Synthesis,characterization and nociceptive screening of new VV-hemorphin-5 analogues

In the present study, some new analogues of VV-hemorphin-5, modified at position 1 and 7 by the non-proteinogenic and/or natural amino acids followed the structures Xxx-Val-Val-Tyr-Pro-Trp-Thr-Gln-NH₂ and Val-Val-Tyr-Pro-Trp-Thr-Yyy-NH₂, where Xxx is Ile or Aib and Yyy is Lys/Orn/Dap/Dab were synthesized to investigate their potential antinociceptive activities. We report also the redox potentials and the acid/base properties as pKa values of these peptide analogues which were compared toward electrochemical behaviour of tryptophan containing peptides. All analogues showed a short lasting initial antinociceptive effect, however H2 hemorphin analogue is characterized with prolong and strong antinociceptive effect, while the other peptide analogues exerted more variable effects on the visceral nociception depending on the dose or time after the intracerebral injection.     

Design and synthesis of plant cyclopeptide Astin C analogues and investigation of their immunosuppressive activity

To further investigate on the structure-activity relationships of immunosuppressive Astin C, seventeen analogues 1–17 were designed and synthetized via amino acid substitution strategy by the solid-phase peptide synthesis method for the first time. In comparison with Astin C (IC₅₀?=?12.6?±?3.3?μM), only compounds 2 (IC₅₀?=?38.4?±?16.2?μM), 4 (IC₅₀?=?51.8?±?12.7?μM), 5 (IC₅₀?=?65.2?±?15.6?μM), and 8 (IC₅₀?=?61.8?±?12.4?μM) exhibited immunosuppressive activity in the Lymph node cells of mice. These results showed that the Astin C analogues containing _D-amino acid residues, hydrophobic long-chain alkyl substituents, and aryl substituents performed better than those carrying hydrophilic amino acid residues and short-chain alkyl substituents. Moreover compounds 15, 16, and 17 had no immunosuppressive activity, which suggested that cis-3,4-dichlorinated proline played an important role in the immunosuppressive activity of Astin C.     

Thrombin binding aptamer analogues containing inversion of polarity sites endowed with antiproliferative and anti-motility properties against Calu-6 cells

Background

Although the thrombin binding aptamer (TBA) is endowed with both anticoagulant and antiproliferative properties, it is possible to reduce the first and enhance the second one by suitable chemical modifications.

In Vitro Anti-hepatitis B Virus Activity of 2',3'-Dideoxyguanosine

2',3'-dideoxyguanosine(DoG) has been demonstrated to inhibit duck hepatitis B virus(DHBV) replication in vivo in a duck model of HBV infection. In the current study, the in vitro antiviral effects of DoG on human and animal hepadnaviruses were investigated. Our results showed that DoG effectively inhibited HBV, DHBV, and woodchuck hepatitis virus(WHV)replication in hepatocyte-derived cells in a dose-dependent manner, with 50% effective concentrations(EC50) of 0.3 ± 0.05, 6.82 ± 0.25, and 23.0 ± 1.5 lmol/L, respectively. Similar to other hepadnaviral DNA polymerase inhibitors,DoG did not alter the levels of intracellular viral RNA but induced the accumulation of a less-than-full-length viral RNA species, which was recently demonstrated to be generated by RNase H cleavage of pgRNA. Furthermore, using a transient transfection assay, DoG showed similar antiviral activity against HBV wild-type, 3TC-resistant rtA181 V, and adefovirresistant rtN236T mutants. Our results suggest that DoG has potential as a nucleoside analogue drug with anti-HBV activity.     

Melatonin receptor pharmacology: toward subtype specificity

The recent cloning of three distinct melatonin receptor subtypes (Mel_1a, Mel_1b and Mel_1c) which are part of a new family of G-protein coupled receptors, and probably mediate the physiological actions of the hormone, has spurred interest in the design of analogues with subtype selectivity. The 5-methoxyl and N-acetyl groups of melatonin are important for binding to and activation of the receptor. The indole nucleus serves to hold these two groups at the correct distance from one another and allows them to adopt the required orientation for interaction with the receptor binding pocket. We have investigated the subtype selectivity of a number of analogues of melatonin in which the structure has systematically been modified in order to probe the similarities and differences in the interaction of ligand and receptor subtype. At all three subtypes 5-methoxyl and N-acetyl groups of melatonin are important for high affinity binding. However, replacing the 5-methoxyl group (eg with 5-H, 5-OH, 5-Me or 5-BzO) reduces affinity much less at the Mel_1b receptor subtype than at either Mel_1a or Mel_1c cloned subtypes. This suggests differences between the Mel_1b and Mel _1a/1c subtypes in the size and shape of the binding pocket or in the manner in which melatonin interacts with the receptor at this position. Further studies have revealed that analogues with longer N-acyl carbon chains behave similarly at each subtype. These observations suggest that the ‘pocket’ into which the N-acetyl group fits is very similar for each subtype. Substitutions at the 2-position on the indole ring improved affinity at each receptor subtype but did not give selective analogues. The systematic ‘mapping’ of the requirements for binding at each receptor subtype should allow the design of more selective agonists and antagonists, which will be valuable tools for the characterization and classification of functional melatonin receptors.     

