Presence Of L-histidine Research Articles

Evaluation of relative efficiency of PDT photosensitizers in producing hydroxyl radicals and singlet oxygen in aqueous media using a UV-visible spectroscopy pNDA dosage.

In order to improve the performance of PDT, it is important to develop new photosensitizers that induce the formation of both hydroxyl radicals and singlet oxygen. In this work, we developed and validated the experimental conditions and reproducibility for the evaluation of relative efficiency of hydroxyl radicals and singlet oxygen production by studying the bleaching of p-nitrosoaniline (pNDA) using a continuous flow UV-visible spectroscopy method in presence of photosensitizers in PBS media. Rapid data sampling made possible to analyze the kinetics of the bleaching by using a mathematical modeling. The pNDA dosage is specific of hydroxyl radicals' production without l-histidine and of singlet oxygen production in presence of l-histidine. A statistical approach is used to precisely evaluate the reliability of the results and to be able to compare different photosensitizers between them such as Methylene Blue and Brillant Blue G.

L-histidine inhibits the heat-induced gelation of actomyosin in a low ionic strength solution.

The heat-induced gelation of actomyosin plays a key role in meat processing. Our previous study showed that L-histidine could affect the characteristics of a heat-induced gel of myosin on a low ionic strength. To apply the specific effect of L-histidine to meat processing, the heat-induced gel properties of actomyosin in the presence of L-histidine were investigated. Actomyosin in a low ionic strength solution containing L-histidine did not form a gel upon heating. The dynamic rheological properties of actomyosin in low ionic strength solutions were distinct depending on the presence or absence of L-histidine. Electron microscopy showed that, heated at 50°C, actomyosin in a low ionic strength solution containing L-histidine remained a filamentous structure. The surface hydrophobicity of actomyosin was stable up to 50°C in a low ionic strength solution containing L-histidine. In conclusion, L-histidine might suppress the aggregation of actomyosin and inhibit heat-induced gelation in a low ionic strength solution.

(Invited) DNA Kirigami with Tripod-C60 Scalpel

A tripod-C60 molecule was synthesized and attached onto a Au-coated AFM tip. Using the tripod skeleton of the molecule, tripod-C60 was immobilized onto the Au surface in a dispersed and stable manner, as observed by XPS and AFM imaging. Using an AFM tip functionalized with the tripod-C60, waffle-type DNA origami was scanned under visible light irradiation. Upon scanning, DNA damage was clearly observed by AFM imaging at the single molecule level. Control experiments in the absence of C60 (tripod only), in the dark, or in the presence of L-histidine or D2O confirmed that the observed DNA damage was induced by singlet oxygen (1O2) generated from C60 under photoirradiation.

Kinetic–spectrophotometric approach to the ampicillin hydrolytic degradation applied for the histidine determination

The objective of this research was to develop a kinetic-spectrophotometric method for the determination of microquantities of L-histidine in pure form and dietary supplements. The method was based on the kinetics of ampicillin degradation by Ni(II) ion as a catalyst in the presence of L-histidine in a strongly alkaline medium. The rate of this reaction was monitored spectrophotometrically by measuring the increase in absorbance at 265 nm as a function of time. The same approach was used for the investigation of the reaction rate in the absence of histidine. A differential variant of the tangent method was used to process the kinetic data. Beer?s law was obeyed in the interval of histidine concentration from 1.24 ?g/ml to 11.63 ?g/ml with the relative standard deviation ranging from 8.1% to 0.7%. The detection limit of 0.46 ?g/ml was estimated based on the 3S0 criterion. The interference effects of some metal ions, anions, and other molecules on the reaction rate were studied to assess method selectivity. Herein described method was applied for the quantification of histidine in dietary supplements. The point hypothesis test confirmed that there was no significant difference between the proposed and the reference method.

Enantioselective Discrimination of Histidine by Means of an Achiral Cubane-Bridged Bis-Porphyrin.

A Langmuir film of cubane-bridged bisporphyrin (H2por-cubane-H2por) at the air/water interface was developed and characterized. The floating film was successfully employed for the chiral discrimination between l- and d-histidine. The enantioselective behavior persisted after the deposition of the film on a solid support using the Langmuir–Schaefer method. Distinct absorption and reflection spectra were observed in the presence of l- or d-histidine, revealing that conformational switching was governed by the interaction between H2por-cubane-H2por and the histidine enantiomer. The mechanism of chiral selection was investigated using an ad hoc modified nulling ellipsometer, indicating the anti-conformation was dominant in the presence of l-histidine, whereas the presence of d-histidine promoted the formation of tweezer conformation.

