Analysis Of Phenylalanine Research Articles

Development of a simple method for the analysis of phenylalanine in dried blood spot using tandem mass spectrometry

BackgroundPhenylketonuria (PKU), inborn error of metabolism, results from phenylalanine hydroxylase deficiency. PKU leads to neurological manifestations, intellectual disability, and mental disorders. Treatment depends on phenylalanine-restricted diet.Diagnosis and follow-up of PKU depends on blood phenylalanine level. The development of bacterial inhibition assay was the first routine screening test for PKU. ELISA and amino acids analyzers methods were then developed.Tandem mass spectrometry was introduced for newborn screening from dried blood spot in the late 1990s. Since then, several methods were developed, starting from using HPLC column followed by direct injection in mass spectrometer by analyte derivatization and use of external and internal standards. Kits are available for neonatal screening without derivatization using internal standards for quantitation.Due to high PKU incidence in Egypt, it is important to continuously ameliorate the methods for neonatal diagnosis and follow-up.ResultsExternal standards as dried blood spots were prepared according to the previously described procedures. These standards were evaluated for phenylalanine concentration using ELISA kit. Analysis of samples was done with a single-step elution from dried blood spot followed by 1-min mass spectrometry analysis. Validation was done according to US FDA and other related guidelines. Fifty samples were analyzed by ELISA and another 126 samples were analyzed by mass spectrometer kit. All these samples were analyzed by the developed method and no statistically significant difference was observed.ConclusionNew simple method is developed for phenylalanine quantitation in dried blood spot using tandem mass spectrometry. This method is cost and time effective.

Rapid Determination of Phenylalanine by Micro-chip Based Field Asymmetric Waveform Ion Mobility Spectrometry Technology

Abstract The microchip field asymmetric ion mobility spectrometry (FAIMS) technology was used for rapid analysis of phenylalanine (PHE) using the metal diffusion tube-microchip μ-FAIMS system. The test pressure was set at 0.25 MPa, and the temperature of the gas generator for the diffusion tube was at 190 °C. The ion characteristic spectra were acquired under the optimized conditions with a gas flow rate of 2000 mL min −1 , a dispersion voltage of 152.8 V and a compensation voltage of −0.62 V for phenylalanine in positive mode. Phenylalanine gas samples with different concentrations were analyzed in detail by FAIMS. The results showed that the ion intensity was linearly correlated with phenylalanine concentration in the range from 6 mg L −1 to 20 mg L −1 , with the detection limit of 5.93 mg L −1 for phenylalanine. This investigation shows the feasibility of FAIMS technique for rapid detection of phenylalanine. The FAIMS instrument is simple, and has high sensitivity and fast response, and shows great potential for rapid detection of phenylalanine.

Spectrofluorimetric determination of phenylalanine based on fluorescence enhancement of europium ion immobilized with sol–gel method

The analysis of phenylalanine (Phe) in serum is widely performed for the screening of newborn phenylketonuria (PKU). In this work, a novel spectrofluorimetric method for the determination of Phe was developed based on the fluorescence enhancement of Ruhemann's purple, the reaction product between Phe and ninhydrin, upon coordination with Eu 3+. A filter paper disc containing immobilized reactants (ninhydrin and Eu 3+) was fabricated by sol–gel method. The experimental parameters affecting the determination of Phe, such as the concentrations of immobilized reagents, the pH value, the reaction time and temperature were optimized. Under optimum conditions, the fluorescence intensity of Phe–ninhydrin–Eu 3+ system was linearly proportional to the concentration of Phe in the range from 5 × 10 −5 to 2 × 10 −3 mol L −1, and the limit of detection was found to be 5.2 × 10 −6 mol L −1. The relative standard deviation was 2.6% for ten replicate measurements of 1.5 × 10 −4 mol L −1 of Phe. The method has merits of sensitivity, simplicity and low cost, and has been applied to the determination of Phe in artificial serum.

Predicting the phenylalanine blood concentration from urine analyses. An approach to noninvasive monitoring of patients with phenylketonuria

The need for regular blood-drawing in the management of chronic metabolic disorders may negatively influence the compliance of patients and their parents; noninvasive analytical procedures could well alleviate this burden. Using data obtained in six adult probands with phenylketonuria, we evaluate the feasibility of noninvasive prediction of phenylalanine blood concentrations from analysis of phenylalanine and creatinine in urine. Cross-validated regression equations correct for the significant inter-individual variation of phenylalanine fractional excretion rates. With sensitive and specific enzymatic assays for phenylalanine and creatinine, the accuracy of this noninvasive procedure may also become clinically satisfactory for the purpose of self-monitoring.

High-performance liquid chromatographic analysis of beta-phenylethylamine for the estimation of in vivo protein synthesis.

A rapid, sensitive, and automated reversed-phase liquid chromatographic method was developed for the analysis of phenylalanine as beta-phenylethylamine, for the measurement of in vivo protein synthesis. beta-Phenylethylamine was derivatized with o-phthaldialdehyde (OPA) to form a fluorescent derivative that was successfully measured in tissue cell fluids and hydrolysates as the decarboxylation product of phenylalanine. The system was extremely sensitive enabling the accurate determination of 0.5 pmol in biological samples. Analysis time was less than 11 min, so that 130 samples can be analysed per day. The method eliminates the need for time-consuming column extraction procedures. This method offers substantial advantages over existing methods for the isolation and determination of beta-phenylethylamine.

Post-column detection by on-line photolysis—electrochemistry in liquid chromatography: Application to the determination of phenylalanine in human urine

On-line, post-column photochemical derivatization for liquid chromatography-electrochemical detection (LC-hv-EC) has been employed for the analysis of phenylalanine in urine. The method is highly sensitive and selective. The quantitative results show good precision and reproducibility. It can be used easily and has the clinical use of diagnosing phenylketonuria disease.