Control of plant disease by perturbation of fungal polyamine metabolism

The diamine putrescine and the polyamines spermidine and spermine are ubiquitous in nature and are essential for cell proliferation. Since polyamine biosynthesis in plants can start from either ornithine or arginine, while fungal polyamine biosynthesis appears to utilise only the ornithine route, it was suggested that specific inhibition of fungal polyamine biosynthesis should be lethal. Indeed, inhibitors of polyamine biosynthesis, e.g. the ornithine decarboxylase inhibitor α-difluoromethylornithine, have been shown to inhibit fungal growth in vitro and to control fungal infections on a variety of plants under glasshouse and field conditions. It is now known that polyamine analogues can perturb polyamine metabolism leading to powerful antiproliferative effects in cancer cells. This paper reviews the results of a research programme focused on the synthesis and evaluation of putrescine analogues as novel fungicides. A number of aliphatic, alicyclic and cyclic diamines have been shown to possess considerable fungicidal activity, but although many of these compounds perturb polyamine metabolism in fungal cells, such changes are not considered sufficient to account for the observed antifungal effects. More recent work on spermidine analogues is also described.     

Synthesis and applications of cyclopeptides and depsipeptides

Summary A solid phase protocol has been devised for the synthesis of linear precursors to cyclic depsipeptide analogues of dolastatin D.t-Butyldimethylsilyl groups were used for hydroxy group protection, with deprotection being carried out byt-butyl ammonium fluoride. HATU and PyBrop were successful in coupling highly hindered residues and in depside bond formation. Cyclic peptide analogues, cyclo[Arg-Gly-Asp-d-Phe-Lys(or Tyr)] have been synthesised and modified for use as carrier molecules for the transport of radio isotopes (¹¹¹In and¹²⁵I) into blood platelets as prototypes for medical imaging.     

油菜素内酯不敏感型的拟南芥突变型筛选

自1979年Grove等首次从油菜（＆．wM－。。WL·）花粉中分离出油菜素内酯（brassinolide,BR）以来,人们已在该激素的生理反应和对植物生长发育等方面进行了许多研究（Kalinich等1985,Mandava1988,吴登如和赵硫橘1993）。但由于这类激素在10－'mol／L浓度水平就能诱导大豆、水稻等多种植物细胞的生长和分裂（Sasse1991）,而且在植物体内含量极低,因此用传统的方法研究它的作用方式非常困难。目前,利用激素突变体来研究激素代谢及其分子机制已有不少成功的例子,如生长素（Keily和Bradford1986,Lincoln等1990）、赤霉素（Singh…     

Potent trypsin-resistant hGH-RH analogues.

A series of analogues of hGH-RH-(1-29)-NH2 designed to have metabolic stability has been synthesized. Standard Boc-SPPS was employed, modified to permit the guanidinylation of amino side-chains after chain assembly but before release from the resin. [Dat1, Har(11, 12, 20, 21, 29), Ala15, Nle27, Asp28]-, [Dat1, Har(11, 20, 29), Orn12, Ala15, Nle27, Asp28]-, and [Dat1, Gap(11,12, 21, 29), Ala15, Har20, Nle27, Asp28]-hGH-RH-(1-29)-NH2 were completely resistant to trypsin and about 50 times as potent as hGH-RH-(1-29)-NH2 itself when injected subcutaneously in rats. These peptides are candidates for clinical application in the therapy of GH deficiency.     

Analogues of a potent oxytocin antagonist with truncated C-terminus or shorter amino acid side chain of the basic amino acid at position 8.

Twelve analogues were synthesized, their structure derived from modifications of [(S)Pmp1, D-Trp2, Pen6, Arg8]oxytocin, PA, in which (S)Pmp = beta,beta-(3-thiapentamethylene-beta-mercaptopropionic acid). PA is a potent antagonist of the uterotonic effect of oxytocin in the rat (uterotonic test in vitro, pA2 = 8.86) and in the baboon. Truncated analogues of PA from the C-terminus were systematically prepared ending in either the free acid or the amide, i.e. PA1-9 acid, PA1-8 acid, PA1-7 acid, PA1-6 acid, PA1-8 amide, PA1-7 amide and PA1-6 amide. PA1-8 amide was roughly as potent as PA in the rat uterotonic assay in vitro, and the shorter amides were only somewhat weaker antagonists. All four acid analogues were weaker antagonists than PA but still maintained rather high antagonistic potency. These findings suggest that, if these truncated acids form as metabolites in vivo, they may contribute to the overall biological effect of PA and their contribution should be taken into account. Furthermore, using these analogues, the radioimmunoassay measurements of PA may be standardized, as they may cross react with PA antibodies and interfere with the determination. In addition, five analogues were made by substituting Arg8 of PA with Lys, Orn8, Dab8, Dap8 and Cit8. All of these analogues maintained high potency as OTAs in the uterotonic assay, although their activity was only about 1.5-3 times lower than PA. The most potent analogue in the uterotonic assay, [Dap8]PA, pA2 = 8.53, had weak pressor activity (pA2 = 6.90) and no antidiuretic effect. The pressor activity was lower for all tested acids, and for PA1-6 acid it was even below the detection limit. Additionally, PA1-9 acid, PA1-7 acid and PA1-6 acid showed no antidiuretic activity. Hence, the PA1-6 acid is a potent OTA with pA2 = 8.27 and no measurable effect in the pressor or antidiuretic tests and thus it is a pure oxytocin antagonist. This fact makes it an attractive candidate for further studies on inhibition of OT biological effects and on preterm labour.