A microplate screen to estimate metal-binding affinities of metalloproteins

Solute-binding proteins (SBPs) from ATP-binding cassette (ABC) transporters play crucial roles across all forms of life in transporting compounds against chemical gradients. Some SBPs have evolved to scavenge metal substrates from the environment with nanomolar and micromolar affinities (KD). There exist well established techniques like isothermal titration calorimetry for thoroughly studying these metalloprotein interactions with metal ions, but they are low-throughput. For protein libraries comprised of many metalloprotein homologues and mutants, and for collections of buffer conditions and potential ligands, the throughput of these techniques is paramount. In this study, we describe an improved method termed the microITFQ-LTA and validated it using CjNikZ, a well-characterized nickel-specific SBP (Ni-BP) from Campylobacter jejuni. We then demonstrated how the microITFQ-LTA can be designed to screen through a small collection of buffers and ligands to elucidate the binding profile of a putative Ni-BP from Clostridium carboxidivorans that we call CcSBPII. Through this study, we showed CcSBPII can bind to various metal ions with KD ranged over 3 orders of magnitude. In the presence of l-histidine, CcSBPII could bind to Ni2+ over 2000-fold more tightly, which was 11.6-fold tighter than CjNikZ given the same ligand.

N-(2-pyridylmethyl)-L-histidine functionalized Fe3O4 magnetic nanoparticles as an efficient catalyst for synthesis of β-amino ketones

N-(2-Pyridylmethyl)-L-histidine functionalized Fe3O4 magnetic nanoparticles (PMHis@Fe3O4 MNPs) efficiently catalyzed three-component Mannich-type reaction of ketones, aromatic aldehydes and anilines, to synthesize β-amino ketones in good to high yields. Mannich adducts were obtained in moderate to high diastereoselectivity, favoring anti isomer. The imidazole moiety of PMHis residue on catalyst plays an important role in the diastereoselectivity. PMHis@Fe3O4 MNPs were prepared via simple coprecipitation from an aqueous solution of Fe2+ and Fe3+ ions using NH4OH in the presence of L-histidine, followed by reductive amination with 2-pyridine carbaldehyde in the presence of NaBH4. Obtained PMHis@Fe3O4 MNPs were characterized by FT-IR, XRD, VSM, BET, TGA, SEM, EDX and TEM analysis.

Identifying the Nonradical Mechanism in the Peroxymonosulfate Activation Process: Singlet Oxygenation Versus Mediated Electron Transfer.

Select persulfate activation processes were demonstrated to initiate oxidation not reliant on sulfate radicals, although the underlying mechanism has yet to be identified. This study explored singlet oxygenation and mediated electron transfer as plausible nonradical mechanisms for organic degradation by carbon nanotube (CNT)-activated peroxymonosulfate (PMS). The degradation of furfuryl alcohol (FFA) as a singlet oxygen (1O2) indicator and the kinetic retardation of FFA oxidation in the presence of l-histidine and azide as 1O2 quenchers apparently supported a role of 1O2 in the CNT/PMS system. However, the 1O2 scavenging effect was ascribed to a rapid PMS depletion by l-histidine and azide. A comparison of CNT/PMS and photoexcited Rose Bengal (RB) excluded the possibility of singlet oxygenation during heterogeneous persulfate activation. In contrast to the case of excited RB, solvent exchange (H2O to D2O) did not enhance FFA degradation by CNT/PMS and the pH- and substrate-dependent reactivity of CNT/PMS did not reflect the selective nature of 1O2. Alternatively, concomitant PMS reduction and trichlorophenol oxidation were achieved when PMS and trichlorophenol were physically separated in two chambers using a conductive vertically aligned CNT membrane. This result suggested that CNT-mediated electron transfer from organics to persulfate was primarily responsible for the nonradical degradative route.

