Quantification Of Phenylalanine Research Articles

Simultaneous Identification and Quantification of Phenylalanine, Glycine and Lysine amino acids and conjugated heterocyclic amines in Maillard chemical model system using RP-HPLC-DAD

In this study, we developed a simple reversed-phase high-performance liquid chromatography (RP-HPLC) methodology for simultaneous identification and quantification of three types of mix: (1) phenylalanine and PHIP; (2) glycine and MeIQx; (3) lysine and 4,8 DiMeIQx in Maillard chemical model systems. In addition, we investigated the effects of different conditions on decreasing amino acids and heterocyclic amines (HCA) formation in chemical model systems. The results show that the developed methods used to separate the proposed mixes gave a relative standard deviation (RSD)% of less than 2% of peak area and retention time, thus proving the robustness and high reproducibility of the proposed method. The relationship between concentration and peak areas is linear with high statistical significance (p<0.001). The residual and slope of linear regression give a limit of detection LoD) and (LoQ) of phenylalanine and PHIP were (2.92- 0.029 ppm),(9.73- 0.098 ppm),respectively, which indicate the high sensitivity of the developed method. Moreover, the findings illustrate that a water ratio of 20% leads to a decrease in phenylalanine versus the largest amount of PHIP, and phenylalanine is the most active amino acid with a decreasing percentage up to 99%.

Ultrafiltration-based Extraction and LC-MS/MS Quantification of Phenylalanine in Human Blood Sample for Metabolite Target Analysis

Background: Phenylalanine is a significant biomarker for various diseases like phenylketonuria, gastric cancers, and ischemic stroke according to recent studies. Methods: In the present study; a simple, sensitive, selective and novel analytical method was validated by using an ultrafiltration-based extraction and LC-MS/MS quantification of phenylalanine in human plasma using 13C phenylalanine heavy isotope. Amicon® Ultra Centrifugal Filter was used for ultrafiltration. Parameters affecting LC separation and MS/MS detection were investigated and optimized. Chromatographic separation was achieved on a Merck SeQuant ZIC-HILIC (100x4.6 mm, 5 μm) at a column temperature of 40°C using a mobile phase of mixture of acetonitrile containing 0.1% formic acid and water containing 0.1% formic acid (50:50 v/v) at a flow rate of 0.35 mL/min. The transitions m/z 167→121 for 13C phenylalanine, m/z 166→120 for phenylalanine itself were monitored using the MRM mode. Result: The assay was linear concentration range of 0.0025 μg/mL to 1.20 μg/mL (R2=0.999). The developed method was validated according to FDA guidelines. The method was found linear, sensitive, precise, accurate, and selective.

Capture of Phenylalanine and Phenylalanine-Terminated Peptides Using a Supramolecular Macrocycle for Surface-Enhanced Raman Scattering Detection.

The cucurbit[n]uril (CB[n]) family of macrocycles are known to bind a variety of small molecules with high affinity. These motifs thus have promise in an ever-growing list of trace detection methods. Surface-enhanced Raman scattering (SERS) detection schemes employing CB[n] motifs exhibit increased sensitivity due to selective concentration of the analyte at the nanoparticle surface, coupled with the ability of CB[n] to facilitate the formation of well-defined electromagnetic hot spots. Herein, we report a CB[7] SERS assay for quantification of phenylalanine (Phe) and further demonstrate its utility for detecting peptides with an N-terminal Phe. The CB[7]-guest interaction improves the sensitivity 5-25-fold over direct detection of Phe using citrate-capped silver nanoparticle aggregates, enabling use of a portable Raman system. We further illustrate detection of insulin via binding of CB[7] to the N-terminal Phe residue on its B-chain, suggesting a general strategy for detecting Phe-terminated peptides of clinically relevant biomolecules.

Nano-Calorimetry based point of care biosensor for metabolic disease management.

Point of care (POC) diagnostics represents one of the fastest growing health care technology segments. Developments in microfabrication have led to the development of highly-sensitive nanocalorimeters ideal for directly measuring heat generated in POC biosensors. Here we present a novel nano-calorimeter-based biosensor design with differential sensing to eliminate common mode noise and capillary microfluidic channels for sample delivery to the thermoelectric sensor. The calorimeter has a resolution of 1.4±0.2 nJ/(Hz)1/2 utilizing a 27 junction bismuth/titanium thermopile, with a total Seebeck coefficient of 2160μV/K. Sample is wicked to the calorimeter through a capillary channel making it suitable for monitoring blood obtained through a finger prick (<1μL sample required). We demonstrate device performance in a model assay using catalase, achieving a threshold for hydrogen peroxide quantification of 50μM. The potential for our device as a POC blood test for metabolic diseases is shown through the quantification of phenylalanine (Phe) in serum, an unmet necessary service in the management of Phenylketonuria (PKU). Pegylated phenylalanine ammonia-lyase (PEG-PAL) was utilized to react with Phe, but reliable detection was limited to <5mM due to low enzymatic activity. The POC biosensor concept can be multiplexed and adapted to a large number of metabolic diseases utilizing different immobilized enzymes.

Synthesis, Application, and Molecular Recognition Mechanism Study of Phenylalanine Molecularly Imprinted Polymer

Phenylalanine molecularly imprinted polymer was synthesized in the presence of triflouroacetic acid. HPLC‐MS evaluation showed it had good affinity toward its template among 16 amino acid mixtures. It was used for quantification of phenylalanine in protein hydrolysis solution and in serum without sample pre‐treatment. Further study revealed the molecular recognition mechanism involved size exclusion, hydrophobic interaction, and hydrogen bonding interaction. The molecularly imprinted polymer presented here can be used for actual sample analysis and the well characterized recognition mechanism can benefit the design, synthesis, and application of MIP.

Analysis of optical purity and impurity of synthetic d‐phenylalanine products using sulfated β‐cyclodextrin as chiral selector by reversed‐polarity capillary electrophoresis

A new capillary electrophoresis (CE) method has been achieved for simultaneous separation and quantification of phenylalanine, N-acetylphenylalanine enantiomers, and prochiral N-acetylaminocinnamic acid, possibly co-existent in reaction systems or synthesized products of D-phenylalanine. The separation was carried out in an uncoated capillary under reversed-electrophoretic mode. Among the diverse charged cyclodextrins (CDs) examined, highly sulfated (HS)-beta-CD as the chiral selector exhibited the best enantioselectivity. The complete separation of the analytes was obtained under the optimum conditions of pH 2.5, 35 mM Tris buffer containing 4% HS-beta-CD, applied voltage -15 kV, and capillary temperature 25 degrees C. Furthermore, the proposed method was applied to the determination of optical purity and trace impurities in three batches of the asymmetric synthetic samples of D-phenylalanine, and satisfactory results were obtained. The determination recoveries of the samples were in the range of 97.8-103.8%, and precisions fell within 2.3-5.0% (RSD). The results demonstrate that this CE method is a useful, simple technique and is applicable to purity assays of D-phenylalanine.

Quantification of phenylalanine in serum with a centrifugal analyzer.

Quantification of phenylalanine in serum with a centrifugal analyzer.