Hectogram-scale synthesis of [Aib8, Arg34]-GLP-1 (7–37) by liquid-phase fragment condensation

Based on small-scale synthesis (0.3 g), a 100-g scale-up synthesis of crude [Aib⁸, Arg³⁴]-glucagon-like peptide-1 (GLP-1) (7–37) was completed. The crude [Aib⁸, Arg³⁴]-GLP-1 (7–37) was purified using a dynamic axial compression column 200 (DAC-200). Approximately 61 g of [Aib⁸, Arg³⁴]-GLP-1 (7–37) with a purity of >99% was obtained through one-step reverse-phase chromatography. The purification yield was approximately 92%. The yield from the total reaction was approximately 60%. In summary, we developed an economical and environmentally friendly route to the synthesis and purification of crude [Aib⁸, Arg³⁴]-GLP-1 (7–37), laying a foundation for subsequent industrial production.     

Interaction of a phosphorylated site of muscle phosphofructokinase with the activation of the enzyme by NH4+ and K+.1

The crystal structure of the cyclic peptide disulfide

has been determined by X-ray diffraction. The peptide crystallizes in the space group P2₁2₁2₁, with a = 8.646(1), b = 18.462(2), c = 19.678(3)Å and Z = 4. The molecules adopt a highly folded compact conformation, stabilized by two intramolecular 4→ 1 hydrogen bonds between the Cys (1) and Pro (2) CO groups and the Cys (4) and methylamide NH groups, respectively. The backbone conformational angles for the peptide lie very close to those expected for a 3₁₀ helix. The S-S bridge adopts a right handed twist with a dihedral angle of 82°. The structure illustrates the role of stereochemically constrained residues, in generating novel peptide conformations.     

Cyanobacterial bioactive metabolites—A review of their chemistry and biology

Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1–3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds.Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.     

5-Membered NH...N hydrogen bonded molecular scaffold in a model dipeptide containing 3-aminophenylacetic acid: Crystal and solution conformations

Crystallographic and spectroscopic studies of a model dipeptidecontaining unusual amino acid residues establish the presence ofan intramolecular, 5-membered NH...N hydrogen bond involvingan amide NH (from 3-amino phenyl acetic acid residue) and anamide N atom from an adjacent amino acid residue in solid stateand in solution. The dipeptide also forms an infinite -sheet ribbon structure in crystals.     

Conformation of peptides constructed from achiral amino acid residues Aib and DeltaZPhe: computational study of the effect of L/D- Leu at terminal positions

Conformational studies of the peptides constructed from achiral amino acid residues Aib and Delta(Z)Phe (I) Ac-Aib-Delta(Z)Phe-NHMe (II), and Ac-(Aib-Delta(Z)Phe)(3)-NHMe; peptides III-VI having L-Leu or D-Leu at either the N- or the C-terminal position and of peptides VII-X having Leu residues in different enantiomeric combinations at both the N- and the C-terminal positions in peptide II have been studied to design the peptide with the required helical sense. Peptide II, as expected, adopts degenerate left- and right-handed helical structures. It has been shown that the peptides IV and VI having D-Leu at either the N or the C terminus can be realized in the right-handed helical structure with the phi,psi values of -20 degrees and -60 degrees for the Aib/Delta(Z)Phe residues. L-Leu and D- Leu at both the terminals in peptides VII and VIII, respectively, have hardly any effect as both the left- and the right-handed structures are found to be degenerate. Peptides III and IX can be realized in right- and left-handed helical structures, respectively, in solvents of low polarity whereas peptides V and X are predicted to be in the right-handed helical structures stabilized by carbonyl-carbonyl interactions without the formation of hydrogen bonds. The conformational states with the phi,psi values of 0 degrees and -85 degrees in peptide V are characterized by rise per residue of 2.03 A, rotation per residue of 117.5 degrees , and 3.06 residues per turn. In all peptides having Leu residue at the N terminus, the methyl moiety of the acetyl group is involved in the CH/pi interactions with the Cepsilon--Cdelta edge of the aromatic ring of Delta(Z)Phe (3) and the amino group NH of Delta(Z)Phe is involved in the NH/pi interactions with its own aromatic ring. The CH(3) groups of the Aib residues are also involved in CH/pi interactions with the i + 1th and i + 3th Delta(Z)Phe's aromatic side chains.     

The production and characterisation of trichotoxin peptaibols, by Trichoderma asperellum

Trichoderma spp. are regularly found as a constituent of the mycoflora of many soils and are noted for their antagonistic activity against bacteria and other fungi. This latter property is the basis for the widespread interest in their use in the biological control of soil-borne fungal plant pathogens. This antagonism is partly based on their ability to produce an impressive inventory of secondary metabolites. An important group of bioactive metabolites produced by Trichoderma spp. are the non-ribosomal peptides (NRPs), especially the peptaibols. A virulent antagonistic strain, T. asperellum, which had been used in biological control strategies in Malaysia and previously examined for mycolytic enzyme production, has been studied for its potential for peptaibol production. The present research demonstrated the ability of T. asperellum to produce at least two metabolites which were identified as acid trichotoxin 1704E (Ac-Aib-Gly-Aib-Leu-Aib-Gln-Aib-Aib-Aib-Ala-Ala-Aib-Pro-Leu-Aib-Iva-Glu-Vol) and neutral trichotoxin 1717A (Ac-Aib-Gly-Aib-Leu-Aib-Gln-Aib-Aib-Aib-Ala-Aib-Aib-Pro-Leu-Aib-Iva-Gln-Vol). Addition of free Aib to the culture medium enhanced the production of trichotoxins. Biological activity of these substances was investigated against Bacillus stearothermophilus. The general characteristics of peptaibols, also found in the trichotoxins, include the presence of high proportions of the uncommon amino acid Aib, the protection of the N- and C-termini by an acetyl group and reduction of the C-terminus to 2-amino alcohols, respectively, amphipathy and microheterogeneity.     