Synthesis of 3D hierarchical Ag/CuO nanostructures in the presence of l-histidine and their application

We report a facile synthesis of 3D hierarchical Ag/CuO nanostructures via the l-histidine-assisted biomimetic hydrothermal method. The XRD pattern of the 3D hierarchical Ag/CuO prepared in the presence of l-histidine only indicated the peaks belonging to Ag and CuO, and thus confirmed the purity of the nanocomposite. The field emission scanning electron microscopy revealed a large surface area of the 3D hierarchical CuO and Ag nanostructures which confirmed the effect of l-histidine on the morphology of the Ag/CuO. The electrochemical properties of the Ag/CuO nanostructured electrode were investigated by cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy. The modified glassy carbon electrode demonstrated excellent electrochemical activity towards dopamine oxidation compared to the bare GCE. From the DPV results, the estimated limit of detection (S/N = 3) and limit of quantification (S/N = 10) in the linear segment (0.001–80 μM) of dopamine are 0.077 μM and 0.257 μM, respectively. The sensitivity of this linear segment is 4.54 μA μM−1 cm−2.

Effect of the amino acid l-histidine on methane hydrate growth kinetics

In the present study, the effect of a polar amino acid, l-histidine on methane hydrate growth kinetics has been investigated. Methane hydrate formation experiments were carried out in a stirred tank reactor setup at pressure and temperature conditions of 274.15 K and 5.0 MPa respectively. Two different concentrations (0.1 and 1 wt %) of l-histidine were studied. Hydrate growth through molecular dynamic (MD) simulation was also studied; pressure and temperature conditions for the simulations were set at 10.0 MPa and 270.0 K, while the concentration of l-histidine was kept fixed at 0.94 wt %. Hydrate formation runs using MD simulation were carried out with optimal concentration of methane in water. The presence of l-histidine in the system was found to significantly enhance methane hydrate growth kinetics as compared to pure water for both experimental and MD simulation runs. Final gas consumption with 1 wt % l-histidine was found to be comparable to that with 1 wt % SDS, the most commonly used additive for hydrate promotion studies. l-histidine is a benign additive which offers considerable enhancement in methane hydrate formation kinetics and can be utilized for various hydrate based technologies such as methane storage and transport.

Cleaved DNAzyme substrate induced enzymatic cascade for the exponential amplified analysis of l-histidine

A novel strategy of cleaved DNAzyme substrate induced enzymatic cascade has been devised for the exponential amplified detection of l-histidine. The enzyme strand carries out hydrolytic cleavage of the substrate strand in the presence of l-histidine. The cleaved DNAzyme substrates introduce the polymerase/endonuclease reaction cycles as primers. The l-histidine acts as the activator for enzymatic cascade amplification generating a distinguishable fluorescence enhancement. A good nonlinear correlation (R=0.9994) between fluorescence intensity and the logarithm of the l-histidine concentration is obtained over the range from 50nM to 1.0mM. The detection limit was estimated as 30nM. This efficient amplification of the fluorescence signal is attributed to the l-histidine induced cooperation of Klenow Fragment polymerase (exo−) and Nb.BbvCI endonuclease reaction. The activation of such enzymatic cascades through analyte-DNAzyme interactions has a substantial impact on the development of exponential amplified DNAzyme sensors.

Specific chiral sensing of amino acids using induced circularly polarized luminescence of bis(diimine)dicarboxylic acid europium(III) complexes.

The circularly polarized luminescence (CPL) from [Eu(pda)2](-) (pda = 1,10-phenanthroline-2,9-dicarboxylic acid) and [Eu(bda)2](-) (bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) in aqueous solutions containing various amino acids was investigated. The europium(III) complexes exhibited bright-red luminescence assignable to the f-f transition of the Eu(III) ion when irradiated with UV light. Although the luminescence was not circularly polarized in the solid state or in aqueous solutions, in accordance with the achiral crystal structure, the complexes exhibited detectable induced CPL (iCPL) in aqueous solutions containing chiral amino acids. In the presence of L-pyrrolidonecarboxylic acid, both [Eu(pda)2](-) and [Eu(bda)2](-) showed similar iCPL intensity (glum ∼ 0.03 for the (5)D0 → (7)F1 transition at 1 mol·dm(-3) of the amino acid). On the other hand, in the presence of L-histidine or L-arginine, [Eu(pda)2](-) exhibited intense CPL (glum ∼ 0.08 for the (5)D0 → (7)F1 transition at 0.10 mol·dm(-3) of the amino acid), whereas quite weak CPL was observed for [Eu(bda)2](-) under the same conditions (glum < 0.01). On the basis of analysis of the iCPL intensities in the presence of 12 amino acids, [Eu(pda)2](-) was found to be a good chiral CPL probe with high sensitivity (about 10(-2) mol·dm(-3)) and high selectivity for L-histidine at pH 3 and for L-arginine at pH 7. The mechanism of iCPL was evaluated by analysis of the fine structures in the luminescence spectra and the amino acid concentration dependence of glum. For the [Eu(pda)2](-)-histidine/arginine systems, the europium(III) complexes possess coordination structures similar to that in the crystal with slight distortion to form a chiral structure due to specific interaction with two zwitterionic amino acids. This mechanism was in stark contrast to that of the europium(III) complex-pyrrolidonecarboxylic acid system in which one amino acid coordinates to the Eu(III) ion to yield an achiral coordination structure.

