bonding with benzoate in 1 and lattice water in 2, whereas 3 shows intermolecular H-bonding between uncoordinated phenols with neighbouring carboxylate. The pH titration of the complexes revealed that metal coordination and H-bond in complexes 1 and 2 considerably lowers the acidity of ligand phenol (pKa 6.8 and 7.0 respectively) compared to phenol (pKa 10). The complex 4 does not show any proton loss due to the absence of phenolic proton. All the complexes show extensive H-bonded network in the crystals including narrow (7.8×5.2Å) water filled one dimensional channel in 2. [ABSTRACT FROM AUTHOR]

Abstract: l-Histidine capped iron oxide nanoparticles (HCIO) have been synthesized in one pot in the presence of l-histidine. The final product was analyzed for composition, microstructure, ac–dc conductivity performance as well as dielectric permittivity. Results revealed that magnetic nanoparticles are maghemite (or magnetite) and l-histidine is covalently bonded to the nanoparticle surface via carboxyl groups. Thermal analysis revealed that magnetic nanoparticles showed catalytic effect that caused an early degradation/decomposition of the l-histidine capping. Near spherical morphology was assessed by TEM and particle size calculated from TEM analysis and crystallite size calculated from XRD analysis reveal single crystalline nature of iron oxide NPs. Magnetic measurements reveal the superparamagnetic character of the nanoparticles, hence the nanocomposite. The ac conductivity showed a temperature-dependent behavior at low frequencies and temperature independent behavior at high frequencies which is an indication of ionic conductivity. The dc conductivity of the nanocomposites is found to obey the Arrhenius plot with activation energy of 0.934eV. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite. [ABSTRACT FROM AUTHOR]

Abstract: l-Histidine capped single-crystalline gold nanoparticles have been synthesized by a hydrothermal process under a basic condition at temperature between 65 and 150°C. The produced gold nanoparticles were spherical with average diameter of 11.5±2.9nm. The synthesized gold colloidal solution was very stable and can be stored at room temperature for more than 6 months. The color of the colloidal solution can change from wine red to mauve, purple and blue during the acidifying process. This color changing phenomenon is attributed to the aggregation of gold nanoparticles resulted from hydrogen bond formation between the histidines adsorbed on the gold nanoparticles surfaces. This hydrothermal synthetic method is expected to be used for synthesizing some other amino acid functionalized gold nanomaterials. [Copyright &y& Elsevier]

Abstract: The administration of methamphetamine (METH; 10mg/kg, i.p.) to male ICR mice induced bizarre behaviors including persistent locomotion and stereotypical behaviors, which were classified into four categories: stereotypical head-bobbing, circling, sniffing, and biting. Pretreatment with l-histidine (750mg/kg, i.p.) significantly decreased the stereotypical biting induced by METH and significantly increased persistent locomotion. This effect of l-histidine on behavior was completely abolished by simultaneous administration of pyrilamine or ketotifen (brain-penetrating histamine H1 receptor antagonists; 10mg/kg each, i.p.), but not by the administration of fexofenadine (a non-sedating histamine H1 receptor antagonist that does not cross the blood-brain barrier; 20mg/kg), zolantidine (a brain-penetrating histamine H2 receptor antagonist; 10mg/kg), thioperamide, or clobenpropit (brain-penetrating histamine H3 receptor antagonists; 10mg/kg each). The histamine content of the hypothalamus was significantly increased by l-histidine treatment. These data suggest that l-histidine modifies the effects of METH through central histamine H1 receptors. [Copyright &y& Elsevier]

Abstract: A new zwitterionic (‘gemini’ like) l-histidine imprinted polymer, based on poly (ethylenediamine tetraacetic acid-co-chloranil), was synthesized for the modification of hanging mercury drop electrode. The imprinted polymeric film at the electrode surface facilitated l-histidine to be reduced electrochemically, as a consequence of the catalytic action of charge-transfer (chloranil-l-histidine complexation) reaction, to respond the corresponding differential pulse, cathodic stripping voltammetric signal without any cross-reactivity with interferents. The limit of detection (3σ) was found to be 0.128 ng mL−1 (RSD 0.2%) and results were found to be precise and accurate, without any false-positive contributions from human blood serum samples. [Copyright &y& Elsevier]

