Tryptophan In Aqueous Solution Research Articles

Construction of a novel coordination polymer for selective fluorescence recognition and efficient adsorption of tryptophan in aqueous solution

The efficient separation and purification of L-tryptophan (L-Trp) from fermentation broth are essential for reducing production costs. Here, we report a new 1,1́-binaphthyl-based copper coordination polymer (R-Cu CP) that enables selective fluorescence recognition and efficient adsorption of L-Trp from aqueous solutions. A three-dimensional (3D) CP with a suitable cavity size (17 × 8 Å) was constructed by coordinating copper ions with the dicarboxylate ligand (R)-H3L derived from 1,1́-binaphthyl phosphoric acid. The prepared R-Cu CP exhibits extraordinary adsorption of L-Trp, up to 1055 mg/g. The specific fluorescence quenching response to L-Trp can be achieved by the ultrasonic exfoliation of two-dimensional (2D) CP nanosheets (CPNs). X-ray photoelectron spectroscopy and density functional theory calculations revealed that the efficient adsorption of L-Trp by R-Cu CP is due to the synergistic effect of coordination interactions, hydrogen bonding interactions, electrostatic interactions, and host–guest interactions, and the quenching mechanism is attributed to the photoinduced electron transfer from L-Trp to R-Cu CP and the competitive absorption of excitation energy by L-Trp.

Measurement and Correlation of Solubility of L–Tryptophan in Aqueous Solutions with a Wide Range of pH and Different Monovalent Counterions from 283.15 to 323.15 K

Measurement and Correlation of Solubility of L–Tryptophan in Aqueous Solutions with a Wide Range of pH and Different Monovalent Counterions from 283.15 to 323.15 K

Molecularly imprinted polymer functionalized silica nanoparticles for enantioseparation of racemic tryptophan in aqueous solution.

A method has beendeveloped for preparation of surface molecularly imprinted polymer functionalized silica nanoparticles (SiO2@MPS@MIP). Firstly, the silica nanoparticles are prepared by a one-pot sol-gel method using tetraethylorthosilicate and 3-methacryloxypropyltrimethoxysilane as functional monomers. Next, the template molecule (L-Trp) is self-assembled with the functional monomer (acrylamide). Finally, SiO2@MPS@MIP are prepared using N,N'-methylenebisacrylamide as the cross-linker. The prepared SiO2@MPS@MIP have an average diameter of about 6.3 ± 1.2nm. They exhibit good selectivity toward L-Trp with an imprinting factor of 6.3. The adsorption isotherm data was well described by the Langmuir model. The maximum adsorption capacities of SiO2@MPS@MIP for L-Trp and D-Trp were calculated to be 11.1 ± 0.9 and 2.66 ± 0.16mgg-1, respectively. An enantiomer excess value of 100% was achieved after adsorption of racemic Trp by the material. The work suggests that SiO2@MPS@MIP are a promising material for enantioseparation of Trp racemate in aqueous media. Graphical abstract.

Electrochemiluminescence analysis of tryptophan in aqueous solutions based on its reaction with tetraphenylborate anions.

The emission of electrogenerated chemiluminescence (ECL) is observed upon the oxidation of fluorescent aromatic amino acid tryptophan in aqueous solutions at a glassy carbon electrode in the presence of a sodium tetraphenylborate co-reactant in a broad pH range. The emission is particularly strong when potential pulses are applied to the electrode. The ECL intensity is proportional to the concentration of amino acid and allows its determination in the concentration range of 0.3 μM-0.3 mM with high selectivity in the presence of other amino acids. The results of studies suggest that the indole ring of tryptophan is responsible for the observed ECL emission.

