Synthesis and structural analysis of vinylogous peptides

A Z- or E-ethenyl group has been inserted between the -carbon andthe carboxyl group of the proline residue by stereoselective Hornersynthesis. The resulting vinylogous amino acid has been coupled with aminocompounds by classical methods, and model amino acid derivatives anddipeptides containing a Z- or E-CH=CMe group have been investigated insolution by ¹H-NMR and IR spectroscopy, and in the solid stateby X-ray diffraction. The E-ethenyl group gives rise to an openconformation and the Z-conformer to a folded structure with anintramolecular hydrogen bond closing a nine-membered pseudocycle.     

Synthesis and conformational analysis of AzAsx-containing oligopeptides

Summary For the sake of improving synthetic methods and evaluating the conformational perturbation induced by the substitution of AzAsx for the Asx residue in the cognate dipeptide R-CO-Asx-Pro-NHR, we prepared the AzAsx-dipeptide sequence by making use of the crystalline triphosgene. This reagent allows, in situ and under very mild experimental conditions, both the carbonylation and the activation of the properly substituted and N-protected hydrazine before coupling with the proline partner. With regard to conformational behaviour, the azadipeptide sequence displays a -fold, unlike the cognate dipeptide which adopts an Asx-turn.     

Synthesis and structural analysis of copper(II) cysteine complexes

This report describes the synthesis and structural analysis of stable copper(II) cysteine complexes. Pale pink copper(II) cysteine complexes were synthesized in mole ratios of 1:2, 1:4, and 1:6 of copper(II):cysteine in ethanol. Infrared spectroscopy and X-ray absorption spectroscopy confirmed that copper(II) binding occurred via the thiol ligand of cysteine. XANES analysis showed that the oxidation state of copper remained as copper(II) and the local atomic geometry was similar in all of the cysteine complexes. The EXAFS data indicate that the copper(II) cysteine complexes are forming ring type structures with sulfur ligands from the cysteines acting as bridging ligands. X-ray diffraction revealed that the copper(II) cysteine complexes formed monoclinic cells with maximum crystallinity found in the 1:4 copper(II):cysteine complex.     

Synthesis and spectroscopic characterization of protected N-phosphonomethylglycine dipeptides.

A series of terminally blocked dipeptides containing C-terminal N-phosphonomethylglycine (glyphosate, an extremely effective non-selective post-emergence herbicide) have been synthesized by a solution method. The presence of their two conformers, cis (syn) and trans (anti), was shown in solutions by NMR spectroscopy. Molecular structures of the peptides were also determined in the solid state by X-ray diffraction. The attempts for the selective and total removal of the groups protecting amino, carboxylic and phosphonate functions were in many cases unsuccessful due to the formation of cyclic structures and breakage of the phosphorus-to-carbon bond.     

Crystallization and preliminary structural studies of the ncd motor domain

The motor domain of the kinesin homolog ncd has been crystallized in the presence of MgATP by the vapor diffusion method using polyethylene glycol as the precipitant. The crystals belong to the orthorhombic space group I222 with unit cell dimensions a = 127.1 Å, b = 122.3 Å, c = 68.0 Å, and there is one ncd molecule per asymmetric unit. The crystals diffract X-ray to at least 2.3 Å and are appropriate for high-resolution structure determination. © 1995 Wiley-Liss, Inc.     

Synthesis of peptides containing oxo amino acids and their crystallographic analysis

An isolated uncharged hydrogen bond acceptor such as the carbonyl functionality of an aldehyde or a keto group is absent in natural amino acids. Although glutamine and asparagine are known to hydrogen bond through the amide carbonyl group in their side chains, they also possess the amide ? NH₂ group, which can act as a hydrogen bond donor. This makes the structural study of peptides containing an oxo residue, with an isolated carbonyl group in the side chain, interesting. Here, we report the synthesis of δ‐ and ε‐oxo amino acids and their incorporation into oligopeptides as the N‐terminal residue. The resultant oxo peptides were extensively studied using X‐ray crystallography to understand the interactions offered by the oxo group in peptide crystals. We find that the oxo groups are capable of providing additional hydrogen bonding opportunities to the peptides, resulting in increased intermolecular interactions in crystals. The study thus offers avenues for the utilization of oxo residues to introduce intermolecular interactions in synthetic peptides.     

