TY - BOOK AU - Kiss, Edina AU - Láng, Emma AU - Molnár, István AU - Vasanits, Anikó TI - Érettségi felkészítő - Kémia - Emelt szint PB - Eötvös Kiadó CY - Budapest PY - 2025 SP - 214 SN - 9789633124109 UR - https://m2.mtmt.hu/api/publication/36154374 ID - 36154374 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Shanmugam, G AU - Polavarapu, PL AU - Láng, Emma AU - Majer, Zsuzsanna (Deckerné) TI - Conformational analysis of amyloid precursor protein fragment containing amino acids 667-676, and the effect of D-Asp and iso-Asp substitution at Asp(672) residue JF - JOURNAL OF STRUCTURAL BIOLOGY J2 - J STRUCT BIOL VL - 177 PY - 2012 IS - 3 SP - 621 EP - 629 PG - 9 SN - 1047-8477 DO - 10.1016/j.jsb.2012.01.012 UR - https://m2.mtmt.hu/api/publication/2014123 ID - 2014123 AB - Amyloid precursor protein (APP) fragment containing amino acids 667-676, (APP(667-676)), is a substrate for beta-secretase which is responsible for generating amyloid beta peptides. Conformational analysis of APP(667-676) peptide [Ac-Ser-Glu-Val-Lys-Met-Asp-Ala-Glu-Phe-Arg-NH2] and the effect of substitution of Asp(672) with D-Asp and iso-L-Asp, studied for the first time, demonstrate that the peptide backbone of APP(667-676) is flexible and adopts different conformations in different solvent environments (water, trifluoroethanol and dimethylsulfoxide). A major conformational difference was observed in trifluoroethanol solvent when Asp(672) is substituted with D-Asp and iso-Asp. These conformational changes involved in APP(667-676) may assist in understanding the interactions between beta-secretase and APP(667-676), with relevance to Alzheimer's disease. (C) 2012 Elsevier Inc. All rights reserved. LA - English DB - MTMT ER - TY - JOUR AU - Vass, Elemér AU - Láng, Emma AU - Samu, J AU - Majer, Zsuzsanna (Deckerné) AU - Kajtár-Peredy, Mária AU - Mák, Marianna AU - Radics, Lajos AU - Hollósi, Miklós TI - Vibrational spectroscopic detection of H-bonded b- and g-turns in cyclic peptides and glycopeptides JF - JOURNAL OF MOLECULAR STRUCTURE J2 - J MOL STRUCT VL - 440 PY - 1998 IS - 1-3 SP - 59 EP - 71 PG - 13 SN - 0022-2860 DO - 10.1016/S0022-2860(97)00216-0 UR - https://m2.mtmt.hu/api/publication/114332 ID - 114332 N1 - [6/1998] LA - English DB - MTMT ER - TY - JOUR AU - Láng, Emma AU - Majer, Zsuzsanna (Deckerné) AU - Vass, Elemér AU - Szabó, Sándor AU - Hallgas, B AU - Hollósi, Miklós TI - Racemization-induced defolding and aggregation of fragments of beta-amyloid protein: an early step in the formation of amyloid plaques JF - IDEGGYOGYASZATI SZEMLE / CLINICAL NEUROSCIENCE J2 - IDEGGYOGY SZEMLE VL - 51 PY - 1998 SP - 11 EP - 12 PG - 2 SN - 0019-1442 UR - https://m2.mtmt.hu/api/publication/1230617 ID - 1230617 LA - English DB - MTMT ER - TY - JOUR AU - Láng, Emma AU - Hargittai, B AU - Majer, Zsuzsanna (Deckerné) AU - Perczel, András AU - Mák, Marianna AU - Kajtár-Peredy, Mária AU - Radics, Lajos AU - Fasman, GD AU - Hollósi, Miklós TI - Synthesis and conformational analysis of the N-glycosylated cyclic:cyclo[Gly-Pro-Asn(GlcNAc)-Gly-NH-(CH2)(4)-CO] JF - PROTEIN AND PEPTIDE LETTERS J2 - PROTEIN PEPTIDE LETT VL - 3 PY - 1996 SP - 9 EP - 16 PG - 8 SN - 0929-8665 UR - https://m2.mtmt.hu/api/publication/2715 ID - 2715 N1 - Department of Organic Chemistry, Eötvös University, P.O.B. 32, 1518 Budapest, Hungary Ctrl. Res. Inst. for Chem. of HAS, P.O.B. 17, 1525 Budapest, Hungary Department of Biochemistry, Brandeis University, Waltham, MA 02254, United States Cited By :6 Export Date: 21 July 2023 CODEN: PPELE Correspondence Address: Hollósi, M.; Department of Organic Chemistry, P.O.B. 32, 1518 Budapest, Hungary AB - This paper reports the synthesis and conformational characterization of the cyclic peptides cyclo[Gly-Pro-Asp(ocHex)-Gly-NH-(CH2)(4)-Co] ((1) under bar), cyclo[Gly-Pro-Asp-Gly-NH-(CH2)(4)-CO] ((2) under bar), cyclo[Gly-Pro-Asn-Gly-NH-(CH2)(4)-CO] ((3) under bar) and the Asn-glycosylated cyclic title compound cyclo[Gly-Pro-Asn(GlcNAc)-Gly-NH-(CH2)(4)-CO] ((4) under bar) (Scheme 1). LA - English DB - MTMT ER - TY - CHAP AU - Tóth, Gábor AU - Váradi, Györgyi AU - Janáky, Tamás AU - Penke, Botond AU - Mák, Marianna AU - Láng, Emma AU - Ötvös, László AU - Hegedűs, Zoltán AU - Monostori, Éva ED - Maia, HLS TI - Synthesis of