Construction of IAA-Deficient Mutants of Pseudomonas moraviensis and Their Comparative Effects with Wild Type Strains as Bio-inoculant on Wheat in Saline Sodic Soil

Tryptophan role in microbial biosynthesis of Indole Acetic Acid (IAA) is very distinct. In present study IAA producing bacteria Pseudomonas moraviensis was applied on wheat for improving growth and physiology; in the presence or absence of L-tryptophan in saline sodic field. Aqueous solution of tryptophan was added to the rhizosphere soil at 10 mg L−1 with irrigated water. The survival efficiency of P. moraviensis measured in the presence of NaCl and mixture of salts. P. moraviensis increased P, NO3–N and K contents in soil by 18–35% and further 12–15% increase was recorded in the presence of tryptophan. There were 40–80% increases in indole acetic acid (IAA), abscisic acid (ABA) and gibberellic acid (GA) contents of rhizosphere soil, and 40–45% increase in leaves when tryptophan was added with P. moraviensis. In the second phase, IAA deficient mutants of P. moraviensis were constructed and tested for the conversion of tryptophan to IAA. In transposon mutagenesis, 1800 trans-conjugants were generated and tested for tryptophan conversion. Among these, 11 mutants were selected and inoculated into wheat to compare their growth responses to the wild type. P. moraviensis wild type served as PGPR under salinity, but IAA- deficient mutants of P. moraviensis were unable to produce IAA and halted plant growth.

Photosensitizing Activity of Steroid Derivatives of Pyropheophorbide in the Oxidation of Tryptophan in the Aqueous Phase

Solubilization with pluronic F-127 gave water-soluble forms of hydrophobic photosensitizers—steroid derivatives of pyropheophorbide a. Solubilization was performed by evaporating the chloroform co-solutions of photosensitizer and pluronic (triple block copolymer of ethylene and propylene oxide) and subsequently dissolving the resulting dry residue in water. The concentration ratios of modified pyropheophorbide–pluronic at which the photosensitizer completely passed into the aqueous phase were determined. Among the starting hydrophobic photosensitizers, pyropheophorbide–dihydrotestosterone possessed the highest activity in photosensitized oxidation of anthracene with singlet oxygen in chloroform, while after solubilization, pyropheophorbide–testosterone was most active in the test (for photodynamic therapy) oxidation of tryptophan in aqueous solutions.

Voltammetric analysis of mycophenolate mofetil in pharmaceutical samples via electrochemical nanostructure based sensor modified with ionic liquid and MgO/SWCNTs

Abstract Mycophenolate is an immunosuppressant drug that used for the prevention of organ transplant rejection and determination of this drug is very important. A sensitive voltammetric sensor based on carbon paste electrode modified with magnesium oxide nanoparticle decorated at single wall carbon nanotubes (MgO/SWCNTs) and n -hexyl-3-methylimidazolium hexafluoro phosphate (HMIPF 6 ) (HMIPF 6 /MgO/SWCNTs/CPE) was fabricated for determination of mycophenolate mofetil in the presence of tryptophan in aqueous solution for the first time. MgO/SWCNTs were synthesized by chemical precipitation method using SWCNTs/COOH, magnesium nitrate and sodium hydroxide as a precursor. Also, MgO/SWCNTs were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDAX) methods. The mycophenolate mofetil and tryptophan were given two separated oxidation peaks at 675 mV and 865 mV, which is sufficient for simultaneous determination of them. The HMIPF 6 /MgO/SWCNTs/CPE displayed excellent catalytic activities toward electro-oxidation of mycophenolate mofetil compared to bare CPE. The HMIPF 6 /MgO/SWCNTs/CPE showed linear responses in the range 0.1–450.0 µM with detection limit 0.07 µM for mycophenolate mofetil analysis. The F -test and Student's t -test confirmed good ability of sensor for determination of mycophenolate mofetil in real samples.

Assorted interactions of amino acids prevailing in aqueous vitamin C solutions probed by physicochemical and ab-initio contrivances

Qualitative and quantitative analysis of molecular interaction prevailing in tyrosine and tryptophan in aqueous solution of vitamin C have been probed by thermophysical properties. The apparent molar volume (ϕV), viscosity B-coefficient, molal refraction (RM) of tyrosine and tryptophan have been studied in aqueous vitamin C solutions at diverse temperatures via Masson equation which deduced solute-solvent and solute-solute interactions, respectively. Spectroscopic study along with physicochemical and computational techniques provides lots of interesting and highly significant insights of the model biological systems. The overall results established strong solute-solvent interactions between studied amino acids and vitamin C mixture in the ternary solutions.

