Investigation of the formation of Strecker aldehydes from the reaction of Amadori rearrangement products with α-amino acids in low moisture model systems

2000 ◽  
Vol 211 (6) ◽  
pp. 400-403 ◽  
Author(s):  
D. R. Cremer ◽  
M. Vollenbroeker ◽  
Karl Eichner
Keyword(s):  
Amino Acids ◽  
Model Systems ◽  
Amadori Rearrangement ◽  
Strecker Aldehydes

scholarly journals Strecker degradation products of aspartic and glutamic acids and their amides

2013 ◽  
Vol 19 (No. 2) ◽  
pp. 41-45 ◽  
Author(s):  
J. Rössner ◽  
J. Velíšek ◽  
F. Pudil ◽  
J. Davídek
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Degradation Products ◽  
Dicarboxylic Acids ◽  
Reaction Products ◽  
Degradation Reactions ◽  
Strecker Aldehydes ◽  
Volatile Products ◽  
Acid Acid

Aspartic and glutamic acids, asparagine and glutamine were oxidised with either potassium peroxodisulphate or glyoxal. Nonvolatile products were derivatised and analysed by GC/FID and GC/MS. Volatile reaction products were isolated and analysed by the same methods. It was found that the degradation reactions of amino acids are complex. Amino acids are principally degraded via the corresponding a-keto acids to Strecker aldehydes (aspartic acid to oxalacetic and 3-oxopropionic acids and glutamic acid to a-ketoglutaric and 4-oxobutyric acids), which are unstable and decomposed by decarboxylation to the corresponding aldehydes. Aspartic acid also eliminates ammonia and yields fumaric acid whereas glutamic acid gives rise to an imine, pyroglutamic acid. A recombination of free radicals leads to dicarboxylic acids (succinic acid from aspartic acid, succinic, glutaric and adipic acids from glutamic acid). The major volatile products (besides the aldehydes) are lower carboxylic acids (acetic acid from aspartic acid and propionic acid acid from glutamic acid) that can at least partly arise by radical reactions. In both quality and quantity terms, a higher amount of degradation products arises by oxidation of amino acids by peroxodisulphate.

scholarly journals Pressure dependence of side chain 1H and 15N-chemical shifts in the model peptides Ac-Gly-Gly-Xxx-Ala-NH2

2020 ◽  
Vol 74 (8-9) ◽  
pp. 381-399
Author(s):  
Markus Beck Erlach ◽  
Joerg Koehler ◽  
Claudia E. Munte ◽  
Werner Kremer ◽  
Edson Crusca ◽  
...  
Keyword(s):  
Amino Acids ◽  
Pressure Dependence ◽  
Chemical Shifts ◽  
Model Systems ◽  
Random Coil ◽  
Nonlinear Dependence ◽  
Side Chain ◽  
Unfolded Proteins ◽  
Pressure Coefficients ◽  
Compression Effects

Abstract For interpreting the pressure induced shifts of resonance lines of folded as well as unfolded proteins the availability of data from well-defined model systems is indispensable. Here, we report the pressure dependence of 1H and 15N chemical shifts of the side chain atoms in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH2 (Xxx is one of the 20 canonical amino acids) measured at 800 MHz proton frequency. As observed earlier for other nuclei the chemical shifts of the side chain nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The pressure response is described by a second degree polynomial with the pressure coefficients B1 and B2 that are dependent on the atom type and type of amino acid studied. A number of resonances could be assigned stereospecifically including the 1H and 15N resonances of the guanidine group of arginine. In addition, stereoselectively isotope labeled SAIL amino acids were used to support the stereochemical assignments. The random-coil pressure coefficients are also dependent on the neighbor in the sequence as an analysis of the data shows. For Hα and HN correction factors for different amino acids were derived. In addition, a simple correction of compression effects in thermodynamic analysis of structural transitions in proteins was derived on the basis of random-coil pressure coefficients.

scholarly journals Advances in Chemistry of Isothiocyanate-derived Colourants

2009 ◽  
Vol 27 (Special Issue 1) ◽  
pp. S207-S210
Author(s):  
K. Cejpek ◽  
J. Velíšek
Keyword(s):  
Amino Acids ◽  
Essential Oils ◽  
Maillard Reaction ◽  
Heterogeneous Group ◽  
Model Systems ◽  
Alkaline Media ◽  
Reaction Conditions ◽  
Condensation Products ◽  
Amino Compounds ◽  
Methylene Group

