Beta-endorphin. Synthesis and biological activity of analogs with disulfide bridges

Two analogs of human beta-endorphin (beta-EP) which contain cystine bridges, [Cys15-Cys26,Phe27,Gly31]-beta-EP (I) and [Cys16-Cys26,Phe27,Gly31]-beta-EP (II), were synthesized by the solid-phase method. Peptides I and II were shown to contain 2-2.5 times the opiate receptor binding activity of beta-endorphin. We also synthesized two analogs with reduced alkylated cysteine residues and these peptides, [Arg9,19,24,28,29 Cys(Cam)11,26,Phe27,Gly31] and [Arg9,19,24,28,29,Cys-(Cam)12,26,Phe27,Gly31], were shown to have approximately the same opiate receptor activity as beta-endorphin.     

MALE PEACH APHID ATTRACTION IN THE FIELD BY SEX PHEROMONES1)

Abstract Field trials by sex pheromone of aphid to trap peach aphids Myzus persicae have been carried out in 1995 and in 1996. Suitable time and the effect of ratio of two components nepetalactone and nepetalactol to apply the lure have been observed.     

Probing the substrate specificity of the intracellular brain platelet-activating factor acetylhydrolase.

Platelet-activating factor acetylhydrolases (PAF-AHs) are unique PLA2s which hydrolyze the sn-2 ester linkage in PAF-like phospholipids with a marked preference for very short acyl chains, typically acetyl. The recent solution of the crystal structure of the alpha(1) catalytic subunit of isoform Ib of bovine brain intracellular PAF-AH at 1.7 A resolution paved the way for a detailed examination of the molecular basis of substrate specificity in this enzyme. The crystal structure suggests that the side chains of Thr103, Leu48 and Leu194 are involved in substrate recognition. Three single site mutants (L48A, T103S and L194A) were overexpressed and their structures were solved to 2.3 A resolution or better by X-ray diffraction methods. Enzyme kinetics showed that, compared with wild-type protein, all three mutants have higher relative activity against phospholipids with sn-2 acyl chains longer than an acetyl. However, for each of the mutants we observed an unexpected and substantial reduction in the V(max) of the reaction. These results are consistent with the model in which residues Leu48, Thr103 and Leu194 indeed contribute to substrate specificity and in addition suggest that the integrity of the specificity pocket is critical for the expression of full catalytic function, thus conferring very high substrate selectivity on the enzyme.     

INTRASPECIFIC VARIATION AND THE ROLE OF SUPERPARASITISM IN DIAPAUSE INDUCTION OF TRICHOGRAMMA EVANESCENS WEST-WOOD*

Abstract The diapause of two populations of Trichogramma evanescens Westwood (T. evanescens A and T. evanescens B), collected from different Iranian insect pests, was studied. T. evunescens A in the eggs of Corcyra cephalonica was easily induced to stable diapause with constant 8°C, 15 % and fluctuating temperature (11–23) C -11C. T. evanescens B could not be induced to diapause with the same temperatural regime and host. The experiments showed that the host of maternal generations and the ability of avoiding super-parasitism may play an important role in intraspecific variation of T. evunescens in diapause induction.