phosphotyrosine-containing peptides: comparison of different methods and their use to investigate cell signalling via the T-cell receptor T2 - Peptides 1994 PB - Escom Science Publishers B.V. CY - Leiden SN - 9072199219 T3 - European Peptide Symposia ; 3. PY - 1995 SP - 743 EP - 744 PG - 2 UR - https://m2.mtmt.hu/api/publication/120015 ID - 120015 LA - English DB - MTMT ER - TY - JOUR AU - Szókán, Gyula AU - Majer, Zsuzsanna (Deckerné) AU - Láng, Emma AU - Kajtar, M AU - Hollósi, Miklós AU - Peredykajtar, M TI - Chromatographic Studies ON The Racemization of Thiopeptides JF - JOURNAL OF LIQUID CHROMATOGRAPHY J2 - J LIQ CHROMATOGR VL - 18 PY - 1995 IS - 5 SP - 941 EP - 964 PG - 24 SN - 0148-3919 DO - 10.1080/10826079508010404 UR - https://m2.mtmt.hu/api/publication/1087403 ID - 1087403 N1 - Department of Organic Chemistry, Eötvös University, P.O. Box 32, H-1518, Budapest 112, Hungary Central Research Institute for Chemistry of the Hungarian Academy of Sciences, P.O. Box 17, H-1515 Budapest, Hungary Cited By :4 Export Date: 31 October 2023 AB - It was found by chromatographic, CD and NMR methods, that the thionation of piperazine-2,5-diones [cyclo(Aaa(1)-Aaa(2)) --> cyclo (Aaat(1)-Aaat(2) (Aaa = -NH-CHR-CO-; Aaat = -NH-CHR-CS-)] or piperazine-2,5-onthiones [cyclo(Aaat(1)-Aaa(2)) --> cyclo (Aaat(1)-Aaat(2))] and, occasionally, even the spontaneous cyclization of endothiodipeptide esters [H-Aaat(1)-Aaa(2) OR] result in enantiomeric (Aaa(1) or Aaa(2) = Gly) or diastereomeric mixtures of piperazine monothiones or dithiones. The diastereoisomers were separated by semipreparative HPLC and their quantitative product distribution was determined by an optimized HPLC method on Hypersil-silica column with CH2Cl2-EtOAc eluent mixtures. Isocratic RP-HPLC on ODS-Hypersil column and pre-column derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide (Marfey's reagent) were used to monitor the racemization of Ala and Pro residues and to determine the ratio of enantiomers. Thionation of urethane protected dipeptide esters or dethionation of the corresponding endothiodipeptide derivatives were not found to result in significant racemization. However, during the thionation of cyclic dipeptides or thiopeptides or isolation of piperazine-2,5- mono- or dithiones a partial or complete racemization could always be detected. Moreover, the acidic hydrolysis of thiopeptides was also accompanied by racemization and resulted in partially racemized amino (oxo)acids. LA - English DB - MTMT ER - TY - JOUR AU - Shaw, RA AU - Láng, Emma AU - Hollósi, Miklós AU - Mantsch, HH TI - Hydrogen-bonding And Isomerization IN Thioamide Peptide Derivatives JF - SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY J2 - SPECTROCHIM ACTA A VL - 51 PY - 1995 IS - 8 SP - 1399 EP - 1412 PG - 14 SN - 1386-1425 DO - 10.1016/0584-8539(95)01448-9 UR - https://m2.mtmt.hu/api/publication/1087405 ID - 1087405 N1 - Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Man. R3B 1Y6, Canada Department of Organic Chemistry, L. Eötvös University, H-1117 Budapest, Hungary Cited By :22 Export Date: 13 May 2024 Correspondence Address: Shaw, R.A.; Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Man. R3B 1Y6, Canada AB - The conformations of fourteen thiopeptides in three solvents (acetonitrile, methylene chloride, DMSO) are discussed as inferred by interpretation of the amide infrared absorptions. The spectra indicate that the enhanced acidity of the thioamide N-H proton (and hence the stronger hydrogen-bonding donor potential) promotes the formation of C-5 ring structures that are not often found in unsubstituted peptides, and strong C(S)-N-H --> O=C hydrogen bonds render both C-7 (gamma-turn) and C-10 (beta-turn) structures more stable than their oxoamide counterparts. The ability of infrared spectra to discriminate among C-5, C-7, and C-10 structures is evaluated and discussed. LA - English DB - MTMT ER - TY - JOUR AU - FABIAN, H AU - Ötvös, László AU - SZENDREI, GI AU - Láng, Emma AU - MANTSCH, HH TI - TYROSINE-PHOSPHORYLATION VERSUS SERINE-PHOSPHORYLATION LEADS TO CONFORMATIONAL-CHANGES IN A SYNTHETIC TAU-PEPTIDE JF - JOURNAL OF BIOMOLECULAR STRUCTURE & DYNAMICS J2 - J BIOMOL STRUCT DYN VL - 12 PY - 1994 IS - 3 SP - 573 EP - 579 PG - 7 SN - 0739-1102 DO - 