Narrow-bore liquid chromatography with multichannel detection in paediatric biochemistry: Analysis of phenylalanine and tyrosine in phenylketonuria

In paediatric biochemistry, the analysis of drugs and endogenous compounds in preterm or low-birth weight neonates presents particular analytical problems. Sensitive techniques with small sample capacity are essential and in this context, narrow-bore (1–2mm) LC columns, coupled with appropriate low-volume detector cells and connections to reduce band dispersion, have been shown to offer significant advantages. By comparison with conventional columns an increase in sensitivity by a factor ofca. 2 can be achieved. The combination of narrow-bore columns and rapid-scanning UV detectors in reversed-phase LC enables the spectral information to be used for both peak recognition and homogeneity validation. Furthermore, “diode bunching” in the wavelength domain leads to a further two-fold increase in sensitivity. This combination of column and detector technology has been utilised in the design of a sensitive serum micro-assay of the essential aromatic amino acids in paediatric samples, capable of being used with 500nl sample, sensitive to 13pg phenylalanine and 9pg tyrosine and linear over the requisite therapeutic range.

Dual-channel continuous-flow system for determination of phenylalanine and galactose: application to newborn screening.

We describe a dual-channel AutoAnalyzer (Technicon) system for the simultaneous measurement of phenylalanine and galactose from blood specimens on filter-paper. Using a single 1/4-in.-diameter (6-mm) specimen, we measure both components fluorometrically at a rate of 70/h. Analytical recovery with the method and the linearity of measurements vs sample concentration are excellent through the ranges of interest, 0-200 mg/L for phenylalanine and 0-800 mg/L for galactose. Carryover at the critical values during screening, 40 mg/L for phenylalanine and 100 mg/L for galactose, is essentially zero. The dual-channel system provides the means to incorporate a low-incidence test, i.e., galactosemia (incidence 1/70 000), into an existing program for phenylalanine analysis, for which the higher rates (phenylketonuria, incidence 1/11 500) easily justify the cost of mass screening.

ChemInform Abstract: PHENYLALANYL TRANSFER RIBONUCLEIC ACID SYNTHETASE FROM RAT LIVER. ANALYSIS OF PHENYLALANINE AND ADENOSINE 5′‐TRIPHOSPHATE BINDING SITES AND COMPARISON TO THE ENZYME FROM ESCHERICHIA COLI

Chemischer InformationsdienstVolume 8, Issue 9 Isocyclic Compounds ChemInform Abstract: PHENYLALANYL TRANSFER RIBONUCLEIC ACID SYNTHETASE FROM RAT LIVER. ANALYSIS OF PHENYLALANINE AND ADENOSINE 5′-TRIPHOSPHATE BINDING SITES AND COMPARISON TO THE ENZYME FROM ESCHERICHIA COLI D. V. SANTI, D. V. SANTISearch for more papers by this authorR. W. JUN. WEBSTER, R. W. JUN. WEBSTERSearch for more papers by this author D. V. SANTI, D. V. SANTISearch for more papers by this authorR. W. JUN. WEBSTER, R. W. JUN. WEBSTERSearch for more papers by this author First published: March 1, 1977 https://doi.org/10.1002/chin.197709198Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue9March 1, 1977 RelatedInformation

Phenylalanyl transfer ribonucleic acid synthetase from rat liver. Analysis of phenylalanine and adenosine 5'-triphosphate binding sites and comparison to the enzyme from Escherichia coli

Inhibition of the ATP--PPi exchange reaction catalyzed by rat liver phenylalanyl-tRNA synthetase by structural analogues of L-phenylalanine and ATP has been examined and compared with data reported for the enzyme from E. coli. The phenylalanine binding sites are similar in the following characteristics. (1) The region that complexes the phenyl ring shows a strict requirement for the unsubstituted phenyl ring altough the rat liver enzyme is more tolerant in this respect. (2) The protonated amino group of phenylalanine is required for binding. (3) The region neighboring the binding site for the carboxylate of phenylalanine is diffusely hydrophobic. Unlike effects of these modifications on interaction with the E. coli enzyme, substitution of the carboxylate by hydrophobic groups leads to large losses in affinity for the rat liver enzyme. Although both enzymes bind D-phenylalanine very poorly, their relative affinities for the D isomers of phenylalanine analogues vary greatly. The most dramatic difference is observed with N-benzyl-D-amphetamine, which binds 24 000-fold tighter to E. coli phenylalanyl-tRNA synthetase than the rat liver enzyme. The affinity of rat liver phenylalanyl-tRNA synthetase for naturally occurring adenine compounds is similar to that of the E. coli enzyme, suggesting that the binding of ATP occurs via similar interactions. Adenine provides a major protion of the free energy of binding of ATP. The remainder may be viewed as the sum of detrimental interactions with the phosphate groups of ATP and a favorable contribution by the ribose moiety.

Filter Paper Blood Collection and Punching As A Means of Quantification

Abstract Filter paper has been tested as a medium for the collection of blood samples for the subsequent elution and analysis of phenylalanine, tyrosine, glucose, and urea nitrogen. The use of paper did not measurably alter the precision of the above methods. The paper punch as a means of quantification has been compared with the more commonly used technic of volumetric measurement. The precision obtained with punched spots was found to be similar to that found with measured spots for the above four procedures and for weighed samples. The hematocrit value was found to have an influence on the volume of blood contained in a punched spot. Differences in spreading through filter paper between 100 individual blood samples tested did not seem to be responsible for a variance in excess of that introduced by the analytic procedures themselves.