Dopamine functionalized–CdTe quantum dots as fluorescence probes for l-histidine detection in biological fluids

In this paper, we developed dopamine functionalized–CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe–dopamine (QDs–DA) could be quenched by Ni2+ due to the strong coordination interaction between the pyrocatechol structure of QDs–DA and Ni2+. In the presence of l-histidine, Ni2+ preferred to bind with l-histidine due to high affinity of Ni2+ to l-histidine and the photoluminescence intensity of QDs–DA was recovered. The recovered photoluminescence intensity of QDs–DA was proportional to the concentration of l-histidine in the ranges of 1.0×10−6–1.0×10−4molL−1 and the detection limit was 5.0×10−7molL−1 respectively. The established method showed a good selectivity for l-histidine among other common amino acids, and it was applied for determination of l-histidine in human serum sample with satisfactory results.

Triamidetriamine Bearing Macrobicyclic and Macrotricyclic Ligands: Potential Applications in the Development of Copper-64 Radiopharmaceuticals

A versatile and straightforward synthetic approach is described for the preparation of triamide bearing analogues of sarcophagine hexaazamacrobicyclic cage ligands without the need for a templating metal ion. Reaction of 1,1,1-tris(aminoethyl)ethane (tame) with 3 equiv of 2-chloroacetyl chloride, yields the tris(α-chloroamide) synthetic intermediate 6, which when treated with either 1,1,1-tris(aminoethyl)ethane or 1,4,7-triazacyclononane furnished two novel triamidetriamine cryptand ligands (7 and 8 respectively). The Co(III) and Cu(II) complexes of cryptand 7 were prepared; however, cryptand 8 could not be metalated. The cryptands and the Co(III) complex 9 have been characterized by elemental analysis, (1)H and (13)C NMR spectroscopy, and X-ray crystallography. These studies confirm that the Co(III) complex 9 adopts an octahedral geometry with three facial deprotonated amido-donors and three facial amine donor groups. The Cu(II) complex 10 was characterized by elemental analysis, single crystal X-ray crystallography, cyclic voltammetry, and UV-visible absorption spectroscopy. In contrast to the Co(III) complex (9), the Cu(II) center adopts a square planar coordination geometry, with two amine and two deprotonated amido donor groups. Compound 10 exhibited a quasi-reversible, one-electron oxidation, which is assigned to the Cu(2+/3+) redox couple. These cryptands represent interesting ligands for radiopharmaceutical applications, and 7 has been labeled with (64)Cu to give (64)Cu-10. This complex showed good stability when subjected to L-cysteine challenge whereas low levels of decomplexation were evident in the presence of L-histidine.

Corrosion resistance of carbon steel in weak acid solutions in the presence of l-histidine as corrosion inhibitor

This paper presents the inhibitory properties of l-histidine on the corrosion of carbon steel in weak acid media containing acetic acid/sodium acetate. The inhibition efficiencies obtained by weight loss measurements are in good agreement with values given by Tafel method and electrochemical impedance spectroscopy. The adsorption of l-histidine obeys the Langmuir isotherm and the negative values of Gibbs energy indicate the nature of interactions between inhibitor molecules and metal surface. Further, the inhibition effect was studied using scanning electron microscopy and energy dispersive X-ray analysis.

Binding of the IclR-type regulator HutR in the histidine utilization (hut) gene cluster of the human pathogen Corynebacterium resistens DSM 45100

The genome of the human pathogen Corynebacterium resistens DSM 45100 is equipped with a histidine utilization (hut) gene cluster encoding a four-step pathway for the catabolism of l-histidine and a transcriptional regulator of the IclR superfamily, now named HutR. The utilization of l-histidine might be relevant for the growth of C.resistens in its natural habitat, probably the histidine-rich inguinal and perineal areas of the human body. The ability of C.resistens to utilize l-histidine as a sole source of nitrogen was demonstrated by growth assays in synthetic minimal media. Reverse transcriptase PCRs revealed enhanced transcript levels of the hut genes in C.resistens cells grown in the presence of l-histidine. Promoter-probe assays showed that the hut genes are organized in three transcription units: hutHUI, hutR, and hutG. The respective transcriptional start sites were mapped by 5' RACE-PCR to detected putative promoter regions. DNA band shift assays with purified HutR protein identified the 14-bp DNA sequence TCTGwwATwCCAGA located upstream of the mapped promoters. This DNA motif includes a 4-bp terminal palindrome, which turned out to be essential for HutR binding in vitro. These data add a new physiological function to the large IclR family of transcriptional regulators.