This study is focused on the reactions of isothiocyanates (ITCs) in the presence of amino compounds leading to coloured structures <I>via</I> substituted 2-thiohydantoins. A series of complementary experiments has been done and appropriate reaction conditions and structural prerequisites have been defined. Low-molecular colourants isolated and characterised from the model systems can be sorted into three groups. Yellow to red diastereomeric dehydrodimers of 2-thiohydantoin derivatives that contain an acidic methylene group are formed in mixtures consisted of ITCs and amino acids with &alpha;-methylene group in mild acidic to mild alkaline systems. The condensation products of the 2-thiohydantoins with reactive aromatic or heterocyclic carbaldehydes from the Maillard reaction, essential oils etc. comprise a heterogeneous group of mostly yellow colourants. Blue compounds of two types are structurally more complicated structures that arise from <I>N</I>-substituted amino acids and ITCs in alkaline media.

Design Of a Most Efficient Inhibitor Of TFPI By Molecular Fusion Of Two Inhibitory Peptides

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3564-3564
Author(s):  
Michael Dockal ◽  
Rudolf Hartmann ◽  
Thomas Polakowski ◽  
Johannes Brandstetter ◽  
Willibald Kammlander ◽  
...  
Keyword(s):  
Amino Acids ◽  
Endothelial Cells ◽  
Cell Surface ◽  
Platelet Activation ◽  
Research Funding ◽  
Thrombin Generation ◽  
Fusion Peptide ◽  
Peptide Inhibitors ◽  
Model Systems ◽  
Inhibitory Peptide

Abstract TFPI is an important inhibitor of the extrinsic coagulation pathway. It efficiently inhibits TF-FVIIa and FXa by quaternary complex formation. Plasma contains various truncated forms of TFPI which are poor inhibitors, and full length (fl)TFPI (0.3 – 0.5 nM) which is the most active TFPI in plasma. flTFPI is released from platelets upon activation, and increases flTFPI concentrations locally up to 30-fold. Most intravascular TFPI (∼80%) is associated with endothelial cells. Both endothelial forms, TFPIa and TFPIb, are similarily effective inhibitors of FX activation on the endothelial cell surface. Inhibition of TFPI in hemophilia models with blocking antibodies, aptamers or peptide inhibitors improves hemostasis and may become an option to treat hemophilia. Recently, we presented peptide inhibitors of TFPI that enhance coagulation in hemophilia models. Two optimized peptides, JBT-A7 and JBT-B5, efficiently blocked inhibitory activity of TFPI and bound to distinct binding sites. We demonstrated the crystal structure of JBT-A7, a linear TFPI inhibitory peptide composed of 20 amino acids, bound to NtermK1 (TFPI 1-83). JBT-B5, a cyclic TFPI inhibitory peptide of 23 amino acids, co-crystallized with TFPI KD1-KD2 (TFPI 22-150). Overlaying the KD1 structure in the KD1-KD2/JBT-B5 and the NTermK1/JBT-A7 complex provided atomic details for linking the two peptide entities. Binding of peptides to TFPI and TFPI fragments was studied by BioCore. The TFPI inhibitory potential of the resulting fusion peptide was tested in model systems (FXa inhibition and TF-FVIIa catalyzed FX activation) and global hemostatic assays (TF-triggered thrombin generation) using hemophilia plasma. To model situations of increased TFPI concentration, both model and plasma assays were carried out at TFPI concentrations up to 10 nM, which is 40-50-fold higher than the physiological flTFPI plasma concentration. To characterize the inhibition of platelet TFPI, we used platelets isolated from blood samples and platelet rich plasma from different donors. Binding of a biotinylated fusion peptide on living HUVE cells was assessed by fluorescence activated cell sorting (FACS) and fluorescence microscopy. Inhibition of cell surface TFPI was analyzed on cultivated HUVECs stimulated with TNFa for TF expression. We monitored FXa generation by the TFPI-dependent cell surface FX activation complex by conversion of an FXa-specific fluorogenic substrate. The overlay of the crystal structures of KD1-KD2/JBT-B5 and the NTermKD1/JBT-A7 complexes revealed non-overlapping epitopes and close proximity of the termini of both peptides. The distance could be bridged by an approximately ten amino acid linker. A fusion peptide with a 10-serine-linker was synthesized and showed highly improved dissociation in Biacore experiments and most efficiently inhibited TFPI activity in the model assays. In contrast, single peptides only partially inhibit TFPI especially at high TFPI concentrations. In thrombin generation assays using hemophilia plasma, the fusion peptide showed a substantially higher ability than the single peptides to increase the thrombin peak even at elevated TFPI. The fusion peptide efficiently inhibited TFPI released from platelets and improved thrombin generation in TFPI deficient plasma reconstituted with platelets as the only source of TFPI released upon platelet activation. The fusion peptide was also shown to bind TFPI on the surface of living HUVECs. This is consistent with its binding epitopes on KD1 and KD2 which result in inhibition of cell surface TFPI in a cell based FX activation assay. Thus, we demonstrate that a molecular fusion peptide most efficiently inhibits all physiologic forms of TFPI. X-ray structures of binary and ternary peptide TFPI complexes provided atomic details for linking two single peptides to generate a fusion peptide that most efficiently blocks TFPI in plasma, released from platelets and associated with endothelial cells. It most efficiently neutralizes TFPI even at substantially elevated concentrations occurring at sites of platelet activation. Our observations support the notion that targeting TFPI with TFPI inhibitors is a promising novel strategy to mitigate the bleeding risk in hemophilia patients. Disclosures: Dockal: Baxter Innovations GmbH, Vienna, Austria: Employment. Hartmann:Baxter Innovations GmbH, Vienna, Austria: Employment. Polakowski:3B Pharmaceuticals, Berlin, Germany: Employment. Brandstetter:Baxter Innovations GmbH, Vienna, Austria: Research Funding. Kammlander:Baxter Innovations GmbH, Vienna, Austria: Employment. Panholzer:Baxter Innovations GmbH, Vienna, Austria: Employment. Redl:Baxter Innovations GmbH, Vienna, Austria: Employment. Osterkamp:3B Pharmaceuticals, Berlin, Germany: Employment. Rosing:Baxter Innovations GmbH, Vienna, Austria: Consultancy, Research Funding. Scheiflinger:Baxter Innovations GmbH, Vienna, Austria: Employment.

