A5062087824- Advanced Chemical Physics Studies
- Protein Structure and Dynamics
- Molecular Spectroscopy and Structure
- Chemical Synthesis and Analysis
- Crystallography and molecular interactions
- Free Radicals and Antioxidants
- Molecular spectroscopy and chirality
- Spectroscopy and Quantum Chemical Studies
- Mass Spectrometry Techniques and Applications
- Chemical Reaction Mechanisms
- Chemical Thermodynamics and Molecular Structure
- Atmospheric Ozone and Climate
- Organic Chemistry Cycloaddition Reactions
- Photochemistry and Electron Transfer Studies
- Various Chemistry Research Topics
- DNA and Nucleic Acid Chemistry
- Inorganic and Organometallic Chemistry
- Enzyme Structure and Function
- Computational Drug Discovery Methods
- RNA and protein synthesis mechanisms
- History and advancements in chemistry
- Carbohydrate Chemistry and Synthesis
- Analytical Chemistry and Chromatography
- Inorganic Fluorides and Related Compounds
- Molecular Junctions and Nanostructures
University of Toronto
2013-2024
Eötvös Loránd University
2003-2024
University of Miskolc
2016-2024
Toronto Public Health
2018
University of the Philippines Diliman
2017
University of Szeged
2007-2016
Hungarian Academy of Sciences
2002-2014
Semmelweis University
2012
Centre National de la Recherche Scientifique
1986-2009
University of Groningen
2009
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 ion eliminates CO to immonium RCH NH2+. By contrast, protonated dipeptide H2NCH(R)C(+O)NHCH(R′)C(+O)X [X OCH3, NHCH(R″)COOH] B2 by elimination HX. These fragment metastable time scale with substantial kinetic energy release (T1/2 0.3–0.5 eV). Similarly, N-acetyl acid CH3C(+O)NHCH(R′)C(+O)X B also unimolecularly T1/2 values ∼ 0.5 eV. large releases...
The unimolecular and low energy collision-induced fragmentation reactions of the MH(+) ions N-acetyl-tri-alanine, N-acetyl-tri-alanine methyl ester, N-acetyl-tetra-alanine, tetra-alanine, penta-alanine, hexa-glycine, Leu-enkephalin have been studied with a particular emphasis on formation B n (n=3,4,5) ions. In addition, metastable ion protonated tetra-glycine, penta-glycine, amide studied. are prominent stable species in all spectra. fragment, part, by elimination CO to form A ions; this...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPeptide models. 1. Topology of selected peptide conformational potential energy surfaces (glycine and alanine derivatives)Andras Perczel, Janos G. Angyan, Marton Kajtar, Wladia Viviani, Jean Louis Rivail, John Frank Marcoccia, Imre CsizmadiaCite this: J. Am. Chem. Soc. 1991, 113, 16, 6256–6265Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July...
Fixed-center Gaussian-type functions (GTF) have been used as basis sets in an extensive SCF–MO–CI study on H−, H2, and H3+. An accurate description requires 4 or 5 s-GTF each center, plus at least one set of p-GTF, which are essential for the reproduction reliable potential curves; d-GTF are, however, minor importance. A constant p exponent may be successfully a wide variety nuclear configurations. Variational energies − 1.3397 1.2765 hartree were calculated most stable equilateral collinear...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBonding between nonbonded sulfur and oxygen atoms in selected organic molecules (a quantum chemical study)Janos G. Angyan, Raymond A. Poirier, Arpad Kucsman, Imre CsizmadiaCite this: J. Am. Chem. Soc. 1987, 109, 8, 2237–2245Publication Date (Print):April 1, 1987Publication History Published online1 May 2002Published inissue 1 April 1987https://pubs.acs.org/doi/10.1021/ja00242a001https://doi.org/10.1021/ja00242a001research-articleACS...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIrrelevance of d-orbital conjugation. I. .alpha.-Thiocarbanion. Comparative quantum chemical study the static and dynamic properties proton affinities carbanions adjacent to oxygen sulfurFernando Bernardi, Imre G. Csizmadia, Angelo Mangini, H. Bernhard Schlegel, Myung-Hwan Whangbo, Saul WolfeCite this: J. Am. Chem. Soc. 1975, 97, 8, 2209–2218Publication Date (Print):April 1, 1975Publication History Published online1 May 2002Published inissue 1...
The proton affinities of certain small molecules have been calculated as an energy difference between the parent molecule and protonated species. Various size Gaussian basis sets were used to see how approximate experimental values wavefunctions approached Hartree–Fock limit. correlation was excellent with extensive sets.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical definition of the size electron pairs and its stereochemical implicationsM. A. Robb, W. J. Haines, I. G. CsizmadiaCite this: Am. Chem. Soc. 1973, 95, 1, 42–48Publication Date (Print):January 1973Publication History Published online1 May 2002Published inissue 1 January 1973https://pubs.acs.org/doi/10.1021/ja00782a007https://doi.org/10.1021/ja00782a007research-articleACS PublicationsRequest reuse permissionsArticle...
