Key bacterial taxa determine longitudinal dynamics of aromatic amino acid catabolism in infants' gut.

The development of the gut microbiota in early life is linked to metabolic, neuronal, and immunological development. Recent studies have shown that bacterial production of short-chain fatty acids (SCFAs) and aromatic amino acid (AAA) catabolites in the gut can mediate host-microbe interactions. However, the dynamics of these microbiota-derived metabolites and the key bacterial taxa producing AAA catabolites during infancy are largely unknown. Here, we investigated the longitudinal dynamics of the microbiota and microbiota-derived SCFAs and AAA catabolites in more than 200 fecal samples from 25 healthy breast- or mixed-fed Danish infants during the first 6 months of life. We found that the gut microbiota composition and metabolism were highly individual but showed significant development over time. SCFAs and specific groups of AAA catabolites showed distinct temporal abundance patterns. Furthermore, we identified bacterial taxa responsible for the generation of AAA catabolites by associating the dynamics of gut microbial taxa and AAA catabolites and subsequently validating these associations in vitro by cultivation of strains representing the associated taxa. In addition to specific Bifidobacterium species being the main producers of aromatic lactic acids, we identified Peptostreptococcus anaerobius as the main producer of aromatic propionic acids, Ruminococcus gnavus as a main producer of tryptamine, and Enterococcus species as main tyramine producers in infants' gut. Thus, our results showcase the temporal dynamics of key gut microbial metabolites in early life and demonstrate that the appearance and abundance of specific AAA catabolites result from the appearance and abundance of specific key bacterial taxa in infants' gut.

Evaluation of aromatic amino acids as potential biomarkers in breast cancer by Raman spectroscopy analysis.

The scope of the work undertaken in this paper was to explore the feasibility and reliability of using the Raman signature of aromatic amino acids as a marker in the detection of the presence of breast cancer and perhaps, even the prediction of cancer development in very early stages of cancer onset. To be able to assess this hypothesis, we collected most recent and relevant literature in which Raman spectroscopy was used as an analytical tool in the evaluation of breast cell lines and breast tissue, re-analyzed all the Raman spectra, and extracted all spectral bands from each spectrum that were indicative of aromatic amino acids. The criteria for the consideration of the various papers for this study, and hence, the inclusion of the data that they contained were two-fold: (1) The papers had to focus on the characterization of breast tissue with Raman spectroscopy, and (2) the spectra provided within these papers included the spectral range of 500-1200 cm-1, which constitutes the characteristic region for aromatic amino acid vibrational modes. After all the papers that satisfied these criteria were collected, the relevant spectra from each paper were extracted, processed, normalized. All data were then plotted without bias in order to decide whether there is a pattern that can shed light on a possible diagnostic classification. Remarkably, we have been able to demonstrate that cancerous breast tissues and cells decidedly exhibit overexpression of aromatic amino acids and that the difference between the extent of their presence in cancerous cells and healthy cells is overwhelming. On the basis of this analysis, we conclude that it is possible to use the signature Raman bands of aromatic amino acids as a biomarker for the detection, evaluation and diagnosis of breast cancer.

Rapid simultaneous determination of gut microbial phenylalanine, tyrosine, and tryptophan metabolites in rat serum, urine, and faeces using LC-MS/MS and its application to a type 2 diabetes mellitus study.

Gut microbial phenylalanine, tyrosine, and tryptophan metabolites are closely linked to various diseases. Monitoring the alterations of the related metabolites is vital to facilitate the understanding of pathophysiology of diseases. Herein, a rapid and sensitive assay based on LC-tandem mass spectrometry has been developed to analyze 20 gut microbial metabolites derived from phenylalanine, tyrosine, and tryptophan in rat serum, urine, and faeces. These microbial-derived metabolites were separated on a phenyl-hexyl column and simultaneously determined in a single run of 8 min. The detection limit for analytes ranged between 1.08 and 32.4 ng/mL. All calibration curves exhibited good linear relationships (R2 ≥ 0.9982). Intra- and inter-assay precision values were below 15% and accuracies ranged from 85% to 115% for all analytes. The selectivity, matrix effect, and recovery of this method were all satisfactory. The validated method was successfully applied to characterize the alterations of these metabolites in type 2 diabetes mellitus rat. In general, the developed assay is suitable for high-throughput monitoring of gut microbial phenylalanine, tyrosine, and tryptophan metabolites and provides a useful approach for exploring the mechanisms of microbial-derived metabolites in diseases.