Experimental and Theoretical Study of the First Vanadocene(IV) Complexes of α-Amino Acids Prepared from Vanadocene Dichloride

2004 ◽  
Vol 69 (4) ◽  
pp. 811-821 ◽  
Author(s):  
Jaromír Vinklárek ◽  
Hana Paláčková ◽  
Jan Honzíček
Keyword(s):  
Amino Acids ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Model Systems ◽  
Amino Groups ◽  
Aqueous Methanol ◽  
Functional Theory ◽  
Elemental Analyses ◽  
Vanadocene Dichloride

The first bioinorganic vanadocene(IV) complexes of α-amino acids ([Cp2V(aa)]Cl, Cp = η5-C5H5, aa = glycine, L-alanine, L-valine) were prepared by reaction of vanadocene dichloride ([Cp2VCl2]) and α-amino acids in aqueous methanol. Analogous cationic complexes with PF6- counterions were obtained by metathetical reactions of the chloride precursors with KPF6. These compounds are of great interest as model systems for the vanadocene moiety binding to proteins. All complexes have been characterized by elemental analyses and IR, Raman and EPR spectroscopies. On the basis of EPR spectra, a chelate in all the studied complexes was proposed, formed by the carboxylato and amino groups. This structure has also been confirmed by density functional theory (DFT) calculations.

The effect of the length and flexibility of the side chain of basic amino acids on the binding of antimicrobial peptides to zwitterionic and anionic membrane model systems

2012 ◽  
Vol 20 (5) ◽  
pp. 1723-1739 ◽  
Author(s):  
Amanda L. Russell ◽  
Brittany C. Williams ◽  
Anne Spuches ◽  
David Klapper ◽  
Antoine H. Srouji ◽  
...  
Keyword(s):  
Amino Acids ◽  
Antimicrobial Peptides ◽  
Model Systems ◽  
Membrane Model ◽  
Side Chain ◽  
Basic Amino Acids
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