scholarly journals Unexpected Importance of Aromatic-Aliphatic and Aliphatic Side Chain-Backbone Interactions in the Stability of Amyloids

2017 ◽  
Vol 23 (46) ◽  
pp. 11046-11053 ◽  
Author(s):  
Dragan B. Ninković ◽  
Dušan P. Malenov ◽  
Predrag V. Petrović ◽  
Edward N. Brothers ◽  
Shuqiang Niu ◽  
...  
Keyword(s):  
Side Chain ◽  
Aliphatic Side Chain ◽  
The Stability

Effect of side-chain hydrophobic bonding on the stability of homopolyamino acid ?-helices: Conformational studies of poly-L-leucine in water

Biopolymers ◽  
1970 ◽  
Vol 9 (7) ◽  
pp. 749-764 ◽  
Author(s):  
Sanford E. Ostroy ◽  
Noah Lotan ◽  
Richard T. Ingwall ◽  
Harold A. Scheraga
Keyword(s):  
Side Chain ◽  
Conformational Studies ◽  
The Stability ◽  
Hydrophobic Bonding

Peptide folding induced by Cα-methylated, chiral α-acids with a long aliphatic side chain

2006 ◽  
pp. 270-271
Author(s):  
Marco Crisma ◽  
Cristina Peggion ◽  
Fernando Formaggio ◽  
Bernard Kaptein ◽  
Quirinus B. Broxterman ◽  
...  
Keyword(s):  
Peptide Folding ◽  
Side Chain ◽  
Aliphatic Side Chain

scholarly journals Studies on the synthesis and stability of α-ketoacyl peptides

Amino Acids ◽  
2020 ◽  
Vol 52 (10) ◽  
pp. 1425-1438
Author(s):  
Johann Sajapin ◽  
Michael Hellwig
Keyword(s):  
Peptide Bond ◽  
Side Chain ◽  
Peptide Backbone ◽  
Post Translational Modifications ◽  
Degradation Reactions ◽  
Keto Acids ◽  
Strecker Aldehydes ◽  
The Stability ◽  
Dehydration Processes ◽  
Hydrolysis Of

Abstract Oxidative stress, an excess of reactive oxygen species (ROS), may lead to oxidative post-translational modifications of proteins resulting in the cleavage of the peptide backbone, known as α-amidation, and formation of fragments such as peptide amides and α-ketoacyl peptides (α-KaP). In this study, we first compared different approaches for the synthesis of different model α-KaP and then investigated their stability compared to the corresponding unmodified peptides. The stability of peptides was studied at room temperature or at temperatures relevant for food processing (100 °C for cooking and 150 °C as a simulation of roasting) in water, in 1% (m/v) acetic acid or as the dry substance (to simulate the thermal treatment of dehydration processes) by HPLC analysis. Oxidation of peptides by 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ) proved to be the most suited method for synthesis of α-KaPs. The acyl side chain of the carbonyl-terminal α-keto acid has a crucial impact on the stability of α-KaPs. This carbonyl group has a catalytic effect on the hydrolysis of the neighboring peptide bond, leading to the release of α-keto acids. Unmodified peptides were significantly more stable than the corresponding α-KaPs. The possibility of further degradation reactions was shown by the formation of Schiff bases from glyoxylic or pyruvic acids with glycine and proven through detection of transamination products and Strecker aldehydes of α-keto acids by HPLC–MS/MS. We propose here a mechanism for the decomposition of α-ketoacyl peptides.

scholarly journals Monitoring the stabilities of a mixture of peptides by mass-spectrometry-based techniques

2019 ◽  
Vol 25 (1) ◽  
pp. 73-81 ◽  
Author(s):  
Daniel R Fuller ◽  
Christopher R Conant ◽  
Tarick J El-Baba ◽  
Zhichao Zhang ◽  
Kameron R Molloy ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Transition State ◽  
Elevated Temperatures ◽  
Proteolytic Enzymes ◽  
Side Chain ◽  
Free Energies ◽  
Dissociation Kinetics ◽  
Penultimate Proline ◽  
The Stability

