Consequences of Cis-amide Bond Simulation in Opioid Peptides

Summary Six analogs of leucine-enkephalin were synthesized in which a 1,5-disubstituted tetrazole ring was incorporated in order to lock selected peptide bonds in cis geometry. The obtained compounds were examined based on their biological effects in vivo and in vitro. Only one analog was completely inactive in binding assays being very weakly active in the antinociceptive test. The remaining five compounds displayed at least weak receptor affinity and in vivo activity.     

Consequences of Cis-amide Bond Simulation in Opioid Peptides

Six analogs of leucine-enkephalin were synthesized in which a 1,5-disubstituted tetrazole ring was incorporated in order to lock selected peptide bonds in cis geometry. The obtained compounds were examined based on their biological effects in vivo and in vitro. Only one analog was completely inactive in binding assays being very weakly active in the antinociceptive test. The remaining five compounds displayed at least weak receptor affinity and in vivo activity.     

A developmentally regulated disappearance of slow myosin in fast-type muscles of the mouse

Histochemistry and immunocytochemistry using an antibody to adult rat slow-type myosin demonstrated that about 10% of the fibers in the mouse extensor digitorum longus and semimembranosus muscles contain slow myosin during the first month after birth. In adult animals, these muscles have only 0-08% slow myosin-containing fibers. These results demonstrate a developmentally linked disappearance of an adult-type myosin, and show that the adult phenotype of muscle fibers is not necessarily determined before birth as previously suggested.     

NMR characterization of a pH-dependent equilibrium between two folded solution conformations of the pheromone-binding protein from Bombyx mori

NMR spectroscopic changes as a function of pH in solutions of the pheromone-binding protein of Bombyx mori (BmPBP) show that BmPBP undergoes a conformational transition between pH 4.9 and 6.0. At pH below 4.9 there is a single "acid form" (A), and a homogeneous "basic form" (B) exists at pH above 6.0. Between pH 5 and 6, BmPBP exists as a mixture of A and B in slow exchange on the NMR chemical shift time scale, with the transition midpoint at pH 5.4. The form B has a well-dispersed NMR spectrum, indicating that it represents a more structured, "closed" conformation than form A, which has a significantly narrower chemical shift dispersion. Conformational transitions of the kind observed here may explain heterogeneity reported for a variety of odorant-binding proteins, and it will be of interest to further investigate possible correlations with pH-dependent regulation of ligand binding and release in the biological function of this class of proteins.     

Solution conformation and dynamics of a fungal cell wall polysaccharide isolated from Microsporum gypseum

The conformational and dynamical features of a branched mannan isolated from a fungal cell wall have been analysed by homo and heteronuclear NMR methods, employing different magnetic fields. 1HNMR cross relaxation times have been obtained for this polysaccharide and have been interpreted qualitatively using different motional models. 13C NMR relaxation parameters (T1, T2, NOE) have also been measured and interpreted using different approximations based on the Lipari and Szabo model free approach. The analysis of the data indicate the existence of important flexibility for the different linkages of the polysaccharide. Motions in the range of 4–6 ns contribute to the relaxation of the macromolecule, although faster internal motions in the 500 ps and 100 ps timescales are also present. These time scales indicate that segmental motions as well as internal motions around the glycosidic linkages are the major sources of relaxation for this molecule at 318 K. Molecular dynamics simulations have also been performed. The obtained results also indicate that the polysaccharide possess a substantial amount of conformational freedom.     

Pescador: the PEptides in Solution ConformAtion Database: Online Resource

In recent years a large body of data has been obtained from Nuclear Magnetic Resonance and Circular Dichroism experiments on the influence of the amino acid sequence and various other parameters on the conformational state of peptides in solution. Interpreting the experimental data in terms of the conformational populations of the peptides remains a key problem, for which current solutions leave appreciable room for improvement. Considering that making this body of data available for surveys and analysis should be instrumental in tackling the problem, we undertook the development of Pescador: The `PEptides in Solution ConformAtion Database: Online Resource'. Pescador contains data from NMR and CD spectroscopy on peptides in solution as well as information on the structural parameters derived from these data. It also features specialized Web-based tools for data deposition, and means for readily accessing the stored information for analysis purposes. To illustrate the use of the database in deriving information for the conformational analysis of peptides, we show how the alpha proton -values stored in Pescador and measured by NMR for different peptides in different laboratories can be used to derive a new set of `random coil' chemical shift values. Firstly, we show these values to be very similar to those obtained experimentally for model peptides in water, and their variation with increasing Tri-Fluoro-Ethanol (TFE) concentration is similar to that reported for model peptides. We show, furthermore, that the chemical shift data in Pescador can be used to derive correction factors that take into account effects of neighboring residues. These correction factors compare favorably with those recently derived from a series of model GGXGG peptides Schwarzinger_e-valuesstoredinPescadorandmeasuredbyNMRfordifferentpeptidesindifferentlaboratoriescanbeusedtoderiveanewsetof`randomcoil'chemicalshiftvalues.Firstly,weshowthesevaluestobeverysimilartothoseobtainedexperimentallyformodelpeptidesinwater,andtheirvariationwithincreasingTri-Fluoro-Ethanol(TFE)concentrationissimilartothatreportedformodelpeptides.Weshow,furthermore,thatthechemicalshiftdatainPescadorcanbeusedtoderivecorrectionfactorsthattakeintoaccounteffectsofneighboringresidues.ThesecorrectionfactorscomparefavorablywiththoserecentlyderivedfromaseriesofmodelGGXGGpeptides Schwarzinger _etal. These encouraging results suggest that, as the quantity of NMR data on peptide deposited in Pescador increases, surveys of these data should be a valuable means of deriving key parameters for the analysis of peptide conformation.     

Conformational Studies of Tachykinin Peptides Using NMR Spectroscopy

A conformational analysis in water and DMSO of two tachykinin family peptides (scyliorhinin I (ScyI) and scyliorhinin II (ScyII)) was carried out by 1D and 2D NMR (DQF-COSY, TOCSY, HMQC, HMBC, NOESY and ROESY) and molecular dynamics calculation methods. In DMSO, two groups of conformations (major and minor) were obtained for both peptides based on the experimental data. The conformations proposed for ScyI represent a folded structure, which shows certain similarities to the structures reported for other NK-1 and NK-2 tachykinin agonists. In water ScyII displays a flexible, extended structure, whereas in DMSO the structure is more compact and, in the fragment from the centre to the C-terminus, several -turns may be present.