The intestine of the American lobster, Homarus americanus, was isolated and perfused in vitro with a physiological saline, based on the ion composition of the blood, to characterize the mechanisms responsible for transmural transport of zinc and how the amino acid, l-histidine, affects the net movement of the metal across the tissue. Previous studies with this preparation, focusing on the characteristics of unidirectional mucosa to serosa (M to S) fluxes of 65Zn2+ and 3H- l-histidine, indicated the presence of a brush border co-transport process responsible for simultaneously transferring the metal and amino acid across this tissue as an apparent bis-complex (Zn-[His]2) using a PEPT-1-like dipeptide carrier mechanism. In addition, both zinc and l-histidine were also transferred toward the blood by separate transporters that were independent of the other substrate. The focus of the present study was to characterize the serosa to mucosa (S to M) flux of 65Zn2+ under a variety of conditions, and use these values in conjunction with those from the previous study, to assess the direction and magnitude of net metal movement across the tissue. Transmural S to M transport of 65Zn2+ was markedly reduced with the addition of the serosal inhibitors ouabain (32%), excess K+ (25%), excess Ca2+ (30%), Cu2+ (38%), nifedipine (21%), and vanadate (53%). In contrast, this flux was markedly stimulated with the serosal addition of ATP (24%) and excess Na+ (28%). These results suggest that S to M fluxes of zinc occurred by the combination of the basolateral Na/Ca exchanger (NCX), where zinc replaced calcium, and a basolateral nifedipine-sensitive calcium channel. Transmural M to S 65Zn2+ fluxes (5–100 μM) were threefold greater than S to M metal transport, and the addition of luminal l-histidine doubled the net M to S zinc flux over its rate in the absence of the amino acid. The results of this paper and those in its predecessor indicate that zinc transport by the lobster intestine is absorptive and significantly enhanced by luminal amino acids. [ABSTRACT FROM AUTHOR]

Abstract: The X-ray crystallographic structure for the adduct of an activator with human carbonic anhydrase isozyme I (hCA I) is reported. l-Histidine binds deep within the enzyme active site, participating in a network of hydrogen bonds involving its carboxylate moiety and the zinc-bound water molecule, as well as the imidazole of His200, being in van der Waals contacts with Thr199, His200, His64, and His67. This binding is very different from that to the other major cytosolic isozyme hCA II. [Copyright &y& Elsevier]

Abstract: Cu(amino acid) complexes were immobilised on silica gel by covalent anchoring. The amino acids were l-histidine and l-tyrosine and their BOC—(tert-butoxycarbonyl) or methyl ester protected derivatives. To gain control over the synthesis the appropriately protected amino acid was reacted with chloropropylated silica gel first. This modified material as is, or after deprotecting the anchored amino acids, was used in further steps of building the immobilised Cu(II) complex. The covalently grafted complexes were studied by FT-IR spectroscopy and computer modelling. Materials containing protected histidine ligands showed catalase activity (decomposition of H2O2), those containing protected or unprotected tyrosine ligands displayed tyrosinase activity (the decomposed H2O2 oxidised the tyrosine skeleton to a quinoidal structure). [Copyright &y& Elsevier]

Integumentary uptake of [3H]-l-histidine by Nereis succinea was measured in the presence and absence of selected heavy metals and the amino acid l-leucine in 60% artificial seawater (ASW). The time course of 10 μM [3H]-l-histidine uptake into worms over a 60 min incubation was approximately doubled in the presence of 0.5 μM zinc and when calcium in the incubation medium was reduced from 6 mM to 5 μM the stimulatory effect of zinc on amino acid accumulation was reduced and uptake under the latter conditions was approximately half that of the control. Zinc stimulation of [3H]-l-histidine influx was a hyperbolic function of zinc concentration over the range 0 to 50 μM metal and displayed an apparent activation or affinity constant of 385±127 nM Zn2+. The hyperbolic stimulatory effect of 1 μM Zn2+ on the time course of 10 μM [3H]-l-histidine uptake was abolished in the presence of 25 μM l-leucine, suggesting that this amino acid shared the same transport system as [3H]-l-histidine and acted as a potential competitive inhibitor. Influx of [3H]-l-histidine was a hyperbolic function of external amino acid concentration and displayed an apparent affinity constant (Km) of 23.71±5.02 μM and an apparent maximal velocity (Jmax) of 4701±449 pmol/g dry wt.×15 min. Addition of 0.5 μM zinc resulted in a four-fold increase in Jmax and a doubling of Km, suggesting the effect of the metal was mostly on the rate of amino acid transport. [3H]-l-histidine influx was mildly stimulated by Fe2+ (0.5 μM), but was unaffected by either Ag+ or Al3+ (both at 0.5 μM). These results suggest that [3H]-l-histidine uptake into worm integument may take place by the classical Na+-independent l-transport system shared by l-leucine and regulated by exogenous calcium and other divalent metal concentrations. [Copyright &y& Elsevier]

The effect of 21 amino acids on the feeding response of larvae of Spodoptera littoralis was investigated using the 'Styropor method.' Lamellae of Styropor were treated (a) with different concentrations of amino acids, (b) different concentrations of amino acids mixed with 0.125 M sucrose, and (c) 0.125 M sucrose alone. The weight of Styropor consumed during 48 h served as the criterion of phagostimulation or phagodeterrency. With the sole exception of 0.125 M L-glutamic acid, no phagostimulation occurred in any of the amino acids tested in mixture with 0.125 M sucrose; none was phagostimulant when tested alone. Deterrency was found at 0.125 M in L-alanine, DL-alpha-amino- n-butyric acid, L-serine, L-cystine, L-methionine, L-tyrosine, and L-histidine, when mixed with an equimolar concentration of sucrose. Methionine was highly phagodeterrent also at 0.0625 M and, as was DL-alpha-amino-n-butyric acid, still active even at 0.0125 M. Chemical analysis showed that there was no decomposition of methionine applied on Styropor. [ABSTRACT FROM AUTHOR]

