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MIKL
S HOLL
SI MEDHEN ZEWDU EMMA KOLLT ZSUZSA MAJER MRTON KAJTR GYULA BATTA KATALIN K
VR PTER SNDOR 《Chemical biology & drug design》1990,36(2):173-181
Mono- and dithionated N-acyl amino acid and dipeptide N′-methylamides were synthesized using Lawesson's reagent and 5-thioacetyl thioglycolic acid. The conformation of the thionated models was characterized by IR, 13C, and 1H NMR spectroscopy, including NOE experiments. The formation of —C=S…H—N—C=X (X = O or S) intramolecular H-bonds of the type 2 → 2. 1 → 3 and 1 → 4 was evidenced by the characteristic shifts of the IR stretching frequencies of the NH group. Act-Pro-NHCH3 (4) and Act-Prot-NHCH3 (5) were found to be present as mixtures of rotational isomers about the CS—N bond. 13C chemical shifts of the γ- and β-carbons of the proline ring elucidated the conformation (Z or E) of the tertiary thioamide group. Our results suggest that the conformation of thiopeptides is determined by two factors: 1) the H-bond donating and accepting ability of the thioamide group and 2) the repulsion between the thiocarbonyl sulfur atom and the side chain groups of the neighbouring amino acid residues. 相似文献
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ERIKA SZAB
JNOS MURVAI PTER FBIN FERENC FBIN MIKL
S HOLL
SI JUDIT KaJTR ZSUZSA BUZS MIHLY SAJG
SNDOR PONGOR BENCE ASB
TH 《Chemical biology & drug design》1993,42(6):527-532
The amino acid sequence of the 27 kDa protein responsible for the haemolytic activity of Bacillus thuringiensis subsp. israelensis toxin has been analysed by secondary structure prediction, helical wheel/net diagrams and molecular mechanics calculations. We found that segment 116–126 presumably forms a strongly amphiphilic α-helix. This is supported by the findings that the synthesized segment 116-126 (a) has a significant α-helical content in water, and (b) displays an in vitro haemolytic activity comparable to that of bee venom peptide melittin. As segment 116-126 is present in the haemolyzing, but not present in the non-haemolyzing proteins from B. thuringiensis toxins, we suggest that this segment is responsible for the lytic potential of the B. thuringiensis subsp. israelensis protein. 相似文献
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