Kinetics of photoinduced electron transfer reactions of ruthenium(II) complexes and phenols, tyrosine, N-acetyl-tyrosine and tryptophan in aqueous solutions measured with modulated fluorescence spectroscopy

Photooxidation kinetics of phenol, 1-naphthol, 2-naphthol, tyrosine (TyrOH) and N-acetyl-tyrosine (AcTyrOH), tryptophan (TrpH) by ruthenium(II) polypyridyl complexes: [Ru(bpy)3]Cl2 (1), [Ru(phen)3]Cl2 (2), [Ru(bpy)(phen)(bpg)]Cl2 (3), and [Ru(dpq)2(bxbg)]Cl2 (4) where bpy is 2,2′-bipyridine, phen – 1,10-phenanthroline, bpg – bipyridine-glycoluril, dpq – dipyrido[3,2-d:2′,3′-f]quinoxaline, and bxbg – bis(o-xylene)bipyridine-glycoluril are investigated. Rate constants have been measured by steady-state luminescence and phase-modulation fluorometry in aqueous solutions at different pH's. The rates for the oxidation of the phenols and phenolic aromatic amino acids spreads over a wide range from 4.2×106 to 6.8×109M−1s−1, depending on pH and the nature of solutes. At pH>pKa of the quenchers, the presence of reactive species (PhO−) in the alkaline solutions is accounted for the rapid ET rates. In the pH range between 4 and 10 (pH<pKa), the ETPT mechanism becomes dominate and the rate constants are relatively low. It reveals that the important parameters that influence the quenching reaction rates, others than the driving forces ∆G0 are the steric and hydrophobic interactions arising from the structure of the compounds. This is clearly seen in the case of photoreaction between the Ru(phen)32+ complex and AcTyrOH. Phen ligands and acetyl group cause a steric effect, but strengthen the hydrophobic interactions and thus promote the quenching process. The pH-dependent equation of the observed rate constant for PhOH/AcTyrOH oxidation is expressed as a sum of rates for its protonated, neutral and deprotonated forms.

Comparative effects of wild type Stenotrophomonas maltophilia and its indole acetic acid-deficient mutants on wheat.

The present investigation evaluated the role of Stenotrophomonas maltophilia and its IAA-deficient mutant on soil health and plant growth under salinity stress in the presence of tryptophan. In the first phase, S. maltophilia isolated from roots of the halo- phytic herb, Cenchrus ciliaris was used as bio-inoculant on wheat grown in saline sodic soil. A field experiment was conducted at Soil Salinity Research Institute during 2010-2011. Treatments included seed inoculation with S. maltophilia with or without tryptophan; uninoculated untreated plants were taken as control. An aqueous solution of tryptophan was added to rhizosphere soil at 1 μg l(_1) after seed germination. Inoculation with S. maltophilia significantly increased soil organic matter, enhanced (20-30%) availability of P, K, Ca and NO3 -N and decreased Na content and electrical conductivity of rhizosphere soil. Plant height, fresh weight, proline and phytohormone content of leaves were increased 30-40% over the control. Activities of superoxide dismutase (SOD) and peroxidase (POD) were 40-50% higher than control. Addition of tryptophan further augmented (10-15%) growth parameters, whereas NO3 -N, P, K and Ca content, proline content and SOD and POD increased 20-30%. In a second phase, indoleacetic acid (IAA)-deficient mutants of S. maltophilia were constructed and evaluated for conversion of tryptophan to IAA at the University of Calgary, Canada, during 2013-2014. About 1800 trans-conjugants were constructed that were unable to produce IAA in the presence of tryptophan. The results suggest that tryptophan assisted S. maltophilia in the amelioration of salt stress, and that IAA played positive role in induction of salt tolerance.