10.1080/07391102.1994.10508760 UR - https://m2.mtmt.hu/api/publication/2014168 ID - 2014168 AB - One of the major immunodominant epitopes of the paired helical filaments (PHF) of Alzheimer's disease is the peptide sequence GAEIVYKSPVVSGD (T3), comprising amino acids 389-402 of the microtubule associated protein, tau when it is phosphorylated at the first serine residue. While the corresponding anti-PHF monoclonal antibody recognizes the peptide phosphorylated at either serine, it does not recognize the tyrosine-phosphorylated peptide. Here we describe the effect of serine- versus tyrosine-phosphorylation on the conformation of a synthetic tau peptide. While adding a phosphate to the serine residue has practically no impact on the structure of the non-phosphorylated peptide, phosphorylation of the tyrosine results in considerable conformational changes. LA - English DB - MTMT ER - TY - JOUR AU - Perczel, András AU - Láng, Emma AU - Hollósi, Miklós AU - Fasman, GD TI - SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF N-GLYCOPEPTIDES. 2. CD, MOLECULAR-DYNAMICS, AND NMR SPECTROSCOPIC STUDIES ON LINEAR N-GLYCOPEPTIDES JF - BIOPOLYMERS J2 - BIOPOLYMERS VL - 33 PY - 1993 SP - 665 EP - 685 PG - 21 SN - 0006-3525 DO - 10.1002/bip.360330416 UR - https://m2.mtmt.hu/api/publication/2743 ID - 2743 N1 - Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts, 02254-9110, United States Institute of Organic Chemistry, Eötvös University, 112, P.O. Box 32, Budapest, H-1518, Hungary Cited By :34 Export Date: 30 June 2023 Correspondence Address: Fasman, G.D.; Graduate Department of Biochemistry, , Waltham, Massachusetts, 02254-9110, United States AB - The comprehensive structural analysis reported herein of eight N-glycopeptides, in three different solvents, is based on quantitative CD experiments, homonuclear nuclear Overhauser effect measurements, and molecular dynamics (MD) calculations. Although several orientations of the two amide planes attached to the carbohydrate pyranose ring are possible, according to NOE, CD data, and MD simulations, of all of the glycopeptide models, regardless of the type of the carrier peptide, only one dominant conformer population was found. This conformer is characterized by a nearly trans orientation of the CH and NH hydrogens of both acetamido groups. This finding is in perfect agreement with x-ray crystallographic data on the solid state conformation of the 1-N-acetyl- and 1-N- (beta-aspartoyl) -2-acetamido-2-deoxy-beta-D-glucopyranosylamine. The precise identification of this dominant conformer of N-glycopeptides in solution was the major question addressed herein by the structural analyses. A ''CD additivity'' experiment was carried out using an equimolar solution of Boc-Pro-Asp-NHCH3 and 1-N-acetyl-3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-beta-D-glucopyranosyla mine at ambient temperature in acetonitrile. The CD spectrum obtained from the equimolar solution of the above two molecules (the ''spectroscopic sum'') was identical with the CD curve obtained from the algebraic summation of the individually recorded CD spectra of the peptide and the carbohydrate moiety (''mathematical sum''). The global picture of the CD spectral analyses of the eight parent peptides with the eight N-glycopeptides revealed that in trifluoroethanol and acetonitrile, the side-chain modification of the Asn models (natural N-glycopeptide analogues) by N-glycosylation has a significant effect on the conformation of the carrier peptide, resulting in a decrease in the original type I beta-turn content. Simultaneously, the type II beta-turn conformational percentage increased to almost-equal-to 20%. Such a conformational ratio change seems to be larger than the expected errors arising from the CD analyses, and agrees with the results of MD calculations. N-glycosylation of Asn residues causes perturbations, not only through the covalent bond, but also through specific hydrogen bonds between the backbone and side chain atoms. CD spectroscopy, augmented by efficient CD curve deconvolution techniques, has proved to be a useful tool for studying multicomponent conformer mixtures of small linear peptides in solution and changes of conformational equilibria caused by N-glycosylation. LA - English DB - MTMT ER -