α-螺旋型抗菌肽结构参数与功能活性的关系

随着耐药病原菌出现,寻求更为安全有效的新型抗菌制剂迫在眉睫。抗菌肽具有广谱抗菌活性,杀菌快,不易产生耐药性等优点,是理想的新型抗菌剂,具有广阔前景。α-螺旋型抗菌肽是抗菌肽中的一大类。本文从α-螺旋型抗菌肽螺旋度,疏水力矩,疏水性,净正电荷数等方面阐述了结构与功能关系,及构效关系在α-螺旋抗菌肽分子设计与改造中的应用。     

Isolation and sequence analysis of human bombesin-like peptides

The decapeptide form of human gastrin releasing peptide was isolated from acid extracts of liver tissue containing a metastatic human bronchial carcinoid tumor. A larger form also was isolated and partially characterized. During gel permeation chromatography the major immunoreactive peak eluted in the same region as synthetic gastrin releasing decapeptide while a second minor immunoreactive peak eluted near gastrin releasing peptide. Bombesin-like immunoreactivity (BLI) was purified by successive applications to reverse phase high pressure liquid chromatography (HPLC) columns. After four successive HPLC purifications a single peak of bombesin-like immunoreactivity was detected. Amino acid analysis, microsequence analysis and coelution with synthetic peptide indicated that the predominant form present in metastatic tumor tissue was identical to the decapeptide form of canine gastrin-releasing peptide. The less abundant form was purified by cation exchange chromatography followed by reverse phase high pressure liquid chromatography. Partial microsequence analysis of this peptide, through the first 11 residues, was Val-Pro-Leu-Pro-Ala-Gly-Gly-Gly-Thr-Val-Leu. This sequence differed from that of hog heptacosapeptide gastrin releasing peptide at positions 1,3,4 and 5 and from the canine peptide as positions 1,3,5, and 7.     

Novel structural class of four disulfide-bridged peptides from Tityus serrulatus venom

A new structural class of short peptides folded by four disulfide-bridges was found in the venom of the Brazilian scorpion Tityus serrulatus. Peptides were put on evidence independently by means of two different approaches of structurally guided prospection. First, a cDNA sequence was obtained using a degenerate primer constructed according to the C-terminal sequence of kaliotoxin (KTx2), from the Androctonus australis venom. Second, MALDI-TOF mass spectrometry analyses of toxic fraction FIII from T. serrulatus venom revealed a family of molecules ranging approximately from 2900 to 3000 Da. Three new peptides were isolated and named TsPep1, TsPep2, and TsPep3. Biochemical characterization showed that they are 29 amino acids long, constrained by a new pattern of four disulfide-bridges. These results enable us to classify these new molecules as part of a novel structural class of short peptides from scorpion venoms.     

Synthesis and single crystal structural investigations on quaternary salts of tellurated alkylamine derivatives

Tellurated alkylamine derivatives , , and have been synthesized by reacting appropriate organic halides with the nucleophile 4-CH₃OC₆H₄Te⁻ or Te²⁻ generated in situ by borohydride reduction of (4-CH₃OC₆H₄Te)₂ or Te powder followed by reaction with HCl of appropriate concentration. The zwitterionic species was generated when single crystals of 2 were grown in methanol at 0 °C. Complexes 1-4 exhibit characteristic ¹H NMR spectra. The single crystal structures of 1-4 and 2a have been determined. In the crystals of 1, C-H?π distances have been found to be 3.31(7)-3.59(5) Å. In both 2 and 2a, weak Te?Cl interactions (3.54(2) -3.62(2) Å) are observed. The C-H?π distance in the crystal of 2 is 3.19(0) Å. In 2a and 3, water hydrogen bonds connect the water molecules with the end groups from different molecules. In the case of 3, Te?Cl weak interactions involving the Cl⁻ ions connect together two such chains. The geometry of Te in 1 is V shaped. In 2 and 3 it is pseudo trigonal bipyramidal, and in 2a, it is square pyramidal. However, in the latter case it becomes distorted octahedral due to weak Te?Cl secondary interactions. The geometry about Te in 4 is distorted octahedral due to weak Te?Cl interactions involving Cl⁻ ions. However, there are no intermolecular Te?Cl interactions.     