Unraveling the intramolecular cyclization mechanism of oxidized tryptophan in aqueous solution as a function of pH

The aqueous intramolecular cyclization of 3a-hydroperoxitryptophan, Trp-OOH, (an intermediate in the photodynamic treatment of cancer) is studied at the PCM-MP2/aug-cc-pVDZ//PCM-B3LYP/aug-cc-pVDZ computational level with and without explicit water molecules. The three-cycle product may evolve to the metabolite N-formyl kynurenine in living beings or can be a building block in the formation of indole alkaloids in organic synthesis. When the pH is close to the isoelectric point of tryptophan, we have found two cyclization mechanisms, one passing along zwitterion intermediates, I-route (beginning with a proton transfer from the ammonium to the N-indole atom) and the other involving neutral isomers, C-route (starting with the attack of N-amino to C2-indole). At this pH, the discrete-continuum model with six explicit water molecules predicts a Gibbs energy barrier of 14.6 kcal mol(-1) for the I-route and of 11.6 kcal mol(-1) for the C-route. It is possible to experimentally tune the operating mechanism since in acidic environments only the I-route is available (Gibbs energy barrier of 8.4 kcal mol(-1)) whereas in basic media only the C-route can operate (Gibbs energy barrier of 6.7 kcal mol(-1)). These data explain the trend of Trp-OOH to easily decompose under basification.

The stimulatory effects of L-tryptophan and plant growth promoting rhizobacteria (PGPR) on soil health and physiology of wheat

During the present study, Pseudomonas moraviensis and Bacillus cereus, were isolated from rhizosphere soil of halophytic weed (cenchrus ciliaris L.) of Khewra salt range, and used as bioinoculants. The plant growth promoting rhizobacteria (PGPR) were applied to wheat (Triticum aestivum) by seeds soaking, and aqueous solution of tryptophan was added to the rhizosphere soil at 1ug/L, after seed germination. Experiment was conducted at Quaid-e-Azam University Islamabad both in pots (filled with sterilized soil) under axenic condition and in field under natural condition, for two consecutive years. The inoculation of Pseudomonas moraviensis and Bacillus cereus, significantly increased the organic matter, P, K, Ca, and NO 3 -N availability of soil. The inoculation of these PGPR positively enhanced growth and physiology of treated plants, and this affect was further augmented in the presence of tryptophan. Addition of tryptophan with Pseudomonas moraviensis and Bacillus cereus increased the fresh weight, proline contents and activities of antioxidant enzymes significantly over control. Added tryptophan with both PGPR, improved the number of plants at yield and seeds establishment by improving number of seeds/spike and spike length. Effects of PGPR inoculation alone and with tryptophan were more pronounced in pots grown plants. It is inferred from the results, that tryptophan addition is a competent source for increasing potential of PGPR, thereby improving wheat growth, and physiology.

Heavy atom induced phosphorescence study on the influence of internal structural factors on the photophysics of tryptophan in aqueous solutions

In this study the effect of alanyl residue insertion into tryptophan and to some extent the effect of peptide bond on the photophysics of tryptophan chromophore has been studied. The photophysical parameters crucial in triplet state decay mechanism of aqueous AW, WA and AWA peptides have been determined applying our previously proposed methodology based on the heavy atom effect and compared with the previously reported values for tryptophan (Kowalska-Baron et al., 2012). The obtained results clearly indicated that the presence of alanyl residue and the peptide bond results in the changes in the fluorescence and phosphorescence decay kinetics of tryptophan. The fluorescence decays of the oligopeptides studied at pH 7 were biexponential. The longer lifetime component of WA arises from anionic form of this dipeptide, while the shorter one may be assigned to the zwitterionic form of WA. The observed invariance of the lifetimes of anionic and zwitterionic forms of WA throughout the pH studied supports the idea that these two components of WA fluorescence decay correspond to nearly independent species, possibly interconverting but at a rate slower than the fluorescence decay rates. Comparing the determined phosphorescence spectra of the oligopeptides studied with that of tryptophan, a slight blue-shift and more evident red-shift was observed in the spectrum of AW and WA, respectively. On the basis of the results of the phosphorescence measurements performed at pH 10, the 170μs lifetime of WA, observed even at pH 7, may be assigned to the anionic form of the compound. It may be suggested that at pH 7 during the excited triplet state lifetime of WA there is a shift in the equilibrium towards the anionic form of this dipeptide. In the case of AW and AWA at pH 7 the obtained monoexponential decay kinetics, most probably, arise from zwitterionic forms of these peptides. The determined triplet quantum yield of AWA is slightly lower than that of tryptophan, while the quantum yield of AW is twofold lower than that of tryptophan. The highest value of the determined triplet quantum yield of WA confirms the presence of anionic form of this dipeptide at pH 7.