Main-chain length control of conformation, membrane activity, and antibiotic properties of lipopeptaibol sequential analogues

To investigate the effect of backbone length and amphiphilicity on the 3D structure, membrane permeability, and antibacterial properties of trichogins, a subclass of lipopeptaibols, we prepared, by the segment condensation approach in solution and chemically characterized, a set of N(alpha)-1-octanoylated -X-(GLUG)(n)-I-L- ( X=G or U where U=Aib; n=1-4) sequential peptide esters. In parallel, the 12-mer (UGGL)(3) aneurism peptide, an analogue of the 11-mer sequential peptide (n=2) with an amino acid insertion was also synthesized and studied. By FT-IR absorption technique, we clearly showed that, in CDCl(3) solution, all peptides essentially populate intramolecularly H-bonded, helical conformations. Moreover, CD spectroscopy indicates that all peptides, with the single exception of the shortest oligomer (the heptamer), adopt mixed 3(10)-/alpha-helical structures, to an extent approximately correlating with main-chain length, in MeOH solution and sodium dodecylsulfate (SDS) micelles. Significant membrane permeability properties were found only for the three longest GLUG-based peptides, with the 15-mer oligomer (n=4) resulting the most active. The lack of activity exhibited by the aneurism peptide in this experiment strongly suggests a relevant role for the sequence amphiphilicity. In addition, antibacterial activity and selectivity were highlighted and demonstrated to be dependent on peptide main-chain length and amphiphilicity, in the sense that the two shortest GLUG-based homologues are active against Gram-positive strains, whereas the two longest homologues are able to penetrate the membranes of the Gram-negative strains, and the UGGL-based aneurism peptide is inactive.     

Backbone dynamics of alamethicin bound to lipid membranes: spin-echo electron paramagnetic resonance of TOAC-spin labels

Alamethicin F50/5 is a hydrophobic peptide that is devoid of charged residues and that induces voltage-dependent ion channels in lipid membranes. The peptide backbone is likely to be involved in the ion conduction pathway. Electron spin-echo spectroscopy of alamethicin F50/5 analogs in which a selected Aib residue (at position n = 1, 8, or 16) is replaced by the TOAC amino-acid spin label was used to study torsional dynamics of the peptide backbone in association with phosphatidylcholine bilayer membranes. Rapid librational motions of limited angular amplitude were observed at each of the three TOAC sites by recording echo-detected spectra as a function of echo delay time, 2τ. Simulation of the time-resolved spectra, combined with conventional EPR measurements of the librational amplitude, shows that torsional fluctuations of the peptide backbone take place on the subnanosecond to nanosecond timescale, with little temperature dependence. Associated fluctuations in polar fields from the peptide could facilitate ion permeation.     

Antiobesity and emetic effects of a short-length peptide YY analog and its PEGylated and alkylated derivatives

Neuropeptide Y2 receptor (Y2R) agonism is an important anorectic signal and a target of antiobesity drug discovery. Recently, we synthesized a short-length Y2R agonist, PYY-1119 (4-imidazolecarbonyl-[d-Hyp²⁴,Iva²⁵,Pya(4)²⁶,Cha^27,36,γMeLeu²⁸,Lys³⁰,Aib³¹]PYY(23–36), 1) as an antiobesity drug candidate. Compound 1 induced marked body weight loss in diet-induced obese (DIO) mice; however, 1 also induced severe vomiting in dogs at a lower dose than the minimum effective dose administered to DIO mice. The rapid absorption of 1 after subcutaneous administration caused the severe vomiting. Polyethylene glycol (PEG)- and alkyl-modified derivatives of 1 were synthesized to develop Y2R agonists with improved pharmacokinetic profiles, i.e., lower maximum plasma concentration (C_max) and longer time at maximum concentration (T_max). Compounds 5 and 10, modified with 20?kDa PEG at the N-terminus and eicosanedioic acid at the Lys³⁰ side chain of 1, respectively, showed high Y2R binding affinity and induced significant body weight reduction upon once-daily administration to DIO mice. Compounds 5 and 10, with their relatively low C_max and long T_max, partially attenuated emesis in dogs compared with 1. These results indicate that optimization of pharmacokinetic properties of Y2R agonists is an effective strategy to alleviate emesis induced by Y2R agonism.     

Helical screw sense of peptide molecules: The pentapeptide system (Aib)4/L-Val[L-(αMe)Val] in the crystal state

The crystal-state preferred conformations of six N^α-blocked pentapeptide esters, each containing four helicogenic, achiral α-aminoisobutyric acid (Aib) residues followed by one chiral L -valine (L -Val) or C^α-methyl-L -valine [(αMe)Val] residue at the C-terminus, have been assessed by x-ray diffraction analysis. In all of the compounds the  (Aib)₄ sequence is folded in a regular 3₁₀-helical conformation. In the four pentapeptides characterized by the L -(αMe)Val residue two conformationally distinct molecules occur in the asymmetric unit. Conversely, only one molecule is observed in the asymmetric unit of two pentapeptides with the C-terminal L -Val residue. In the L -Val based peptides the helical screw sense of the  (Aib)₄ sequence is right-handed, whereas in the L  (αMe)Val analogues both right- and left-handed helical screw senses concomitantly occur in the two crystallographically independent molecules. © 1998 John Wiley & Sons, Inc. Biopoly 46: 433–443, 1998