Selective Transport of Cu2+ Ions through Bulk Liquid Membrane System Mediated by Erythromycin Ethyl Succinate

The carrier mediated transport of Cu2+ ions from an aqueous medium has been examined. The ability of Erythromycin Ethyl Succinate (EES) as a carrier to form a complex with Cu2+ ions and transport them to the receiving phase is reported. The fundamental parameters influencing the transport of Cu2+ ions such as the pH in the source and receiving phases and concentration of the stripping agent in the receiving phase have been optimized and accordingly, the amount of Cu2+ transported across the liquid membrane after 5 h was 94.3 ± 1.8% in the presence of L-histidine as a suitable stripping agent. Moreover, the selectivity and efficiency of Cu2+ ions transport from aqueous solution over other cations in ternary and quaternary mixtures have been investigated. The results indicate that our fabricated membrane is very sensitive toward Cu+2 ions in the presence of heavy metal ions.

Electrochemical real-time detection of l-histidine via self-cleavage of DNAzymes

Herein, a rapid electrochemical biosensor for l-histidine based on highly specific, l-histidine-dependent DNAzymes is described. DNA with a single, sessile ribo-adenine, self-cleaves in the presence of l-histidine, allowing a ferrocene tag to transfer electrons to the electrode. The double-stranded DNA complex was chemi-absorbed to a gold electrode via a 3′ terminal thiol. The signal of this proposed sensor is linear over the range, 1 nM to 10 μM, with R = 0.98775. To improve signal intensity, gold nanoparticles were anchored to a gold electrode surface which had been previously modified with self-assembled monolayers of 1,6-hexanedithiol. With gold nanoparticle modification, a lower detection limit of 0.1 pM l-histidine and a good linear relationship over the range, 0.1 pM to 50 nM were obtained. The proposed biosensor presents high specificity for l-histidine, is not affected by the presence of other amino acids, and demonstrates excellent enantio-selectivity toward l-histidine. This proposed sensor protocol offers reasonable selectivity, rapid speed, and operational convenience for real sample assays.

L-Histidine coated iron oxide nanoparticles: Synthesis, structural and conductivity characterization

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 0.934 eV. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite.

Molecular Identification of Carnosine Synthase as ATP-grasp Domain-containing Protein 1 (ATPGD1)

Carnosine (beta-alanyl-L-histidine) and homocarnosine (gamma-aminobutyryl-L-histidine) are abundant dipeptides in skeletal muscle and brain of most vertebrates and some invertebrates. The formation of both compounds is catalyzed by carnosine synthase, which is thought to convert ATP to AMP and inorganic pyrophosphate, and whose molecular identity is unknown. In the present work, we have purified carnosine synthase from chicken pectoral muscle about 1500-fold until only two major polypeptides of 100 and 90 kDa were present in the preparation. Mass spectrometry analysis of these polypeptides did not yield any meaningful candidate. Carnosine formation catalyzed by the purified enzyme was accompanied by a stoichiometric formation, not of AMP, but of ADP, suggesting that carnosine synthase belongs to the "ATP-grasp family" of ligases. A data base mining approach identified ATPGD1 as a likely candidate. As this protein was absent from chicken protein data bases, we reconstituted its sequence from a PCR-amplified cDNA and found it to fit with the 100-kDa polypeptide of the chicken carnosine synthase preparation. Mouse and human ATPGD1 were expressed in HEK293T cells, purified to homogeneity, and shown to catalyze the formation of carnosine, as confirmed by mass spectrometry, and of homocarnosine. Specificity studies carried out on all three enzymes were in agreement with published data. In particular, they acted with 15-25-fold higher catalytic efficiencies on beta-alanine than on gamma-aminobutyrate. The identification of the gene encoding carnosine synthase will help for a better understanding of the biological functions of carnosine and related dipeptides, which still remain largely unknown.