The effect of lead cations on the fluorescence characteristics of bovine serum albumin in aqueous solution

The effect of lead (heavy metal) cations on the fluorescence characteristics and photophysical parameters (fluorescence intensity and anisotropy, absorption cross section, excited state lifetime, and rates of singlet-triplet conversion and reversible photobleaching) of tryptophan in an aqueous solution of bovine serum albumin (two-tryptophan protein) is studied and compared with the effect in the aqueous solution of tryptophan. It is demonstrated that the effect of lead on the fluorescence characteristics of the protein is manifested at a molar concentration ratio of metal cations and protein macromolecules of greater than 10 and related to the dynamic quenching of the excited state, protein aggregation, and an increase in the rate of singlet-triplet conversion (the effect of a heavy atom) in tryptophan molecules.

Fluorescence of tryptophan in aqueous solution

In this work, the absorption and emission spectra of Tryptophan (Trp) in aqueous solution were studied. Moreover, a hydrogen-bonded zwitterionic Trp(H2O)9 model was proposed and its ground-state and excited-state properties were investigated using the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) methods, respectively. All spectroscopic data in our experiments can be well explained by the hydrogen bond strengthening in the excited state of the model complex. The delocalization of electron density between indole moiety and neighboring H2O molecules in fluorescent state was proposed to be facilitated by the strengthened hydrogen-bond chain, and thus resulting in the large red-shift fluorescence of Trp in aqueous solution.

Structural Heterogeneity in the Collision Complex between Organic Dyes and Tryptophan in Aqueous Solution

The heterogeneity on photoinduced electron transfer (PET) kinetics between a labeled fluorophore and an amino acid residue has been extensively studied in biopolymers. However in aqueous solutions, the heterogeneity on PET kinetics between a fluorophore and a quencher has rarely been reported. Herein, we selected four commonly used fluorophores, such as tetramethylrhodamine (TMR), Rhodamine B (RhB), Alexa fluor 546 (Alexa546), and Atto655, and studied their respective PET kinetics in 50 mM tryptophan solutions with femtosecond transient absorption spectroscopy to explore the structural heterogeneity in their corresponding collision complexes. We measured the decay of the first excited electronic state of respective fluorophore with and without 50 mM tryptophan in aqueous solutions, and derived the charge separation rate in their corresponding collision complexes. We found that the PET process of all selected fluorophores in 50 mM tryptophan solutions has two charge separation rates, which indicates that the relevant states in the collision complex between respective fluorophore and tryptophan have strong structural heterogeneity. These femtosecond PET measurements are in agreement with Vaiana's molecular dynamics simulation (J. Am. Chem. Soc.2003, 125, 14564). In addition, with the obtained PET kinetic parameters, we derived the relative brightness of the collision complex between respective fluorophore and tryptophan, which are important parameters for the PET based fluorescence correlation spectroscopy study involving these fluorophores in biopolymers.

Computational protocols for prediction of solute NMR relative chemical shifts. A case study of L‐tryptophan in aqueous solution

In this study, we have applied two different spanning protocols for obtaining the molecular conformations of L-tryptophan in aqueous solution, namely a molecular dynamics simulation and a molecular mechanics conformational search with subsequent geometry re-optimization of the stable conformers using a quantum mechanically based method. These spanning protocols represent standard ways of obtaining a set of conformations on which NMR calculations may be performed. The results stemming from the solute-solvent configurations extracted from the MD simulation at 300 K are found to be inferior to the results stemming from the conformations extracted from the MM conformational search in terms of replicating an experimental reference as well as in achieving the correct sequence of the NMR relative chemical shifts of L-tryptophan in aqueous solution. We find this to be due to missing conformations visited during the molecular dynamics run as well as inaccuracies in geometrical parameters generated from the classical molecular dynamics simulations.