Synthesis and properties of guanidine-pyridine hybridligands and structural characterisation of their mono- and bis(chelated) cobalt complexes

The synthesis of four guanidine-pyridine hybridligands and their spectroscopic features in MeCN are described. In order to demonstrate their coordinating properties, the corresponding cobalt(II)chloride complexes have been prepared and completely characterised by means of X-ray structure analysis, UV/Vis spectroscopy and mass spectrometry. The neutral complexes {1,1,3,3-tetramethyl-2-(quinolin-8-yl)guanidine}cobalt(II)-dichloride [Co(TMGqu)Cl₂] and {N-(1,3-dimethylimidazolidin-2-yliden)pyridin-8-amine}cobalt(II)-dichloride [Co(DMEGpy)Cl₂] exhibit a tetrahedral coordination of the cobalt atom, whereas in bis[chlorobis{N-(1,3-dimethylimidazolidin-2-yliden)quinolin-8-amine}cobalt(II)]tetrachlorocobaltate [Co(DMEGqu)₂Cl]₂[CoCl₄] and chlorobis{1,1,3,3-tetramethyl-2-((pyridin-2-yl)methyl)guanidine}cobalt(II)chloride [Co(TMGpy)₂Cl]Cl, the cobalt atom is coordinated in a trigonal pyramidal environment. These trigonal pyramidal complex cations represent the first bis(chelated) guanidine cobalt complexes in which the pyridine donor resides on the apical position and the guanidine donor forms with the chlorine atom the base of the pyramid. Besides the structural characterisation, the quenching effect of the cobalt(II) ion (d⁷) on the ligand fluorescence has been studied.     

Synthesis, cardiostimulatory, and cardioinhibitory effects of selected insect peptides on Tenebrio molitor

The subject of these studies was a search for proctolin antagonists among peptides originating from insect species because the proctolin antagonists constantly pose a problem. During these studies we performed the synthesis of the following peptides: a native decapeptide from Manduca sexta Mas-MT-I and its 11 analogs with shortened sequences at the N-end as well as a growth suppressor, a pentapeptide isolated from Antheraea yamamai, Any-GS and its 10 analogs, modified at position 1 and with a shortened peptide chain.Biological effects were evaluated by the cardiotropic test on the semi-isolated heart of the insect species Tenebrio molitor. Mas-MT-I and six analogs stimulate the heartbeat frequency, especially [6-10]-Mas-MT-I, whereas the [4-10]-Mas-MT-I analog shows a strong inhibition of the heartbeat frequency, if insect. The Any-GS and the analogs [Gln(1)]- and [Gly(1)]-Any-GS also show a strong cardioinhibitory effect.     

Synthesis and receptor binding of IgG1 peptides derived from the IgG Fc region

The IgG binding Fcgamma receptors (FcgammaRs) play a key role in defence against pathogens by linking humoral and cell-mediated immune responses. Impaired expression and/or function of FcgammaR may result in the development of pathological autoimmunity. Considering the functions of FcgammaRs, they are potential target molecules for drug design to aim at developing novel anti-inflammatory and immunomodulatory therapies. Previous data mostly obtained by X-ray analysis of ligand-receptor complexes indicate the profound role of the CH2 domain in binding to various FcgammaRs. Our aim was to localize linear segments, which are able to bind and also to modulate the function of the low affinity FcgammaRs, like FcgammaRIIb and FcgammaRIIIa. To this end a set of overlapping octapeptides was prepared corresponding to the 231-298 sequence of IgG1 CH2 domain and tested for binding to human recombinant soluble FcgammaRIIb. Based on these results, a second group of peptides was synthesized and their binding properties to recombinant soluble FcgammaRIIb, as well as to FcgammaRs expressed on the cell surface, was investigated. Here we report that peptide representing the Arg(255)-Ser(267) sequence of IgG1 is implicated in the binding to FcgammaRIIb. In addition we found that peptides corresponding to the Arg(255)-Ser(267), Lys(288)-Ser(298) or Pro(230)-Val(240) when presented in a multimeric form conjugated to branched chain polypeptide in uniformly oriented copies induced the release of TNFalpha, a pro-inflammatory cytokine from MonoMac monocyte cell line. These findings indicate that these conjugated peptides are able to cluster the activating FcgammaRs, and mediate FcgammaR dependent function. Peptide Arg(255)-Ser(267) can also be considered as a lead for further functional studies.     

Synthesis of fused tricyclic peptides using a reprogrammed translation system and chemical modification

Here we report a unique method of ribosomally synthesizing fused tricyclic peptides. Flexizyme-assisted in vitro translation of a linear peptide with the N-terminal chloroacetyl group and four downstream cysteines followed by the addition of 1,3,5-tris(bromomethyl)benzene results in selective production of the fused tricyclic peptide. This technology can be used for the ribosomal synthesis of fused tricyclic peptide libraries for the in vitro selection of bioactive peptides with tricyclic topology.     

