Analysis Of Tyrosine Research Articles

Manganese tetraphenylporphyrin and carbon nanocoil interface-based electrochemical sensing of tyrosine.

Tyrosine is one of the essential metabolites present in the human body for nutritional maintenance and normal physiological functioning. Its concentration in the body is crucial in predicting various hereditary, emotional, and physiological disorders. Therefore, quantitative monitoring of tyrosine in clinical samples is indispensable. We state the use of carbon nanocoils/manganese tetraphenylporphyrin convened glassy carbon electrode (CNC/MnTPP/GC) for the streamlined electrochemical sensing of tyrosine. Cutting-edge analytical techniques were employed to perform a comprehensive physicochemical analysis of the synthesized materials. To investigate the electrochemical properties, various techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy, and chronocoulometry were employed. CNC/MnTPP/GC displayed an optimal response at pH 5 and exhibited remarkable linearity within the concentration range of 0.05 to 100 μM for tyrosine. Using DPV, it demonstrated a low limit of detection (21 nM ± 1.17) and a sensitivity of 0.12 μA μM-1 cm-2. CNC/MnTPP/GC displayed excellent performance in terms of repeatability, reproducibility, and stability for up to 30 days, making it suitable for real-time analysis, particularly in the analysis of tyrosine in blood serum. Notably, CNC/MnTPP/GC showcased a superior detection limit compared to previously reported methods.

Biosensing Applications of ZnO / Graphene on Glassy Carbon Electrode in Analysis of Tyrosine

Biosensing Applications of ZnO / Graphene on Glassy Carbon Electrode in Analysis of Tyrosine

Finding the same needles in the haystack? A comparison of phosphotyrosine peptides enriched by immuno-affinity precipitation and metal-based affinity chromatography

Analysis of tyrosine (Tyr) phosphorylation by mass spectrometry (MS)-based proteomics remains challenging, due to the low occurrence of this post-translational modification compared to serine and threonine phosphorylation events in mammalian systems. Conventional metal-based affinity chromatography methods used to enrich phosphopeptides can nowadays isolate over 10,000 phosphopeptides. However, these approaches are not particularly suitable for the selective enrichment of low abundant Tyr phosphorylated peptides as the higher abundant co-enriched serine (Ser) and threonine (Thr) phosphorylated peptides typically obscure their detection. Therefore, a more targeted approach based on immuno-affinity precipitation at the peptide level has been introduced for the specific analysis of Tyr phosphorylated species. This method typically leads to the detection of a few hundreds of phosphopeptides, albeit typically over 70% of those are Tyr phosphorylated. Here, we evaluated and compared phosphotyrosine peptides enriched by a phospho-Tyr immuno-affinity enrichment (employing pY99 antibodies) and a multidimensional approach consisting of metal-affinity based enrichment (Ti(4+)-IMAC) followed by hydrophilic interaction liquid chromatography (HILIC) fractionation. Our aim was to assess differences and similarities in the set of Tyr phosphorylated peptides detected by each approach. Our data suggest that both strategies are not redundant but complementary and should ideally be combined for a more comprehensive view at phosphotyrosine signaling. Here we evaluated enabling tools for the global analysis of phosphotyrosine phosphorylation. Phosphotyrosine phosphorylation is a key protein modification driving cellular response also involved in disease/cancer molecular pathways.

Evaluation of a novel, commercially available mass spectrometry kit for newborn screening including succinylacetone without hydrazine

Newborn screening for tyrosinemia type I (Tyr-I) is mandatory to identify infants at risk before life-threatening symptoms occur. The analysis of tyrosine alone is limited, and might lead to false-negative results. Consequently, the analysis of succinylacetone (SUAC) is needed. Current protocols are time-consuming, and above all, include hazardous reagents such hydrazine. We evaluated a novel, commercial kit to analyze amino acids, acylcarnitines and SUAC with a significantly less harmful hydrazine derivative in a newborn screening laboratory. Dried blood spot specimens from 4683 newborns and samples from known patients with inborn errors of metabolism (IEM) were analyzed by a novel protocol and compared to an in-house screening assay. All samples were derivatized with butanol–HCl after extraction from 1/8-inch DBS punches. For the novel protocol, the residual blood spots were extracted separately for SUAC, converted into hydrazone, combined with amino acids and acylcarnitines, and subsequently analyzed by mass spectrometry using internal isotope-labeled standards. All newborns were successfully tested, and 74 patients with IEMs including three with Tyr-I (SUAC 1.50, 4.80 and 6.49; tyrosine levels 93.10, 172.40 and 317.73, respectively) were detected accurately. The mean SUAC level in non-affected newborns was 0.68μmol/l (cut-off 1.29μmol/l). The novel assay was demonstrated to be accurate in the detection of newborns with IEM, robust, and above all, without the risk of the exposure to highly toxic reagents and requirement of additional equipment for toxic fume evacuation.