Photophysical Properties of Atto655 Dye in the Presence of Guanosine and Tryptophan in Aqueous Solution

Atto655 has been widely used as an excellent probing dye through photoinduced electron transfer (PET) for biochemical processes in oligonucleotides or polypeptides. However, its photophysical properties in the presence of the quenchers guanosine and tryptophan have not been carefully studied. In this work, we investigated the dynamics of PET between Atto655 and the two quenchers in aqueous solution with femtosecond transient absorption experiments. We derived that the charge separation rate is 8.1 × 10(9) s(-1) and the charge recombination rate is 7.7 × 10(10) s(-1) for the collision complex between Atto655 and guanosine and that the corresponding values for the collision complex between Atto655 and tryptophan are 4.0 × 10(11) and 5.0 × 10(12) s(-1), respectively. These experimental results are quite consistent with the prediction of Marcus-type theory for electron transfer. The implications of this work for the data analysis of PET-based fluorescence correlation spectroscopy are discussed.

Complex formation of tetrakis(4-sulfonatophenyl)porphyrin with γ-cyclodextrin, phenylalanine, and tryptophan in aqueous solution

In pH 10.3 buffer, in which phenylalanine and tryptophan are in an anionic form, the interactions of tetrakis(4-sulfonatophenyl)porphyrin (TSPP) with γ-cyclodextrin (γ-CD) and phenylalanine (or tryptophan) have been examined by means of absorption and fluorescence spectroscopy. A 1:1 inclusion complex is formed between TSPP and γ-CD. TSPP forms 1:2 complexes with l- and d-phenylalanine (LPhe and DPhe), while TSPP forms 1:1 complexes with l- and d-tryptophan (LTrp and DTrp). In TSPP solution containing γ-CD and LPhe (or DPhe), the 1:1:2 γ-CD–TSPP–LPhe (or –DPhe) inclusion complex is formed, while the 1:1:1 γ-CD–TSPP–LTrp (or –DTrp) inclusion complex is formed for LTrp (or DTrp). The equilibrium constants for the formation of the complexes have been evaluated from the fluorescence intensity change of TSPP. The equilibrium constants are nearly the same for the optical isomers of phenylalanine and tryptophan, respectively, indicating that the optical isomers are not discriminated through the complexation. For the LPhe complexes, the equilibrium constants have also been evaluated at a fixed ionic strength of 0.2 mol dm−3 using NaCl. 3-Phenyl-1-propanol and l-phenylalaninol, which are analogous to phenylalanine in molecular structure, have been examined for the complexation with TSPP and γ-CD. In contrast to phenylalanine, the stoichiometries of their binary complexes with TSPP and their ternary inclusion complexes with γ-CD and TSPP are 1:1 and 1:1:1, respectively.

1,1′-Binaphthyl-based imidazolium chemosensors for highly selective recognition of tryptophan in aqueous solutions

A type of 1,1'-binaphthyl-based imidazolium chemosensor module has been synthesized for the highly selective recognition of tryptophan (Trp) among the eleven alpha-amino acids investigated in aqueous solutions via synergistic effects of multiple hydrogen bonding and electrostatic interactions. These results have demonstrated that the C-2 hydrogen atom of the imidazolium ring plays a key role as a hydrogen bond donor. The UV/vis, fluorescence and mass spectral studies have indicated that a 1 : 1 complex is formed between the host and tryptophan. The binding affinity and selectivity of the cleft-like receptor (R)- with l-Trp are superior to those of (R)-. In spite of an inferior selectivity towards various aromatic amino acids, the macrocyclic (R)- displays a remarkable enantiodiscrimination for the two enantiomers of tryptophan with a K(D)/K(L) value as high as 6.2.