Biomolecular degradation plays a key role in proteostasis. Typically, proteolytic enzymes degrade proteins into smaller peptides by breaking amino acid bonds between specific residues. Cleavage around proline residues is often missed and requires highly specific enzymes for peptide processing due to the cyclic proline side-chain. However, degradation can occur spontaneously (i.e. in the absence of enzymes). In this study, the influence of the first residue on the stability of a series of penultimate proline containing peptides, with the sequence Xaa–Pro–Gly–Gly (where Xaa is any amino acid), is investigated with mass spectrometry techniques. Peptides were incubated as mixtures at various solution temperatures (70℃ to 90℃) and were periodically sampled over the duration of the experiment. At elevated temperatures, we observe dissociation after the Xaa–Pro motif for all sequences, but at different rates. Transition state thermochemistry was obtained by studying the temperature-dependent kinetics and although all peptides show relatively small differences in the transition state free energies (∼95 kJ/mol), there is significant variability in the transition state entropy and enthalpy. This demonstrates that the side-chain of the first amino acid has a significant influence on the stability of the Xaa–Pro sequence. From these data, we demonstrate the ability to simultaneously measure the dissociation kinetics and relative transition state thermochemistries for a mixture of peptides, which vary only in the identity of the N-terminal amino acid.

scholarly journals Efficient Synthesis of α-Branched Purine-Based Acyclic Nucleosides: Scopes and Limitations of the Method

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4307
Author(s):  
Jan Frydrych ◽  
Lenka Poštová Slavětínská ◽  
Martin Dračínský ◽  
Zlatko Janeba
Keyword(s):  
Acetic Anhydride ◽  
Room Temperature ◽  
Side Chain ◽  
Efficient Synthesis ◽  
Purine Derivatives ◽  
Aliphatic Side Chain ◽  
Acyclic Nucleosides ◽  
Efficient Route ◽  
High Yields ◽  
Trimethylsilyl Trifluoromethanesulfonate

An efficient route to acylated acyclic nucleosides containing a branched hemiaminal ether moiety is reported via three-component alkylation of N-heterocycle (purine nucleobase) with acetal (cyclic or acyclic, variously branched) and anhydride (preferentially acetic anhydride). The procedure employs cheap and easily available acetals, acetic anhydride, and trimethylsilyl trifluoromethanesulfonate (TMSOTf). The multi-component reaction is carried out in acetonitrile at room temperature for 15 min and provides moderate to high yields (up to 88%) of diverse acyclonucleosides branched at the aliphatic side chain. The procedure exhibits a broad substrate scope of N-heterocycles and acetals, and, in the case of purine derivatives, also excellent regioselectivity, giving almost exclusively N-9 isomers.

An α-diketone from the condensation product of glucose and ethyl acetoacetate

1964 ◽  
Vol 17 (10) ◽  
pp. 1174 ◽  
Author(s):  
LK Dalton
Keyword(s):  
Hydrogen Peroxide ◽  
Solid State ◽  
Hydrogen Chloride ◽  
Ethyl Acetoacetate ◽  
Condensation Product ◽  
Side Chain ◽  
Furoic Acid ◽  
Aliphatic Side Chain ◽  
Benzilic Acid ◽  
Reversible Cyclization

When the product from the condensation of glucose and ethyl acetoacetate, ethyl 2-D-arabino-tetrahydroxybutyl-5-methyl-4-furoate (Ia), is heated in ethanolic hydrogen chloride, an a-diketone (IVa) is produced. It exists as a mono-enol in solution and in the solid state. Although this diketone is formed with an aliphatic side chain, there is at first a predominant, but reversible, cyclization to the "difuran" (II). With hydrogen peroxide the diketone yields 2-carboxymethy1-5- methyl-4-furoic acid (VII), and with alkali it undergoes a benzilic acid rearrangement.

scholarly journals Cholesterol's Aliphatic Side Chain Structure Modulates Membrane Properties

2016 ◽  
Vol 110 (3) ◽  
pp. 84a
Author(s):  
Daniel Huster ◽  
Thomas Meyer ◽  
Jörg Nikolaus ◽  
Dong Jae Baek ◽  
Ivan Haralampiev ◽  
...  
Keyword(s):  
Chain Structure ◽  
Membrane Properties ◽  
Side Chain ◽  
Aliphatic Side Chain
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