Branched-chain and aromatic amino acids and cardiometabolic risk in Black African and Asian Indian populations.

INTRODUCTION: Studies have shown that systemic levels of branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs) are elevated in cardiometabolic diseases (CMDs) in populations resident in high income countries. However, little is known about the association of BCAAs and AAAs with metabolic syndrome and its components in Asian Indian (AI) and Black African (BA) populations. OBJECTIVE: The aim of this study was to describe the association of BCAAs and AAAs with the metabolic syndrome, its individual components and insulin resistance in AI and BA populations. METHODS: Serum samples collected from AI (n = 349) and BA (n = 369) subjects were used to measure levels of BCAAs and AAAs by ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Anthropometric, demographic and cardiometabolic variables were measured in all subjects. RESULTS: The sum of BCAAs and AAAs was higher in AIs compared to BAs. The BCAAs and AAAs were positively associated with insulin resistance, metabolic syndrome and its individual components. This was particularly the case for AI subjects, in unadjusted regression models. However, these associations were non-significant after adjusting for co-variates, particularly visceral adipose tissue (VAT). Triglyceride levels were significantly associated with valine and leucine levels in BAs even after adjustment for co-variates. Lastly, we found that fasting circulatory BCAA and AAA levels are strongly correlated with VAT in both populations. CONCLUSION: This study identified specific associations of serum valine and leucine levels with triglycerides in BAs. The association of amino acids with CMDs was observed in AIs, but was found to be the result of confounding by VAT. Further studies are required to determine whether BCAAs and AAAs are aetiological factors in CMDs and how VAT modulates their serum levels.

Targeted Metabolomic Analysis of a Mucopolysaccharidosis IIIB Mouse Model Reveals an Imbalance of Branched-Chain Amino Acid and Fatty Acid Metabolism.

Mucopolysaccharidoses (MPSs) are inherited disorders of the glycosaminoglycan (GAG) metabolism. The defective digestion of GAGs within the intralysosomal compartment of affected patients leads to a broad spectrum of clinical manifestations ranging from cardiovascular disease to neurological impairment. The molecular mechanisms underlying the progression of the disease downstream of the genetic mutation of genes encoding for lysosomal enzymes still remain unclear. Here, we applied a targeted metabolomic approach to a mouse model of PS IIIB, using a platform dedicated to the diagnosis of inherited metabolic disorders, in order to identify amino acid and fatty acid metabolic pathway alterations or the manifestations of other metabolic phenotypes. Our analysis highlighted an increase in the levels of branched-chain amino acids (BCAAs: Val, Ile, and Leu), aromatic amino acids (Tyr and Phe), free carnitine, and acylcarnitines in the liver and heart tissues of MPS IIIB mice as compared to the wild type (WT). Moreover, Ala, Met, Glu, Gly, Arg, Orn, and Cit amino acids were also found upregulated in the liver of MPS IIIB mice. These findings show a specific impairment of the BCAA and fatty acid catabolism in the heart of MPS IIIB mice. In the liver of affected mice, the glucose-alanine cycle and urea cycle resulted in being altered alongside a deregulation of the BCAA metabolism. Thus, our data demonstrate that an accumulation of BCAAs occurs secondary to lysosomal GAG storage, in both the liver and the heart of MPS IIIB mice. Since BCAAs regulate the biogenesis of lysosomes and autophagy mechanisms through mTOR signaling, impacting on lipid metabolism, this condition might contribute to the progression of the MPS IIIB disease.

Visual chiral recognition of aromatic amino acids with (S)-mandelic acid-based ionic liquids via complexation.

Recently, chiral ionic liquids have attracted increasing attention in analytical chemistry. However, only a few papers focus on the application of them in visual chiral recognition. Herein, two functionalized chiral ionic liquids derived from (S)-mandelic acid (1-butyl-3-methylimidazolium mandelate, CIL1 and N-butyl-N-methylpyrrolidinium mandelate, CIL2) were prepared for visual chiral recognition of aromatic amino acids for the first time. In the presence of Cu(II) and appropriate solvents, visual enantiomeric responses of phenylalanine, tryptophane, tyrosine and phenylglycine were observed. Relying on solubility or color differences, all chiral recognition could be finished within 5 min. The potential mechanism was investigated by means of infrared spectroscopy, ultraviolet spectroscopy, thermal gravity analysis, elemental analysis and scanning electron microscope. Results revealed that CuSO4 interacted with CIL1 and D-tryptophane in the ratio of 1:1.96:0.43 in relevant precipitate, and the different stability of complex was responsible for the chiral recognition. In addition, resolution of racemic tryptophane was performed, which offered excellent enantiomeric excess values (94.2% for CIL1 and 95.1% for CIL2 in solid phase). The proposed ionic liquids had strong enantioselectivity for aromatic amino acids and great potential in visual chiral recognition.

An application of Nano Differential Scanning Fluorimetry for Higher Order Structure assessment between mAb originator and biosimilars: Trastuzumab and Rituximab as case studies.

Differential scanning fluorimetry (DSF) or thermal shift has emerged in recent years as a high-throughput screening method in biotherapeutic formulation studies. The present article reports on a fast-track assessment platform for rapid investigation of therapeutic proteins such as monoclonal antibodies (mAb) with minimal sample concentration, volume, and preparation. The proposed nanoDSF platform has been demonstrated for rapid assessment of two commercial IgG 1 drug products (DP), trastuzumab and rituximab, and their biosimilars with respect to their conformational and colloidal stability. Domain specific differences for each of the IgGs have been elucidated with respect to onset of domain unfolding (Tonset) and melting temperatures. These thermal unfolding and transition midpoint (Tm) measurements are based on the intrinsic aromatic amino acid residue fluorescence of proteins. Moreover, to understand the possibility of nanoDSF as a predictive tool, data from nanoDSF has been correlated with accelerated stability studies. Melting temperatures across brands were found to be highly comparable to the rate of heating, thereby exhibiting a significant domain specific effect on melting temperatures for both trastuzumab and rituximab. Conservation of higher order structure (HOS) through reversible unfolding was also examined and both the mAbs were found to regain tertiary structure up till the first transition midpoint. No clear correlation was found between formation of higher molecular weight species (HMWS) and unfolding parameters (Tonset and Tagg) for accelerated stability studies. Finally, a discussion on the need for fast predictive assessment of conformation and colloidal stability as well as a comparison of advantages and limitations of the technique with routine/classical tools such as circular dichroism spectrophotometry and differential scanning calorimetry has been presented.

Raman Analysis Reveals Biochemical Differences in Plasma of Crohn's Disease Patients.

BACKGROUNDS AND AIMS: There is no accurate and reliable circulating biomarker to diagnose Crohn's disease [CD]. Raman spectroscopy is a relatively new approach that provides information on the biochemical composition of samples in minutes and virtually without any sample preparation. We aimed to test the use of Raman spectroscopy analysis of plasma samples as a potential diagnostic tool for CD. METHODS: We analysed by Raman spectroscopy dry plasma samples obtained from 77 CD patients [CD] and 45 healthy controls [HC]. In the dataset obtained, we analysed spectra differences between CD and HC, as well as among CD patients with different disease behaviours. We also developed a method, based on principal component analysis followed by a linear discrimination analysis [PCA-LDA], for the automatic classification of individuals based on plasma spectra analysis. RESULTS: Compared with HC, the CD spectra were characterised by less intense peaks corresponding to carotenoids [p <10-4] and by more intense peaks corresponding to proteins with ß-sheet secondary structure [p <10-4]. Differences were also found on Raman peaks relative to lipids [p = 0.0007] and aromatic amino acids [p <10-4]. The predictive model we developed was able to classify CD and HC subjects with 83.6% accuracy [sensitivity 80.0% and specificity 85.7%] and F1-score of 86.8%. CONCLUSIONS: Our results indicate that Raman spectroscopy of blood plasma can identify metabolic variations associated with CD and it could be a rapid pre-screening tool to use before further specific evaluation.

An Approach for In Situ Rapid Detection of Deep-Sea Aromatic Amino Acids Using Laser-Induced Fluorescence.

Amino acids are the material basis of almost all life activities. An improved understanding of the source, state, and cycle of amino acids is essential for determining the energy flow and material circulation of marine ecosystems. In the present study, an in situ rapid detection method of ultraviolet (UV; 266 nm) laser-induced fluorescence (LIF) technology was used to detect three natural, aromatic amino acids in the seawater. The laser-induced fluorescence peaks of aromatic amino acids tryptophan, tyrosine, and phenylalanine were located at 350 nm, 300 nm, and 280 nm, respectively. High, linear correlations between the concentrations of the aromatic amino acids and the fluorescence peak heights were observed, and the lowest detectable concentrations of tryptophan, tyrosine, and phenylalanine were 4.70 × 10-9 mol/L, 2.76 × 10-8 mol/L, and 6.05 × 10-7 mol/L, respectively, which allowed us to quantify their concentrations by using laser-induced fluorescence. This paper not only provides a practical method for the detection of aromatic amino acids in seawater, but a new means to further understand the biogeochemical processes of carbon cycles in the deep sea.

Phylogenetic and structural diversity of aromatically dense pili from environmental metagenomes.

Electroactive type IV pili, or e-pili, are used by some microbial species for extracellular electron transfer. Recent studies suggest that e-pili may be more phylogenetically and structurally diverse than previously assumed. Here, we used updated aromatic density thresholds (≥9.8% aromatic amino acids, ≤22-aa aromatic gaps and aromatic amino acids at residues 1, 24, 27, 50 and/or 51, and 32 and/or 57) to search for putative e-pilin genes in metagenomes from diverse ecosystems with active microbial metal cycling. Environmental putative e-pilins were diverse in length and phylogeny, and included truncated e-pilins in Geobacter spp., as well as longer putative e-pilins in Fe(II)-oxidizing Betaproteobacteria and Zetaproteobacteria.

Physiological performance of glyphosate and imazamox mixtures on Amaranthus palmeri sensitive and resistant to glyphosate.

The herbicides glyphosate and imazamox inhibit the biosynthetic pathway of aromatic amino acids (AAA) and branched-chain amino acids (BCAA), respectively. Both herbicides share several physiological effects in the processes triggered in plants after herbicide application that kills the plant, and mixtures of both herbicides are being used. The aim of this study was to evaluate the physiological effects in the mixture of glyphosate and imazamox in glyphosate-sensitive (GS) and -resistant (GR) populations of the troublesome weed Amaranthus palmeri. The changes detected in the physiological parameters after herbicide mixtures application were similar and even less to the changes detected after individual treatments. This pattern was detected in shikimate, amino acid and carbohydrate content, and it was independent of the EPSPS copy number, as it was detected in both populations. In the case of the transcriptional pattern of the AAA pathway after glyphosate, interesting and contrary interactions with imazamox treatment were detected for both populations; enhancement of the effect in the GS population and alleviation in the GR population. At the transcriptional level, no cross regulation between AAA and BCAA inhibitors was confirmed. This study suggests that mixtures are equally or less toxic than herbicides alone, and would implicate careful considerations when applying the herbicide mixtures.

The Parallel Factor Analysis of Beer Fluorescence.

Fluorescence excitation-emission matrices were measured for 111 samples of different types of beer and studied by the parallel factor analysis (PARAFAC). The 5-component PARAFAC model was found to suitably describes the beer fluorescence, accounting for 99.4% of the fluorescence variance in the measured set of samples, and providing the completely resolved excitation and emission spectra of each component. The model was chosen based on a model's core consistency and split-half analysis. It is shown that beer fluorescence is the sum of fluorescence of aromatic amino acids (tryptophan, tyrosine, and phenylalanine), different forms of vitamin B, and phenolic compounds. Obtained PARAFAC model of beer fluorescence demonstrated the potential for the quantification and quality analysis of beer fluorophores and classification of different beer types.

Tyrosine Induced Metabolome Alterations of Penicillium roqueforti and Quantitation of Secondary Key Metabolites in Blue-Mold Cheese.

To map qualitative and quantitative metabolome alterations when Penicillium roqueforti is grown in an environment where l-tyrosine levels are perturbed, the recently established differential off-line LC-NMR (DOLC-NMR) approach was successfully applied in connection with an absolute metabolite quantitation using a quantitative 1H NMR protocol following the ERETIC 2 (Electronic REference To access In vivo Concentrations) methodology. Among the 23 influenced metabolites, amino acid degradation products like 2-(4-hydroxyphenyl)acetic acid and 2-(3,4-dihydroxyphenyl)acetic acid underwent a tremendous upregulation in the amino acid perturbed approach. Moreover, the output of secondary metabolites like andrastin A, eremofortin B, and the tetrapeptide d-Phe-l-Val-d-Val-l-Tyr was affected in the case of the presence or absence of the added aromatic amino acid. Furthermore, the isolated secondary metabolites of P. roqueforti have been quantified for the first time in five divergent Penicillium isolates by means of a validated LC-ECHO-MS/MS method. This technique is used to compensate the effect of co-extracted matrix compounds during the analysis and to utilize quasi-internal standards to quantify all metabolites of interest accurately. This screening outlined the great variety between the different fungi of the same species. The metabolite spectra of wild-type fungi included more toxic intermediates compared to a selected fungi used as a starter culture for blue-mold cheese production. In addition, these secondary metabolites were quantified in commercially available white- and blue-mold cheese samples. The main differences between the analyte profiles of white and blue cheeses were linked to the impact of the used starter culture. Specific metabolites detected from P. roqueforti like andrastin A and B or roquefortine C could not be detected in white cheese. Among the blue cheese samples, different metabolite pattern could be observed regarding various P. roqueforti starter cultures.

Efficient function of signal peptidase 1 of Escherichia coli is partly determined by residues in the mature N-terminus of exported proteins.

Exported proteins require an N-terminal signal peptide to direct them from the cytoplasm to the periplasm. Once the protein has been translocated across the cytoplasmic membrane, the signal peptide is cleaved by a signal peptidase, allowing the remainder of the protein to fold into its mature state in the periplasm. Signal peptidase I (LepB) cleaves non-lipoproteins and recognises the sequence Ala-X-Ala. Amino acids present at the N-terminus of mature, exported proteins have been shown to affect the efficiency at which the protein is exported. Here we investigated a bias against aromatic amino acids at the second position in the mature protein (P2'). Maltose binding protein (MBP) was mutated to introduce aromatic amino acids (tryptophan, tyrosine and phenylalanine) at P2'. All mutants with aromatic amino acids at P2' were exported less efficiently as indicated by a slight increase in precursor protein in vivo. Binding of LepB to peptides that encompass the MBP cleavage site were analysed using surface plasmon resonance. These studies showed peptides with an aromatic amino acid at P2' had a slower off rate, due to a significantly higher binding affinity for LepB. These data are consistent with the accumulation of small amounts of preMBP in purified protein samples. Hence, the reason for the lack of aromatic amino acids at P2' in E. coli is likely due to interference with efficient LepB activity. These data and previous bioinformatics strongly suggest that aromatic amino acids are not preferred at P2' and this should be incorporated into signal peptide prediction algorithms.

Biological synthesis of high-conductive pili in aerobic bacterium Pseudomonas aeruginosa.

Bioelectrical nanowires as ecomaterials have great potential on environmental applications. A wide range of bacteria can express type IV pili (T4P), which are long protein fibers assembled from PilA. The T4P of Geobacter sulfurreducens are well known as "microbial nanowires," yet T4P of Pseudomonas aeruginosa (PaT4P) was believed to be poorly conductive. P. aeruginosa is an aerobic and electrochemically active bacterium. Its T4P have been known to be responsible for surface attachment, twitching motility and biofilm formation. Here, we show that PaT4P can be highly conductive while assembled by a truncated P. aeruginosa PilA (PaPilA) containing only N-terminus 61 amino acids. Furthermore, increasing the number of aromatic amino acids in the PaPilA1-61 significantly enhances the conductivity of pili and the bioelectricity output of P. aeruginosa in microbial fuel cell system, suggesting a potential application of PaT4P as a conductive nanomaterial. The N-terminal region of PilA from diverse eubacteria is highly conserved, implying a general way to synthesize highly conductive microbial nanowires and to increase the bioelectricity output of microbial fuel cell.

Au Nanoparticles Deposited on Magnetic Carbon Nanofibers as the Ultrahigh Sensitive Substrate for Surface-Enhanced Raman Scattering: Detections of Rhodamine 6G and Aromatic Amino Acids.

Surface-enhanced Raman scattering (SERS) is a unique spectroscopy that can offer high-sensitive detection for many molecules. Herein, the Au particles deposited on carbon nanofiber-encapsulated magnetic Ni nanoparticles (NPs) (Ni@CNFs@Au) have been successfully synthesized for SERS measurements. The Ni@CNFs@Au substrates have the advantages of a high SERS sensitivity and good magnetic response. The Ni@CNFs could be directly obtained from CO2 hydrogenation on a Ni catalyst, which has been characterized as having rich carboxylic acid groups, graphitic structures, and a high surface area. The Ni@CNFs surface could effectively increase the density of hotspots during Au NP aggregation and influence the morphology of the Au nanostructures. The spherical shape, oval shape, and coral-like Au nanostructures were prepared on Ni@CNFs with various Au concentrations. Brunauer-Emmett-Teller, zeta potential, high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy measurements were used to characterize the Ni@CNFs@Au samples. The Au NPs deposited on the Ni@CNFs presented a suitable oval shape, and an average size of ∼30-40 nm. The size allowed surprisingly ultrasensitive SERS detection of rhodamine 6G (R6G) with a resolution of approximately a single molecule under an excitation wavelength of 532 nm. Using 785 nm excitation, a low R6G concentration of ∼1 × 10-14 M was detected. Moreover, the Ni@CNFs@Au substrates could be rapidly magnetically separated after adsorption. Phenylalanine and tyrosine amino acids, which are associated with the liver disease, were examined using SERS with the Ni@CNFs@Au substrate. Ultralow concentrations of ∼1 × 10-11 M for phenylalanine and ∼1 × 10-13 M for tyrosine were clearly measured. The Ni@CNFs@Au substrates exhibited applicability as excellent SERS detection platforms that combine high-sensitivity and rapid magnetic separation for various adsorption molecules.

Detecting Nonvolatile Life- and Nonlife-Derived Organics in a Carbonaceous Chondrite Analogue with a New Multiplex Immunoassay and Its Relevance for Planetary Exploration.

Potential martian molecular targets include those supplied by meteoritic carbonaceous chondrites such as amino acids and polycyclic aromatic hydrocarbons and true biomarkers stemming from any hypothetical martian biota (organic architectures that can be directly related to once living organisms). Heat extraction and pyrolysis-based methods currently used in planetary exploration are highly aggressive and very often modify the target molecules making their identification a cumbersome task. We have developed and validated a mild, nondestructive, multiplex inhibitory microarray immunoassay and demonstrated its implementation in the SOLID (Signs of Life Detector) instrument for simultaneous detection of several nonvolatile life- and nonlife-derived organic molecules relevant in planetary exploration and environmental monitoring. By utilizing a set of highly specific antibodies that recognize D- or L- aromatic amino acids (Phe, Tyr, Trp), benzo[a]pyrene (B[a]P), pentachlorophenol, and sulfone-containing aromatic compounds, respectively, the assay was validated in the SOLID instrument for the analysis of carbon-rich samples used as analogues of the organic material in carbonaceous chondrites or even Mars samples. Most of the antibodies enabled sensitivities at the 1-10 ppb level and some even at the ppt level. The multiplex immunoassay allowed the detection of B[a]P as well as aromatic sulfones in a water/methanol extract of an Early Cretaceous lignite sample (c.a., 140 Ma) representing type IV kerogen. No L- or D-aromatic amino acids were detected, reflecting the advanced diagenetic stage and the fossil nature of the sample. The results demonstrate the ability of the liquid extraction by ultrasonication and the versatility of the multiplex inhibitory immunoassays in the SOLID instrument to discriminate between organic matter derived from life and nonlife processes, an essential step toward life detection outside Earth.

Optical Sensing of Aromatic Amino Acids and Dipeptides by a Crown-Ether-Functionalized Perylene Bisimide Fluorophore.

The host-guest binding properties of a fluorescent perylene bisimide (PBI) receptor equipped with crown ether were studied in detail with a series of aromatic amino acids and dipeptides by UV/Vis, fluorescence and NMR spectroscopy. Fluorescence titration experiments showed that electron-rich aromatic amino acids and dipeptides strongly quench the fluorescence of the electron-poor PBI host molecule. Benesi-Hildebrand plots of fluorescence titration data confirmed the formation of host-guest complexes with 1:2 stoichiometry. Binding constants determined by global analysis of UV/Vis and fluorescence titration experiments revealed values between 103 m-1 and 105 m-1 in acetonitrile/methanol (9:1) at 23 °C. These data showed that amino acid l-Trp having an indole group and dipeptides containing this amino acid bind to the PBI receptor more strongly than other amino acids and dipeptides investigated here. For dipeptides containing l-Trp or l-Tyr, the binding strength is dependent on the distance between the ammonium group and the aromatic unit of the amino acids and dipeptides leading to a strong sensitivity for Ala-Trp dipeptide. 1D and 2D NMR experiments also corroborated 1:2 host-guest complexation and indicated formation of two diastereomeric species of host-guest complexes. The studies have shown that a properly functionalized PBI fluorophore functions as a molecular probe for the optical sensing of aromatic amino acids and dipeptides.

Association between NAT2, CYP1A1, and CYP1A2 genotypes, heterocyclic aromatic amines, and prostate cancer risk: a case control study in Japan.

BACKGROUND: Heterocyclic aromatic amines (HAAs) may confer prostate cancer risk; however, the evidence is inconclusive and the activity of HAA-metabolizing enzymes is modulated by gene variants. The purpose of our study was to determine whether there was evidence of an association between HAA intake, polymorphisms in NAT2, CYP1A1, and CYP1A2 and prostate cancer risk in Japanese men. METHODS: Secondary data analysis of an observational case control study was performed. Among 750 patients with prostate cancer and 870 healthy controls, 351 cases and 351 age-matched controls were enrolled for analysis. HAA intake was estimated using a food frequency questionnaire and genotypes were scored by TaqMan real-time PCR assay. Logistic regression analysis was conducted according to affected/control status. RESULTS: We found that high HAA intake was significantly associated with an increased risk of prostate cancer (odds ratio (OR), 1.90; 95% confidence interval (95% CI), 1.40-2.59). The increased risk of prostate cancer was observed among individuals with the NAT2 slow acetylator phenotype (OR, 1.65; 95% CI, 1.04-2.61), CYP1A1 GA + GG genotype (OR, 1.27; 95% CI, 1.02-1.59), and CYP1A2 CA + AA genotype (OR, 1.43; 95% CI, 1.03-2.00). In addition, CYP1A1 GA + GG genotypes were associated with increased cancer risk in low (OR, 2.05; 95% CI, 1.19-3.63), moderate (OR, 1.72; 95% CI, 1.07-2.76), and high (OR, 2.86; 95% CI, 1.83-4.47) HAA intake groups. CONCLUSIONS: Our results suggest that high HAA intake is a risk factor of prostate cancer, and genotypes related to HAA metabolic enzymes can modulate the degree of the risk.

Selective determination of aromatic amino acids by magnetic hydroxylated MWCNTs and MOFs based composite.

A novel magnetic solid-phase extraction (MSPE) based method was established for aromatic amino acids (AAAs) selective determination. Central to the method was the adopted extractant. An explored composite of metal organic frameworks (MOFs) and magnetic carbon nanotubes (CNTs) was employed for that, which exhibited superior adsorption affinity and selectivity to AAAs as compared to other amino acids with the mechanisms attributed to multiple hydrogen bonding and π-π electron-donor-acceptor (EDA) interactions. The morphology, structure and magnetic behavior of the composite were characterized and related MSPE procedure was established. Critical extraction conditions including pH, extraction time, temperature and salt addition were investigated and optimized. Subsequently the concentrations of three AAAs tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) in Lanzhou lily were determined by the composite based MSPE procedure coupled with high performance liquid chromatography-ultraviolet detection (HPLC-UV). The composite provided a superior sample clean-up function and many of the matrix interferences were eliminated, thus ensured AAAs were accurately and efficiently determined. The results showed that the method had good linearities with the linear coefficients above 0.99, desirable recoveries ranged from 88.0% to 96.8% with the RSD less than 5.1%, satisfactory precision and low limits of detection (LODs) which were respectively 0.04, 0.11, and 0.87ng/g for Trp, Tyr and Phe. The composite based MSPE-HPLC-UV method has great potentials for the AAAs selective determination from complex matrix samples.