Imre G. Csizmadia

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Amyloid oligomers are considered to play causal roles in the pathogenesis of amyloid-related degenerative diseases including Alzheimer's disease. Using MD simulation techniques, we explored the contributions of the different structural elements of trimeric and pentameric full-length Abeta1-42 aggregates in solution to their stability and conformational(More)
Protonated amino acids and derivatives RCH(NH2)C(+O)X · H(+) (X = OH, NH2, OCH3) do not form stable acylium ions on loss of HX, but rather the acylium ion eliminates CO to form the immonium ion RCH = NH 2 (+) . By contrast, protonated dipeptide derivatives H2NCH(R)C(+O)NHCH(R')C(+O)X · H(+) [X = OH, OCH3, NH2, NHCH(R″)COOH] form stable B2 ions by(More)
The unimolecular and low energy collision-induced fragmentation reactions of the MH(+) ions of N-acetyl-tri-alanine, N-acetyl-tri-alanine methyl ester, N-acetyl-tetra-alanine, tetra-alanine, penta-alanine, hexa-glycine, and Leu-enkephalin have been studied with a particular emphasis on the formation and fragmentation of B n (n=3,4,5) ions. In addition, the(More)
Various folded molecular structures contain different amount of information. The relative amount of information may be related to relative entropy or entropy change. The conformational entropy change for n-butane has been computed as the function of rotation around the central C-C bond. It appears that the g+ or g- conformers contain about 16% more(More)
Two sites of a Pro-Pro diamide were subjected to individual Pro --> Thr point mutations. The parent diamide Pro-Pro as well as selected conformers of the Pro-Thr and Thr-Pro mutant models were subjected to molecular computations at the B3LYP/6-31G(d) level of theory. At the optimized geometries, thermodynamic functions (S, H, and G) were computed. In order(More)
In a number of cases the b2 ion observed in peptide mass spectra fragments directly to the a1 ion. The present study examines the scope of this reaction and provides evidence as to the structure(s) of the b2 ions undergoing fragmentation to the a1 ion. The b2 ion H-Ala-Gly+ fragments, in part, to the a1 ion, whereas the isomeric b2 ion H-Gly-Ala+ does not(More)
This study is on structure and stability of sheetlike conformers of beta-peptides; never seen new foldamers are reported here for the first time. Single- and double-stranded structures are analyzed, and the seeds of large beta-layers and biocompatible nanomaterials are described here. Both the monomeric, HCO-[NH-CH(2)-CH(2)CO](n)-NH(2), and dimeric forms,(More)
First principle quantum molecular computations have been carried out at the B3LYP/6-31G(d,p) and G3MP2B3 levels of theory on ethyl mercaptan and diethyl disulfide to study their full conformational space. The consequences of molecular axis chirality for the potential energy hypersurface of diethyl disulfide was fully explored. Thermodynamic functions (U, H,(More)