Ageing of the human corneal stroma: structural and biochemical changes

High and low angle X-ray diffraction patterns from the corneal stroma give information about the mean intermolecular spacing of the collagen molecules and the mean interfibrillar spacing of the collagen fibrils, respectively. X-ray data were collected, using a high intensity synchrotron source, from human corneas and sclera at approximately physiological hydration. The spacings were measured as a function of tissue age. Between birth and 90 years there is an increase in the cross-sectional area associated with each molecule in corneal collagen from approx. 3.04 nm² to 3.46 nm², and an increase in scleral collagen from approx. 2.65 nm² to 3.19 nm². These changes may be due to an increase in the extent of non-enzymatic cross-linking between collagen molecules over the age range. We have investigated this possibility by measuring collagen glycation using the thiobarbituric acid assay and the subsequent advanced glycation end-products (AGEs) using fluorescence emission. The results obtained have shown an age-related increase in glycation and AGEs in both tissues. We have also demonstrated a decrease in the interfibrillar spacing of corneal collagen with increasing age which may be related to changes in the proteoglycan composition of the interfibrillar matrix.     

Synthesis and biological activities of cyclic lactam peptides as substrates for non-receptors PTKs

The heptapeptide EDNEYTA, which reproduces the main autophosphorylation site of Src, has been previously shown to be a good substrate for both Src and Syk tyrosine kinases [Ruzza, P., et al., J. Pept. Sci., 2 (1996) 325]. Four lactam bridge conformationally constrained analogues of this peptide were synthesized by classical solution methods and screened for their suitability as c-Fgr and Syk tyrosine kinase substrates. The kinetic data obtained indicate that the different rings of the lactam peptides influence the capability of the peptides to act as PTK substrates. In general cyclization decreases the peptide phosphorylability, however the sequence containing the greatest lactam ring, ED(EEYTK), resulted in an especially suitable and selective substrate for Syk tyrosine kinase.     

Synthesis and biological activities of cyclic lactam peptides as substrates for non-receptors PTKs

Summary The heptapeptide EDNEYTA, which reproduces the main autophosphorylation site of Src, has been previously shown to be a good substrate for both Scc and Syk tyrosine kinases [Ruzza, P., et al., J. Pept. Sci., 2 (1996) 325]. Four lactam bridge conformationally constrained analogues of this peptide were synthesized by classical solution methods and screened for their suitability as c-Fgr and Syk tyrosine kinase substrates. The kinetic data obtained indicate that the different rings of the lactam peptides influence the capability of the peptides to act as PTK substrates. In general cyclization decreases the peptide phosphorylability, however the sequence containing the greatest lactam ring, ED(EEYTK), resulted in an especially suitable and selective substrate for Syk tyrosine kinase.     

Crystallization and preliminary X-ray crystallographic analysis of ImmE7 protein of colicin E7

The ImmE7 protein, which can bind specifically to the DNase colicin E7 and neutralize its bactericidal activity, has been purified and crystallized in two different crystal forms by vapor diffusion method. The orthorhombic crystals belong to space group I222 or I2₁2₁2₁ and have unit cell dimensions a = 75.1 Å, b = 50.5 Å, and c = 45.4 Å. The second form is monoclinic space group P2₁ with ceil dimensions a = 29.3 Å, b = 102.7 Å, c = 53.0 Å and β = 91.5°. The orthorhombic crystals diffract to 1.8 Å resolution, and are suitable for high-resolution X-ray analysis. © 1995 Wiley-Liss, Inc.     

Nanopore analysis of tethered peptides

Peptides of 12 amino acids were tethered via a terminal cysteine to mono‐, di‐, tri‐, and tetrabromomethyl‐substituted benzene to produce bundles of one to four peptide strands (CY12‐T1 to CY12‐T4, respectively). The interaction of the bundles with the α‐hemolysin pore was assessed by measuring the blockade currents (I) and times (T) at an applied potential of ? 50, ? 100, and ? 150 mV. Three types of events could be distinguished: bumping events, with small I and short T where the molecule transiently interacts with the pore before diffusing away; translocation events, where the molecule threads through the pore with large I and the value of T decreases with increasing voltage; and intercalation events, where the molecule transiently enters the pore but does not translocate with large I and the value of T increases with increasing voltage. CY12‐T1 and CY12‐T2 gave only bumping and translocation events; CY12‐T3 and CY12‐T4 also gave intercalation events, some of which were of very long duration. The results suggest that three uncoiled peptide strands cannot simultaneously thread through the α‐hemolysin pore and that proteins must completely unfold in order to translocate. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.