Abstract Why bigger is better : A “steric wall” created by the N ‐(2,6‐diisopropylphenyl) substituent on bulky NHC ligand IPr (1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) guides reactants to and from Pd center through weak, fleeting (IPr)H–Pd interactions that help oxidative addition intermediate escape “the anti‐trap”. The alternative “side” approach leads transmetalation (the rate‐limiting step) for which a novel Pd–Zn interaction was identified. magnified image mechanism proposed...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPeptide models 6. New .beta.-turn conformations from ab initio calculations confirmed by x-ray data of proteinsAndras Perczel, Michael A. McAllister, Pal Csaszar, and Imre G. CsizmadiaCite this: J. Am. Chem. Soc. 1993, 115, 11, 4849–4858Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://pubs.acs.org/doi/10.1021/ja00064a053https://doi.org/10.1021/ja00064a053research-articleACS...
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 contributions different structural elements trimeric and pentameric full-length Aβ1−42 aggregates solution their stability conformational dynamics. We found that our models stable at a temperature 310 K, converge toward an interdigitated side-chain packing for intermolecular contacts within two β-sheet...
A three-dimensional classical trajectory calculation has been made of the dynamics reaction D + H 2 → DH . In contrast to earlier studies potential-energy surface was obtained ab initio, consequently results have predictive interest.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of the Wolff rearrangementImre G. Csizmadia, J. Font, and Otto P. StrauszCite this: Am. Chem. Soc. 1968, 90, 26, 7360–7361Publication Date (Print):December 1, 1968Publication History Published online1 May 2002Published inissue 1 December 1968https://pubs.acs.org/doi/10.1021/ja01028a041https://doi.org/10.1021/ja01028a041research-articleACS PublicationsRequest reuse permissionsArticle Views661Altmetric-Citations53LEARN ABOUT THESE...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure of an .alpha.-sulfonyl carbanionSaul Wolfe, Arvi Rauk, and Imre G. CsizmadiaCite this: J. Am. Chem. Soc. 1969, 91, 6, 1567–1569Publication Date (Print):March 1, 1969Publication History Published online1 May 2002Published inissue 1 March 1969https://pubs.acs.org/doi/10.1021/ja01034a069https://doi.org/10.1021/ja01034a069research-articleACS PublicationsRequest reuse permissionsArticle Views114Altmetric-Citations53LEARN ABOUT THESE...
Helices are among the predominant secondary structures in globular proteins. About 90% of residues them found to be α-helical conformation, and another 10% 310 conformation. There is a standing controversy between experimental some theoretical results, results concerning predominance each particular, helices. We address this by ab initio Hartree−Fock density functional theory studies helices with different lengths vacuum aqueous phase. Our show that (1) vacuum, all oligo(Ala) 4−10 adopt −...
In a number of cases the b2 ion observed in peptide mass spectra fragments directly to a1 ion. The present study examines scope this reaction and provides evidence as structure(s) ions undergoing fragmentation H-Ala-Gly+ fragments, part, ion, whereas isomeric H-Gly-Ala+ does not fragment Ab initio calculations energies show that different behavior can be rationalized terms protonated oxazolone structures for provided one assumes reverse activation energy ∼1 eV → a2; such is consistent with...
The allylic H-atom abstraction reaction plays a more dominant role, especially at lower temperature, than addition reactions in the case of CH2 [Formula: see text] CH-CH3 + •OH system. Different computational methods including ab initio as well density functional have been used to examine H-abstraction. Both energetically less favorable direct H-abstraction and indirect H-abstractions investigated. Using first principles computations, for abstraction, stable π- or reactantlike late...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPeptide models. 3. Conformational potential energy hypersurface of formyl-L-valinamideWladia Viviani, Jean Louis Rivail, Andras Perczel, and Imre G. CsizmadiaCite this: J. Am. Chem. Soc. 1993, 115, 18, 8321–8329Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://pubs.acs.org/doi/10.1021/ja00071a046https://doi.org/10.1021/ja00071a046research-articleACS PublicationsRequest...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination and analysis of the formic acid conformational hypersurfaceMichael R. Peterson Imre G. CsizmadiaCite this: J. Am. Chem. Soc. 1979, 101, 5, 1076–1079Publication Date (Print):February 1, 1979Publication History Published online1 May 2002Published inissue 1 February 1979https://pubs.acs.org/doi/10.1021/ja00499a003https://doi.org/10.1021/ja00499a003research-articleACS PublicationsRequest reuse permissionsArticle...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnalysis of the topological features conformational hypersurface n-butaneMichael R. Peterson and Imre G. CsizmadiaCite this: J. Am. Chem. Soc. 1978, 100, 22, 6911–6916Publication Date (Print):October 1, 1978Publication History Published online1 May 2002Published inissue 1 October 1978https://pubs.acs.org/doi/10.1021/ja00490a023https://doi.org/10.1021/ja00490a023research-articleACS PublicationsRequest reuse permissionsArticle...
Ab initio molecular-orbital calculations have been carried out on nine isomers corresponding to the empirical formula of CH3NO. The near-Hartree–Fock wavefunctions were used calculate ground-state energies as well dipole moments. total energy values and transition moments first 12 singlet triplet excited states calculated by virtual orbital technique. These latter results relevant some questions in photochemistry also gave basis theoretical electronic spectra. computed for ground studied...