Relative densities, $$\left( {\rho - \rho _o } \right)$$ , and heat capacity ratios, $$[(c_p \rho /c_{p1}^o \rho _o ) - 1],$$ of aqueous L-histidine, L-phenylalanine, L-tyrosine, L-tryptophan, and L-2,3-dihydroxyphenylalanine (L-dopa) have been measured at 15, 25, 40, and 55°C and 0.1 MPa. Apparent molar volumes, V2,Φ, apparent molar heat capacities, CP2,Φ, partial molar volumes at infinite dilution, $$V_2^o$$ , and partial molar heat capacities at infinite dilution, $$V_{p2}^o$$ , have been calculated from these measurements and compared to available literature values. The partial molar properties at infinite dilution for these systems have been added to those previously obtained for amino acids and peptides in water and the combined set used as input to a novel additivity analysis. The model we develop is based upon the equations of state of Helgeson, Kirkham, and Flowers (HKF) and has been constructed with additive parameters. The model may be used to predict thermodynamic properties of many aqueous biochemicals over an extended temperature range. Group contributions to the parameters in our model and effective Born coefficients are reported for 24 aqueous amino acid and peptide systems. Our results are compared to data previously published in the literature. [ABSTRACT FROM AUTHOR]

The changes in hydration structure of β-alanine and L-histidine through dipeptide formation were studied and discussed from experimentally measured values of densities, viscosities and computational investigations of amino acids diluted aqueous solutions, β-alanine and L-histidine, and the final dipeptide, L-carnosine over the temperature range from 283.15 K to 313.15 K. The apparent molar volume (V ϕ), apparent molar volume at infinite dilution (V ϕ o ), Masson 's experimental slope (S v), limiting apparent molar expansibility, (E ϕ o), Hepler 's coefficient, hydration number, and viscosity B coefficient have been evaluated using the experimental density and viscosity values. The formation of the peptide bond has been examined in terms of water structuring nature around dipeptide and starting amino acids, and how it is linked with dipeptide self-interactions. Also, L-carnosine solubility in water was determined, as well as the thermal decomposition of the investigated compounds was examined by simultaneous thermogravimetric (TG) and DSC measurement. For the evaluation of their decomposition, the data obtained by coupled TG–mass spectrometric (MS) measurements were used. • L-carnosine solubility in water was determined. • TG-MS analysis showed almost the same main decomposition products and ion fragment distribution of three examined compounds. • L-carnosine have the more pronounced structure making comparing to L-histidine and β-alanine. • The entropy increase of L-carnosine due to dipeptide self-interaction and release of electrostricted water. [ABSTRACT FROM AUTHOR]

Abstract: Divalent transition metal ions have a strong relationship with l-histidine (His) in many important biological processes. In this work, the solution complexes of His and Mn2+, Co2+, Ni2+, Cu2+, Zn2+ with a molar ratio 2:1 separately at pH 6.0 were studied by extended X-ray absorption fine structure (EXAFS). The result supports that all the Metal/His complexes have distorted octahedral geometries, but the configurations of Cu/His and Zn/His are more disordered than that of Mn/His, Co/His and Ni/His. Data also indicate that the bond distances between the metals ions and histidine ligands present a clear trend consistent with the rule of the Irving–Williams series. [Copyright &y& Elsevier]

In this study, a novel simple type of label-free, ultra-sensitive, and highly selective UV–Vis absorption and naked-eye detection of histidine (His) and lysine (Lys) using a dye/metal ion ensemble is developed. The outcoming high sensitivity and selectivity for histidine and lysine were attained by changing the metal ions. The indicator is released due to its displacement from the murexide (Mure)/Cu2+ complex by histidine and the change in absorbance may be due to the further complexation of lysine with the additional coordination sites present in the zinc atom of Mure/Zn2+ complex. The label-free chemosensor provided sensitive and selective detection of l -histidine and l -lysine with detection limits of 9.1 and 9.4 nmol L−1, respectively. The protocol especially offers high selectivity for the determination of His and Lys among amino acids found in human urine samples. Furthermore, INHIBIT and NAND molecular logic gates were obtained using chemical inputs and UV–Vis absorbance signal output. Image 1 • A new type of label-free, simple and fast chemosensor for detection of His and Lys. • High sensitivity and selectivity for His & Lys were achieved by changing the metal ions. • This probe enabled detection of His & Lys with LODs 9.1 and 9.4 nmol L−1, respectively. • Selective detection of His&Lys without interference from other AAs is a complex matrix. • This receptor demonstrates the functions of multiple logic gates. [ABSTRACT FROM AUTHOR]