ABSTRACT
We show that bimolecular reactions between species confined to the surfaces of nanoparticles can be manipulated by the nature of the linker, as well as by the curvature of the underlying particles.
Subject(s)
Enzymes, Immobilized/chemistry , Anthracenes/chemistry , Enzymes, Immobilized/metabolism , Gold/chemistry , Metal Nanoparticles/chemistry , Models, Molecular , Protein Conformation , Surface PropertiesABSTRACT
In insects numerous physiological processes are regulated by neuropeptides. Two fluorescent analogues of the amino acids tryptophan and tyrosine were synthesized and incorporated in the diuretic neuropeptide helicokinin I from the moth Heliothis zea. By fluorescence emission measurements it was shown that both fluorescent helicokinin I analogues react sensitive on the dielectricity of their microenvironment. A helicokinin I analogue containing the fluorescent tryptophan mimic beta-[6'-(N,N-dimethyl)-amino-2'-naphthoyl]alanine (Ald) was shown to bind to dodecylphosphocholine (DPC) micelles by the Ald residue. A membrane binding model for helicokinin I is proposed based on data from related mammalian and insect-neuropeptides.
Subject(s)
Fluorescent Dyes/chemistry , Insect Hormones/chemistry , Insect Proteins/chemistry , Moths/genetics , Neuropeptides/chemistry , Alanine/analogs & derivatives , Alanine/metabolism , Amino Acid Sequence , Animals , Fluorescent Dyes/metabolism , Insect Hormones/biosynthesis , Insect Hormones/genetics , Insect Proteins/biosynthesis , Insect Proteins/genetics , Models, Molecular , Neuropeptides/biosynthesis , Neuropeptides/genetics , Receptors, Peptide/genetics , Spectrometry, Fluorescence , Tryptophan/analogs & derivatives , Tryptophan/metabolism , Tyrosine/analogs & derivatives , Tyrosine/metabolismABSTRACT
Neuropeptides control essential physiological processes in insects such as water balance and muscle activity. Due to their metabolic instability and adverse physiochemical properties, insect neuropeptides are unsuited for a direct application in plant protection. As a first approximation towards the biologically active conformation, the structures of selected neuropeptides from economically important pest insects were determined by NMR spectroscopy and fluorescence measurements in a membrane-mimicking environment. A receptor binding model is suggested for the helicokinins and discussed in connection with biological activities and membrane-bound conformations of linear and cyclic analogues.
Subject(s)
Insect Proteins/chemistry , Micelles , Peptides/chemistry , Animals , Nuclear Magnetic Resonance, Biomolecular , Spectrometry, FluorescenceABSTRACT
Neuropeptides control numerous physiological processes in insects. The regulation of water balance is a crucial aspect of homeostasis in terrestrial insects and has been shown to be under endocrine control, primarily by corticotrophin releasing factor (CRF)-related peptides and kinins. For helicokinin I, a diuretic neuropeptide from the economically important insect pest Heliothis virescens, detailed structure-activity relationships have been established based on truncated structures, diverse amino acid scans and peptidomimetic analogues. The activities of selected compounds on functional expressed helicokinin receptors are compared with the results of a Malphigian tubule assay. Implications for further peptidomimetic variations are provided.
Subject(s)
Insecta/metabolism , Neuropeptides/chemistry , Neuropeptides/metabolism , Amino Acid Sequence , Animals , Insect Proteins/chemistry , Insect Proteins/metabolism , Protein Binding , Receptors, Neuropeptide/metabolism , Structure-Activity RelationshipABSTRACT
Insect neuropeptides are involved in almost all physiological processes in insects, such as diuresis, ecdysis, pheromone biosynthesis and control of muscle activity. Thus, these small peptide hormones and their receptors are promising targets for a novel generation of selective and non-neurotoxic insecticides. However, due to poor bioavailability, pharmacokinetics and short half-life the peptides themselves cannot be used as insect control agents. The past two decades have seen an increase in research into the discovery of non-peptide small molecules that function as mimics for neuropeptides. This review presents an overview on structure-activity studies, conformational analyses and peptidomimetic modifications of selected insect neuropeptides with a special potential for application in pest control.