Abstract 2908: Multiparameter FACS analysis of Stat3 and Stat5 signaling in pediatric AML samples

Abstract Pediatric acute myeloid leukemia (AML) is a devastating disease with a relapse rate near 50%. New targeted therapies are entering clinical use, yet the pathways affected by these drugs remain poorly understood. Aberrantly active Stat3 and Stat5 are found in AML and have been associated with chemoresistant disease, likely due to increased pro-survival gene expression. Our hypothesis is that analysis of Stat3/5 activation, and expression levels of key proteins in the pathways, will provide insight into mechanisms of aberrant signaling, and will guide the development of targeted therapies. We performed multiparameter FACS analysis of tyrosine- and serine-phosphorylated Stat3 (pY- and pS-Stat3; n=65) and pY-Stat5 (n=47) in pediatric AML samples from the Children's Oncology Group. Constitutive activation was common and quite variable (median pY-Stat3+ events/sample: 38%, range: 3 – 82%; median pY-Stat5+: 34%, range: 5.9 – 77%). There was non-significant correlation between %pY-Stat3+ and %pY-Stat5+ events in unstimulated samples. Constitutive pS-Stat3 was rare (median 2%). As expected, there was a significant correlation between constitutive %pY-Stat3+ and total Stat3 expression (by MFI), with linear correlation coefficient R=0.411 (p<0.001). Most samples were not responsive to G-CSF or IL-6; 38/65 (58%) failed to show at least a 2-fold increase in the pY-Stat3 MFI after treatment with G-CSF (100 ng/ml), and 42/65 (65%) did not respond to IL-6 (50 ng/ml IL-6 + 100 ng/ml soluble IL-6 receptor (sIL6R)). A pY-Stat3 response to only this high dose of G-CSF was seen in 23% of samples, while 15% responded to 10 ng/ml, and only 1 sample responded to 1 ng/ml G-CSF. The patterns of pY-Stat5 responses to G-CSF and of pY-Stat3 responses to IL-6 were similar. The pY-Stat3 and pY-Stat5 responses to G-CSF, as well as the pY-Stat3 responses to G-CSF and to IL-6, were significantly correlated (R=0.911, p<0.001 and R=0.431, p<0.001, respectively), suggesting overlap of these signaling pathways. Surface G-CSFR expression positively correlated with the GCSF-induced pY-Stat3 response (R=0.333, p=0.005). Interestingly, surface gp130 expression negatively correlated with the IL6-induced response (R=−0.349, p<0.005), meaning samples with robust IL-6 responses tended to have fewer gp130+ cells. Expression of the negative regulators SOCS3 and Shp1 were measured by Western blot (n=46) and normalized to the AML cell line Kasumi-1. SOCS3 expression in primary samples was consistently low, whereas Shp1 expression was up to 26-fold higher in primary samples compared to Kasumi-1 cells. Neither SOCS3 nor Shp1 levels varied in proportion to basal pY-Stat3. In summary, multiparameter FACS analysis of baseline and ligand-induced Stat3 and Stat5 activity provides biologic insight into signaling aberrancies in AML, and this knowledge will promote rational design and testing of new therapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2908. doi:10.1158/1538-7445.AM2011-2908

Analysis of tyrosine- and methionine-containing neuropeptides by fast atom bombardment mass spectrometry

A simple and unambiguous method for the detection of the amino acids tyrosine and methionine in peptide structures has been developed. The procedure, which was applied in studies of opioid peptides, is based on continuous-flow fast atom bombardment mass spectrometry (CF-FAB-MS) following chemical modification of the residue to be analyzed. Thus, for the detection of tyrosine, modification reactions such as acetylation or non-radioactive iodination were performed prior to analysis by CF-FAB-MS. O-Acetylation of the tyrosine residue with N-acetylimidazole was accompanied by a shift of 42 Da in the molecular mass of the peptide under investigation. This modification was reversed by treatment with hydroxylamine hydrochloride. Incorporation of iodine resulted in a molecular weight shift of 126 Da per iodine atom. Methionine residues were detected in methionine-enkephalin-containing peptides following S-oxidation with hydrogen peroxide. The procedures described may have a wide application in peptide chemistry, particularly for the identification of peptide fragments containing the above residues, e.g. in studies of processing or degradation of the enkephalins or other neuropeptides ( e.g. endorphins and tachykinins).

A rapid quantitative analysis of tyrosine and its oxidation products by tyrosinase.

A new technique based on liquid phase ion exchange chromatography on short column is proposed for quantitative determination of tyrosine and Dopa. alpha-Amino,beta-guanidinopropionic acid is used as an internal standard of coloration. The role of H2O2 and ascorbic acid on tyrosine and Dopa was checked. Ascorbic acid prevents the auto-oxidation of Dopa, H2O2 has no effect on tyrosine but oxidizes Dopa even in the presence of excess ascorbic acid. This method was tested in mushroom tyrosinase, with and without ascorbic acid. Assays performed with tyrosinase from rabbit ocular extracts clearly showed that they do oxidize tyrosine. Reliability of the method is comparable to radioassay.

Tyrosyl transfer ribonucleic acid synthetase from Escherichia coli B. Analysis of tyrosine and adenosine 5'-triphosphate binding sites.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTyrosyl transfer ribonucleic acid synthetase from Escherichia coli B. Analysis of tyrosine and adenosine 5'-triphosphate binding sitesDaniel V. Santi and Van A. PenaCite this: J. Med. Chem. 1973, 16, 3, 273–280Publication Date (Print):March 1, 1973Publication History Published online1 May 2002Published inissue 1 March 1973https://doi.org/10.1021/jm00261a025RIGHTS & PERMISSIONSArticle Views155Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts