Suchergebnisse

The formation of 2-phenylethylamine and phenylacetaldehyde in mixtures of phenylalanine, a lipid oxidation product, and a second amino acid was studied to determine the role of the second amino acid in the degradation of phenylalanine produced by lipid-derived reactive carbonyls. The presence of the second amino acid usually increased the formation of the amine and reduced the formation of the Strecker aldehyde. The reasons for this behaviour seem to be related to the α-amino group and the other functional groups (mainly amino or similar groups) present in the side-chain of the amino acid. These groups are suggested to modify the lipid-derived reactive carbonyl but not the reaction mechanism because the E of formation of both 2-phenylethylamine and phenylacetaldehyde remained unchanged in all studied systems. All these results suggest that the amine/aldehyde ratio obtained by amino acid degradation can be modified by adding free amino acids during food formulation. ; We are indebted to José L. Navarro for technical assistance. This study was supported in part by the European Union (FEDER funds) and the Plan Nacional de I + D of the Ministerio de Economía y Competitividad of Spain (projects AGL2012-35627 and AGL2015-68186-R). ; Peer Reviewed

D-amino acid oxidase (DAAO) plays an important role in the functioning of
both prokaryotes and eukaryotes. DAAO is increasingly being used in practice, including
for the determination of D-amino acids in complex samples, including human tissues
and fl uids. There are generally two types of DAAO in all organisms. The fi rst type is
an enzyme highly specifi c for D-aspartate and has its own name D-aspartate oxidase
(DASPO). DAAO of the second type is characterized by a wide spectrum of substrate
specificity, with preference for one or another D-amino acid varying from source to
source. The activity of DAAO with a large number of substrates greatly complicates the
selective determination of a particular D-amino acid. The problem is often solved by
choosing an enzyme that, under the conditions of analysis, has low or no activity with
other D-amino acids present in the sample. For the convenience of selecting a particular
enzyme, we have collected and analyzed literature data on the catalytic parameters
of known DAAOs with the most important D-amino acids. In addition, similar data
are presented for novel recombinant DAAOs from the methylotrophic yeast Ogataea
parapolymorpha DL-1. Analysis of the data shows that, with the D-amino acid series,
the new OpaDASPO and OpaDAAO have the highest catalytic parameters.

The aim of this study was to assess the bromatological quality and the content of essential amino acids in maize grains produced using two different cropping systems: organic and conventional. The experimental area was 4 hectares, divided into 2 hectares per system. In the conventional management, agrochemicals from conventional maize production were used. In the organic management, inputs permitted by the current Brazilian legislation on organic production were used. For each system, 10 plots of 9 m² each were established, from which experimental samples were harvested. The method described by Silva & Queiroz (2002) was used to determine bromatological quality. Near-infrared reflectance spectroscopy (NIRS) was used to quantify essential amino acids. A significant difference was found in the bromatological quality of maize grains. The conventional management provided greater crude protein content. Significant changes were also found in the following amino acids: methionine, threonine, arginine, isoleucine, leucine, valine, histidine, and phenylalanine, which showed lower levels in the organic management. The results confirm the need to determine food composition before diet formulation, since using preestablished food compositions probably leads to differences between what was formulated and what was actually given to poultry. The type of management influenced the quality of maize grains. The management of plant nutrition in the organic system should be refined to adequately supply nitrogen, thus improving bromatological and amino acid quality of the grains.

Nomenclature of Amino Acids -- The Protein Amino Acids -- Beta and Higher Homologous Amino Acids -- The Non-Protein Amino Acids -- Metabolic and Pharmacological Studies -- The Biosynthesis of Amino Acids in Plants -- Enzyme Inhibition by Amino Acids and their Derivatives -- Synthesis of Amino Acids -- Protected Amino Acids in Peptide Synthesis -- Resolution of Amino Acids -- Reactions of Amino Acids -- Degradation of Amino Acids Accompanying in vitro Protein Hydrolysis -- Racemization of Amino Acids -- Ion-Exchange Separation of Amino Acids -- Liquid Chromatography of Amino Acids and their Derivatives -- Gas-Liquid Chromatographic Separation of Amino Acids and their Derivatives -- Mass Spectrometry of Amino Acids and their Derivatives -- Nuclear Magnetic Resonance Spectra of Amino Acids and their Derivatives -- The Optical Rotatory Dispersion and Circular Dichroism of Amino Acids and their Derivatives -- Colorimetric and Fluorimetric Detection of Amino Acids -- Physical Properties of Amino Acid Solutions -- X-Ray Crystal Structures of Amino Acids and Selected Derivatives.

The photooxygenation of model compounds containing the two enantiomers of naproxen (NPX) covalently linked to histidine (His), tryptophan (Trp) and tyrosine (Tyr) has been investigated by steady state irradiation, fluorescence spectroscopy and laser flash photolysis. The NPX–His systems presented the highest oxygen-mediated photoreactivity. Their fluorescence spectra matched that of isolated NPX and showed a clear quenching by oxygen, leading to a diminished production of the NPX triplet excited state ( 3 NPX*–His). Analysis of the NPX–His and NPX–Trp photolysates by UPLC-MS–MS revealed in both cases the formation of two photoproducts, arising from the reaction of singlet oxygen (1 O2) with the amino acid moiety. The most remarkable feature of NPX–Trp systems was a fast and stereoselective intramolecular fluorescence quenching, which prevented the efficient formation of 3 NPX*–Trp, thus explaining their lower reactivity towards photooxygenation. Finally, the NPX–Tyr systems were nearly unreactive and exhibited photophysical properties essentially coincident with those of the parent NPX. Overall, these results point to a type II photooxygenation mechanism, triggered by generation of 1 O2 from the 3 NPX* chromophore ; Financial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, Miguel Servet CP11/00154), from the EU (PCIG12-GA-2012-334257), from the Universitat Politecnica de Valencia (SP20120757) and from the Conselleria de Educacio, cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged. ; Vayá Pérez, I.; Andreu Ros, MI.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photooxygenation mechanisms in naproxen-amino acid linked systems. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 13:224-230. https://doi.org/10.1039/c3pp50252j ; S ; 224 ; 230 ; 13 ; L. I. Grossweiner and K. C.Smith, Photochemistry, in The Science of Photobiology, ed. K. C. Smith, Plenum Press, New York, 2nd edn, 1989, pp. 47–78 ; L. Pretali and A.Albini, in CRC ...

Department of Chemistry, Muragachha Government College, University of Kalyani, Nadia-741 235, West Bengal, India E-mail: rajibsarkar.org@gmail.com Manuscript received 16 July 2018, accepted 27 August 2018 A tripeptide, Boc-(L)-Leu(1)-Aib(2)-(L)-Leu(3)-OMe, 1 containing a-aminoisobutyric acid and a coded amino acid was synthe­sized and fully characterized. Then, conformational preference of the tripeptide was studied. The highly hydrophobic peptide adopts bend conformation like a helix. But there is no intramolecular hydrogen bonded regular β or -y turn. The X-ray crystal­lography of the tripeptide shows that the peptide has a helical conformation with consecutive five members N-H.N hydro­gen bonded turn. The single amino acid chain inverter forms a 2→1 N-H.N hydrogen bonds and helical structure which are rare element of proteins.

An ability to sense and respond to nutrient availability is an important requisite for life.Nutrient limitation is among main factors to influence the evolution of most cellular processes.Different pathways that sense intracellular and extracellular levels of carbohydtrates, amino acids,lipids, and intermediate metabolites are integrated and coordinated at the organismal levelthrough neuronal and humoral signals. During food abundance, nutrient-sensing pathwaysengage anabolism and storage, whereas limitation triggers the mechanisms, such as themobilization of internal stores including through autophagy. These processes are affected duringaging and are themselves important regulators of longevity, stress resistance, and age-relatedcomplications

224 230 13 ; S ; The photooxygenation of model compounds containing the two enantiomers of naproxen (NPX) covalently linked to histidine (His), tryptophan (Trp) and tyrosine (Tyr) has been investigated by steady state irradiation, fluorescence spectroscopy and laser flash photolysis. The NPX–His systems presented the highest oxygen-mediated photoreactivity. Their fluorescence spectra matched that of isolated NPX and showed a clear quenching by oxygen, leading to a diminished production of the NPX triplet excited state ( 3 NPX*–His). Analysis of the NPX–His and NPX–Trp photolysates by UPLC-MS–MS revealed in both cases the formation of two photoproducts, arising from the reaction of singlet oxygen (1 O2) with the amino acid moiety. The most remarkable feature of NPX–Trp systems was a fast and stereoselective intramolecular fluorescence quenching, which prevented the efficient formation of 3 NPX*–Trp, thus explaining their lower reactivity towards photooxygenation. Finally, the NPX–Tyr systems were nearly unreactive and exhibited photophysical properties essentially coincident with those of the parent NPX. Overall, these results point to a type II photooxygenation mechanism, triggered by generation of 1 O2 from the 3 NPX* chromophore Financial support from the Spanish Government (CTQ2010-14882, JCI-2011-09926, Miguel Servet CP11/00154), from the EU (PCIG12-GA-2012-334257), from the Universitat Politecnica de Valencia (SP20120757) and from the Conselleria de Educacio, cultura i Esport (PROMETEOII/2013/005, GV/2013/051) is gratefully acknowledged. Vayá Pérez, I.; Andreu Ros, MI.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2014). Photooxygenation mechanisms in naproxen-amino acid linked systems. Photochemical & Photobiological Sciences Photochemical and Photobiological Sciences. 13:224-230. doi:10.1039/c3pp50252j L. I. Grossweiner and K. C.Smith, Photochemistry, in The Science of Photobiology, ed. K. C. Smith, Plenum Press, New York, 2nd edn, 1989, pp. 47–78 L. Pretali and A.Albini, in CRC Handbook of Organic ...